Phylogeny, systematics, and biogeography of Acridocarpus and other old world Malpighiaceae

Chapter 1. Infrafamilial classification of the tropical angiosperm lineage Malpighiaceae has been based almost entirely on fruit characters. Phylogenetic evidence from cholorplast ndhF and trnL-F data has revealed that nearly all of the major taxonomic groupings within Malpighiaceae are non-monophyletic, suggesting extensive convergence on similar fruit types. Furthermore, these data have revealed that the Old World Malpighiaceae are variously related to at least six different lineages, each of which are more closely related to New World clades.; Chapter 2. Madagasikaria andersonii is described as a new genus and species of Malpighiaceae from Madagascar. It forms a strongly supported clade with the Malagasy endemic genera Rhynchophora and Microsteira and is easily distinguished from these taxa on fruit morphology. The madagasikarioids are morphologically androdioecious and functionally dioecious, producing both staminate and “bisexual” (i.e., functionally carpellate) individuals. The madagasikarioids represent one departure from the specialized floral and pollination system of neotropical malpighs.; Chapter 3. Biogeographical explanations for Malpighiaceae traditionally invoke vicariance or dispersal, both of which are problematical. Chloroplast ndhF and nuclear PHYC data suggest a new explanation for the distribution of Malpighiaceae. Given that (1) Malpighiaceae appear to have originated in South America, (2) there are six separate New World-Old World disjunctions within Malpighiaceae, and (3) there are excellent fossils of this group from the Northern Hemisphere, I postulate migration northward out of South America via the nascent Caribbean region and then eastward via a North Atlantic “land bridge” during several episodes in the Tertiary. This Laurasian migration may have been a general route, which was episodic and bidirectional, whereby some Gondwanan distribution patterns originated.; Chapter 4. A major tenet of African Tertiary biogeography posits that lowland rainforest dominated much of Africa in the late Cretaceous and was replaced by xeric vegetation as a response to widespread aridification resulting primarily from continental uplift beginning in the late Paleogene. I tested this geologically based model with independent phylogenetic evidence (using ITS, ndhF, and trnL-F) from the widespread African plant group Acridocarpus, which contains both humid- and xeric-adapted species. Dispersion of Acridocarpus from Africa to Madagascar is inferred between ∼50 and ∼34 mya, when lowland humid tropical forest was nearly continuous between these landmasses. A single dispersal event within Acridocarpus is inferred from western Africa to eastern Africa between ∼23 and ∼17 mya, coincident with the widespread replacement of humid forests by savannas in eastern Africa. Although the spread of xeric environments resulted in the extinction of some African plant groups, these data suggest that for others it provided an opportunity for further diversification.