Bram Vanschoenwinkel | KU Leuven (original) (raw)

Papers by Bram Vanschoenwinkel

PloS one, 2013

The relative importance of deterministic and stochastic processes driving patterns of human settl... more The relative importance of deterministic and stochastic processes driving patterns of human settlement remains controversial. A main reason for this is that disentangling the drivers of distributions and geographic clustering at different spatial scales is not straightforward and powerful analytical toolboxes able to deal with this type of data are largely deficient. Here we use a multivariate statistical framework originally developed in community ecology, to infer the relative importance of spatial and environmental drivers of human settlement. Using Moran's eigenvector maps and a dataset of spatial variation in a set of relevant environmental variables we applied a variation partitioning procedure based on redundancy analysis models to assess the relative importance of spatial and environmental processes explaining settlement patterns. We applied this method on an archaeological dataset covering a 15 km 2 area in SW Turkey spanning a time period of 8000 years from the Late Neolithic/Early Chalcolithic up to the Byzantine period. Variation partitioning revealed both significant unique and commonly explained effects of environmental and spatial variables. Land cover and water availability were the dominant environmental determinants of human settlement throughout the study period, supporting the theory of the presence of farming communities. Spatial clustering was mainly restricted to small spatial scales. Significant spatial clustering independent of environmental gradients was also detected which can be indicative of expansion into unsuitable areas or an unexpected absence in suitable areas which could be caused by dispersal limitation. Integrating historic settlement patterns as additional predictor variables resulted in more explained variation reflecting temporal autocorrelation in settlement locations.

Oikos, 2007

Explaining the variance of local communities in a spatial-environmental matrix is one of the core... more Explaining the variance of local communities in a spatial-environmental matrix is one of the core interests of ecology today. Recent progress in metacommunity theory has made a substantial contribution to this field, however good empirical data in support of available theories are still relatively scarce. In this study we sampled a cluster of 36 temporary rock pools four times during one season to assess invertebrate metacommunity structure and dynamics and to search for steering processes and variables. Both Mantel tests and redundancy models indicate that local abiotic factors were dominant over spatial factors in explaining community structure and both were acting independently. Spatial variables were only important for passive dispersers and significantly explained 11% of variation in this community component. Pools connected by temporary overflows hosted more similar communities of passive dispersers than unconnected ones while community dissimilarity significantly increased with inter-pool distance. A negative curvilinear relation was discovered between taxon richness and isolation in passive dispersers, providing some support for existing theoretical models of Mouquet and Loreau. Of different metacommunity perspectives, a combination of species sorting and mass effects best explains the observed patterns. Additionally, priority effects and monopolization may buffer against the homogenising effects of dispersal and contribute to the distinctness of isolated communities. This is one of the first studies to present evidence for spatial patterns in aquatic communities on such a small spatial scale (a rock ledge of 99000 m 2 ). Bridging the gap between theory and observed patterns in natural systems is one of the main challenges for future metacommunity research. Small aquatic habitats such as pitcher plants and freshwater rock pools may well have an important role to play as model systems to study ecological processes in a natural spatially explicit environment.

Oikos, 2007

Despite an upsurge of interest in spatial interactions between communities and in the impact of d... more Despite an upsurge of interest in spatial interactions between communities and in the impact of dispersal on ecological and evolutionary processes, dispersal patterns and dynamics in natural metacommunities remain poorly understood. Although passive aerial dispersal of freshwater invertebrates is generally accepted, the frequency and relative importance of wind as a vector is still subject of considerable debate. We assessed the importance of wind dispersal in an invertebrate metacommunity in a cluster of 36 temporary rock pools on an isolated mountaintop in South Africa. Wind dispersal was quantified every four days using nine windsocks (about 1.5 m above rock base), placed in the field during one month. Distance to the nearest pool varied from 2 up to 16 m. Wind direction and speed were monitored for the entire period. About 850 propagules (mostly resting eggs) of 17 taxa were captured. The presence of water in the pools (level of exposure of the dormant propagule bank) and the dominant wind direction were the key factors affecting the yield. Wind speed was much less important.

PLOS One, 2011

Recent findings suggest a convergence of time scales between ecological and evolutionary processe... more Recent findings suggest a convergence of time scales between ecological and evolutionary processes which is usually explained in terms of rapid micro evolution resulting in evolution on ecological time scales. A similar convergence, however, can also emerge when slow ecological processes take place on evolutionary time scales. A good example of such a slow ecological process is the colonization of remote aquatic habitats by passively dispersed zooplankton. Using variation at the protein coding mitochondrial COI gene, we investigated the balance between mutation and migration as drivers of genetic diversity in two Branchipodopsis fairy shrimp species (Crustacea, Anostraca) endemic to remote temporary rock pool clusters at the summit of isolated mountaintops in central South Africa. We showed that both species colonized the region almost simultaneously c. 0.8 My ago, but exhibit contrasting patterns of regional genetic diversity and demographic history. The haplotype network of the common B. cf. wolfi showed clear evidence of 11 long distance dispersal events (up to 140 km) with five haplotypes that are shared among distant inselbergs, as well as some more spatially isolated derivates. Similar patterns were not observed for B. drakensbergensis presumably since this rarer species experienced a genetic bottleneck. We conclude that the observed genetic patterns reflect rare historic colonization events rather than frequent ongoing gene flow. Moreover, the high regional haplotype diversity combined with a high degree of haplotype endemicity indicates that evolutionary-(mutation) and ecological (migration) processes in this system operate on similar time scales. Citation: Vanschoenwinkel B, Mergeay J, Pinceel T, Waterkeyn A, Vandewaerde H, et al. (2011) Long Distance Dispersal of Zooplankton Endemic to Isolated Mountaintops -an Example of an Ecological Process Operating on an Evolutionary Time Scale. PLoS ONE 6(11): e26730.

