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Abstract Across taxa, individuals vary in how far they disperse, with most individuals staying close to their origin and fewer dispersing long distances. Costs associated with dispersal (e.g., energy, risk) are widely believed to trade off with benefits (e.g., reduced competition, increased reproductive success) to influence dispersal propensity. However, this framework has not been applied to understand variation in dispersal distance, which is instead generally attributed to extrinsic environmental factors. We alternatively hypothesized that variation in dispersal distances results from trade‐offs associated with other aspects of locomotor performance. We tested this hypothesis in the stream salamanderGyrinophilus porphyriticusand found that salamanders that dispersed farther in the field had longer forelimbs but swam at slower velocities under experimental conditions. The reduced swimming performance of long‐distance dispersers likely results from drag imposed by longer forelimbs. Longer forelimbs may facilitate moving longer distances, but the proximate costs associated with reduced swimming performance may help to explain the rarity of long‐distance dispersal. The historical focus on environmental drivers of dispersal distances misses the importance of individual traits and associated trade‐offs among traits affecting locomotion.
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Long‐term survival probability, not current habitat quality, predicts dispersal distance in a stream salamander
Abstract Dispersal evolves as an adaptive mechanism to optimize individual fitness across the landscape. Specifically, dispersal represents a mechanism to escape fitness costs resulting from changes in environmental conditions. Decades of empirical work suggest that individuals use local habitat cues to make movement decisions, but theory predicts that dispersal can also evolve as a fixed trait, independent of local conditions, in environments characterized by a history of stochastic spatiotemporal variation. Until now, however, both conditional and fixed models of dispersal evolution have primarily been evaluated using emigration data (stay vs. leave), and not dispersal distances: a more comprehensive measure of dispersal. Our goal was to test whether conditional or fixed models of dispersal evolution predict variation in dispersal distance in the stream salamanderGyrinophilus porphyriticus.We quantified variation in habitat conditions using measures of salamander performance from 4 yr of spatially explicit, capture–mark–recapture (CMR) data across three headwater streams in the Hubbard Brook Experimental Forest in central New Hampshire, USA. We used body condition as an index of local habitat quality that individuals may use to make dispersal decisions, and survival probability estimated from multistate CMR models as an index of mortality risk resulting from the long‐term history of environmental variation. We found that dispersal distances increased with declining survival probability, indicating that salamanders disperse further in risky environments. Dispersal distances were unrelated to spatial variation in body condition, suggesting that salamanders do not base dispersal distance decisions on local habitat quality. Our study provides the first empirical support for fixed models of dispersal evolution, which predict that dispersal evolves in response to a history of spatiotemporal environmental variation, rather than as a conditional response to current habitat conditions. More broadly, this study underscores the value of assessing alternative scales of environmental variation to gain a more complete and balanced understanding of dispersal evolution.
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- Award ID(s):
- 1655653
- PAR ID:
- 10456589
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Ecology
- Volume:
- 101
- Issue:
- 4
- ISSN:
- 0012-9658
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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{"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."]}more » « less
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