The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Aaron M. Ellison - One of the best experts on this subject based on the ideXlab platform.
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regulation by the Pitcher Plant sarracenia purpurea of the structure of its inquiline food web
American Midland Naturalist, 2021Co-Authors: Aaron M. Ellison, Leszek A Bledzki, Nicholas J. Gotelli, Jessica L. ButlerAbstract:Phytotelmata, the water-filled habitats in Pitcher Plants, bromeliad tanks, and tree-holes, host multitrophic food webs that are model experimental systems for studying food-web structure and dynamics. However, the Plant usually is considered simply as an inert container, not as an interacting part of the food web. We used a manipulative field experiment with a response-surface design to determine effects of nutrient enrichment (multiple levels of NH4NO3, PO4, and captured prey), top predator (removed or present), and the Plant itself (with or without plastic tubes inserted into the Pitchers to isolate the food web from the Plant) on the macrobial food web within the modified leaves ("Pitchers") of the carnivorous Pitcher Plant Sarracenia purpurea. Connection to the Plant, addition of NH4NO3 and removal of the top predator significantly increased the food web9s saturation, defined as its trophic depth and number of interactions. No effects on food-web saturation resulted from addition of PO4 or supplemental prey. Plants such as S. purpurea that create phytotelmata are more than inert containers and their inhabitants are more than commensal inquilines. Rather, both the Plant and the inquilines are partners in a complex network of interactions.
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regulation by the Pitcher Plant sarracenia purpurea of the structure of its inquiline food web
bioRxiv, 2020Co-Authors: Aaron M. Ellison, Leszek A Bledzki, Nicholas J. Gotelli, Jessica L. ButlerAbstract:Phytotelmata, the water-filled habitats in Pitcher Plants, bromeliad tanks, and tree-holes, host multitrophic food webs that are model experimental systems for studying food-web structure and dynamics. However, the Plant usually is considered simply as an inert container, not as an interacting part of the food web. We used a response-surface and factorial field experiment to determine effects of nutrient enrichment (multiple levels of NH4NO3, PO4, and captured prey), top predator (removed or present), and the Plant itself (with or without plastic tubes inserted into the Pitchers to isolate the food web from the Plant) on the macrobial food web within the modified leaves ("Pitchers") of the carnivorous Pitcher Plant Sarracenia purpurea. Connection to the Plant, addition of NH4NO3 and removal of the top predator significantly increased the food web9s saturation, defined as its trophic depth and number of interactions. No effects on food-web saturation resulted from addition of PO4 or supplemental prey. Plants such as S. purpurea that create phytotelmata are more than inert containers and their inhabitants are more than commensal inquilines. Rather, both the Plant and the inquilines are partners in a complex network of interactions.
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regime shifts and hysteresis in the Pitcher Plant microecosystem
Ecological Modelling, 2018Co-Authors: Matthew K Lau, Nicholas J. Gotelli, Benjamin Baiser, Amanda C Northrop, Aaron M. EllisonAbstract:Abstract Changes in environmental conditions can lead to rapid shifts in the state of an ecosystem (“regime shifts”), which, even after the environment has returned to previous conditions, subsequently recovers slowly to the previous state (“hysteresis”). Large spatial and temporal scales of dynamics, and the lack of frameworks linking observations to models, are challenges to understanding and predicting ecosystem responses to perturbations. The naturally-occurring microecosystem inside leaves of the northern Pitcher Plant (Sarracenia purpurea) exhibits oligotrophic and eutrophic states that can be induced by adding insect prey. Here, we further develop a model for simulating these dynamics, parameterize it using data from a prey addition experiment and conduct a sensitivity analysis to identify critical zones within the parameter space. Simulations illustrate that the microecosystem model displays regime shifts and hysteresis. Parallel results were observed in the Plant itself after experimental enrichment with prey. Decomposition rate of prey was the main driver of system dynamics, including the time the system remains in an anoxic state and the rate of return to an oxygenated state. Biological oxygen demand influenced the shape of the system's return trajectory. The combination of simulated results, sensitivity analysis and use of empirical results to parameterize the model more precisely demonstrates that the Sarracenia microecosystem model displays behaviors qualitatively similar to models of larger ecological systems.
