Comparing the potential for dispersal via waterbirds of a native and an invasive brine shrimp (original) (raw)
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Marine Biology, 2007
Waterbirds are known to disperse invertebrate propagules that survive gut passage, but there is very little information about how the probability of dispersal changes at diVerent times of the annual cycle when birds move in diVerent directions, or how it is aVected by changes in diet. We studied internal transport of brine shrimp Artemia cysts by migratory waders in the Odiel saltworks in south-west Spain. Viable cysts of parthenogenetic Artemia were abundant in the faeces and regurgitated pellets of redshank Tringa totanus, pellets of spotted redshank T. erythropus, and faeces of black-tailed godwit Limosa limosa during spring and/ or autumn migrations in 2001-2002, but were not recorded during winter. Godwits did not produce pel-lets, and spotted redshank faeces were not sampled. SigniWcant correlations between the number of cysts in a pellet or faecal sample and the proportion of that sample constituted by Artemia adults suggested that most cysts were ingested while in the ovisacs of gravid females. The proportion of cysts destroyed during digestion increased when accompanied by harder food items or grit, and when fewer cysts were ingested. The median number of intact cysts was higher in redshank faeces than in their pellets, but cysts extracted from pellets were more likely to hatch. A higher proportion of redshank pellets contained Artemia cysts in spring than in autumn, but more redshank migrated through the area in autumn. SigniWcantly fewer cysts were recorded in redshank pellets in winter than in spring or autumn. Our results conWrm that there is potential for long-distance dispersal of Artemia cysts via waders during both northwards (spring) and southwards (autumn) migrations.
Diversity and Distributions, 2005
Although Darwin pioneered the study of long-distance dispersal (LDD) of aquatic invertebrates via waterbirds, it remains in its infancy as a modern discipline. A handful of recent studies have quantified internal or external transport in the field, confirming that a variety of long-distance migrants carry invertebrates both internally and externally. These studies show that variation in the morphology of vectors influences the frequency and size of propagules transported, and suggest that more invertebrate groups disperse via birds than was previously thought. Dispersal limitation has mainly been investigated for zooplankton in small experimental systems from which waterbirds were effectively excluded, and the extent of such limitation for invertebrate populations in wetlands interconnected by waterbird movements remains unclear. We expect that the spatial and temporal scales at which dispersal limitation constrains geographical ranges, species richness and genetic structure of invertebrates depends partly on the density of migratory birds using the area. Birds may have a major role in the expansion of exotic species. We propose several avenues for future research. There is a particular need for more quantitative studies of LDD by birds that will enable modellers to assess its role in maintaining invertebrate biodiversity among increasingly fragmented wetlands and in the face of climate change, as well as in the spread of invasive species.
Waterbird-mediated passive dispersal of river shrimp Athyaephyra desmaresti
Hydrobiologia, 2012
The river shrimp Athyaephyra desmaresti is a Mediterranean species which in recent years expanded its distribution, colonizing rivers of central Europe. The purpose of this study was to investigate the possibility of passive external dispersal of the river shrimp Athyaephyra desmaresti by waterfowl. We performed experiments testing shrimp desiccation survival, probability of attachment to waterfowl, and probability of successful transport. We found that in the laboratory 10% of the river shrimps can survive out of water for up to 90.1 min, but this period was reduced to 18.5 min under simulated bird flight conditions. Two different outdoor experiments simulating bird flight conditions indicated a 50% probability of successful transport on flight distances over 15 km. Our results using dead ducks show evidence that small, large or ovigerous river shrimps can attach to and be transported by ducks and that this capacity is affected by water depth. This study demonstrated that waterbird-mediated passive dispersal of river shrimps can occur and may be important for genetic flows between populations and for the colonization of new sites.
High dispersal capacity of a broad spectrum of aquatic invertebrates via waterbirds
Aquatic Sciences, 2007
Speculation about the role of waterbirds in the dispersal of aquatic invertebrates pre-dates Darwin. However, there is a critical shortage of field studies quantifying such dispersal. We quantified the viability of aquatic invertebrates in the faeces of different waterfowl species collected in the field at different times during winter. Faeces were collected from four duck species (Northern Pintail Anas acuta, Mallard A. platyrhynchos, Shoveler A. clypeata, Eurasian Teal A. crecca) and Eurasian Coot Fulica atra in November 2004 and January 2005. We also collected soil samples from resting sites as an indicator of what may be transported on birds’ feet and plumage. Faecal and soil samples were incubated using two treatments (0.4 and 4.0 mS cm-1) to quantify the potential for dispersal between aquatic habitats of different salinities. We found that viable Nematoda, Rotifera, Copepoda, Ostracoda, Insecta (Tipulidae), and Daphnia and Moina cladocerans were transported internally by birds in the wild. We also found evidence that nematodes, rotifers, ostracods, copepods, tipulids, chironomids and hemipterans can be dispersed on birds’ feet and feathers. The overall incidence of hatching from all samples was higher in January (59.4%) than in November (11.5%). With the exception of bdelloid rotifers, we found no evidence that the potential for dispersal between two habitats would be impeded by salinity in the range tested. Our data suggest that the taxonomic range of dispersed invertebrates and the frequency of their dispersal via waterfowl has previously been underestimated.
