Neotropical Plant Evolution: Assembling the Big Picture

Abstract

This paper and this issue attempt to address how, when and why the phenomenal c. 100,000 species of seed plants in tropical America (the Neotropics) arose. It is increasingly clear that an approach focusing on individual major biomes rather than a single aggregate view is useful because of evidence for differing diversification histories among biomes. Phylogenetic evidence suggests that Neotropical‐scale diversification patterns are structured more ecologically than geographically, with a key role for phylogenetic niche or biome conservatism. Lower geographical structure reflects the fact that long‐distance dispersal, inferred from dated phylogenetic trees, has overcome many supposed dispersal barriers. Overall, high rates of species turnover as inferred from palaeontological and molecular data have been the hallmark of plant evolutionary dynamics in the Neotropics throughout the Cenozoic, with most extant species diversity post‐dating the Mid‐ to Late Miocene, perhaps reflecting the conjunction of both global climatic changes and geological upheavals such as the Neogene uplift of the tropical Andes. Future studies of Neotropical diversification will be facilitated by taxonomically and genetically better sampled phylogenetic analyses, their integration with palaeontological, geological and ecological data, and improved methods to estimate biogeographic history and diversification dynamics at different spatial and temporal scales. Future biome‐focused approaches would benefit greatly from better delimitation and mapping of Neotropical biomes. © 2012 The Linnean Society of London

Time-Calibrated Phylogenies of Hummingbirds and Hummingbird-Pollinated Plants Reject a Hypothesis of Diffuse Co-Evolution

“…This study corroborates a growing consensus (e.g., Hughes et al 2013) that full explanation of high Neotropical diversity will require synthesis of multiple ideas regarding sources of diversity, including both abiotic and biotic axes of speciation, as well as phylogenetic studies of lineages that occur in the New World. We anticipate contributing to this synthesis by expanding sampling of New World Ruellia to study phylogenetically patterned correlates of diversity in a spatio-temporal context.…”

Model-based analysis supports interglacial refugia over long-dispersal events in the diversification of two South American cactus species

“…Most of these studies focused in the Northern Hemisphere (Beheregaray, 2008), and tried to identify putative species refugia by locating regions of the species' range that contain high levels of genetic diversity and were also ice-free during glaciation (Keppel et al, 2012). The paucity of data for South American species, particularly for those adapted to open and/or dry habitat types, has greatly hindered the understanding about diversification mechanisms in the continent (Hughes et al, 2013;Turchetto-Zolet et al, 2013). Despite the controversy about Haffer's (1969) forest refuge hypothesis (for example, Hoorn et al, 2010;Rull 2011), many species associated with mesic vegetation display similar patterns (Turchetto-Zolet et al, 2013;Garzón-Orduña et al, 2014) that are consistent with the tropical refugial hypothesis.…”

Plant diversity patterns in neotropical dry forests and their conservation implications

“…The lowest percentage of exclusive species is found in central Brazil dry forests, which reflects the larger numbers of species shared with neighboring floristic groups. Despite their close geographical proximity, Andean floristic groups each have about 30 to 40% of exclusive species, reflecting high floristic turnover at relatively small spatial scales, which may be caused by dispersal limitation among the geographic groups and in situ speciation within them (1,28).…”

“…These patterns contrast strongly with the rain forests of Amazonia (33,34) and the savannas of central Brazil (30), which are often dominated by a suite of oligarchic species over large geographic areas. The lack of an oligarchy of widespread, dominant dry forest species reflects the limited opportunities for dispersal and successful establishment among dry forest areas (1,28).…”