Although theory suggests that hybrid zones can move or change structure over time, studies supported by direct empirical evidence for these changes are relatively limited. We present a spatiotemporal genetic study of a hybrid zone between Pseudacris nigrita and P. fouquettei across the Pearl River between Louisiana and Mississippi. This hybrid zone was initially characterized in 1980 as a narrow and steep “tension zone,” in which hybrid populations were inferior to parentals and were maintained through a balance between selection and dispersal. We reanalyzed historical tissue samples and compared them to samples of recently collected individuals using microsatellites. Clinal analyses indicate that the cline has not shifted in roughly 30 years but has widened significantly. Anthropogenic and natural changes may have affected selective pressure or dispersal, and our results suggest that the zone may no longer best be described as a tension zone. To the best of our knowledge, this study provides the first evidence of significant widening of a hybrid cline but stasis of its center. Continued empirical study of dynamic hybrid zones will provide insight into the forces shaping their structure and the evolutionary potential they possess for the elimination or generation of species.

Understanding the factors influencing recruitment in animal populations is an important objective of many research and conservation programmes. However, evaluating hypotheses is challenging because recruitment is the outcome of birth and survival processes that are difficult to directly observe. Capture–recapture is the most general framework for estimating recruitment in the presence of observation error, but existing methods ignore the underlying birth and survival processes, as well as age effects and spatial variation in vital rates. We present an individual‐based, spatio‐temporal model that can be fit to capture–recapture data to draw inferences on the birth and survival processes governing recruitment dynamics. The number, dates, and spatial distribution of births are modelled as outcomes of a point process, and survival is modelled using a failure time approach. Survival parameters can be modelled as functions of individuals traits and time‐varying, spatial covariates. Continuous‐ and discrete‐time formulations are possible. We demonstrate the model using 7 months of camera data collected on white‐tailed deer Odocoileus virginianus fawns in Big Cypress National Preserve. Spot patterns were used to individually identify 28 fawns, detected 1,454 times between December 1, 2015 and July 1, 2016. A total of 37 (95% CI: 30–49) fawns were born, of which 16 (95% CI: 10–23) survived 180 days to the recruitment age. Mean parturition date was February 14 (95% CI: February 6–February 22), much earlier than in more temperate parts of the species’ range, but coinciding with the dry season in southern Florida. We found little evidence that mortality rates decreased with age, but the estimate of the age effect was imprecise. In contrast, we found strong evidence that encounter rates were age‐specific and increased rapidly over the first month of life as fawns became more mobile. Our case study demonstrates the potential of this new model for advancing knowledge of spatial population dynamics by providing insights into the birth and juvenile survival processes that influence recruitment. Because the model can be applied to data from noninvasive survey methods such as camera trapping, it is possible to apply it at broad spatial scales to understand how environmental variables and predator communities influence recruitment.

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Large carnivore restoration programs are often promoted as capable of providing ecosystem services. However, these programs rarely measure effects of successful restoration on other economically and ecologically important species. In South Florida, while the endangered Florida panther Puma concolor coryi population has increased in recent years due to conservation efforts, the population of its main prey, the white‐tailed deer Odocoileus virginianus, has declined in some regions. The extent to which panther predation has affected deer populations has been difficult to assess because several other factors have changed during this period, including hydrology and hunting regulations. We collected known‐fate survival data on 241 GPS‐collared adult deer (156 females and 85 males) from 2015 to 2018 in the Florida Panther National Wildlife Refuge and the Big Cypress National Preserve in Florida, USA, to assess effects of panther predation on the deer population, while also evaluating the impacts of hunting and hydrology. Predation was the primary cause of death (110 of 134 mortalities), and 87% of predation events were attributed to panthers, a much greater rate than reported by studies conducted before the panther genetic restoration effort initiated in 1995. One deer was legally harvested, and two were likely killed by poachers. Increasing water depth decreased female survival but had little impact on male survival, and drowning was never a cause of mortality. Females had greater survival probability than males, except during fawning season. From 2015 to 2018, annual survival rates increased from 0.61 (0.52–0.70) to 0.86 (0.79–0.91) for females, and from 0.45 (95% CI: 0.33–0.58) to 0.79 (0.69–0.86) for males. Synthesis and applications. High predation rates, coupled with previous evidence of low recruitment of deer in South Florida, suggest that it will be challenging to meet society's competing demands for large predator restoration and sustainable deer harvest. Deer hunting in the area must remain tightly controlled, for now, if it is to be sustainable, and managers should seek to mitigate effects of high waters and improve deer habitat quality to increase deer population viability. Future work should closely monitor the deer population to assess if management actions can increase vital rates and abundance in the context of high predation rates.

In south Florida, white-tailed deer (Odocoileus virginianus) are the primary prey of the endangered Florida panther (Puma concolor coryi). Deer populations in some regions of south Florida have declined in recent years, and the role of fawn survival and recruitment in these declines is unknown. Determining known-fate survival of fawns is challenging, requires invasive and costly methods, and often has a limited geographic scope. We deployed 180 cameras throughout the Florida Panther National Wildlife Refuge and the Big Cypress National Preserve to understand how environmental variables influence fawn survival. We identified 271 fawns from 12,715 photographs in 2015 and 2016. We utilized a noninvasive sampling method coupled with a spatial capture-recapture model to estimate the number of fawns born, the spatial distribution of birth locations, and the number of fawns that survived to recruitment (180 days old) during two fawning seasons. We found strong evidence of temporal variation in survival, but little evidence of spatial variation. Within the 10,941-ha study area, we estimated that 305 (95% CI: 245-385) fawns were born in 2015 and 278 (212-381) fawns were born in 2016. In 2015, 36% (110) of the estimated 305 fawns survived to 180 days. However, in 2016, only 13% (36) of the estimated 278 fawns survived to 180 days. The large difference in recruitment between years was likely driven by record flooding in 2016. Our data suggest that extreme weather events, coupled with high adult mortality, likely contributed to recent deer population decline in south Florida through reduced fawn recruitment. Unlike studies of known-fate fawn survival that require labor-intensive and invasive capture of both adults and neonates, our approach relies exclusively on camera data, which makes it possible to conduct studies over broad spatiotemporal scales in challenging environments to illuminate the drivers of variation in juvenile survival.