Understanding the environmental parameters that drive adaptation among populations is important in predicting how species may respond to global climatic changes and how gene pools might be managed to conserve adaptive genetic diversity. Here, we used Bayesian FST outlier tests and allele-climate association analyses to reveal two Eucalyptus EST-SSR loci as strong candidates for diversifying selection in natural populations of a southwestern Australian forest tree, Eucalyptus gomphocephala (Myrtaceae). The Eucalyptus homolog of a CONSTANS-like gene was an FST outlier, and allelic variation showed significant latitudinal clinal associations with annual and winter solar radiation, potential evaporation, summer precipitation and aridity. A second FST outlier locus, homologous to quinone oxidoreductase, was significantly associated with measures of temperature range, high summer temperature and summer solar radiation, with important implications for predicting the effect of temperature on natural populations in the context of climate change. We complemented these data with investigations into neutral population genetic structure and diversity throughout the species range. This study provides an investigation into selection signatures at gene-homologous EST-SSRs in natural Eucalyptus populations, and contributes to our understanding of the relationship between climate and adaptive genetic variation, informing the conservation of both putatively neutral and adaptive components of genetic diversity.

Patterns of mating and dispersal are key factors affecting the dynamics, viability and evolution of plant populations. Changes in mating system parameters can provide evidence of anthropogenic impacts on populations of rare plants. Tetratheca paynterae subsp. paynterae is a critically endangered perennial shrub confined to a single ironstone range in Western Australia. Mining of the range removed 25% of plants in 2004 and further plants may be removed if the viability of the remaining populations is not compromised. To provide baseline genetic data for monitoring mining impacts, we characterised the mating system and pollen dispersal over two seasons in T. paynterae subsp. paynterae and compared mating system parameters with two other ironstone endemics, T. paynterae subsp. cremnobata and T. aphylla subsp. aphylla that were not impacted by mining. T. paynterae subsp. paynterae was the only taxon showing evidence of inbreeding (t m = 0.89), although hand pollination revealed pre-zygotic self-incompatibility limits the production of seed from self-pollen. In a year of lower fruit set (2005), the estimate of correlated paternity increased from 20 to 35%. Direct estimates of realised pollen dispersal, made by paternity assignment in two small populations where all adult plants were genotyped, revealed a leptokurtic distribution with 30% of pollen dispersed less than 3 m and 90% less than 15 m. Restricted pollen dispersal maintains the strong genetic structuring of the adult populations in succeeding generations. As a consequence of preferential outcrossing, any reduction in effective population size, flowering plant density and/or the abundance and activity of pollinators may impact negatively on population viability through reduced seed set, increased inbreeding and increased correlated paternity.

The chloroplast and nuclear data suggest wide persistence of E. gomphocephala during the LGM. Palaeodistribution modelling supports the conclusions drawn from genetic data and indicates a widespread westward shift of E. gomphocephala onto the exposed continental shelf during the LGM. This study highlights the importance of the inclusion of complementary, non-genetic data (information on geomorphology and palaeoclimate) to interpret phylogeographic patterns.

Aim Terrestrial plant ecology and evolution is significantly influenced by the phenomenon of fire, but studies of its potential impact on intraspecific genetic variation and phylogeography are rare. This understanding will be important for predicting the biogeographical consequences of changing fire regimes under global climate change. Here, we asked whether changing historical fire regimes, together with climatic and geological history, have influenced phylogeographical patterns in a fire-ephemeral vine. We also asked whether demographic stochasticity associated with a fire-ephemeral life history results in nuclear genetic drift as expected from spatio-temporal patchiness, or if this effect is buffered by the connectivity and diversity afforded by a persistent soil seed bank.Location The fire-prone, mediterranean-type climate region of south-western Australia.Methods We used Bayesian phylogeny reconstruction and statistical tests of demographic expansion based on variation at three non-coding chloroplast sequence regions (atpF, ndhF-rpl32, psbD-trnT) to reconstruct phylogeographical history. Nuclear diversity and population structure at 11 microsatellite loci were investigated for evidence of genetic drift.Results Evidence for prolonged persistence and a lack of vicariance within the species range was found, together with strong evidence of historical demographic expansion. Contrary to expectations, there was little evidence of nuclear genetic drift despite strong, above-ground spatio-temporal population patchiness.Main conclusions Our findings suggest that a late Pleistocene increase in fire frequency may have led to demographic expansion in this fire-ephemeral species; alternatively, the expansion signal may be an inherent feature of fire ephemerals with a persistent soil seed bank. Prolonged climatic stability has likely fostered persistence within the species range in contrast to contraction and vicariance. The notable lack of genetic drift implies a role for ample pollen dispersal and a long-lived soil seed bank in the maintenance of diversity and connectivity in an otherwise stochastic, fire-driven system.

