Geology topics

Christopher S. Hobson

Publications and source records attributed to Christopher S. Hobson.

4 recordsLinked to original sources

USGS2016

Comparative mitogenomic analyses of three North American stygobiont amphipods of the genus Stygobromus (Crustacea: Amphipoda)

The mitochondrial genomes of three North American stygobiont amphipods Stygobromus tenuis potomacus , S. foliatus and S. indentatus collected from Caroline County, VA, were sequenced using a shotgun sequencing approach on an Illumina NextSeq500 (Illumina Inc., San Diego, CA). All three mitogenomes displayed 13 protein-coding genes, 22 tRNAs and two rRNAs typical of metazoans. While S. tenuis and S. indentatus displayed identical gene orders similar to the pancrustacean ground pattern, S. foliatus displayed a transposition of the trnL2 - cox2 genes to after atp8-atp6 . In addition, a short atp8 gene, longer rrnL gene and large inverted repeat within the Control Region distinguished S. foliatus from S. tenuis potomacus and S. indentatus . Overall, it appears that gene order varies considerably among amphipods, and the addition of these Stygobromus mitogenomes to the existing sequenced amphipod mitogenomes will prove useful for characterizing evolutionary relationships among various amphipod taxa, as well as investigations of the evolutionary dynamics of the mitogenome in general.

Mitochondrial DNA Part B↗

USGS2016

Changes in rates of capture and demographics of Myotis septentrionalis (Northern Long-eared Bat) in Western Virginia before and after onset of white-nose syndrome

Documenting the impacts of white-nose syndrome (WNS) on demographic patterns, such as annual survivorship and recruitment, is important to understanding the extirpation or possible stabilization and recovery of species over time. To document demographic impacts of WNS on Myotis septentrionalis (Northern Long-eared Bat), we mistnetted at sites in western Virginia where Northern Long-eared Bats were captured in summer before (1990–2009) and after (2011–2013) the onset of WNS. Our mean capture rates per hour, adjusted for area of net and sampling duration, declined significantly from 0.102 bats/ m 2 /h before WNS to 0.005 bats/m 2 /h (-95.1%) by 2013. We noted a time lag in the rate of decline between published data based on bats captured during the swarming season and our summer mist-netting captures from the same geographic area. Although proportions of pregnant or lactating females did not vary statistically in samples obtained before and after the onset of WNS, the proportion of juvenile bats declined significantly (-76.7%), indicating that the viability of Northern Long-eared Bats in western Virginia is tenuous.

Virginia↗

USGS2016

Monitoring the status of Gray Bats (Myotis grisescens in Virginia, 2009-2014, and potential impacts of White-nose Syndrome

Myotis grisescens (Gray Bat) is a federally endangered species distributed over the mid-South with a summer range that extends across the upper Tennessee River Basin, including southwest Virginia. Given the onset of White-nose Syndrome (WNS) in the Commonwealth in the winter of 2009, we initiated yearly surveys in late summer 2009 to monitor the status of known summer populations. Our objectives were to examine the relative health of these bats using body mass index (BMI), and determine any changes in juvenile recruitment across sites and years. We did not find any marked changes in BMI across years after WNS for Gray Bats. This finding suggests that surviving bats are either not negatively impacted by WNS or have recovered sufficiently by late summer as to not document obvious differences across years. After limiting our analyses of juvenile recruitment to only the individuals that we had definitively aged via backlit photos (2010–2014), we found a non-significant declining trend in juvenile recruitment; a trend that merits continued monitoring in the years to come. As Gray Bats have only recently shown to be susceptible to WNS infection, it is possible that observable population declines are forthcoming.

Virginia↗

USGS2015

Post-White-nose syndrome trends in Virginia’s cave bats, 2008-2013

Since its 2009 detection in Virginia hibernacula, the fungal pathogen Pseudogymnoascus destructans causing White-nose Syndrome (WNS) has had a marked impact on cave bats locally. From 2008-2013, we documented numeric and physiologic changes in cave bats through fall swarm (FS), early hibernation (EH), and late hibernation (LH) capture and banding surveys at 18 hibernacula in western Virginia. We coupled active surveys with passive biennial winter counts in 2009, 2011, and 2013. We compared individual body mass index (BMI) across years for FS, EH, and LH hibernation to determine if WNS impacts on extant bats would be manifested by changes in body condition (as anecdotally observed elsewhere for WNS-impacted bats) as well as a population reduction. To estimate percent declines in bat presence or relative activity, we used FS capture per-unit-effort data, and the winter hibernacula absolute counts. We captured 4,524 bats of eight species, with species-specific capture success declining by 75-100% post-WNS. Little brown bats (Myotis lucifugus) exhibited the greatest declines in winter hibernacula counts (AVG. = 99.0% decline), followed by tri-colored bats (Perimyotis subflavus; 89.5% decline) and Indiana bats (M. sodalis; 33.5% decline). Graphical analyses of captures-per-trap-hour in FS showed declines for little brown bats, tri-colored bats, and northern long-eared bats (M. septentrionalis), but suggest a modest rebound of Indiana bat numbers. Fall swarm trends in BMI suggested some drops post-WNS exposure, but these trends were not consistent across sexes or seasonal time blocks. Our inconclusive BMI metrics and little brown bat band recapture data suggest little competitive advantage or selection for surviving bats. Lesser (but apparent) declines in Indiana bat numbers mirrors trends seen elsewhere regionally, and band recoveries do show that some individuals are persisting. Additional surveys will determine if bats in Virginia will persist or face extirpation due to presumed low recruitment and survivorship.

Virginia↗