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Disentangling the contemporary and historical factors underlying the spatial distributions of species is a central goal of biogeography. For species with broad distributions but little capacity to actively disperse, disconnected geographical distributions highlight the potential influence of passive, long-distance dispersal (LDD) on their evolutionary histories. However, dispersal alone cannot completely account for the biogeography of any species, and other factors-e.g. habitat suitability, life history-must also be considered. North American ice worms ( Mesenchytraeus solifugus) are ice-obligate annelids that inhabit coastal glaciers from Oregon to Alaska. Previous studies identified a complex biogeographic history for ice worms, with evidence for genetic isolation, unexpectedly close relationships among geographically disjunct lineages, and contemporary migration across large (e.g. greater than 1500 km) areas of unsuitable habitat. In this study, we analysed genome-scale sequence data for individuals from most of the known ice worm range. We found clear support for divergence between populations along the Pacific Coast and the inland flanks of the Coast Mountains (mean FST = 0.60), likely precipitated by episodic ice sheet expansion and contraction during the Pleistocene. We also found support for LDD of ice worms from Alaska to Vancouver Island, perhaps mediated by migrating birds. Our results highlight the power of genomic data for disentangling complex biogeographic patterns, including the presence of LDD.

Expansion of an invasive Lake Trout Salvelinus namaycush population in Swan Lake, Montana, threatens a core area population of Bull Trout S. confluentus. Given the recent development of novel suppression methods, such as use of carcass analog pellets to cause high mortality of embryos, there was a need to quantify spawning season aggregation sites, site use, and spawning habitat for Lake Trout in Swan Lake. Acoustic tags were implanted in 85 Lake Trout during the summer in 2018 and 2019. Nightly tracking efforts during autumn in both years resulted in 1,744 relocations for 49 individual Lake Trout. Kernel density analysis was used to evaluate Lake Trout aggregation sites, identifying 10 distinct sites. All spawning sites were located in the littoral zone along areas of steep bathymetric relief, and these sites composed 48% of total relocations during both spawning seasons. In 2019, side‐scan sonar imaging was used to classify and quantify the total area of spawning substrate, which constituted 12.8% of the total surface area estimated for spawning sites 1, 6, and 9 and 11.4% of the total surface area for aggregation sites 2–5, 7, 8, and 10. Simultaneous treatment of all spawning sites would require 205,709 ± 86 kg of carcass analog pellet material, resulting in 370.4 ± 0.2 kg of phosphorus inputs and 7,487.9 ± 3.1 kg of nitrogen inputs to Swan Lake. Thus, pellet treatment would increase the Carlson's trophic state index (TSI) values from 20.8 to 27.7 for total phosphorus and from 22.1 to 26.2 for total nitrogen. Based on a TSI threshold of less than 40 for an oligotrophic lake, the use of carcass analog pellets could be feasible for supplementing the gill‐netting suppression of Lake Trout in Swan Lake. [ABSTRACT FROM AUTHOR]

Choosing an aquatic invertebrate sampling method for biomonitoring depends upon study goals, resources, and ecosystem conditions. In this study, we compared two methods that are widely used in stream ecology, but have not been directly compared: Hester–Dendy (HD) and Hess sampling. Hester–Dendy sampling uses artificial substrate that invertebrates colonize over a specific period of time. In contrast, Hess samplers surround a fixed area of natural substrate with a net. To compare approaches, we combined 5 years of simultaneous HD and Hess data collection (2010–2014) from the Niobrara River with a 14-year (1996–2009) historical HD data set for the same study sites. We used this full 19-year data set to assess how ecosystem health has changed in the Niobrara River over time, while also testing the influence of HD versus Hess data (2010–2014) on historical trends (1996–2009). Our results showed that HD samples are more taxonomically variable and bias bioassessment metrics because they collect more sensitive taxa versus Hess sampling. However, when combined with the 1996–2009 HD data set, both recent HD and Hess data sets recovered the same trend of declining ecosystem health in the Niobrara River. These results provide empirical evidence that even when historical HD data are combined with recent Hess data, long-term bioassessment trends remain unchanged despite more accurate perspectives of invertebrate assemblages being collected.

Comparative population genetic studies provide a powerful means for assessing the degree to which evolutionary histories may be congruent among taxa while also highlighting the potential for cryptic diversity within existing species.In the Rocky Mountains, three confamilial stoneflies (Zapada glacier, Lednia tumana, and Lednia tetonica; Plecoptera, Nemouridae) occupy cold alpine streams that are primarily fed by melting ice. Lednia tumana and L. tetonica are sister species diagnosed from systematic morphological differences, and they are endemic to areas surrounding Glacier National Park and Grand Teton National Park, respectively, in the U.S. Rocky Mountains. Zapada glacier is also present in alpine streams from Glacier National Park to the Teton Range, sometimes co‐occurring with either Lednia species.We used mitochondrial sequence data to clarify species boundaries, compare population genetic patterns, and test demographic models in a coalescent framework for the three stoneflies. We addressed four questions: (1) Is there genetic support for the morphology‐based species boundaries in Lednia? (2) Is there genetic support for cryptic, or as‐yet undescribed, diversity within Z. glacier? (3) Do similar geographic distributions and ecological requirements yield spatial congruence of genetic structure between high‐elevation Lednia and Z. glacier populations? (4) Is there evidence for contemporary gene flow among isolated populations in either group?Our results supported the existing taxonomy with Z. glacier and the two Lednia species differing in their depths of divergence among study regions (e.g. maximum sequence divergence within Z. glacier = 1.2% versus 5% between L. tumana and L. tetonica). However, spatial population genetic patterns were broadly congruent, indicating stonefly populations isolated on mountaintop islands. Coalescent modelling supported the possibility of rare, extremely limited contemporary gene flow among Z. glacier populations, with no support for gene flow between L. tumana and L. tetonica.The focal stoneflies and associated assemblages occupy the highest elevation, coldest permanent alpine streams in the study region. This lotic habitat type faces an uncertain future under a diminishing alpine cryosphere. Given spatial congruence of genetic structure demonstrating unique biodiversity associated with individual alpine islands, we encourage conservation management strategies be developed and applied at corresponding spatial scales. [ABSTRACT FROM AUTHOR]