Species Of Peromyscus Research Articles

Personality and behavioral syndromes in two Peromyscus species: presence, lack of state dependence, and lack of association with home range size

One common theme of adaptive hypotheses for the existence of stable individual differences in behavior (personality) or persistent correlations among behaviors (behavioral syndromes) is an association between intrinsic state (e.g., body size, mass, metabolism) and the behavioral traits of interest. Empiricists are tasked with assessing whether there is an association between intrinsic state and behavior, but the statistical methods to appropriately quantify the among-individual correlation between intrinsic state and behavior have only recently become widely known. We conducted a multiyear study in wild mice of two Peromyscus species (Peromyscus leucopus noveboracensis and Peromyscus maniculatus gracilis) to assess the existence of stable individual differences in four different behaviors (presence of animal personality, as assessed by quantifying repeatabilities) and one measure of intrinsic state (body mass), the degree of association between these four behaviors (presence of behavioral syndromes), and the association of these behavioral traits with body mass using multivariate methods that allowed us to estimate the within-individual (residual) component and the among-individual component. We used standardized behavioral tests to measure struggle time (time spent struggling when removed from the trap) and exploration time (time spent exploring a novel surface) and used open-field trials to measure whether or not an individual entered the open field plus the total time it spent active in the open field. In P. leucopus, we assessed whether coarse but quick methods of assessing animal personality (struggle or exploration time) correlate with behavior using more in-depth estimates obtained by open-field trials. Additionally, we tested the ecological relevance of our personality measures by assessing their association with home range size in P. leucopus. In both species, struggle time, exploration time, and body mass were significantly repeatable and there was a significant among-individual correlation between struggle time and exploration time. However, in both species, there was no evidence for an among-individual correlation between our measure of intrinsic state (body mass) and personality traits. In one species (P. leucopus), we found that individuals that spent more time struggling or exploring a novel surface were also more likely to emerge into an open field and spent more time being active in an open field, but these four behavioral measures were not associated with home range size. Our results suggest among-individual correlation among these different behaviors but no among-individual correlation between behavior and intrinsic state. Over the past 15 years, it has become clear that nonhuman animals exhibit “personalities”: some individuals consistently differ in their behavior, and there is limited flexibility in their behavior when they experience environmental change. Biologists have now been searching for why and how animal personalities exist and their ecological and evolutionary consequences. Some explanations have focused on how condition or “internal state” may cause variation in animal personalities. In this study, we show that two species of wild mice exhibit personalities and that their personality traits are associated with one another, in that mice that were less docile were also more active, exploratory, and bold. We then show that their personality traits were not linked with body mass, suggesting a lack of association between internal state and personality. Our results provide important insights into the causes of personality in nonhuman animals.

High-altitude rodents have abundant collaterals that protect against tissue injury after cerebral, coronary and peripheral artery occlusion

Collateral number/density varies widely in brain and other tissues among strains of Mus musculus mice due to differences in genetic background. Recent studies have shown that prolonged exposure to reduced atmospheric oxygen induces additional collaterals to form, suggesting that natural selection may favor increased collaterals in populations native to high-altitude. High-altitude guinea pigs (Cavia) and deer mice (Peromyscus) were compared with lowland species of Peromyscus, Mus and Rattus (9 species/strains examined). Collateral density, diameter and other morphometrics were measured in brain where, importantly, collateral abundance reflects that in other tissues of the same individual. Guinea pigs and high-altitude deer mice had a greater density of pial collaterals than lowlanders. Consistent with this, guinea pigs and highlander mice evidenced complete and 80% protection against stroke, respectively. They also sustained significantly less ischemia in heart and lower extremities after arterial occlusion. Vessels of the circle of Willis, including the communicating collateral arteries, also exhibited unique features in the highland species. Our findings support the hypothesis that species native to high-altitude have undergone genetic selection for abundant collaterals, suggesting that besides providing protection in obstructive disease, collaterals serve a physiological function to optimize oxygen delivery to meet oxygen demand when oxygen is limiting.

