Population and phylogenetic analysis of the cinnamoyl coA reductase gene in Eucalyptus globulus (Myrtaceae)

Abstract

Low-copy number nuclear genes are currently emerging as new markers for phylogenetic and phylogeographic analysis. This study used the single-copy gene for cinnamoyl coA reductase (CCR) to gain insights into the evolutionary history of the forest tree Eucalyptus globulus Labill. (subgenus Symphyomyrtus, section Maidenaria). A population analysis based on CCR restriction fragments from E. globulus was combined with a phylogenetic analysis of 1.5 kb of CCR sequence from the major haplotypes. Two highly divergent CCR lineages were found in E. globulus. One lineage was prominent throughout the species’ range and was identified in 16 other Maidenaria species by restriction analysis. The second lineage, which was prominent in the northern part of the species’ range, was found only in species of the E. globulus complex and surprisingly showed homology to CCR from Eucalyptus saligna Smith (subgenus Symphyomyrtus, section Latoangulatae). This finding may reflect either incomplete lineage sorting in CCR, or reticulate evolution. No statistically significant phylogeographic structure (geographic clustering of closely related haplotypes) was detected. However, patterns of CCR haplotypic diversity were congruent with patterns of chloroplast DNA diversity in several respects, and divided the range of E. globulus into four regions, supporting (1) former gene flow between King Island and western Tasmania, (2) gene flow between northern Tasmania, the Furneaux Group and Victoria, and (3) a genetic disjunction between north-eastern and south-eastern Tasmania, consistent with separate histories for these two regions.

Chemical Variation in a Dominant Tree Species: Population Divergence, Selection and Genetic Stability across Environments

“…Our clinal trends in chemistry are consistent with that reported across the island group by Wallis et al [22] which appears to coincide with a barrier to seed dispersal suggested by the north-eastern Tasmanian populations lacking a specific chloroplast haplotype which is common in eastern Victoria and present on Flinders Island and the Southern Furneaux [67]. However, while there may be a barrier to seed dispersal, there is evidence of pollen flow [68] supporting the steep cline evident in this study.…”

Response of a southern temperate marsupial, the Tasmanian pademelon (Thylogale billardierii), to historical and contemporary forest fragmentation

“…Studies of Eucalyptus globulus in this region have inferred a barrier to seed dispersal (Freeman et al. 2001), but not nuclear gene flow (McKinnon et al. 2005), which also suggests the intermittent formation of a forested landbridge.…”

Progress in Myrtaceae genetics and genomics: Eucalyptus as the pivotal genus

“…However, this is the level at which molecular phylogenetics and population genetics (see Section "Molecular population genetics") intersect, with continuous variation often occurring between closely related taxa. Population genetic approaches are increasingly being used to resolve the phylogenetic affinities and differentiation of species, particularly at the intra-series levels (e.g., Byrne 2008;Cook et al 2008;Drummond et al 2000;McKinnon et al 2005;McKinnon et al 2008;Ochieng et al 2007a;Percy et al 2008). In eucalypts, the frequent occurrence of geographic replacement series involving closely related taxa argues for recent speciation through allopatric processes Byrne 2008;Ladiges 1997).…”