Phylogeny, biogeography, and rates of diversification of New World Astragalus (Leguminosae) with an emphasis on South American radiations

• DOI: 10.3732/ajb.0800017
• Publication Date: 2008-07-23T16:53:12Z
• Authors: Rosa A. Scherson; Rodrigo Vidal; Michael J. Sanderson
• Keywords: 0106 biological sciences; Astragalus; 15. Life on land; 01 natural sciences

This study uses phylogenetic relationships of New World representatives the species-rich genus Astragalus (Leguminosae; Papilionoideae) to follow up on recent evidence pointing rapid and plant diversification patterns in Andes. Bayesian maximum likelihood analyses were done using nuclear rDNA ITS chloroplast spacers trnD-trnT trnfM-trnS1, either separately or combination. The effect partitioned vs. nonpartitioned a approach was evaluated. Highest resolution obtained when data combined analyses. All phylogenies support two clades South American species nested within North species, implying separate invasions from America. These correspond original morphological classification Johnston (1947 Journal Arnold Arboretum 28: 336-409). mean ages very but still significantly different (1.89 0.98 Ma). Upper lower bounds rates varied between 2.01 0.65 species/Ma for older clade 2.06 1.24 younger clade. Even are high, reasserting Neo-Astragalus growing list radiations plants, especially areas with high physiographic diversity, such as