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Luc Brendonck - One of the best experts on this subject based on the ideXlab platform.
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The power of numbers: dynamics of hatching and dormant Egg production in two populations of the water flea Daphnia magna
Aquatic Ecology, 2019Co-Authors: Aurora N. Geerts, Luc Brendonck, Kelle Moreau, Bram Vanschoenwinkel, Joost Vanoverbeke, Luc De MeesterAbstract:Many organisms that live in inland standing waters produce dormant life stages that can accumulate in propagule Banks to survive temporarily unfavourable periods. These Egg Banks have important effects on the ecology of populations and communities in terms of phenology, population densities, the probability of extinction, species diversity and habitat connectivity in time and space. They also have important consequences for the evolutionary versatility of populations. Although diapause and dormant Egg Banks in freshwater zooplankton have been studied for several decades, little is known about the quantitative contribution of Egg production and hatching to yearly Egg Bank budgets and their seasonality in natural ponds and lakes. Here we quantified inter- and intra-annual variation in hatching and dormant Egg production in the water flea Daphnia magna in two natural shallow ponds in Flanders (Belgium) using high-intensity sampling and in situ measurements. Hatching started in spring and occurred in several bouts (April–July), accumulating to a yearly average total of 3.5 × 103 hatchlings m−2. Dormant Egg production occurred in one-to-three bouts mainly during late spring and summer (May–August), resulting in a total yearly production ranging from 1.2 × 104 up to 17.3 × 104 ephippia m−2. In both years, there was an average surplus of 3.14 × 104 and 15.24 × 104 ephippia produced m−2 for ponds OM2 and OM3, respectively, contributing to the accumulation of the persistent Egg Bank. We discuss the ecological and evolutionary consequences of both the high number of ephippia that are produced and the high number of hatchlings at the start of each growing season.
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Dormancy and dispersal as mediators of zooplankton population and community dynamics along a hydrological disturbance gradient in inland temporary pools
Hydrobiologia, 2016Co-Authors: Luc Brendonck, Tom Pinceel, Raquel OrtellsAbstract:At some stage in their life cycle, most zooplankton in temporary waters produce dormant Eggs that assemble in a persistent Egg Bank to cope with unfavourable conditions. As part of a risk-spreading strategy, only a fraction of the Egg Bank hatches during a single inundation. Besides this dispersal in time, resistant dormant Eggs also disperse in space via vectors including wind, water and animals. The structure and functioning of the dormant Egg Bank has important consequences for (meta) population and (meta) community structure and dynamics. Here, we merge empirical and theoretical data into a conceptual framework for the study of population and community responses in temporary ponds along a gradient in hydrological disturbance. Overall, we conclude that changes in hydrological disturbance may compromise both the abiotic (i.e. water quality) and biotic (i.e. population and community processes) integrity of temporary pools which is especially relevant in light of ongoing anthropogenic alterations in the hydrology of inland waters.
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banco de huevos de resistencia revela una alta riqueza especifica de cladoceros en charcos temporales altoandinos resting Egg Bank reveals high cladoceran species richness in high altitude temporary peat land pools
Revista Boliviana de Ecología y Conservación Ambiental, 2013Co-Authors: Jorge S Coronel, Ximena Aguilera, Steven Decleck, Luc BrendonckAbstract:El analisis del banco de efipias (huevos de dormancia) presente en el sedimento de los cuerpos de agua ha resultado ser una herramienta util para el estudio de la diversidad de cladoceros en sistemas permanentes de agua. Este metodo ha sido inexplorado en sistemas temporales que experimentan un periodo seco durante una parte del ano. En este estudio se evaluo la riqueza de especies del ensamblaje de cladoceros (Branchiopoda, Crustacea) obtenido mediante la eclosion de efipias provenientes del sedimento de 61 charcos temporales de la cordillera del Tunari en Bolivia. La eclosion de efipias revelo mas especies de cladoceros (total= 24; promedio= 6.7) que el numero obtenido de los muestreos del ensamblaje activo (total= 21; promedio= 4.6). En promedio, el analisis de las efipias contribuyo con 2.1 especies de cladoceros por charco. El numero de cladoceros (ensamblaje activo + analisis de efipia) alcanzo un total de 28 especies. Analisis de redundancia indicaron diferencias significativas entre la composicion del ensamblaje activo y el ensamblaje obtenido por eclosion de las efipias. La cobertura vegetal fue la principal variable que explico una variacion en la estructura del ensamblaje activo de cladoceros, mientras que para el ensamblaje obtenido de la eclosion de efipias estuvieron la clorofila-a, el grosor de la capa de sedimento, y la conectividad entre charcos. Palabras claves: Bolivia, Charcos temporales andinos, huevos de dormancia, zooplancton de los Andes. ABSTRACT The use of Egg Bank analysis proved a valuable approach to uncover hidden diversity in permanent lakes. The efficiency of the method remains largely unexplored in temporary aquatic