Project description:Eurasian lynx (Lynx lynx) have a wide distribution across Eurasia. The northern edge of this distribution is in Norway, where they reach up to 72 degrees north. We conducted a study of lynx space use in this region from 2007 to 2013 using GPS telemetry. The home range sizes averaged 2,606 (± 438 SE) km2 for males (n = 9 ranges) and 1,456 (± 179 SE) km2 for females (n = 24 ranges). These are the largest home ranges reported for any large felid, and indeed are only matched by polar bears, arctic living wolves, and grizzly bears among all the Carnivora. The habitat occupied was almost entirely treeless alpine tundra, with home ranges only containing from 20% to 25% of forest. These data have clear implications for the spatial planning of lynx management in the far north as the current management zones are located in unsuitable habitats and are not large enough to encompass individual lynx movements.
Project description:We present the first study that evaluates jaguar-puma interactions in the arid lands of northern Mexico, where jaguars have their northernmost breeding population and both predators are persecuted for livestock depredation. We tested whether jaguars are the dominant species in this unique ecosystem, where: (1) pumas outnumber jaguars, (2) pumas are better adapted to arid environments, and (3) jaguars and pumas are of similar size. We analyzed four years of data with two approaches; a two species conditional occupancy model and an activity patterns analysis. We used camera location and prey presence as covariates for jaguar and puma detection and presence probabilities. We also explored overlap in activities of predators and prey. Where both species were detected, peccary presence was positively correlated with both jaguar and puma presence, whereas in areas where jaguars were detected but pumas were not, deer presence explained the probability of jaguar presence. We found that both predators were more likely to co-occur together than to be found independently, and so we rejected the hypothesis that jaguars were the dominant species in our study area. Predators were mainly nocturnal and their activity patterns overlapped by 60%. Jaguar, as compared with puma, overlapped more with deer and calves; puma overlapped with calves more than with other prey, suggesting a preference. We believe exploring predator relationships at different scales may help elucidate mechanisms that regulate their coexistence.
Project description:We used data from eight years of camera trapping at Rancho El Aribabi, a cattle ranch and conservation property in northern Sonora, Mexico, to examine the ecology of the northern-most known breeding population of ocelots (Leopardus pardalis). Ocelots were found mostly in two discrete and disjunct areas: a riverine riparian canyon at just less than 1,000 masl elevation and along arroyos in an oak-mesquite savanna in the Sierra Azul at 1,266-1,406 masl. An ocelot was also detected at a site between those two areas, in an area of a Sonoran desertscrub-foothills thornscrub ecotone at 1,300 masl. At least 18 ocelots, both males and females, were detected during the 2007-2011 and 2014-2018 sampling periods. A female with a kitten was documented in 2011. No individual ocelots were photographed in both areas, which are separated by a minimum of 11.29 km, and no individuals were photographed in both time periods. In a binary logistic regression, key environmental variables predicting ocelot presence were, in order of importance, distance to a paved road, distance to human habitation, proximity to water, and an anthropogenic influences index that was dominated by cattle. Another analysis corroborated the finding regarding ocelot presence and cattle. Contrary to previous studies, ocelot presence was not tied to vegetation cover close to the ground. We present information about the types of habitats and sites ocelots used, short-term movements, daily and seasonal activity patterns, and behavior, including occurrence of different individuals at or near the same site over short periods of time. We discuss ocelot home range, density, and movements, but small sample sizes and study design problems limit the value of estimates derived from our work. Rancho El Aribabi is a private, conservation ranch for which the owners have made voluntary conservation commitments that provide habitat and protection for ocelots and other animals and plants. This northern-most known breeding population is a likely source of ocelots that are periodically detected in southeastern Arizona. Our results should help facilitate conservation of the ocelot in other semi-arid areas of northwestern Mexico and adjacent USA.
Project description:The geographic range of tick populations has expanded in Canada due to climate warming and the associated poleward range shifts of their vertebrate hosts. Abiotic factors, such as temperature, precipitation, and snow, are known to directly affect tick abundance. Yet, biotic factors, such as the abundance and diversity of mammal hosts, may also alter tick abundance and consequent tick-borne disease risk. Here, we incorporated host surveillance data with high-resolution environmental data to evaluate the combined impact of abiotic and biotic factors on questing Ixodes scapularis abundance in Ontario and Quebec, Canada. High-resolution abiotic factors were derived from remote sensing satellites and meteorological towers, while biotic factors related to mammal hosts were derived from active surveillance data that we collected in the field. Generalized additive models were used to determine the relative importance of abiotic and biotic factors on questing I. scapularis abundance. Combinations of abiotic and biotic factors were identified as important drivers of abundances of questing I. scapularis. Positive and negative linear relationships were found for questing I. scapularis abundance with monthly mean precipitation and accumulated snow, but no effect was found for the relative abundance of white-footed mice. Positive relationships were also identified between questing I. scapularis abundance with monthly mean precipitation and mammal species richness. Therefore, future studies that assess I. scapularis should incorporate host surveillance data with high-resolution environmental factors to determine the key drivers impacting the abundance and geographic spread of tick populations and tick-borne pathogens.