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regime shifts and hysteresis in the Pitcher Plant microecosystem
bioRxiv, 2018Co-Authors: Matthew K Lau, Nicholas J. Gotelli, Benjamin Baiser, Amanda C Northrop, Aaron M. EllisonAbstract:Changes in environmental conditions can lead to rapid shifts in ecosystem state ("regime shifts"), which subsequently returns slowly to the previous state ("hysteresis"). Large spatial and temporal scales of dynamics, and the lack of frameworks linking observations to models, are challenges to understanding and predicting ecosystem responses to perturbations. The naturally-occurring microecosystem inside leaves of the northern Pitcher Plant ( Sarracenia purpurea ) exhibits oligotrophic and eutrophic states that can be induced by adding insect "prey." Here, we further develop a model for simulating these dynamics, parameterize it using data from a prey addition experiment and conduct a sensitivity analysis to identify critical zones within the parameter space. Simulations illustrate that the microecosystem model displays regime shifts and hysteresis. Parallel results were observed in the Plant itself after experimental enrichment with prey. Decomposition rate of prey was the main driver of system dynamics, including the time the system remains in an anoxic state and the rate of return to an oxygenated state. Biological oxygen demand influenced the shape of the system9s return trajectory. The combination of simulated results, sensitivity analysis and use of empirical results to parameterize the model more precisely demonstrates that the Sarracenia microecosystem model displays behaviors qualitatively similar to models of larger ecological systems.
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proteomic characterization of the major arthropod associates of the carnivorous Pitcher Plant sarracenia purpurea
Proteomics, 2011Co-Authors: Nicholas J. Gotelli, Aidan M Smith, Aaron M. Ellison, Bryan A BallifAbstract:The array of biomolecules generated by a functioning ecosystem represents both a potential resource for sustainable harvest and a potential indicator of ecosystem health and function. The cupped leaves of the carnivorous Pitcher Plant, Sarracenia purpurea, harbor a dynamic food web of aquatic invertebrates in a fully functional miniature ecosystem. The energetic base of this food web consists of insect prey, which is shredded by aquatic invertebrates and decomposed by microbes. Biomolecules and metabolites produced by this food web are actively exchanged with the photosynthesizing Plant. In this report, we provide the first proteomic characterization of the sacrophagid fly (Fletcherimyia fletcheri), the Pitcher Plant mosquito (Wyeomyia smithii), and the Pitcher-Plant midge (Metriocnemus knabi). These three arthropods act as predators, filter feeders, and shredders at distinct trophic levels within the S. purpurea food web. More than 50 proteins from each species were identified, ten of which were predominantly or uniquely found in one species. Furthermore, 19 peptides unique to one of the three species were identified using an assembled database of 100 metazoan myosin heavy chain orthologs. These molecular signatures may be useful in species monitoring within heterogeneous ecosystem biomass and may also serve as indicators of ecosystem state.
Bryan C. Carstens - One of the best experts on this subject based on the ideXlab platform.
