The Experts below are selected from a list of 144 Experts worldwide ranked by ideXlab platform
Lee B. Kats - One of the best experts on this subject based on the ideXlab platform.
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Amphibian responses in the aftermath of extreme climate events.
Scientific reports, 2020Co-Authors: Gary M. Bucciarelli, Rodney L. Honeycutt, Robert N. Fisher, Morgan A. Clark, Katy S. Delaney, Seth P. D. Riley, H. Bradley Shaffer, Lee B. KatsAbstract:Climate change-induced extinctions are estimated to eliminate one in six known species by the end of the century. One major factor that will contribute to these extinctions is extreme climatic events. Here, we show the ecological impacts of recent record warm air temperatures and simultaneous peak drought conditions in California. From 2008–2016, the southern populations of a wide-ranging endemic amphibian (the California Newt, Taricha torosa) showed a 20% reduction to mean body condition and significant losses to variation in body condition linked with extreme climate deviations. However, body condition in northern populations remained relatively unaffected during this period. Range-wide population estimates of change to body condition under future climate change scenarios within the next 50 years suggest that northern populations will mirror the loss of body condition recently observed in southern populations. This change is predicated on latter 21st century climate deviations that resemble recent conditions in Southern California. Thus, the ecological consequences of climate change have already occurred across the warmer, drier regions of Southern California, and our results suggest that predicted climate vulnerable regions in the more mesic northern range likely will not provide climate refuge for numerous amphibian communities.
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The effect of Newt toxin on an invasive snail
Hydrobiologia, 2018Co-Authors: William M. Ota, Gary M. Bucciarelli, Braden Olsen, Lee B. KatsAbstract:Invasive species are well documented to impact native species where they are introduced. In the Santa Monica Mountains, a native species of amphibian, the California Newt ( Taricha torosa ) possesses a neurotoxin, tetrodotoxin (TTX) that is considered a chemical defense against predation but also appears to facilitate ecological processes and specifically affect freshwater macroinvertebrate behavior. A recently introduced invasive species, the New Zealand mud snail ( Potamopyrgus antipodarum ), is known to negatively affect ecosystems it invades and means to control its proliferation once introduced are limited. Given the ecological role of Newt neurotoxin, we hypothesized that TTX may impact P. antipodarum behavior and tested its effects upon snail movement in laboratory assays and in-stream experiments. When snails were exposed to ecologically realistic TTX concentrations and Newt chemical cues that contain TTX they moved significantly less and distance was significantly reduced relative to controls. In a natural stream, significantly more P. antipodarum moved out of areas exposed to Newt chemical cues relative to snails in the presence of native tree frog cues ( Pseudacris cadaverina ). Our results suggest that California Newts may help limit the spread of P. antipodarum in streams where T. torosa is both able to persist and possess adequate chemical defenses.
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Predicting the effects of manual crayfish removal on California Newt persistence in Santa Monica Mountain streams
Ecological Modelling, 2017Co-Authors: William R. Milligan, Lee B. Kats, Marjorie T. Jones, Timothy A. Lucas, Courtney L. DavisAbstract:Abstract We construct a hybrid, stage-structured mathematical model to study whether trapping of the invasive predatory crayfish Procambarus clarkii can prevent local extinctions of the California Newt ( Taricha torosa ), a species of special concern native to Santa Monica Mountain streams. Specifically, we numerically and analytically determine under what conditions trapping can drive the crayfish population size to zero. We observe the persistence or the time to extinction for Newt populations under corresponding trapping scenarios. No simulations allow for long-term coexistence of Newts and crayfish, although multiple scenarios delay Newt extinction by several years in the presence of crayfish. We predict that crayfish extinction and Newt persistence become more likely as the quantity of trapping resources, frequency of trapping implementation, and susceptibility of the crayfish population to trapping increases. We quantify the effectiveness of different crayfish trapping regimes at delaying the time until the Newt population goes extinct. Predictions made with our model inform restorative efforts and crayfish management.
