Speciation, the evolution of new, distinct species from a single ancestral population, is the fundamental process generating the earth?s biodiversity. This project focuses on a group of twelve finch species called ?munias? that represent one of the most extraordinary examples of rapid speciation in birds. The twelve species, most living in New Guinea or surrounding islands, are nearly identical genetically, but have evolved an astounding diversity of plumage colors and patterns, as well as differences in bill size. This project combines the first significant field research on these birds (the grant specifically supports fieldwork in the Trans Fly region of Papua New Guinea, where two additional species will be sampled) with modern genome sequencing technology to reconstruct the evolutionary history of these species and determine the number and identity of genes that are responsible for differences among species.
Given their morphological diversity and recent origin, the munias provide an exceptional opportunity to advance the new field of speciation genomics, which seeks to understand the patterns of genetic change responsible for the evolution of new species. The research will test the hypothesis that natural selection on a small number of genes is sufficient to generate new species, challenging a classic model of gradual genome-wide divergence. As such, the results may overturn commonly held assumptions about the nature of species and speciation. The research will also advance our understanding of the evolution of plumage coloration in birds generally and will provide critical data for making informed decisions on priorities for biodiversity conservation.
Speciation, the evolution of morphologically, behaviorally and/or ecologically distinct organisms from a common ancestor is the fundamental process generating biodiversity. This Doctoral Dissertation Improvement Grant supported a critical component of an ongoing investigation into a previously unrecognized, but extraordinary example of rapid speciation in birds. Twelve closely related species of "munias" in the genus Lonchura in northern Australia and Papua New Guinea have rapidly evolved a diversity of plumage colors and patterns. Some of these species have undoubtedly evolved as a result of divergence between populations in different geographic areas (a process classically known as allopatric speciation), but this group of munias is also remarkable in that most of these species live in the same area as one or two other species in the same genus. In the classic allopatric model, the ability of newly evolved species to coexist in the same place represents the culmination of the speciation process. Thus, examples of closely related forms coexisting in the same area have been of particular interest for ecological, genetic and phylogenetic analyses of speciation. The specific goal of this project was to extend the geographic and taxonomic sampling of munias by allowing travel to the Trans-Fly savannahs of Western Province, Papua New Guinea, where two additional species, the black munia Lonchura stygia and the grey-crowned munia Lonchura nevermanni, were sampled. During a highly successful expedition in September-October 2012, 50 individuals of L. nevermanni and 38 individuals of L. stygia were captured, measured, photographed, and sampled for genetic analysis. In addition, 20 birds of each species were collected and prepared as permanent museum specimens with associated tissue samples. Recordings of vocalizations and notes on habitat, diet, and behavior were also taken. These samples and specimens are currently stored at Boston University, but will be donated to a permanent museum collection (e.g., Harvard Museum of Vertebrate Zoology) at the conclusion of the larger project. The samples collected in the Tran Fly region are critical to ongoing research examining the evolutionary history of this group of birds and the genomic changes responsible for the differences between them. The recent evolution of these species and the likelihood that species living in the same areas continue to exchange genes provides an ideal opportunity to used modern genome sequencing technology to identify those portions of the genome responsible for speciation, a general question of substantial current interest in evolutionary biology. This project represents the first study of an extraordinary avian radiation and promises to lend new insights into the genomic consequences of speciation and the evolutionary mechanisms shaping the genetic structure of populations, central questions in evolutionary biology. The completed work represents a significant extension to an ongoing project, increasing its coverage of species in the focal group from 67% to 83%. The project has also facilitated an outstanding dissertation project for a female graduate student and provided research opportunities and training for young scientists in Papua New Guinea. Finally, the Lonchura radiation is the subject of a newly developed module for an ongoing educational outreach program that serves Boston area high school students.
