Influence of male size and competition on male mating preference in the Sailfin molly

Felicia Schwake

Amazon mollies are gynogens and reproduce asexually but require sperm, commonly from male Sailfins, to trigger embryogenesis. Sailfin mollies are a sexual species that commonly live in the same habitat as Amazon mollies. Theoretically, Amazon mollies should cause Sailfin mollies to go extinct because of their ability to increase in numbers more quickly. In turn, Amazon mollies would go extinct because of their need for a sperm donor. I’m interested in how these two species are able to live in stable coexistence. One possible mechanism is male choice. In theory, males should not mate with Amazon mollies because they gain no fitness-relevant offspring. Also, Amazon mollies must compete with female Sailfin mollies. Currently, my project is trying to determine if larger male Sailfin mollies force smaller male Sailfin mollies into proximity and mating situations with Amazon mollies.

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