systems that remain dry for a variable part of the year. We assessed species richness of the cladoceran assemblage (Branchiopoda, Crustacea) from the dormant Egg Bank of 61 temporary peat land pools in the high Andes of Bolivia. The analysis of the dormant Egg Bank yielded more species (total: 24; mean per peat land pool: 6.7) than snapshot samples from active communities taken previously (total: 21; mean per peat land pool: 4.6). On average, the dormant Egg Bank resulted in the detection of 2.1 (45%) more cladoceran species per peat land pool than on the basis of active cladoceran assemblages. The accumulated (active plus dormant) cladoceran species richness of the study peat land pools mounted up to 28 species. RDA analyses indicated a significant difference in assemblage composition between dormant and active samples. Different environmental variables explained variation in the structure of the dormant and active cladoceran assemblages. Water plant cover significantly explained variation in active assemblages, while a model constructed by chlorophyll-a, sediment thickness, and connectivity explained variation in dormant cladoceran assemblages. The analysis of the dormant assemblages was essential, not only in revealing the potential species richness but also for better understanding assemblage structure of aquatic organisms. Key words: Bolivia, Andean temporary pools, Resting Eggs, Bolivian zooplankton, Egg-morphotype.
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Pesticide exposure impacts not only hatching of dormant Eggs, but also hatchling survival and performance in the water flea Daphnia magna
Ecotoxicology (London England), 2013Co-Authors: Sabine Navis, Luc De Meester, Aline Waterkeyn, Tom Voet, Luc BrendonckAbstract:Laboratory ecotoxicity tests and biomonitoring in aquatic systems are currently based on the active component of invertebrate communities. Even though dormant Egg Banks are crucial for the long term survival and community dynamics of many aquatic organisms, the effects of anthropogenic activities on dormant Egg Bank dynamics have rarely been studied. In this study we investigated the effects of two pesticides with a different mode of action (carbaryl and fenoxycarb) on hatching of Daphnia magna dormant Eggs (ephippia) as well as on survival, growth and reproduction of the hatched neonates. Dormant Eggs were exposed to the pesticides simultaneously to incubation under conditions that induce hatching (long daylight and 20 °C). Carbaryl had no negative effects on embryonic development or hatching rate up to concentrations almost 1,000 times the median effect concentration (EC50) of neonate survival in acute tests. Fenoxycarb, however, had a significant dose-related effect by delaying or completely stopping the hatching process and caused severe abnormalities in developing individuals. Both pesticides had significant negative effects on survival and reproduction of the hatchlings. These results indicate that, in addition to inducing mortality of active individuals, pesticides can affect zooplankton communities by altering hatching dynamics and life history traits of hatched individuals. We briefly discuss how such pollution induced changes in the benthic-pelagic coupling could translate into trans-generational effects impacting ecological and evolutionary dynamics.
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Hatching phenology, life history and Egg Bank size of fairy shrimp Branchipodopsis spp. (Branchiopoda, Crustacea) in relation to the ephemerality of their rock pool habitat
Aquatic Ecology, 2010Co-Authors: Bram Vanschoenwinkel, Maitland T. Seaman, Luc BrendonckAbstract: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.
Piet Spaak - One of the best experts on this subject based on the ideXlab platform.
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sedimentary and Egg Bank dna from 3 european lakes reveal concurrent changes in the composition and diversity of cyanobacterial and daphnia communities
Hydrobiologia, 2017Co-Authors: Marieeve Monchamp, Ioana Varduca Enache, Patrick Turko, Francesco Pomati, Geta Risnoveanu, Piet SpaakAbstract:Eutrophication generally favours the growth of cyanobacteria over eukaryotic green algae in freshwater lakes. Cyanobacteria constitute a poor food source for the waterflea Daphnia, an important primary consumer of phytoplankton in lakes. While it is known that some Daphnia species are adapted to eutrophic conditions and can cope with cyanobacteria in their diet, it is less known whether cyanobacterial community composition can influence Daphnia population structure in lakes. We studied the variation in genetic diversity of Daphnia resting Eggs and cyanobacterial DNA preserved in sediment cores from three European lakes impacted by eutrophication. Our retrospective analysis confirms that D. galeata invaded the two pre-alpine lakes around the middle of the twentieth century, hybridized with and became dominant over D. longispina. This coincides with the presence in all lakes and the increase in the proportion of colonial and filamentous cyanobacteria in the pre-alpine lakes. The recent re-oligotrophication of the lakes did not reverse the cyanobacterial and Daphnia assemblages to their pre-eutrophication composition and genetic structure, suggesting that both changed irreversibly due to anthropogenic influence on the ecosystems. Genetic analyses applied to lake sedimentary archives have the potential to unveil how different compartments of the food web covary in a changing environment.