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phylogeographic concordance factors quantify phylogeographic congruence among co distributed species in the sarracenia alata Pitcher Plant system
Evolution, 2016Co-Authors: Jordan D. Satler, Bryan C. CarstensAbstract:Comparative phylogeographic investigations have identified congruent phylogeographic breaks in co-distributed species in nearly every region of the world. The qualitative assessments of phylogeographic patterns traditionally used to identify such breaks, however, are limited because they rely on identifying monophyletic groups across species and do not account for coalescent stochasticity. Only long-standing phylogeographic breaks are likely to be obvious; many species could have had a concerted response to more recent landscape events, yet possess subtle signs of phylogeographic congruence because ancestral polymorphism has not completely sorted. Here, we introduce Phylogeographic Concordance Factors (PCFs), a novel method for quantifying phylogeographic congruence across species. We apply this method to the Sarracenia alata Pitcher Plant system, a carnivorous Plant with a diverse array of commensal organisms. We explore whether a group of ecologically associated arthropods have co-diversified with the host Pitcher Plant, and identify if there is a positive correlation between ecological interaction and PCFs. Results demonstrate that multiple arthropods share congruent phylogeographic breaks with S. alata, and provide evidence that the level of ecological association can be used to predict the degree of similarity in the phylogeographic pattern. This study outlines an approach for quantifying phylogeographic congruence, a central concept in biogeographic research.
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Biogeographic barriers drive co-diversification within associated eukaryotes of the Sarracenia alata Pitcher Plant system.
PeerJ, 2016Co-Authors: Jordan D. Satler, Amanda J. Zellmer, Bryan C. CarstensAbstract:Understanding if the members of an ecological community have co-diversified is a central concern of evolutionary biology, as co-diversification suggests prolonged association and possible coevolution. By sampling associated species from an ecosystem, researchers can better understand how abiotic and biotic factors influence diversification in a region. In particular, studies of co-distributed species that interact ecologically can allow us to disentangle the effect of how historical processes have helped shape community level structure and interactions. Here we investigate the Sarracenia alata Pitcher Plant system, an ecological community where many species from disparate taxonomic groups live inside the fluid-filled Pitcher leaves. Direct sequencing of the eukaryotes present in the Pitcher Plant fluid enables us to better understand how a host Plant can shape and contribute to the genetic structure of its associated inquilines, and to ask whether genetic variation in the taxa are structured in a similar manner to the host Plant. We used 454 amplicon-based metagenomics to demonstrate that the pattern of genetic diversity in many, but not all, of the eukaryotic community is similar to that of S. alata, providing evidence that associated eukaryotes share an evolutionary history with the host Pitcher Plant. Our work provides further evidence that a host Plant can influence the evolution of its associated commensals.
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conservation genetic inferences in the carnivorous Pitcher Plant sarracenia alata sarraceniaceae
Conservation Genetics, 2010Co-Authors: Margaret M. Koopman, Bryan C. CarstensAbstract:Conservation geneticists make inferences about their focal species from genetic data, and then use these inferences to inform conservation decisions. Since different biological processes can produce similar patterns of genetic diversity, we advocate an approach to data analysis that considers the full range of evolutionary forces and attempts to evaluate their relative contributions in an objective manner. Here we collect data from microsatellites and chloroplast loci and use these data to explore models of historical demography in the carnivorous Pitcher Plant, Sarracenia alata. Findings indicate that populations of S. alata exhibit high degrees of population genetic structure, likely caused by dispersal limitation, and that population sizes have decreased in western populations and increased in eastern populations. These results provide new insight to the management and conservation of Plants restricted to small, declining populations isolated in increasingly scarce and highly threatened habitat, including other rare and endangered species of Sarracenia.
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The Carnivorous Pale Pitcher Plant Harbors Diverse, Distinct, and Time-Dependent Bacterial Communities
Applied and environmental microbiology, 2010Co-Authors: Margaret M. Koopman, Danielle M. Fuselier, Sarah M. Hird, Bryan C. CarstensAbstract:The ability of American carnivorous Pitcher Plants (Sarracenia) to digest insect prey is facilitated by microbial associations. Knowledge of the details surrounding this interaction has been limited by our capability to characterize bacterial diversity in this system. To describe microbial diversity within and between Pitchers of one species, Sarracenia alata, and to explore how these communities change over time as Pitchers accumulate and digest insect prey, we collected and analyzed environmental sequence tag (454 pyrosequencing) and genomic fingerprint (automated ribosomal intergenic spacer analysis and terminal restriction fragment length polymorphism) data. Microbial richness associated with Pitcher Plant fluid is high; more than 1,000 unique phylogroups were identified across at least seven phyla and 50 families. We documented an increase in bacterial diversity and abundance with time and observed repeated changes in bacterial community composition. Pitchers from different Plants harbored significantly more similar bacterial communities at a given time point than communities coming from the same genetic host over time. The microbial communities in Pitcher Plant fluid also differ significantly from those present in the surrounding soil. These findings indicate that the bacteria associated with Pitcher Plant leaves are far from random assemblages and represent an important step toward understanding this unique Plant-microbe interaction.
