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Savannas depend on frequent, low-intensity fires that shape animal and plant communities. These fires alter animal populations, movement, and habitat use. Here, we report on how fires in a longleaf pine ( Pinus palustris ) savanna affected small mammal microhabitat use via changes in competition and predation. We monitored small mammal populations and vegetation subjected to biennial prescribed fires and compared microhabitat use of three small mammal populations [hispid cotton rats ( Sigmodon hispidus ), cotton mice ( Peromyscus gossypinus ) and oldfield mice ( Peromyscus polionotus )] in the presence and absence of mesocarnivores while accounting for changes in density and movement of each small mammal species. Densities of cotton rats varied greatly across years but were similar between predator exclosures and controls. However, frequency of use was greater in exclosures than in controls irrespective of vegetation characteristics, suggesting predation risk altered cotton rat microhabitat use. Conversely, higher relative abundance of cotton rats was associated with lower cotton mouse and oldfield mouse use, suggesting spatial separation in niche and indicating that cotton mice expand their realized niche following predation-induced declines of cotton rats associated with prescribed burn events. Our results contribute to a better understanding of pyrodiversity and how interspecific interactions can moderate effects of vegetation changes following prescribed fires.

Efforts to remove invasive species may benefit native species, but the effects can be complex and unpredictable. Thus, studies of invasive-species removal provide important information for guiding management and providing insight about variation in post-removal impacts within the community. Using southern pine-grassland ecosystems as a model system, we hypothesized that removal of the long-established red-imported fire ant (Solenopsis invicta, hereafter RIFA) would positively influence altricial Peromyscus species, due to increased survival of young in the nest and thus increased recruitment to the population, but would not impact semi-precocial hispid cotton rats (Sigmodon hispidus), which are mobile more quickly after birth and thus at less risk of depredation by RIFA. We compared small mammal populations on sites treated with a granular insecticide (Extinguish Plus) to remove RIFA in southwestern Georgia, United States, from April 2018 to December 2019. As expected, we detected no difference in cotton rat recruitment. However, contrary to our prediction, the same was true for cotton mice (Peromyscus gossypinus) and oldfield mice (Peromyscus polionotus). We found RIFA removal increased survival both of cotton rats and cotton mice, increasing average population rate of change (λ) on treated sites during the study period. In contrast, we observed lower survival of oldfield mice, with similar λ estimates on treated and untreated sites, but low sample sizes were problematic for this species. Our results show that removal of invasive species can have positive impacts for native species, but both the magnitude of RIFA effects on small mammals and mechanisms by which impacts occur are complex.

The negative impacts of invasive Burmese pythons ( Python bivittatus ) on mammal communities in mainland South Florida are well-documented. However, few studies have examined the ecological effects of Burmese pythons along their southern invasion front in the Florida Keys. The establishment of Burmese pythons in the Keys could be devastating for island mammal communities and their ecosystem functions. We leveraged long-term data from camera trap surveys of endangered Key Largo woodrats ( Neotoma floridana smalli ) and free-ranging cats ( Felis catus ), as well as publicly available datasets to create time-dependent occupancy and generalized linear models to explore potential changes in the mammal community associated with increasing prevalence of Burmese pythons on Key Largo. Top occupancy models indicated that detection probabilities of endangered Key Largo cotton mice ( Peromyscus gossypinus allapaticola ), Key Largo woodrats, and invasive black rats ( Rattus rattus ) all decreased since the establishment of Burmese pythons in 2016 on North Key Largo, but the detection probability of Virginia opossums ( Didelphis virginiana ) might have increased. Additionally, top models indicated that increasing python prevalence was associated with high local extinction probabilities for woodrats and black rats. Generalized linear models indicated raccoon ( Procyon lotor ) and opossum counts decreased locally over time in areas where pythons were present, despite no broad-scale changes in occupancy. These results reveal a complex dynamic wherein Burmese pythons are likely having a stronger effect on rodent communities over mesopredator communities in North Key Largo—presumably due to demographics of a relatively new established python population. This study indicates that the python invasion in Key Largo has started to have ecological impacts. While these findings are cause for concern, evidence does suggest python removals are mitigating effects on certain mammal populations.