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Local human pressures influence gene flow in a hybridizing Daphnia species complex.
Journal of evolutionary biology, 2016Co-Authors: Benjamin Alric, Markus Möst, Piet Spaak, Isabelle Domaizon, Cécile Pignol, Marie-elodie PergaAbstract:Anthropogenic environmental changes are considered critical drivers of the genetic structure of populations and communities through, for example, the facilitation of introgressive hybridization between syntopic species. However, the mechanisms by which environmental perturbations trigger changes in the genetic structure of populations and communities, such as the processes that determine the directionality of hybridization and patterns of mitochondrial introgression over many generations, remain largely unexplored. In this study, the changes in genetic structure of hybridizing members of the Daphnia longispina species complex were reconstructed over the last 100 years for three large temperate lakes under strong anthropogenic pressures via palaeogenetic analyses of resting Egg Banks. Drastic changes in the genetic structure of the Daphnia community, associated with hybridization events between D. longispina and D. galeata and subsequent introgression, were detected in Lakes Geneva and Bourget. In Lake Bourget, these changes were induced by the successful establishment of D. galeata with rising phosphorus levels and reinforced by the sensitivity of D. longispina to fish predation pressure. In Lake Geneva, the pattern of hybridization during eutrophication is more likely a function of the original taxonomic composition of the species complex in this lake. Lakes seem to require at least a meso-oligotrophic status to allow D. galeata populations to establish and accordingly no D. galeata genotypes were found in the Egg Bank of oligotrophic Lake Annecy. In contrast to the generally assumed pattern of unidirectional hybridization in this species complex, bidirectional hybridization was recorded in Lakes Geneva and Bourget. Our results also demonstrate complex genetic trajectories within this species complex and highlight the irreversibility of changes in the genotypic architecture of populations driven by local human pressures. Finally, we show that extensive hybridization and introgression do not necessarily result in a large and homogenous hybrid swarm.
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Population genetic dynamics of an invasion reconstructed from the sediment Egg Bank.
Molecular Ecology, 2015Co-Authors: Markus Möst, Sarah Oexle, Silvia Marková, Dalia Aidukaite, Livia Baumgartner, Hans-bernd Stich, Martin Wessels, Dominik Martin-creuzburg, Piet SpaakAbstract:Biological invasions are a global issue with far-reaching consequences for single species, communities and whole ecosystems. Our understanding of modes and mechanisms of biological invasions requires knowledge of the genetic processes associated with successful invasions. In many instances, this information is particularly difficult to obtain as the initial phases of the invasion process often pass unnoticed and we rely on inferences from contemporary population genetic data. Here, we combined historic information with the genetic analysis of resting Eggs to reconstruct the invasion of Daphnia pulicaria into Lower Lake Constance (LLC) in the 1970s from the resting Egg Bank in the sediments. We identified the invader as ‘European D. pulicaria’ originating from meso- and eutrophic lowland lakes and ponds in Central Europe. The founding population was characterized by extremely low genetic variation in the resting Egg Bank that increased considerably over time. Furthermore, strong evidence for selfing and/or biparental inbreeding was found during the initial phase of the invasion, followed by a drop of selfing rate to low levels in subsequent decades. Moreover, the increase in genetic variation was most pronounced during early stages of the invasion, suggesting additional introductions during this period. Our study highlights that genetic data covering the entire invasion process from its beginning can be crucial to accurately reconstruct the invasion history of a species. We show that propagule Banks can preserve such information enabling the study of population genetic dynamics and sources of genetic variation in successful invasive populations.
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Combined exposure to parasite and pesticide causes increased mortality in the water flea Daphnia
Aquatic Ecology, 2012Co-Authors: Claudia C. Buser, Luc De Meester, Mieke Jansen, Kevin Pauwels, Piet SpaakAbstract:Organisms are exposed to multiple biotic and abiotic environmental stressors, which can influence the dynamics of individual populations and communities. Populations may also genetically adapt to both natural (e.g. disease) and anthropogenic (e.g. chemical pollution) stress. In the present study, we studied fitness consequences of exposure to both a parasite (i.e. biotic) and a pesticide (i.e. abiotic) for the water flea Daphnia. In addition, we investigated whether these fitness consequences change through time as a population evolves. Thus, we exposed Daphnia magna clones, hatched from dormant Eggs isolated from different time layers of a natural dormant Egg Bank, to the parasite Pasteuria ramosa and the insecticide diazinon in a multifactorial experiment. While our experimental treatments for unknown reasons failed to induce disease symptoms in the Daphnia, we did observe a reduced survival of D. magna when simultaneously exposed to both the parasite and the pesticide. No increased mortality upon exposure to individual stressors was observed. We did not observe an evolutionary change in fitness response of the Daphnia clones hatched from different time horizons upon exposure to stressors.
