Drought‐mediated extinction of an arid‐land amphibian: insights from a spatially explicit dynamic occupancy model

Abstract

Understanding how natural and anthropogenic processes affect population dynamics of species with patchy distributions is critical to predicting their responses to environmental changes. Despite considerable evidence that demographic rates and dispersal patterns vary temporally in response to an array of biotic and abiotic processes, few applications of metapopulation theory have sought to explore factors that explain spatiotemporal variation in extinction or colonization rates. To facilitate exploring these factors, we extended a spatially explicit model of metapopulation dynamics to create a framework that requires only binary presence–absence data, makes few assumptions about the dispersal process, and accounts for imperfect detection. We apply this framework to 22 yr of biannual survey data for lowland leopard frogs, Lithobates yavapaiensis, an amphibian that inhabits arid stream systems in the southwestern United States and northern Mexico. Our results highlight the importance of accounting for factors that govern temporal variation in transition probabilities, as both extinction and colonization rates varied with hydrologic conditions. Specifically, local extinctions were more frequent during drought periods, particularly at sites without reliable surface water. Colonization rates increased when larval and dispersal periods were wetter than normal, which increased the probability that potential emigrants metamorphosed and reached neighboring sites. Extirpation of frogs from all sites in one watershed during a period of severe drought demonstrated the influence of site‐level features, as frogs persisted only in areas where most sites held water consistently and where the amount of sediment deposited from high‐elevation wildfires was low. Application of our model provided novel insights into how climate‐related processes affected the distribution and population dynamics of an arid‐land amphibian. The approach we describe has application to a wide array of species that inhabit patchy environments, can improve our understanding of factors that govern metapopulation dynamics, and can inform strategies for conservation of imperiled species.

Regional and local effects drive changes in spawning stream occupancy in a sockeye salmon metapopulation

“…However, in years of poor reproductive success and low abundance, brood failures in streams with small populations and poor habitats occurred, and the metapopulation was restricted to streams with the best habitat, a pattern that has been observed in some other salmon metapopulations (Anlauf-Dunn et al 2014). The role of variation in habitat or patch quality in metapopulation dynamics is being increasingly recognized (Robles and Ciudad, 2012;Vanhaecke et al 2012), as are interactions of patch quality with broader scale factors associated with weather or climate (Grof-Tisza et al 2019;Zylstra et al 2019). Our result is also consistent with results from theoretical models that include limited colonization of unoccupied patches (Freckleton et al 2005).…”

A statistical forecasting approach to metapopulation viability analysis

“…, Zylstra et al. ). Another component of SMT is that the landscape structure in which patches are embedded influences colonization dynamics (Moilanen and Hanski ), yet statistical metapopulation models typically make the simplifying assumption that the landscape in which patches are embedded is homogenous, and colonization is only influenced by patch quality and the spatial distribution of patches (Risk et al.…”

“…, Zylstra et al. ). Recent advances in metapopulation models have made it possible to relax this assumption and allow researchers to draw inferences about the effects of landscape structure on colonization dynamics using empirical data (Howell et al.…”

“…However, recently developed statistical metapopulation models allow for spatiotemporal autocorrelation while accommodating process and sampling uncertainty (Risk et al 2011, Green et al 2013, Heard et al 2013, Sutherland et al 2014, Chandler et al 2015, Broms et al 2016, Williams et al 2017, Alcala et al 2018, Howell et al 2018, Laroche et al 2018, Zylstra et al 2019. Another component of SMT is that the landscape structure in which patches are embedded influences colonization dynamics (Moilanen and Hanski 1998), yet statistical metapopulation models typically make the simplifying assumption that the landscape in which patches are embedded is homogenous, and colonization is only influenced by patch quality and the spatial distribution of patches (Risk et al 2011, Green et al 2013, Heard et al 2013, Sutherland et al 2014, Chandler et al 2015, Broms et al 2016, Williams et al 2017, Alcala et al 2018, Laroche et al 2018, Zylstra et al 2019. Recent advances in metapopulation models have made it possible to relax this assumption and allow researchers to draw inferences about the effects of landscape structure on colonization dynamics using empirical data (Howell et al 2018).…”

Quantifying Nutrient Trade in the Arbuscular Mycorrhizal Symbiosis Under Extreme Weather Events Using Quantum-Dot Tagged Phosphorus

“…As the climate continues to warm, global ecosystems are experiencing an increase in the frequency and intensity of extreme weather events, such as sudden heat waves, droughts, torrential rains, and floods (IPCC, 2014;Allen et al, 2018). Extreme weather events can have dramatic impacts on the survival, abundance and distribution of species, and can even lead to the local extinction of species (Tinsley et al, 2015;Ray et al, 2016;Zylstra et al, 2019). While progress is being made in our ability to predict the effects of extreme weather events on single species, it is less understood how these events affect the interactions among species, such as in mutualism and parasitism (Harrison, 2000;Edwards and Richardson, 2004;Bronstein, 2015;Millar and Bennett, 2016;Gardner et al, 2017).…”