Document Type

Dissertation

Degree

Doctor of Philosophy

Major

Biology, Plant Systematics

Date of Defense

8-3-2011

Graduate Advisor

Elizabeth A. Kellogg

Committee

Dr. Kathleen Haywood

Thomas B. Croat

Peter M. Richardson

Simon J. Mayo

Abstract

Anthurium is a strictly neotropical genus of Araceae ranging from southern Mexico to northern Argentina, including ca. 900 species and displaying an enormous variation in leaf morphology, growth habit, leaf venation pattern and inflorescence and fruit colors. Despite its immense diversity, its ecological importance in Neotropical forests, and a very long history of botanical collection, cultivation, and taxonomical research, Anthurium had been almost neglected in molecular phylogenies. This study combines chloroplast (trnG intron, trnH-psbA and trnC-ycf6 intergenic spacers) and nuclear (CHS first intron) DNA sequence data for 102 Anthurium species and uses maximum parsimony, likelihood and Bayesian phylogenetic analysis to test the monophyly of Anthurium, to elucidate relationships among its species, to test statistically the validity of the currently accepted sectional classification and its associated morphological characters, and to study the pattern of Anthurium species diversification through time. Results show that Anthurium is monophyletic and that at least 20 highly supported (bootstrap values > 70% and/or posterior probabilities > 0.90) major clades are recognizable within it, most of them easily characterized morphologically and/or geographically. Despite giving a better idea about the evolutionary history of the genus, resolution is still lacking in the deeper nodes of the phylogeny. This study suggests that the current sectional classification of Anthurium does not accurately represent its evolutionary history. Most of the major clades do not correspond with the circumscriptions of infrageneric groups and morphological characters used in the sectional classification are in fact highly homoplasious within Anthurium. This study also reveals that there is very low sequence divergence among Anthurium species, and relatively short branches characterize the core of the Anthurium clade. Although the stem node of Anthurium is quite old (Late Cretaceous), species diversification did not start until quite recently – the crown node age is dated to Late Oligocene, and the bulk of species diversification did not occur until even later, during the Late Miocene (ca. 8-9 Mya). Anthurium species diversification through time is indeed consistent with the pattern of a rapid radiation, having a diversification rate of approximately 0.61-0.69 species per million years.

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