Introduction sources and population genetics of Cichlasoma urophthalmus (Mayan cichlids) in South Florida

Background/Question/Methods

Invasive species are a major threat to biodiversity and ecosystem function, and are of increasing economic concern. Yet, ecologists have struggled to explain why some species succeed while others do not. One hypothesis is that a population with high genetic diversity should be able to adapt quickly to new environments, thus enhancing invasion success. However, other studies have revealed successful invasions resulting from a single introduction. This research aims to determine how introduction method influences population genetics using a successful aquatic invader. The Mayan cichlid (Cichlasoma urophthalmus) is native to the Atlantic slope of Central America. It was first recorded in Everglades National Park in 1983 and is now well established throughout most of south Florida. We examined genetic structure of introduced and native populations of Mayan cichlids by examining the cytochrome b gene and microsatellites to evaluate the source, number of introductions, and population genetic structure. 

Results/Conclusions

We have collected 645 fish from sites in south Florida, Mexico, Belize, Honduras, Nicaragua and Guatemala. Preliminary results indicated six cytochrome b haplotypes that can distinguish between samples from Mexico, Belize, and Honduras (native range), and south Florida (introduced range). Two of those haplotypes were found in multiple fish and separated all of the cytochrome b data into two distinct clades. One clade contained samples from Belize, Honduras, Nicaragua, and most of the samples from Mexico while the second clade contained all of the samples from Florida, all samples from three Guatemalan sites, and some of the samples from five Mexican sites. All of the samples from Florida were identical for cytochrome b except for one individual. These results indicate that Mayan cichlids underwent a limited introduction from one or more of the sites in either Guatemala and/or Mexico into south Florida. We have also identified and analyzed 18 microsatellite loci for 24 Mayan cichlids from Mexico, Honduras and Florida. The number of alleles per locus ranged from 3 to 21 and observed heterozygosity ranged from 0.208 to 0.875. These new loci will be used to verify the introduction sources indicated by cytochrome b and to compare population genetic structure within and among sites in the native and introduced ranges of Mayan cichlids.