Invasion strategies in clonal aquatic plants: are phenotypic differences caused by phenotypic plasticity or local adaptation (original) (raw)
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Annales de Limnologie - International Journal of Limnology, 2018
Morphological performance of invasive plants can be determined by abiotic factors (e.g. water temperature) and biotic factors (e.g. herbivory). This study investigates the performance of an exotic plant in its native and introduced environments. The questions of study are: Is the performance of Egeria densa in both its native and introduced areas associated with abiotic and/or biotic factors? Is the performance of this plant better in the native or in the introduced area? In order to answer these questions, E. densa individuals collected in France (introduced range) were compared with individuals collected in Brazil (native range). The results demonstrate that E. densa populations sampled in its native areas included a higher percentage of plants grazed than in the introduced range populations, but they also exhibited a superior performance in terms of length and dry mass. In both regions, the performance of the plants was associated mainly with abiotic factors. Whereas the higher t...
Aquatic Invasions, 2009
Introduced plant species appear often more vigorous than their conspecifics in the native range. We investigated the morphological variations of Elodea nuttallii (Planch.) St John and its behaviour in its native and in its introduced habitats. We assessed eight morphological traits of 24 populations in the native North America range and 16 populations in the introduced European range. The introduced taxa can be very distinct in their growth form and size from counterparts in their native range. The shorter broaded-leaved phenotype typically occurs in shallow streams, whereas the longer spacer narrow-leaved phenotype occurs in lakes. Larger leaf width and higher number of lateral shoots-when nutrients are not limiting-may enhance plant performance. The European populations grow more vigorously than their American relatives, possibly because of different selection pressures.
Aquatic Botany, 2012
Invasive freshwater plants are currently spreading rapidly and this is likely to continue with further changes in global climate resulting in changes in physical and chemical conditions in freshwaters. We studied the effect of summer temperature (20 • C, 25 • C and 30 • C) and light availability (25% and 50% of incident light availability) on shoot establishment in terms of growth rate, photosynthesis, and morphology of three invasive aquatic plants (Elodea canadensis, Egeria densa and Lagarosiphon major) in order to assess their interspecific competition. Light availability had an overall stronger effect on growth rate and plant morphology than temperature in the three species. Growth rate increased three-fold from low to high light, and low light reduced belowground biomass, increased stem length, and reduced branching and lateral spread. Photosynthetic rates were the only parameter for which temperature had an equal or stronger effect than light availability. The results show that E. canadensis has the most competitive establishment of the three species in both high and low temperature and light availability. E. densa is most competitive in warm water compared to colder water, whereas the opposite pattern is present for L. major which is most competitive in colder water. In conclusion, we suggest that that E. densa will dominate warmer, shallower waters, whereas L. major will dominate in colder, clear-water lakes, while E. canadensis continues its established role as a pioneer species that is quickly replaced by the two taller species after their arrival.
Do patterns of establishment support invasive status of five aquatic plants in New Zealand?
In order to improve management of invasive aquatic plants, a Weed Risk Assessment Model (WRAM) on aquatic plant species in New Zealand was introduced in 2000. The model ranks different attributes such as habitat versatility, competitive ability, reproductive output, dispersal mechanisms, range of potential impacts, potential distribution, and resistance to management activities. The overall objective of this study was to determine to what extent relative growth rate, photosynthetic rate, light use efficiency, allocation of biomass, and bicarbonate use efficiency during establishment could explain the rank assigned to 5 species in the WRAM: Hydrilla verticillata (Linn.f.) Royle, Ceratophyllum demersum L., Egeria densa Planchon, Lagarosiphon major (Ridley) Moss, and Elodea canadensis Michaux. Overall, our results indicate that the parameters measured for 5 invasive species do not support the rank assigned to these same species in the WRAM. Our study investigated only the growth performance of shoots during establishment and thus only a small part of a plant's life cycle. Although a high rate of establishment might result in a high local abundance, as well as a high regional distribution, our study illustrates that this is a single component to determining overall invasive status of the plants. Consequently, this indicates that other parts of the life cycle and ecology also contribute to high rate of invasion by the highly ranked species H. verticillata and C. demersum.
