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Abstract—Species in the genus Coccoloba are trees, shrubs, and lianas present in low elevation tropical and sub-tropical forests. Since 1756, well over 400 taxa have been described for Coccoloba. Coccoloba species are natively distributed throughout the New World in a variety of habitats. Despite being distributed throughout the Neotropics, the concentration of Coccoloba species in a given area varies considerably, with four centers of diversity for the genus: southern and coastal Brazil, the West Indies, Mesoamerica, and Amazonia. We here present the first molecular phylogeny of Coccoloba and use this phylogeny to investigate geographic patterns of diversity within the genus. The topology of the phylogeny and the closest related genera to Coccoloba suggest a Mesoamerican origin for the genus. The South American species are recovered as the crown group of the phylogeny with one instance of a separate migration event from Mesoamerica to South America. Coccoloba species in Mesoamerica and the Caribbean show little to no geographic pattern to their diversification. Mesoamerica and the Caribbean are best considered as one phytogeographic region for Coccoloba.

Rumex is one of about 50 genera in the knotweed family, Polygonaceae. The genus comprises about 200 species with bisexual, or more commonly, unisexual flowers, with the species displaying monoecious, dioecious, synoecious (hermaphroditic) or polygamous reproductive systems. Some of the dioecious species have heteromorphic sex chromosomes, which is rare amongst angiosperms. We here present a plastid phylogeny of 67 species, representing all four subgenera. For this study, we used three chloroplast markers, rbcL, trnH-psbA, trnL-F and dense taxon sampling to reconstruct the most comprehensive molecular phylogeny of Rumex to date. The reconstructed phylogeny for this work resolves six major clades and one large grade in Rumex subg. Rumex. In addition, the species with known dioecious reproductive systems are resolved within a broader clade we term “the dioecious clade”. These results suggest that the species with divergent reproductive systems are more closely related to each other than to other species comprising the rest of the Rumex genus.

The genus Rumex is a unique member of the Polygonaceae (Buckwheat) family of plants. A source of intrigue for Rumex lies in the diversity of the reproductive systems associated with the subgenera, species, and subspecies within this genus. Four previously circumscribed subgenera, some 200 species, and a number of subspecies comprise the collective Rumex genus. These species exhibit monoecious, dioecious, synoecious (hermaphroditic), and polygamous reproductive systems. Moreover, some of the dioecious species contain sex chromosomes, a phenomenon that is very rare in angiosperms. Apart from the confirmed morphological and phytogeographical distinctions, two of the four described subgenera, Acetosa and Acetosella, are distinctive in their exhibited sex chromosome systems. For this study, we used three chloroplast markers, rbcL, trnH-psbA, trnL-F, and dense taxon sampling, to reconstruct a molecular phylogeny for Rumex.The reconstructed phylogeny for this work resolves six major clades and one large grade in Rumex. In addition, the species with known dioecious reproductive systems derived from unique sex chromosome systems are resolved in two different clades nested within “the dioecious clade”. These results suggest that the species with divergent sexual systems are more closely related to each other than to other species comprising the rest of the Rumex genus. Furthermore, some species with known synoecious reproductive systems are resolved in a single clade which is also nested within “the dioecious clade”. These results imply a possible reversal occurring over time which suggests the highly plastic nature of reproductive systems among Rumex species.

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The majority of angiosperms (~94 %) are synoecious, with only a small minority separating the production of the two gamete types onto different biological individuals (dioecy). For many plant species, however, reproductive systems and habits are not well documented. This is particularly true of tropical trees, which, despite their conspicuity, are poorly understood. Plants in the genus Triplaris have been consistently described as strictly dioecious. After morphologic analysis using a dissecting microscope, here I present a number of fully-formed perfect (hermaphroditic) flowers observed on Triplaris herbaria specimens.