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Thomasomys princeps (Thomas, 1895) is a large, sigmodontine rat and a member of the "aureus" group of the highly diverse genus Thomasomys. This species is only known from the Cordillera Oriental, Colombia; however, based on a recent examination of specimens of Thomasomys from Venezuela, I report the first record of T. princeps from Venezuela, in the Páramo del Tamá near the Colombian border. This record extends the distributional range of the species by 360 km northeast, representing the northernmost record of the species and of the "aureus" group. [ABSTRACT FROM AUTHOR]

We used Cormack–Jolly–Seber capture–recapture analyses to investigate differences in monthly survival of the southeastern beach mouse (Peromyscus polionotus niveiventris) between sexes, between juveniles and adults, and effects due to the presence of transients that can bias survival estimates. We accounted for transients (e.g. nonresidents) by distinguishing survival for the initial month after an individuals’ 1st capture from monthly survival after the 1st recapture. Survival estimates for 1st captures and recaptures of females were 0.70 and 0.78, respectively. Survival estimates for 1st captures and recaptures of males were 0.74 and 0.80, respectively. Our results showed that a comparably small proportion of transients (females = 0.10; males = 0.08) can bias survival estimates. [ABSTRACT FROM AUTHOR]

Reintroducing native wildlife populations is a common conservation-management approach aimed at reducing the threat of extinction and restoring ecosystem function. Captive-born individuals are sometimes used in reintroductions, but the effectiveness of this strategy is poorly understood due to insufficient post-reintroduction monitoring and evaluation. Our objective was to evaluate the utility of using captive-born individuals of an endangered rodent, the Perdido Key beach mouse (Peromyscus polionotus trissyllepsis) to reestablish a population on the western end of Perdido Key at Gulf State Park, Alabama, from which it was extirpated in 1997. We released 48 captive-born mice in March 2010 and monitored the population through livetrapping across 8 sessions spanning 5 years. We evaluated temporal changes in microsatellite genetic diversity to determine whether mice born in the wild were derived from released mice. The number of mice declined by 73% to 13 individuals in the first 2 weeks after release but increased to an estimated 206 (95% confidence interval = 195-217) individuals after 5 years. Genetic monitoring demonstrated a slight decrease in diversity during the first 3 months but an increase by year 5. Admixture from a neighboring population was detected in year 2 and year 5, which corresponded to the largest increase in population size between trapping sessions. This change in abundance corresponded with a doubling of Ne/N signifying a possible role of admixture in population growth and resilience. This study demonstrates the feasibility of using captive-born beach mice to reestablish populations when wild populations are too small to serve as donors for a translocation. We could not, however, discern how gene flow from an expanding neighboring population affected growth or persistence of the reintroduced population. Our study emphasizes that in future reintroductions, genetics should be monitored together with demographic patterns, because cryptic gene flow could affect how we interpret reintroduction success. [ABSTRACT FROM AUTHOR]

Synoptic data and an understanding of helminth parasite diversity among diverse rodent assemblages across temperate latitudes of North America remain remarkably incomplete. Renewed attention to comprehensive survey and inventory to establish the structure of biodiverse faunas is essential in providing indicators and proxies for identifying the outcomes of accelerating change linked to climate warming and anthropogenic forcing. Subsequent to the description of Hymenolepis folkertsi in the oldfield mouse, Peromyscus polionotus, additional specimens of hymenolepidids were collected or discovered in archived museum repositories from multiple species of deer mice ( Peromyscus maniculatus, Peromyscus leucopus), the golden mouse ( Ochrotomys nuttalli), chipmunks ( Tamias striatus, Tamias amoenus), the 13-lined ground squirrel ( Ictidomys tridecemlineatus), and tree squirrels ( Sciurus carolinensis, Sciurus niger) from disjunct localities in the USA spanning southern Georgia, Virginia, Pennsylvania, Connecticut, the Upper Peninsula of Michigan, Wisconsin, and central Idaho. Specimens were largely consistent morphologically with the original description of H. folkertsi. Initial DNA sequence data, from a portion of the mitochondrial NADH dehydrogenase subunit 1, demonstrated intraspecific variation among three apparently geographically isolated populations attributed to H. folkertsi (uncorrected genetic distances of 2.7 % (Idaho and Michigan), 2.4 % (Virginia + Pennsylvania and Michigan), and 1.89 % (VA + PA and ID). Geography rather than host association explains the distribution and occurrence of H. folkertsi, and host colonization among deer mice, chipmunks, and other sciurids within regional sites is indicated. Genetic divergence revealed across localities for H. folkertsi suggests historically isolated populations, consistent with extended evolutionary and biogeographic trajectories among hymenolepidids and species of Peromyscus and Tamias in North America. Field inventory, that revealed these parasite populations, substantially alters our understanding of the distribution of diversity and provides insights about the nature of the complex relationships that serve to determine cestode faunas in rodents. [ABSTRACT FROM AUTHOR]

Wild rodents such as Peromyscus spp. are intermediate hosts for the zoonotic ascarid Baylisascaris procyonis (raccoon roundworm), and previous studies indicate Peromyscus leucopus (white-footed mouse) likely serves an important role in parasite ecology. Natural infections have been sporadically identified in a few Peromyscus spp., but no data are available on differences in susceptibility among the many other species. We compared survival and infection dynamics of B. procyonis in 4 species ( P. leucopus, Peromyscus maniculatus [deer mouse], Peromyscus californicus [California mouse], Peromyscus polionotus [Oldfield mouse]) from regions of varying habitat types as well as B. procyonis prevalence in raccoons. Six captive-bred mice of each species were inoculated per os with 1 of 3 biologically-relevant doses of embryonated B. procyonis eggs (∼10, ∼50, or ∼500). Animals were monitored twice daily for clinical signs and behavioral abnormalities and were euthanized at the onset of neurological signs or extensive (≥20%) weight loss, or at 45 days post-infection if no disease developed. Larvae were counted in the brain via microscopic examination and in skeletal muscle and visceral organs via artificial digestion. In the high-dose group, all but 1 mouse developed severe neurologic disease and were euthanized. In the medium-dose group, survival was variable and ranged from 33-85% across species. Little to no disease was observed in the low-dose group, although 1 P. maniculatus developed disease and was euthanized. Survival analysis reveals P. leucopus had a longer time until clinical disease onset versus the other species, which did not differ significantly from each other. Interestingly, larval recovery relative to dose was nearly identical across species and doses; however, larvae were differentially distributed in skeletal muscle, visceral organs, and brain among species. These data indicate that P. leucopus may be more resilient toward severe baylisascariasis compared to the other species and that even closely-related rodents may experience differential mortality. This variation in tolerance may have ecological implications for the different species as B. procyonis intermediate hosts, although more work is needed to put these experimental findings into context. [ABSTRACT FROM AUTHOR]

