Timothy P. Holtsford
Associate Professor of Biological Sciences
| E-mail: | holtsfordt@missouri.edu |
 |
| Office Phone: | (573) 882-3016 | |
| Lab Phone: | (573) 882-2988 | |
| Fax: | (573) 882-0123 | |
| Office: | 202 Tucker Hall | |
| Mailing Address: |
Biological Sciences
105 Tucker Hall University of Missouri-Columbia Columbia, MO 65211 |
|
| Research Areas: |
Floral evolution; systematics; molecular evolution. |
Research Description
We are interested in the population genetic processes that influence floral evolution, species divergence and changes in the mating system in flowering plants. The impressive floral radiation of Nicotiana Section Alatae (Fig. 1) provides opportunities to study plant-pollinator interactions and the evolution of self-pollination.
We have worked on the pollinator-associations and their contribution to the species boundary between N. alata (pollinated by hawkmoths) and N. forgetiana (hummingbirds) (Ippolito et al., 2004), nectar variation and its relation to pollinator associations in all 8 spp. (Kaczorowski et al. 2005, Raguso et al. 2006), and crossability and pollen tube growth rates in crosses among all species (Lee et al., in prep).
Our current projects are focused on the evolution of self-pollination in N.longiflora and N. plumbaginifolia. Nicotiana plumbaginifolia is autogamous and self-pollinates before flower opening. Self-fertilization is a very effective gene flow barrier and has certainly contributed to the divergence of N. plumbaginifolia from N. longiflora, resulting in a long branch supporting the N. plumbaginifolia clade. N. longiflora includes three morphologies and mating systems. Most of N. longiflora is predominantly outcrossing, encouraged by spatial and temporal separation of male and female function, yet it is self-compatible (SC). Second, a mid-size morph, a putative hybrid, is found in the hybrid zone between N. plumbaginifolia and N. longiflora in NW Argentina. In the midsize morph stigma receptivity and anther dehiscence occur simultaneously, and with very little spatial separation, presenting a competitive arena for selfed vs. outcrossed pollen for ovule access. The third mating system is self-incompatibility (SI), a genetically determined rejection of selfed pollen, which is segregating in at least one population found in NW Argentina.
Our current experimental approaches include genetic marker development for quantitative trait locus (QTL) identification; quantitative and Mendelian genetics; pollen tube growth dynamics using light microscopy; and natural and synthetic population experiments in natural habitats, the glasshouse and the MU Genetics Farm.
Figure 1. Phylogenetic hypothesis for Alatae based on 298 ISSR bands, treated as (0, 1) characters in PAUP* parsimony, with bootstrap values above the branches. A population designation follows the sp. abbreviation: N. alata = ala, forgetiana= forg, langsdorfii= lang, mutabilis=mut, putative sp. rastroensis = rastro, longiflora = long, plumbaginifolia = plum.
Selected Publications
Lee, C., L. Page, B. A. McClure and T. P. Holtsford. Pollen tube growth rates are correlated with style length and contribute to the asymmetric Biological Species Concept boundaries in Nicotiana Section Alatae (Solanaceae). In prep. for Heredity.
Raguso, R.A., B. O. Schlumpberger, R. Kaczorowski and T. P. Holtsford. 2006. Tobacco floral scent revisited: geographic variation and new species in Nicotiana sections Alatae and Suaveolentes. Phytochemistry 67:1931-1942.
Buckler, E. S., M.M. Goodman, T.P. Holtsford, J.F. Doebley, and J. Sanchez-G. 2006. Phylogeography of the wild subspecies of Zea mays. Maydica 51:123-134.
Kaczorowski, R.L. M. C. Gardener, and T. P. Holtsford. 2005. Nectar traits and availability in Nicotiana Section Alatae (Solanaceae) in relation to primary pollinators and mating system. American Journal of Botany. 92:1270-1283
Ippolito, A., G.W. Fernandes and T.P. Holtsford, 2004. Pollinator preferences for Nicotiana alata, N. forgetiana and their F 1 hybrids. Evolution 58:2634-2644.
