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1. Climate variables explain neutral and adaptive variation within salmonid metapopulations: the importance of replication in landscape genetics

   https://doi.org/10.1111/mec.13517  

   Hand, Brian K. ; Muhlfeld, Clint C. ; Wade, Alisa A. ; Kovach, Ryan P. ; Whited, Diane C. ; Narum, Shawn R. ; Matala, Andrew P. ; Ackerman, Michael W. ; Garner, Brittany A. ; Kimball, John S. ; et al ( February 2016 , Molecular Ecology)

   Understanding how environmental variation influences population genetic structure is important for conservation management because it can reveal how human stressors influence population connectivity, genetic diversity and persistence. We used riverscape genetics modelling to assess whether climatic and habitat variables were related to neutral and adaptive patterns of genetic differentiation (population‐specific and pairwiseF_ST) within five metapopulations (79 populations, 4583 individuals) of steelhead trout (Oncorhynchus mykiss) in the Columbia River Basin,USA. Using 151 putatively neutral and 29 candidate adaptiveSNPloci, we found that climate‐related variables (winter precipitation, summer maximum temperature, winter highest 5% flow events and summer mean flow) best explained neutral and adaptive patterns of genetic differentiation within metapopulations, suggesting that climatic variation likely influences both demography (neutral variation) and local adaptation (adaptive variation). However, we did not observe consistent relationships between climate variables andF_STacross all metapopulations, underscoring the need for replication when extrapolating results from one scale to another (e.g. basin‐wide to the metapopulation scale). Sensitivity analysis (leave‐one‐population‐out) revealed consistent relationships between climate variables andF_STwithinthree metapopulations; however, these patterns were not consistent in two metapopulations likely due to small sample sizes (N = 10). These results provide correlative evidence that climatic variation has shaped the genetic structure of steelhead populations and highlight the need for replication and sensitivity analyses in land and riverscape genetics.

    

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2. Species‐level view of population structure and gene flow for a critically endangered primate ( Varecia variegata )

   https://doi.org/10.1002/ece3.1119  

   Baden, Andrea L. ; Holmes, Sheila M. ; Johnson, Steig E. ; Engberg, Shannon E. ; Louis, Jr, Edward E. ; Bradley, Brenda J. ( June 2014 , Ecology and Evolution)

   Lemurs are among the world's most threatened mammals. The critically endangered black‐and‐white ruffed lemur (Varecia variegata), in particular, has recently experienced rapid population declines due to habitat loss, ecological sensitivities to habitat degradation, and extensive human hunting pressure. Despite this, a recent study indicates that ruffed lemurs retain among the highest levels of genetic diversity for primates. Identifying how this diversity is apportioned and whether gene flow is maintained among remnant populations will help to diagnose and target conservation priorities. We sampled 209 individuals from 19 sites throughout the remainingV. variegatarange. We used 10 polymorphic microsatellite loci and ~550 bp of mtDNAsequence data to evaluate genetic structure and population dynamics, including dispersal patterns and recent population declines. Bayesian cluster analyses identified two distinct genetic clusters, which optimally partitioned data into populations occurring on either side of theMangoro River. Localities north of the Mangoro were characterized by greater genetic diversity, greater gene flow (lower genetic differentiation) and higher mtDNAhaplotype and nucleotide diversity than those in the south. Despite this, genetic differentiation across all sites was high, as indicated by high averageF_ST(0.247) and Φ_ST(0.544), and followed a pattern of isolation‐by‐distance. We use these results to suggest future conservation strategies that include an effort to maintain genetic diversity in the north and restore connectivity in the south. We also note the discordance between patterns of genetic differentiation and current subspecies taxonomy, and encourage a re‐evaluation of conservation management units moving forward.

    

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3. Physical effects of habitat‐forming species override latitudinal trends in temperature

   https://doi.org/10.1111/ele.12881  

   Jurgens, L. J. ; Gaylord, B. ; Diaz‐Pulido, ed., Guillermo ( November 2017 , Ecology Letters)

   Latitudinal and elevational temperature gradients (LTGandETG) play central roles in biogeographical theory, underpinning predictions of large‐scale patterns in organismal thermal stress, species' ranges and distributional responses to climate change. Yet an enormous fraction of Earth's taxa live exclusively in habitats where foundation species modify temperatures. We examine little‐explored implications of this widespread trend using a classic model system for understanding heat stresses – rocky intertidal shores. Through integrated field measurements and laboratory trials, we demonstrate that thermal buffering by centimetre‐thick mussel and seaweed beds eliminates differences in stress‐inducing high temperatures and associated mortality risk that would otherwise arise over 14° of latitude and ~ 1 m of shore elevation. These results reveal the extent to which physical effects of habitat‐formers can overwhelm broad‐scale thermal trends, suggesting a need to re‐evaluate climate change predictions for many species. Notably, inhabitant populations may exhibit deceptive resilience to warming until refuge‐forming taxa become imperiled.

