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1. Spatiotemporal patterns of emergence phenology reveal complex species‐specific responses to temperature in aquatic insects

   https://doi.org/10.1111/ddi.13472  

   Finn, Debra S. ; Johnson, Sherri L. ; Gerth, William J. ; Arismendi, Ivan ; Li, Judith L. ; Bates, ed., Amanda ( January 2022 , Diversity and Distributions)

   Climate change is broadly affecting phenology, but species‐specific phenological response to temperature is not well understood. In streams, insect emergence has important ecosystem‐level consequences because emergent adults link aquatic and terrestrial food webs. We quantified emergence timing and duration (within‐population synchronicity) of insects among streams along a spatiotemporal gradient of mean water temperature in a montane basin to assess the sensitivity of these phenological traits to heat accumulation from mid‐winter through spring emergence periods.

   Six headwater streams in the Lookout Creek basin, H.J. Andrews Experimental Forest, Oregon, USA.

   We collected emerging adults of four abundant insect species twice weekly throughout spring for 6 consecutive years. We fit Gaussian models to the empirical temporal distributions to characterize peak emergence timing (mean) and duration (days between 5th and 95th percentiles) for each species/stream/year combination. We then quantified relationships between degree‐day accumulation and phenological response.

   Only one of the four species (a caddisfly) showed a simple response of earlier emergence timing in both warmer streams and years. One stonefly had lengthy emergence periods resulting in substantial phenological overlap between warmer and cooler streams/years. Interestingly, two species (a mayfly and a stonefly) responded strongly to temporal (interannual) temperature differences but minimally to spatial differences, indicating that emergence was nearly synchronous among streams, within years. These two species had among‐stream differences approaching 500 degree‐days from mid‐winter to peak emergence. Conversely, duration of emergence was more strongly associated with spatial than temporal differences, with longer duration in lower‐elevation (warmer) streams.

   Emergence phenology has species‐specific responses to temperature likely driven by complex cues for diapause or quiescence periods during preceding life cycle stages. We hypothesize a trade‐off between complex phenological response that synchronizes emergence among heterogeneous sites and other traits such as adult longevity and dispersal capacity.

    

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2. Drift happens: Molecular genetic diversity and differentiation among populations of jewelweed ( Impatiens capensis Meerb.) reflect fragmentation of floodplain forests

   https://doi.org/10.1111/mec.15072  

   Toczydlowski, Rachel H. ; Waller, Donald M. ( May 2019 , Molecular Ecology)

   Landscape features often shape patterns of gene flow and genetic differentiation in plant species. Populations that are small and isolated enough also become subject to genetic drift. We examined patterns of gene flow and differentiation among 12 floodplain populations of the selfing annual jewelweed (Impatiens capensisMeerb.) nested within four river systems and two major watersheds in Wisconsin, USA. Floodplain forests and marshes provide a model system for assessing the effects of habitat fragmentation within agricultural/urban landscapes and for testing whether rivers act to genetically connect dispersed populations. We generated a panel of 12,856 single nucleotide polymorphisms and assessed genetic diversity, differentiation, gene flow, and drift. Clustering methods revealed strong population genetic structure with limited admixture and highly differentiated populations (mean multilocusF_ST = 0.32,F_ST’ = 0.33). No signals of isolation by geographic distance or environment emerged, but alleles may flow along rivers given that genetic differentiation increased with river distance. Differentiation also increased in populations with fewer private alleles (R² = 0.51) and higher local inbreeding (R² = 0.22). Populations varied greatly in levels of local inbreeding (F_IS = 0.2–0.9) andF_ISincreased in more isolated populations. These results suggest that genetic drift dominates other forces in structuring theseImpatienspopulations. In rapidly changing environments, species must migrate or genetically adapt. Habitat fragmentation limits both processes, potentially compromising the ability of species to persist in fragmented landscapes.

    

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3. Conservation genetics and breeding system of Penstemon debilis (Plantaginaceae), a rare beardtongue endemic to oil shale talus in western Colorado, USA

   https://doi.org/10.1111/jse.12100  

   WOLFE, Andrea D. ; MCMULLEN‐SIBUL, Amy ; TEPEDINO, V. J. ; KUBATKO, Laura ; NECAMP, Timothy ; FASSNACHT, Susan ( May 2014 , Journal of Systematics and Evolution)

