The marbled crayfish (Procambarus virginalis) is a triploid and parthenogenetic freshwater crayfi... more The marbled crayfish (Procambarus virginalis) is a triploid and parthenogenetic freshwater crayfish species that has colonized diverse habitats around the world. Previous studies suggested that the clonal marbled crayfish population descended as recently as 25 years ago from a single specimen of P. fallax, the sexually reproducing parent species. However, the genetic, phylogeographic, and mechanistic origins of the species have remained enigmatic. We have now constructed a new genome assembly for P. virginalis to support a detailed phylogeographic analysis of the diploid parent species, Procambarus fallax. Our results strongly suggest that both parental haplotypes of P. virginalis were inherited from the Everglades subpopulation of P. fallax. Comprehensive whole-genome sequencing also detected triploid specimens in the same subpopulation, which either represent evolutionarily important intermediate genotypes or independent parthenogenetic lineages arising among the sexual parent pop...
ABSTRACTThe marbled crayfish is the only obligately parthenogenetic decapod crustacean and a nove... more ABSTRACTThe marbled crayfish is the only obligately parthenogenetic decapod crustacean and a novel research model and invasive animal on three continents. It is regarded either as a parthenogenetic form of slough crayfish Procambarus fallax or as a separate species named Procambarus virginalis. In order to investigate the species question of this unusual crayfish in detail we have identified the similarities and differences in morphology, life history, genetics, behaviour, ecology and biogeography between marbled crayfish and its most likely parent species P. fallax. We have investigated specimens from natural habitats, laboratory colonies and museum collections and performed a meta-analysis of our data and published data. Our COI based molecular tree with 27 Cambaridae confirms closest relationship of marbled crayfish with P. fallax. Marbled crayfish and P. fallax are similar with respect to morphological characters, coloration and body proportions, but differ considerably with res...
Predator-prey interactions are often size-structured and focused on smaller vulnerable size class... more Predator-prey interactions are often size-structured and focused on smaller vulnerable size classes. Predators are also predicted to sort prey communities according to relative vulnerabilities. Increased system productivity and juvenile growth may benefit some species more than others, making relative vulnerability non-static and growth-mediated. We hypothesized that increased system productivity would weaken juvenile-stage predation generally, and potentially shift the community sorting effects of a predator. Using replicated wetland mesocosms we quantified the effects of a generalist size-specific crayfish predator (Procambarus fallax) on juveniles of two species of apple snails (Pomacea spp.) under two levels of system productivity (low vs. high). After 6 weeks of exposure, we quantified predator and productivity effects on snail survival, biomass, and composition of the assemblage. Crayfish depressed the final density and biomass of snails, and sorted the assemblage, selectively...
There was an error in the abstract of the original publication. The 9th sentence of abstract shou... more There was an error in the abstract of the original publication. The 9th sentence of abstract should be:"Our results are inconsistent with predictions about the sorting effects of predators across productivity gradients because the more resistant prey dominated at low productivity."
Effects of predators on prey populations can be especially strong in aquatic ecosystems, but dist... more Effects of predators on prey populations can be especially strong in aquatic ecosystems, but disturbances may mediate the strength of predator limitation and even allow outbreaks of some prey populations. In a two-year study we investigated the numerical responses of crayfish (Procambarus fallax) and small fishes (Poeciliidae and Fundulidae) to a brief hydrological disturbance in replicated freshwater wetlands with an experimental drying and large predatory fish reduction. The experiment and an in situ predation assay tested the component of the consumer stress model positing that disturbances release prey from predator limitation. In the disturbed wetlands, abundances of large predatory fish were seasonally reduced, similar to dynamics in the Everglades (southern Florida). Densities of small fish were unaffected by the disturbance, but crayfish densities, which were similar across all wetlands before drying, increased almost threefold in the year after the disturbance. Upon re-floo...