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Reproductive isolation keeps hybridizing Daphnia species distinct
Limnology and Oceanography, 2007Co-Authors: Barbara Keller, Justyna Wolinska, Christoph Tellenbach, Piet SpaakAbstract:We asked whether pre- (e.g., assortative mating, temporal isolation) or postzygotic (e.g., hybrid inviability, infertility) barriers are more likely to affect the hybridization between Daphnia galeata and Daphnia hyalina .W e compared the taxonomic composition of different reproductive stages in the life cycle of D. galeata, D. hyalina, and their hybrids in Greifensee (Switzerland) by using molecular genetic methods. We found evidence for reproductive isolation between taxa and that hybrids in particular, have reduced sexual fitness. The results provide one potential mechanism for parental taxa to remain distinct. F1 hybrid dominance in Greifensee could be explained by an increased asexual reproduction of hybrids that results in a higher proportion of gravid females compared with the parental D. galeata. The low sexual fitness of hybrids limits the abilities of hybrids to take advantage of diapausing Eggs. The lower dispersal ability, including colonization of new habitats, and survival probability during harsh environmental conditions, could, therefore, lead to underestimates of historical hybrid occurrence by using diapausing Egg Bank reconstructions.
Luc De Meester - One of the best experts on this subject based on the ideXlab platform.
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The power of numbers: dynamics of hatching and dormant Egg production in two populations of the water flea Daphnia magna
Aquatic Ecology, 2019Co-Authors: Aurora N. Geerts, Luc Brendonck, Kelle Moreau, Bram Vanschoenwinkel, Joost Vanoverbeke, Luc De MeesterAbstract:Many organisms that live in inland standing waters produce dormant life stages that can accumulate in propagule Banks to survive temporarily unfavourable periods. These Egg Banks have important effects on the ecology of populations and communities in terms of phenology, population densities, the probability of extinction, species diversity and habitat connectivity in time and space. They also have important consequences for the evolutionary versatility of populations. Although diapause and dormant Egg Banks in freshwater zooplankton have been studied for several decades, little is known about the quantitative contribution of Egg production and hatching to yearly Egg Bank budgets and their seasonality in natural ponds and lakes. Here we quantified inter- and intra-annual variation in hatching and dormant Egg production in the water flea Daphnia magna in two natural shallow ponds in Flanders (Belgium) using high-intensity sampling and in situ measurements. Hatching started in spring and occurred in several bouts (April–July), accumulating to a yearly average total of 3.5 × 103 hatchlings m−2. Dormant Egg production occurred in one-to-three bouts mainly during late spring and summer (May–August), resulting in a total yearly production ranging from 1.2 × 104 up to 17.3 × 104 ephippia m−2. In both years, there was an average surplus of 3.14 × 104 and 15.24 × 104 ephippia produced m−2 for ponds OM2 and OM3, respectively, contributing to the accumulation of the persistent Egg Bank. We discuss the ecological and evolutionary consequences of both the high number of ephippia that are produced and the high number of hatchlings at the start of each growing season.
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Temporal genetic stability in natural populations of the waterflea Daphnia magna in response to strong selection pressure.
Molecular ecology, 2016Co-Authors: Luisa Orsini, Hollie Marshall, Maria Cuenca Cambronero, Anurag Chaturvedi, Kelley Thomas, Michael E. Pfrender, Katina I. Spanier, Luc De MeesterAbstract:Studies monitoring changes in genetic diversity and composition through time allow a unique understanding of evolutionary dynamics and persistence of natural populations. However, such studies are often limited to species with short generation times that can be propagated in the laboratory or few exceptional cases in the wild. Species that produce dormant stages provide powerful models for the reconstruction of evolutionary dynamics in the natural environment. A remaining open question is to what extent dormant Egg Banks are an unbiased representation of populations and hence of the species' evolutionary potential, especially in the presence of strong environmental selection. We address this key question using the water flea Daphnia magna, which produces dormant stages that accumulate in biological archives over time. We assess temporal genetic stability in three biological archives, previously used in resurrection ecology studies showing adaptive evolutionary responses to rapid environmental change. We show that neutral genetic diversity does not decline with the age of the population and it is maintained in the presence of strong selection. In addition, by comparing temporal genetic stability in hatched and unhatched populations from the same biological archive, we show that dormant Egg Banks can be consulted to obtain a reliable measure of genetic diversity over time, at least in the multidecadal time frame studied here. The stability of neutral genetic diversity through time is likely mediated by the buffering effect of the resting Egg Bank.
