Informed breeding dispersal following stochastic changes to patch quality in a pond‐breeding amphibian

Abstract

The unidirectional movement of animals between breeding patches (i.e. breeding dispersal) has profound implications for the ecological and evolutionary dynamics of spatially structured populations. In spatiotemporally variable environments, individuals are expected to adjust their dispersal decisions according to information gathered on the environmental and/or social cues that reflect the fitness prospects in a given breeding patch (i.e. informed dispersal). A paucity of empirical work limited our understanding of the ability of animals to depart from low‐quality breeding patches and settle in high‐quality breeding patches. We examined the capacity of individuals to respond to stochastic changes in habitat quality via informed breeding dispersal in a pond‐breeding amphibian. We conducted a 5‐year (2015–2019) capture–recapture study of boreal toads Anaxyrus boreas boreas (n = 1,100) that breed in beaver ponds in western Wyoming, USA. During early spring of 2017, an extreme flooding event destroyed several beaver dams and resulted in the loss of breeding habitat. We used multi‐state models to investigate how temporal changes in pond characteristics influenced breeding dispersal, and determine whether movement decisions were in accordance with prospects for reproductive fitness. Boreal toads more often departed from low‐quality breeding ponds (without successful metamorphosis) and settled in high‐quality breeding ponds (with successful metamorphosis). Movement decisions were context‐dependent and associated with pond characteristics altered by beaver dam destruction. Individuals were more likely to depart from shallow ponds with high vegetation cover and settle in deep ponds with low vegetation cover. The probability of metamorphosis was related to the same environmental cues, suggesting that boreal toads assess the fitness prospects of a breeding patch and adjust movement decisions accordingly (i.e. informed breeding dispersal). We demonstrated that stochastic variability in environmental conditions and habitat quality can underpin dispersal behaviour in amphibians. Our study highlighted the mechanistic linkages between habitat change, movement behaviour and prospects for reproductive performance, which is critical for understanding how wild animals respond to rapid environmental change.

Context‐dependent dispersal determines relatedness and genetic structure in a patchy amphibian population

“…Overall, our study and previous work (Barrile et al, 2021; Boualit et al, 2019; Tournier et al, 2017) suggest that amphibians adjust their dispersal decisions according to environmental and/or social cues reflecting local fitness prospects in the aquatic patches used for reproduction (Cayuela, Valenzuela‐Sánchez, et al, 2020). Those results are congruent with the conclusions drawn by a growing number of studies on vertebrates and invertebrates that show dispersal to be a plastic phenotypic trait (Saastamoinen et al, 2018) allowing organisms to respond to the spatiotemporal heterogeneity of their habitat in fragmented landscapes (Baguette et al, 2013; Cote et al, 2017; Hendrix et al, 2017).…”

“…Overall, our study and previous work (Barrile et al, 2021;Boualit et al, 2019;Tournier et al, 2017) suggest that amphibians adjust their dispersal decisions according to environmental and/or social cues reflecting local fitness prospects in the aquatic patches used for reproduction (Cayuela, Valenzuela-Sánchez, et al, 2020).…”

Wildfire influences individual growth and breeding dispersal, but not survival and recruitment in a montane amphibian

“…Recruitment of boreal toads also was not influenced by wildfire during our study period. We expected recruitment via immigration into our study area given that boreal toad dispersal tends to increase post‐disturbance (Barrile, Walters, et al, 2021; Crisafulli et al, 2005) and fire‐induced habitat changes likely increased landscape permeability (Rochester et al, 2010). Many of the breeding ponds within our study streams were degraded from spring flooding during 2017, however, such that emigration out of our system may have been more common than immigration into our system.…”

“…Efforts to maintain beaver populations in our system may help protect riparian habitat from fire‐induced habitat changes, as beaver‐dammed riparian corridors remain relatively unaffected by wildfire compared with corridors without beaver damming (Fairfax & Whittle, 2020). Finally, wildfire also may interact with other key disturbances in our system, including extreme flooding and livestock grazing, both of which can influence riparian habitat and the quality of breeding ponds (Barrile, Walters, et al, 2021; Barrile, Walters, & Chalfoun, 2022; Fesenmyer et al, 2018). Determining how wildfire, grazing, and flooding independently and interactively influence the quality of breeding ponds and the dispersal pathways between them likely will be critical for predicting how boreal toads will respond in an uncertain future.…”

“…During the early spring of 2017, high snowmelt runoff destroyed beaver dams within our core study reaches, which degraded the quality of breeding habitat at many of our primary sites (Barrile, Walters, et al, 2021). Because boreal toad dispersal can increase following wildfire (Hossack & Corn, 2007; Hossack, Lowe, & Corn, 2013), we predicted that fire‐induced habitat changes (e.g., increased landscape permeability; Rochester et al, 2010) and/or enhanced growth would provide individuals the opportunity to depart low‐quality breeding ponds (i.e., primary sites) and colonize alternative breeding ponds (hereafter, alternative sites) outside of our core study area (e.g., areas with recent beaver activity).…”