PloS one, 2012

Tadpole shrimp (Crustacea, Notostraca) are iconic inhabitants of temporary aquatic habitats world... more Tadpole shrimp (Crustacea, Notostraca) are iconic inhabitants of temporary aquatic habitats worldwide. Often cited as prime examples of evolutionary stasis, surviving representatives closely resemble fossils older than 200 mya, suggestive of an ancient origin. Despite significant interest in the group as 'living fossils' the taxonomy of surviving taxa is still under debate and both the phylogenetic relationships among different lineages and the timing of diversification remain unclear. We constructed a molecular phylogeny of the Notostraca using model based phylogenetic methods. Our analyses supported the monophyly of the two genera Triops and Lepidurus, although for Triops support was weak. Results also revealed high levels of cryptic diversity as well as a peculiar biogeographic link between Australia and North America presumably mediated by historic long distance dispersal. We concluded that, although some present day tadpole shrimp species closely resemble fossil specimens as old as 250 mya, no molecular support was found for an ancient (pre) Mesozoic radiation. Instead, living tadpole shrimp are most likely the result of a relatively recent radiation in the Cenozoic era and close resemblances between recent and fossil taxa are probably the result of the highly conserved general morphology in this group and of homoplasy. Citation: Vanschoenwinkel B, Pinceel T, Vanhove MPM, Denis C, Jocque M, et al. (2012) Toward a Global Phylogeny of the ''Living Fossil'' Crustacean Order of the Notostraca. PLoS ONE 7(4): e34998.

…, 2008

The extent and frequency of passive overland dispersal of freshwater invertebrates as well as the... more The extent and frequency of passive overland dispersal of freshwater invertebrates as well as the relative importance of different dispersal vectors is not well documented. Although anecdotal evidence subscribing the feasibility of individual vectors in various aquatic systems is abundant, dispersal rates have rarely been quantified for different vectors in one study system. Earlier studies also usually investigated dispersal potential rather than actual dispersal rates. In this study we have estimated passive dispersal rates of invertebrate propagules within a cluster of temporary rock pools via water, wind and amphibians in a direct way. Overflows after heavy rains mediated dispersal of a large number of propagules through eroded channels between pools, which were collected in overflow traps. Taking into account model based predictions of overflow frequency, this corresponds with average dispersal rates of 4088 propagules/channel yr (1 . Wind dispersal rates as measured by numbers of propagules collected on sticky traps mounted between pool basins were very high (average dispersal rate: 649 propagules m (2 in one month) and were positively related to the proximity of source populations. Finally, invertebrate propagules were also isolated from the faeces of African clawed frogs Xenopus laevis caught from the pools (on average 368 propagules/frog).

Aquatic Ecology, 2010

In temporary aquatic habitats, permanence and the severe disturbance associated with desiccation ... more In temporary aquatic habitats, permanence and the severe disturbance associated with desiccation are strong selective agents expected to lead to differentiation in life history strategies in populations experiencing different disturbance regimes. Besides optimal timing of hatching of dormant life stages, maturation and reproduction, pool inhabitants also benefit from the acquisition of reliable cues for the quality of the ambient environment. We investigated whether hatching patterns, life history characteristics and egg bank size of Branchipodopsis fairy shrimp (Branchiopoda, Anostraca) inhabiting a cluster of temporary rock pools in South Africa reflect variation in habitat stability and hatching cues. Long-term hydrological variation was used to select pools along a gradient of habitat stability. Initial conductivity was a good indicator for the length of inundations. No hatching occurred under elevated conductivities, which may present a mechanism to avoid abortive hatching. Egg bank size was unaffected by habitat size or habitat stability but instead was related to cover by a protective sheet of dry aquatic vegetation, which presumably counteracts egg bank erosion by wind when pools are dry. Life history but not hatching phenology reflected some aspects of habitat stability. Fairy shrimp populations in ephemeral pools started reproduction earlier than populations in more stable habitats. Additional common garden or transplant experiments, however, will be required to assess the relative importance of environmental and genetic components in explaining the observed variation and acquire more insight into the trade-offs that lie at the base of the evolution of life history strategies along the pond permanence gradient.

Marine and freshwater …, 2008

Het onderzoek voorgesteld in dit proefschrift werd gefinancierd met een specialisatiebeurs van he... more Het onderzoek voorgesteld in dit proefschrift werd gefinancierd met een specialisatiebeurs van het Instituut voor de Aanmoediging van Innovatie door Wetenschap en Technologie in Vlaanderen (IWT-Vlaanderen). Biodiversity and structure of invertebrate communities of temporary pools along a hydroperiod gradient Biodiversiteit en structuur van invertebratengemeenschappen in tijdelijke poelen overheen een hydroperiodegradiënt Promotoren: Prof. dr. L. Brendonck Prof. dr. L. De Meester Prof. dr. R. Stoks Proefschrift voorgedragen tot het behalen van het doctoraat in de wetenschappen, 2009 Door: Liesbet Boven

Hydrobiologia, 2009

Current evidence suggests regular overland transport of different freshwater invertebrates by win... more Current evidence suggests regular overland transport of different freshwater invertebrates by wind, mainly over short distances. Yet, very little is known about the mechanism and scale of this process or about differences in wind dispersal dynamics and capacities among taxa and propagule types. We investigated wind dispersal of freshwater invertebrates in a cluster of temporary rock pools (spatial scale: 9,000 m 2 ) in South Africa. Dispersing propagules and propagule bank fragments (i.e. aggregates of sediments and propagules) were intercepted during 1 month using a combination of windsocks (1.5 m above ground level) and sticky traps (ground level). The potential movement of propagule bank fragments (i.e. aggregates of propagules and sediments) was also simulated by tracking inter-pool movements of differently sized artificial substrate fragments similar to dry propagule bank fragments. We detected differences in the composition of dispersing communities intercepted at different altitudes (ground level and at 1.5 m). Comparison of dispersal distance distributions also revealed significant differences among taxa. Overall, larger propagule types (e.g. adult ostracods and oribatid mites) dominantly travelled near ground level while small resting eggs and cryptobiotic life stages of copepods were most frequently collected at higher altitudes (1.5 m) and dispersed over the longest distances. Finally, not only dispersal of single propagules but also ground level transport of propagule bank fragments was shown to contribute to local dispersal dynamics in temporary aquatic habitats.

Wetlands, 2007

Temporary wetlands are an ecologically and economically important habitat in South Africa. They h... more Temporary wetlands are an ecologically and economically important habitat in South Africa. They harbor large branchiopods, known to be flagship species of nonpermanent aquatic habitats, and sensitive to land use changes. In this study we review the current status of large branchiopods in the Western Cape, a South African province subject to increasing agriculture and urbanization. We studied the species diversity and distribution of large branchiopods by sampling 58 temporary wetlands in an area covering about 30% of the Western Cape. Information obtained from field samples was supplemented by incubating resting egg banks from the sampled wetlands. Our data were compared with all known distribution records for large branchiopods in the target region. Based on this combined information, the International Union for the Conservation of Nature and Natural Resources (IUCN) Red List category was assessed for each species. Four of the eight large branchiopod species known to occur in the sampling area were collected. Of all wetlands sampled, 40% harbored large branchiopods. Most anostracan populations were small, and species co-occurred in only one wetland. From the entire Western Cape, 14 species have been recorded in the past. Two of these are already included in the IUCN Red List. Insufficient data are available to determine the IUCN Red Data Category of six other species. A large variation in the telsonic appendages of S. dendyi was found across the studied area. In view of possible ongoing speciation and subsequent radiation, individual populations need protection. Since little information is available, it is difficult to evaluate recent changes in the conservation status of large branchiopods. Their populations are currently very low and have probably diminished in the last few decades. More knowledge about the functioning of temporary systems is needed to manage these vulnerable habitats and conserve their threatened species.