The Perdido Key beach mouse (Peromyscus polionotus trissyllepsis) is a critically endangered subspecies of the oldfield mouse. The captive population, currently maintained by 3 Florida zoos, is entirely derived from just 3 wild-caught ancestor mice. Necropsy and histopathology revealed chordoma of the vertebral column in 38 of 88 (43%) mice. The tumors were locally expansile and invasive masses of large physaliferous (vacuolated) cells with small, round, hyperchromatic nuclei, similar to the “classic” form of chordomas described in humans. Primary tumors rarely contained small amounts of bone and cartilaginous matrix, characteristic of the “chondroid” form. Neoplastic cells contained abundant granules positive by the periodic acid–Schiff reaction. Brachyury and cytokeratin AE1/AE3 were detected in neoplastic cells by immunohistochemistry, but uncoupling protein 1 was not identified. Primary tumors occurred along the entire vertebral column—cervical, 5 of 38 (13%); thoracic, 16 (42%); lumbar, 13 (34%); and sacral, 10 (26%)—and 10 (26%) mice had multiple primary masses. Metastases to the lungs were noted in 13 of the 38 (34%) mice. Mice diagnosed with chordomas postmortem ranged from 424 to 2170 days old, with a mean of 1399 days. The prevalence of chordoma was not significantly different between males (n = 23 of 50; 46%) and females (n = 15 of 38; 39%). [ABSTRACT FROM AUTHOR]

Habitat fragmentation can exacerbate the impacts on population persistence in species with rapid life histories and specialized habitat requirements. We investigated genetic structuring across the range of the federally endangered (USA) Perdido Key beach mouse (PKBM), Peromyscus polionotus trissyllepsis, using 16 microsatellite loci. Between 2010 and 2012 we sampled the three core habitat areas that are separated by 3-5 km of developed area. One location GSP was re-established in 2010 with a release of 48 captive bred mice. The other two parks had a reticulate recent history, including extirpations, translocations and, a recent (2009) natural re-colonization. Our objectives were to document the level of genetic drift associated with the post-release phase at GSP over a 2-year period, and to test the hypothesis that PKBM dispersal connectivity is restricted between the three parks. The three populations were significantly genetically differentiated in 2010 and 2012 (pairwise F ranged from 0.135 to 0.276). However, Bayesian clustering, assignment tests and hybridization analyses revealed inter-park dispersal and reproduction in 2012 that was absent in 2010. The detection of dispersal was an important step in understanding the regulation of connectivity in this fragmented system. We propose that a combination of recent apparent population increases across the island combined with the concurrent re-establishment of beachfront vegetated sand berms encouraged inter-park dispersal detected in 2012. These results provide important information for the future conservation of beach mice inhabiting northern Gulf of Mexico and Atlantic barrier islands in light of continued development pressure. [ABSTRACT FROM AUTHOR]

A previously unrecognized species of hymenolepidid cestode attributable to Hymenolepis is described based on specimens in Peromyscus polionotus, oldfield mouse, from Georgia near the southeastern coast of continental North America. Specimens of Hymenolepis folkertsi n. sp. differ from those attributed to most other species in the genus by having testes arranged in a triangle and a scolex with a prominent rostrum-like protrusion. The newly recognized species is further distinguished by the relative position and length of the cirrus sac, shape of seminal receptacle, and relative size of external seminal vesicle and seminal receptacle. Hymenolepidid cestodes have sporadically been reported among the highly diverse assemblage of Peromyscus which includes 56 distinct species in the Nearctic. Although the host genus has a great temporal duration and is endemic to the Nearctic, current evidence suggests that tapeworm faunal diversity reflects relatively recent assembly through bouts of host switching among other cricetid, murid, and geomyid rodents in sympatry. [ABSTRACT FROM AUTHOR]

The spatial configuration of habitat and the frequency of disturbances through time could have interacting effects on population viability. With this in mind, we assessed the rate of post-hurricane recovery and long term viability of the Alabama beach mouse ( Peromyscus polionotus ammobates ). We collected detection/nondetection data across the range of the Alabama beach mouse for four years subsequent to hurricanes Ivan and Katrina, and then fit a dynamic patch occupancy model to these data using hierarchical Bayesian methods. We converted remotely sensed data into habitat classes, and then mapped site survival probability over the entire range of the species. These estimates were then used to parameterize a spatially-explicit population viability analysis. Our occupancy modeling demonstrates that the probability of patch occupancy increased from 0.16 to 0.67, with occupancy in the surveyed patches approaching an asymptote by the third post-hurricane summer. The viability analysis suggests that extinction probability increases nonlinearly with monotonic increases in both habitat loss and hurricane frequency. Extinction risk is sensitive to the regularity of catastrophic hurricanes; consecutive hurricanes dramatically increase extinction risk, further suggesting that the effect of global climate change on hurricane regimes may have a large effect on the probability of long-term persistence. A mild interaction between habitat loss and hurricane frequency occurs when extinction probability is relatively low, but disappears as extinction probability increases. Our results indicate that extinction risk is a complex function of multiple interacting drivers. [ABSTRACT FROM AUTHOR]

