Reference no: EM133814862

Question

On the Bahamian island of Andros, mosquitofish (Gambusia hubbsi) populations live in small isolated freshwater ponds between which there is little gene flow. The inland ponds were formed by rising sea levels and have been colonised by mosquitofish during the past 15 000 years. In some ponds there are few predators [low predation (LP) regime], and the mosquitofish in these have a body shape that optimises swimming for a long time, a character favoured by selection for finding food and mates (Figure 1, left). Other inland ponds have a high density of predators [high predation (HP) regime], and fish in these ponds have a body shape that optimises swimming in short, fast bursts, a character favoured by selection for escaping predators (Figure 1, right). There are two possible explanations for the differences in body shape of fish inhabiting different pools with different predator regimes: Fish of a similar body type found in different ponds (either HP or LP) share a common ancestor with similarly-shaped fish in other HP or LP ponds, and their body shape evolved before the populations were isolated in different ponds. The body shapes of the various populations were then conserved in descendants of that ancestor. LP body shape and HP body shape evolved repeatedly in different populations after they were isolated in different ponds, as a direct result of differences in predator regime.