Maintenance of Recombination

Why do almost all metazoans have some form of genome reshuffling every generation? Why is asexuality comparatively rare? These are questions we tackle using a comparative approach. One of the few asexual, all-female, and clonal animals is a livebearing fish, the Amazon molly (Poecilia formosa). It features a number of traits that make it a uniquely fascinating system.

(1): No meiosis. Yes, they are ameiotic, and have no recombination.

(2): Hybrid origin: Amazon mollies are a natural hybrid of two sexual species, the sailfin molly (Poecilia latipinna) and the Atlantic molly (Poecilia mexicana).

(3): Sperm dependency: Amazon mollies require sperm to trigger embryogenesis. Since they have no males in their own species, they have to obtain matings with males of syntopic sexual species, like the sailfin and the Atlantic molly. The sperm DNA is typically not incorporated.

We study many aspects of this system, often in cooperation with other research groups. Why do males of the sexual species mate with Amazon mollies? How can a system like this be stable in space and time? How does the absence of recombination shape the genome?

This phenomenon is the focus of a big NSF funded project, where we cross the parental species to retrace the steps of the original hybridization. This project is now running. Expect to see results sometime next week. The postdoc in charge of the project is Waldir Miron (more info on him is in the People tab).

Biogeography of Caribbean Freshwater Fishes

We are broadly interested in the fish faunas of the larger islands in the Caribbean (Hispaniola, Cuba, Jamaica), trying to understand what drives patterns of biodiversity on these islands as a model for large – scale biogeography. In addition to basic research we are very interested in providing data for fact based conservation decisions. The first publications on this topic are now out. Check out especially the descriptions of two new species of Limia (Limia islai and Limia mandibularis) from Haiti.

Sulfidic habitat in the Dominican Republic

Ecological Speciation

We are interested in understanding the factors that facilitate or inhibit ecological speciation. As model system we use Livebearing fishes that have colonized extreme habitats. One example is the Cave molly, a cave living form of the Atlantic molly (Poecilia mexicana). This species has colonized a cave in Tabasco, Mexico, which – in addition to being lightless – shows high concentrations of toxic hydrogensulfide in the water (17.442387, -92.775110). We study how toxicity and darkness interact to form the unique phenotype of the Cave molly by comparing it to other populations from a non-toxic cave, toxic surface waters, and non-toxic surface waters.