A new species of Sigmodontinae (Rodentia) from the late Hemphillian of central Mexico, and comments on the possible radiation of this group

The Sigmodontinae subfamily represents one of the most diverse groups of mammals in the world; this rodent group evolved in the open and arid ecosystems of the Miocene of North America and was the most successful legion of mammals in the Great American Biotic Interchange. Part of its diversification occurred in the Mexican Pliocene, in the Hemphillian-Blancan boundary, where Prosigmodon and Sigmodon species are very common. Recent molecular phylogenetic systematics research propose that Sigmodon is related to South American sigmodontines, while studies of classical morphometry in isolated molar teeth consider Prosigmodon as synonymy of Sigmodon, which modifies the biogeographic and chronostratigraphic interpretations of this group in America. In this paper, we describe a new species of Prosigmodon from the late Hemphillian (~4.89 Ma) of central Mexico based on jaws, maxillary, and complete isolated teeth. This is the most complete and austral record of the genus in North America. This species was compared with North American species of the Sigmodontinae and Neotominae subfamilies and we defined it as a new Prosigmodon species characterized by having a consistently present minute mesoloph in M1 and M2, in addition, there is an isolated metaconid from the protoconid in the m1 of young individuals. We performed a phylogenetic model focused on understanding the relationship between Prosigmodon (four species) and Sigmodon (eight species), where we included Baiomys (two species), Neotoma (two species), Peromyscus (two species), and Reithrodontomys (two species). Our results indicate that Prosigmodon is a monophyletic group if Sigmodon minor is included within the genus and P. chihuahuensis is excluded. The Mexican Prosigmodon species have more apomorphic characters with respect to S. minor and P. holocuspis. The species of Prosigmodon and Sigmodon are not closely related, Sigmodon is more related to the Neotoma species than the species of Baiomys, Prosigmodon, Reitrhodontomys, and Peromyscus. Based on the topology of our cladogram and the stratigraphic ranges of the species Sigmodontinae and Neotominae, we discuss that Baiomys, Prosigmodon, Reitrhodontomys, and Peromyscus probably diversified in the early Hemphillian, while Sigmodon and Neotoma did so during the late Pliocene.

Genomes, expression profiles, and diversity of mitochondria of the White-footed Deermouse Peromyscus leucopus, reservoir of Lyme disease and other zoonoses

The cricetine rodents Peromyscus leucopus and P. maniculatus are key reservoirs for several zoonotic diseases in North America. We determined the complete circular mitochondrial genome sequences of representatives of 3 different stock colonies of P. leucopus, one stock colony of P. maniculatus and two wild populations of P. leucopus. The genomes were syntenic with that of the murids Mus musculus and Rattus norvegicus. Phylogenetic analysis confirmed that these two Peromyscus species are sister taxa in a clade with P. polionotus and also uncovered a distinction between P. leucopus populations in the eastern and the central United States. In one P. leucopus lineage four extended regions of mitochondrial pseudogenes were identified in the nuclear genome. RNA-seq analysis revealed transcription of the entire genome and differences from controls in the expression profiles of mitochondrial genes in the blood, but not in liver or brain, of animals infected with the zoonotic pathogen Borrelia hermsii. PCR and sequencing of the D-loop of the mitochondrion identified 32 different haplotypes among 118 wild P. leucopus at a Connecticut field site. These findings help to further establish P. leucopus as a model organism for studies of emerging infectious diseases, ecology, and in other disciplines.

Pulsed resource availability changes dietary niche breadth and partitioning between generalist rodent consumers.

