Abstract Detail

Systematics Section/ASPT

Lyon, Stephanie [1], Clements, Mark [2], Givnish , Thomas J [3].

Phylogeny, morphological evolution, and biogeography of the orchid subtribe Acianthinae.

We present the most comprehensive phylogeny of the Acianthinae (Orchidaceae: Orchidoideae: Diurideae) to date, including all major lineages and over 80 taxa of Corybas, the largest genus in the group. With excellent backbone resolution and support, we propose a revised generic classification scheme that minimizes taxonomic changes but accounts for the polyphyly of the genus Acianthus. Corybas is strongly supported as monophyletic, and several of the genera that have been proposed as segregates are clearly not natural groups. We examine several morphological characters that have been used to subdivide Corybas, and conclude that while some floral characters, such as the presence of spurs and some minor details of the lateral tepals, are highly conserved, other characters such as tepal length are more labile. Some remarkable cases of convergence in floral form are reported. Historical biogeographic reconstructions of the Acianthinae support an origin in Australia about 27 My. Much exchange between Australia and New Zealand and Australia and New Caledonia is apparent, primarily following the patterns expected from West Wind Drift, but only following the reemergence of these Zealandian fragments post drowning. Our reconstructions of the two genera (Corybas and Stigmatodactylus) that have dispersed beyond these southern landmasses support a fairly restrictive path of dispersal along the intervening islands to mainland Asia, via island hopping. Dispersal northwards likely began between 10-12 My, congruent with the timing of major collision between the Australian and Asian plates. Corybas seems to have dispersed directly from Australia to the Sunda shelf, likely at a time when New Guinea was primarily submerged, and only colonized New Guinea around 8 My coinciding with the onset of major uplift and mountain building. Despite the finding that many lineages are highly geographically conserved, and most dispersal seems to take place between adjacent landmasses, a few instances of fairly remarkable long-distance dispersal are inferred.

1 - University of Wisconin - Madison, Botany, 430 Lincoln Dr, Madison, WI, 54706, USA
2 - CSIRO Plant Industry, Centre for Australian National Biodiversity Research, Clunies Ross Street, Black Mountain, ACT, 2601, Australia
3 - University of Wisconsin-Madison, Botany, 430 Lincoln Dr, Madison, WI, 53706, USA

Keywords:
Orchidaceae
Australasia
Malesia
long-distance dispersal
Corybas
Acianthus.

Presentation Type: Oral Paper:Papers for Sections
Session: 31
Location: Pines South/Boise Centre
Date: Tuesday, July 29th, 2014
Time: 4:45 PM
Number: 31012
Abstract ID:760
Candidate for Awards:None