Mate recognition in early lineages of angiosperms:

Most aspects of mate recognition systems cannot be studied in the fossil record. However, there are conspicuous differences between extant gymnosperm and angiosperm lineages with regards to mate recognition. Extant gymnosperms generally do not have pre-fertilization mate recognition, whereas angiosperms generally have varying degrees of both pre- and post-fertilization mate recognition. What kinds of developmental transitions accompanied the origin of pre-fertilization mate recognition in angiosperms? I am addressing this question by studying pre-fertilization mate recognition processes in newly-defined early lineages of angiosperms, focusing initially on self vs. outcross recognition. Because mating systems in plants are mediated by development, not behavior (as in animals), study of mating system evolution is inherently a study of the evolution of development. My lab is undertaking a variety of studies on early lineages of angiosperms, starting with the question of the nature of self versus outcross ontogenies during the progamic phase, the life history period between pollination and fertilization. Mating systems can be strongly influenced by two types of post-pollination processes: competition among male gametophytes and/or differential attrition of male gametophytes. I am currently focusing on Austrobaileya scandens, a vine endemic to the wet tropics region of northeastern Queensland, Australia. At the same time, Mackenzie Taylor is pursuing her Ph.D. on two water lilies, Cabomba and Brasenia (Cabombaceae). Austrobaileya and the Cabombaceae are in the two earliest divergent clades of angiosperms that possess bisexual flowers, the Austrobaileyales and the Nymphaeales, and hence will shed light on the early evolution of post-pollination inbreeding avoidance.

This project is currently funded by NSF.

Phylogeography of Austrobaileya scandens:

In collaboration with Andrew Ford (CSIRO, Atherton, Australia), I am tracing the patterns of genetic diversity in this relict species. Austrobaileya is the sole species within the family Austrobaileyaceae, however its range is today strongly partitioned into two separated distributions. Most populations occur on the eastern side of the small mountain range just southwest of Cairns city, one of the wettest places on earth. The only other populations known, occur in an isolated area of highlands from Mount Lewis and to the northwest on the Carbine plateau. These two areas are separated by the Black Mountain Divide. Formerly some individuals from the Carbine area (Mt. Spurgeon) were described as a separate species, Austrobaileya maculata. To date, we have used nuclear microsatellite and chloroplast PCR-RFLP markers to examine historical patterns of genetic diversity and inbreeding.

Phylogeography of Betula neoalaskana (=B. resinifera):

I have a long-standing interest in the oaks and birches. These open-pollinated trees often have huge geographic ranges, are highly outcrossing and frequently hybridize. Understanding how diversity originates and is maintained in these organisms is quite interesting since most of their life history characters mediate against population divergence (and speciation) even while promoting within-population genetic diversity. A long standing challenge for biologists has been where Alaskan tree species survived the ice ages. It was long thought that trees could not have survived glacial periods as far north as Alaska/Beringia and hence that most tree species either went through periodic local extinctions or range contractions to warmer areas south of the ice sheets. Genetic data from herbaceous plants and some animals seems to indicate that  many organisms survived in Alaska/Beringia during glacial periods. Did the Alaska paper birch and other tree species also survive there? I have been using chloroplast DNA (PCR-RFLPs and microsatellites) as well as nuclear microsatellite data to test alternative refugium hypotheses (Beringia-only, South of the Ice-only, or both). This study is in collaboration with University of Alaska researchers Tom Clausen and John Bryant who have studied geographic patterns of browsing-resistance chemistry that may have evolved in a very few birch generations.