Aquatic conservation …, 2010

1.Several human activities, such as actions for nature conservation, research and recreational ac... more 1.Several human activities, such as actions for nature conservation, research and recreational activities, are closely associated with inland aquatic habitats that are usually considered as isolated island habitats. In this study, the possibility of unintentional dispersal of aquatic invertebrates among water bodies via footwear and motor vehicles was investigated.2.Mud samples collected from boots and from the tyres and wheel cases of cars used for field work by biologists (Camargue, Southern France) were hatched under laboratory conditions and also checked for the presence of unhatched propagules. A large number of organisms hatched and invertebrate propagules from a wide range of taxa were encountered (including Artemia, freshwater large branchiopods, Cladocera, Ostracoda, Rotifera, Turbellaria, Nematoda, etc.). The results also demonstrated that different research groups tend to transport the aquatic invertebrates typical for their respective study systems.3.Human dispersal of aquatic invertebrates has been studied mainly on large continental scales, such as in the case of transoceanic transport via ballast water in ships. This study provides evidence that dispersal via footwear and motor vehicles may result in frequent dispersal of aquatic invertebrates on a local scale, and we presume also occasionally over longer distances. Given the rapid spread of invasive zooplankton species (e.g. Artemia franciscana encountered in this study), we promote caution and recommend cleaning before transport of any equipment which comes in contact with water or aquatic sediment. Copyright © 2010 John Wiley & Sons, Ltd.Several human activities, such as actions for nature conservation, research and recreational activities, are closely associated with inland aquatic habitats that are usually considered as isolated island habitats. In this study, the possibility of unintentional dispersal of aquatic invertebrates among water bodies via footwear and motor vehicles was investigated.Mud samples collected from boots and from the tyres and wheel cases of cars used for field work by biologists (Camargue, Southern France) were hatched under laboratory conditions and also checked for the presence of unhatched propagules. A large number of organisms hatched and invertebrate propagules from a wide range of taxa were encountered (including Artemia, freshwater large branchiopods, Cladocera, Ostracoda, Rotifera, Turbellaria, Nematoda, etc.). The results also demonstrated that different research groups tend to transport the aquatic invertebrates typical for their respective study systems.Human dispersal of aquatic invertebrates has been studied mainly on large continental scales, such as in the case of transoceanic transport via ballast water in ships. This study provides evidence that dispersal via footwear and motor vehicles may result in frequent dispersal of aquatic invertebrates on a local scale, and we presume also occasionally over longer distances. Given the rapid spread of invasive zooplankton species (e.g. Artemia franciscana encountered in this study), we promote caution and recommend cleaning before transport of any equipment which comes in contact with water or aquatic sediment. Copyright © 2010 John Wiley & Sons, Ltd.

Limnetica, 2010

... Luc Brendonck1,∗, Merlijn Jocque1,2, Ann Hulsmans1 and Bram Vanschoenwinkel1 ... Depending on... more ... Luc Brendonck1,∗, Merlijn Jocque1,2, Ann Hulsmans1 and Bram Vanschoenwinkel1 ... Depending on the characteristics of connecting elements (length, diameter, water flow, wind direction), weighing factors can be included to improve the connectivity matrix. ...

Freshwater …, 2009

1. Hydroregime (duration, frequency and predictability of the aquatic phase) is a key feature of ... more 1. Hydroregime (duration, frequency and predictability of the aquatic phase) is a key feature of temporary aquatic habitats that not only moulds community structure and diversity (species sorting) but also life history characteristics of the inhabitants (natural selection). However, since hydroregime is a complex multidimensional entity that cannot be estimated from short term observations, morphometric variables are commonly used as proxies for hydroregime, making it impossible to separate effects of habitat size and hydroregime on biota.2. We have used a simple hydrological model, validated with recent (average r2 = 96%) and historic water level observations (average r2 = 81%), to accurately reconstruct hydroregime based on historical rainfall and evaporation data in a cluster of 36 temporary rock pools in central South Africa.3. Using the model output, we demonstrated that both hydroregime and habitat size had unique and shared effects on temporary pool biota and that these effects depended on the dispersal modes of the taxa. Model-generated hydrological data explained more variation in community patterns than short-term observations of hydroperiod. Hydroregime was more important for passive dispersers than for active dispersers that can migrate when pools dry up. Basin morphometry was a relatively poor predictor of pool hydroregime. We concluded that simple modelling may greatly improve the resolution of studies linking hydroregime to biological variables.4. An accurate account of hydrological variation provides a firm foundation to understand community and population structure and dynamics in temporary aquatic habitats. Since many of these habitats have been destroyed or degraded in recent decades, our findings and tools may contribute to the development of reliable conservation guidelines.

Freshwater Biology, 2010

1. In the light of the recent surge of interest in small and often temporary wetlands as model sy... more 1. In the light of the recent surge of interest in small and often temporary wetlands as model systems for ecological and evolutionary research, this article reviews current knowledge on freshwater rock pools and their fauna.2. Freshwater rock pools occur all over the globe in all major biomes and depend mainly on precipitation for filling. Rock pool clusters are some of the more persistent and oldest freshwater habitats worldwide. Interactions between climate and geology (e.g. limestone, sandstone, granite) generally determine the morphology and hydrology of rock pool habitats, with hydroperiods ranging from several days up to the whole year. Pool volume is usually small, resulting in strongly fluctuating environmental conditions, low conductivity and wide variations in pH (from 4.0 to 11.0) and temperature (from freezing point to 40 °C) often with well-marked diel cycles. The highly variable environmental conditions, combined with the unpredictability of the flooding regime, require high stress tolerance of the inhabitants, with adaptations for surviving the dry phase such as the production of resistant stages and active emigration followed by recolonisation.3. About 460 aquatic animal species have been recorded from freshwater rock pools around the world. Approximately 170 of these are passive dispersers, which mainly disperse as resting stages via wind and overflow of water between pools. Successful long distance dispersal seems limited. This group is composed mainly of rock pool specialists with a high degree of endemicity. The remaining taxa can be considered active dispersers, with migration usually restricted to the adult stage. Often these taxa are broadly distributed and occur in a wide range of temporary habitats in addition to rock pools.4. The inherent characteristics of freshwater rock pools, such as their simple structure and occurrence on similar substrata all over the world, facilitate comparison of research results and promote rock pools as model systems for ecological and evolutionary research. Nevertheless, despite their potential as model systems, the unique fauna and their importance as sources of freshwater in dry countries, the ecology of freshwater rock pools remain virtually unexplored in large parts of the world.