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A discrete stage-structured model of California Newt population dynamics during a period of drought
Journal of theoretical biology, 2016Co-Authors: Marjorie T. Jones, Lee B. Kats, William R. Milligan, Thomas L. Vandergon, Rodney L. Honeycutt, Robert N. Fisher, Courtney L. Davis, Timothy A. LucasAbstract:We introduce a mathematical model for studying the population dynamics under drought of the California Newt (Taricha torosa), a species of special concern in the state of California. Since 2012, California has experienced a record-setting drought, and multiple studies predict drought conditions currently underway will persist and even increase in severity. Recent declines and local extinctions of California Newt populations in Santa Monica Mountain streams motivate our study of the impact of drought on Newt population sizes. Although Newts are terrestrial salamanders, they migrate to streams each spring to breed and lay eggs. Since egg and larval stages occur in water, a precipitation deficit due to drought conditions reduces the space for Newt egg-laying and the necessary habitat for larval development. To mathematically forecast Newt population dynamics, we develop a nonlinear system of discrete equations that includes demographic parameters such as survival rates for Newt life stages and egg production, which depend on habitat availability and rainfall. We estimate these demographic parameters using 15 years of stream survey data collected from Cold Creek in Los Angeles County, California, and our model captures the observed decline of the parameterized Cold Creek Newt population. Based upon data analysis, we predict how the number of available Newt egg-laying sites varies with annual precipitation. Our model allows us to make predictions about how the length and severity of drought can affect the likelihood of persistence and the time to critical endangerment of a local Newt population. We predict that sustained severe drought will critically endanger the Newt population but that the Newt population can rebound if a drought is sufficiently short.
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Effects of Newt chemical cues on the distribution and foraging behavior of stream macroinvertebrates
Hydrobiologia, 2015Co-Authors: Gary M. Bucciarelli, Lee B. KatsAbstract:Many amphibians possess noxious or toxic substances for self defense. These compounds have been characterized largely as chemical defenses, but may promote ecological and evolutionary processes. The California Newt, Taricha torosa , possesses a potent neurotoxin, tetrodotoxin (TTX), which serves as a chemical defense, chemical cue to conspecifics, and selection pressure that has selected for evolved resistance in a predator. However, the potential effects of TTX upon the broader community and on behavior, in general, have been overlooked. Field assays conducted during the Newt breeding season indicate that the macroinvertebrate community responds to adult Newt chemical cues by altering foraging behavior. In these assays, significantly fewer macroinvertebrates were found in experimental areas with enclosed Newts relative to enclosures with a non-predatory amphibian. Laboratory bioassays showed that dragonfly nymphs ( Anax junius ) reduced predatory behavior and moved less in the presence of adult Newt chemical cues. When exposed to TTX, nymph mean angular velocities were reduced four fold and mean velocity magnitude was reduced threefold relative to controls. Overall, these results support the hypothesis that chemical stimuli from predators, and TTX specifically, can shape species interactions at lower trophic levels and potentially affect community organization.
Courtney L. Davis - One of the best experts on this subject based on the ideXlab platform.
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Predicting the effects of manual crayfish removal on California Newt persistence in Santa Monica Mountain streams
Ecological Modelling, 2017Co-Authors: William R. Milligan, Lee B. Kats, Marjorie T. Jones, Timothy A. Lucas, Courtney L. DavisAbstract:Abstract We construct a hybrid, stage-structured mathematical model to study whether trapping of the invasive predatory crayfish Procambarus clarkii can prevent local extinctions of the California Newt ( Taricha torosa ), a species of special concern native to Santa Monica Mountain streams. Specifically, we numerically and analytically determine under what conditions trapping can drive the crayfish population size to zero. We observe the persistence or the time to extinction for Newt populations under corresponding trapping scenarios. No simulations allow for long-term coexistence of Newts and crayfish, although multiple scenarios delay Newt extinction by several years in the presence of crayfish. We predict that crayfish extinction and Newt persistence become more likely as the quantity of trapping resources, frequency of trapping implementation, and susceptibility of the crayfish population to trapping increases. We quantify the effectiveness of different crayfish trapping regimes at delaying the time until the Newt population goes extinct. Predictions made with our model inform restorative efforts and crayfish management.
