Abstract Detail

Systematics Section/ASPT

ZIMMERS, JAY [1], MANCUSO, MICHAEL [2], SMITH, JAMES F. [3].

Determining the Taxonomic Status of the four varieties of Astragalus cusickii Using Molecular Phylogenetic Methods.

The concept of species is central to biology, yet a precise definition of species can be elusive, particularly when delimiting the boundary between two closely related taxa. Definitions of species such as the biological species concept can be useful when applied to certain organisms, but may present problems elsewhere in the tree of life. The phylogenetic species concept defines species as the smallest group of organisms that share a common ancestor and which can be distinguished from other such groups. In this study, we have applied the phylogenetic species concept to explore the taxonomic organization of Astragalus cusickii, which is currently recognized as comprising four varieties within a single species, as determined by morphological characters. Varieties packardiae and sterilis are rare plants endemic to a small area in southwestern Idaho and adjacent Oregon. Conservation concerns have made it necessary to reexamine the taxonomic status of Astragalus cusickii using molecular phylogenetic methods. In this study, we obtained gene sequences (the chloroplast trnS-trnG, nuclear ribosomal ITS and the low copy nuclear gene CNGC4) from numerous specimens of each variety of Astragalus cusickii as well as several other species that are hypothesized to be close to A. cusickii based on morphology. These sequences were analyzed using maximum parsimony, maximum likelihood, and Bayesian inference to develop a probable phylogeny. Preliminary results show monophyly within varieties packardiae and sterilis and a monophyletic cusickii/flexilipes, although flexilipes is paraphyletic. The monolphyly of A. cusickii in its entirety is as yet unsupported and the three clades within A. cusickii are unresolved with two individuals of A. whitneyi. A chloroplast capture event occurred recently within one population of packardiae implying that hybridization has occurred at least among some individuals at some point in the past.

1 - Boise State University, Biological Sciences, 1910 University Dr. MS1515, Boise, ID, 83725-1515, USA
2 - 20 N. Wilson St., Boise, ID, 83706, USA
3 - BOISE STATE UNIVERSITY, Biology Department, 1910 UNIVERSITY DRIVE, MS1515, Boise, ID, 83725-1515, USA

Keywords:
Astragalus
Fabaceae
species delimitation
molecular systematics.

Presentation Type: Oral Paper:Papers for Sections
Session: 18
Location: Salmon/Boise Centre
Date: Tuesday, July 29th, 2014
Time: 8:30 AM
Number: 18003
Abstract ID:158
Candidate for Awards:None