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Dr. Irby Lovette

Director, Evolutionary Biology Program
Assistant Professor, Department of Ecology & Evolutionary Biology

Curator of Genetic Resources, Cornell University Museum of Vertebrates

Biographical sketch | Information for prospective students and others interested in working in my lab | Publications | Contact me

My personal research program centers on two broad topics: the generation and use of phylogenetic information, and the study of individual dispersal and population-level gene flow.

 

Parulidae phylogenetics. I have a long-term research program to reconstruct the evolutionary relationships of parulid warblers and related groups of birds, and to use the resulting information to explore their patterns of variation. These phylogenies are based on both long mitochondrial DNA sequences and sequences from a growing number of nuclear loci. My sample of taxa includes nearly all species and many geographic populations. From a combined taxon--and nucleotide--sampling perspective, this is one of the most robust and complete such data sets for any diverse avian clade.

My primary motivation in generating these phylogenetic trees is to use them to explore questions about diversification rates and the evolution of morphological, behavioral, and ecological diversity.

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Emberizine phylogenetics. At a somewhat deeper phylogenetic level, recent funding from the NSF Tree-of-Life program has fostered a collaborative network that links my parulid research with the projects of four other researchers working on similar questions in other closely related avian clades. By employing the same molecular markers and by combining our taxon sampling resources, we will be able to generate a robust phylogenetic tree for the entire Emberizinae, the clade of birds that includes familiar groups such as the warblers, sparrows, cardinals, tanagers, and blackbirds. This single subfamily of birds comprises nearly 10% of extant avian species diversity and nearly 15% of all Passeriformes.

This group is the focus of an impressive volume of behavioral, ecological, and evolutionary research, including studies of song learning, social and genetic mating systems, brood parasitism, long-distance migration, avian demography, and plumage evolution (sexual dichromatism and delayed plumage maturation). The group has also been a major focus of research on New World historical biogeography and the processes fundamental to species diversification in the region. The interpretation of the profound ecological, behavioral, and morphological variation in this group, in the context of New World landscapes and history, depends critically upon understanding phylogenetic structure.

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Florida Scrub-Jay gene flow and conservation genetics. The core of this NSF-funded project is an exploration of the relationship between field measurements of demography and dispersal behavior and molecular genetic estimates of gene flow. The project takes advantage of the wealth of knowledge about the Florida Scrub-Jay system generated by generations of field biologists, including (1) a complete inventory of all FSJ populations, (2) detailed demographic data on survivorship and reproduction, and (3) a large sample of documented dispersal distances as accurate as any available for a vertebrate. My role in this multi-collaborator project is to develop and screen an equivalently powerful suite of genetic markers, and to apply these data to a range of questions about the genetic structuring of Florida Scrub-Jay populations.

 

To assess levels and patterns of genetic structure within populations and across a gradient of habitat scales, we have developed 37 species-specific microsatellite markers. At present, we have a major laboratory initiative underway to develop a complementary battery of SNP markers. Ultimately we will screen >3,000 individuals using these two techniques. The resulting high-resolution portrait of genetic structure will allow us to explore hypotheses and predictions about gene flow generated from the field dispersal indices. The most general analytical goal is to test whether the quantitative gene flow models developed from field measurements of dispersal yield similar estimates to those derived from molecular genetic assays of population structure.

In a hypothesis-testing framework, we will also compare expected and observed rates of gene flow across habitat gaps of varying size and landscape type, with emphasis on identifying the gap sizes at which gene flow is functionally disrupted. At the statewide level we will test the prediction that the species is segregated into major, genetically distinct units reflecting ancient geologic events, with little or no modern gene flow between or among them. Because the Florida Scrub-Jay system is so well characterized and our genetic markers so powerful, these analyses will provide an important contribution to the controversial topic of why field and genetic approaches usually provide noncongruent estimates of dispersal parameters in wild organisms.

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Dispersal constraints in Neotropical birds. A second project on dispersal and gene flow centers on testing the relationship between dispersal ability and gene flow in a suite of tropical birds that likely differ in their dispersal biology. The project is a collaboration with Doug Robinson, Randy Moore, and Tara Robinson of Oregon State University. That group has extensive indirect evidence of how dispersal rates differ in bird species in central Panama. We are currently implementing a set of novel experiments that allow us to index dispersal ability directly in these species. To explore long-term effects of differential dispersal ability, we are using molecular markers to survey patterns of gene flow and population structuring in these species across a much broader geographic range. The resulting insights into the mechanisms of past and potential gene flow give us the basis for testing the links among dispersal behavior and long-term processes of population subdivision and speciation. In a conservation context, these results are also highly relevant to understanding the effects of forest fragmentation on population persistence, extinction risk, and disruption of gene flow.

 

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Biographical sketch | Information for prospective students and others interested in working in my lab | Publications | Contact me

 

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