Abstract Detail

Systematics Section/ASPT

Gagnon, Edeline [1], Lewis, Gwilym [2], Hughes, Colin [3], Bruneau, Anne [4].

A molecular phylogeny with increased sampling of Caesalpinia sensu lato and the Caesalpinia Group: more genera than expected and new insights in the biogeography of this pantropical group.

Phylogenies that concentrate on higher-level systematics are important to study macro-evolutionary and biogeographic patterns. Caesalpinia sensu lato (Leguminosae), in its broadest circumscription, is a pantropical group of c.150 species of trees, shrubs and lianas many of which grow in arid habitats of the Succulent Biome (sensu Schrire, 2005), and especially in the Seasonally Dry Tropical Forests (SDTFs) of Central and South America and the Caribbean. Because of its widespread distribution, Caesalpinia s.l. can be used as a model to investigate the evolution of this biome on a pantropical scale. However, the taxonomic uncertainty regarding the delimitation of some of the segregate genera within Caesalpinia s.l. must first be clarified. As traditionally circumscribed, Caesalpinia s.l. is one of the largest genera in tribe Caesalpinieae, but seven generic segregates recently were reinstated by Lewis (2005), namely Coulteria, Erythrostemon, Guilandina, Libidibia, Mezoneuron, Poincianella, Tara, leaving a Caesalpinia sensu stricto highly reduced in species number compared with Caesalpinia s.l. Nevertheless, a number of doubts remain regarding the delimitation of some of these segregate genera, and this has hindered the understanding of the evolution of the broader Caesalpinia Group, which currently recognizes a total of 21 genera, including the eight genera mentioned above. Based on a broad taxonomic sampling of 18 genera of the Caesalpinia Group and 98 species belonging to Caesalpinia s.l. sequenced for plastid and nuclear loci (e.g., rps16, trnD-trnT, ycf6-psbmR, ITS),we present here significant advances in the understanding of evolutionary relationships amongst groups of species within Caesalpinia s.l. Our results support the monophyly of five of the genera reinstated by Lewis, but the three other genera (including Caesalpinia s.s.) are non-monophyletic and need to be reevaluated. Furthermore, three robustly supported newly discovered clades within Caesalpinia s.l. potentially merit recognition as distinct genera pending complete investigation of diagnostic morphological characters. In conjunction with a preliminary dating analysis, our findings suggest that Caesalpinia s.l. and the Caesalpinia Group may have a pattern of diversification that is similar to that seen in many other legumes and other plant taxa growing in the Succulent Biome.

Broader Impacts:

1 - Institut de Recherche en Biologie Végétale, Université de Montréal, Département de Sciences biologiques, 4101 rue Sherbrooke est, , Montréal, QC, H1X 2B2, Canada
2 - Royal Botanic Gardens - Kew, HERBARIUM ROYAL BOTANIC GARDEN, Richmond, Surrey, TW9 3AE, United Kingdom
3 - University of Zurich, Department of Plant Sciences, Zollikerstrasse 107, Zürich, N/A, 8008 Zürich, Switzerland
4 - University of Montreal, Institut de recherche en biologie végétale, 4101 rue Sherbrooke Est, Montreal, QC, H1X 2B2, Canada

Keywords:
Leguminosae
Caesalpinia
Succulent Biome
Seasonally Dry Tropical Forest
Systematics
biogeography.

Presentation Type: Oral Paper:Papers for Sections
Session: 11
Location: Magnolia/Riverside Hilton
Date: Monday, July 29th, 2013
Time: 2:00 PM
Number: 11003
Abstract ID:521
Candidate for Awards:None