B.10C Living Together Does Not Always Work – 03

Two species of Midas cichlid fish are found in Lake Apoyo. The two species have slight differences in body shape and jaw structure. They cannot interbreed. Research shows that the two species live at different depths inside the lake. One lives in open top water while the other lives in deeper water. Competition for food could have led some to look for food in the deeper waters. As they continued to live and feed in different parts of the lake, sympatric speciation might occur. Over time, this would lead to a different species that cannot breed with each other.

Cichlids in the African Great Lakes also shows sympatric speciation. Females choose males that has same coloration as her. This helps maintain the sympatric speciation in the lakes. A male cichlid will quiver, or shake, to attract females. This produces a certain number of pulses and pulse periods. The female chooses mates by selecting numbers and rates of pulses found within her species. This increases the chances of survival of her offspring.

Recent sympatric speciation may be occurring in the apple maggot fly. The flies lay eggs on fruits of hawthorn trees. But after the introduction of apples in the 19th century, some lay their eggs on apples. The flies usually look for mates and lay eggs on the same fruit that they grew up on. So, over time although they are in the same geographic area, speciation may occur between the two groups, based on their preference of the fruits that they lay their eggs on.

Professor Pickens also showed pictures of the Eastern Meadowlark and the Western Meadowlark. The two birds look very similar to each other. But they are two distinct species. They have different mating calls. They do not respond to each other’s mating calls. Since the two do not mate they are considered to be two different species.