Project description:Under the current amphibian biodiversity crisis, common species provide an opportunity to measure population dynamics across a wide range of environmental conditions while examining the processes that determine abundance and structure geographical ranges. Studying species at their range limits also provides a window for understanding the dynamics expected in future environments under increasing climate change and human modification. We quantified patterns of seasonal activity, density and space use in the eastern red-backed salamander (Plethodon cinereus) near its southern range edge and compare the spatial ecology of this population to previous findings from the core of their range. This southern population shows the expected phenology of surface activity based on temperature limitations in warmer climates, yet maintains unexpectedly high densities and large home ranges during the active season. Our study suggests that ecological factors known to strongly affect amphibian populations (e.g. warm temperature and forest fragmentation) do not necessarily constrain this southern population. Our study highlights the utility of studying a common amphibian as a model system for investigating population processes in environments under strong selective pressure.
Project description:Background and aimsClimate change, including gradual changes and extreme weather events, is driving widespread species losses and range shifts. These climatic changes are felt acutely in intertidal ecosystems, where many organisms live close to their thermal limits and experience the extremes of both marine and terrestrial environments. A recent series of multiyear heatwaves in the northeast Pacific Ocean might have impacted species even towards their cooler, northern range edges. Among them, the high intertidal kelp Postelsia palmaeformis has traits that could make it particularly vulnerable to climate change, but it is critically understudied.MethodsIn 2021 and 2022, we replicated in situ and aerial P. palmaeformis surveys that were conducted originally in 2006 and 2007, in order to assess the state of northern populations following recent heatwaves. Changes in P. palmaeformis distribution, extent, density and morphometrics were assessed between these two time points over three spatial scales, ranging from 250 m grid cells across the entire 167 km study region, to within grid cells and the individual patch.Key resultsWe found evidence consistent with population stability at all three scales: P. palmaeformis remained present in all 250 m grid cells in the study region where it was previously found, and neither the extent within cells nor the patch density changed significantly between time points. However, there was evidence of slight distributional expansion, increased blade lengths and a shift to earlier reproductive timing.ConclusionsWe suggest that apparent long-term stability of P. palmaeformis might be attributable to thermal buffering near its northern range edge and from the wave-exposed coastlines it inhabits, which may have decreased the impacts of heatwaves. Our results highlight the importance of multiscale assessments when examining changes within species and populations, in addition to the importance of dispersal capability and local conditions in regulating the responses of species to climate change.
Project description:Background: Responses to hypoxia have been investigated in many species; however, comparative study between conspecific geographical populations in different altitude regions is rare, especially for invertebrates . The migratory locust, Locusta migratoria, is widely distributed both on high-altitude Tibetan Plateau (TP) and on low-altitude North China Plain (NP). TP locusts have inhabited Tibetan Plateau since Quaternary glaciations events and thus probably have evolved superior capacity to deal with hypoxia. Results: Here we compared the hypoxic responses of TP and NP locusts from morphological, behavioral and physiological perspectives. We found that TP locusts were more tolerant of extreme hypoxia than NP locusts, with a lower proportion exhibiting stupor, a faster recovery time, and higher respiration rates. We compared the transcriptional profiles of field TP and NP locusts and found that their differences were possibly attributed to a combination of multiple factors, e.g. oxygen, UV radiation, temperature and nutrition. To evaluate why TP locusts respond to extreme hypoxia differently from NP locusts, we subjected them to extreme hypoxia and compared their transcriptional responses. We found that the aerobic metabolism was more active in TP locusts than in NP locusts. RNAi disruption of PDHE1b, an entry gene from glycolysis to TCA cycle, increased the ratio of stupor in Tibetan locusts and decreased the ATP content of Tibetan locusts in hypoxia, confirming the significant importance of this metabolic branch for TP locusts to conquer hypoxia. Conclusions: Here we show that TP locusts are better tolerant of hypoxia than NP locusts and the better capacity to modulate primary metabolism in TP locusts contributes to their superior tolerance of hypoxia compared to NP locusts.
