Allopatric Speciation on an Archipelago

Winds or ocean currents carry a few individuals of mainland species to remote, isolated islands chains (archipelagos) such as Hawaii

Habitats and selection pressures that differ within and between the islands foster divergences that result in allopatric speciation

Example: Hawaiian honeycreepers and thousands of other species of finches are unique to the Hawaiian archipelagoWinds or ocean currents carry a few individuals of mainland species to remote, isolated islands chains (archipelagos) such as Hawaii

Habitats and selection pressures that differ within and between the islands foster divergences that result in allopatric speciation

Example: Hawaiian honeycreepers and thousands of other species of finches are unique to the Hawaiian archipelago

,’ 11" _ Akepa Akekee Nihoa finch Fallla Maui parrotbill Apapane (Loxops coccineus) (Loxops caeruleirostri's) (Telespiza ultima) (Loxioi'des bail/em) (Pseudonesror xanthaplirys) (Himatione sanguinea) Insects, spiders, insects, spiders. Insects, buds, seeds, Mamane seeds, buds, insect larvae, pupae; Nectar, caterpillars and nectar; high mounr nectar; high mounr flowers, seabird eggs; flowers. berries, insects; mountain forests, dense other insects, spiders; tain rain forest tain rain forest rocky or shrubby slopes high mountain dry forests underbrush high mountain forests Poouli (Me/amprosops Maui Alauahio Kauai Amakihi (Hemi! Akiapolaau Akohekohe liWi phaeosoma) (Parareomyza montana) gnatnus kauaiensis) (Hemignathus munrol) (Palmeria dolei) (Vest/aria cacoinea) Tree snails, insects in Bark or leaf insects, Earkrpicker; insects, Probes, digs insects Mostly nectar from flowering Mostly nectar. some forest understory some nec1ar: high spiders, nectar; high from big trees; high trees, some insects. pollen; insects: high mounr mountain rain forest mountain rain forest mountain rain forest high mountain rain forest tain rain forest Kauai Nitihau ’ Oahu Archipelagos such as the Hawaiian islands (right) are separated from mainland continents by thousands of miles of open oceania geographic barrier that prevents gene flow between island colonizers and mainland populations. Further divergences occur as colonizers spread to the other islands in the chain. DNA sequence comparisons sug gest that the ancestor of all Hawaiian honeycreepers resembled the housefinch (Carpodacus) at left. N ‘ Molokai ~> Maui 0 500 kilometers H—H—LH—H 0 300 miles Hawai'i