TRIPP, Erin, A.; Duke University: Nothing happens once: systematics and parallel evolution in the species-rich genus Ruellia (Acanthaceae)
The genus Ruellia (Acanthaceae) comprises ca. 300 species, is largely herbaceous, and is primarily tropical or subtropical in distribution. Ruellia is ecologically and evolutionarily interesting because of its diversity in floral and vegetative morphology, habit, and reproductive strategies. Using Bayesian and parsimony methods, molecular phylogenetic analyses of 200 spp. of Ruellia and 45 additional taxa in tribe Ruellieae were conducted to test the monophyly of the genus, elucidate patterns in biogeography, and reconstruct the evolution of pollination syndromes, breeding systems, and plant habit. While the monophyly of Ruellia has been historically doubted, results from this study indicate that the genus is indeed natural and nested within Ruellieae. The geographic distribution of basal lineages of the genus as well as neighboring outgroups suggest an �out-of-Madagascar� scenario for its origins, with dispersal to and radiation in Central and South America. Hummingbird pollination has evolved at least 7 times, hawkmoth pollination 5 times, and bat pollination at least 3 times. Cleistogamy, or the production of closed, obligately self-fertilizing flowers, has evolved at least 4 times. This reproductive strategy may facilitate population establishment and growth following a dispersal event. Both liana and tree habits have evolved multiple times. Bat pollination is often associated with one of these habits and may have evolved as a consequence of more aerial flower production. Finally, floral resupination, or the twisting of flowers during development that in Ruellia results in an upside-down orientation of reproductive parts, is also documented for the first time in this genus. It has evolved multiple times, often in association with bat pollination. The ability of species of Ruellia to exploit a wide range of niches, pollinator communities, and reproductive strategies probably helps explain its diversity and widespread distribution.
