Paula E. Marquardt

White‐nose syndrome (WNS), caused by the fungal pathogen Pseudogymnoascus destructans (Pd), has driven alarming declines in North American hibernating bats, such as little brown bat (Myotis lucifugus). During hibernation, infected little brown bats are able to initiate anti‐Pd immune responses, indicating pathogen‐mediated selection on the major histocompatibility complex (MHC) genes. However, such immune responses may not be protective as they interrupt torpor, elevate energy costs, and potentially lead to higher mortality rates. To assess whether WNS drives selection on MHC genes, we compared the MHC DRB gene in little brown bats pre‐ (Wisconsin) and post‐ (Michigan, New York, Vermont, and Pennsylvania) WNS (detection spanning 2014–2015). We genotyped 131 individuals and found 45 nucleotide alleles (27 amino acid alleles) indicating a maximum of 3 loci (1–5 alleles per individual). We observed high allelic admixture and a lack of genetic differentiation both among sampling sites and between pre‐ and post‐WNS populations, indicating no signal of selection on MHC genes. However, post‐WNS populations exhibited decreased allelic richness, reflecting effects from bottleneck and drift following rapid population declines. We propose that mechanisms other than adaptive immunity are more likely driving current persistence of little brown bats in affected regions.

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Research Highlights: Long-term exposure of paper birch to elevated carbon dioxide (CO₂) and ozone (O₃) modified metabolite content of over-wintering buds, but no evidence of reduced freezing tolerance was found. Background and Objectives: Atmospheric change may affect the metabolite composition of over-wintering buds and, in turn, impact growth onset and stress tolerance of perennial plant species in spring. Materials and Methods: Low molecular weight compounds of paper birch (Betula papyrifera) buds, including lipophilic, polar and phenolic compounds were analyzed, and freezing tolerance (FT) of the buds was determined prior to bud break after 11 growing seasons exposure of saplings to elevated concentrations of CO₂ (target concentration 560 µL L⁻¹) and O₃ (target concentration 1.5 × ambient) at the Aspen FACE (Free-Air CO₂ and O₃ Enrichment) facility. Results: The contents of lipophilic and phenolic compounds (but not polar compounds) were affected by elevated CO₂ and elevated O₃ in an interactive manner. Elevated O₃ reduced the content of lipids and increased that of phenolic compounds under ambient CO₂ by reallocating carbon from biosynthesis of terpenoids to that of phenolic acids. In comparison, elevated CO₂ had only a minor effect on lipophilic and polar compounds, but it increased the content of phenolic compounds under ambient O₃ by increasing the content of phenolic acids, while the content of flavonols was reduced. Conclusions: Based on the freezing test and metabolite data, there was no evidence of altered FT in the over-wintering buds. The impacts of the alterations of bud metabolite contents on the growth and defense responses of birches during early growth in spring need to be uncovered in future experiments.

Rising temperatures and changes in precipitation may affect plant responses, and mountainous regions in particular are sensitive to the impacts of climate change. The Santa Catalina Mountains, near Tucson, Arizona, USA, are among the best known Madrean Sky Islands, which are defined by pine-oak forests. We compared the sensitivity and temporal stability of climate–growth relationships to quantify the growth responses of sympatric taxa of ponderosa pine to changing climate. Three taxa (three-needle, mixed-needle, and five-needle types) collected from southern slopes of two contact zones (Mt. Lemmon, Mt. Bigelow) were evaluated. Positive climate–growth correlations in these semiarid high-elevation pine forests indicated a seasonal shift from summer- to spring-dominant precipitation since 1950, which is a critical time for reproduction. Mixed- and five-needle types responded to winter precipitation, and growth was reduced for the five-needle type when spring conditions were dry. Growth trends in response to temperature and specific to site were observed, which indicated the climate signal can be weakened when data are combined into a single chronology. Significant fluctuations in temperature–growth correlations since 1950 occurred for all needle types. These results demonstrated a dramatic shift in sensitivity of annual tree growth to the seasonality of the limiting factor, and a climatic trend that increases local moisture stress may impact the stability of climate–growth relationships. Moreover, output from temperature–growth analyses based on ring-width data (for example from semiarid sites) that does not account for positive and negative growth trends may be adversely affected, potentially impacting climate reconstructions.

