Systematics Section / ASPT
Teoh, View , Brewer, J. Stephen , Starr, Julian R. .
Phylogeny, hybridization and the evolution of fire-adaptive traits within the grass-leaved goldenasters (Pityopsis, Asteraceae).
Pityopsis is a perennial herbaceous genus native to the southeastern United States and northern Central America. To examine evolution within the genus, we reconstructed the phylogeny of all seven species and five of the seven varieties of Pityopsis using the nuclear rDNA markers ITS and ETS. Phylogenetic analyses recovered two well-supported biogeographic clades: (1) a “Florida” clade (70 % bootstrap or BS; P. aspera, P. oligantha, P. flexuosa, P. graminifolia vars. graminifolia and aequifolia) composed primarily of species adapted to different moisture regimes within Florida or the outer Coastal Plain (OCP) except for Pityopsis aspera var. adenolepis (Florida, Fall-Line Hills and Piedmont), and (2) an “Out-of-Florida” clade (73% BS) consisting of three disjunct species (P. falcata, P. pinifolia, P. ruthii) adapted to xeric or rocky environments that are sympatric or parapatric with the widespread polyploid P. graminifolia var. latifolia (2n = 36). These results do not support the division of the genus into sections Pityopsis and Graminifoliae, and they contradict our previous morphological analysis suggesting a weakly supported “Falcata” clade (57% BS; P. pinifolia, P. falcata, P. flexuosa, P. ruthii, P. graminifolia [monophyletic]) sister to a strongly supported (90% BS) “Aspera” clade (P. aspera, P. adenolepis, P. oligantha). We hypothesize that differences amongst molecular and morphological analyses are due to high levels of homoplasy in morphological characters and to hybridization between the Florida and Out-of-Florida clades that resulted in the polyploid evolution of Pityopsis graminifolia var. latifolia. Character analyses suggest that the absence of fire-stimulated flowering is ancestral in Pityopsis. Fire-stimulated flowering subsequently arose early in the Florida clade in productive fire-prone savannas, but was then lost upon adaptation to xeric scrub habitats. Efforts to produce a maternal phylogeny (cpDNA) to more fully understand hybridization within Pityopsis are currently underway.
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S. Brewer Homepage
View-hune Teoh Hompage
1 - University of Mississippi, Department of Biology, 214 Shoemaker Hall, University, Mississippi, 38677, USA
2 - University of Mississippi, Department of Biology, 214 Shoemaker Hall, University, MS, 38677, USA
3 - University of Ottawa, Department of Biology, Gendron Hall, Room 160, 30 Marie Curie, P.O. Box 450, Station A,, Ottawa, Ontario, K1N 6N5, Canada
Presentation Type: Oral Paper:Papers for Sections
Location: Lake Erie/Hilton
Date: Monday, July 9th, 2007
Time: 3:30 PM