Newly discovered site in the Bahamas houses a hybrid between two groups of mangrove rivulus fish.
Self-fertilization is extremely rare in vertebrates. The mangrove rivulus is the only known vertebrate that routinely reproduces by selfing (teenagers taking selfies do not count). Given this peculiar mode of reproduction, hybridization should be rare. Or so you would think…
The mangrove rivulus currently comprises two species (Kryptolebias marmoratus and K. hermaphroditus), but can be divided into three main groups:
- Northern group in Florida and the Caribbean that corresponds to K. marmoratus
- Southern group in Brazil that corresponds to K. hermaphroditus
- Central group in the Caribbean that probably corresponds to a third species
A laboratory experiment already showed that hybridization between fish from the central group and K. hermaphroditus is possible. But does it also occur in nature? A recent study in the journal Biology Letters answers this question: yes!
Andrey Tatarenkov and his colleagues discovered a site in San Salvador (the Bahamas) where members from the central group and K. marmoratus coexist. This finding is already quite special because the three groups of rivulus were not known to co-occur. Genetic characterization of this population revealed a hybrid individual: a cross between a male K. marmoratus and a hermaphrodite of the Central group. Further analyses suggested that this hybrid has been selfing for two generations.
How common hybridization is in this population and if there is gene flow between the different species/groups remains to be investigated.
Tatarenkov, A., Earley, R.L., Taylor, D.S., Davis, W.P. & Avise, J.C. (2018) Natural hybridization between divergent lineages in a selfing hermaphroditic fish. Biology Letters, 14:20180118.