Christina M. Holzapfel - One of the best experts on this subject based on the ideXlab platform.
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replicate phylogenies and post glacial range expansion of the Pitcher Plant mosquito wyeomyia smithii in north america
PLOS ONE, 2013Co-Authors: Clayton R Merz, William E. Bradshaw, Kevin J. Emerson, Julian M Catchen, Victor Hansonsmith, Christina M. HolzapfelAbstract:Herein we tested the repeatability of phylogenetic inference based on high throughput sequencing by increased taxon sampling using our previously published techniques in the Pitcher-Plant mosquito, Wyeomyia smithii in North America. We sampled 25 natural populations drawn from different localities nearby 21 previous collection localities and used these new data to construct a second, independent phylogeny, expressly to test the reproducibility of phylogenetic patterns. Comparison of trees between the two data sets based on both maximum parsimony and maximum likelihood with Bayesian posterior probabilities showed close correspondence in the grouping of the most southern populations into clear clades. However, discrepancies emerged, particularly in the middle of W. smithii's current range near the previous maximum extent of the Laurentide Ice Sheet, especially concerning the most recent common ancestor to mountain and northern populations. Combining all 46 populations from both studies into a single maximum parsimony tree and taking into account the post-glacial historical biogeography of associated flora provided an improved picture of W. smithii's range expansion in North America. In a more general sense, we propose that extensive taxon sampling, especially in areas of known geological disruption is key to a comprehensive approach to phylogenetics that leads to biologically meaningful phylogenetic inference.
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Evolution of photoperiodic time measurement is independent of the circadian clock in the Pitcher-Plant mosquito, Wyeomyia smithii
Journal of Comparative Physiology A, 2009Co-Authors: Kevin J. Emerson, William E. Bradshaw, Sabrina J. Dake, Christina M. HolzapfelAbstract:For over 70 years, researchers have debated whether the ability to use day length as a cue for the timing of seasonal events (photoperiodism) is related to the endogenous circadian clock that regulates the timing of daily events. Models of photoperiodism include two components: (1) a photoperiodic timer that measures the length of the day, and (2) a photoperiodic counter that elicits the downstream photoperiodic response after a threshold number of days has been counted. Herein, we show that there is no geographical pattern of genetic association between the expression of the circadian clock and the photoperiodic timer or counter. We conclude that the photoperiodic timer and counter have evolved independently of the circadian clock in the Pitcher-Plant mosquito Wyeomyia smithii and hence, the evolutionary modification of photoperiodism throughout the range of W. smithii has not been causally mediated by a corresponding evolution of the circadian clock.
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quantitative trait loci associated with photoperiodic response and stage of diapause in the Pitcher Plant mosquito wyeomyia smithii
Genetics, 2007Co-Authors: Derrick Mathias, William E. Bradshaw, Lucien Jacky, Christina M. HolzapfelAbstract:A wide variety of temperate animals rely on length of day (photoperiodism) to anticipate and prepare for changing seasons by regulating the timing of development, reproduction, dormancy, and migration. Although the molecular basis of circadian rhythms regulating daily activities is well defined, the molecular basis for the photoperiodic regulation of seasonal activities is largely unknown. We use geographic variation in the photoperiodic control of diapause in the Pitcher-Plant mosquito Wyeomyia smithii to create the first QTL map of photoperiodism in any animal. For critical photoperiod (CPP), we detect QTL that are unique, a QTL that is sex linked, QTL that overlap with QTL for stage of diapause (SOD), and a QTL that interacts epistatically with the circadian rhythm gene, timeless. Results presented here confirm earlier studies concluding that CPP is under directional selection over the climatic gradient of North America and that the evolution of CPP is genetically correlated with SOD. Despite epistasis between timeless and a QTL for CPP, timeless is not located within any detectable QTL, indicating that it plays an ancillary role in the evolution of photoperiodism in W. smithii. Finally, we highlight one region of the genome that includes loci contributing to CPP, SOD, and hormonal regulation of development.