Most animal species forage with risk from an ensemble of predators, wherein some predators are themselves prey to the others. A forager's behavior should reflect a synthesis of the effect of environmental conditions on both marginal prédation risk and rates of energy accumulation. Here, a forager's giving-up density [GUD] is analyzed for signs of these complex signals. Specifically, we hypothesized that temperature can reverse the effect of moonlight intensity on Alabama beach mouse (Peromyscus polionotus ammobates) GUD because changes in temperature change the ensemble of predators from homeothermic taxa with better vision than the mouse to ectothermic taxa with worse vision than the mouse. We fit several models to GUD measurements taken over a broad range of temperatures and nocturnal luminosities. We obtained strong information-theoretic support for a model that is consistent with our hypothesis of temperature-dependent reversal of the effect of nocturnal illumination on mouse GUD. Signals in GUDs can reveal complex effects of optimal foraging at multiple trophic levels, which is especially informative when direct measurement of taxonomic sources of prédation is not feasible. [ABSTRACT FROM AUTHOR]

Motivated by conservation concerns, we assessed whether Sigmodon hispidus (hispid cotton rat) affects the realized niche of Peromyscus polionotus ammobates (Alabama beach mouse). After experimentally removing S. hispidus and accounting for spatial autocorrelation in our data, we found weak evidence for an increase in habitat use by P. p. ammobates at locations previously occupied by S. hispidus. This pattern is consistent with a niche- constriction hypothesis, and was not observed on 2 control grids where removals were not conducted. our results suggest that removal of S. hispidus from habitat remnants immediately following catastrophic hurricanes ameliorates extinction risk of P. p. ammobates, but we also stress the inferential limitations of our data and the need for further investigation of competitive interactions between these species. [ABSTRACT FROM AUTHOR]

Landscape features that promote animal movement contribute to functional habitat connectivity. Factors that affect the use of landscape features, such as predation risk, may alter functional connectivity. We identify factors important to functional habitat connectivity by quantifying movement patterns of the Santa Rosa beach mouse ( Peromyscus polionotus leucocephalus) in relation to landscape features and by examining how ambient perceived predation risk, which is altered by moon phase, interacts with landscape features. We use track paths across the sand to relate the probability that beach mice cross gaps between vegetation patches to gap width, patch quality, landscape context and moon phase. Overall activity levels were lower during full versus new moon nights, demonstrating that beach mice respond negatively to moonlight. Gap crossing was more likely during new moon nights (25 % of gaps crossed vs. 7 % during full moon nights), and across narrower gaps (<8.38 m) that led to larger vegetation patches (>11.75 m). This study suggests that vegetation recovery is necessary for functional connectivity in post-hurricane landscapes commonly inhabited by beach mice and provides initial guidelines for restoring landscape connectivity. More broadly, this study highlights the importance of considering predation risk when quantifying landscape connectivity, as landscape features that facilitate connectivity when predation risk is low may be ineffective if predation risk increases over time or across space. [ABSTRACT FROM AUTHOR]

Relative to morphological traits, we know little about how genetics influence the evolution of complex behavioural differences in nature. It is unclear how the environment influences natural variation in heritable behaviour, and whether complex behavioural differences evolve through few genetic changes, each affecting many aspects of behaviour, or through the accumulation of several genetic changes that, when combined, give rise to behavioural complexity. Here we show that in nature, oldfield mice (Peromyscus polionotus) build complex burrows with long entrance and escape tunnels, and that burrow length is consistent across populations, although burrow depth varies with soil composition. This burrow architecture is in contrast with the small, simple burrows of its sister species, deer mice (P. maniculatus). When investigated under laboratory conditions, both species recapitulate their natural burrowing behaviour. Genetic crosses between the two species reveal that the derived burrows of oldfield mice are dominant and evolved through the addition of multiple genetic changes. In burrows built by first-generation backcross mice, entrance-tunnel length and the presence of an escape tunnel can be uncoupled, suggesting that these traits are modular. Quantitative trait locus analysis also indicates that tunnel length segregates as a complex trait, affected by at least three independent genetic regions, whereas the presence of an escape tunnel is associated with only a single locus. Together, these results suggest that complex behaviours-in this case, a classic 'extended phenotype'-can evolve through multiple genetic changes each affecting distinct behaviour modules. [ABSTRACT FROM AUTHOR]

Anthropogenic habitat loss is among the greatest threats to biodiversity. Populations undergoing fragmentation and loss of habitat are also threatened by erosion of genetic diversity. However, contemporary genetic diversity may be the legacy of natural processes acting prior to anthropogenic influences. Measurements of genetic diversity from contemporary and historical samples can evaluate the relative impact of natural and anthropogenic effects on its status. We investigated the genetic diversity of a threatened subspecies occupying Atlantic Coast barrier islands of Florida, Peromyscus polionotus niveiventris (southeastern beach mouse). To test for recent loss of genetic diversity, we compared cyt b data from museum samples (historical-prior to human impact) with contemporary samples throughout their range. Ten microsatellite loci were genotyped for samples from the contemporary range, to determine current population interconnectedness and structure. The results using cyt b data revealed no statistically significant loss of genetic diversity between historical and contemporary populations of P. p. niveiventris. Both nuclear and mitochondrial data support our conclusion that the observed capture and conservation of historical genetic diversity is explained by the large federally protected region of continuous habitat that remains with minimal human impact. Whereas, the two disjunct populations isolated by anthropogenic habitat destruction, exhibit significant losses of genetic diversity. Collectively, these findings offer a sound basis from which to formulate a conservation strategy to maintain the genetic diversity of P. p. niveiventris. Furthermore, our study underscores the importance of large expanses of continuous habitat within the geographic range of species to facilitate the maintenance of genetic integrity. [ABSTRACT FROM AUTHOR]

To understand how organisms adapt to novel habitats, which involves both demographic and selective events, we require knowledge of the evolutionary history of populations and also selected alleles. There are still few cases in which the precise mutations (and hence, defined alleles) that contribute to adaptive change have been identified in nature; one exception is the genetic basis of camouflaging pigmentation of oldfield mice ( Peromyscus polionotus) that have colonized the sandy dunes of Florida's Gulf Coast. To quantify the genomic impact of colonization as well as the signature of selection, we resequenced 5000 1.5-kb noncoding loci as well as a 160-kb genomic region surrounding the melanocortin-1 receptor ( Mc1r), a gene that contributes to pigmentation differences, in beach and mainland populations. Using a genome-wide phylogenetic approach, we recovered a single monophyletic group comprised of beach mice, consistent with a single colonization event of the Gulf Coast. We also found evidence of a severe founder event, estimated to have occurred less than 3000 years ago. In this demographic context, we show that all beach subspecies share a single derived light Mc1r allele, which was likely selected from standing genetic variation that originated in the mainland. Surprisingly, we were unable to identify a clear signature of selection in the Mc1r region, despite independent evidence that this locus contributes to adaptive coloration. Nonetheless, these data allow us to reconstruct and compare the evolutionary history of populations and alleles to better understand how adaptive evolution, following the colonization of a novel habitat, proceeds in nature. [ABSTRACT FROM AUTHOR]