Freshwater …, 2008

1. Many invertebrates inhabiting insular aquatic habitats rely on external agents or vectors to d... more 1. Many invertebrates inhabiting insular aquatic habitats rely on external agents or vectors to disperse. Besides water connections and wind, waterfowl and amphibians are known to mediate passive dispersal of freshwater invertebrates. However, the possibility of dispersal by terrestrial mammals has been largely overlooked.2. We investigated the potential of both external and internal zoochorous dispersal of aquatic invertebrates by the wild boar (Sus scrofa) in Mediterranean wetlands in the Camargue (France). As wild boar frequently visit wetlands for feeding and wallowing purposes, we hypothesized that they may be important passive dispersal vectors of aquatic invertebrates at a local scale. Dried mud was collected from selected ‘rubbing trees’ used by boars to dispose of parasites. Additionally, faecal pellets were collected from different locations in the wetland area.3. Seventeen freshwater invertebrate taxa including rotifers, cladocerans, copepods and ostracods hatched from sediment obtained from ‘rubbing trees’, while invertebrates hatching from dried faeces (10 taxa) were mainly rotifers. Dispersing invertebrates were collected up to 318 m from a nearest potential dispersal source. Both abundance and richness of invertebrates significantly decreased with dispersal distance.4. Our results demonstrate that large mammals such as wild boar can act as dispersal vectors of aquatic invertebrates at a local scale in the wetland area of the Camargue and suggest that external transport may be quantitatively more important than internal transport. As wallowing (mud bathing) is common in many terrestrial mammals, this mode of dispersal may be quite widespread.

Ecosystems, 2008

Ecological and evolutionary processes in temporary rock pools operate within constraints imposed ... more Ecological and evolutionary processes in temporary rock pools operate within constraints imposed by their hydrologic regimes. These shallow pools flood when seasonal rains accumulate on impermeable

Freshwater …, 2008

1. Temporary aquatic habitats often are inhabited by a unique fauna and flora and contribute sign... more 1. Temporary aquatic habitats often are inhabited by a unique fauna and flora and contribute significantly to regional diversity. Temporary wetlands around the world are disappearing rapidly. The individual and interacting impacts of factors influencing community structure and dynamics in temporary wetlands are not always well known.2. Camargue wetlands are mainly characterized by variable salinity and hydroperiod. The individual and combined impacts of these local factors, together with regional variables, on invertebrate communities remain unknown. We therefore characterized and sampled invertebrates in 30 temporary wetlands along salinity and hydroperiod gradients in the Camargue (Southern France) 3, 5 and 7 months after inundation.3. Over the three sampling occasions, a total of 17 cladoceran species and 49 macroinvertebrate taxa were identified. Hydroperiod and salinity were the most important variables explaining variation in taxonomic composition and can be considered key factors shaping the invertebrate communities in Camargue wetlands. The impact on taxon richness was significantly positive for hydroperiod but significantly negative for salinity. Regional factors had no significant effect on the structure of the studied invertebrate communities, suggesting that dispersal was not limiting and that species sorting was the most important structuring process.4. The results of this study suggest that the combined and interacting effects of salinization and hydrological modification of Mediterranean temporary wetlands (due to water management, climate change, etc.) can result in reduced diversity in large numbers of Mediterranean wetlands and induce a considerable decline in regional diversity of aquatic invertebrates.

Limnology and …, 2010

In a large-scale outdoor mesocosm experiment we studied the effects of salinity on successional p... more In a large-scale outdoor mesocosm experiment we studied the effects of salinity on successional patterns, diversity, and relative abundances of Camargue (southern France) temporary pool crustaceans. Eighty mesocosms were inoculated with a mixed resting egg bank and exposed to four different salinity treatments (0.5, 1.0, 2.5, and 5.0 g L 21 ) for a period of 7 months. Salinity significantly altered crustacean communities hatching from the resting egg bank through a number of direct and indirect effects. Salinity had a significant negative effect on the establishment of large branchiopods and copepods. Both richness and density of cladocerans, especially chydorids, were positively related to salinity, possibly due to the absence of biotic interactions with large branchiopods at the highest salinity values. We hypothesize that the salinity-mediated presence of the large branchiopod keystone group can shift the whole wetland regime from a zooplankton-rich clear-water state to a zooplankton-poor turbid state. Crustacean succession was significantly altered by salinity, by slowing down development rates, population growth or maturation rates of some species. This suggests that in addition to salinity changes, any alteration of wetland hydroperiod (e.g., through aridification or inappropriate water management) could have a synergistic effect on community structure and diversity of invertebrate communities, including some keystone species.

Fundamental and Applied Limnology, 2010

The length of the hydrocycle restrains the development of communities in temporary aquatic habita... more The length of the hydrocycle restrains the development of communities in temporary aquatic habitats. Little information is available on the importance of biotic interactions in shaping the communities in these temporary habitats. A common observation in the freshwater rock pool community assembly process is the clearly separated density peaks over time of fairy shrimp (Anostraca) and cladocerans (Anomopoda). Fairy shrimp (Anostraca), the fl agship group and dominant fi lter feeders of temporary waters hatch early after inundation. This contrasts with the occurrence pattern of coexisting cladocerans, which despite higher chances of abortive hatching occur later during the hydroperiod. To study this apparent succession pattern and test the possible presence of a biotic interaction, we set up enclosure experiments in freshwater rock pools in Western Australia and monitored cladoceran (Macrothrix hardingii) densities in the presence of variable densities or absence of fairy shrimp (Branchinella longirostris). The anomopod cladoceran populations decreased with increasing anostracan densities revealing a negative biotic interaction. The competitive dominance of anostracans most probably was mainly due to exploitation competition, with possibly elements of interference competition or predation included. Early hatching and competitive superiority may help anostracans in temporary pools to monopolize the habitat with respect to small and/or other fi lter feeding invertebrates. As such they infl uence succession dynamics and invertebrate community structure, making anostracans keystone species of temporary pools.

