Genetic variation within and between populations of Posidonia australis, a hydrophilous, clonal seagrass

Abstract

Allozyme diversity was surveyed at 15 loci across 22 populations of the hydrophilous seagrass Posidonia australis (Hook. f.). Substantial genetic variation was detected (HT = 0.311) with a high proportion of this variation partitioned between populations (GST = 0.623). The high value of GST is attributed to large geographical distances between many of the populations and several of the extreme north-western populations having fixed homozygous genotypes. Southwestern populations of P australis were the most variable and these correlate with the highest species diversity in this genus. Intermediate levels of genetic diversity are observed in P australis when compared with other hydrophilous angiosperms. Average gene diversity values for hydrophilous taxa surveyed to date indicate lower HT and higher GST values than an average reported for 468 plant taxa. Patterns of genetic variability in different regions of the distribution of P australis may reflect past evolutionary diversification into novel environments and subsequent dispersal following the rifting of Australia from Antarctica in the early Tertiary.

Characterisation of polymorphic microsatellite markers in the widespread Australian seagrass, Posidonia australis Hook. f. (Posidoniaceae), with cross-amplification in the sympatric P. sinuosa

“…Locus PaB6 and PaB8 did not amplify (consistently) well in samples from Port Stephens, and less stringent PCR conditions were required. These results suggest deeply divergent eastern and western lineages within P. australis, consistent with earlier allozyme results (Waycott et al 1997). Seven of the 10 loci amplified in P. sinuosa samples, six of which were polymorphic (Table 2).…”

“…f. is widespread along the Australian coastline, occurring from Shark Bay in northern Western Australia around the southern coast to Lake Macquarie in central New South Wales, and along the northern coast of Tasmania (Gobert et al 2006). Population differentiation at a broad geographic scale has been reported in P. australis, but these results were based on a low number of weakly polymorphic markers e.g., five polymorphic allozyme loci (Waycott et al 1997) and 28 Pa118/9R…”

Correlation analysis of genetic diversity and population structure of Houttuynia cordata Thunb with regard to environment

“…In addition, all genetic parameters were not significantly correlated with soil pH and longitude (Table 8). (Waycott et al, 1997). Many studies have shown that the average ratio of different genotypes (PD) and Simpson diversity index (D) of asexually reproduced plants are 0.62 (0.1-1.00) and 0.75 (0.13-1.00), respectively (Widén et al, 1994).…”

Linking Seed Photosynthesis and Evolution of the Australian and Mediterranean Seagrass Genus Posidonia

“…However, other studies of phylogeny based on a nuclear marker (rRNA-ITS) revealed a more ancient split between the Mediterranean and Australian taxa (>60 Myr BP). Based on this evidence, the Australian Posidonia species are probably the survival descendants after the separation of Australia from Antarctica during the Eocene (55.8 to 33.9 Myr BP) [7, 16], followed by a more recent divergence of the two recognized Australian complexes around 12 Myr ago [1]. In the northern hemisphere only P .…”