Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)

First Advisor

Robert M. Zink


I present allozyme and mitochondrial DNA (mtDNA) data on the genetic structure of five species of Amazonian forest birds at two geographic scales. The five species, Glyphorynchus spirurus (family Dendrocolaptidae), Leptopogon amaurocephalus (Tyrannidae), Hypocnemis cantator, Myrmeciza hemimelaena, and Hylophylax poecilinota (all three Formicariidae), are common forest understory inhabitants throughout much of Amazonia. At the local geographic scale, I hypothesized that forest fragmentation affected genetic structure in these species. Study sites were in the Department of Santa Cruz, Bolivia. Six sites separated by 150 km or less for each species were sampled: three sites in continuous Amazonian forest, and three in forest fragments separated from continuous forest by South American savanna. If forest fragmentation leads to genetic isolation, small populations in the forest fragments should exhibit decreased genetic variation as a result of inbreeding depression. Isolated populations may also exhibit genetic differentiation from one another and from populations in continuous forest. Allozymic data were not consistent with predicted effects of forest fragmentation, and neither allozyme nor mtDNA data suggested that genetic variation had been lost in forest fragment populations. MtDNA data for three formicariid species suggested that forest fragment populations had differentiated from populations in contiguous forest. The most common haplotypes in several forest fragment populations these three species were not found at continuous forest sites, whereas the most common haplotypes in contiguous forest sites occurred in both contiguous forest and forest fragments. Two non-formicariids had either fewer (G. spirurus) or greater (L. amaurocephalus) overall numbers of haplotypes than the three formicariids, but neither exhibited effects consistent the hypothesis that forest fragmentation affected genetic structure. At a regional geographic scale, I hypothesized that these sedentary Amazonian species would exhibit greater genetic differentiation than comparable populations of more mobile temperate species. I compared samples from two biogeographic regions of the Amazon basin, the Inambari and the Rondonian; samples at this scale were separated by up to 1750 km. For both allozymes and mtDNA, all species except L. amaurocephalus exhibited levels of differentiation consistent with greater geographic isolation than often found among congeneric species of temperate birds.