Biology Department

Research Overview

Ramsey Lab Website

The Ramsey lab combines molecular analyses, greenhouse studies and field experiments to address classical questions about speciation and adaptation in flowering plants. As is traditional in our area of research, we work on a diversity of non-model plant taxa selected on the basis of natural history rather than tractability to genetic analysis. Ongoing research projects are outlined below.

WILD YARROW

Achillea borealis (Asteraceae) is a widespread complex of ecological races occuring in diverse climatic and edaphic conditions throughout North America. The species is notorious for its taxonomic complexity, incidence of polyploidy and profound degree of local adaptation. Our studies have three foci. (1) Characterization of historical relationships in the circumpolar Achillea millefolium aggregate using DNA sequence data (cpDNA, single copy nuclear genes) and molecular markers (AFLPs, microsatellites). (2) Evaluation of autopolyploidy as mechanism of adaptive divergence and incipient speciation, based on comparisons of naturally-occuring polyploids ("established" polyploid populations) vs. neopolyploids (spontaneous polyploid mutants screened from diploid progenitors). (3) Analysis of the phenotypic and genetic basis of climatic and edaphic adaptation, inferred from classical approaches (segregation of traits in hybrid pedigrees) and modern methods (candidate genes).

ENGLISH IVY

Ivy (Hedera spp, Araliaceae) is a woody vine that is native to Eurasia but cultivated worldwide for its attractive foliage, hardiness and ease of propogation. Ivy is also a serious pest in forest environments along the Atlantic Seaboard and Pacific Coast of North America. Despite its horticultural value and ecological impacts, many aspects of ivy phylogeny, biogeography and invasion biology are poorly understood. Our work involves four major projects. (1) Characterization of Hedera phylogeny based on DNA sequence data (cpDNA, single copy nuclear genes) and molecular markers (microsatellites). (2) Analysis of the taxonomic composition and population genetic structure of invasive ivy populations in North America using cpDNA and flow cytometry. (3) Evaluation of species-differences in invasiveness, inferred from field observations and experiments. (4) Characterization of fruit dispersal and seedling recruitment in cultivated and naturalized ivy populations.

CREOSOTE BUSH

Creosote Bush (Larrea tridentata, Zygophyllaceae) is a dominant shrub across the Mojave, Sonoran and Chihuahuan deserts of the southwestern U.S. and northern Mexico. This taxonomic species is comprised of diploid, tetraploid and hexaploid "races" that replace each other along a longitudinal gradient. We are working on three major projects in this system. (1) Characterization of phylogeography and population structure of L. tridentata in comparison to its South American relatives, based on DNA sequence data (cpDNA, single copy nuclear genes). (2) Analysis of pre-zygotic barriers (habitat isolation, phenological isolation) and post-zygotic barriers (triploid block, sterility) isolating diploid and autopolyploid races of L. tridentata as inferred from field observation and experiments. (3) Evolutionary rates of host specialization by Larrea herbivores and pollinators.