Bumble bee species distributions and habitat associations in the Midwestern USA, a region of declining diversity

Jessie Lanterman Novotny, Paige Reeher, Megan Varvaro, Andrew Lybbert, Jesse Smith, Randall J. Mitchell & Karen Goodell. Biodivers Conserv 30, 865–887 (2021). https://doi.org/10.1007/s10531-021-02121-x

Abstract

Bumble bees (Bombus spp.) are important pollinators, yet rapidly declining globally. In North America some species are thriving while others are nearing extinction. Recognizing subtle differences in species’ biology and responses to environmental factors is required to illuminate key threats and to understand their different population trajectories. We intensively surveyed bumble bees in Ohio, USA, along the receding southern boundary of many species’ ranges, to evaluate current conservation status of the state’s species. In 318 90-min field surveys across two consecutive years we observed 23,324 bumble bees of 10 species visiting 170 plant species. Habitat, landscape, latitude, and their interactions significantly influenced bumble bee abundance, species richness, and community composition during peak season. Sites planted with flowers yielded more bumble bee individuals and species than did sites not planted with bee food plants. Bombus impatiens, B. griseocollis, and B. bimaculatus comprised 93% of all observations. Their abundances all peaked in habitats planted with wildflowers, but there were species-specific responses to local and landscape factors. Three less common species (B. fervidus, B. vagans, and B. perplexus) were more likely to be found in forested landscapes, particularly in the northeastern portion of the state. Bombus perplexus was also affiliated with planted urban wildflower patches. These results provide a strong starting point for future monitoring and conservation intervention that targets less common species. A quantitative synthesis of detailed state-level and regional datasets would allow additional insight into broad scale patterns of diversity in bumble bee communities and species conservation trajectories.

Freshwater mussels (Unionidae) brought into captivity exhibit up-regulation of genes involved in stress and energy metabolism

Ieva Roznere, Brandon T. Sinn, Marymegan Daly & G. Thomas Watters. Sci Rep 11, 2241 (2021). https://doi.org/10.1038/s41598-021-81856-7

Abstract

Approximately two thirds of freshwater mussel species in the United States and Canada are imperiled, and populations are declining rapidly. Translocation and captive management are commonly used to mitigate losses of freshwater mussel biodiversity, but these conservation tools may result in decreased growth and increased mortality. This study uses RNA-Seq to determine how translocation into captivity affects gene expression in Amblema plicata. Mussels were collected from the Muskingum River in Ohio, USA and brought into a captive holding facility. RNA was extracted from gill tissue 11 months post translocation from mussels in captivity and the Muskingum River on the same day. RNA was sequenced on an Illumina HiSeq 2500, and differential expression analysis was performed on de novo assembled transcripts. More than 1200 transcripts were up-regulated in captive mussels, and 246 were assigned functional annotations. Many up-regulated transcripts were involved in energy metabolism and the stress response, such as heat shock proteins and antioxidants. More than 500 transcripts were down-regulated in captive mussels, and 41 were assigned functional annotations. We observed an over-representation of down-regulated transcripts associated with immune response. Our work suggests that A. plicata experienced moderate levels of stress and altered energy metabolism and immune response for at least 11 months post translocation into captivity.

Mixed‐stock analysis using Rapture genotyping to evaluate stock‐specific exploitation of a walleye population despite weak genetic structure

Peter T. Euclide, Tom MacDougall, Jason M. Robinson, Matthew D. Faust, Chris C. Wilson, Kuan‐Yu Chen, Elizabeth A. Marschall, Wesley Larson, Stuart A. Ludsin. 2021. https://doi.org/10.1111/eva.13209

Abstract

Mixed‐stock analyses using genetic markers have informed fisheries management in cases where strong genetic differentiation occurs among local spawning populations, yet many fisheries are supported by multiple, weakly differentiated stocks. Freshwater fisheries exemplify this problem, with many populations supported by multiple stocks of young evolutionary age and isolated across small spatial scales. Consequently, attempts to conduct genetic mixed‐stock analyses of inland fisheries have often been unsuccessful. Advances in genomic sequencing offer the ability to discriminate among populations with weak population structure; providing the necessary resolution to conduct mixed‐stock assignment among previously indistinguishable stocks. We used genomic data to conduct a mixed‐stock analysis of eastern Lake Erie's commercial and recreational walleye (Sander vitreus) fisheries and estimate the relative harvest of weakly differentiated stocks (pairwise FST < 0.01). Using RAD‐capture (Rapture), we sequenced and genotyped individuals at 12,081 loci that had been previously determined to be capable of discriminating between western and eastern basin stocks with 95% reassignment accuracy, which was not possible in the past with microsatellite markers. The baseline assessment of 395 walleye from 11 spawning stocks identified three reporting groups and refined previous assessments of gene flow among walleye stocks. Genetic assignment of 1,075 walleye harvested in eastern Lake Erie’s recreational and commercial fisheries indicated that western basin stocks constituted the majority of harvest during the peak walleye fishing season (July – September), whereas eastern basin individuals comprised much of the early season harvest (May – June). Clear spatial structure in harvest composition existed; catches in more easterly sites contained more individuals of eastern basin origin than did more westerly sites. Our study provides important stock contribution estimates for Lake Erie fishery management and demonstrates the utility of genomic data to facilitate mixed‐stock analysis in exploited fish populations having weak population structure or limited existing genetic resources.