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Pesticide exposure impacts not only hatching of dormant Eggs, but also hatchling survival and performance in the water flea Daphnia magna
Ecotoxicology (London England), 2013Co-Authors: Sabine Navis, Luc De Meester, Aline Waterkeyn, Tom Voet, Luc BrendonckAbstract:Laboratory ecotoxicity tests and biomonitoring in aquatic systems are currently based on the active component of invertebrate communities. Even though dormant Egg Banks are crucial for the long term survival and community dynamics of many aquatic organisms, the effects of anthropogenic activities on dormant Egg Bank dynamics have rarely been studied. In this study we investigated the effects of two pesticides with a different mode of action (carbaryl and fenoxycarb) on hatching of Daphnia magna dormant Eggs (ephippia) as well as on survival, growth and reproduction of the hatched neonates. Dormant Eggs were exposed to the pesticides simultaneously to incubation under conditions that induce hatching (long daylight and 20 °C). Carbaryl had no negative effects on embryonic development or hatching rate up to concentrations almost 1,000 times the median effect concentration (EC50) of neonate survival in acute tests. Fenoxycarb, however, had a significant dose-related effect by delaying or completely stopping the hatching process and caused severe abnormalities in developing individuals. Both pesticides had significant negative effects on survival and reproduction of the hatchlings. These results indicate that, in addition to inducing mortality of active individuals, pesticides can affect zooplankton communities by altering hatching dynamics and life history traits of hatched individuals. We briefly discuss how such pollution induced changes in the benthic-pelagic coupling could translate into trans-generational effects impacting ecological and evolutionary dynamics.
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Combined exposure to parasite and pesticide causes increased mortality in the water flea Daphnia
Aquatic Ecology, 2012Co-Authors: Claudia C. Buser, Luc De Meester, Mieke Jansen, Kevin Pauwels, Piet SpaakAbstract:Organisms are exposed to multiple biotic and abiotic environmental stressors, which can influence the dynamics of individual populations and communities. Populations may also genetically adapt to both natural (e.g. disease) and anthropogenic (e.g. chemical pollution) stress. In the present study, we studied fitness consequences of exposure to both a parasite (i.e. biotic) and a pesticide (i.e. abiotic) for the water flea Daphnia. In addition, we investigated whether these fitness consequences change through time as a population evolves. Thus, we exposed Daphnia magna clones, hatched from dormant Eggs isolated from different time layers of a natural dormant Egg Bank, to the parasite Pasteuria ramosa and the insecticide diazinon in a multifactorial experiment. While our experimental treatments for unknown reasons failed to induce disease symptoms in the Daphnia, we did observe a reduced survival of D. magna when simultaneously exposed to both the parasite and the pesticide. No increased mortality upon exposure to individual stressors was observed. We did not observe an evolutionary change in fitness response of the Daphnia clones hatched from different time horizons upon exposure to stressors.
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Invasion of an asexual American water flea clone throughout Africa and rapid displacement of a native sibling species
Proceedings. Biological sciences, 2006Co-Authors: Joachim Mergeay, Dirk Verschuren, Luc De MeesterAbstract:The huge ecological and economic impact of biological invasions creates an urgent need for knowledge of traits that make invading species successful and factors helping indigenous populations to resist displacement by invading species or genotypes. High genetic diversity is generally considered to be advantageous in both processes. Combined with sex, it allows rapid evolution and adaptation to changing environments. We combined paleogenetic analysis with continent-wide survey of genetic diversity at nuclear and mitochondrial loci to reconstruct the invasion history of a single asexual American water flea clone (hybrid Daphnia pulex×Daphnia pulicaria) in Africa. Within 60 years of the original introduction of this invader, it displaced the genetically diverse, sexual population of native D. pulex in Lake Naivasha (Kenya), despite a formidable numerical advantage of the local population and continuous replenishment from a large dormant Egg Bank. Currently, the invading clone has spread throughout the range of native African D. pulex, where it appears to be the only occurring genotype. The absence of genetic variation did not hamper either the continent-wide establishment of this exotic lineage or the effective displacement of an indigenous and genetically diverse sibling species.
Manuel Serra - One of the best experts on this subject based on the ideXlab platform.
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Diapausing Egg Banks, lake size, and genetic diversity in the rotifer Brachionus plicatilis Müller (Rotifera, Monogononta).
