Abstract Detail

Molecular Ecology

Eifler, Evan [1], Givnish, Thomas [2], Lemmon , Alan [3], Lemmon, Emily [4], Johnson, Steven [5].

Drivers of Species Diversification and Floral Mimicry in Geissorhiza (Iridaceae): Phylogeny, Biogeography, and Vulnerability in the Greater Cape Floristic Region.

The Greater Cape Floristic Region (GCFR) of southwestern South Africa harbors an exceptionally rich angiosperm flora with ~9000 species inhabiting an area of only 90,000 km2, greatly exceeding the diversity of any region of comparable climate on Earth and with a higher proportion of endemic species than any other continental landmass. It is thus an exceptional laboratory for studies of plant evolution, well-equipped to help answer questions relating to how and why plant species are generated and maintained. Thirty-three clades account for half this diversity; most are specialized on either extremely infertile, sandy soils associated with fynbos, or on much richer, heavier soils associated with renosterveld plant communities. Geissorhiza (103 described species, Iridaceae subfamily Crocoideae) is an exception and has apparently speciated extensively in both fynbos and renosterveld. It is one of the largest genera wholly restricted to the GCFR, where it occurs across a wide range of soil textures, elevations, and hydrological regimes, exhibits striking variation in floral form, and shares the bulbous habit that characterizes such a large share of the GCFR flora. In addition, the flowers of six species of Geissorhiza appear to closely mimic co-flowering irids, sixty-eight of its species are of conservation concern, and sixteen are known only from a single location on Earth.
Our research project opens a multifaceted window on plant evolution in the GCFR through the lens of Geissorhiza, one of the GCFR’s most remarkable plant genera. We are deriving a molecular phylogeny for Geissorhiza based on sequencing 512 nuclear loci and entire plastomes, nested within a study of generic relationships within the mostly southern African Iridaceae subfamily Crocoideae. We will calibrate this tree against time by embedding it in the dated monocot plastome tree, and use it to reconstruct historical biogeography within Geissorhiza and Crocoideae, infer patterns in the evolution of floral form, pollinators, soils, and climatic niches in Geissorhiza, estimate net rates of species diversification, and relate the latter to plant and habitat characteristics to quantify the extent to which shifts in pollinators, soils, and climatic variables help determine diversity within the genus. Here we present preliminary phylogenetic results comparing nuclear and plastome trees highlighting the independent evolution of similar floral forms involved in the floral mimicry of the five ‘winecup’ species of Geissorhiza and Babiana. This multi-faceted project should shed substantial light on the evolution, geographic spread, and diversification in Geissorhiza, a hallmark genus of megadiverse southwest South Africa.

1 - UW Madison, Botany, 430 Lincoln Dr., Madison, WI, 53706, United States
2 - University Of Wisconsin-Madison, Department Of Botany, 430 Lincoln Drive, Madison, WI, 53706.0, United States
3 - Florida State University, Scientific Computing, 400 Dirac Science Library, Tallahassee, FL, 32306-4120, USA
4 - Florida State University, Biological Sciences, 213 Biomedical Research Facility, Tallahassee, FL, 32306-4120, United States
5 - SCHOOL OF BIOLOGICAL AND CONSERVATION SCIENCES/UNI, Private Bag X101 Scottsville, Pietermaritzburg, 3209, South Africa

Floral mimicry
Greater Cape Floristic Region
adaptive radiation.

Presentation Type: Poster This poster will be presented at 6:15 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PME004
Abstract ID:1073
Candidate for Awards:None

Copyright © 2000-2019, Botanical Society of America. All rights reserved