|
| |
|
|
| |
Molecular Ecology |
|
| |
|
|
| |
Molecular markers comprise an exciting and important component of my research "toolbox" and I use these tools to explore research questions from angles that would not be possible otherwise. I am working to identify immature stages (and their host associations) of Ghana's forest-endemic butterflies. For many taxa this task is not straightforward and DNA samples are being collected for larvae that cannot be reared through to adulthood to allow for sequencing of a COI mtDNA barcode. In the context of sequences obtained from known adults, this barcode will permit identification of these immatures. Although not a panacea, genetic barcodes are being used successfully to expedite biodiversity discovery and documentation and to identify cryptic species (Hebert et al. (2004) PNAS 101:14812). A repository of molecular data is also being created from the network of forest reserves and sacred groves that I am surveying in anticipation of assessing within and between population variation in future phylogeographic studies. A key question is whether genetic diversity, as well as species diversity, is lost from habitat island communities. The system I have identified presents an ideal opportunity to explore this issue. |
|
| |
|
|
| |
An additional goal is to assemble a collection of microsatellite markers for use in evaluating spatial genetic structure in Papilio glaucus, the tiger swallowtail butterfly. This is a broadly distributed species that nonetheless exists as fragmented populations throughout large areas of its range, and that was purportedly restricted to Florida during the last ice age. Microsatellites, because of their rapid rate of mutation, have high potential to detect and track impact of fragmentation and population isolation on extant gene pools. They additionally potentially have power to reveal gene genealogies and thus to identify lineage branching and phylogenetic relationships among populations. P. glaucus samples have been collected from populations that collectively span the geographic region encompassed by Ohio, New Jersey, Florida, and Louisiana. Theoretically, it should be possible to identify and reconstruct the historical development of this species’ geographic range expansion from its putative glacial refugia, and to separate this historical footprint from pattern due to contemporary processes, e.g., using nested clade analysis. |
|
| |
|
|
| |
Development of microsatellite markers, however, appears to be a risky endeavor for those working with lepidopteran species (e.g., Williams et al. (2002) Molecular Ecology Notes 2:87). I have been able to identify only four polymorphic loci in P. glaucus from screenings of >10,000 recombinant clones. Interestingly, the microsatellite at a fifth, putatively X-linked locus was ultimately found to be cleanly and completely excised from the amplified region in 79 of the 80 adults assayed from five widely separated geographic populations! The complete excision of the repetitive region and nearly complete absence of this microsatellite from this broad geographic range survey was a major surprise and hints at a potential explanation for the general paucity of tandem repetitive regions in lepidoptera. Perhaps lepidopteran species come better equipped with an efficient DNA repair mechanism that deletes these energy-consuming, but presumably useless, non-coding regions of DNA from the butterfly genome? |
|
| |
|
|
|