Identifying the mechanisms that structure niche breadth and overlap between species is important for determining how species interact and assessing their functional role in an ecosystem. Without manipulative experiments, assessing the role of foraging ecology and interspecific competition in structuring diet is challenging. Systems with regular pulses of resources act as a natural experiment to investigate the factors that influence the dietary niches of consumers. We used natural pulses of mast‐fruiting of American beech (Fagus grandifolia) to test whether optimal foraging or competition structure the dietary niche breadth and overlap between two congener rodent species (Peromyscus leucopus and P. maniculatus), both of which are generalist consumers. We reconstructed diets seasonally over a 2‐year period using stable isotope analysis (δ13C, δ15N) of hair and of potential dietary items and measured niche dynamics using standard ellipse area calculated within a Bayesian framework. Changes in niche breadth were generally consistent with predictions of optimal foraging theory, with both species consuming more beechnuts (a high‐quality food resource) and having a narrower niche breadth during masting seasons compared to nonmasting seasons when dietary niches expanded and more fungi (a low‐quality food source) were consumed. In contrast, changes in dietary niche overlap were consistent with competition theory, with higher diet overlap during masting seasons than during nonmasting seasons. Overall, dietary niche dynamics were closely tied to beech masting, underscoring that food availability influences competition. Diet plasticity and niche partitioning between the two Peromyscus species may reflect differences in foraging strategies, thereby reducing competition when food availability is low. Such dietary shifts may have important implications for changes in ecosystem function, including the dispersal of fungal spores.

Evolution of the rodent Trim5 cluster is marked by divergent paralogous expansions and independent acquisitions of TrimCyp fusions

Evolution of cellular innate immune genes in response to viral threats represents a rich area of study for understanding complex events that shape mammalian genomes. One of these genes, TRIM5, is a retroviral restriction factor that mediates a post-entry block to infection. Previous studies on the genomic cluster that contains TRIM5 identified different patterns of gene amplification and the independent birth of CypA gene fusions in various primate species. However, the evolution of Trim5 in the largest order of mammals, Rodentia, remains poorly characterized. Here, we present an expansive phylogenetic and genomic analysis of the Trim5 cluster in rodents. Our findings reveal substantial evolutionary changes including gene amplifications, rearrangements, loss and fusion. We describe the first independent evolution of TrimCyp fusion genes in rodents. We show that the TrimCyp gene found in some Peromyscus species was acquired about 2 million years ago. When ectopically expressed, the P. maniculatus TRIMCyp shows anti-retroviral activity that is reversed by cyclosporine, but it does not activate Nf-κB or AP-1 promoters, unlike the primate TRIMCyps. These results describe a complex pattern of differential gene amplification in the Trim5 cluster of rodents and identify the first functional TrimCyp fusion gene outside of primates and tree shrews.

A high methyl donor diet affects physiology and behavior in Peromyscus polionotus

Folic acid and other dietary methyl donors are widely supplemented due to their ability to prevent neural tube defects. Dietary methyl donors are also added to other consumables such as energy drinks due to energy-promoting attributes and other perceived benefits. However, there is mounting evidence that indicates developmental exposure to high levels of dietary methyl donors may have deleterious effects. We assessed whether behavior was affected in the social North American rodent species Peromyscus polionotus exposed to a diet enriched with folic acid, Vitamin B12, choline, and betaine/trimethylglycine(TMG). P. polionotus (PO) animals are very social and exhibit little repetitive behavior, particularly compared to their sister species, P. maniculatus. We assayed the effects of dietary methyl-donor supplementation on anxiety-like repetitive and social behaviors by testing young adult animals for novel cage behavior and in social interaction tests. Animals of both sexes exposed to the diet had increased repetitive behaviors and reduced social interactions. Males exposed to the diet became more aggressive compared to their control counterparts. Since methyl-diet animals were larger than control animals, DEXA scans and hormone analyses were performed. Animals exposed to the diet had increased body fat percentages and experienced hormonal changes typically associated with excess fat storage and anxiety-like behavior changes. Therefore, these data suggest the wide use of these dietary supplements makes further investigation imperative.