PloS one, 2013

The relative importance of deterministic and stochastic processes driving patterns of human settl... more The relative importance of deterministic and stochastic processes driving patterns of human settlement remains controversial. A main reason for this is that disentangling the drivers of distributions and geographic clustering at different spatial scales is not straightforward and powerful analytical toolboxes able to deal with this type of data are largely deficient. Here we use a multivariate statistical framework originally developed in community ecology, to infer the relative importance of spatial and environmental drivers of human settlement. Using Moran's eigenvector maps and a dataset of spatial variation in a set of relevant environmental variables we applied a variation partitioning procedure based on redundancy analysis models to assess the relative importance of spatial and environmental processes explaining settlement patterns. We applied this method on an archaeological dataset covering a 15 km 2 area in SW Turkey spanning a time period of 8000 years from the Late Neolithic/Early Chalcolithic up to the Byzantine period. Variation partitioning revealed both significant unique and commonly explained effects of environmental and spatial variables. Land cover and water availability were the dominant environmental determinants of human settlement throughout the study period, supporting the theory of the presence of farming communities. Spatial clustering was mainly restricted to small spatial scales. Significant spatial clustering independent of environmental gradients was also detected which can be indicative of expansion into unsuitable areas or an unexpected absence in suitable areas which could be caused by dispersal limitation. Integrating historic settlement patterns as additional predictor variables resulted in more explained variation reflecting temporal autocorrelation in settlement locations.

Oikos, 2007

Explaining the variance of local communities in a spatial-environmental matrix is one of the core... more Explaining the variance of local communities in a spatial-environmental matrix is one of the core interests of ecology today. Recent progress in metacommunity theory has made a substantial contribution to this field, however good empirical data in support of available theories are still relatively scarce. In this study we sampled a cluster of 36 temporary rock pools four times during one season to assess invertebrate metacommunity structure and dynamics and to search for steering processes and variables. Both Mantel tests and redundancy models indicate that local abiotic factors were dominant over spatial factors in explaining community structure and both were acting independently. Spatial variables were only important for passive dispersers and significantly explained 11% of variation in this community component. Pools connected by temporary overflows hosted more similar communities of passive dispersers than unconnected ones while community dissimilarity significantly increased with inter-pool distance. A negative curvilinear relation was discovered between taxon richness and isolation in passive dispersers, providing some support for existing theoretical models of Mouquet and Loreau. Of different metacommunity perspectives, a combination of species sorting and mass effects best explains the observed patterns. Additionally, priority effects and monopolization may buffer against the homogenising effects of dispersal and contribute to the distinctness of isolated communities. This is one of the first studies to present evidence for spatial patterns in aquatic communities on such a small spatial scale (a rock ledge of 99000 m 2 ). Bridging the gap between theory and observed patterns in natural systems is one of the main challenges for future metacommunity research. Small aquatic habitats such as pitcher plants and freshwater rock pools may well have an important role to play as model systems to study ecological processes in a natural spatially explicit environment.

Oikos, 2007

Despite an upsurge of interest in spatial interactions between communities and in the impact of d... more Despite an upsurge of interest in spatial interactions between communities and in the impact of dispersal on ecological and evolutionary processes, dispersal patterns and dynamics in natural metacommunities remain poorly understood. Although passive aerial dispersal of freshwater invertebrates is generally accepted, the frequency and relative importance of wind as a vector is still subject of considerable debate. We assessed the importance of wind dispersal in an invertebrate metacommunity in a cluster of 36 temporary rock pools on an isolated mountaintop in South Africa. Wind dispersal was quantified every four days using nine windsocks (about 1.5 m above rock base), placed in the field during one month. Distance to the nearest pool varied from 2 up to 16 m. Wind direction and speed were monitored for the entire period. About 850 propagules (mostly resting eggs) of 17 taxa were captured. The presence of water in the pools (level of exposure of the dormant propagule bank) and the dominant wind direction were the key factors affecting the yield. Wind speed was much less important.

PLOS One, 2011

Recent findings suggest a convergence of time scales between ecological and evolutionary processe... more Recent findings suggest a convergence of time scales between ecological and evolutionary processes which is usually explained in terms of rapid micro evolution resulting in evolution on ecological time scales. A similar convergence, however, can also emerge when slow ecological processes take place on evolutionary time scales. A good example of such a slow ecological process is the colonization of remote aquatic habitats by passively dispersed zooplankton. Using variation at the protein coding mitochondrial COI gene, we investigated the balance between mutation and migration as drivers of genetic diversity in two Branchipodopsis fairy shrimp species (Crustacea, Anostraca) endemic to remote temporary rock pool clusters at the summit of isolated mountaintops in central South Africa. We showed that both species colonized the region almost simultaneously c. 0.8 My ago, but exhibit contrasting patterns of regional genetic diversity and demographic history. The haplotype network of the common B. cf. wolfi showed clear evidence of 11 long distance dispersal events (up to 140 km) with five haplotypes that are shared among distant inselbergs, as well as some more spatially isolated derivates. Similar patterns were not observed for B. drakensbergensis presumably since this rarer species experienced a genetic bottleneck. We conclude that the observed genetic patterns reflect rare historic colonization events rather than frequent ongoing gene flow. Moreover, the high regional haplotype diversity combined with a high degree of haplotype endemicity indicates that evolutionary-(mutation) and ecological (migration) processes in this system operate on similar time scales. Citation: Vanschoenwinkel B, Mergeay J, Pinceel T, Waterkeyn A, Vandewaerde H, et al. (2011) Long Distance Dispersal of Zooplankton Endemic to Isolated Mountaintops -an Example of an Ecological Process Operating on an Evolutionary Time Scale. PLoS ONE 6(11): e26730.

PloS one, 2012

Tadpole shrimp (Crustacea, Notostraca) are iconic inhabitants of temporary aquatic habitats world... more Tadpole shrimp (Crustacea, Notostraca) are iconic inhabitants of temporary aquatic habitats worldwide. Often cited as prime examples of evolutionary stasis, surviving representatives closely resemble fossils older than 200 mya, suggestive of an ancient origin. Despite significant interest in the group as 'living fossils' the taxonomy of surviving taxa is still under debate and both the phylogenetic relationships among different lineages and the timing of diversification remain unclear. We constructed a molecular phylogeny of the Notostraca using model based phylogenetic methods. Our analyses supported the monophyly of the two genera Triops and Lepidurus, although for Triops support was weak. Results also revealed high levels of cryptic diversity as well as a peculiar biogeographic link between Australia and North America presumably mediated by historic long distance dispersal. We concluded that, although some present day tadpole shrimp species closely resemble fossil specimens as old as 250 mya, no molecular support was found for an ancient (pre) Mesozoic radiation. Instead, living tadpole shrimp are most likely the result of a relatively recent radiation in the Cenozoic era and close resemblances between recent and fossil taxa are probably the result of the highly conserved general morphology in this group and of homoplasy. Citation: Vanschoenwinkel B, Pinceel T, Vanhove MPM, Denis C, Jocque M, et al. (2012) Toward a Global Phylogeny of the ''Living Fossil'' Crustacean Order of the Notostraca. PLoS ONE 7(4): e34998.

