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Phylogeographical patterns of trees in topographically subdued, unglaciated landscapes are under-reported, and might reflect population persistence and the influences of environment and distance over historical (~2.6 Mya to present) and contemporary (recent generations) timescales. We examined this hypothesis using genetic analyses of four slowly evolving non-coding chloroplast sequences and 16 nuclear microsatellites in the tree Corymbia calophylla from south-western Australia, an area that has been unglaciated since the Permian (c. 300–250 Mya). We found strong population differentiation for chloroplast DNA and low differentiation for nuclear loci, consistent with higher gene flow by pollen than by seed. We identified three divergent chloroplast lineages distributed in central, northern and southern regions, and diversifying from the early (c. 3.028 Mya), mid- (c. 0.793 Mya) and late (c. 0.426 Mya) Pleistocene, respectively. Moderate to high nucleotide diversity with population-specific haplotypes supported long-term persistence, but diversification of lineages provided evidence of unexpected episodic range expansion. We suggest this pattern reflects environmental influences of climatic oscillations during progressive drying of southwestern Australia from the early Pleistocene. Significant tests for isolation by environment for nuclear loci also supported an influence of contemporary environmental (aridity) conditions on genetic structure, but isolation by distance (IBD) was greater. Significant chloroplast and nuclear IBD suggested distance was a major influence on gene flow at both timescales. [ABSTRACT FROM AUTHOR]

Most woody plants are animal-pollinated, but the global problem of habitat fragmentation is changing the pollination dynamics. Consequently, the genetic diversity and fitness of the progeny of animal-pollinated woody plants sired in fragmented landscapes tend to decline due to shifts in plant-mating patterns (for example, reduced outcrossing rate, pollen diversity). However, the magnitude of this mating-pattern shift should theoretically be a function of pollinator mobility. We first test this hypothesis by exploring the mating patterns of three ecologically divergent eucalypts sampled across a habitat fragmentation gradient in southern Australia. We demonstrate increased selfing and decreased pollen diversity with increased fragmentation for two small-insect-pollinated eucalypts, but no such relationship for the mobile-bird-pollinated eucalypt. In a meta-analysis, we then show that fragmentation generally does increase selfing rates and decrease pollen diversity, and that more mobile pollinators tended to dampen these mating-pattern shifts. Together, our findings support the premise that variation in pollinator form contributes to the diversity of mating-pattern responses to habitat fragmentation. [ABSTRACT FROM AUTHOR]

India is the largest grower of Eucalyptus with an area of 3.943 million hectares under plantations and E. tereticornis is the predominant species in the plains of southern India with an average productivity of 12–25 m3 ha−1 year−1. With the aim to establish seedling seed orchards of the species, seed lots of fifteen provenances were imported from Australia and a trial was laid. In the present study the genetic diversity existing in the seed orchard was estimated using ISSR–PCR. Seven ISSR primers amplified 663 amplicons in the size ranging from 255 to 2,711 bp. The total number of polymorphic bands varied from 59 to 123 with 100% polymorphic banding profiles. The average gene diversity ( Hj) of all the provenances ranged from 0.0589 to 0.1109 and the total gene diversity estimated was low ( HT = 0.130) when compared to the earlier reports from other eucalypts species. Analysis of Molecular Variance partitioned the ISSR variation into inter and intra population components. The inter population component accounted for 55.2% of the variation and the intra population component accounted for 46.3% ( P < 0.001). A neighbour-joining analysis was done using the dissimilarity matrix to determine the aggregation of the individuals into clusters. Existence of population structure among the populations was revealed in STRUCTURE analysis but geographical region based clustering was not observed. The assessment of intra and inter genetic variation documented in the present study suggests that, along with the phenotypic traits, knowledge about genetic diversity measured at the DNA level in individuals of seed orchards provide an objective guide for selective culling of trees for maintaining optimal diversity for enhanced genetic gains. [ABSTRACT FROM AUTHOR]

The potential for breeding Pinus radiata D. Don to improve wood stiffness (modulus of elasticity, MoE) was examined by obtaining pith-to-bark cores from trees at breast height in two independent genetic trials. The effectiveness of early selection for stiffness and indirect selection on the component traits, microfibril angle (MfA) and wood density, was determined as well as the age-related changes in the genetic variation of these traits. The first trial comprised 50 open-pollinated families in the central North Island, New Zealand. The second trial comprised 20 control-pollinated families in New South Wales, Australia. The genetic control of MfA, density, and MoE was found to be high in the corewood and moderate in the outerwood. Estimated genetic correlations suggested that early selection for most traits would be successful but could be carried out slightly earlier at the New Zealand site than at the Australian site. To maximize gain in the corewood, selection for MoE and MfA would be most effective around rings 4-8. There were no adverse correlations between MoE and MfA or density, implying that selection for MoE would also improve MfA and density. [ABSTRACT FROM AUTHOR]

It is difficult to accurately identify Mycosphaerella species associated with leaf diseases of Eucalyptus based on morphological characters, as there is considerable overlap between very similar species and subspecies, and isolation from the host is not easy. Thus, a PCR and RFLP assay based on the ITS region of nr DNA was developed for the rapid detection and differentiation of M. nubilosa, M. cryptica and two non-sporing unidentified Mycosphaerella species isolated from the foliage of trees in resistant and susceptible families of E. globulus in a seed orchard at Kinglake West, Victoria, Australia. The M. nubilosa primer pair MNF/MNR was highly specific. A PCR-RFLP system based on the primer pair MCF/MCR, coupled with two restriction enzymes (DdeI and Tru1I), differentiated M. cryptica, M. nubilosa, M. tasmaniensis and M. aff. vespa. One of the unidentified field-isolated Mycosphaerella species was identified as M. grandis on the basis of ITS sequence data while the other species remains unidentified. A PCR-RFLP system based on the primer pair U1F/U1R, coupled with the restriction enzyme StyI, differentiated between the two unidentified species. Unexpectedly, unlike isolation and culture studies, these assays detected M. nubilosa, M. cryptica and M. grandis in all single lesions examined on both juvenile and adult leaves, and on both highly resistant and highly susceptible E. globulus trees at this site. [ABSTRACT FROM AUTHOR]