Distribution extension of Aspiculuris americana parasite of Peromyscus difficilis in Hidalgo, México

As a part of an ongoing project to inventory the helminth parasites of rodents in Mexico, 30 individuals of Aspiculuris americana were collected inhabiting the intestine from three specimens of the rock mouse Peromyscus difficilis, collected from Cerro Xihuingo, Municipality of Tepeapulco, Hidalgo State, Mexico. This species of nematode parasite different species of the genus Peromyscus (P. gossypinus, P. leucopus, P. maniculatus, and P. floridanus) distributed from Yukon Territory in Canada to Florida in the United States of America. This is the first report of Aspiculuris americana in a Mexican endemic rodent, widening the known distribution of the species to the southern portion of the country.

Differentiation pattern in the use of space by males and females of two species of small mammals (Peromyscus difficilis and P. melanotis) in a temperate forest

The distribution patterns of individuals together with mechanisms that maintain them have significant implications for population-level processes. Sex-specific differences in home-range may strongly influence the spatial distribution of individuals, while the differential use of space by the sexes can yield insights into the mating system and the life history of the species. Sexual differences in the use of space could be due to different habitat requirements during the breeding season. This is interesting because the males and females likely are interacting with operational sex ratios and mating strategies. Here, we evaluated for ten months of the year 2014, the spatial patterns of ecological distribution in males and females of two species of deer mice ( Peromyscus difficilis and P. melanotis ) that coexist in a temperate forest. Also, we assessed the variation in the use of space by males and females in both Peromyscus species and we analyze the intensity of positive association or repulsion between males and females. During drought and rain seasons, males and females of both Peromyscus were captured. The sex and reproductive status of each were identified. To analyze the spatial patterns of ecological distribution, we used the Nearest Neighbor Analysis. Kernel spatial analysis was performed to evaluate the variation in the use of space of males and females between seasons. The Ripley’s K bivariate function was carried out to assess the positive association or repulsion between males and females in each season. We found a different use of space between sexes. Our evidence shed light on the respective life histories of these species and provides information on possible factors that they may be using to coexist successfully among them. We conclude that in this temperate coniferous forest: 1) use of space by P. difficilis and P. melanotis , is influenced by both sex and by the reproductive season, and that this pattern varies, according to shifts on ecological conditions that promote variation and availability of resources during the two pluvial seasons; 2) there are interspecific differences in the use of space with conspicuous intraspecific differences in females and males of P. difficilis ( e. g. , males are more territorial, and both sexes only become more clustered during the breeding season), while both sexes of P. melanotis are more gregarious; and 3) there is a clear differentiation in the reproductive seasons of both species that could be related to resources availability, such as shelters and food.

The Role of Mammalian Reservoir Hosts in Tick-Borne Flavivirus Biology

Small-to-medium sized mammals and large animals are lucrative sources of blood meals for ixodid ticks that transmit life-threatening tick-borne flaviviruses (TBFVs). TBFVs have been isolated from various organs obtained from wild-caught Myodes and Apodemus species in Europe and Asia. Thus, these rodents are well-established reservoirs of TBFVs. Wild-caught Peromyscus species have demonstrated seropositivity against Powassan virus, the only TBFV known to circulate in North America, suggesting that they may play an important role in the biology of the virus in this geographic region. However, virus isolation from Peromyscus species is yet to be demonstrated. Wild-caught medium-sized mammals, such as woodchucks (Marmota monax) and skunks (Mephitis mephitis) have also demonstrated seropositivity against POWV, and virus was isolated from apparently healthy animals. Despite the well-established knowledge that small-to-medium sized animals are TBFV reservoirs, specific molecular biology addressing host-pathogen interactions remains poorly understood. Elucidating these interactions will be critical for gaining insight into the mechanism(s) of viral pathogenesis and/or resistance.

Genetic patterns in fragmented habitats: a case study for two Peromyscus species in southern California

Genetic patterns in fragmented habitats: a case study for two Peromyscus species in southern California

Comparative studies need to rely both on sound natural history data and on excellent statistical analysis.