…, 2008

The extent and frequency of passive overland dispersal of freshwater invertebrates as well as the... more The extent and frequency of passive overland dispersal of freshwater invertebrates as well as the relative importance of different dispersal vectors is not well documented. Although anecdotal evidence subscribing the feasibility of individual vectors in various aquatic systems is abundant, dispersal rates have rarely been quantified for different vectors in one study system. Earlier studies also usually investigated dispersal potential rather than actual dispersal rates. In this study we have estimated passive dispersal rates of invertebrate propagules within a cluster of temporary rock pools via water, wind and amphibians in a direct way. Overflows after heavy rains mediated dispersal of a large number of propagules through eroded channels between pools, which were collected in overflow traps. Taking into account model based predictions of overflow frequency, this corresponds with average dispersal rates of 4088 propagules/channel yr (1 . Wind dispersal rates as measured by numbers of propagules collected on sticky traps mounted between pool basins were very high (average dispersal rate: 649 propagules m (2 in one month) and were positively related to the proximity of source populations. Finally, invertebrate propagules were also isolated from the faeces of African clawed frogs Xenopus laevis caught from the pools (on average 368 propagules/frog).

Aquatic Ecology, 2010

In temporary aquatic habitats, permanence and the severe disturbance associated with desiccation ... more In temporary aquatic habitats, permanence and the severe disturbance associated with desiccation are strong selective agents expected to lead to differentiation in life history strategies in populations experiencing different disturbance regimes. Besides optimal timing of hatching of dormant life stages, maturation and reproduction, pool inhabitants also benefit from the acquisition of reliable cues for the quality of the ambient environment. We investigated whether hatching patterns, life history characteristics and egg bank size of Branchipodopsis fairy shrimp (Branchiopoda, Anostraca) inhabiting a cluster of temporary rock pools in South Africa reflect variation in habitat stability and hatching cues. Long-term hydrological variation was used to select pools along a gradient of habitat stability. Initial conductivity was a good indicator for the length of inundations. No hatching occurred under elevated conductivities, which may present a mechanism to avoid abortive hatching. Egg bank size was unaffected by habitat size or habitat stability but instead was related to cover by a protective sheet of dry aquatic vegetation, which presumably counteracts egg bank erosion by wind when pools are dry. Life history but not hatching phenology reflected some aspects of habitat stability. Fairy shrimp populations in ephemeral pools started reproduction earlier than populations in more stable habitats. Additional common garden or transplant experiments, however, will be required to assess the relative importance of environmental and genetic components in explaining the observed variation and acquire more insight into the trade-offs that lie at the base of the evolution of life history strategies along the pond permanence gradient.

Marine and freshwater …, 2008

Het onderzoek voorgesteld in dit proefschrift werd gefinancierd met een specialisatiebeurs van he... more Het onderzoek voorgesteld in dit proefschrift werd gefinancierd met een specialisatiebeurs van het Instituut voor de Aanmoediging van Innovatie door Wetenschap en Technologie in Vlaanderen (IWT-Vlaanderen). Biodiversity and structure of invertebrate communities of temporary pools along a hydroperiod gradient Biodiversiteit en structuur van invertebratengemeenschappen in tijdelijke poelen overheen een hydroperiodegradiënt Promotoren: Prof. dr. L. Brendonck Prof. dr. L. De Meester Prof. dr. R. Stoks Proefschrift voorgedragen tot het behalen van het doctoraat in de wetenschappen, 2009 Door: Liesbet Boven

Hydrobiologia, 2009

Current evidence suggests regular overland transport of different freshwater invertebrates by win... more Current evidence suggests regular overland transport of different freshwater invertebrates by wind, mainly over short distances. Yet, very little is known about the mechanism and scale of this process or about differences in wind dispersal dynamics and capacities among taxa and propagule types. We investigated wind dispersal of freshwater invertebrates in a cluster of temporary rock pools (spatial scale: 9,000 m 2 ) in South Africa. Dispersing propagules and propagule bank fragments (i.e. aggregates of sediments and propagules) were intercepted during 1 month using a combination of windsocks (1.5 m above ground level) and sticky traps (ground level). The potential movement of propagule bank fragments (i.e. aggregates of propagules and sediments) was also simulated by tracking inter-pool movements of differently sized artificial substrate fragments similar to dry propagule bank fragments. We detected differences in the composition of dispersing communities intercepted at different altitudes (ground level and at 1.5 m). Comparison of dispersal distance distributions also revealed significant differences among taxa. Overall, larger propagule types (e.g. adult ostracods and oribatid mites) dominantly travelled near ground level while small resting eggs and cryptobiotic life stages of copepods were most frequently collected at higher altitudes (1.5 m) and dispersed over the longest distances. Finally, not only dispersal of single propagules but also ground level transport of propagule bank fragments was shown to contribute to local dispersal dynamics in temporary aquatic habitats.

Wetlands, 2007

Temporary wetlands are an ecologically and economically important habitat in South Africa. They h... more Temporary wetlands are an ecologically and economically important habitat in South Africa. They harbor large branchiopods, known to be flagship species of nonpermanent aquatic habitats, and sensitive to land use changes. In this study we review the current status of large branchiopods in the Western Cape, a South African province subject to increasing agriculture and urbanization. We studied the species diversity and distribution of large branchiopods by sampling 58 temporary wetlands in an area covering about 30% of the Western Cape. Information obtained from field samples was supplemented by incubating resting egg banks from the sampled wetlands. Our data were compared with all known distribution records for large branchiopods in the target region. Based on this combined information, the International Union for the Conservation of Nature and Natural Resources (IUCN) Red List category was assessed for each species. Four of the eight large branchiopod species known to occur in the sampling area were collected. Of all wetlands sampled, 40% harbored large branchiopods. Most anostracan populations were small, and species co-occurred in only one wetland. From the entire Western Cape, 14 species have been recorded in the past. Two of these are already included in the IUCN Red List. Insufficient data are available to determine the IUCN Red Data Category of six other species. A large variation in the telsonic appendages of S. dendyi was found across the studied area. In view of possible ongoing speciation and subsequent radiation, individual populations need protection. Since little information is available, it is difficult to evaluate recent changes in the conservation status of large branchiopods. Their populations are currently very low and have probably diminished in the last few decades. More knowledge about the functioning of temporary systems is needed to manage these vulnerable habitats and conserve their threatened species.

