Turnover in an amphibian metacommunity: the role of local and regional factors

Abstract

Ecologists have long realized that stable species richness values can mask rapid turnover in species composition. Because turnover occurs as a consequence of both local and regional processes, understanding the responsible factors provides insight on processes influencing community structure at different scales. Despite the insights to be gained from data on species turnover, they remain relatively uncommon. We present data on the interannual turnover in species composition of larval amphibian communities in 37 ponds over seven years. Species composition of a given pond community was highly dynamic; about half of the species that could be found breeding in a particular pond were actually present in a given year. All species participated in this community turnover, but to different degrees. Using a model selection approach, we show that a statistical model including local environmental factors (pond area, hydroperiod, and canopy cover) and pond connectivity on the landscape provided the best predictions of turnover. Averaged parameter estimates were significant for area, hydroperiod, and connectivity and these same variables were identified by hierarchical partitioning as having significant independent effects on turnover. Area and hydroperiod were negatively related to turnover, whereas connectivity was positively related to turnover. Additionally, the average fraction of years a species was present in a pond was positively correlated with average local population size, but even more strongly correlated with regional population size, suggesting both local and regional influences on turnover. Of the measured biotic factors (biomass of fish, invertebrate predators, anuran and caudate larvae), presence of fish was the only factor that significantly affected rates of turnover. Several mechanism could be responsible for changes in species composition (species extinctions, skipped breeding and movement of choruses), but extinctions appear to be the major cause of turnover. These results have important implications to understanding long-term persistence of species on landscapes and the causes of patterns in species richness on environmental gradients.Ecologists have a longstanding interest in the causes of patterns in species richness and composition of communities. Early observations suggested that, while species richness could be relatively stable in an environment, membership of the community could be dynamic. For example, theories of island biogeography and the effects of disturbance provided clear, early statements that a colonization/extinction dynamic may underlie relative stability in species richness across habitats that differ in characteristics such as area, isolation, or disturbance (MacArthur and Wilson 1967, Connell 1978). More recently, interest in the regional processes contributing to population persistence and the structure of ecological communities (Hanski 1999, Hubbell 2001 has further emphasized the importance of temporal turnover. This interest, however, also has highlighted the lack of long-term ...

Opposite effects of environmental variability and species richness on temporal turnover of species in a complex habitat mosaic

“…For instance, while Pandit et al (2009) studied differences in spatial variation between habitat specialists and generalists, they treated the different years as replicates. However, population dynamics and community structure also changes over time within a local community as a consequence of both local environmental processes (including biotic interactions) and spatial, or regional processes (Werner et al, 2007;Pandit et al, 2009). For example, extinction may occur when species density declines below threshold, but a species can be rescued from propagules of neighbouring habitats or dormant individuals or seed banks (Chesson & Warner, 1981;Hanski et al, 1996;Shurin, 2007;Shurin et al, 2010).…”

“…Thus, it may be necessary to study temporal turnover in the complex mosaic of habitats in a landscape to understand the patterns in a fragmented habitats. However, the main impediment to the study of temporal turnover is the lack of long-term data from a multiple sites or habitats (Werner et al, 2007).…”

Water, stream morphology and landscape: complex habitat determinants for the fire salamander Salamandra salamandra

“…An increasing number of studies evaluated the relationship between amphibian distribution and habitat across all the continents, to provide scientific information helping to set up conservation plans. These studies improved our knowledge of mechanisms influencing the patterns of species abundance and occurrence (Van Buskirk, 2005), increased our understanding of the ecological processes that underlie the effects of habitat change (Gardner, Barlow and Peres, 2007), and helped to individuate the factors determining variation in species distribution (Skelly, Werner and Cortwright, 1999;Dalbeck, Lüscher and Ohlhoff, 2007;Werner et al, 2007). Nevertheless, our knowledge of the effect of environmental modification on amphibians is far to be complete, and more studies are required on the relationships between amphibian distribution and habitat, before generalizations can be performed (Gardner, Barlow and Peres, 2007).…”

Rapid Turnover in Site Occupancy of a Pond-breeding Frog Demonstrates the Need for Landscape-level Management

“…Many local amphibian populations experience high turnover M'Closkey 1996, 1997;Skelly et al 1999;Trenham et al 2003;Werner et al 2007). We found high turnover in the population and that the size of the male Table 6 Model-averaged estimates (and SE) of the probability of waterbody usage (b y) and probability of turnover (b "), and betweenyear turnover rate (l), by the green and golden bell frog (Litoria aurea) at 30 waterbodies on Kooragang Island in 2000 and 2001.…”