B.10C Living Together Does Not Always Work – 9.1 – 04
Students were surprised to learn of a rare example of sympatric speciation in orcas in the Pacific Northwest. The “resident”, “transient” and “offshore” orcas hunt for different prey. The “resident” orcas feed exclusively on salmon and are found in nearby coastal waters. The “transient” orcas feed only on marine mammals and move north to south along the coast. The other group known as the “offshore orcas” are found well beyond the coast and sharks are an important part of their diet. The social structure of each population is different as well as their form of communication. They do not interbreed although they inhabit the same areas.
Did you know that there are many species of fireflies and each have their unique flashing lights? What is so special about that is the fact that different species of fireflies have very distinct patterns of flashing lights. Members of the same species find mates using their unique flashing patterns. This prevents breeding between different species, since the female will not mate unless she recognizes the light pattern.
Have you seen a blue-footed booby dance? Well, the blue-footed booby shares its habitat with other species in the same genus, but it never mates with the other species. Its behavioral isolation is promoted by its elaborate courtship ritual. The female blue-footed booby selects a mate after watching the entire ritual dance.
Sympatric speciation is common in plants due to polyploidy. Polyploidy results due to errors in meiosis that create extra chromosomes. New plants can grow in the same environment as the parent but are reproductively isolated due to the difference in number of chromosomes.
In the remote Lord Howe Island near Australia, there are two distinct but closely related palm trees. They are found in two areas of the island. The soil pH is different in these two areas. Palms send pollen through the air, so these two varieties could interbreed, but since speciation has already occurred, they do not produce viable hybrids. In this case, sympatric speciation could have occurred due to competition for soil to grow on.
Temporal isolation happens when two or more species reproduce at different times. There are three species of orchid that live in the same rain forest. Each species has flowers that last only one day. The flowers must be pollinated on the same day to produce seeds. But each species flowers on different days and therefore cross pollination does not occur.
Some flowers evolve to attract specific pollinators. The structure for access to the nectar varies. An example would be the two different species of monkey flowers. The pink flowers are more open in structure. They are pollinated by bees. The red flowers are narrower and are pollinated by hummingbirds. The hummingbirds can reach nectar deep within the narrow tubes while the bees prefer the wider floral tube to access the nectar. This prevents cross pollination between the two different species of monkey flower, even though they occupy the same general area.
Temporal isolation also occurs when two related frog species show reproductive isolation since one species breeds earlier in the year than the other.