ABSTRACT One of the best studied freshwater predator–prey interactions is arguably that between c... more ABSTRACT One of the best studied freshwater predator–prey interactions is arguably that between crayfish and gastropods. In many ecosystems, crayfish limit populations of thin-shelled snails and induce changes in snail traits. However, the connection between these 2 phenomena and, therefore, the mechanism by which crayfish have population-dynamic effects on snails, has been little studied. I examined the population-level effects of 2 procambarid crayfish (Procambarus alleni and Procambarus fallax) on a 2-species assemblage of snails (physids: Hatia cubensis, planorbids: Planorbella duryi) in experimental mesocosms. Observations early in the experiment suggested that both snail species were responding behaviorally to the crayfish, especially to P. alleni. At the end of the study (8 wk), both species of crayfish had reduced filamentous periphyton by 50% and snail density by >95%. The 2 crayfish species had quantitatively similar effects on both trophic levels. Physids laid eggs early in the study, but they had no size refuge and were almost completely eliminated from the crayfish treatments by the end of the study. Large planorbids had a size refuge and persisted with crayfish, but almost no recruitment occurred in the presence of crayfish. Per-capita egg-laying rates on bottom substrates at the end of the experiment were equal between treatments, results indicating that planorbids persisted in laying eggs and that crayfish continued to consume the hatchlings. The observations from this experiment suggest that crayfish limit snail populations primarily by direct consumptive effects.
Journal of the North American Benthological Society
Stable isotope enrichment experiments offer a potentially powerful way to examine the base of aqu... more Stable isotope enrichment experiments offer a potentially powerful way to examine the base of aquatic food webs, but interpretation of the data from these experiments may be confounded by prob- lem ss uc ha ss elective ingestion/assimilation of bulk food sources by consumers, variable tracer enrichment over time, and the failure of consumers to approach isotopic equilibrium with the tracer in their diets over the course of the experiment. Our study examined data from a stable isotope addition experiment in which 15N-labeled NH 4 wa sa dded to a midwestern US stream. A compartment model was used to provide insights into the kinetics of 15N uptake and release from algae, heterotrophic microbes colonizing detritus, and invertebrate consumers. The model accounted for temporal variation in the degree of isotopic enrichment and did not require the assumption of isotopic equilibrium between consumers and their diets. The importance of instream production (i.e., growth of algae and microbes...
Habitat selection of the slough crayfish (Procambarus fallax), within the ridge and slough landsc... more Habitat selection of the slough crayfish (Procambarus fallax), within the ridge and slough landscape in the central Everglades presents a unique study system to test this theory. Crayfish have the choice of two adjacent habitats in the wet season, deeper sloughs with submerged ...
Effects of predators on prey populations can be especially strong in aquatic ecosystems, but dist... more Effects of predators on prey populations can be especially strong in aquatic ecosystems, but disturbances may mediate the strength of predator limitation and even allow outbreaks of some prey populations. In a two-year study we investigated the numerical responses of crayfish (Procambarus fallax) and small fishes (Poeciliidae and Fundulidae) to a brief hydrological disturbance in replicated freshwater wetlands with an experimental drying and large predatory fish reduction. The experiment and an in situ predation assay tested the component of the consumer stress model positing that disturbances release prey from predator limitation. In the disturbed wetlands, abundances of large predatory fish were seasonally reduced, similar to dynamics in the Everglades (southern Florida). Densities of small fish were unaffected by the disturbance, but crayfish densities, which were similar across all wetlands before drying, increased almost threefold in the year after the disturbance. Upon re-flooding, juvenile crayfish survival was inversely related to the abundance of large fish across wetlands, but we found no evidence for enhanced algal food quality. At a larger landscape scale (500 km2 of the Everglades), crayfish densities over eight years were positively correlated with the severity of local dry disturbances (up to 99 days dry) during the preceding dry season. In contrast, densities of small-bodied fishes in the same wetlands were seasonally depressed by dry disturbances. The results from our experimental wetland drought and the observations of crayfish densities in the Everglades represent a large-scale example of prey population release following a hydrological disturbance in a freshwater ecosystem. The conditions producing crayfish pulses in the Everglades appear consistent with the mechanics of the consumer stress model, and we suggest crayfish pulses may influence the number of nesting wading birds in the Everglades.
