line decor
  
line decor
   
   

David K. Skelly
Yale University
School of Forestry & Environmental Studies
370 Prospect Street
New Haven, CT 06511 USA

Yale FES

 

 


Ecology of Amphibian Metacommunities
OVERVIEW

The textbook description of amphibian community structure has been based on keystone predation.  This concept relies on some sort of gradient over which the intensity of predation varies, encouraging reduction or elimination of dominant competitors in some locations and allowing dominant competitors to exclude inferior competitors in others. 

Our long-term research in Michigan (since 1988) and Connecticut (since 1996), largely conflicts with this view [abstract].  Instead of assemblages of strong interactors, it appears that larval amphibians in natural populations typically do not compete intensely and there is little evidence that predators result in exclusion from nonpermanent wetlands.  In the language of metacommunity theory, it appears much more like these amphibians may exist in layers of single species metapopulations.

Nevertheless, amphibian distributions are strongly patterned.  Where do these patterns come from?  The permanence of a wetland and its light and thermal environment appear to be key variables.  Repeated cohort loss from drying can lead to local extinction of a species.  The time constraint imposed by drying can be enhanced when vegetation grows up around wetlands.  Shading leads to lower temperatures and slower developmental rates.  Vegetation also evapotranspires.  In spite of any contrary intuitions, a given wetland heavily shaded by forest vegetation will dry faster than the same which have little vegetation near the basin.  The synergistic action of these factors can cause populations to go extinct.  Similarly, it appears that disturbances that remove vegetation and alter hydrology can promote population establishment.  The likelihood of establishment can be related to the proximity of source populations and the structure of the intervening terrestrial environment.

This research is important because, as with rocky intertidal systems, further research has shown that "post-settlement" mechanisms initially used to describe community structure now need to be revised and expanded.  For amphibians, linkages among breeding ponds and the dynamics of the terrestrial ecosystems that surround breeding ponds have demonstrable impacts on amphibians that may often trump the impacts of species interactions initially used as a basis for understanding amphibian communities.

Vernal pond in Vermont

 

Spotted salamander (Ambystoma maculatum)

REPRESENTATIVE PUBLICATIONS

Halverson, M. A., D. K. Skelly, J. M. Kiesecker, and L. K. Freidenburg. 2003. Forest mediated light regime linked to amphibian distribution and performance. Oecologia 134:360-364.  Link

Semlitsch, R. D. and D. K. Skelly. 2007. Ecology and conservation of pool-breeding amphibians. Pages 127 to 147 in A. Calhoun and P. deMaynadier (Eds.) Science and Conservation of Vernal Pools in Northeastern North America. CRC Press. ISBN 0849336759.

Skelly, D. K. 1997. Tadpole communities. American Scientist 85:36-45.  Link

Skelly, D. K., E. E. Werner, and S. A. Cortwright. 1999. Long-term distributional dynamics of a Michigan amphibian assemblage. Ecology 80:2326-2337.  Link

Skelly, D. K. and J. M. Kiesecker. 2001. Venue and outcome in ecological experiments: manipulations of larval anurans. Oikos 94:198-208.  Link

Skelly, D. K., L. K. Freidenburg, and J. M. Kiesecker. 2002. Forest canopy and the performance of larval amphibians. Ecology 83:983-992.  Link

Skelly, D. K. 2002. Experimental venue and estimation of interaction strength. Ecology 83:2097-2101.  Link

Skelly, D. K., M. A. Halverson, L. K. Freidenburg, and M. C. Urban. 2005. Canopy closure and amphibian diversity in forested wetlands. Wetlands Ecology and Management 13:261-268.  Link

Skelly, D. K. 2005. Experimental venue and estimation of interaction strength: reply. Ecology 86:1068-1071.  Link

Urban, M. C. and D. K. Skelly. 2006. Evolving metacommunities: Toward an evolutionary perspective on metacommunities (Concepts & Synthesis). Ecology 87:1616-1626.  Link

Wellborn, G. A., D. K. Skelly, and E. E. Werner. 1996. Mechanisms creating community structure across a freshwater habitat gradient. Annual Review of Ecology and Systematics 27:337-363.  Link