Hydrobiologia, 2016Co-Authors: Javier Montero-pau, Manuel Serra, Africa GómezAbstract:Diapausing Egg Banks are reservoirs of ecological and genetic diversity in continental zooplankton. However, although habitat size has often been used as a proxy for population size, the relationship between diapausing Egg Bank size and genetic diversity has not been explicitly tested in zooplankton. We estimated the density and size of diapausing Egg Banks, habitat size and genetic diversity (for mitochondrial and nuclear markers) of 14 populations of the rotifer Brachionus plicatilis in an endorheic basin in the SE Iberian Peninsula. The size of B. plicatilis diapausing Egg Banks ranged across eight orders of magnitude (from 257 to 4.9 × 1010 Eggs). Despite the small geographical scale, populations were strongly structured genetically, but with no evidence of isolation by distance. Habitat size (lake area) was a better predictor of genetic diversity than total diapausing Egg Bank size, but only for mtDNA haplotype diversity. However, as these results were driven by the strong effect of the largest lake in the database, they should be taken with caution. Our results suggest that large lakes could have a disproportionate effect on genetic diversity and that more work is needed to support the use of habitat size as a proxy of population size in rotifers
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Long-term competitive dynamics of two cryptic rotifer species: diapause and fluctuating conditions.
PloS one, 2015Co-Authors: Carmen Gabaldón, Maria Jose Carmona, Javier Montero-pau, Manuel SerraAbstract:Life-history traits may have an important role in promoting species coexistence. However, the complexity of certain life cycles makes it difficult to draw conclusions about the conditions for coexistence or exclusion based on the study of short-term competitive dynamics. Brachionus plicatilis and B. manjavacasare two cryptic rotifer species co-occurring in many lakes on the Iberian Peninsula. They have a complex life cycle in which cyclical parthenogenesis occurs with diapausing stages being the result of sexual reproduction. B. plicatilis and B. manjavacasare identical in morphology and size, their biotic niches are broadly overlapping, and they have similar competitive abilities. However, the species differ in life-history traits involving sexual reproduction and diapause, and respond differently to salinity and temperature. As in the case of certain other species that are extremely similar in morphology, a fluctuating environment are considered to be important for their coexistence. We studied the long-term competitive dynamics of B. plicatilis and B. manjavacas under different salinity regimes (constant and fluctuating). Moreover, we focused on the dynamics of the diapausing Egg Bank to explore how the outcome of the entire life cycle of these rotifers can work to mediate stable coexistence. We demonstrated that these species do not coexist under constant-salinity environment, as the outcome of competition is affected by the level of salinity—at low salinity, B. plicatilis excluded B. manjavacas, and the opposite outcome occurred at high salinity. Competitive dynamics under fluctuating salinity showed that the dominance of one species over the other also tended to fluctuate. The duration of co-occurrence of these species was favoured by salinity fluctuation and perhaps by the existence of a diapausing Egg Bank. Stable coexistence was not found in our system, which suggests that other factors or other salinity fluctuation patterns might act as stabilizing processes in the wild.
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assessing rotifer diapausing Egg Bank diversity and abundance in brackish temporary environments an ex situ sediment incubation approach
Fundamental and Applied Limnology, 2008Co-Authors: Eduardo M Garciaroger, Maria Jose Carmona, Xavier Armengoldiaz, Manuel SerraAbstract:The hatching of diapausing Eggs from sediment samples of ponds and lakes is a fast, easy, and economical technique proven useful for the assessment of diversity and abundance of zooplankton in permanent habitats. Here, we extend and optimize this approach for temporary brackish ponds which may experience great within-year variation in salinity conditions. We studied the species and numbers of rotifers emerging from the sediments of several brackish ponds and saline lakes from Eastern Spain incubated at the full range of salinity conditions observed at the study sites. On average, 82 % of the total observed species in weekly sampling for one year were detected in a single sample of both the sediments and water column. No statistical difference was found between both methods. However, some rotifer species were only observed in the water column samples, but not in sediment hatchlings, and vice versa. We concluded that both methods are not exhaustive by themselves but are complementary. Salinity affected the estimation of both rotifer richness and the density of individuals of each rotifer species that emerged from the incubated sediments. Differences in the density of emerging animals were also found among sites and among combinations of sites and salinities. The latter result indicates that in order to obtain an estimate of the emergence rate for each rotifer species present at a site, it is necessary to incubate sediments at salinity conditions close to their local values.