Project description:During range expansion, edge populations are expected to face increased genetic drift, which in turn can alter and potentially compromise adaptive dynamics, preventing the removal of deleterious mutations and slowing down adaptation. Here, we contrast populations of the European subspecies Arabidopsis lyrata ssp. petraea, which expanded its Northern range after the last glaciation. We document a sharp decline in effective population size in the range-edge population and observe that nonsynonymous variants segregate at higher frequencies. We detect a 4.9% excess of derived nonsynonymous variants per individual in the range-edge population, suggesting an increase of the genomic burden of deleterious mutations. Inference of the fitness effects of mutations and modeling of allele frequencies under the explicit demographic history of each population predicts a depletion of rare deleterious variants in the range-edge population, but an enrichment for fixed ones, consistent with the bottleneck effect. However, the demographic history of the range-edge population predicts a small net decrease in per-individual fitness. Consistent with this prediction, the range-edge population is not impaired in its growth and survival measured in a common garden experiment. We further observe that the allelic diversity at the self-incompatibility locus, which ensures strict outcrossing and evolves under negative frequency-dependent selection, has remained unchanged. Genomic footprints indicative of selective sweeps are broader in the Northern population but not less frequent. We conclude that the outcrossing species A. lyrata ssp. petraea shows a strong resilience to the effect of range expansion.
Project description:Background: Responses to hypoxia have been investigated in many species; however, comparative study between conspecific geographical populations in different altitude regions is rare, especially for invertebrates . The migratory locust, Locusta migratoria, is widely distributed both on high-altitude Tibetan Plateau (TP) and on low-altitude North China Plain (NP). TP locusts have inhabited Tibetan Plateau since Quaternary glaciations events and thus probably have evolved superior capacity to deal with hypoxia. Results: Here we compared the hypoxic responses of TP and NP locusts from morphological, behavioral and physiological perspectives. We found that TP locusts were more tolerant of extreme hypoxia than NP locusts, with a lower proportion exhibiting stupor, a faster recovery time, and higher respiration rates. We compared the transcriptional profiles of field TP and NP locusts and found that their differences were possibly attributed to a combination of multiple factors, e.g. oxygen, UV radiation, temperature and nutrition. To evaluate why TP locusts respond to extreme hypoxia differently from NP locusts, we subjected them to extreme hypoxia and compared their transcriptional responses. We found that the aerobic metabolism was more active in TP locusts than in NP locusts. RNAi disruption of PDHE1b, an entry gene from glycolysis to TCA cycle, increased the ratio of stupor in Tibetan locusts and decreased the ATP content of Tibetan locusts in hypoxia, confirming the significant importance of this metabolic branch for TP locusts to conquer hypoxia. Conclusions: Here we show that TP locusts are better tolerant of hypoxia than NP locusts and the better capacity to modulate primary metabolism in TP locusts contributes to their superior tolerance of hypoxia compared to NP locusts. FIELD POPULATION: TP locusts vs. NP locusts;direct comparison on 6 separate microarrays; each microarray compares one biological replicate; each biological replicate contains 10 individuals. LAB POPULATION: hypoxia-treated TP locusts vs TP locusts in normoxia; hypoxia-treated NP locusts vs NP locusts in normoxia; direct comparison on 6 separate microarrays; each microarray compares one biological replicate; each biological replicate contains 10 individuals.
Project description:Understanding the demographic drivers of range contractions is important for predicting species' responses to climate change; however, few studies have examined the effects of climate change on survival and recruitment across species' ranges. We show that climate change can drive trailing edge range contractions through the effects on apparent survival, and potentially recruitment, in a migratory songbird. We assessed the demographic drivers of trailing edge range contractions using a long-term demography dataset for the black-throated blue warbler (Setophaga caerulescens) collected across elevational climate gradients at the trailing edge and core of the breeding range. We used a Bayesian hierarchical model to estimate the effect of climate change on apparent survival and recruitment and to forecast population viability at study plots through 2040. The trailing edge population at the low-elevation plot became locally extinct by 2017. The local population at the mid-elevation plot at the trailing edge gradually declined and is predicted to become extirpated by 2040. Population declines were associated with warming temperatures at the mid-elevation plot, although results were more equivocal at the low-elevation plot where we had fewer years of data. Population density was stable or increasing at the range core, although warming temperatures are predicted to cause population declines by 2040 at the low-elevation plot. This result suggests that even populations within the geographic core of the range are vulnerable to climate change. The demographic drivers of local population declines varied between study plots, but warming temperatures were frequently associated with declining rates of population growth and apparent survival. Declining apparent survival in our study system is likely to be associated with increased adult emigration away from poor-quality habitats. Our results suggest that demographic responses to warming temperatures are complex and dependent on local conditions and geographic range position, but spatial variation in population declines is consistent with the climate-mediated range shift hypothesis. Local populations of black-throated blue warblers near the warm-edge range boundary at low latitudes and low elevations are likely to be the most vulnerable to climate change, potentially leading to local extirpation and range contractions.