We certainly agree with Schradin [1] that comparative studies need to use the best information available—as well as clear definitions, up-to-date statistical techniques and common sense. We have divided our response into two sections: the first dealing with Schradin's critique of our 2017 paper and the classification of the social organization of shrews; the second dealing with three general issues that his commentary raises. The paper that Schradin is commenting on [2] asks whether cooperative breeders (which we define as species where non-breeding helpers assist breeders to raise their young) in mammals are more commonly found in arid environments than monogamous species (defined as species where breeding pairs of males and females remain together for more than one season) from which cooperative breeders appear to be derived [3]. It shows that, as in birds, cooperative breeders tend to live in relatively arid habitats compared to monogamous species. As we describe below, these conclusions are unaffected by differences between our classification of the social organization of shrews and the classification suggested by Schradin. Schradin's first criticism is that the categorizations of shrews that we have used in this analysis were based on one paper on a single species. This is incorrect, for our categorization of shrews was based on more than 70 separate sources (see electronic supplementary material, appendix S1). When we published our dataset [4], we were required to reduce the associated reference list by the editors of the journal and, to comply, we removed around 75% of our 2000+ sources, often listing a single reference per species or group of species, and frequently using generic reviews for particular groups where these were available: for example, for many rodent species, we simply listed Wolff and Sherman's Rodent Societies [5], and …

Mating system as a possible driver of behavioral diversity in Peromyscus

Identifying mechanisms underlying behavioral variation is important for understanding ecological and evolutionary processes. Comparative studies can help test hypotheses about the adaptive value of behaviors. Pace of life history and mating systems are broad factors hypothesized to drive species differences in behaviors. We tested these hypotheses using several Peromyscus species from lab stocks that varied in predicted life history and level of monogamy. We predicted that species with faster life histories would be more bold, active, and neophilic, and that these traits would also be positively correlated at the individual level. We further predicted that there would be greater sex differences in behaviors in non-monogamous, more sexually dimorphic species and that sociability would be more highly correlated with other behavioral traits in monogamous than in non-monogamous species. Counter to predictions, we found that larger stocks (with slower paces of life history) tended to be bolder, and that stock size was not associated with differences in activity, neophilia, or sociability. There was greater sexual differentiation in non-monogamous species in sociability, but not in other behaviors. Monogamous species were generally more sociable, and this was especially pronounced in male mice. Monogamous species showed a positive association between boldness and activity, while non-monogamous species showed a positive association between boldness and neophilia. A negative association between neophilia and sociability was stronger in species predicted to be monogamous. Thus, the pace-of-life-history syndrome hypothesis was not supported in this study, but mating system differences could help drive behavioral diversity. Social system and pace of life history are two factors hypothesized to drive evolution of behavioral diversity, both between and within populations. We examined whether behavioral variation in several species of Peromyscus mice was associated with either of these factors. Larger species, with slower life histories, were potentially bolder. Monogamous species were generally more social (attracted to other individuals), especially when comparing males, and males and females differed more in this trait in non-monogamous species. The correlations among boldness, response to novelty, and sociability were also different between mating systems. These results do not support predictions from pace-of-life history hypotheses, but they suggest that the evolution of different mating systems is associated with systematic behavioral differences across these related species.

Benign neonatal deep hypothermia in rodents and its relations to hibernation.