Track tubes may help measure impacts of disturbances on small mammals by providing information about the magnitude and timing of fluctuations in relative abundance. We evaluated live-capture and track-tube data from 8 trapping grids to test the utility of track tubes for monitoring abundance of beach mice (Peromyscus polionotus) through time and for comparing relative abundance of beach mice among sites. When averaged across grid sites, track indexes and abundance estimates exhibited strong covariation through time. Associations between the track index and estimated abundance on different grids varied from strong to very poor depending on sample period. Associations between track indexes and abundance estimates were strong when mouse densities on all grids were relatively low, but they were weak during other sample periods when densities were highly variable among grids. This study points to the need to understand factors that influence the relationship between indexes from track tubes and mouse abundance before track tubes can be used to compare abundances among sites. [ABSTRACT FROM AUTHOR]

Food resources and predation play important roles in determining small mammal population dynamics. These factors also can interact as individuals under predation pressure make trade-offs between access to food resources and exposure to predators. Fires consume food sources and reduce cover, which increases exposure to predators. For species that occur in areas with frequent fire, it is instructive to consider how all of these factors interact to affect populations of interest. We examined how supplemental feeding, mammalian predator exclusion, and prescribed fire affected survival, abundance, and reproduction of cotton mice (Peromyscus gossypinus) and oldfield mice (P. polionotus) in a longleaf pine ecosystem. Burning and predator exclusion interacted to affect survival of cotton mice; survival was similar in predator exclosures and controls in nonburning periods and in controls following prescribed burns but increased in exclosures following burns. Rates of transitions to reproductive states (which for females includes lactation or gravidity and for males, descent of testes) decreased in burn years but increased with the combination of feeding and predator exclusion. Supplemental feeding increased abundances. Among oldfield mice, survival and abundance were greater in predator exclusion areas than in controls. Supplemental feeding and the interaction of feeding and predator exclusion also increased abundances. During peak breeding seasons during which burning occurred rates of transitions to reproductive states declined to such an extent that reproductive transition rates in these seasons were lower than during nonpeak breeding seasons. [ABSTRACT FROM AUTHOR]

The article presents information on the composite species distribution model which is considered better in oldfield mouse (Peromyscus polionotus) than the models produced by taking whole species as a single unit. There are high rates of omission errors in predicting geographic distribution of species by modeling as the relevant spatial variation in the distribution of a single species may be masked biologically.

Standard track tube designs are ineffective for long-term monitoring of beach mice (Peromyscus polionotus) largely because of blowing sand and rain in the coastal dune habitat. We developed a novel track tube design with the tube elevated, capped on one end, and covered on the other end with a short 90° elbow tube. We tested this tube design against 2 other designs (elevated and ground). Our elevated 90° elbow track tubes detected beach mouse tracks more often and they were disturbed less frequently than elevated or ground tubes. Elevated 90° elbow track tubes are a practical means for managers to conduct long-term monitoring of beach mouse populations. [ABSTRACT FROM AUTHOR]

Mice of the genus Peromyscus, including several endangered subspecies, occur throughout North America and have been important models for conservation research. We describe 526 primer pairs that amplify microsatellite DNA loci for Peromyscus maniculatus bairdii, 467 of which also amplify in Peromyscus polionotus subgriseus. For 12 of these loci, we report diversity data from a natural population. These markers will be an important resource for future genomic studies of Peromyscus evolution and mammalian conservation. [ABSTRACT FROM AUTHOR]

A major goal in evolutionary biology is to understand how and why populations differentiate, both genetically and phenotypically, as they invade a novel habitat. A classical example of adaptation is the pale colour of beach mice, relative to their dark mainland ancestors, which colonized the isolated sandy dunes and barrier islands on Florida's Gulf Coast. However, much less is known about differentiation among the Gulf Coast beach mice, which comprise five subspecies linearly arrayed on Florida's shoreline. Here, we test the role of selection in maintaining variation among these beach mouse subspecies at multiple levels—phenotype, genotype and the environments they inhabit. While all beach subspecies have light pelage, they differ significantly in colour pattern. These subspecies are also genetically distinct: pair-wise FST-values range from 0.23 to 0.63 and levels of gene flow are low. However, we did not find a correlation between phenotypic and genetic distance. Instead, we find a significant association between the average ‘lightness’ of each subspecies and the brightness of the substrate it inhabits: the two most genetically divergent subspecies occupy the most similar habitats and have converged on phenotype, whereas the most genetically similar subspecies occupy the most different environments and have divergent phenotypes. Moreover, allelic variation at the pigmentation gene, Mc1r, is statistically correlated with these colour differences but not with variation at other genetic loci. Together, these results suggest that natural selection for camouflage—via changes in Mc1r allele frequency—contributes to pigment differentiation among beach mouse subspecies. [ABSTRACT FROM AUTHOR]