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A discrete stage-structured model of California Newt population dynamics during a period of drought
Journal of theoretical biology, 2016Co-Authors: Marjorie T. Jones, Lee B. Kats, William R. Milligan, Thomas L. Vandergon, Rodney L. Honeycutt, Robert N. Fisher, Courtney L. Davis, Timothy A. LucasAbstract:We introduce a mathematical model for studying the population dynamics under drought of the California Newt (Taricha torosa), a species of special concern in the state of California. Since 2012, California has experienced a record-setting drought, and multiple studies predict drought conditions currently underway will persist and even increase in severity. Recent declines and local extinctions of California Newt populations in Santa Monica Mountain streams motivate our study of the impact of drought on Newt population sizes. Although Newts are terrestrial salamanders, they migrate to streams each spring to breed and lay eggs. Since egg and larval stages occur in water, a precipitation deficit due to drought conditions reduces the space for Newt egg-laying and the necessary habitat for larval development. To mathematically forecast Newt population dynamics, we develop a nonlinear system of discrete equations that includes demographic parameters such as survival rates for Newt life stages and egg production, which depend on habitat availability and rainfall. We estimate these demographic parameters using 15 years of stream survey data collected from Cold Creek in Los Angeles County, California, and our model captures the observed decline of the parameterized Cold Creek Newt population. Based upon data analysis, we predict how the number of available Newt egg-laying sites varies with annual precipitation. Our model allows us to make predictions about how the length and severity of drought can affect the likelihood of persistence and the time to critical endangerment of a local Newt population. We predict that sustained severe drought will critically endanger the Newt population but that the Newt population can rebound if a drought is sufficiently short.
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Discrete Models of Newt Population Declines Due to Severe Drought and Invasive Crayfish
2016Co-Authors: Courtney L. Davis, Timothy A. LucasAbstract:We introduce discrete mathematical models for studying the population dynamics of the California Newt (Taricha torosa), a species of special concern in California. Recent declines and local extinctions of native California Newt populations in Santa Monica Mountain (SMM) streams motivate our investigation of the impact of drought and invasive crayfish (Procambarus clarkii) on Newt population sizes. Multiple studies predict Californias severe drought conditions currently underway will persist and even increase in duration and severity. In addition, invasive crayfish have decimated native Newt reproduction in SMM streams. We construct two nonlinear systems of discrete equations that include demographic parameters such as survival rates for Newt life stages and egg production, which depend upon habitat availability and rainfall. We estimate these demographic parameters using 15 years of stream survey data collected from Cold Creek in the SMM. Our models capture the observed decline of the studied Newt population and replicate crayfish trapping data. The first model makes predictions about how the length and severity of drought can affect the likelihood of persistence and the time to critical endangerment of a Newt population. With our second model, we evaluate the persistence or the time to extinction for Newt populations under crayfish trapping regimes when varying the quantity of trapping resources, frequency of trapping implementation, and susceptibility of the crayfish population to trapping. Predictions made with both models inform restorative efforts and crayfish management.
Timothy A. Lucas - One of the best experts on this subject based on the ideXlab platform.
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Predicting the effects of manual crayfish removal on California Newt persistence in Santa Monica Mountain streams
Ecological Modelling, 2017Co-Authors: William R. Milligan, Lee B. Kats, Marjorie T. Jones, Timothy A. Lucas, Courtney L. DavisAbstract:Abstract We construct a hybrid, stage-structured mathematical model to study whether trapping of the invasive predatory crayfish Procambarus clarkii can prevent local extinctions of the California Newt ( Taricha torosa ), a species of special concern native to Santa Monica Mountain streams. Specifically, we numerically and analytically determine under what conditions trapping can drive the crayfish population size to zero. We observe the persistence or the time to extinction for Newt populations under corresponding trapping scenarios. No simulations allow for long-term coexistence of Newts and crayfish, although multiple scenarios delay Newt extinction by several years in the presence of crayfish. We predict that crayfish extinction and Newt persistence become more likely as the quantity of trapping resources, frequency of trapping implementation, and susceptibility of the crayfish population to trapping increases. We quantify the effectiveness of different crayfish trapping regimes at delaying the time until the Newt population goes extinct. Predictions made with our model inform restorative efforts and crayfish management.