Aquatic conservation …, 2010

1.Several human activities, such as actions for nature conservation, research and recreational ac... more 1.Several human activities, such as actions for nature conservation, research and recreational activities, are closely associated with inland aquatic habitats that are usually considered as isolated island habitats. In this study, the possibility of unintentional dispersal of aquatic invertebrates among water bodies via footwear and motor vehicles was investigated.2.Mud samples collected from boots and from the tyres and wheel cases of cars used for field work by biologists (Camargue, Southern France) were hatched under laboratory conditions and also checked for the presence of unhatched propagules. A large number of organisms hatched and invertebrate propagules from a wide range of taxa were encountered (including Artemia, freshwater large branchiopods, Cladocera, Ostracoda, Rotifera, Turbellaria, Nematoda, etc.). The results also demonstrated that different research groups tend to transport the aquatic invertebrates typical for their respective study systems.3.Human dispersal of aquatic invertebrates has been studied mainly on large continental scales, such as in the case of transoceanic transport via ballast water in ships. This study provides evidence that dispersal via footwear and motor vehicles may result in frequent dispersal of aquatic invertebrates on a local scale, and we presume also occasionally over longer distances. Given the rapid spread of invasive zooplankton species (e.g. Artemia franciscana encountered in this study), we promote caution and recommend cleaning before transport of any equipment which comes in contact with water or aquatic sediment. Copyright © 2010 John Wiley & Sons, Ltd.Several human activities, such as actions for nature conservation, research and recreational activities, are closely associated with inland aquatic habitats that are usually considered as isolated island habitats. In this study, the possibility of unintentional dispersal of aquatic invertebrates among water bodies via footwear and motor vehicles was investigated.Mud samples collected from boots and from the tyres and wheel cases of cars used for field work by biologists (Camargue, Southern France) were hatched under laboratory conditions and also checked for the presence of unhatched propagules. A large number of organisms hatched and invertebrate propagules from a wide range of taxa were encountered (including Artemia, freshwater large branchiopods, Cladocera, Ostracoda, Rotifera, Turbellaria, Nematoda, etc.). The results also demonstrated that different research groups tend to transport the aquatic invertebrates typical for their respective study systems.Human dispersal of aquatic invertebrates has been studied mainly on large continental scales, such as in the case of transoceanic transport via ballast water in ships. This study provides evidence that dispersal via footwear and motor vehicles may result in frequent dispersal of aquatic invertebrates on a local scale, and we presume also occasionally over longer distances. Given the rapid spread of invasive zooplankton species (e.g. Artemia franciscana encountered in this study), we promote caution and recommend cleaning before transport of any equipment which comes in contact with water or aquatic sediment. Copyright © 2010 John Wiley & Sons, Ltd.

Limnetica, 2010

... Luc Brendonck1,∗, Merlijn Jocque1,2, Ann Hulsmans1 and Bram Vanschoenwinkel1 ... Depending on... more ... Luc Brendonck1,∗, Merlijn Jocque1,2, Ann Hulsmans1 and Bram Vanschoenwinkel1 ... Depending on the characteristics of connecting elements (length, diameter, water flow, wind direction), weighing factors can be included to improve the connectivity matrix. ...

Freshwater …, 2009

1. Hydroregime (duration, frequency and predictability of the aquatic phase) is a key feature of ... more 1. Hydroregime (duration, frequency and predictability of the aquatic phase) is a key feature of temporary aquatic habitats that not only moulds community structure and diversity (species sorting) but also life history characteristics of the inhabitants (natural selection). However, since hydroregime is a complex multidimensional entity that cannot be estimated from short term observations, morphometric variables are commonly used as proxies for hydroregime, making it impossible to separate effects of habitat size and hydroregime on biota.2. We have used a simple hydrological model, validated with recent (average r2 = 96%) and historic water level observations (average r2 = 81%), to accurately reconstruct hydroregime based on historical rainfall and evaporation data in a cluster of 36 temporary rock pools in central South Africa.3. Using the model output, we demonstrated that both hydroregime and habitat size had unique and shared effects on temporary pool biota and that these effects depended on the dispersal modes of the taxa. Model-generated hydrological data explained more variation in community patterns than short-term observations of hydroperiod. Hydroregime was more important for passive dispersers than for active dispersers that can migrate when pools dry up. Basin morphometry was a relatively poor predictor of pool hydroregime. We concluded that simple modelling may greatly improve the resolution of studies linking hydroregime to biological variables.4. An accurate account of hydrological variation provides a firm foundation to understand community and population structure and dynamics in temporary aquatic habitats. Since many of these habitats have been destroyed or degraded in recent decades, our findings and tools may contribute to the development of reliable conservation guidelines.

Freshwater Biology, 2010

1. In the light of the recent surge of interest in small and often temporary wetlands as model sy... more 1. In the light of the recent surge of interest in small and often temporary wetlands as model systems for ecological and evolutionary research, this article reviews current knowledge on freshwater rock pools and their fauna.2. Freshwater rock pools occur all over the globe in all major biomes and depend mainly on precipitation for filling. Rock pool clusters are some of the more persistent and oldest freshwater habitats worldwide. Interactions between climate and geology (e.g. limestone, sandstone, granite) generally determine the morphology and hydrology of rock pool habitats, with hydroperiods ranging from several days up to the whole year. Pool volume is usually small, resulting in strongly fluctuating environmental conditions, low conductivity and wide variations in pH (from 4.0 to 11.0) and temperature (from freezing point to 40 °C) often with well-marked diel cycles. The highly variable environmental conditions, combined with the unpredictability of the flooding regime, require high stress tolerance of the inhabitants, with adaptations for surviving the dry phase such as the production of resistant stages and active emigration followed by recolonisation.3. About 460 aquatic animal species have been recorded from freshwater rock pools around the world. Approximately 170 of these are passive dispersers, which mainly disperse as resting stages via wind and overflow of water between pools. Successful long distance dispersal seems limited. This group is composed mainly of rock pool specialists with a high degree of endemicity. The remaining taxa can be considered active dispersers, with migration usually restricted to the adult stage. Often these taxa are broadly distributed and occur in a wide range of temporary habitats in addition to rock pools.4. The inherent characteristics of freshwater rock pools, such as their simple structure and occurrence on similar substrata all over the world, facilitate comparison of research results and promote rock pools as model systems for ecological and evolutionary research. Nevertheless, despite their potential as model systems, the unique fauna and their importance as sources of freshwater in dry countries, the ecology of freshwater rock pools remain virtually unexplored in large parts of the world.