Abstract: Debate about the relative merits of single-species management versus more comprehensive approaches has intensified in recent years. In east-central Florida, USA, land managers use prescribed burns and mechanical cutting to manage and restore scrub habitat to benefit the imperiled Florida Scrub-Jay (Aphelocoma coerulescens). However, these land-management techniques may affect non-target taxa, especially the threatened southeastern beach mouse (Peromyscus polionotus niveiventris). We evaluated the collateral effects of single-species land management by trapping P. p. niveiventris and other small rodents in eighteen land-management compartments at Cape Canaveral Air Force Station, Florida during 2004–2005. Compartments were managed using either prescribed burns (N =5), mechanical cutting (N =6), checkerboarding (cut and uncut lanes alternating and overlapping, followed by a prescribed burn, N =4) or left unburned and uncut for >50year (N =3). P. p. niveiventris was significantly more abundant in compartments managed with prescribed burns (mean±SE: 4.2±0.7 individuals/transect) than those managed with cutting alone (1.0±0.3) or not managed for >50y (0.2±0.1 individuals/transect). In contrast, the cotton mouse (Peromyscus gossypinus) tended to be more abundant in compartments managed with mechanical cutting alone (2.6±0.4 individuals/transect) compared to the other three management strategies (prescribed burns; 1.5±0.4; checkerboarding, 1.1±0.3; not managed, 1.6±0.4 individuals/transect) but these differences were not statistically significant. Abundances of P. p. niveiventris and Florida Scrub-Jay breeding groups were positively correlated (r =0.655), suggesting that both listed species benefit from similar management techniques. Thus, the mosaic of burned and cut patches used to improve habitat for the Florida Scrub-Jay also benefits an endemic, non-target species. Single-species management may benefit multiple species when restoration improves their shared habitat, which in this case is an endangered, fire-dependent ecosystem: Florida scrub. [Copyright &y& Elsevier]

The article discusses field research of oldfield mice or peromyscus polionotus to study adaptations they make to the environment. It notes evolutionary biologist Hopi Hoekstra and pigment genes she is researching to help explain the pale color of the beach-residing oldfield mice. Hoekstra's team also is researching the burrowing habits of the mice. It notes graduate and post-doctoral students Evan Kingsley and Catherine Linnen, respectively, and their studies of mouse tail length and light-colored deer mice. INSET: Melding Mammals and Molecules to Track Evolution.

Recent increases in hurricane activity along the Gulf of Mexico lend urgency to understanding storm impacts on beach mice (Peromyscus polionotus) that occupy dune systems along this coast in Florida and Alabama. We documented changes in occupancy patterns of the Santa Rosa beach mouse (P. p. leucocephalus) from Hurricane Ivan and examined predictors of habitat use before and after the hurricane. The hurricane removed 68% of frontal dune area occupied by beach mice and only 15% of scrub dune area. Occupancy of frontal dunes by beach mice dropped from 100% before to the hurricane to 60% after the hurricane. Occupancy of scrub habitat was lower than occupancy of frontal dune habitat before the hurricane (~75% occupancy) and did not change with the hurricane. Occupancy of frontal dunes after the hurricane was influenced by percent cover of woody vegetation, dune height, and distance to nearest occupied dune. Probability of occupancy of scrub habitat was positively correlated with individual dune area and amount of surrounding dune habitat before and after the hurricane. Our study supports recent efforts to define scrub dunes as Critical Habitat for beach mice and points to the importance of enhancing dune height and reducing dune isolation in coastal restoration programs. [ABSTRACT FROM AUTHOR]

The evolutionary history of most behaviours remains unknown. Here, we assay burrowing behaviour of seven species of deer mice in standardized environments to determine how burrowing evolved in this genus (Peromyscus). We found that several, but not all, species burrow even after many generations of captive breeding. Specifically, there were significant and repeatable differences in both the frequency of burrowing and burrow shape between species. Moreover, these observed species-specific behaviours resemble those reported in wild mice. These results suggest that there is probably a strong genetic component to burrowing in deer mice. We also generated a phylogeny for these seven species using characters from four mtDNA and two autosomal loci. Mapping burrowing behaviour onto this phylogeny suggests a sequence for how complex burrowing evolves: from small, simple burrows to long, multitunnel burrows with defined entrance and escape tunnels. In particular, the most ‘complex’ burrows of P. polionotus appear to be derived. These behavioural data, when examined in a phylogenetic context, show that even closely related species differ in their burrowing behaviours and that the most complex burrows probably evolved by the gradual accumulation of genetic change over time. [Copyright &y& Elsevier]

In the absence of detailed pedigree records, researchers have attempted to estimate individuals' levels of inbreeding using molecular markers, generally making use of heterozygosity measures based on microsatellite markers. Here we report and validate a method for estimating an individual's inbreeding coefficient, f, using amplified fragment length polymorphism (AFLP) markers. We use simulations to confirm that our measure scales appropriately with f when allele frequencies can be estimated from a subset of outbred individuals. We also present an approach for obtaining satisfactory estimates even in the absence of an independent set of known outbred individuals from which to estimate allele frequencies. We then test our method against empirical data from 179 wild and captive-bred old-field mice, Peromyscus polionotus subgriseus, comprising pedigree-based estimates of f, along with genetic data from 94 AFLP markers and 12 microsatellites. Inbreeding estimates based on both AFLP and microsatellite markers were found to correlate strongly with pedigree-based inbreeding coefficients. Owing to their ease of amplification in any species, AFLP markers may prove to be a valuable new tool for estimating f in natural populations and for examining correlations between heterozygosity and fitness.Heredity (2008) 100, 286–295; doi:10.1038/sj.hdy.6801075; published online 7 November 2007 [ABSTRACT FROM AUTHOR]

Naturally occurring variation within a small rodent species native to the southeastern USA, Peromyscus polionotus, has interested biologists for nearly a century. This species has contributed significantly to our understanding of geographical variation and has often been presented as an example of adaptive evolution. Much of the interest in this organism has been predicated on assumptions that the species is relatively young (< 300 000 bp) and that coastal populations have a very recent history (< 10 000 bp). To test these assumptions and the prevailing biogeographical hypothesis ( Recurrent Invasion), we examined nucleotide sequence data from the cytochrome b and D-loop mitochondrial regions (2449 bp) for 79 samples of P. polionotus collected across the Gulf Coast region of Florida and Alabama. Samples representing Peromyscus maniculatus bairdii, P. m. sonoriensis, P. m. pallescens, and P. keeni were used as outgroups. The degree of cytochrome b divergence (≈ 4.4%) between P. maniculatus and P. polionotus was higher than expected. Analyses consistently indicated that three distinct groups are represented within P. polionotus from the Gulf Coast region. Among these, coastal populations (beach mice) form a monophyletic group and apparently represent a substantially older group (≈ 200 000 year. separation) than previously recognized. Our results were counter to the core assumptions of the existing biogeographical model but were consistent with an alternative hypothesis ( Shore-line Tracking) which provides a more parsimonious explanation for the observed patterns. This research provides new insight into the evolutionary history of P. polionotus and highlights the importance of considering biogeographical history when evaluating extant patterns of natural variation. [ABSTRACT FROM AUTHOR]

