Abstract
AbstractKey factors affecting metapopulation dynamics of animals include patch size, isolation, and patch quality. For wetland‐associated species, hydrology can affect patch availability, connectivity, and potentially habitat quality; and therefore drive metapopulation dynamics. Wetlands occurring on natural river floodplains typically have more dynamic hydrology than anthropogenic wetlands. Our overall objective was to assess the multiyear spatial and temporal variation in occupancy and turnover rates of a semi‐aquatic small mammal at two hydrologically distinct wetland complexes. We live‐trapped marsh rice rats (Oryzomys palustris) for 3 yr and >50 000 trap nights at nine wetland patches on the Mississippi River floodplain and 14 patches at a reclaimed surface mine in southern Illinois. We used dynamic occupancy modeling to estimate initial occupancy, detection, colonization, and extinction rates at each complex. Catch per unit effort (rice rats captured/1000 trap nights) was markedly higher at the floodplain site (28.1) than the mining site (8.1). We found no evidence that temperature, rainfall, or trapping effort affected detection probability. Probability of initial occupancy was similar between sites and positively related to patch size. Patch colonization probability at both sites was related negatively to total rainfall 3 weeks prior to trapping, and varied across years differently at each site. We found interacting effects of site and rainfall on extinction probability: extinction increased with total rainfall 3 months prior to trapping but markedly more at the floodplain site than at the mining site. These site‐specific patterns of colonization and extinction are consistent with the rice rat metapopulation in the floodplain exhibiting a habitat‐tracking dynamic (occupancy dynamics driven by fluctuating quality), whereas the mineland complex behaved more as a classic metapopulation (stochastic colonization & extinction). Our study supports previous work demonstrating metapopulation dynamics in wetland systems being driven by changes in patch quality (via hydrology) rather than solely area and isolation.
Highlights
A metapopulation is the term used to describe “a population of populations which go extinct locally and recolonize” (Levins 1970)
Extinction and colonization (Levins 1970). This framework has been expanded to include the influence of patch size, quality, and degree of isolation on colonization and extinction rates, but the actual colonization and extinction events are considered stochastic (Hanski 1998, Moilanen 1999)
Studies of key factors influencing metapopulation dynamics have focused on patch size and isolation
Summary
A metapopulation is the term used to describe “a population of populations which go extinct locally and recolonize” (Levins 1970). Vrieze 1979, Forys and Dueser 1993) and to move ~400 m daily (Cooney et al 2015b) increase their dispersal potential, which in turn increases gene flow among distinct populations (Loxterman et al 1998) Rice rats alter their movement in response to water fluctuations, including dispersal in search of water during dry seasons (Smith and Vrieze 1979) and the use of upland areas during floods (Kruchek 2004). We studied metapopulation dynamics of rice rats at two hydrologically distinct wetland complexes (mineland and floodplain) over 3 yr to meet two objectives: (1) determine important landscape covariates influencing rice rat occupancy of patches within each wetland system, and (2) quantitate spatial and temporal variation in extinction and colonization rates of rice rats among local populations at these wetland complexes. Colonization rates of rice rats might be higher in riverine floodplain wetlands during periods between flood events, when there is enough dry land to facilitate movement among multiple wetland patches
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