Parasite resistance and genetic variation in the endangered Gila topminnow

In recent years, it has become apparent that introduced or novel pathogens or parasites may have a significant negative impact on endangered species. Here we examine experimentally the effect of an exotic fluke from guppies o n the endangered Gila topminnow. Populations from different sources showed variable responses (although statistically non-significant) to the fluke an d, in particular, the most homozygous population had high fluke infections and high subsequent mortality. Homozygotes for a MHC (major histocompatibil ity complex) gene had lower (although statistically non-significant) surviv al when infected with flukes than did heterozygotes. An inbred line from on e of the populations had statistically significant lower survival and highe r fluke infection than did a simultaneous outbred control. Overall, Gila to pminnows appear quite susceptible to infection by the non-native fluke comp ared to other related species. In addition, it was shown that Gila topminno ws can be infected by casual contact with infected guppies. This is another example of the potential detrimental effects of a parasite on an endangere d species, a threat that may constitute a particular problem for species wi th low genetic variation, either in general, for important MHC genes, or fo r populations with a past history of inbreeding.