Diversification in the Andes: Age and origins of South American Heliotropium lineages (Heliotropiaceae, Boraginales)

Freie Universität Berlin, Institut für Biologie - Botanik, Altensteinstraße 6, D-14195 Berlin, Germany.
Molecular Phylogenetics and Evolution (Impact Factor: 3.92). 06/2011; 61(1):90-102. DOI: 10.1016/j.ympev.2011.06.001
Source: PubMed


The uplift of the Andes was a major factor for plant diversification in South America and had significant effects on the climatic patterns at the continental scale. It was crucial for the formation of the arid environments in south-eastern and western South America. However, both the timing of the major stages of the Andean uplift and the onset of aridity in western South America remain controversial. In this paper we examine the hypothesis that the Andean South American groups of Heliotropium originated and diversified in response to Andean orogeny during the late Miocene and a the subsequent development of aridity. To this end, we estimate divergence times and likely biogeographical origins of the major clades in the phylogeny of Heliotropium, using both Bayesian and likelihood methods. Divergence times of all Andean clades in Heliotropium are estimated to be of late Miocene or Pliocene ages. At least three independent Andean diversification events can be recognized within Heliotropium. Timing of the diversification in the Andean lineages Heliotropium sects.Heliothamnus, Cochranea, Heliotrophytum, Hypsogenia, Plagiomeris, Platygyne clearly correspond to a rapid, late Miocene uplift of the Andes and a Pliocene development of arid environments in South America.

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    • "Another possibility for lower divergence among the South American taxa is that radiation and speciation has, in general, been more recent in the Andes than in Mexico. The low diver­ gence among members of the Andean clade fits a pattern seen in several other groups in the Andes where relatively recent uplift has provided environments for colonization (Hughes & Eastwood, 2006; Drummond, 2008; Luebert & al., 2011). Even the most divergent species in South America are only half as divergent as the most divergent Mexican taxa. "
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    ABSTRACT: Coreopsis (Asteraceae) sect. Pseudoagarista is the largest section in the genus. It is disjunct between the high mountains of Mexico and high elevations in the Andes. Most species in the section are similar in floral and fruit characters, and are distinguished primarily by leaf characters. Despite the morphological similarity among all species, the monophyly of the section has been called into question by molecular data. Prior studies of tribe Coreopsideae have been equivocal with, cpDNA markers indicating monophyly but nrDNA ITS sequences have not resolved the section as monophyletic. Expanded cpDNA and nrDNA ITS datasets, and statistical (i.e., AU) tests of the ITS and cpDNA topologies provide support that sect. Pseudoagarista is not monophyletic. Both data partitions strongly support the Mexican and South American subclades as monophyletic. The low cpDNA sequence variation within each subclade provides no resolution, and thus patterns of evolution within each were examined using a phylogenetic framework estimated from ITS data. Sequences from ITS fail to provide high resolution of relationships among South American species, a likely result of a recent, rapid radiation, as is known in other Andean lineages. Divergence among species is generally higher in the Mexican species, resulting in better resolution of phylogenetic relationships compared to South American species. Three ploidy levels (diploid, tetraploid, hexaploid) are known in species from South America, and diploids and tetraploids have been documented in Mexico. Multiple origins of polyploidy are indicated for both geographic areas.
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    • "Cochranea underwent an adaptive radiation toward the early Pliocene in response to the aridification of the Atacama Desert (Luebert and Wen 2008; Luebert et al. 2011a,b2011b). However, sister relationships are largely unresolved, and little is known about the ecological and genetic forces as well as the spatial and temporal dynamics implied in its diversification. "
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    • "A high diversity of Stachys species is also found in South America (SA), particularly in the Andean region. The powerful effect of the Andean orogeny has led to rapid diversification and radiations in the Andean flora (Luebert et al., 2011), and the Andean mountain ranges with their high altitude flora are the seat of a variety of species (Marx et al., 2010; Tank and Olmstead, 2009; Turchetto-Zolet et al., 2013). The rapid radiation in this region is comparable in many instances to that observed in oceanic islands (Drummond et al., 2012; Hughes and Eastwood, 2006). "
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