Genetic study confirms hybridization between two dolphin species.
Bird hybrids – the main focus of this website – are relatively easy to identify. Unusual plumage patterns and mixed songs can provide some clues. But what about less visible animals, such as dolphins and whales? Genomic analyses already revealed hybridization between several whale species (read my blog post about it here). A recent study in Molecular Phylogenetics and Evolution shows that hybridization also readily occurs in dolphins.
When you take a boat ride on the Greek Seas and explore the Gulf of Corinth – which separates the Peloponnese from mainland Greece – you might see some groups of dolphins composed of several species. Indeed, in this part of the Meditarrean three species of dolphins peacefully swim side by side: the striped dolphin (Stenella coeruleoalba), the short-beaked common dolphin (Delphinus delphis), and Risso’s Dolphin (Grampus griseus). These mixed associations provide the ideal circumstances for hybridization. But does it actually occur?
To answer this question, Aglaia Antoniou and her colleagues focused on two species: the striped dolphin and the short-beaked common dolphin. Individuals with intermediate pigmentation patterns have been reported, suggesting these species might be interbreeding. The researchers collected samples from 45 striped dolphins, 12 short-beaked common dolphin and 3 intermediates. Based on microsatellites and mitochondrial DNA (mtDNA), they went on their quest to find hybrids.
Hybridization into the Future
The software package NEWHYBRIDS confirmed their suspicions: the intermediate morphs, along with 12 other individuals, were classified as hybrids. Moreover, two samples that were identified as short-beaked common dolphin contained mtDNA of the other species. Clearly, these dolphins are interbreeding.
In the future, hybridization might become more common. The population of short-beaked common dolphins is declining and these animals tend to associate with striped dolphins because of their tendency to stay in large groups. This behavior can affect the incidence of hybridization and pose a threat for the already endangered short-beaked common dolphin.
Antoniou, A., Frantzis, A., Alexiadou, P., Paschou, N. & Poulakakis, N. (2018) Evidence of introgressive hybridization between Stenella coeruleoalba and Delphinus delphis in the Greek Seas. Molecular Phylogenetics and Evolution, 129:325-337.