Use of multiple dispersal pathways facilitates amphibian persistence in stream networks

Abstract

Although populations of amphibians are declining worldwide, there is no evidence that salamanders occupying small streams are experiencing enigmatic declines, and populations of these species seem stable. Theory predicts that dispersal through multiple pathways can stabilize populations, preventing extinction in habitat networks. However, empirical data to support this prediction are absent for most species, especially those at risk of decline. Our mark-recapture study of stream salamanders reveals both a strong upstream bias in dispersal and a surprisingly high rate of overland dispersal to adjacent headwater streams. This evidence of route-dependent variation in dispersal rates suggests a spatial mechanism for population stability in headwater-stream salamanders. Our results link the movement behavior of stream salamanders to network topology, and they underscore the importance of identifying and protecting critical dispersal pathways when addressing region-wide population declines.amphibian decline | dendritic ecological network | stream salamander | plethodontidae | movement

Population Genetics of the Eastern Hellbender (Cryptobranchus alleganiensis alleganiensis) across Multiple Spatial Scales

“…For example, there is a clear scaling-up effect of genetic variance partitioning among sub-basins in species with some degree of terrestrial dispersal (Table 4). Indeed, the black-bellied salamander (Desmognathus quadramaculatus ) conforms well to predictions of higher variance within stream reaches (lower hierarchical levels) possibly due to high levels of overland dispersal [73]. On the other hand, patterns of variance partitioning for some species of fishes are not explained by high dispersal ability, but rather strong natal philopatry within particular rivers or higher historical connectivity [71].…”

Metapopulation persistence and species spread in river networks

“…Model (1) has been parameterised with demographic (Organ ) and dispersal (Campbell Grant et al . ) data relative to the salamander species Desmognathus fuscus and D. monticola (technical details in Appendix S6). The juveniles of these two amphibian species can move both along stream corridors and overland, whereas larvae and adults are almost sessile.…”

“…As an example, in a massive mark‐recapture study (Campbell Grant et al . ) of two lungless salamander species in stream networks of Virginia, the newly metamorphosed (juvenile) salamanders had the highest probabilities of dispersing to other stream reaches, thus being the primary responsible for overland connections. Although it is relatively common to find freshwater organisms that begin their life cycle as motile and reach maturity as sessile (e.g.…”

Conservation genetics of extremely isolated urban populations of the northern dusky salamander (Desmognathus fuscus) in New York City

“…Population losses have also been reported from large, contiguous protected areas in the northeastern USA (Bank et al, 2006), and population densities of southern dusky salamanders ( D. auriculatus ) are inversely correlated with the degree of urbanization (Orser & Shure, 1972). Population stability may be realized when salamanders disperse through multiple pathways in stream networks (Campbell Grant et al, 2010), but both streams (Walsh et al, 2005) and overland corridors (Munshi-South, 2012) are typically degraded in urban environments. Other small vertebrates with limited dispersal ability also exhibit population genetic patterns consistent with loss of population connectivity.…”