Search for: All records

We lack a strong understanding of how organisms with complex life histories respond to climate variation. Many stream-associated species have multi-stage life histories that are likely to influence the demographic consequences of floods and droughts. However, tracking stage specific demographic responses requires high-resolution, long-term data that are rare. We used eight years of capture-recapture data for the headwater stream salamander Gyrinophilus porphyriticus to quantify the effects of flooding and drying magnitude on stage-specific vital rates and population growth. Drying reduced larval recruitment but increased the probability of metamorphosis (i.e., adult recruitment). Flooding reduced adult recruitment but had no effect on larval recruitment. Larval and adult survival declined with flooding but were unaffected by drying. Annual population growth rates (lambda, ) declined with flooding and drying. Lambda also declined over the study period (2012 – 2021), although mean  was 1.0 over this period. Our results indicate that G. porphyriticus populations are resilient to hydrologic variation due to compensatory effects on recruitment of larvae vs. adults (i.e., reproduction vs. metamorphosis). Complex life cycles may enable this resilience to climate variation by creating opportunities for compensatory demographic responses across stages. However, more frequent and intense hydrologic variation in the latter half of this study contributed to a decline in  over time, suggesting that increasing environmental variability poses a threat even when demographic compensation occurs. 

This project was designed to describe fine-scale population genetic differentiation of the stream salamander Gryinophilus porphyriticus among five study streams in the Hubbard Brook Experimental Forest. The data are paired with intensive capture-recapture data to assess direct fitness effects of individual genetic diversity, including effects of individual multilocus heterozygosity on stage-specific survival probabilities. This dataset publishes a manifest of the genomic sequence reads submitted to the National Center for Biotechnology Information (NCBI) Sequence Read Archive (SRA). These samples are published at NCBI under the BioProject ID 1090913 (https://www.ncbi.nlm.nih.gov/bioproject/1090913). The tables here include sample metadata and the NCBI URLs to each sample. These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station. 

Abstract Assessing direct fitness effects of individual genetic diversity is challenging due to the intensive and long‐term data needed to quantify survival and reproduction in the wild. But resolving these effects is necessary to determine how inbreeding and outbreeding influence eco‐evolutionary processes. We used 8 years of capture–recapture data and single nucleotide polymorphism genotypes for 1906 individuals to test for effects of individual heterozygosity on stage‐specific survival probabilities in the salamanderGyrinophilus porphyriticus. The life cycle ofG. porphyriticusincludes an aquatic larval stage followed by metamorphosis into a semi‐aquatic adult stage. In our study populations, the larval stage lasts 6–10 years, metamorphosis takes several months, and lifespan can reach 20 years. Previous studies showed that metamorphosis is a sensitive life stage, leading us to predict that fitness effects of individual heterozygosity would occur during metamorphosis. Consistent with this prediction, monthly probability of survival during metamorphosis declined with multi‐locus heterozygosity (MLH), from 0.38 at the lowest MLH (0.10) to 0.06 at the highest MLH (0.38), a reduction of 84%. Body condition of larvae also declined significantly with increasing MLH. These relationships were consistent in the three study streams. With evidence of localised inbreeding within streams, these results suggest that outbreeding disrupts adaptations in pre‐metamorphic and metamorphic individuals to environmental gradients along streams, adding to evidence that headwater streams are hotspots of microgeographic adaptation. Our results also underscore the importance of incorporating life history in analyses of the fitness effects of individual genetic diversity and suggest that metamorphosis and similar discrete life stage transitions may be critical periods of viability selection. 

This data set includes spatially explicit mark-recapture data of the Northern Spring Salamander (Gyrinophilus porphyriticus) collected via telemetry during the summer months (June – September) from 2019 - 2021 from eight reaches in multiple streams in the Hubbard Brook Experimental Forest. Salamanders were captured by hand and marked with PIT-tags. Telemetry surveys occurred weekly. These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station. These data are being used to publish the following papers: Cochrane, M. M., B. R. Addis, L. K. Swartz, and W. H. Lowe. 2023. Individual and population growth rates decline with watershed area in a stream salamander. In review Ecology. Cochrane, M. M., and W. H. Lowe. 2023. Floods increase downstream movement of adult and larval life stages of a headwater stream salamander. In prep Freshwater Biology. 

This dataset includes spatially explicit mark-recapture data of the Northern Spring Salamander (Gyrinophilus porphyriticus) collected during the summer months (June – August) from downstream and upstream reaches in multiple streams in the Hubbard Brook Experimental Forest. Downstream reaches begin at the confluence with the Main Hubbard and extend upstream 500 meters and upstream reaches begin at the weir and extend downstream 500 meters. Downstream reaches contain brook trout and upstream reaches do not. We used a robust design framework with 9 surveys per reach each summer (3 primary occasions with 3 secondary occasions each). Salamanders were captured by hand and marked with either Visual Implant Elastomer and/or a PIT tag. The data table herein is specific to the following publication: Lowe, W.H., B.R. Addis, M.M. Cochrane, and L.K. Swartz. In press. Source-sink dynamics within a complex life history. Ecology. These data are a subset of the primary long term dataset available at https://doi.org/10.6073/pasta/cd5f5a03df194930bf87eb12157b8182 These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station. 

