Summary from the authors: landscape genetics of eastern indigo snakes

Landscape features, such as land use, vegetation cover, roads, and topography, strongly influence genetic connectivity yet these relationships can vary across spatial scales which therefore requires multi-scale approaches for evaluating landscape genetics relationships. We used the federally threatened eastern indigo snake (Drymarchon couperi), a terrestrial habitat generalist endemic to the southeastern United States, as a case study with which to evaluate the consequences of different approaches for accounting for spatial scale when optimizing genetics resistance surfaces using the software ResistanceGA. Resistance surfaces with scale selected using a true optimization approach simultaneously comparing all possible combinations of scale across each set of covariates performed better than resistance surfaces where scale was selected individually for each covariate. Truly optimized resistance surfaces also outperformed resistance surfaces based on habitat selection models and categorical land cover maps. Optimal scales were usually larger than average indigo snake home range sizes suggesting that gene flow was mediated mostly by extra-home range dispersal. Large tracts of undeveloped upland habitat with intermediate habitat heterogeneity most promoted indigo snake gene flow while roads did not appear to restrict gene flow. Our results show the importance of testing a wide range of spatial scales in landscape genetics studies. 

The top-ranked optimized genetic resistance surfaces for eastern indigo snakes in central Florida from (a) categorical land cover surfaces, (b) multi-scale habitat selection models, and (c) multi-scale landscape covariates selected using a true optimization approach. (d) shows an average resistance surface across our best-supported truly optimized resistance surfaces. (Figure 6 from Bauder et al. 2021.)

Article: Bauder JM, Peterman WE, Spear SF, Jenkins CL, Whiteley AR, McGarigal K. 2021. Multiscale assessment of functional connectivity: Landscape genetics of eastern indigo snakes in an anthropogenically fragmented landscape in central Florida. Molecular Ecology https://doi.org/10.1111/mec.15979.

Summary from the authors: inbreeding and management in captive populations

Pacific salmon hatcheries aim to supplement declining wild populations and support commercial and recreational fisheries. However, there are also risks associated with hatcheries because the captive and wild environments are inherently different. It is important to understand these risks in order to maximize the success of hatcheries. Inbreeding, which occurs when related individuals interbreed, is one risk that may inadvertently be higher in hatcheries due to space limitations and other factors. Inbred fish may have reduced fitness and survival compared to non-inbred fish. We quantified inbreeding and its effect on key fitness traits across four generations in two hatchery populations of adult Chinook salmon that were derived from the same source. We utilized recent advancements in DNA sequencing technology, which provide much more precise estimates of inbreeding and its potential effects on fitness. Our results indicate that inbreeding may not be severe in salmon hatcheries, even small ones, provided that appropriate management practices are followed. However, we documented an influence of inbreeding on the phenology of adult spawners, which could have biological implications for individual fitness and population productivity. Our findings provide a better understanding of changes that may occur in hatchery salmon and will further inform research on “best” hatchery practices to minimize potential risks. 

Article: Waters CD, Hard JJ, Fast DE, Knudsen CM, Bosch WJ, Naish KA. 2020. Genomic and phenotypic effects of inbreeding across two different hatchery management regimes in Chinook salmon. Molecular Ecology https://doi.org/10.1111/mec.15356.