Freshwater …, 2008

1. Many invertebrates inhabiting insular aquatic habitats rely on external agents or vectors to d... more 1. Many invertebrates inhabiting insular aquatic habitats rely on external agents or vectors to disperse. Besides water connections and wind, waterfowl and amphibians are known to mediate passive dispersal of freshwater invertebrates. However, the possibility of dispersal by terrestrial mammals has been largely overlooked.2. We investigated the potential of both external and internal zoochorous dispersal of aquatic invertebrates by the wild boar (Sus scrofa) in Mediterranean wetlands in the Camargue (France). As wild boar frequently visit wetlands for feeding and wallowing purposes, we hypothesized that they may be important passive dispersal vectors of aquatic invertebrates at a local scale. Dried mud was collected from selected ‘rubbing trees’ used by boars to dispose of parasites. Additionally, faecal pellets were collected from different locations in the wetland area.3. Seventeen freshwater invertebrate taxa including rotifers, cladocerans, copepods and ostracods hatched from sediment obtained from ‘rubbing trees’, while invertebrates hatching from dried faeces (10 taxa) were mainly rotifers. Dispersing invertebrates were collected up to 318 m from a nearest potential dispersal source. Both abundance and richness of invertebrates significantly decreased with dispersal distance.4. Our results demonstrate that large mammals such as wild boar can act as dispersal vectors of aquatic invertebrates at a local scale in the wetland area of the Camargue and suggest that external transport may be quantitatively more important than internal transport. As wallowing (mud bathing) is common in many terrestrial mammals, this mode of dispersal may be quite widespread.

Ecosystems, 2008

Ecological and evolutionary processes in temporary rock pools operate within constraints imposed ... more Ecological and evolutionary processes in temporary rock pools operate within constraints imposed by their hydrologic regimes. These shallow pools flood when seasonal rains accumulate on impermeable

Freshwater …, 2008

1. Temporary aquatic habitats often are inhabited by a unique fauna and flora and contribute sign... more 1. Temporary aquatic habitats often are inhabited by a unique fauna and flora and contribute significantly to regional diversity. Temporary wetlands around the world are disappearing rapidly. The individual and interacting impacts of factors influencing community structure and dynamics in temporary wetlands are not always well known.2. Camargue wetlands are mainly characterized by variable salinity and hydroperiod. The individual and combined impacts of these local factors, together with regional variables, on invertebrate communities remain unknown. We therefore characterized and sampled invertebrates in 30 temporary wetlands along salinity and hydroperiod gradients in the Camargue (Southern France) 3, 5 and 7 months after inundation.3. Over the three sampling occasions, a total of 17 cladoceran species and 49 macroinvertebrate taxa were identified. Hydroperiod and salinity were the most important variables explaining variation in taxonomic composition and can be considered key factors shaping the invertebrate communities in Camargue wetlands. The impact on taxon richness was significantly positive for hydroperiod but significantly negative for salinity. Regional factors had no significant effect on the structure of the studied invertebrate communities, suggesting that dispersal was not limiting and that species sorting was the most important structuring process.4. The results of this study suggest that the combined and interacting effects of salinization and hydrological modification of Mediterranean temporary wetlands (due to water management, climate change, etc.) can result in reduced diversity in large numbers of Mediterranean wetlands and induce a considerable decline in regional diversity of aquatic invertebrates.

Limnology and …, 2010

In a large-scale outdoor mesocosm experiment we studied the effects of salinity on successional p... more In a large-scale outdoor mesocosm experiment we studied the effects of salinity on successional patterns, diversity, and relative abundances of Camargue (southern France) temporary pool crustaceans. Eighty mesocosms were inoculated with a mixed resting egg bank and exposed to four different salinity treatments (0.5, 1.0, 2.5, and 5.0 g L 21 ) for a period of 7 months. Salinity significantly altered crustacean communities hatching from the resting egg bank through a number of direct and indirect effects. Salinity had a significant negative effect on the establishment of large branchiopods and copepods. Both richness and density of cladocerans, especially chydorids, were positively related to salinity, possibly due to the absence of biotic interactions with large branchiopods at the highest salinity values. We hypothesize that the salinity-mediated presence of the large branchiopod keystone group can shift the whole wetland regime from a zooplankton-rich clear-water state to a zooplankton-poor turbid state. Crustacean succession was significantly altered by salinity, by slowing down development rates, population growth or maturation rates of some species. This suggests that in addition to salinity changes, any alteration of wetland hydroperiod (e.g., through aridification or inappropriate water management) could have a synergistic effect on community structure and diversity of invertebrate communities, including some keystone species.

Fundamental and Applied Limnology, 2010

The length of the hydrocycle restrains the development of communities in temporary aquatic habita... more The length of the hydrocycle restrains the development of communities in temporary aquatic habitats. Little information is available on the importance of biotic interactions in shaping the communities in these temporary habitats. A common observation in the freshwater rock pool community assembly process is the clearly separated density peaks over time of fairy shrimp (Anostraca) and cladocerans (Anomopoda). Fairy shrimp (Anostraca), the fl agship group and dominant fi lter feeders of temporary waters hatch early after inundation. This contrasts with the occurrence pattern of coexisting cladocerans, which despite higher chances of abortive hatching occur later during the hydroperiod. To study this apparent succession pattern and test the possible presence of a biotic interaction, we set up enclosure experiments in freshwater rock pools in Western Australia and monitored cladoceran (Macrothrix hardingii) densities in the presence of variable densities or absence of fairy shrimp (Branchinella longirostris). The anomopod cladoceran populations decreased with increasing anostracan densities revealing a negative biotic interaction. The competitive dominance of anostracans most probably was mainly due to exploitation competition, with possibly elements of interference competition or predation included. Early hatching and competitive superiority may help anostracans in temporary pools to monopolize the habitat with respect to small and/or other fi lter feeding invertebrates. As such they infl uence succession dynamics and invertebrate community structure, making anostracans keystone species of temporary pools.