College of Science and Health Theses and Dissertations

Date of Award

Summer 8-22-2021

Degree Type


Degree Name

Master of Science (MS)


Biological Science


Within Middle America, cichlids and poeciliids account for more than half of the fish biodiversity. This richness in fish fauna highlights the complexity of Middle American biogeography: no other continental area on earth contains within its range the unparalleled abundance of secondary freshwater fish species (fish that can tolerate both saltwater and freshwater). Research into the biogeography of widely distributed Middle American freshwater fish is essential to understanding this unique region.

Three species of freshwater fishes (Belonesox belizanus – Pike killifish, Vieja maculicauda – Black belt cichlid, and Gambusia nicaraguensis – Nicaraguan mosquitofish) are widely distributed across rivers on the Caribbean slope of Central America (Matamoros et al., 2014). Belonesox belizanus and G. nicaraguensis are poecilids (live-bearing fish), while V. maculicauda is a cichlid (a diverse family of fishes primarily found in Africa, South America, and Central America). The overlapping distributions of these species allow for a comparative population genomics approach to understand their biogeographic history and evolution. Past research used individual loci to assess general phylogeographic patterns with little structure detected within each species; however, these data lacked power to properly test hypotheses of population subdivision, gene flow, and recent expansion. Greater genomic coverage and an increase in sample sizes (geographic coverage and number of individuals) are essential for the objective of this proposed research: to test hypotheses of biogeographic and evolutionary patterns of these three species across their Middle American distribution.

Our results using the mitochondrial COI gene suggest four clades of G. nicaraguensis, while more comprehensive sampling using genomic data supports only three populations. Two populations were recovered for both B. belizanus and V. maculicauda using genomic data. Divergence among populations was associated with geographic breaks for the two poeciliids although the location of the geographic breaks differed between species. The two populations detected for V. maculicauda were highly divergent genetically but sympatric. This study gives insight into the historical biogeography of the region, showing that population structure is complex and varies across widespread species.

SLP Collection


Included in

Biology Commons