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A discrete stage-structured model of California Newt population dynamics during a period of drought
Journal of theoretical biology, 2016Co-Authors: Marjorie T. Jones, Lee B. Kats, William R. Milligan, Thomas L. Vandergon, Rodney L. Honeycutt, Robert N. Fisher, Courtney L. Davis, Timothy A. LucasAbstract:We introduce a mathematical model for studying the population dynamics under drought of the California Newt (Taricha torosa), a species of special concern in the state of California. Since 2012, California has experienced a record-setting drought, and multiple studies predict drought conditions currently underway will persist and even increase in severity. Recent declines and local extinctions of California Newt populations in Santa Monica Mountain streams motivate our study of the impact of drought on Newt population sizes. Although Newts are terrestrial salamanders, they migrate to streams each spring to breed and lay eggs. Since egg and larval stages occur in water, a precipitation deficit due to drought conditions reduces the space for Newt egg-laying and the necessary habitat for larval development. To mathematically forecast Newt population dynamics, we develop a nonlinear system of discrete equations that includes demographic parameters such as survival rates for Newt life stages and egg production, which depend on habitat availability and rainfall. We estimate these demographic parameters using 15 years of stream survey data collected from Cold Creek in Los Angeles County, California, and our model captures the observed decline of the parameterized Cold Creek Newt population. Based upon data analysis, we predict how the number of available Newt egg-laying sites varies with annual precipitation. Our model allows us to make predictions about how the length and severity of drought can affect the likelihood of persistence and the time to critical endangerment of a local Newt population. We predict that sustained severe drought will critically endanger the Newt population but that the Newt population can rebound if a drought is sufficiently short.
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Discrete Models of Newt Population Declines Due to Severe Drought and Invasive Crayfish
2016Co-Authors: Courtney L. Davis, Timothy A. LucasAbstract:We introduce discrete mathematical models for studying the population dynamics of the California Newt (Taricha torosa), a species of special concern in California. Recent declines and local extinctions of native California Newt populations in Santa Monica Mountain (SMM) streams motivate our investigation of the impact of drought and invasive crayfish (Procambarus clarkii) on Newt population sizes. Multiple studies predict Californias severe drought conditions currently underway will persist and even increase in duration and severity. In addition, invasive crayfish have decimated native Newt reproduction in SMM streams. We construct two nonlinear systems of discrete equations that include demographic parameters such as survival rates for Newt life stages and egg production, which depend upon habitat availability and rainfall. We estimate these demographic parameters using 15 years of stream survey data collected from Cold Creek in the SMM. Our models capture the observed decline of the studied Newt population and replicate crayfish trapping data. The first model makes predictions about how the length and severity of drought can affect the likelihood of persistence and the time to critical endangerment of a Newt population. With our second model, we evaluate the persistence or the time to extinction for Newt populations under crayfish trapping regimes when varying the quantity of trapping resources, frequency of trapping implementation, and susceptibility of the crayfish population to trapping. Predictions made with both models inform restorative efforts and crayfish management.
Anming Tan - One of the best experts on this subject based on the ideXlab platform.
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lineage diversification on an evolving landscape phylogeography of the California Newt taricha torosa caudata salamandridae
Biological Journal of The Linnean Society, 2006Co-Authors: Shawn R. Kuchta, Anming TanAbstract:We used mitochondrial cytochrome b sequences (up to 778 bp) and starch gel electrophoresis (45 loci) to examine the phylogeographical history of 39 populations of the California Newt, Taricha torosa. Phylogenetic and population genetic methods were integrated to infer history at deep and shallow time depths. Using a molecular clock, the subspecies T. t. torosa and T. t. sierrae were estimated to have diverged 7–13 Mya. Within T. t. torosa, genetically differentiated groups were identified along coastal California, in southern California, and in the southern Sierra Nevada. The coastal group exhibited isolation by distance, but a lack of genetic variation north of present-day Monterey was indicative of a recent range expansion. In southern California, a disjunct population in central San Diego County was genetically diverged from coastal populations to the north (Nei’s genetic distance of 0.113). However, mtDNA and protein data were geographically discordant regarding the boundary between the coastal and southern Californian groups, and a biogeographical scenario was developed to account for this discordance. The southern Sierran clade of T. t. torosa was weakly diverged from coastal populations for mtDNA sequence variation, yet was strongly differentiated for allozyme variation (Nei’s genetic distance of 0.17–0.20). Populations of T. t. sierrae exhibited substantial population structure, and showed a steeper pattern of isolation by distance than did coastal populations of T. t. torosa. These results are interpreted in consideration of the known geomorphological history of California. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 89, 213–239.