The robust dispersal capability of the coyote ( Canis latrans ) would suggest a pattern of widespread gene flow across North America, yet historical legacies, dispersal barriers, and habitat affinities may produce or reinforce genetic structure. In the northeastern United States, some coyotes carry genetic signatures from past hybridization events with eastern wolves ( C. lupus lycaon ). These so‐called “coywolves” may have differential predation or competitive success compared with the western origin coyotes with whom they share the contemporary landscape. We sampled coyote populations from New York ( n = 156) and Wyoming, USA ( n = 8) in 2006–2007 and from South Carolina, USA, in 2010 and confirmed regional genetic structure among these coyote populations. Then, within the putative contact zone between the northeastern and western coyote colonization fronts (New York State), we evaluated evidence for broad‐ and fine‐sale genetic structure, and a genetic gradient among New York coyotes using a suite of spatial genetic analyses. Although broad‐scale analyses indicated New York coyotes were highly intermixed, subtle isolation‐by‐distance was detected, and local spatial autocorrelation indicated potentially shorter dispersal distances and larger group sizes for coyotes in the Northeastern Highlands (Adirondack Mountains and foothills). Yet we failed to detect a distinct contact zone between 2 coyote types in New York, indicating that local abundance and ecological context rather than genetic lineage are likely to determine the local ecological effects of coyotes in this region. We suggest that the contact zone between coyote colonization fronts has either eroded or moved further south. © 2019 The Wildlife Society.

Genes of the major histocompatibility complex (MHC) are of great interest to molecular ecologists due to their role in the immune response and the complex evolutionary mechanisms affecting their abundance and distribution. Next generation sequencing (NGS) offers the best potential for characterizing such genes by overcoming the low throughput constraints associated with traditional cloning and Sanger sequencing. However, available bioinformatics methods to effectively filter MHC data acquired through NGS are complex and have not been widely applied. Here we present a method to sequence MHC II DRB of the little brown bat (Myotis lucifugus) using semi-conductor sequencing on the Ion Torrent Personal Genome Machine (PGM) and subsequently analyze the data using a modified UPARSE clustering algorithm. As proof of concept, preliminary characterization of the MHC II DRB alleles of 15 little brown bats was accomplished through PGM sequencing. Analysis identified 24 MHC II DRB alleles overall and a high number of alleles per individual (average 6.8 ± 3.5, range 1 – 12), indicating little brown bats may have among the highest number of MHC DRB loci documented in mammals. Our method provides a framework for studying MHC II DRB diversity in little brown bats, which are experiencing significant population declines in North America due to the recent emergence of white-nose syndrome (WNS).

We evaluated the population genetic structure of seven microsatellite loci for old growth and second growth populations of eastern white pine (Pinus strobus). From each population, located within Hartwick Pines State Park, Grayling, Michigan, USA, 120-122 contiguous trees were sampled for genetic analysis. Within each population, genetic diversity was high and inbreeding low. When comparing these populations, there is a significant, but small (less than 1%), genetic divergence between populations. Spatial distance between populations or timber harvest at the second growth site were reasonable explanations for the observed minor differences in allele frequencies between populations. Spatial autocorrelation analysis suggested that, for the old growth population, weak positive structuring at 15 m fits the isolation by distance model for a neighbourhood size of about 100 individuals. In comparison, genotypes were randomly distributed in the second growth population. Thus, logging may have decreased spatial structuring at the second growth site, suggesting that management practices may be used to alter natural spatial patterns. In addition, the amount of autocorrelation in the old growth population appears to be lower for some of the microsatellites, suggesting higher numbers of rare alleles and that higher mutation rates may have directly affected spatial statistics by reducing structure.