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a simple model relating habitat features to a diapause Egg Bank
Limnology and Oceanography, 2006Co-Authors: Eduardo M Garciaroger, Maria Jose Carmona, Manuel SerraAbstract:As a way to escape from adverse conditions, many zooplankton populations produce diapausing Eggs that accumulate in the sediments and hatch when suitable environmental conditions are restored. While buried in the sediment, diapausing Eggs may be affected by several processes (i.e., production, hatching, deterioration, and loss). We present a simple mathematical model for the dynamics of diapausing Eggs in the sediment. We were mainly inspired by the model organism Brachionus plicatilis, a cyclical parthenogen rotifer, but the model is applicable to other zooplankters. Three diapausing Egg categories are used as variables in our model: (1) healthy-looking Eggs, assumed to represent the fraction of viable Eggs; (2) deteriorated Eggs, considered unviable; and (3) hatched Eggs, shells remaining in the Egg Bank from past emergences. The model is used to relate the abundances of these Egg categories to production, hatching, deterioration, and loss rates. Then, we propose how relationships between these variables are related to habitat features for temporary populations. Size of the Egg Bank, here considered as the summation of the three Egg categories, is indicative of the quality conditions in the water column (i.e., high production of diapausing Eggs). The ratio among deteriorated and healthy-looking Eggs is indicative of deterioration rates in the sediment, and high ratios are expected when sediment adversity is high. Our analysis also indicates that the ratio among hatched and healthy-looking Eggs is indicative of the hatching rate, which we hypothesize is positively related to both sediment adversity and water-column predictability.
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Hatching and viability of rotifer diapausing Eggs collected from pond sediments
Freshwater Biology, 2006Co-Authors: Eduardo M. García-roger, Maria Jose Carmona, Manuel SerraAbstract:SUMMARY 1. Planktonic rotifers inhabiting variable environments produce diapausing Eggs that accumulate in the sediment of lakes and ponds, forming Egg Banks that may withstand adverse periods. A common assumption in zooplankton diapausing Egg Bank studies is to count as viable all Eggs in the sediment that look healthy. This assumption should be challenged by asking how effectively ‘healthy-looking’ Eggs represent viable Eggs. 2. In this study, viability of more than 1100 ‘healthy-looking’ diapausing Eggs belonging to the Brachionus plicatilis species complex was assessed in a laboratory hatching experiment. Eggs were collected at different depths from sediment cores obtained from 15 ponds located in coastal and inland areas of Eastern Spain. 3. Only approximately one half of the ‘healthy-looking’ diapausing Eggs hatched after incubation in experimental conditions. Almost all the hatchlings (99.4%) survived to maturity. The proportion of ‘healthy-looking’ diapausing Eggs that hatched varied among areas and among ponds within area, and substantially declined with sediment depth. Most of the hatchlings (88%) were obtained from the uppermost 2 cm of sediment. ‘Healthylooking’ Eggs from upper sediment layers hatched after significantly shorter incubation times than Eggs recovered from deeper layers. 4. Both decreased hatching success and increased incubation time for hatching with sediment depth suggest that older ‘healthy-looking’ Eggs are less responsive to hatching stimuli and could become unviable. However, the strong correlation found between the number of ‘healthy-looking’ Eggs and the number of hatchlings indicates that the abundance of ‘healthy-looking’ Eggs is a good index of Egg Bank viability.
Africa Gómez - One of the best experts on this subject based on the ideXlab platform.
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A new molecular diagnostic tool for surveying and monitoring Triops cancriformis populations
PeerJ, 2017Co-Authors: Graham S. Sellers, Larry Griffin, Bernd Hänfling, Africa GómezAbstract:The tadpole shrimp, Triops cancriformis, is a freshwater crustacean listed as endangered in the UK and Europe living in ephemeral pools. Populations are threatened by habitat destruction due to land development for agriculture and increased urbanisation. Despite this, there is a lack of efficient methods for discovering and monitoring populations. Established macroinvertebrate monitoring methods, such as net sampling, are unsuitable given the organism's life history, that include long lived diapausing Eggs, benthic habits and ephemerally active populations. Conventional hatching methods, such as sediment incubation, are both time consuming and potentially confounded by bet-hedging hatching strategies of diapausing Eggs. Here we develop a new molecular diagnostic method to detect viable Egg Banks of T. cancriformis, and compare its performance to two conventional monitoring methods involving diapausing Egg hatching. We apply this method to a collection of pond sediments from the Wildfowl & Wetlands Trust Caerlaverock National Nature Reserve, which holds one of the two remaining British populations of T. cancriformis. DNA barcoding of isolated Eggs, using newly designed species-specific primers for a large region of mtDNA, was used to estimate Egg viability. These estimates were compared to those obtained by the conventional methods of sediment and isolation hatching. Our method outperformed the conventional methods, revealing six ponds holding viable T. cancriformis diapausing Egg Banks in Caerlaverock. Additionally, designed species-specific primers for a short region of mtDNA identified degraded, inviable Eggs and were used to ascertain the levels of recent mortality within an Egg Bank. Together with efficient sugar flotation techniques to extract Eggs from sediment samples, our molecular method proved to be a faster and more powerful alternative for assessing the viability and condition of T. cancriformis diapausing Egg Banks.