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circadian rhythmicity and photoperiodism in the Pitcher Plant mosquito can the seasonal timer evolve independently of the circadian clock
The American Naturalist, 2006Co-Authors: William E. Bradshaw, Christina M. Holzapfel, D MathiasAbstract:Abstract: The two major rhythms of the biosphere are daily and seasonal; the two major adaptations to these rhythms are the circadian clock, mediating daily activities, and the photoperiodic timer, mediating seasonal activities. The mechanistic connection between the circadian clock and the photoperiodic timer remains unresolved. Herein, we show that the rhythmic developmental response to exotic light:dark cycles, usually used to infer a causal connection between the circadian clock and the photoperiodic timer, has evolved independently of the photoperiodic timer in the Pitcher‐Plant mosquito Wyeomyia smithii across the climatic gradient of eastern North America from Florida to Canada and from the coastal plain to the mountains. We conclude that the photoperiodic timing of seasonal events can evolve independently of the daily circadian clock.
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geographic and developmental variation in expression of the circadian rhythm gene timeless in the Pitcher Plant mosquito wyeomyia smithii
Journal of Insect Physiology, 2005Co-Authors: Derrick Mathias, William E. Bradshaw, Lucien Jacky, Christina M. HolzapfelAbstract:Expression of the circadian rhythmgene timeless was investigated in the Pitcher-Plant mosquito, Wyeomyia smithii (Coq.), and was found to vary with time of day, instar of diapause, and latitude of origin. The temporal pattern of timeless expression differed between the two diapausing instars and was significantly higher in southern (38–401N) than in northern (501N) populations, when diapausing instar was held constant. Expression of timeless is therefore both developmentally and evolutionarily variable. This result provides the first example of a latitudinal difference in the expression of timeless, suggesting that, along with evidence fromother insects, timeless has the potential to affect photoperiodic response and its adaptive evolution in temperate seasonal environments. r 2005 Elsevier Ltd. All rights reserved.
Nicholas J. Gotelli - One of the best experts on this subject based on the ideXlab platform.
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regulation by the Pitcher Plant sarracenia purpurea of the structure of its inquiline food web
American Midland Naturalist, 2021Co-Authors: Aaron M. Ellison, Leszek A Bledzki, Nicholas J. Gotelli, Jessica L. ButlerAbstract:Phytotelmata, the water-filled habitats in Pitcher Plants, bromeliad tanks, and tree-holes, host multitrophic food webs that are model experimental systems for studying food-web structure and dynamics. However, the Plant usually is considered simply as an inert container, not as an interacting part of the food web. We used a manipulative field experiment with a response-surface design to determine effects of nutrient enrichment (multiple levels of NH4NO3, PO4, and captured prey), top predator (removed or present), and the Plant itself (with or without plastic tubes inserted into the Pitchers to isolate the food web from the Plant) on the macrobial food web within the modified leaves ("Pitchers") of the carnivorous Pitcher Plant Sarracenia purpurea. Connection to the Plant, addition of NH4NO3 and removal of the top predator significantly increased the food web9s saturation, defined as its trophic depth and number of interactions. No effects on food-web saturation resulted from addition of PO4 or supplemental prey. Plants such as S. purpurea that create phytotelmata are more than inert containers and their inhabitants are more than commensal inquilines. Rather, both the Plant and the inquilines are partners in a complex network of interactions.