The marbled crayfish (Procambarus virginalis) is a triploid and parthenogenetic freshwater crayfi... more The marbled crayfish (Procambarus virginalis) is a triploid and parthenogenetic freshwater crayfish species that has colonized diverse habitats around the world. Previous studies suggested that the clonal marbled crayfish population descended as recently as 25 years ago from a single specimen of P. fallax, the sexually reproducing parent species. However, the genetic, phylogeographic, and mechanistic origins of the species have remained enigmatic. We have now constructed a new genome assembly for P. virginalis to support a detailed phylogeographic analysis of the diploid parent species, Procambarus fallax. Our results strongly suggest that both parental haplotypes of P. virginalis were inherited from the Everglades subpopulation of P. fallax. Comprehensive whole-genome sequencing also detected triploid specimens in the same subpopulation, which either represent evolutionarily important intermediate genotypes or independent parthenogenetic lineages arising among the sexual parent pop...
ABSTRACTThe marbled crayfish is the only obligately parthenogenetic decapod crustacean and a nove... more ABSTRACTThe marbled crayfish is the only obligately parthenogenetic decapod crustacean and a novel research model and invasive animal on three continents. It is regarded either as a parthenogenetic form of slough crayfish Procambarus fallax or as a separate species named Procambarus virginalis. In order to investigate the species question of this unusual crayfish in detail we have identified the similarities and differences in morphology, life history, genetics, behaviour, ecology and biogeography between marbled crayfish and its most likely parent species P. fallax. We have investigated specimens from natural habitats, laboratory colonies and museum collections and performed a meta-analysis of our data and published data. Our COI based molecular tree with 27 Cambaridae confirms closest relationship of marbled crayfish with P. fallax. Marbled crayfish and P. fallax are similar with respect to morphological characters, coloration and body proportions, but differ considerably with res...
Predator-prey interactions are often size-structured and focused on smaller vulnerable size class... more Predator-prey interactions are often size-structured and focused on smaller vulnerable size classes. Predators are also predicted to sort prey communities according to relative vulnerabilities. Increased system productivity and juvenile growth may benefit some species more than others, making relative vulnerability non-static and growth-mediated. We hypothesized that increased system productivity would weaken juvenile-stage predation generally, and potentially shift the community sorting effects of a predator. Using replicated wetland mesocosms we quantified the effects of a generalist size-specific crayfish predator (Procambarus fallax) on juveniles of two species of apple snails (Pomacea spp.) under two levels of system productivity (low vs. high). After 6 weeks of exposure, we quantified predator and productivity effects on snail survival, biomass, and composition of the assemblage. Crayfish depressed the final density and biomass of snails, and sorted the assemblage, selectively...
There was an error in the abstract of the original publication. The 9th sentence of abstract shou... more There was an error in the abstract of the original publication. The 9th sentence of abstract should be:"Our results are inconsistent with predictions about the sorting effects of predators across productivity gradients because the more resistant prey dominated at low productivity."
Effects of predators on prey populations can be especially strong in aquatic ecosystems, but dist... more Effects of predators on prey populations can be especially strong in aquatic ecosystems, but disturbances may mediate the strength of predator limitation and even allow outbreaks of some prey populations. In a two-year study we investigated the numerical responses of crayfish (Procambarus fallax) and small fishes (Poeciliidae and Fundulidae) to a brief hydrological disturbance in replicated freshwater wetlands with an experimental drying and large predatory fish reduction. The experiment and an in situ predation assay tested the component of the consumer stress model positing that disturbances release prey from predator limitation. In the disturbed wetlands, abundances of large predatory fish were seasonally reduced, similar to dynamics in the Everglades (southern Florida). Densities of small fish were unaffected by the disturbance, but crayfish densities, which were similar across all wetlands before drying, increased almost threefold in the year after the disturbance. Upon re-floo...
