Abstract Detail

Systematics Section/ASPT

Teisher, Jordan [1], Kellogg, Elizabeth [2].

Multivariate Analysis of the Arundinoideae and Micrairoideae (Poaceae).

Many groups of organisms do not lend themselves to molecular analysis due to rarity and/or habitat inaccessibility. Furthermore, herbarium collections often fail to yield viable DNA, making these specimens analogous to very excellently preserved fossils. Morphology is thus a large part of the data available for these taxa, but unfortunately some plant groups are notorious for their lack of phylogenetic signal in morphological characters. We cannot simply ignore these taxa, however, as the inconvenient geographic distributions and peculiar characteristics that make some species untenable as model genetic organisms may be important exceptions to established evolutionary rules and trends. In this study, we use a multivariate comparative approach to explore the evolutionary patterns in two very poorly-known subfamilies of the grass family (Poaceae): the Arundinoideae and the Micrairoideae. These taxa contain approximately 225 species, most of which are the Micrairoideae. The Arundinoideae was historically a “junk group” for odd taxa that did not fit elsewhere in classifications of the grasses. Molecular analyses have reduced the group in composition, leaving it with a highly morphologically disparate and geographically dispersed collection of species-poor genera. The Micrairoideae, in addition to possessing many more species in fewer genera, has a more continuous geographic distribution. Both subfamilies and their sister relationship are supported by chloroplast molecular data, although less than half of the genera and only a handful of species have been sequenced. We compare patterns of morphological, geographical and ecological variation within and between these subfamilies to explore 1) whether there are cohesive taxonomic groups elucidated by these data and 2) what factors might be responsible for the different patterns of taxonomic diversity and morphological disparity in the two clades. Phylogenetic analysis of morphological and ecological data sets recovers genera within subfamilies, a group of temperate genera in the Arundinoideae and the widely distributed tribe Isachneae in the Micrairoideae as monophyletic. Aside from these groupings, however, phylogenetic signal is virtually absent from any of the data as expected based on previous studies. Multivariate analyses of dispersion find that the Arundinoideae are more dispersed in terms of morphology, ecology and geography than the Micrairoideae, consistent with the taxonomic structure of the current classification. These results also suggest either an early diversification within the Arundinoideae followed by decline of intermediate taxa or a history of long-distance dispersal with adaptive divergence. The data are discussed in the context of what is currently known about phylogeny in these subfamilies.

Broader Impacts:

1 - Washington University in St. Louis, Evolution, Ecology and Population Biology, One Brookings Dr, St. Louis, MO, 63130, United States
2 - University of Missouri - St. Louis, Department of Biology, One University Boulevard, St. Louis, MO, 63121-4499, USA, 314/516-6217

Keywords:
multivariate morphometrics
Poaceae
Systematics.

Presentation Type: Oral Paper:Papers for Sections
Session: 11
Location: Magnolia/Riverside Hilton
Date: Monday, July 29th, 2013
Time: 2:15 PM
Number: 11004
Abstract ID:623
Candidate for Awards:George R. Cooley Award