"Little Sharks, Big World: Genetic Insights into Horn Shark Dispersal & Migration" скачать в хорошем качестве

"Little Sharks, Big World: Genetic Insights into Horn Shark Dispersal & Migration"

Presented by Sean Canfield (ToBo Lab, Hawaiʻi Institute of Marine Biology). *One hiccup: Speaker is muffled through short video clip of Sean catching a Horn Shark The field of genetics provides a useful way to assess connectivity – that is, the degree of movement and settlement of individuals – between populations. It has been especially useful in the marine environment, where the direct tracking of individuals can be very difficult. To date, little attention has been paid to marine organisms with small range sizes and a limited ability to travel large distances. This is a problem, because these species tend to have higher risks of extinction in the marine environment than their well-traveled brethren. Enter the California horn shark (Heterodontus francisci): a small, bottom-dwelling shark inhabiting the East-Pacific coastline from California to Mexico. This common species is known to maintain small home-ranges as adults and can stay at these sites for years at a time, making it an excellent candidate for study. To examine population connectivity in this species, I sequenced DNA from sharks in the waters of mainland California, the Channel Islands (CA), and the Baja peninsula (Mexico). Using these DNA sequences, I have found evidence of discrete island populations of horn sharks, which exchange very few migrants with the California mainland only ten to twenty miles away. This may require us to re- think the spatial scale of isolation in the marine environment.