Contrasting levels of connectivity and localised persistence characterise the latitudinal distribution of a wind-dispersed rainforest canopy tree

Abstract

Contrasting signals of genetic divergence due to historic and contemporary gene flow were inferred for Coachwood, Ceratopetalum apetalum (Cunoniaceae), a wind-dispersed canopy tree endemic to eastern Australian warm temperate rainforest. Analysis of nine nuclear microsatellites across 22 localities revealed two clusters between northern and southern regions and with vicariance centred on the wide Hunter River Valley. Within populations diversity was high indicating a relatively high level of pollen dispersal among populations. Genetic variation was correlated to differences in regional biogeography and ecology corresponding to IBRA regions, primary factors being soil type and rainfall. Eleven haplotypes were identified by chloroplast microsatellite analysis from the same 22 localities. A lack of chloroplast diversity within sites demonstrates limited gene flow via seed dispersal. Network representation indicated regional sharing of haplotypes indicative of multiple Pleistocene refugia as well as deep divergences between regional elements of present populations. Chloroplast differentiation between sites in the upper and lower sections of the northern population is reflective of historic vicariance at the Clarence River Corridor. There was no simple vicariance explanation for the distribution of the divergent southern chlorotype, but its distribution may be explained by the effects of drift from a larger initial gene pool. Both the Hunter and Clarence River Valleys represent significant dry breaks within the species range, consistent with this species being rainfall dependent rather than cold-adapted.

An ancient and a recent colonization of islands by an Australian sap‐feeding insect

“…More recently, the speciation and biogeographical limits of various taxa including assassin spiders, mayflies, and snails (Christidis & Dean, 2008;Rix & Harvey, 2012) have been found to correspond with the Hunter Valley breaks. Similarly, these patterns have also been observed at the population level within species of skinks (Chapple, Hoskin, Chapple, & Thompson, 2011b), butterflies (Eastwood, Pierce, Kitching, & Hughes, 2006), and trees (Heslewood, Lowe, Crayn, & Rossetto, 2014). Our sampling between Sydney and the Hunter Val-…”

Analysis of nuclear microsatellites reveals limited differentiation between Colchic and Hyrcanian populations of the wind‐pollinated relict tree Zelkova carpinifolia (Ulmaceae)

“…However, our findings indicate the possibility for pollen dispersal over larger distances (200 km or more). So far, no other cases of such long‐distance pollen dispersal were described in the literature (Petit and Hampe, 2006; Heslewood et al, 2014). However, we do not exclude that more stepping‐stone populations of Zelkova carpinifolia , which connected the regions in the past have already been eliminated due to climate change or anthropogenic influence, and so our results can also illuminate the past gene flow in a long‐lived tree.…”

Lines in the land: a review of evidence for eastern Australia's major biogeographical barriers to closed forest taxa

“…6; Mellick, Lowe & Rossetto, 2011;Mellick et al, 2012). The CRC appears to have been important in the diversification of several closed forest geckos (Couper et al, 2008;Colgan, O'Meally & Sadlier, 2009), fish (Rourke & Gilligan, 2010), plants (Mellick et al, 2011(Mellick et al, , 2012Heslewood et al, 2014;Van Der Merwe et al, 2014), and mammals (Frankham, Handasyde & Eldridge, 2012;Rowe et al, 2012). Likewise, some taxa appear to be restricted by the intersection of open woodland around the Glasshouse Mountains region north of Brisbane (Crisp, Linder & Weston, 1995).…”