Abstract Detail

Systematics Section/ASPT

Jacobs, Sarah [1], Kristofferson, Casey [1], Uribe-Convers, Simon [1], Tank, David [1].

Evaluating the Taxonomic Status of Two Narrowly Endemic Owl's Clovers (Castilleja: Orobanchaceae).

Species delimitation can be challenging in recently and rapidly radiating groups. The accumulation of species properties – molecular, morphological, ecological, and geographic traits – happens in a gradual and continuous manner. Because species boundaries may be inconsistent or incomplete with respect to these traits, a multifaceted approach to assessing species delimitation is necessary. The genus Castilleja L. (Orobanchaceae) experiences its greatest species diversity in the North American West. One species, Castilleja ambigua, is widespread along the western coast, with several described varieties united by both ecological and morphological similarities. One variety, C. ambigua var. meadii, shares morphological similarities with C. ambigua but is isolated geographically, occurring in a few small populations in Napa County, California, whereas the other three varieties have primarily coastal distributions. In addition, Castilleja victoriae was recently described from the San Juan Islands of Washington and adjacent British Columbia, and has been allied with C. ambigua because of its similar, but arguably unique, morphological and ecological traits. Here, we assess the taxonomic status of C. ambigua var. meadii and C. victoriae using molecular phylogenetic methods to test hypotheses of species boundaries in this clade. We sequenced five chloroplast DNA and two nuclear ribosomal DNA regions for phylogeny reconstruction, using both maximum likelihood and Bayesian methods, and modeled alternative species delimitations of C. ambigua and C. victoriae calculating speciation probabilities using BP& P – a coalescent-based, Bayesian approach to species delimitation. ML and Bayesian analyses revealed that C. victoriae is more closely related to the rest of the C. ambigua clade than C. ambigua var. meadii. Speciation probabilities separating C. ambigua var. meadii from the rest of the clade were 0.97, while there was no statistical support for a speciation event leading to C. victoriae despite clear morphological and ecological differences. From these analyses, we conclude that C. ambigua var. meadii diverged from the core C. ambigua lineage earlier than C. victoriae and should be elevated to species status as C. meadii. Its current distribution and abundance are extremely limited and as a species, rather than variety of C. ambigua, this taxon will likely receive more recognition from a conservation standpoint. Finally, we emphasize that phenotypic differences alone are not necessarily the best indicators of evolutionary divergence; both taxa considered here were described based on their divergent morphologies. We illustrate the importance of multiple lines of evidence, including phylogenetic approaches, for species delimitation – especially in recently evolved lineages.

Broader Impacts:

1 - University of Idaho, College of Natural Resources & Institute for Bioinformatics and Evolutionary Studies, 875 Perimeter Drive MS 1133, Moscow, ID, 83844-1133

Keywords:
Castilleja
Orobanchaceae
species delimitation
Likelihood
Bayesian
speciation.

Presentation Type: Oral Paper:Papers for Sections
Session: 13
Location: Rosedown/Riverside Hilton
Date: Monday, July 29th, 2013
Time: 2:45 PM
Number: 13006
Abstract ID:751
Candidate for Awards:George R. Cooley Award