Genomic data from the Brazilian sibilator frog reveal contrasting pleistocene dynamics and regionalism in two South American dry biomes

Maria Tereza C. Thomé, Bryan C. Carstens, Miguel T. Rodrigues, João Alexandrino, Célio F. B. Haddad. 2021. https://doi.org/10.1111/jbi.14064

Abstract

Aim

Knowledge about the Neotropical dry formations, particularly the Caatinga, remains rudimentary compared to other biotas in the region. Here we address several biogeographical hypotheses by combining intense geographical and genomic sampling obtained for the Brazilian sibilator frog. We specifically test predictions related to the putative roles of past climate shifts (Pleistocene and Holocene) and local geographical barriers (past and current courses of the São Francisco River, SFR) in causing population differentiation in this species.

Location

Caatinga and eastern Cerrado.

Taxon

Brazilian sibilator frog Leptodactylus troglodytes.

Methods

We sequenced up to ~15,000 single nucleotide polymorphisms for 159 samples from 61 locations. We inferred genetic structure using spatial clustering and examined population sizes through time. We estimated the relationship among populations using phylogenetic reconstruction, estimated historical distributions with ecological niche modelling and inferred demographic history under isolation‐with‐migration models.

Results

Genetic diversity in L. troglodytes corresponds to biome boundaries, with one population in the Cerrado and two populations in the Caatinga, separated by the SFR. Demographic model selection indicates the Caatinga populations expanded since the end of the Pleistocene while the Cerrado population declined. Within the Caatinga, population expansion began earlier and was more extreme in the north. A continuous stability area maintained the two Caatinga populations, which share a common origin and began diverging in the mid‐Pleistocene, first with symmetric gene flow and later under pronounced migration from the north.

Main conclusions

We could not reject a role of past climate change in causing diversification of relictual populations in the Cerrado, but we found no evidence of multiple refuges or long‐term isolation within the Caatinga. Instead, diversification in this biome appears to be caused by the SFR acting as a ‘soft barrier’ that constrains migration over an extended period of time.

Expression of aquaporins in response to distinct dehydration stresses that confer stress tolerance in the Antarctic midge Belgica antarctica

Mizuki Yoshida, Richard E. Lee Jr, David L.Denlinger, Shin G.Goto. 2021. https://doi.org/10.1016/j.cbpa.2021.110928

Abstract

Larvae of the Antarctic midge Belgica antarctica Jacobs (Diptera: Chironomidae) are highly tolerant of diverse environmental stresses, including freezing, severe desiccation, and osmotic extremes. Furthermore, dehydration confers subsequent desiccation and freeze tolerance. While a role for aquaporins—channels for water and other solutes—has been proposed in these dehydration processes, the types of aquaporins involved in dehydration-driven stress tolerance remain unknown. In the present study, we investigated expression of six aquaporins (Drip, Prip, Eglp1, Eglp2, Aqp12L, and Bib) in larvae of B. antarctica subjected to three different dehydration conditions: desiccation, cryoprotective dehydration, and osmotic dehydration. The expression of Drip and Prip was up-regulated under desiccation and cryoprotective dehydration, suggesting a role for these aquaporins in efficient water loss under these dehydration conditions. Conversely, expression of Drip and Prip was down-regulated under osmotic dehydration, suggesting that their expression is suppressed in larvae to combat dehydration. Larval water content was similarly decreased under all three dehydration conditions. Differences in responses of the aquaporins to the three forms of dehydration suggests distinct water management strategies associated with different forms of dehydration stress.

Stress hormone-mediated antipredator morphology improves escape performance in amphibian tadpoles

Michael E. Fraker, Stuart A. Ludsin, Barney Luttbeg & Robert J. Denver. Sci Rep 11, 4427 (2021). https://doi.org/10.1038/s41598-021-84052-9

Abstract

Complete functional descriptions of the induction sequences of phenotypically plastic traits (perception to physiological regulation to response to outcome) should help us to clarify how plastic responses develop and operate. Ranid tadpoles express several plastic antipredator traits mediated by the stress hormone corticosterone, but how they influence outcomes remains uncertain. We investigated how predator-induced changes in the tail morphology of wood frog (Rana sylvatica) tadpoles influenced their escape performance over a sequence of time points when attacked by larval dragonflies (Anax junius). Tadpoles were raised with no predator exposure, chemical cues of dragonflies added once per day, or constant exposure to caged dragonflies crossed with no exogenous hormone added (vehicle control only), exogenous corticosterone, or metyrapone (a corticosteroid synthesis inhibitor). During predation trials, we detected no differences after four days, but after eight days, tadpoles exposed to larval dragonflies and exogenous corticosterone had developed deeper tail muscles and exhibited improved escape performance compared to controls. Treatment with metyrapone blocked the development of a deeper tail muscle and resulted in no difference in escape success. Our findings further link the predator-induced physiological stress response of ranid tadpoles to the development of an antipredator tail morphology that confers performance benefits.