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mtdna phylogeography of the California Newt taricha torosa caudata salamandridae
Molecular Phylogenetics and Evolution, 1995Co-Authors: Anming Tan, David B. WakeAbstract:Thirty-six individuals of the California Newt, Taricha torosa, representing 22 populations from throughout the range of the two currently recognized subspecies, torosa and sierrae, were examined for sequence variation in a segment (375 bp) of the mitochondrial (mt) cytochrome b gene. The maximum sequence divergence within T. torosa is about 9%. Phylogenetic analyses used the sister taxa T. rivularis and T. granulosa as outgroups. Eighteen haploid sequence types found in T. torosa were grouped by parsimony, maximum likelihood, and neighbor-joining analyses into five mitochondrial clusters: two in torosa (the northern and southern clusters) and three in sierrae (the northern, central, and southern clusters). The southern sierrae cluster apparently shared a most recent common ancestor with the northern torosa cluster. The approximate time of sequence divergence within the current species was calibrated using the known fossil record (0.8% divergence per million years or 0.01 maximum likelihood distance per million years). Phylogenetic implications of mtDNA sequence variation for evolution and biogeography of the T. torosa species complex are discussed.
William R. Milligan - One of the best experts on this subject based on the ideXlab platform.
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Predicting the effects of manual crayfish removal on California Newt persistence in Santa Monica Mountain streams
Ecological Modelling, 2017Co-Authors: William R. Milligan, Lee B. Kats, Marjorie T. Jones, Timothy A. Lucas, Courtney L. DavisAbstract:Abstract We construct a hybrid, stage-structured mathematical model to study whether trapping of the invasive predatory crayfish Procambarus clarkii can prevent local extinctions of the California Newt ( Taricha torosa ), a species of special concern native to Santa Monica Mountain streams. Specifically, we numerically and analytically determine under what conditions trapping can drive the crayfish population size to zero. We observe the persistence or the time to extinction for Newt populations under corresponding trapping scenarios. No simulations allow for long-term coexistence of Newts and crayfish, although multiple scenarios delay Newt extinction by several years in the presence of crayfish. We predict that crayfish extinction and Newt persistence become more likely as the quantity of trapping resources, frequency of trapping implementation, and susceptibility of the crayfish population to trapping increases. We quantify the effectiveness of different crayfish trapping regimes at delaying the time until the Newt population goes extinct. Predictions made with our model inform restorative efforts and crayfish management.
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A discrete stage-structured model of California Newt population dynamics during a period of drought
Journal of theoretical biology, 2016Co-Authors: Marjorie T. Jones, Lee B. Kats, William R. Milligan, Thomas L. Vandergon, Rodney L. Honeycutt, Robert N. Fisher, Courtney L. Davis, Timothy A. LucasAbstract:We introduce a mathematical model for studying the population dynamics under drought of the California Newt (Taricha torosa), a species of special concern in the state of California. Since 2012, California has experienced a record-setting drought, and multiple studies predict drought conditions currently underway will persist and even increase in severity. Recent declines and local extinctions of California Newt populations in Santa Monica Mountain streams motivate our study of the impact of drought on Newt population sizes. Although Newts are terrestrial salamanders, they migrate to streams each spring to breed and lay eggs. Since egg and larval stages occur in water, a precipitation deficit due to drought conditions reduces the space for Newt egg-laying and the necessary habitat for larval development. To mathematically forecast Newt population dynamics, we develop a nonlinear system of discrete equations that includes demographic parameters such as survival rates for Newt life stages and egg production, which depend on habitat availability and rainfall. We estimate these demographic parameters using 15 years of stream survey data collected from Cold Creek in Los Angeles County, California, and our model captures the observed decline of the parameterized Cold Creek Newt population. Based upon data analysis, we predict how the number of available Newt egg-laying sites varies with annual precipitation. Our model allows us to make predictions about how the length and severity of drought can affect the likelihood of persistence and the time to critical endangerment of a local Newt population. We predict that sustained severe drought will critically endanger the Newt population but that the Newt population can rebound if a drought is sufficiently short.
