Hybridization is a form of speciation that involves mating organisms of two different species to create a hybrid that may have the potential of becoming a new species.

A famous, yet extremely unnatural example is the liger, which is a hybrid cross between a male lion and a female tiger. Ligers never occur in the wild and result in sterile males. Most animal hybrids are infertile and cannot produce offspring, whereas plant species hybridize more readily, resulting in fertile hybrids that may reproduce. So what do big fur balls have to do with dolphins?

In the wild, hybridization may result in the exchange of genetic material between divergent lineages, eventually producing the formation of new taxa. Recent evidence indicates that hybridization may lead to increases in biodiversity, which is key to adaptation through the formation of new species. A fairly recent study suggests that the evolution of a specific type of dolphin is the result of the admixture between two other closely related dolphin species. In their report, “Hybrid Speciation in a Marine Mammal,” authors Amaral, Lovewell, Coelho, Amato, and Rosenbaum declare the study of speciation through hybridization to be an exceptional opportunity to understand the mechanisms leading to speciation in the context of gene flow (transfer of genes from one population to another).

Tissue samples of the hybrid dolphin species Stenella clymene were taken from the Gulf of Mexico and Florida for sequencing. DNA extractions from the two suspected parent species were obtained from different locations in the Atlantic, Pacific, and Indian oceans in order to provide an overall estimate of genetic diversity for each species. DNA samples, photographic data, and skull measurements of Stenella clymene and its closely related relatives were compared in order to establish the presence of hybridization. The data prove that Stenella clymene is the hybrid of two other closely related species, S. coeuruleolba and S. longisrostris. Eeeek!

Although they are aquatic and resemble cuter versions of sharks, dolphins are mammals, meaning that this finding has important implications for better understanding hybrid speciation in mammal species.

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By Alissa Patterson

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