Abstract Detail

Systematics

Vargas, Oscar M [1], Simpson, Beryl [2].

Reticulate evolution and recent diversification in Andean Compositae (Astereae: Diplostephium).

Rapid diversification events are often associated with the colonization or emergence of new habitats such as island systems or mountain ranges. These landscapes provide opportunities for lineages to diverge rapidly via allopatric and ecological speciation. Taxa in which recent diversifications events have occurred are usually characterized by low molecular divergence and high morphological variation. The recency of these events poses a challenge to the phylogenetic inference of such lineages because of the low divergence expected in their DNA sequences. With a complex topography and a recent orogeny (5–20 my), the Andes Cordillera is a hotspot for plant biodiversity and an ideal region to study recent plant speciation events. The genus Diplostephium s.l. is a main component of the high Andean flora comprising 111 species of shrubs and small trees. The present study elucidated the phylogenetic patterns of Diplostephium and its allies using genome skimming sequencing. We sequenced a total of 91 samples, 74 from Diplostephium species, 13 from allied genera, and 3 from outgroups. A bioinformatic workflow adjusted specifically to the characteristics of each genomic region was used to construct three matrices: the complete nuclear ribosomal cistron, the complete chloroplast genome, and a partial mitochondrial genome. All the topologies obtained are generally well resolved and with high support. We found significant incongruences between the three datasets suggesting that they represent different genome histories. We attribute the major incongruences between datasets to reticulate evolution resulting from multiple events of hybridization and introgression for which morphological and geographical support is present. These events primarily biased the uniparentally non-recombinant chloroplast and mitochondrial genome histories confounding their phylogeny from the species tree. Therefore, of the three datasets, we propose the nuclear ribosomal phylogeny as the best species-tree hypothesis. The nuclear ribosomal phylogeny revealed that Diplostephium s.l is polyphyletic with most species comprising two large well-supported distantly related clades. Finally, our results suggest recent acceleration of diversification rates driven by isolation and ecological divergence. We conclude that reticulation played an important role in the evolutionary history of Diplostephium s.l. and its allies; chloroplast and mitochondrial phylogenies are biased due to processes of hybridization and introgression in relation to the species-tree; and isolation and ecological divergence worked synergistically to accelerate rates of diversification after Andean uplift.

Related Links:
First author and project website

1 - The University of Texas at Austin, Integrative Biology and the Plant Resources Center, 1 University Station C0930, Austin, TX, 78712, USA
2 - University Of Texas, Section Of Integrative Biology, 205 W 24th St, Mail Stop C0930, Austin, TX, 78712, USA

Keywords:
Andes
Asteraceae
Diplostephium
genome skimming
historical biogeography
hybridization
introgression
phylogenomics
rapid diversification
reticulate evolution
species tree.

Presentation Type: Oral Paper
Session: 21, Cooley Awards I
Location: 201/Savannah International Trade and Convention Center
Date: Tuesday, August 2nd, 2016
Time: 8:00 AM
Number: 21001
Abstract ID:84
Candidate for Awards:George R. Cooley Award