Unveiling the Gut Microbiota and Resistome of Wild Cotton Mice, Peromyscus gossypinus , from Heavy Metal- and Radionuclide-Contaminated Sites in the Southeastern United States

Antimicrobial resistance is a serious global public health concern because of its prevalence and ubiquitous distribution. The rapid dissemination of antibiotic resistance genes is thought to be the result of the massive overuse of antibiotics in agriculture and therapeutics.

Mammal Molar Size Ratios and the Inhibitory Cascade at the Intraspecific Scale

Synopsis Mammalian molar crowns form a module in which measurements of size for individual teeth within a tooth row covary with one another. Molar crown size covariation is proposed to fit the inhibitory cascade model (ICM) or its variant the molar module component (MMC) model, but the inability of the former model to fit across biological scales is a concern in the few cases where it has been tested in Primates. The ICM has thus far failed to explain patterns of intraspecific variation, an intermediate biological scale, even though it explains patterns at both smaller organ-level and larger between-species biological scales. Studies of this topic in a much broader range of taxa are needed, but the properties of a sample appropriate for testing the ICM at the intraspecific level are unclear. Here, we assess intraspecific variation in relative molar sizes of the cotton mouse, Peromyscus gossypinus, to further test the ICM and to develop recommendations for appropriate sampling protocols in future intraspecific studies of molar size variation across Mammalia. To develop these recommendations, we model the sensitivity of estimates of molar ratios to sample size and simulate the use of composite molar rows when complete ones are unavailable. Similar to past studies on primates, our results show that intraspecific variance structure of molar ratios within the rodent P. gossypinus does not meet predictions of the ICM or MMC. When we extend these analyses to include the MMC, one model does not fit observed patterns of variation better than the other. Standing variation in molar size ratios is relatively constant across mammalian samples containing all three molars. In future studies, analyzing average ratio values will require relatively small minimum sample sizes of two or more complete molar rows. Even composite-based estimates from four or more specimens per tooth position can accurately estimate mean molar ratios. Analyzing variance structure will require relatively large sample sizes of at least 40–50 complete specimens, and composite molar rows cannot accurately reconstruct variance structure of ratios in a sample. Based on these results, we propose guidelines for intraspecific studies of molar size covariation. In particular, we note that the suitability of composite specimens for averaging mean molar ratios is promising for the inclusion of isolated molars and incomplete molar rows from the fossil record in future studies of the evolution of molar modules, as long as variance structure is not a key component of such studies.

Diet-based assortative mating through sexual imprinting

Speciation is facilitated when traits subject to divergent selection also contribute to non-random mating—so-called ‘magic traits.’ Diet is a potential magic trait in animal populations because selection for divergence in consumed food may contribute to assortative mating and therefore sexual isolation. However, the mechanisms causing positive diet-based assortment are largely unknown. Here, using diet manipulations in a sexually imprinting species of mouse, Peromyscus gossypinus (the cotton mouse), we tested the hypothesis that sexual imprinting on a divergent diet could be a mechanism that generates rapid and significant sexual isolation. We provided breeding pairs with novel garlic- or orange-flavored water and assessed whether their offspring, exposed to these flavors in utero and in the nest before weaning, later preferred mates that consumed the same flavored water as their parents. While males showed no preference, females preferred males of their parental diet, which generated significant sexual isolation. Thus, our experiment demonstrates that sexual imprinting on dietary cues learned in utero and/or postnatally can facilitate reproductive isolation and potentially speciation.

The RareospCAllele L of Borrelia burgdorferi Sensu Stricto, Commonly Found among Samples Collected in a Coastal Plain Area of the Southeastern United States, Is Associated with Ixodes affinis Ticks and Local Rodent Hosts Peromyscus gossypinus and Sigmodon hispidus

ABSTRACTThe rareospCallele L was detected in 30% ofBorrelia burgdorferisensu stricto strains cultured from a tick species,Ixodes affinis, and two rodent host species,Peromyscus gossypinusandSigmodon hispidus, collected in a coastal plain area of Georgia and South Carolina, in the southeastern United States.

Borrelia carolinensis sp. nov., a novel species of the Borrelia burgdorferi sensu lato complex isolated from rodents and a tick from the south-eastern USA

A group of 16 isolates with genotypic characteristics different from those of known species of the Borrelia burgdorferi sensu lato complex were cultured from ear biopsies of the rodents Peromyscus gossypinus and Neotoma floridana trapped at five localities in South Carolina, USA, and from the tick Ixodes minor feeding on N. floridana. Multilocus sequence analysis of members of the novel species, involving the 16S rRNA gene, the 5S–23S (rrf–rrl) intergenic spacer region and the flagellin, ospA and p66 genes, was conducted and published previously and was used to clarify the taxonomic status of the novel group of B. burgdorferi sensu lato isolates. Phylogenetic analysis based on concatenated sequences of the five analysed genomic loci showed that the 16 isolates clustered together but separately from other species in the B. burgdorferi sensu lato complex. The analysed group therefore represents a novel species, formally described here as Borrelia carolinensis sp. nov., with the type strain SCW-22T (=ATCC BAA-1773T =DSM 22119T).

Small Mammal Distributions Relative to Corridor Edges Within Intensively Managed Southern Pine Plantations

We characterized small mammal communities in three loblolly pine (Pinus taeda) stands in the Lower Coastal Plain of South Carolina during June 1998–Aug. 2000 to investigate influence of corridor edges on small mammal distribution. We live-trapped small mammals in three regenerating stands following clearcutting. Harvested stands were bisected by 100-m-wide, 20–23-year-old pine corridors. During 47,040 trap nights, we recorded 907 captures of 661 individual small mammals. Species captured included southern short-tailed shrews (Blarina carolinensis), cotton mice (Peromyscus gossypinus), cotton rats (Sigmodon hispidus), eastern harvest mice (Reithrodontomys humulis), marsh rice rats (Oryzomys palustris), and golden mice (Ochrotomys nuttalli). We did not observe an edge effect (i.e., preference or avoidance) in small mammal captures at the corridor edge. Rodent captures were greatest in harvested stands, declined near the edge of mature pine corridors, and were lowest within corridors. Shrew captures were generally greatest in mature pine corridors and least in the interior of harvested stands. Retention of mature pine corridors of only 100 m may maintain some small mammals (i.e., shrews) that would not occur if stands were completely harvested. South. J. Appl. For. 29(3):148–151.