We investigated genetic diversity within the southeastern beach mouse (SEBM-Peromyscus polionotus niveiventris) and also tested the hypothesis that the subspecies recognition of P.p. niveiventris, based on size and color differences, is congruent with this taxon representing a discrete evolutionary lineage. We used ten polymorphic microsatellite loci and mitochondrial cytochrome-b gene DNA sequences to investigate genetic diversity and population structure within the SEBM, and to determine the level of divergence between the SEBM and the nearest known inland subspecies of the oldfield mouse (Peromyscus polionotus rhoadsi). Moderate genetic distances were observed between the SEBM and the inland oldfield mouse based on microsatellite data, with FST values ranging from 0.11 to 0.22 between these taxa. Additionally, mitochondrial DNA haplotypes of the SEBM formed a distinct monophyletic group relative to haplotypes sampled from P. p. rhoadsi. Based on previous estimates of rates of mitochondrial DNA evolution in rodents, we inferred that Pleistocene sea-level fluctuations are likely responsible for the historical isolation of the SEBM lineage from mainland P. polionotus. Our data demonstrate the genetic distinctiveness of the SEBM, justifying the current subspecies designation for the SEBM and its continued protection under the United States Endangered Species Act. We classify the Cape Canaveral and Smyrna Dunes Park populations of SEBM as a single evolutionary significant unit. The two known extant allopatric populations of the SEBM showed some differentiation in microsatellite frequencies and were moderately reciprocally distinguishable based on assignment to distinct genetic clusters by a Bayesian admixture procedure. These results justify the classification of these two extant SEBM populations as distinct management units that should be independent targets of management and conservation attention. [ABSTRACT FROM AUTHOR]

We investigated causes of body mass loss associated with consecutive days of live trapping of old-field mice (Peromyscus polionotus) on four small mammal trapping grids in central Florida USA from Mar. 2003 to Dec. 2004. Body mass of P. polionotus declined when live trapped for two consecutive days. Mean mass losses were recorded in all seasons and were significantly different in spring and summer. Temperatures inside live traps were higher than ambient temperatures. Mean number of sunflower seeds ingested was not different between day one and day two of capture, and the total number of sunflower seeds consumed explained a small amount of the variation in body mass loss. Our results suggest that sunflower seeds are not a good source of water necessary to maintain a constant body mass in P. polionotus live trapped on consecutive days, and mass loss is influenced by a combination of seasonal temperature fluctuations and physiological condition of trapped individuals. [ABSTRACT FROM AUTHOR]

Despite recent discoveries of the specific contributions of genes to behavior, the molecular mechanisms mediating contributions of the environment are understudied. We demonstrate that the behavioral effects of estrogens on aggression are completely reversed by a discrete environmental signal, day length. Selective activation of either estrogen receptor α or β decreases aggression in long days and increases aggression in short days. In the bed nucleus of the stria terminalis, one of several nuclei in a neural circuit that controls aggression, estrogen-dependent gene expression is increased in long days but not in short days, suggesting that estrogens decrease aggression by driving estrogen-dependent gene expression. Estradiol injections increased aggression within 15 mm in short days but not in long days, suggesting that estrogens increase aggression in short days primarily via nongenomic pathways. These data demonstrate that the environment can dictate how hormones affect a complex behavior by altering the molecular pathways targeted by steroid receptors. [ABSTRACT FROM AUTHOR]

Genetic relatedness estimates and capture records were used to examine population ecology of endangered Alabama beach mice (Peromyscus polionotus ammobates). Because of their monogamous mating strategy, biparental natal care, and limited dispersal patterns, we hypothesized that beach mice form gamodemes with family groups representing the core units. Under this hypothesis, we predicted that groups of related individuals would utilize common habitat spaces and that nonrandom age or sex associations could occur. To test these predictions, livetrapping data from an 8-year study were used to examine demography and relatedness of mice involved in joint and single captures (4,683 capture events involving 1,404 individuals, of which 949 were genotyped using microsatellite data). Mice were observed in joint captures nonrandomly with respect to age and sex, implying that there are nonrandom spatial associations among beach mice. Specifically, adult females were captured more often than expected with adult males and subadults were involved in joint captures more often than expected. Subadults captured with adults were the most related cocaptures, which, along with parental assignment, provided evidence of familial clustering. Adult male-female cocaptures were among the least related pairings, suggesting that inbreeding avoidance may play a role in mate choice. [ABSTRACT FROM AUTHOR]

Crosses between two recently diverged rodent species of the genus Peromyscus result in dramatic parent-of-origin effects on growth and development. P. maniculatus females crossed with P. polionotus males yield growth-retarded conceptuses, whereas the reciprocal cross results in overgrowth and lethality. These hybrid effects are particularly pronounced in the placenta. We previously detected linkage to two regions of the genome involved in the overgrowth effects. One locus, termed Peal, is a paternally expressed autosomal locus mapping to a domain whose house mouse equivalent contains several clusters of imprinted genes. The other locus, termed Mexl, maps to a gene-poor region of the X chromosome. Here we use an advanced intercross line to verify and narrow the regions of linkage and identify candidate genes for Mexl and Peal. While we have previously shown that Mexl affects both pre-and postnatal growth, we show here that Peal affects only prenatal growth. Utilizing criteria such as mutant phenotypes and allelic expression, we identify the loci encoding the homeobox protein Esx1 and the zinc-finger protein Pw1/Peg3 as candidates. Both loci exhibit expression changes in the hybrids. [ABSTRACT FROM AUTHOR]

We isolated and characterized 60 novel microsatellite markers from the closely related oldfield mouse ( Peromyscus polionotus) and deer mouse ( Peromyscus maniculatus) for studies of conservation, ecological, quantitative and population genetics. We assessed all 60 markers in a wild population of Peromyscus polionotus rhoadsi ( N = 20) from central Florida and found an average of nine alleles per marker and an observed heterozygosity ( HO) of 0.66 (range = 0.00–1.00). These polymorphic markers contribute to the growing number of genomic resources for Peromyscus, an emerging model system for ecological and evolutionary research. [ABSTRACT FROM AUTHOR]