The healthy herds hypothesis (HHH) suggests that predators decrease parasitism in their prey. Repeated tests of this hypothesis across a range of taxa and ecosystems have revealed significant variation in the effect of predators on parasites in prey. Differences in the response to predators (1) between prey taxa, (2) between seasons, and (3) before and after catastrophic disturbance are common in natural systems, but typically ignored in empirical tests of the HHH. We used a predator exclusion experiment to measure the effect of these heterogeneities on the tri-trophic interaction among predators, parasites and prey. We experimentally excluded mammalian predators from the habitats of hispid cotton rats (Sigmodon hispidus) and cotton mice (Peromyscus gossypinus) and measured the effect of exclusion on gastrointestinal parasites in these rodents. Our experiment spanned multiple seasons and before and after a prescribed burn. We found that the exclusion of the same predators had opposite effects on the parasites of small mammal prey species. Additionally, we found that the effect of mammal exclusion on parasitism differed before versus after fire disturbance. Finally, we saw that the effect of predator exclusion was highly dependent on prey capture season. Significant effects of exclusion emerged primarily in the fall and winter months. The presence of so many different effects in one relatively simple system suggests that predator effects on parasites in prey are highly context dependent.

Everglades virus (EVEV) is subtype II of the Venezuelan equine encephalitis virus (VEEV) complex (Togaviridae: Alphavirus), endemic to Florida, USA. EVEV belongs to a clade that includes both enzootic and epizootic/ epidemic VEEV subtypes. Like other enzootic VEEV subtypes, muroid rodents are important vertebrate hosts for EVEV and certain mosquitoes are important vectors. The hispid cotton rat Sigmodon hispidus and cotton mouse Peromyscus gossypinus are important EVEV hosts, based on natural infection (virus isolation and high seropositivity), host competence (experimental infections), and frequency of contact with the vector. The mosquito Culex (Melanoconion) cecedei is the only confirmed vector of EVEV based upon high natural infection rates, efficient vector competence, and frequent feeding upon muroid rodents. Human disease attributed to EVEV is considered rare. However, cases of meningitis and encephalitis are recorded from multiple sites, separated by 250 km or more. Phylogenetic analyses indicate that EVEV is evolving, possibly due to changes in the mammal community. Mutations in the EVEV genome are of concern, given that epidemic strains of VEEV (subtypes IAB and IC) are derived from enzootic subtype ID, the closest genetic relative of EVEV. Should epizootic mutations arise in EVEV, the abundance of Aedes taeniorhynchus and other epizootic VEEV vectors in southern Florida provides a conducive environment for widespread transmission. Other factors that will likely influence the distribution and frequency of EVEV transmission include the establishment of Culex panocossa in Florida, Everglades restoration, mammal community decline due to the Burmese python, land use alteration by humans, and climate change.

Sexual isolation, a reproductive barrier, can prevent interbreeding between diverging populations or species. Sexual isolation can have a clear genetic basis; however, it may also result from learned mate preferences that form via sexual imprinting. Here, we demonstrate that two sympatric species of mice—the white-footed mouse (Peromyscus leucopus) and its sister species, the cotton mouse (P. gossypinus)—hybridize only rarely in the wild despite co-occurrence in the same habitat and lack of any measurable intrinsic postzygotic barriers in laboratory crosses. We present evidence that strong conspecific mating preferences in each species result in significant sexual isolation. We find that these preferences are learned in at least one species: P. gossypinus sexually imprints on its parents, but in P. leucopus, additional factors influence mating preferences. Our study demonstrates that sexual imprinting contributes to reproductive isolation that reduces hybridization between otherwise interfertile species, supporting the role for learning in mammalian speciation.

In Louisiana, there is a lack of published reproductive information for the white-footed mouse (Peromyscus leucopus) and cotton mouse (Peromyscus gossypinus). We recorded reproductive data from the voucher tags of preserved P. leucopus (n = 652) and P. gossypinus (n = 1460) specimens captured in Louisiana, summarized monthly variation in reproductive activity, and compared our findings to those in other states throughout each species geographic range. The average number of embryos for females was 3.93 (SD = 0.87) for P. leucopus and 4.42 (SD = 1.30) for P. gossypinus. Average testis length for male P. leucopus was 10.78 mm (SD = 3.22 mm) (scrotal) and 6.63 mm (SD = 3.38 mm) (abdominal), whereas for P. gossypinus, average testis length was 13.50 mm (SD = 5.05 mm) (scrotal) and 11.31 mm (SD = 4.39 mm) (abdominal). Similar to other southern states, both species appear to be year-round breeders with reproductive evidence appearing in every month except August for P. leucopus and July for P. gossypinus.