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Isolation mediates persistent founder effects on zooplankton colonisation in new temporary ponds.
Scientific reports, 2017Co-Authors: Anna Badosa, Dagmar Frisch, Andy J. Green, Ciro Rico, Africa GómezAbstract:Understanding the colonisation process in zooplankton is crucial for successful restoration of aquatic ecosystems. Here, we analyzed the clonal and genetic structure of the cyclical parthenogenetic rotifer Brachionus plicatilis by following populations established in new temporary ponds during the first three hydroperiods. Rotifer populations established rapidly after first flooding, although colonisation was ongoing throughout the study. Multilocus genotypes from 7 microsatellite loci suggested that most populations (10 of 14) were founded by few clones. The exception was one of the four populations that persisted throughout the studied hydroperiods, where high genetic diversity in the first hydroperiod suggested colonisation from a historical Egg Bank, and no increase in allelic diversity was detected with time. In contrast, in another of these four populations, we observed a progressive increase of allelic diversity. This population became less differentiated from the other populations suggesting effective gene flow soon after its foundation. Allelic diversity and richness remained low in the remaining two, more isolated, populations, suggesting little gene flow. Our results highlight the complexity of colonisation dynamics, with evidence for persistent founder effects in some ponds, but not in others, and with early immigration both from external source populations, and from residual, historical diapausing Egg Banks.
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Diapausing Egg Banks, lake size, and genetic diversity in the rotifer Brachionus plicatilis Müller (Rotifera, Monogononta).
Hydrobiologia, 2016Co-Authors: Javier Montero-pau, Manuel Serra, Africa GómezAbstract:Diapausing Egg Banks are reservoirs of ecological and genetic diversity in continental zooplankton. However, although habitat size has often been used as a proxy for population size, the relationship between diapausing Egg Bank size and genetic diversity has not been explicitly tested in zooplankton. We estimated the density and size of diapausing Egg Banks, habitat size and genetic diversity (for mitochondrial and nuclear markers) of 14 populations of the rotifer Brachionus plicatilis in an endorheic basin in the SE Iberian Peninsula. The size of B. plicatilis diapausing Egg Banks ranged across eight orders of magnitude (from 257 to 4.9 × 1010 Eggs). Despite the small geographical scale, populations were strongly structured genetically, but with no evidence of isolation by distance. Habitat size (lake area) was a better predictor of genetic diversity than total diapausing Egg Bank size, but only for mtDNA haplotype diversity. However, as these results were driven by the strong effect of the largest lake in the database, they should be taken with caution. Our results suggest that large lakes could have a disproportionate effect on genetic diversity and that more work is needed to support the use of habitat size as a proxy of population size in rotifers
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Sex, parthenogenesis and genetic structure of rotifers: microsatellite analysis of contemporary and resting Egg Bank populations
Molecular ecology, 2000Co-Authors: Africa Gómez, Gary R. CarvalhoAbstract:Cyclically parthenogenetic rotifers are a valuable model for investigating the relationship between reproductive mode and population structure, although advances in this field have been hindered by low allozyme variability in these organisms. A high genotypic diversity is predicted after population establishment, which would be eroded by clonal selection during the parthenogenetic phase. The resting Egg Bank, produced sexually, is presumed to store high levels of genetic diversity, with subsequent effects on planktonic population structure. Here, we provide the first application of microsatellite markers to a rotifer planktonic population and its associated resting Egg Bank. Seven polymorphic microsatellite loci were screened in populations of the rotifer Brachionus plicatilis in a temporary pond to analyse: (i) the genetic structure of the resting Egg Bank; (ii) the changes in the genetic structure of rotifer populations during the parthenogenetic phase; and (iii) the population structure after its initiation from resting Eggs. Microsatellites proved to be a useful tool for clone identification, revealing a surprisingly high clonal diversity in rotifer populations. The last sample in the parthenogenetic phase showed evidence of clonal selection, as indicated by a low observed clonal diversity and the appearance of linkage disequilibria. The resting Egg Bank, analysed comprehensively for the first time in any zooplankter, is in Hardy–Weinberg and linkage equilibrium, and contains a high genotypic diversity. Unexpectedly, the resting Egg Bank differed from the planktonic population in its allelic composition, suggesting that resting Egg hatching is biased.