We examined how corridors and patch shape affect foraging by the oldfield mouse (Peromyscus polionotus) by deploying foraging trays and live traps in experimental landscapes with 3 different patch types: patches connected with a corridor, unconnected patches with projecting corridorlike portions ("winged" patches), and unconnected rectangular patches. Corridors did not lead to different levels of activity of P. polionotus among the 3 patch types. Rather, corridors influenced activity by changing patch shape: foraging in seed trays and total number of captures of P. polionotus tended to be greater at the patch center than at the patch edge, but only in connected and winged patches where corridors or wings increased the amount of patch edge relative to the amount of core habitat in the patch. P. polionotus avoided open microhabitats near the patch edge in winged and connected patches, but not open microhabitats near the patch interior, suggesting that predation risk caused shifts in foraging near edges in connected and winged patches. Foraging in corridors and wings was generally low, suggesting that both are high-risk habitats where predation risk is not ameliorated by proximity to vegetative cover. By changing patch shape, corridors caused changes in within-patch activity of P. polionotus, changing foraging patterns and potentially altering the dynamics of P. polionotus and the seeds they consume. [ABSTRACT FROM AUTHOR]

Body mass is commonly used as an indicator of habitat quality and body condition in small mammal populations. We examined the effects of consecutive days of livetrapping on body mass of 2 federally listed subspecies of beach mice on the eastern coast of Florida: the Anastasia Island beach mouse (Peromyscus polionotus phasma) and the southeastern beach mouse (P. p. niveiventris). Mean mass loss (approximately 0.5 g/recaptured day) was additive and occurred for Anastasia Island beach mice over 2 consecutive days and for southeastern beach mice over 3 consecutive days. Researchers should exercise caution when their trapping protocols call for consecutive nights of trapping. [ABSTRACT FROM AUTHOR]

Studies of a variety of taxa have almost universally shown an increase in survivorship between the first cohort of young reared by a female (or both parents) and subsequent litters. Here, we examine the effect of early experience with sibling pups during the subadult period on later maternal behaviour and reproductive success in oldfield mice. ‘Experienced’ females remained with their mothers through the rearing of a litter of siblings. ‘Inexperienced’ females were removed from their parents at 20 days of age and had no prior exposure to pups before they reproduced. Twenty-four experienced females and 24 inexperienced females (each a full sibling of an experienced female) were paired with noninbred, inexperienced males through the birth and rearing of three litters. Litter survival improved significantly with experience and increasing parity. Pairs with experienced females showed improved nest-building behaviour and averaged significantly more surviving pups than did pairs with inexperienced females. Inexperienced mates of experienced females showed improved nest building, as well, consistent with the results of previous studies showing that paternal care tends to match that of mates. Maternal body weight did not appear to influence reproductive performance. These findings support the contention that individuals may accrue significant fitness benefits by delaying their own reproduction and gaining experience. [Copyright &y& Elsevier]

Introduction of artificial light into wildlife habitat represents a rapidly expanding form of human encroachment, particularly in coastal systems. Light pollution alters the behavior of sea turtles during nesting; therefore, long-wavelength lights—low-pressure sodium vapor and bug lights—that minimize impacts on turtles are required for beach lighting in Florida (U.S.A.). We investigated the effects of these two kinds of lights on the foraging behavior of Santa Rosa beach mice (Peromyscus polionotus leucocephalus). We compared patch use and giving-up densities of mice for experimental food patches established along a gradient of artificial light in the field. Mice exploited fewer food patches near both types of artificial light than in areas with little light and harvested fewer seeds within patches near bug lights. Our results show that artificial light affects the behavior of terrestrial species in coastal areas and that light pollution deserves greater consideration in conservation planning. [ABSTRACT FROM AUTHOR]

We used foraging trays to compare how oldfield mice, Peromyscus polionotus, altered foraging in response to the presence of fire ants, Solenopsis invicta, and in the presence of direct (predator urine) and indirect (sheltered or exposed microhabitat, moonlight, and precipitation) indicators of predation risk. Foraging reductions elicited by S. invicta were greater than reductions in response to well-documented indicators of risk (i.show $132#e., moonlit nights) and the presence of predator urine. The presence of S. invicta always led to reduced foraging, but the overall impact of S. invicta was dependent upon microhabitat and precipitation. When S. invicta was not present, foraging was greater in sheltered microhabitats compared to exposed microhabitats. S. invicta made sheltered microhabitats equivalent to more risky exposed microhabitats, and this effect was especially pronounced on nights without precipitation. The effect of S. invicta suggests that interactions with S. invicta may entail a potentially heavy cost or that presence of S. invicta may represent a more reliable indicator of imminent competition or predation compared to indirect cues of risk and predator urine. The presence of S. invicta led to reduced foraging under situations when foraging activity would otherwise be greatest (i.show $132#e., under vegetative cover), potentially reducing habitat quality for P. polionotus and the distribution of seeds consumed by rodents. [ABSTRACT FROM AUTHOR]

We used foraging trays to determine whether oldfield mice, Peromyscus polionotus, altered foraging in response to direct cues of predation risk (urine of native and nonnative predators) and indirect cues of predation risk (foraging microhabitat, precipitation, and moon illumination). The proportion of seeds remaining in each tray (a measure of the giving-up density [GUD]) was used to measure risk perceived by mice. Mice did not alter their GUD when presented with cues of native predators (bobcats, Lynx rufus, and red foxes, Vulpes vulpes), recently introduced predators (coyotes, Canis latrans), nonnative predators (ocelots, Leopardus pardalis), a native herbivore (white-tailed deer, Odocoileus virginianus), or a water control. Rather, GUD was related to microhabitat: rodents removed more seeds from foraging trays sheltered beneath vegetative cover compared with exposed trays outside of cover. Rodents also removed more seeds during nights with precipitation and when moon illumination was low. Our results suggest that P. polionotus used indirect cues rather than direct cues to assess risk of vertebrate predation. Indirect cues may be more reliable than are direct scent cues for estimating risk from multiple vertebrate predators that present the most risk in open environments. [ABSTRACT FROM AUTHOR]

