The systematics and evolution of Lantaneae (Verbenaceae), a molecular phylogenetic approach

Abstract

Lantaneae are a morphologically variable group of 300-400 species, representing the largest tribe within Verbenaceae. They are widespread and diverse in the new world tropics and subtropics; some members are native to Africa, and others, most notably the <italic>Lantana camara</italic> complex, have spread across the globe as noxious weeds. Complex patterns of morphological parallelism have hindered taxonomic efforts within Lantaneae, and previous molecular phylogenetic studies have failed to resolve relationships within the tribe. The lack of variability among loci commonly used to infer phylogeny at the species level in plants suggests that Lantaneae are recently radiated. With growing interest in the taxonomy of this difficult group, and growing recognition of the worldwide ecological and economic impacts of <italic>Lantana camara</italic>, there is a clear need for a well resolved phylogenetic hypothesis for Lantaneae. Species-level phylogenetic reconstruction in taxonomically complex, recently radiated lineages is a major challenge in plant systematics, and represents an opportunity to test the limitations of the molecular methods that are currently prevalent in modern systematic biology. Here, I have taken a multi-locus approach to resolve the pattern of diversification among a broad representative sample of the morphological, taxonomic, and geographic diversity of Lantaneae, demonstrating the effectiveness of the PPR gene family as phylogenetic tools. The results reveal that major genera are not monophyletic, with <italic>Lantana</italic> species belonging to two main clades, derived within a background of <italic>Lippia</italic> species. The small African genus <italic>Coelocarpum</italic> is the sister group to the tribe. Different loci reconstruct the species of <italic>Aloysia</italic>, and its affiliated genera, differently: either in a paraphyletic grade to the <italic>Lantana-Lippia</italic> complex, or as its sister group. A species tree reconstruction supports the hypothesis of sister clades. Within the <italic>Lantana-Lippia</italic> complex, fleshy fruits have evolved four times independently from dry-fruited ancestors, and are associated with higher speciation rates. At a broad scale, there is no clear pattern suggesting that fleshy fruits confer a dispersal advantage over dry fruits. My results place the origin of core Lantaneae in the Miocene, in subtropical South America, with different lineages subsequently migrating independently throughout the neotropics, into North America, and twice to Africa.