Saturday, December 22, 2007

In the Lab 1: Island Speciation

My Honor's Thesis is a phylogeography study - the genetic form of biogeography, examining the relationship of phylogenetic lineages and gene flow with geographic distribution. Phylogeography can give us useful insights into speciation and factors influencing biodiversity. My particular study is part of a larger project by Andrea Townsend looking at island speciation on Hispaniola (Haiti and the Dominican Republic). Hispaniola is the second-largest island in the Caribbean, with the highest mountains. Several mountain ranges cleave the island east-to-west, separated by deep alluvial valleys that flood during geological periods of high sea level.

Hispaniola is very interesting to birders, as it contains over 30 endemic species and many endemic subspecies. Particularly interesting from an evolutionary perspective is the presence of several sister-species pairs: a pair of species that appear to have diverged from a common ancestor on Hispaniola. Most island speciation is allopatric in nature: species form when a population becomes isolated on the island, diverging and becoming one new species on the island. The presence of multiple sister-species pairs on Hispaniola may indicate that it is large enough to allow avian speciation to occur in situ, something previously only thought to occur on the largest islands (Madagascar, etc).

My study looks at one sister-species pair on the island to examine the effects of past and present topographic barriers on gene flow in the populations. My study species are the Black-crowned Palm-Tanager (Phaenicophilus palmarum) and the Gray-crowned Palm-Tanager (Phaenicophilus poliocephalus), two common habitat-generalist endemics.

Phaenicophilus poliocephalus
(Photo courtesy of Andrea Townsend)

For this study, a large amount of genetic data is needed. The following long-overdue series of posts is a brief step-through of the collection and analysis of genetic data for this type of evolutionary study.

Part 2: From Bird to DNA

1 comment:

  1. The photo shows P. palmarum. Doesn't show crown well but too much white on throat and spot above eye too large for it to be P. poliocephalus.