Long-term maintenance of captive populations followed by release of captive animals into the wild is one of many approaches to endangered species conservation. To assess captivity''s effects on behavior, a simulated predator was presented and response behaviors measured in oldfield mice, Peromyscus polionotus subgriseus. The animals tested were from four populations collected from Ocala National Forest, Florida, and held in captivity for varying numbers of generations: 35, 14, 2, and 0 (wild caught). Results show (1) that the more generations a population has been in captivity, the less likely an individual is to take cover after seeing a predator and (2) variance in predator-response behaviors increases with generations in captivity. These results point to two ways in which captivity can compromise animal behavior and, in turn, the success of reintroduction programs. First, because individuals from populations that have been in captivity for multiple generations seek refuge less often than their wild counterparts, they might experience increased mortality in the wild due to predation. Second, increased behavioral variance could translate into decreased survivorship upon reintroduction. Therefore, more individuals will need to be released to reach the targeted wild population size. [Copyright &y& Elsevier]

The measurement of fecal steroids provides an increasingly important noninvasive technique for assessing reproduction, environmental stress, and aggression in populations of captive and free-living animals. In this paper, we validated the corticosterone (CORT) 125I-radioimmunoassay (ICN Pharmaceuticals) for plasma and fecal samples in a small rodent species, the oldfield mouse (Peromyscus polionotus subgriseus). The biochemical validations indicated that the assays accurately measured CORT concentrations in the plasma and corticosteroid concentrations in the feces. Physiological validation demonstrated that: (1) blood samples collected within 3 min of disturbing an animal''s cage represented “baseline” CORT concentrations, and (2) fecal corticosteroid concentrations collected over a 24-h period closely tracked plasma CORT concentrations approximately 4 h earlier. These results demonstrate that the plasma CORT and fecal corticosteroid assays are sensitive enough to detect biologically meaningful alterations in corticosteroid concentrations in oldfield mice. [Copyright &y& Elsevier]

Long-term maintenance of captive populations and release of these animals into the wild is one approach to endangered species conservation. In this study, I used a traditional ethological technique, the open-field test, to assess captivity's effects on exploratory behavior, level of activity, and enclosure use in oldfield mice (Peromyscus polionotus subgriseus) upon introduction to a novel environment. The animals tested were from four populations collected from Ocala National Forest, Florida, and were held in captivity for varying numbers of generations: 35, 14, 2, and 0 (wild caught). The population 35 generations removed from the wild was behaviorally distinct from the other three populations. The mechanisms behind the differences are unclear. This study, however, is an example of how traditional behavioral methods can be applied to conservation problems. Whether captive populations are raised for lab studies or for captive breeding of endangered species, this study suggests that if they have been removed from the wild for more than 14 generations, they are likely to be significantly different from the wild counterparts of interest. [ABSTRACT FROM AUTHOR]

Presents a study which examined the dispersal and philopatric tendencies in Alabama beach mice. Information on peromyscus polionotus ammobates; Materials and methods; Results and discussion.

Despite the consensus that mate choice acts as a mechanism for selection of secondary sexual traits, the evolutionary forces affecting mate preferences themselves remain controversial. In this study, we first demonstrated selection acting directly on the mate preferences of monogamous male oldfield mice, Peromyscus polionotus rhoadsi. One group of male oldfield mice were allowed to express a social preference between two potential mates, and were subsequently paired with either their preferred or rejected female. Among these pairs, those containing preferred females produced more offspring than did those containing rejected females. We next demonstrated that this fitness advantage depended primarily on compatibility between the members of a mated pair. A second group of male oldfield mice were not allowed the opportunity to express a social preference between potential mates. Rather, these males were paired with females that had been either preferred or rejected by males in the first group. Among these pairs, those containing preferred females did not produce more offspring than those containing rejected females. In other words, individual mate preferences had fitness consequences only for those males that expressed them, demonstrating that these preferences were based primarily on compatibility between mates. [ABSTRACT FROM AUTHOR]

Crosses between the two North American rodent species Peromyscus polionotus (PO) and Peromyscus maniculatus (BW) yield parent-of-origin effects on both embryonic and placental growth. The two species are approximately the same size, but a female BW crossed with a male PO produces offspring that are smaller than either parent. In the reciprocal cross, the offspring are oversized and typically die before birth. Rare survivors are exclusively female, consistent with Haldane's rule, which states that in instances of hybrid sterility or inviability, the heterogametic sex tends to be more severely affected. To understand these sex- and parent-of-origin-specific patterns of overgrowth, we analysed reciprocal backcrosses. Our studies reveal that hybrid inviability is partially due to a maternally expressed X-linked PO locus and an imprinted paternally expressed autosomal BW locus. In addition, the hybrids display skewing of X-chromosome inactivation in favour of the expression of the BWX chromosome. The most severe overgrowth is accompanied by widespread relaxation of imprinting of mostly paternally expressed genes. Both genetic and epigenetic mechanisms underlie hybrid inviability in Peromyscus and hence have a role in the establishment and maintenance of reproductive isolation barriers in mammals. [ABSTRACT FROM AUTHOR]

Provides information on a study of the impact of inbreeding on reproductive success of adult females in a captive colony of oldfield mice (Peromyscus polionotus subgriseus and Peromyscus polionotus). Methodology and materials used to conduct the study; Results of the study; Discussion on the results.

Analyzes the color of pelage and substrate and patterns of crypsis for nine samples of Peromyscus polionotus representing variation found throughout the entire range of species. Positive correlation between the brightness of pelage and subsurface soil brightness among mainland locations; Predation as a selective force affecting color of pelage in oldfield mice.

Examines the effectiveness of natural selection in reducing the `genetic load' of deleterious alleles from three subspecies of Peromyscus polionotus during inbreeding. Information on inbreeding depression; Factors on which the effectiveness of selection in reducing inbreeding is dependent; In-depth look at the study; Results of the study.

Presents a hierarchical analysis of inbreeding depression in Peromyscus polionotus mice. Information on inbreeding; Cause of inbreeding depression; Materials and methods used in the analysis.