Description
Plant-insect relationships are among the most common interspecific relationships observed in biology. As these two organisms closely interact with one another, profound effects on adaptation and interaction can be observed. The genus Astragalus (milkvetches) is the most rapidly speciating plant lineage known, with an astounding array of fruit morphology and defensive chemistry. We lack an empirical understanding as to why speciation rates are so high in this genus, but one possibility is that rapid diversification is driven by specialist seed beetles. Because of the phenotypic diversity of the plants that seems related to defense against insects, the anticipated paradigm is that only specialists would utilize each species as a host. However, the seed beetle Acanthoscelides pullus is able to utilize >25 Astragalus species. This relationship poses a challenge for understanding the nature of specialization and speciation in these seed beetles. There are three alternative scenarios that offer the most plausible explanations: Ac. pullus is a generalist species, a genetically structured species, or an ecologically structured cryptic species. I am using molecular genetic techniques in order to assess patterns of genetic variation that would be predicted based on these different scenarios. I will then use a pairwise population comparisons across host plant and geography in order to estimate the amount of gene flow that occurs between each population. The information obtained from the genetic data and pairwise comparisons allows us to examine whether genetic variation is partitioned via ecological parameters or more neutral geographic parameters.
Does coevolution with toxic milkvetches drive diversification in seed-feeding beetles? Investigation using new genomic techniques.
Plant-insect relationships are among the most common interspecific relationships observed in biology. As these two organisms closely interact with one another, profound effects on adaptation and interaction can be observed. The genus Astragalus (milkvetches) is the most rapidly speciating plant lineage known, with an astounding array of fruit morphology and defensive chemistry. We lack an empirical understanding as to why speciation rates are so high in this genus, but one possibility is that rapid diversification is driven by specialist seed beetles. Because of the phenotypic diversity of the plants that seems related to defense against insects, the anticipated paradigm is that only specialists would utilize each species as a host. However, the seed beetle Acanthoscelides pullus is able to utilize >25 Astragalus species. This relationship poses a challenge for understanding the nature of specialization and speciation in these seed beetles. There are three alternative scenarios that offer the most plausible explanations: Ac. pullus is a generalist species, a genetically structured species, or an ecologically structured cryptic species. I am using molecular genetic techniques in order to assess patterns of genetic variation that would be predicted based on these different scenarios. I will then use a pairwise population comparisons across host plant and geography in order to estimate the amount of gene flow that occurs between each population. The information obtained from the genetic data and pairwise comparisons allows us to examine whether genetic variation is partitioned via ecological parameters or more neutral geographic parameters.