Moody, Michael .
Deep divergence within a rare species complex (Myriophyllum petraeum) of geographically disjunct granite "islands" in the arid landscape of the Biodiversity Hotspot of southwest Australia.
The international biodiversity hotspot of southwest Australia has an ancient landscape, above sea level and devoid of glaciations for over 200 million years. The region has also lacked major geological events such as volcanism and mountain uplifting. This has led to distinctive patterns of evolution at the landscape scale with a very high rate of local endemism and rarity with often geographically disjunct species distribution patterns. While the region has seen major advances over the past decade in taxonomic discovery and description, an estimated relatively high proportion of the flora is yet to be formally described (>15% of the WA flora) and species level phylogeographic studies are still rare. Myriophyllum petraeum is a species of conservation concern in southwest WA with its 20 known population distributed over a 300 km2 region overlapping five recognized bio-regions. Populations are found in small ephemeral pools (< 10 m2) on granite outcrops scattered across the region well known for their particularly unique floras, acting as islands in an often arid landscape. The level of geographic isolation of M. petraeum populations would predict a potential for low gene flow at an ancient time scale, as onset of aridity dates > 4 m.a. Species level DNA sequence markers (nrDNA ITSand cpDNA trnL-rpl32) were utilized to determine level of divergence among populations within this complex. Deep divergence was found at a geographic scale among population with 9 unique ITS genotypes and 10 unique cpDNA haplotypes recognized from 12 sampled populations. The level of sequence diversity among populations is comparable to that found among many well defined morphological species pairs in the genus. Nodal divergence among populations is estimated as high as 1.8 m.a., near the beginning of the Pleistocene.
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1 - University of Western Australia, Plant Biology, 35 Stirling Highway, Crawley, WA, 6009, Australia
Presentation Type: Oral Paper:Papers for Topics
Location: Waterman Room/Chase Park Plaza
Date: Wednesday, July 13th, 2011
Time: 11:00 AM