Species Delineation and Population Genetics of Menidia Species in Southern Florida

The key silverside (Menidia conchorum) is one of three silverside species occurring in southern Florida. In contrast to the tidewater silverside (M. peninsulae) and the inland silverside (M. beryllina), it is reported to have a very restricted geographic distribution (the lower Florida Keys) and have very specialized habitat requirements (small hypersaline ponds). However, the taxonomic status of the key silverside is questionable, due to a lack of diagnostic morphological features separating it from the tidewater silverside.

Because of these morphologically similarities and indications that their distribution overlaps, it has recently been hypothesized that the key silverside is in fact an ecotype of the tidewater silverside. To address this issue, we resolved the phylogenetic relationships of Florida M. beryllina, M. peninsulae and M. conchorum using molecular markers (CytochromeoxidaseI, Internal transcribed spacer, NADH dehydrogenaseII, mitochondrial control region). We also further investigated the geographic range and distribution of the key and tidewater silverside in the Florida Keys.

DNA sequence data at multiple loci confirmed that   the tidewater and key silversides are not reciprocally monophyletic and share several haplotypes. Our data support the hypothesis that the key silverside is an ecotype of the more widespread tidewater silverside (M. peninsulae,).