   Rare species of plants are especially vulnerable to extinction when populations are few, have small numbers of individuals, and are fragmented. Such conditions lead to a reduction in gene flow and genetic diversity, and encourage inbreeding depression. We conducted a study of the reproductive biology and population genetics ofPenstemon debilis(Plantaginaceae), a Federally Threatened species endemic to a small region of oil shale extraction in western Colorado, USA. Most of the habitat area is privately owned and undergoing natural gas extraction activities.Penstemon debilisreproduces both vegetatively and as an outcrosser that requires a pollen vector. Moderate levels of inbreeding, but no inbreeding depression, were found within populations ofP. debilis. Genetic divergence among the extant populations surveyed was moderate (F_STvalues = 0.069–0.231;Nm = 0.831–3.385) with levels of genetic diversity within populations relatively low compared to congeners with similar modes of pollination and reproductive biology. STRUCTURE analysis revealed three population clusters with some admixture among all extant populations. Genetic diversity within and amongP. debilispopulations is similar to genetic diversity found for other rare and endemic outcrossing plant species. Our results are consistent with a pattern of recent population fragmentation or low levels of pollen‐mediated gene flow among populations in close proximity to one another. Conservation ofP. debiliswill require cooperative management strategies between private landowners, government agencies, and concerned NGOs to preserve habitat for this rare species.

    

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4. Urbanization mediates the effects of water quality and climate on a model aerial insectivorous bird

   https://doi.org/10.1002/ecm.1442  

   Sullivan, S. Mažeika P. ; Corra, Joseph W. ; Hayes, Jeffry T. ( February 2021 , Ecological Monographs)

   Aerial insectivorous birds have experienced alarming population declines in eastern North America. Meanwhile, urbanization continues to increase rapidly, with urban land use comprising 69.4 million acres (1 acre = 0.40 ha), or 3.6% of total land area, in the contiguous United States. Multiple environmental changes are associated with urbanization, including alterations to local climate, changes in habitat structure, and potential shifts in both terrestrial and emergent aquatic flying insects on which aerial insectivorous birds rely. Here, we investigated the linkages between urbanization, water quality, and Tree Swallow (Tachycineta bicolor) reproductive success and body condition at seven river‐riparian sites representing urban and protected land use in Columbus, Ohio (USA) over five consecutive years (2014–2018). Tree Swallows at urban and protected sites relied on emergent aquatic insects for 37.4% and 30.8% (SD = 28.4% and 24.1%) of their nutritional subsidies, respectively. Despite the loss of environmental quality generally attributed to cities, Tree Swallows exhibited greater reproductive success in urban settings where climate was more amenable to egg and nestling survival, and the breeding season was longer. Urban‐nesting Tree Swallows initiated laying 7.9 d earlier and fledged 35% more young per nest than those at protected sites. Multiple characteristics of urban sites appeared to drive these patterns, including differences in mean and extreme air temperatures and measures of water quality (e.g., water temperature, nutrient concentrations, turbidity). However, chronic effects of elevated Hg concentrations, which were 482% greater in adult swallow blood at urban sites than at protected sites where swallows exhibited a 17.4% lower trophic position, may disadvantage individuals in other ways. Further, although Tree Swallows are a good model aerial insectivore bird species, characteristics of urban landscapes that benefit Tree Swallows may not advantage other aerial insectivorous birds owing to differences in life‐history and foraging strategies. These findings implicate urbanization, local climate, and water quality as important considerations in the conservation of aerial insectivorous birds.

    

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5. Genetic structure across urban and agricultural landscapes reveals evidence of resource specialization and philopatry in the Eastern carpenter bee, Xylocopa virginica L.

   https://doi.org/10.1111/eva.13078  

   Ballare, Kimberly M. ; Jha, Shalene ( August 2020 , Evolutionary Applications)

   Human activity continues to impact global ecosystems, often by altering the habitat suitability, persistence, and movement of native species. It is thus critical to examine the population genetic structure of key ecosystemservice providers across human‐altered landscapes to provide insight into the forces that limit wildlife persistence and movement across multiple spatial scales. While some studies have documented declines of bee pollinators as a result of human‐mediated habitat alteration, others suggest that some bee species may benefit from altered land use due to increased food or nesting resource availability; however, detailed population and dispersal studies have been lacking. We investigated the population genetic structure of the Eastern carpenter bee,Xylocopa virginica,across 14 sites spanning more than 450 km, including dense urban areas and intensive agricultural habitat.X. virginicais a large bee which constructs nests in natural and human‐associated wooden substrates, and is hypothesized to disperse broadly across urbanizing areas. Using 10 microsatellite loci, we detected significant genetic isolation by geographic distance and significant isolation by land use, where urban and cultivated landscapes were most conducive to gene flow. This is one of the first population genetic analyses to provide evidence of enhanced insect dispersal in human‐altered areas as compared to semi‐natural landscapes. We found moderate levels of regional‐scale population structure across the study system (Gʹ_ST = 0.146) and substantial co‐ancestry between the sampling regions, where co‐ancestry patterns align with major human transportation corridors, suggesting that human‐mediated movement may be influencing regional dispersal processes. Additionally, we found a signature of strong site‐level philopatry where our analyses revealed significant levels of high genetic relatedness at very fine scales (<1 km), surprising givenX. virginica'slarge body size. These results provide unique genetic evidence that insects can simultaneously exhibit substantial regional dispersal as well as high local nesting fidelity in landscapes dominated by human activity.

    

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