Variation in patterns of mating within and among plant populations can be impacted by habitat disturbance and have significant implications for offspring fitness. An understanding of this variation will inform predictions of seed genetic quality, benefiting ecological restoration through better seed-sourcing guidelines. We assessed mating system variation in six populations of tuart (Eucalyptus gomphocephala DC.), an iconic tree of significance to ecological restoration in Western Australia. A mixed mating system was observed with predominant outcrossing (tm = 0.76 ± 0.05) and low biparental inbreeding (tm–ts = 0.03 ± 0.02). We detected some evidence of increased inbreeding in a naturally fragmented population (tm–ts = 0.10 ± 0.04) and in a disturbed urban remnant (tm = 0.52 ± 0.12), including a family with complete selfing. However, most variation in outcrossing rate occurred among individuals within populations (82%), rather than among populations (2.6%) or among groups of populations defined by fragmentation or disturbance (15.4%). Genetic diversity was not consistently lower in offspring from fragmented, smaller and/or disturbed populations. These data reinforce the importance of sourcing seeds from multiple trees for ecological restoration, and emphasise that tuart’s mating system and the genetic diversity of offspring is robust to some habitat disturbance and/or fragmentation.

The degree of clonality, interspecific hybridisation and inbreeding in rare species will have significant implications for maintenance of genetic diversity and resilience to environmental change, with related implications for immediate conservation management. Using microsatellites, we detected extensive clonality within the rare mallee, Eucalyptus absita, from a highly disturbed agricultural habitat in southwestern Australia. A total of just 16 unique genets, plus five putative hybrids with E. loxophleba, were detected across the known species range and these genets were estimated to be of considerable age. Each location possessed a unique genotype and overall diversity was moderate (H E = 0.547). The outcrossing rate in seedling progeny was low (t m = 0.281), reflecting a rarity of intraspecific sires and minimal inbreeding depression prior to seed dispersal. Of all seedling progeny, up to 19 % were putative hybrids. Our findings indicate that despite rarity and clonality, moderate levels of genetic diversity and the capacity to produce outcrossed seeds is maintained. However, the ongoing maintenance of E. absita genetic diversity is significantly compromised by a high rate of selfing and potential hybridisation in seedling progeny. Seeds collected for long-term storage or rehabilitation should be screened for inbreeding and hybridisation rates to improve conservation outcomes. All existing adults represent a unique portion of the genepool for conservation.

• Premise of the study: New microsatellite (simple sequence repeat [SSR]) primers were developed from Eucalyptus expressed sequence tags (ESTs) and optimized for genetic studies of the southwestern Australian tree E. gomphocephala, which is severely impacted by tree health decline and habitat fragmentation.• Methods and Results: A total of 133 gene-homologous EST-SSR primer pairs were designed for Eucalyptus, and 44 were screened in E. gomphocephala. Of these, 17 produced reliable amplification products and 11 were polymorphic. Between two and 13 alleles were observed per locus, and observed heterozygosities ranged from 0.172 to 0.867. All 17 EST-SSRs that amplified E. gomphocephala cross-amplified to at least one of E. marginata, E. camaldulensis, and E. victrix.• Conclusions: This set of EST-SSR primer pairs will be valuable tools for future population genetic studies of E. gomphocephala and other eucalypts, particularly for studying gene-linked variation and informing seed-sourcing strategies for ecological restoration.

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