Evol Ecol Res 6: 457-471 (2004)     Full PDF if your library subscribes.

Hybrid response to pathogen infection in interspecific crosses between two amphibian species (Anura: Ranidae)

Matthew J. Parris*

Department of Biology, University of Memphis, Memphis, TN 38152, USA

e-mail: mparris@memphis.edu


Interspecific hybridization can affect fitness-related traits, such as response to pathogens. Few experimental studies have directly addressed the effects of pathogens on host fitness in hybrid zones, particularly in animal systems. I used a system of hybridizing leopard frogs to test for differences in response to disease as a function of genetic admixture. I raised F1 hybrid and parental genotypes between Rana blairi (plains leopard frog) and Rana sphenocephala (southern leopard frog) in replicated experimental tanks, and tested the effect of an emergent amphibian pathogen, chytrid fungi (Batrachochytrium dendrobatidis), on larval growth and development. Chytrid did not have a significant effect on larval survival for any genotype. Chytrids reduced body mass at metamorphosis and increased duration of the larval period for all genotypes. F1 hybrids experienced smaller metamorphic body masses and longer larval periods than both parental genotypes, but only in chytrid environments. Significantly, more F1 hybrids were infected than either parental species. These results indicate that interspecific hybridization may produce relatively fit hybrid genotypes in pathogen-free conditions, but hybrids suffer decreased performance in the presence of chytrids. Such results suggest that hybridization between divergent amphibian lineages may produce hybrid genotypes with a reduced ability to cope with emergent pathogens.

Keywords: amphibian, chytridiomycosis, disease, hybridization, larvae, pathogens, Rana.

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