PeerJ 1: e200. DOI 10.7717/peerj.200, 2013
Since Darwin’s time, waterbirds have been considered an important vector for the dispersal of continental aquatic invertebrates. Bird movements have facilitated the worldwide invasion of the American brine shrimp Artemia franciscana, transporting cysts (diapausing eggs), and favouring rapid range expansions from introduction sites. Here we address the impact of bird migratory flyways on the population genetic structure and phylogeography of A. franciscana in its native range in the Americas. We examined the sequence variation for two mitochondrial gene fragments (COI and 16S for a subset of the data) in a large set of population samples representing the entire native range of A. franciscana. Furthermore, we performed Mantel tests and redundancy analyses (RDA) to test the role of flyways, geography and human introductions on the phylogeography and population genetic structure at a continental scale. A. franciscana mitochondrial DNA was very diverse, with two main clades, largely corresponding to Pacific and Atlantic populations, mirroring American bird flyways. There was a high degree of regional endemism, with populations subdivided into at least 12 divergent, geographically restricted and largely allopatric mitochondrial lineages, and high levels of population structure ( Φ ST of 0.92), indicating low ongoing gene flow. We found evidence of human-mediated introductions in nine out of 39 populations analysed. Once these populations were removed, Mantel tests revealed a strong association between genetic variation and geographic distance (i.e., isolation-by-distance pattern). RDA showed that shared bird flyways explained around 20% of the variance in genetic distance between populations and this was highly significant, once geographic distance was controlled for. The variance explained increased to 30% when the factor human introduction was included in the model. Our findings suggest that bird-mediated transport of brine shrimp propagules does not result in substantial ongoing gene flow; instead, it had a significant historical role on the current species phylogeography, facilitating the colonisation of new aquatic environments as they become available along their main migratory flyways.
Parasitology Research, 2007
Artemia franciscana is an invasive crustacean expanding its range in hypersaline wetlands in the Mediterranean region and replacing native Artemia parthenogenetica and Artemia salina. Native brine shrimps are known as intermediate hosts of cestodes; infected individuals exhibit changes in their behaviour and appearance, thus facilitating the parasite transmission to the avian hosts by predation. To assess whether invasive brine shrimps participate in the cestode life cycles to the same extent as the native species, we examined the natural infections in seven populations of Artemia spp. along the southern coast of Spain and Portugal: three populations of each A. franciscana and A. parthenogenetica and one population of A. salina. Ten cestode species were found in A. parthenogenetica, while only six were recorded in each of A. salina and A. franciscana. The overall infection was consistently higher in native than in invasive populations. For a particular cestode species, the prevalence or abundance was significantly higher in a native population for 54 pairwise comparisons and only higher for an invasive population for 4 pairwise comparisons. These results suggest that cestodes may influence competitive interactions between native and invasive brine shrimps, thus partly explaining the invasive success of A. franciscana.
Freshwater Biology, 2002
1. Inland wetlands constitute ecological islands of aquatic habitat often isolated by huge areas of non-suitable terrestrial habitats. Although most aquatic organisms lack the capacity to disperse by themselves to neighbouring catchments, many species present widespread distributions consistent with frequent dispersal by migratory waterbirds. 2. A literature review indicates that bird-mediated passive transport of propagules of aquatic invertebrates and plants is a frequent process in the field, at least at a local scale. Both endozoochory (internal transport) and ectozoochory (external transport) are important processes. 3. The characteristics of the dispersed and the disperser species that facilitate such transport remain largely uninvestigated, but a small propagule size tends to favour dispersal by both internal and external transport. 4. We review the information currently available on the processes of waterbird-mediated dispersal, establishing the limits of current knowledge and highlighting problems with research methods used in previous studies. We also identify studies required in the future to further our understanding of the role of such dispersal in aquatic ecology.