    

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4. Molecular systematics of the Amazonian endemic genus Hylexetastes (Aves: Dendrocolaptidae): taxonomic and conservation implications

   https://doi.org/10.1111/ibi.12693  

   Azuaje‐Rodríguez, Roxiris A. ; Weckstein, Jason D. ; Dispoto, Janice H. ; Patel, Swati ; Cacioppo, Joseph A. ; Bates, John M. ; Silva, Sofia Marques ; Aleixo, Alexandre ( December 2018 , Ibis)

   Hylexetasteswoodcreepers are endemic to theterra firmeforests of the Amazon basin. Currently, most taxonomic sources recognize two species ofHylexetastes(H. perrotiiandH. stresemanni), each divided into three subspecies. Some authors maintain that theH. perrotiisubspecies should be elevated to full species status. In particular,Hylexetastes perrotii brigidaiis endemic to the eastern Amazon, the second Amazonian area of endemism (Xingu) most affected by deforestation and habitat degradation. Consequently, the taxonomic status ofH. p. brigidaiis of particular concern for conservation. Thus far, only morphological characters have been evaluated for the taxonomic delimitation of species and subspecies ofHylexetastes. We present a molecular phylogenetic analysis of all subspecies to help delimitHylexetastesinterspecific limits. Fragments of two mitochondrial (CytbandND2) and three nuclear genes (FGB5, G3PDHandMUSK) from 57Hylexetastesspecimens were sequenced. An ecological niche model was estimated to describe more accurately the potential distributions of taxa and to evaluate their vulnerability to ongoing deforestation. Phylogenetic analyses support the paraphyly of the polytypicH. perrotiias currently delimited and the elevation ofHylexetastes perrotii uniformisto full species rank, as well as the presence of three evolutionary significant units (ESUs) within this newly delimited species, including one grouping allH. p. brigidaispecimens. Alternatively, under lineage‐based species concepts, our results support at least five evolutionary species inHylexetastes:H. stresemanni,H. undulatus,H. perrotii,H. uniformisandH. brigidai. Each of these taxa andESUs are distributed in different interfluvial areas of the Amazon basin, which have different degrees of disturbance. Because they occupy the most heavily impacted region among allHylexetastesESUs, regular assessments of the conservation statuses ofH. p. brigidaiand bothH. uniformisESUs are paramount.

    

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5. Conservation genetic assessment of the paleback darter, Etheostoma pallididorsum , a narrowly distributed endemic in the Ouachita Highlands, Arkansas, USA

   https://doi.org/10.1002/aqc.3510  

   McCall, Brittany L. ; Fluker, Brook L. ( March 2021 , Aquatic Conservation: Marine and Freshwater Ecosystems)

   The paleback darter,Etheostoma pallididorsum, is considered imperilled and has recently been petitioned for listing under the Endangered Species Act. Previous allozyme‐based studies found evidence of a small effective population size, warranting conservation concern. The objective of this study was to assess the population dynamics and the phylogeographical history of the paleback darter, using a multilocus microsatellite approach and mitochondrial DNA.

   The predictions of this study were that: paleback darter populations will exhibit low genetic diversity and minimal gene flow; population structure will correspond to the river systems from which the samples are derived; reservoir dams impounding the reaches between the Caddo and Ouachita rivers would serve as effective barriers to gene flow; and the Caddo and Ouachita rivers are reciprocally monophyletic.

   Microsatellite DNA loci revealed significant structure among sampled localities (globalF_st= 0.17,P< 0.001), with evidence of two distinct populations representing the Caddo and Ouachita rivers. However, Bayesian phylogeographical analyses resulted in three distinct clades: Caddo River, Ouachita River, and Mazarn Creek. Divergence from the most recent ancestor shared among the river drainages was estimated at 60 Kya. Population genetic diversity was relatively low (H_e= 0.65; mean alleles per locus,A= 6.26), but was comparable with the population genetic diversity found in the close relatives slackwater darter,Etheostoma boschungi(H_e= 0.65;A= 6.74), and Tuscumbia darter,Etheostoma tuscumbia(H_e= 0.57;A= 5.53).

   These results have conservation implications for paleback darter populations and can be informative for other headwater specialist species. Like other headwater species with population structuring and relatively low genetic diversity, the persistence of paleback darter populations is likely to be tied to the persistence and connectivity of local breeding and non‐breeding habitat. These results do not raise conservation concern for a population decline; however, the restricted distribution and endemic status of the species still renders paleback darter populations vulnerable to extirpation or extinction.

    

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