ABSTRACT One of the best studied freshwater predator–prey interactions is arguably that between c... more ABSTRACT One of the best studied freshwater predator–prey interactions is arguably that between crayfish and gastropods. In many ecosystems, crayfish limit populations of thin-shelled snails and induce changes in snail traits. However, the connection between these 2 phenomena and, therefore, the mechanism by which crayfish have population-dynamic effects on snails, has been little studied. I examined the population-level effects of 2 procambarid crayfish (Procambarus alleni and Procambarus fallax) on a 2-species assemblage of snails (physids: Hatia cubensis, planorbids: Planorbella duryi) in experimental mesocosms. Observations early in the experiment suggested that both snail species were responding behaviorally to the crayfish, especially to P. alleni. At the end of the study (8 wk), both species of crayfish had reduced filamentous periphyton by 50% and snail density by >95%. The 2 crayfish species had quantitatively similar effects on both trophic levels. Physids laid eggs early in the study, but they had no size refuge and were almost completely eliminated from the crayfish treatments by the end of the study. Large planorbids had a size refuge and persisted with crayfish, but almost no recruitment occurred in the presence of crayfish. Per-capita egg-laying rates on bottom substrates at the end of the experiment were equal between treatments, results indicating that planorbids persisted in laying eggs and that crayfish continued to consume the hatchlings. The observations from this experiment suggest that crayfish limit snail populations primarily by direct consumptive effects.
Journal of the North American Benthological Society
Stable isotope enrichment experiments offer a potentially powerful way to examine the base of aqu... more Stable isotope enrichment experiments offer a potentially powerful way to examine the base of aquatic food webs, but interpretation of the data from these experiments may be confounded by prob- lem ss uc ha ss elective ingestion/assimilation of bulk food sources by consumers, variable tracer enrichment over time, and the failure of consumers to approach isotopic equilibrium with the tracer in their diets over the course of the experiment. Our study examined data from a stable isotope addition experiment in which 15N-labeled NH 4 wa sa dded to a midwestern US stream. A compartment model was used to provide insights into the kinetics of 15N uptake and release from algae, heterotrophic microbes colonizing detritus, and invertebrate consumers. The model accounted for temporal variation in the degree of isotopic enrichment and did not require the assumption of isotopic equilibrium between consumers and their diets. The importance of instream production (i.e., growth of algae and microbes...
Habitat selection of the slough crayfish (Procambarus fallax), within the ridge and slough landsc... more Habitat selection of the slough crayfish (Procambarus fallax), within the ridge and slough landscape in the central Everglades presents a unique study system to test this theory. Crayfish have the choice of two adjacent habitats in the wet season, deeper sloughs with submerged ...
Effects of predators on prey populations can be especially strong in aquatic ecosystems, but dist... more Effects of predators on prey populations can be especially strong in aquatic ecosystems, but disturbances may mediate the strength of predator limitation and even allow outbreaks of some prey populations. In a two-year study we investigated the numerical responses of crayfish (Procambarus fallax) and small fishes (Poeciliidae and Fundulidae) to a brief hydrological disturbance in replicated freshwater wetlands with an experimental drying and large predatory fish reduction. The experiment and an in situ predation assay tested the component of the consumer stress model positing that disturbances release prey from predator limitation. In the disturbed wetlands, abundances of large predatory fish were seasonally reduced, similar to dynamics in the Everglades (southern Florida). Densities of small fish were unaffected by the disturbance, but crayfish densities, which were similar across all wetlands before drying, increased almost threefold in the year after the disturbance. Upon re-flooding, juvenile crayfish survival was inversely related to the abundance of large fish across wetlands, but we found no evidence for enhanced algal food quality. At a larger landscape scale (500 km2 of the Everglades), crayfish densities over eight years were positively correlated with the severity of local dry disturbances (up to 99 days dry) during the preceding dry season. In contrast, densities of small-bodied fishes in the same wetlands were seasonally depressed by dry disturbances. The results from our experimental wetland drought and the observations of crayfish densities in the Everglades represent a large-scale example of prey population release following a hydrological disturbance in a freshwater ecosystem. The conditions producing crayfish pulses in the Everglades appear consistent with the mechanics of the consumer stress model, and we suggest crayfish pulses may influence the number of nesting wading birds in the Everglades.
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