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Eifler, Evan [1], Karimi, Nisa [2], Lemmon, Alan R. [3], Lemmon, Emily M. [4], Givnish, Thomas [5].

Patterns of Species Diversification in Geissorhiza (Iridaceae): Phylogeny, Biogeography, and Vulnerability in the Cape Floristic Region.

The Greater Cape Floristic Region (GCFR) of southwestern South Africa harbors an exceptionally rich angiosperm flora with a higher proportion of endemic species than any other continental landmass, and is the biodiversity hotspot for the iris family (Iridaceae). 33 clades in 24 families account for half of GCFR diversity; most are specialized on either extremely infertile, sandy soils associated with fynbos, or on richer, heavier soils associated with renosterveld plant communities. Geissorhiza (106 described species) in 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 geophytic 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, 68 of its species are of conservation concern, and 16 are known only from a single location on Earth. We derived molecular phylogenies for Geissorhiza based on sequencing 436 nuclear loci (via anchored phylogenomics) and entire plastomes and use these to revise subgeneric divisions. We will explore patterns of congruence and discordance within the nuclear data and between the nuclear and plastome data and examine what this means for limited patterns of hybridization and incomplete lineage sorting. We calibrated the plastome tree against time by embedding it in a fossil-calibrated monocot plastome phylogeny. Finally, we used both nuclear and plastome trees to reconstruct the historical biogeography of Geissorhiza, infer patterns in the evolution of floral form, soil, climatic niche, and extreme rarity, 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. We will highlight the multiple origins of a rare alpine floral morphology, life in waterfalls, and the convergent evolution of similar floral forms involved in the apparent floral mimicry of the five ‘winecup’ species of Geissorhiza and Babiana. Collectively, this work will shed substantial light on the evolution, geographic spread, and diversification of Geissorhiza, a hallmark genus of megadiverse southwest South Africa.

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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, United States
3 - Florida State University, 400 Dirac Science Library, Dept. of Scientific Computing, Tallahassee, FL, 32306, United States
4 - Florida State University, 89 Chieftain Way, Biology Unit 1, Tallahassee, FL, 32306, United States
5 - University Of Wisconsin-Madison, Department Of Botany, Birge Hall, 430 Lincoln Drive, Madison, WI, 53706, United States

Cape Floristic Region
Trait evolution

Presentation Type: Oral Paper
Session: PHYLOV, Phylogenomics V
Location: Virtual/Virtual
Date: Friday, July 23rd, 2021
Time: 3:45 PM(EDT)
Number: PHYLOV004
Abstract ID:958
Candidate for Awards:None

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