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regulation by the Pitcher Plant sarracenia purpurea of the structure of its inquiline food web
bioRxiv, 2020Co-Authors: Aaron M. Ellison, Leszek A Bledzki, Nicholas J. Gotelli, Jessica L. ButlerAbstract:Phytotelmata, the water-filled habitats in Pitcher Plants, bromeliad tanks, and tree-holes, host multitrophic food webs that are model experimental systems for studying food-web structure and dynamics. However, the Plant usually is considered simply as an inert container, not as an interacting part of the food web. We used a response-surface and factorial field experiment to determine effects of nutrient enrichment (multiple levels of NH4NO3, PO4, and captured prey), top predator (removed or present), and the Plant itself (with or without plastic tubes inserted into the Pitchers to isolate the food web from the Plant) on the macrobial food web within the modified leaves ("Pitchers") of the carnivorous Pitcher Plant Sarracenia purpurea. Connection to the Plant, addition of NH4NO3 and removal of the top predator significantly increased the food web9s saturation, defined as its trophic depth and number of interactions. No effects on food-web saturation resulted from addition of PO4 or supplemental prey. Plants such as S. purpurea that create phytotelmata are more than inert containers and their inhabitants are more than commensal inquilines. Rather, both the Plant and the inquilines are partners in a complex network of interactions.
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regime shifts and hysteresis in the Pitcher Plant microecosystem
Ecological Modelling, 2018Co-Authors: Matthew K Lau, Nicholas J. Gotelli, Benjamin Baiser, Amanda C Northrop, Aaron M. EllisonAbstract:Abstract Changes in environmental conditions can lead to rapid shifts in the state of an ecosystem (“regime shifts”), which, even after the environment has returned to previous conditions, subsequently recovers slowly to the previous state (“hysteresis”). Large spatial and temporal scales of dynamics, and the lack of frameworks linking observations to models, are challenges to understanding and predicting ecosystem responses to perturbations. The naturally-occurring microecosystem inside leaves of the northern Pitcher Plant (Sarracenia purpurea) exhibits oligotrophic and eutrophic states that can be induced by adding insect prey. Here, we further develop a model for simulating these dynamics, parameterize it using data from a prey addition experiment and conduct a sensitivity analysis to identify critical zones within the parameter space. Simulations illustrate that the microecosystem model displays regime shifts and hysteresis. Parallel results were observed in the Plant itself after experimental enrichment with prey. Decomposition rate of prey was the main driver of system dynamics, including the time the system remains in an anoxic state and the rate of return to an oxygenated state. Biological oxygen demand influenced the shape of the system's return trajectory. The combination of simulated results, sensitivity analysis and use of empirical results to parameterize the model more precisely demonstrates that the Sarracenia microecosystem model displays behaviors qualitatively similar to models of larger ecological systems.
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regime shifts and hysteresis in the Pitcher Plant microecosystem
bioRxiv, 2018Co-Authors: Matthew K Lau, Nicholas J. Gotelli, Benjamin Baiser, Amanda C Northrop, Aaron M. EllisonAbstract:Changes in environmental conditions can lead to rapid shifts in ecosystem state ("regime shifts"), which subsequently returns slowly to the previous state ("hysteresis"). Large spatial and temporal scales of dynamics, and the lack of frameworks linking observations to models, are challenges to understanding and predicting ecosystem responses to perturbations. The naturally-occurring microecosystem inside leaves of the northern Pitcher Plant ( Sarracenia purpurea ) exhibits oligotrophic and eutrophic states that can be induced by adding insect "prey." Here, we further develop a model for simulating these dynamics, parameterize it using data from a prey addition experiment and conduct a sensitivity analysis to identify critical zones within the parameter space. Simulations illustrate that the microecosystem model displays regime shifts and hysteresis. Parallel results were observed in the Plant itself after experimental enrichment with prey. Decomposition rate of prey was the main driver of system dynamics, including the time the system remains in an anoxic state and the rate of return to an oxygenated state. Biological oxygen demand influenced the shape of the system9s return trajectory. The combination of simulated results, sensitivity analysis and use of empirical results to parameterize the model more precisely demonstrates that the Sarracenia microecosystem model displays behaviors qualitatively similar to models of larger ecological systems.
