Evidence for convergent evolution among phylogenetically distant rare species of Tetratheca (Elaeocarpaceae, formerly Tremandraceae) from Western Australia
Ryonen Butcher A B E , Margaret Byrne C and Darren M. Crayn DA Western Australian Herbarium, Department of Environment and Conservation, Locked Bag 104, Bentley Delivery Centre, WA 6983, Australia.
B School of Plant Biology (Botany MO90), The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.
C Science Division, Department of Environment and Conservation, Locked Bag 104, Bentley Delivery Centre, WA 6983, Australia.
D National Herbarium of New South Wales, Botanic Gardens Trust, Mrs Macquaries Road, Sydney, NSW 2000, Australia.
E Corresponding author. Email: Ryonen.Butcher@dec.wa.gov.au
Australian Systematic Botany 20(2) 126-138 https://doi.org/10.1071/SB06017
Submitted: 1 June 2006 Accepted: 22 January 2007 Published: 26 April 2007
Abstract
Morphological and molecular investigations of taxon relationships among rare species of Tetratheca Sm. occurring near Koolyanobbing, Western Australia, have confirmed the distinctness of T. aphylla F.Muell., T. harperi F.Muell. and T. paynterae Alford and identified three new rare taxa from collections affiliated with T. aphylla and T. paynterae. The recognition of these taxa at specific and sub-specific ranks is based on their different degrees of morphological and molecular divergence, combined with geographic disjunction. Cladistic analysis of nrDNA internal transcribed spacer and cpDNA trnL-trnF sequences from a range of Tetratheca species from Western Australia and the eastern states indicates that T. aphylla, T. harperi and T. paynterae belong to three separate evolutionary lineages and that the endemism displayed among these taxa to small, disjunct ranges within the same geographic area, is a result of in situ speciation due to historical fragmentation. These results exemplify the extremely high conservation value of the Yilgarn banded ironstone ranges. The superficial similarity among the study taxa in having a ‘leafless’ habit can be seen to be adaptive convergence in response to the marginal and semi-arid environments in which they occur, and this character is highly homoplastic within the genus.
Acknowledgements
RB thanks Jerome Bull for his enthusiasm in the field, Matthew Williams for his assistance with morphometric analyses, Jenny Chappill (dec.), Marco Duretto, Neil Gibson, Terry Macfarlane and Juliet Wege for taxonomic discussions, Bronwyn Macdonald and Paul Rymer for laboratory assistance, Siegy Krauss for preliminary genetic results, Erica Alecs, Daniel Sievers and Bob Dixon for field assistance and Dot and Ron Budge, and Joy and Herb (dec.) Budge for their hospitality during field work. The Department of Clinical Immunology at Royal Perth Hospital and the DNA Analysis Facility at University of New South Wales performed the sequence electrophoresis. Funding from Portman Iron Ore Pty Ltd (to MB), the Australian Biological Resources Study (to DMC) and the Hermon Slade Foundation (to DMC) is acknowledged. Piers Goodman (Portman Iron Ore Pty Ltd) is thanked for the provision of the Koolyanobbing region Tetratheca distribution map and for facilitating financial support for the publication of colour images.
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[Verified 30 January 2007]
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