The neonates of many rodent species survive deep hypothermia (T b = 0-8 °C). In key respects, this hypothermia is more akin to hibernation than was thought during much of the twentieth century, indicating that studies of neonatal hypothermia may usefully supplement studies of hibernation in understanding evolved tissue adaptations to near-freezing T b. To clarify evolutionary diversity in neonatal survival of deep hypothermia, neonates of six species or strains were subjected to a standardized procedure: exposure for 2.5h to test T bs followed by autoresuscitation. Mus and Peromyscus differed dramatically, the lowest T b survived by all ages studied (3-10 days) being 7-8 °C in Mus and 0-1 °C in Peromyscus. There was, however, no evidence of intrageneric plasticity because feral and laboratory Mus were identical, and Peromyscus species with cold- and warm-climate distribution ranges were identical. When neonates survive deep hypothermia, a key question is whether the experience is benign, meaning neonates tolerate hypothermia. To test the benign nature of deep hypothermia, neonates of Peromyscus leucopus were exposed four times (3h each) to T b = 1-2 °C when 3-10 days old; controls were same-sex siblings not hypothermia exposed. When 74 such sibling pairs were exposed after weaning to predation by screech owls, the hypothermia-treated and control siblings did not differ in which was caught first. Based on study of deaths in 253 sibling pairs prior to weaning while under parental care, parents cared for hypothermia-treated siblings as attentively as controls. The results indicate that the experience of multiple neonatal deep-hypothermic episodes is benign in P. leucopus.

Ecology of phlebotomine sandflies and putative reservoir hosts of leishmaniasis in a border area in Northeastern Mexico: implications for the risk of transmission of Leishmania mexicana in Mexico and the USA.

Leishmaniases are a group of important diseases transmitted to humans through the bite of sandfly vectors. Several forms of leishmaniases are endemic in Mexico and especially in the Southeast region. In the Northeastern region, however, there have only been isolated reports of cases and scanty records of sandfly vectors. The main objective of this study was to analyze the diversity of sandflies and potential reservoir hosts of Leishmania spp. in the states of Nuevo León and Tamaulipas. Species richness and abundances of sandflies and rodents were recorded. A fraction of the caught sandflies was analyzed by PCR to detect Leishmania spp. Tissues from captured rodents were also screened for infection. Ecological Niche Models (ENMs) were computed for species of rodent and their association with crop-growing areas. We found 13 species of sandflies, several of which are first records for this region. Medically important species such as Lutzomyia anthophora, Lutzomyia diabolica, Lutzomyia cruciata, and Lutzomyia shannoni were documented. Leishmania spp. infection was not detected in sandflies. Nine species of rodents were recorded, and Leishmania (Leishmania) mexicana infection was found in four species of Peromyscus and Sigmodon. ENMs showed that potential distribution of rodent pest species overlaps with allocated crop areas. This shows that Leishmania (L.) mexicana infection is present in the Northeastern region of Mexico, and that previously unrecorded sandfly species occur in the same areas. These findings suggest a potential risk of transmission of Leishmania (L.) mexicana.

Lentiviral Knockdown of Transcription Factor STAT1 in Peromyscus leucopus to Assess Its Role in the Restriction of Tick-borne Flaviviruses.

Cellular infection with tick-borne flaviviruses (TBFVs) results in activation of the interferon (IFN) signaling pathway and subsequent upregulation of numerous genes termed IFN stimulated genes (ISGs) ( Schoggins et al., 2011 ). Many ISGs function to prevent virus pathogenesis by acting in a broad or specific manner through protein-protein interactions (Duggal and Emerman, 2012). The potency of the IFN signaling response determines the outcome of TBFV infection (Best, 2017; Carletti et al., 2017 ). Interestingly, data from our lab show that TBFV replication is significantly restricted in cells of the reservoir species Peromyscus leucopus thereby suggesting a potent antiviral response ( Izuogu et al., 2017 ). We assessed the relative contribution of IFN signaling to resistance in P. leucopus by knocking down a major transcription factor in the IFN response pathway. Signal transducer and activator of transcription 1 (STAT1) was specifically targeted in P. leucopus cells by shRNA technology. We further tested the impact of gene knockdown on the ability of cells to respond to IFN and restrict virus replication; the results indicate that when STAT1 expression is altered, P. leucopus cells have a decreased response to IFN stimulation and are significantly more susceptible to TBFV replication.

