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Understanding patterns and mechanisms underlying local adaptation is becoming increasingly important for species conservation amid anthropogenically driven environmental change. Alpine systems are experiencing particularly intense pressure from environmental change resulting from increased rates of warming and corresponding loss of snow and ice. We integrate morphological and genetic analyses to identify traits important for local adaptation in one of the highest elevation breeding birds in North America, the Sierra Nevada Gray-crowned Rosy Finch. We performed an in-depth analysis of how traits with known links to thermoregulation in birds such as wing length, bill size, and feather microstructure vary between two populations at sites with contrasting climate and environmental conditions. We identified loci underlying these traits using a genome-wide association study and further examined regions of the genome related to altitude adaptation and cold tolerance using F ST outlier tests. Together, these results indicate that temperature, food availability, and alpine landscape features may impose multifaceted and potentially conflicting selective pressures on morphological traits important to adaptation in alpine birds. Overall, this work represents one of the first in-depth analyses of the genetic basis of adaptation in an alpine specialist songbird. 

Microplastics are widespread in the environment, including in the bodies of freshwater fish, with their concentrations influenced by factors such as proximity to point sources, such as wastewater treatment plants (WWTPs), and trophic level. However, few studies have simultaneously assessed the combined effects of these factors on microplastic abundance in urban stream fish. To do so, we measured microplastics and assessed trophic level via N stable isotope (δ15N) content in 6 species of small-bodied fishes (species = Lepomis macrochirus Rafinesque, 1819, Neogobius melanostomus [Pallas, 1814], Fundulus notatus [Rafinesque, 1820], Pimephales notatus [Rafinesque, 1820], Notemigonus crysoleucas [Mitchill, 1814], and Dorosoma cepedianum [Lesueur, 1818]) collected upstream, at, and downstream of a large WWTP in Chicago, Illinois, USA. Additionally, we analyzed stomach contents for 2 of these species (L. macrochirus and N. melanostomus). Four of the six species exhibited δ15N enrichment at and downstream of the WWTP, indicating prolonged residence times at the study sites (i.e., several weeks). Stomach contents of the 2 species measured supported this pattern, showing high chironomid consumption at the WWTP and variable stomach contents elsewhere. For microplastics, 1 species had higher concentrations near the WWTP, but microplastic concentrations did not differ among locations in the other 5 species. We found no evidence of a relationship between δ15N enrichment and microplastic concentration. Overall, the stable isotope and stomach content results suggest a strong relationship of WWTP effluent with fish diet but not with microplastic concentrations in fish. The results suggest that microplastic concentrations in fish is are shaped by interacting, species-specific factors including behavior (i.e., movement and foraging) and physiology (i.e., egestion rates and feeding mechanisms), in addition to proximity to point sources. Our study highlights the complexity of microplastic infiltration into food webs and underscores the need for further research to disentangle the drivers of microplastic accumulation in aquatic organisms. 

Abstract Flexible parental care strategies are widespread in nature and factor into conflict between the sexes and the realization of sex roles. While adaptive explanations abound, the mechanisms underlying flexible ‘sex-reversal’ of care are less clear. We enlist a biparental frog (Ranitomeya imitator) with flexible parental care to investigate the extrinsic and intrinsic mechanisms underpinning parental decisions. Using mate removal experiments in the laboratory, we show that members of the primary caregiving sex (males) show less variation than the flexible sex (females) in their propensity to provide care and that care propensity in females is affected by extrinsic partner cues as well as individual variability. Indeed, individual repeatability in parental effort is high in both typically caregiving and flexible parents. To investigate the underpinnings of differences in care propensity, we sequenced RNA from whole brains of caregiving and non-caregiving frogs of both sexes. While actively caregiving females showed minimal differential gene expression compared to actively caregiving males, females that failed to provide care showed distinct patterns of gene expression. Our findings offer an initial glimpse into the environmental and genetic regulation of individual variation in sex-reversed parental care.