Plant biology (Stuttgart, Germany), 2018
Two closely related alien submerged aquatic plants were introduced in Europe. The new invader (Elodea nuttallii) gradually displaced E. canadensis even at sites where the latter was well-established. The aim of the study was to evaluate the combined effects of environmental factors on several phenotypic characteristics of the two Elodea species, and to relate these phenotypic characteristics to the invasion success of E. nuttallii over E. canadensis. In a factorial design, Elodea plants were grown in aquaria containing five different nitrogen concentrations and incubated at five different light intensities. We used six functional traits (apical shoot relative growth rate (RGR), total shoot RGR, relative elongation, root length, lateral spread, branching degree) to measure the environmental response of the species. We calculated plasticity indexes to express the phenotypic differences between species. Light and nitrogen jointly triggered the development of phenotypic characteristics ...
Biological Invasions, 2011
Submersed aquatic plants have a key role in maintaining functioning aquatic ecosystems through their effects on the hydrological regime, sedimentation, nutrient cycling and habitat of associated fauna. Modifications of aquatic plant communities, for example through the introduction of invasive species, can alter these functions. In the Sacramento-San Joaquin River Delta, California, a major invasive submersed plant, Brazilian waterweed Egeria densa, has become widespread and greatly affected the functionality of the submersed aquatic plant community. Rapid assessments of the distribution and abundance of this species are therefore crucial to direct management actions early in the season. Given the E. densa bimodal growth pattern (late spring and fall growth peaks), summer assessments of this species may indicate which and where other submersed species may occur and fall assessments may indicate where this and other species may occur in the following spring, primarily because the Delta's winter water temperatures are usually insufficient to kill submersed aquatic plant species. We assessed community composition and distribution in the fall of 2007 and summer of 2008 using geostatistical analysis; and measured summer biomass, temperature, pH, salinity, and turbidity. In the fall of 2007, submersed aquatic plants covered a much higher proportion of the waterways (60.7%) than in the summer of 2008 (37.4%), with a significant overlap between the seasonal distribution of native and nonnative species. Most patches were monospecific, and multispecies patches had significantly higher dominance by E. densa, co-occurring especially with Ceratophyllum demersum. As species richness of non-natives increased there was a significant decrease in richness of natives, and of native biomass. Sustained E. densa summer biomass negatively affected the likelihood of presence of Myriophyllum spicatum, Potamogeton crispus, and Elodea canadensis but not their biomass within patches. Depth, temperature and salinity were associated with biomass; however, the direction of the effect was species specific. Our results suggest that despite native and invasive non-native submersed plant species sharing available niches in the Delta, E. densa affects aquatic plant community structure and composition by facilitating persistence of some species and reducing the likelihood of establishment of other species. Successful management of this species may therefore facilitate shifts in existing non-native or native plant species.
Trait responses of invasive aquatic macrophyte congeners: colonizing diploid outperforms polyploid
AoB PLANTS, 2016
Understanding traits underlying colonization and niche breadth of invasive plants is key to developing sustainable management solutions to curtail invasions at the establishment phase, when efforts are often most effective. The aim of this study was to evaluate how two invasive congeners differing in ploidy respond to high and lowresource availability following establishment from asexual fragments. Because polyploids are expected to have wider niche breadths than diploid ancestors, we predicted that a decaploid species would have superior ability to maximize resource uptake and use, and outperform a diploid congener when colonizing environments with contrasting light and nutrient availability. A mesocosm experiment was designed to test the main and interactive effects of ploidy (diploid and decaploid) and soil nutrient availability (low and high) nested within light environments (shade and sun) of two invasive aquatic plant congeners. Counter to our predictions, the diploid congener...
Ecology, 2003
Geographic variation can lead to the evolution of different local varieties within a given species, therefore influencing its distribution and genetic structure. We investigated the contribution of plasticity and local adaptation to the performance of a common aquatic plant (Potamogeton pectinatus) in contrasting climates, using reciprocal transplants at three experimental sites across a latitudinal cline in Europe. Plants from 54 genets, originally collected from 14 populations situated within four climatic regions (subarctic, cold temperate, mild temperate, and mediterranean) were grown in three different localities within three of these regions (cold temperate, Norway; mild temperate, The Netherlands; mediterranean, Spain). Tuber production was highest for the mild-temperate genets, irrespective of locality where the genets were grown. Selection coefficients indicated that populations at the European center of the species distribution perform better than all other populations, at all sites. However, marginal populations showed changes in life-history traits, such as compressed life cycles in the north and true perenniality in the south, that may allow them to perform better locally, at the limits of their distribution range. Our results thus suggest that local adaptation may overlap spatially with center-periphery gradients in performance caused by genetic factors (such as genetic drift and inbreeding in range-marginal populations).