{"Abstract":["This data set includes spatially explicit mark-recapture data of the\nNorthern Spring Salamander (Gyrinophilus porphyriticus) collected during\nthe summer months (June \u2013 August) from downstream and upstream reaches\nin multiple streams in the Hubbard Brook Experimental Forest. Downstream\nreaches begin at the confluence with the Main Hubbard and extend\nupstream 500 meters and upstream reaches begin at the weir and extend\ndownstream 500 meters. Downstream reaches contain brook trout and\nupstream reaches do not. We used a robust design framework with\napproximately 9 surveys per reach each summer (3 primary occasions with\n3 secondary occasions each). Salamanders were captured by hand and\nmarked with either Visual Implant Elastomer and/or a PIT tag.\n These data were gathered as part of the Hubbard Brook Ecosystem Study\n(HBES). The HBES is a collaborative effort at the Hubbard Brook\nExperimental Forest, which is operated and maintained by the USDA Forest\nService, Northern Research Station.\n These data have been published in the following papers: \n Lowe WH, Addis\nBR, Smith MR, Davenport JM. The spatial structure of variation in\nsalamander survival, body condition and morphology in a headwater stream\nnetwork. Freshwater Biol. 2018;63:1287\u20131299.\nhttps://doi.org/10.1111/fwb.13133\n Lowe, W. H., and Addis, B. R.. 2019. Matching habitat choice and plasticity contribute to phenotype\u2013environment covariation in a stream salamander. Ecology 100( 5):e02661. 10.1002/ecy.2661 \n Lowe, W.H., et al. Hydrologic variability contributes to reduced survival through metamorphosis in a stream salamander. Proceedings of the National Academy of Sciences 2019; 116.39: 19563-19570.\n Bryant, A.R., Gabor, C.R., Swartz, L.K., Wagner, R., Cochrane, M.M., Lowe, W.H. Differences in corticosterone release rates of larval Spring Salamanders (Gyrinophilus porphyriticus) in response to native fish presence. Biology 2022; 11.484. https://doi.org/10.3390/biology11040484\n Addis, B.R., and W.H. Lowe. Environmentally associated variation in dispersal distance affects inbreeding risk in a stream salamander." The American Naturalist 2022."]} 

Abstract A fundamental goal of ecology is to understand how the physical environment influences intraspecific variability in life history and, consequently, fitness. In streams, discharge and associated habitat conditions change along a continuum from intermittency to permanence: Headwater streams typically have smaller watersheds and are thus more prone to drying than higher‐order streams with larger watersheds and more consistent discharge. However, few empirical studies have assessed life history and associated population responses to this continuum in aquatic organisms. We tested the prediction that individual growth, rate of development, and population growth increase with watershed area in the long‐lived stream salamanderGyrinophilus porphyriticus, where we use watershed area as a proxy for hydrologic intermittence. To address this hypothesis, we used 8 years of mark–recapture data from 53 reaches across 10 headwater streams in New Hampshire, USA. Individual growth rates and mean size at metamorphosis increased with watershed area for watersheds from 0.12 to 1.66 km². Population growth rates increased with watershed area; however, this result was not statistically significant at our sample size. Mean age of metamorphosis did not vary across watershed areas. Lower individual growth rates and smaller sizes at metamorphosis likely contributed to reduced lifetime fecundity and population growth in reaches with the smallest watershed areas and highest vulnerability to drought. These responses suggest that as droughts increase due to climate change, headwater specialists in hydrologically intermittent environments will experience a reduction in fitness due to smaller body sizes or other growth‐related mechanisms. 

Invasive fish predators are an important factor causing amphibian declines and may have direct and indirect effects on amphibian survival. For example, early non-lethal exposure to these stressors may reduce survival in later life stages, especially in biphasic species. In amphibians, the glucocorticoid hormone corticosterone is released by the hypothalamo–pituitary–interrenal axis (HPI), as an adaptive physiological response to environmental stressors. The corticosterone response (baseline and response to acute stressors) is highly flexible and context dependent, and this variation can allow individuals to alter their phenotype and behavior with environmental changes, ultimately increasing survival. We sampled larvae of the spring salamander (Gyrinophilus porphyriticus) from two streams that each contained predatory brook trout (Slavelinus fontinalis) in the lower reaches and no predatory brook trout in the upper reaches. We measured baseline and stress-induced corticosterone release rates of larvae from the lower and upper reaches using a non-invasive water-borne hormone assay. We hypothesized that corticosterone release rates would differ between larvae from fish-present reaches and larvae from fish-free reaches. We found that baseline and stressor-induced corticosterone release rates were downregulated in larvae from reaches with fish predators. These results indicate that individuals from reaches with predatory trout are responding to fish predators by downregulating corticosterone while maintaining an active HPI axis. This may allow larvae more time to grow before metamorphosing, while also allowing them to physiologically respond to novel stressors. However, prolonged downregulation of corticosterone release rates can impact growth in post-metamorphic individuals.