-
proteomic characterization of the major arthropod associates of the carnivorous Pitcher Plant sarracenia purpurea
Proteomics, 2011Co-Authors: Nicholas J. Gotelli, Aidan M Smith, Aaron M. Ellison, Bryan A BallifAbstract:The array of biomolecules generated by a functioning ecosystem represents both a potential resource for sustainable harvest and a potential indicator of ecosystem health and function. The cupped leaves of the carnivorous Pitcher Plant, Sarracenia purpurea, harbor a dynamic food web of aquatic invertebrates in a fully functional miniature ecosystem. The energetic base of this food web consists of insect prey, which is shredded by aquatic invertebrates and decomposed by microbes. Biomolecules and metabolites produced by this food web are actively exchanged with the photosynthesizing Plant. In this report, we provide the first proteomic characterization of the sacrophagid fly (Fletcherimyia fletcheri), the Pitcher Plant mosquito (Wyeomyia smithii), and the Pitcher-Plant midge (Metriocnemus knabi). These three arthropods act as predators, filter feeders, and shredders at distinct trophic levels within the S. purpurea food web. More than 50 proteins from each species were identified, ten of which were predominantly or uniquely found in one species. Furthermore, 19 peptides unique to one of the three species were identified using an assembled database of 100 metazoan myosin heavy chain orthologs. These molecular signatures may be useful in species monitoring within heterogeneous ecosystem biomass and may also serve as indicators of ecosystem state.
William E. Bradshaw - One of the best experts on this subject based on the ideXlab platform.
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replicate phylogenies and post glacial range expansion of the Pitcher Plant mosquito wyeomyia smithii in north america
PLOS ONE, 2013Co-Authors: Clayton R Merz, William E. Bradshaw, Kevin J. Emerson, Julian M Catchen, Victor Hansonsmith, Christina M. HolzapfelAbstract:Herein we tested the repeatability of phylogenetic inference based on high throughput sequencing by increased taxon sampling using our previously published techniques in the Pitcher-Plant mosquito, Wyeomyia smithii in North America. We sampled 25 natural populations drawn from different localities nearby 21 previous collection localities and used these new data to construct a second, independent phylogeny, expressly to test the reproducibility of phylogenetic patterns. Comparison of trees between the two data sets based on both maximum parsimony and maximum likelihood with Bayesian posterior probabilities showed close correspondence in the grouping of the most southern populations into clear clades. However, discrepancies emerged, particularly in the middle of W. smithii's current range near the previous maximum extent of the Laurentide Ice Sheet, especially concerning the most recent common ancestor to mountain and northern populations. Combining all 46 populations from both studies into a single maximum parsimony tree and taking into account the post-glacial historical biogeography of associated flora provided an improved picture of W. smithii's range expansion in North America. In a more general sense, we propose that extensive taxon sampling, especially in areas of known geological disruption is key to a comprehensive approach to phylogenetics that leads to biologically meaningful phylogenetic inference.