Habitat occupancy models, designed to deal with non‐detection of a target species in occupied sites, have been expanded to allow for false‐positive detections when species are mistakenly detected in unoccupied sites. When a subset of the data are unambiguous detections, such occupancy models can produce reliable results. However, if not properly accounted for, heterogeneity in the rate of false‐positive detection between sites may bias estimates of habitat occupancy. We studied habitat occupancy of the southeastern beach mouse (Peromyscus polionotus niveiventris), a species along Florida's Atlantic coast that is threatened due to the reduction of its core range by over 79% since 1950. Southeastern beach mice were detected based on their footprints in track tubes, but because of co‐occurrence of the cotton mouse (Peromyscus gossypinus) with overlapping footprint size, we had to allow for possible false‐positive detections. Differences in the relative abundance of these two species between habitats may have resulted in heterogeneity in the false‐positive rate. By combining uncertain (track tube) and certain (live capture) detection methods, we were able to use covariates to account for heterogeneity in false‐positive detection rates between habitats. Southeastern beach mouse habitat occupancy was higher in coastal dune and strand habitat than in coastal scrub or interior scrub habitats. The rate of false‐positive detections was much higher in coastal scrub habitat than in coastal dune and strand habitat or interior scrub habitat, reinforcing the need for methods that accommodate heterogeneity in the rate of false positives to reduce bias in estimates of habitat occupancy. Using simulations, we show that heterogeneity in the false‐positive detection rate leads to bias in habitat occupancy estimates unless properly accounted for. We also discuss how differences in relative abundance between the target species and a confusing species can directly impact the heterogeneity of false‐positive detections.

A novel jeilongvirus was identified through next-generation sequencing in cell cultures inoculated with spleen and kidney extracts. The spleen and kidney were obtained from a Peromyscus gossypinus rodent (cotton mouse) found dead in the city of Gainesville, in North-Central Florida, USA. Jeilongviruses are paramyxoviruses of the subfamily Orthoparamyxovirinae that have been found in bats, cats, and rodents. We designated the virus we discovered as Gainesville rodent jeilong virus 1 (GRJV1). Preliminary results indicate that GRJV1 can complete its life cycle in various human, non-human primate, and rodent cell lines, suggesting that the virus has a generalist nature with the potential for a spillover event. The early detection of endemic viruses circulating within hosts in North-Central Florida can significantly enhance surveillance efforts, thereby bolstering our ability to monitor and respond to potential outbreaks effectively.

Speciation is facilitated by “magic traits,” where divergent natural selection on such traits also results in assortative mating. In animal populations, diet has the potential to act as a magic trait if populations diverge in consumed food that incidentally affects mating and therefore sexual isolation. While diet‐based assortative mating has been observed in the laboratory and in natural populations, the mechanisms causing positive diet‐based assortment remain largely unknown. Here, we experimentally created divergent diets in a sexually imprinting species of mouse, Peromyscus gossypinus (the cotton mouse), to test the hypothesis that sexual imprinting on diet could be a mechanism that generates rapid and significant sexual isolation. We provided breeding pairs with novel garlic‐ or orange‐flavored water and assessed whether their offspring, exposed to these flavors in utero and in the nest before weaning, later preferred mates that consumed the same flavored water as their parents. While males showed no preference, females preferred males of their parental diet, which is predicted to yield moderate sexual isolation. Thus, our experiment demonstrates the potential for sexual imprinting on dietary cues learned in utero and/or postnatally to facilitate reproductive isolation and potentially speciation. Open Research Badges This article has earned an Open Data Badge for making publicly available the digitally‐shareable data necessary to reproduce the reported results. The data is available at https://doi.org/10.5061/dryad.n1qq6v3. Females largely prefer mates fed on the same diet as their parents, suggesting that sexual imprinting on diet could lead to assortative mating and potentially act as a “magic trait.”