A new species in thePeromyscus boyliispecies group (Cricetidae: Neotominae) from Michoacán, México

Specimens of the Peromyscus boylii species group occurring in the montane regions of Michoacan, Mexico, historically have been assigned to P. levipes. However, previous studies have shown that some specimens from eastern Michoacan possessed mitochondrial DNA haplotypes and karyotypes that were distinct from P. levipes and other members of the P. boylii species group. Phylogenetic analyses (parsimony and likelihood) of additional DNA sequences obtained from the mitochondrial cytochrome-b gene indicated that specimens from central and eastern Michoacan and western Morelos formed a monophyletic clade that was sister to a clade containing representatives of P. beatae. Estimations of genetic divergence for members of these 2 sister clades exceeded 5% and were greater than most pairwise comparisons reported for other members of the P. boylii species group. Collectively, there are no discernable morphological differences between those specimens and other cryptic species in the P. boylii species group. Together, these results indicated that specimens from the Sierra Madre del Sur region of Michoacan, Morelos, and likely throughout the Neovolcanic Axis of the Estado de Mexico represent an undescribed species of Peromyscus for which we propose the name Peromyscus kilpatricki.

Insights on the host associations and geographic distribution of Hymenolepis folkertsi (Cestoda: Hymenolepididae) among rodents across temperate latitudes of North America.

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.

A method to distinguish morphologically similar Peromyscus species using extracellular RNA and high-resolution melt analysis

A method applying high-resolution melt (HRM) analysis to PCR products copied and amplified from extracellular RNA (exRNA) has been developed to distinguish two morphologically similar Peromyscus species: Peromyscus leucopus and Peromyscus maniculatus. P. leucopus is considered the primary reservoir host of Borrelia burgdorferi, the causative agent for Lyme disease in North America. In northern Minnesota the habitat ranges of P. leucopus overlaps with that of P. maniculatus. Serum samples from live mice of both species were collected from cheek bleeds, total extracellular RNA (exRNA) was extracted, copied using reverse transcription and amplified by PCR followed by HRM analysis. A circulating ribosomal RNA (rRNA) was identified which differed at seven nucleotides between the two species and a method of HRM analysis was developed allowing rapid species confirmation. In the future, this HRM based method may be adapted for additional species.

Detection of Chlamydia infection in Peromyscus species rodents from sylvatic and laboratory sources.

To determine if Chlamydia muridarum, or other chlamydiae, are enzootic in rodents, we probed a serum bank of wild Peromyscus spp. mice for immunoglobulin G-antibody reactivity to ultraviolet light-inactivated C. muridarum elementary bodies (EBs) using an enzyme-linked immunoassay. Applying a cut-off for a positive reaction of OD(405) nm = 0.1 at a 1:20 dilution, we found titratable antibody reactivity in 190 of 247 specimens surveyed (77%, mean OD(405) = 0.33 ± 0.26, range = 0.11-1.81, median = 0.25). In addition, serum samples were obtained from a colony of specific pathogen-free Peromyscus spp. maintained at the University of South Carolina and six of 12 samples were reactive (50%, mean OD(405) = 0.19 +/- 0.08, range = 0.1-0.32, median = 0.18). Lastly, 40 additional wild Peromyscus spp. were captured in a disparate region of Midwestern USA and 22 serum specimens were reactive (55%, mean OD(405) = 0.22 +/- 0.11, range = 0.1-0.48, median = 0.2). Specificity of selected reactive sera for chlamydial antigen was confirmed on Western blot using resolved purified EBs as the detecting antigen. From tissues removed from several mice at necropsy, the gene for chlamydial 16S ribosomal ribonucleic acid (rRNA) was amplified by polymerase chain reaction (PCR). Positive samples of 16S rRNA were subjected to additional PCR for the major outer membrane protein gene (ompA). The amplicons of three select ompA positive samples were sequenced with ≥99% homology with C. muridarum. Our findings indicate that chlamydial infection is enzootic for Peromyscus spp., and that C. muridarum, or a closely related species or strain, is likely the agent in the tested rodent species.