-
Evolution of photoperiodic time measurement is independent of the circadian clock in the Pitcher-Plant mosquito, Wyeomyia smithii
Journal of Comparative Physiology A, 2009Co-Authors: Kevin J. Emerson, William E. Bradshaw, Sabrina J. Dake, Christina M. HolzapfelAbstract:For over 70 years, researchers have debated whether the ability to use day length as a cue for the timing of seasonal events (photoperiodism) is related to the endogenous circadian clock that regulates the timing of daily events. Models of photoperiodism include two components: (1) a photoperiodic timer that measures the length of the day, and (2) a photoperiodic counter that elicits the downstream photoperiodic response after a threshold number of days has been counted. Herein, we show that there is no geographical pattern of genetic association between the expression of the circadian clock and the photoperiodic timer or counter. We conclude that the photoperiodic timer and counter have evolved independently of the circadian clock in the Pitcher-Plant mosquito Wyeomyia smithii and hence, the evolutionary modification of photoperiodism throughout the range of W. smithii has not been causally mediated by a corresponding evolution of the circadian clock.
-
quantitative trait loci associated with photoperiodic response and stage of diapause in the Pitcher Plant mosquito wyeomyia smithii
Genetics, 2007Co-Authors: Derrick Mathias, William E. Bradshaw, Lucien Jacky, Christina M. HolzapfelAbstract:A wide variety of temperate animals rely on length of day (photoperiodism) to anticipate and prepare for changing seasons by regulating the timing of development, reproduction, dormancy, and migration. Although the molecular basis of circadian rhythms regulating daily activities is well defined, the molecular basis for the photoperiodic regulation of seasonal activities is largely unknown. We use geographic variation in the photoperiodic control of diapause in the Pitcher-Plant mosquito Wyeomyia smithii to create the first QTL map of photoperiodism in any animal. For critical photoperiod (CPP), we detect QTL that are unique, a QTL that is sex linked, QTL that overlap with QTL for stage of diapause (SOD), and a QTL that interacts epistatically with the circadian rhythm gene, timeless. Results presented here confirm earlier studies concluding that CPP is under directional selection over the climatic gradient of North America and that the evolution of CPP is genetically correlated with SOD. Despite epistasis between timeless and a QTL for CPP, timeless is not located within any detectable QTL, indicating that it plays an ancillary role in the evolution of photoperiodism in W. smithii. Finally, we highlight one region of the genome that includes loci contributing to CPP, SOD, and hormonal regulation of development.
-
circadian rhythmicity and photoperiodism in the Pitcher Plant mosquito can the seasonal timer evolve independently of the circadian clock
The American Naturalist, 2006Co-Authors: William E. Bradshaw, Christina M. Holzapfel, D MathiasAbstract:Abstract: The two major rhythms of the biosphere are daily and seasonal; the two major adaptations to these rhythms are the circadian clock, mediating daily activities, and the photoperiodic timer, mediating seasonal activities. The mechanistic connection between the circadian clock and the photoperiodic timer remains unresolved. Herein, we show that the rhythmic developmental response to exotic light:dark cycles, usually used to infer a causal connection between the circadian clock and the photoperiodic timer, has evolved independently of the photoperiodic timer in the Pitcher‐Plant mosquito Wyeomyia smithii across the climatic gradient of eastern North America from Florida to Canada and from the coastal plain to the mountains. We conclude that the photoperiodic timing of seasonal events can evolve independently of the daily circadian clock.
-
geographic and developmental variation in expression of the circadian rhythm gene timeless in the Pitcher Plant mosquito wyeomyia smithii
Journal of Insect Physiology, 2005Co-Authors: Derrick Mathias, William E. Bradshaw, Lucien Jacky, Christina M. HolzapfelAbstract:Expression of the circadian rhythmgene timeless was investigated in the Pitcher-Plant mosquito, Wyeomyia smithii (Coq.), and was found to vary with time of day, instar of diapause, and latitude of origin. The temporal pattern of timeless expression differed between the two diapausing instars and was significantly higher in southern (38–401N) than in northern (501N) populations, when diapausing instar was held constant. Expression of timeless is therefore both developmentally and evolutionarily variable. This result provides the first example of a latitudinal difference in the expression of timeless, suggesting that, along with evidence fromother insects, timeless has the potential to affect photoperiodic response and its adaptive evolution in temperate seasonal environments. r 2005 Elsevier Ltd. All rights reserved.