Varying levels of clonality and ploidy create barriers to gene flow and challenges for conservation of an Australian arid-zone ecosystem engineer, Acacia loderi (original) (raw)
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Plant Ecology, 2014
For plants capable of both sexual and clonal reproduction, the relative frequency of these reproductive modes is influenced by genetic and ecological factors. Acacia carneorum is a threatened shrub from the Australian arid zone that occurs as a set of small, spatially isolated populations. Sexual reproduction appears to be very rare: despite regular flowering, only two populations set seed. It is not known whether this reflects an ancient pattern, or results from rapid land use changes following arrival of Europeans in the region 150 years ago. We assessed genotypic variation throughout the range of A. carneorum using AFLP markers, to elucidate the relative importance of clonal and sexual reproduction in this species' history. Clonal diversity (CD) within populations ranged from 0 to 0.820 (mean CD = 0.270, SE = 0.094), but the relative abundances of genets were typically highly skewed. On average, the two fruiting populations had higher CD (mean CD = 0.590, SE = 0.265) than non-fruiting populations (mean CD = 0.179, SE = 0.077) (t = 2.315, p = 0.049), but most populations contained multiple genets. All genets were populationspecific, and there was substantial divergence among populations (U ST = 0.690), implying a long history of isolation. We conclude that clonality has predominated in A. carneorum populations, with occasional sexual recruitment, and that current failure of most populations to set seed likely reflects both a long history of asexual reproduction and effects of habitat disturbance. Conservation of this species may benefit from translocations to increase genotypic diversity within populations.
Clonality disguises the vulnerability of a threatened arid zone Acacia
Ecology and evolution, 2017
Long-lived, widespread plant species are expected to be genetically diverse, reflecting the interaction between large population sizes, overlapping generations, and gene flow. Such species are thought to be resilient to disturbance, but may carry an extinction debt due to reproductive failure. Genetic studies of Australian arid zone plant species suggest an unusually high frequency of asexuality, polyploidy, or both. A preliminary AFLP genetic study implied that the naturally fragmented arid zone tree, Acacia carneorum, is almost entirely dependent on asexual reproduction through suckering, and stands may have lacked genetic diversity and interconnection even prior to the onset of European pastoralism. Here we surveyed microsatellite genetic variation in 20 stands to test for variation in life histories and further assessed the conservation status of the species by comparing genetic diversity within protected stands in National Parks and disturbed range lands. Using herbarium record...
Ecology and Evolution
Widespread plant species are expected to maintain genetic diversity and gene flow via pollen and seed dispersal. Stature is a key life history trait that affects seed and potentially pollen dispersal, with limited stature associated with limited dispersal and greater genetic differentiation. We sampled Hill's tabletop wattle (Acacia hilliana) and curry wattle (Acacia spondylophylla), two co-distributed, widespread, Acacia shrubs of low stature, across the arid Pilbara region of northwestern Australia. Using chloroplast sequence and nuclear microsatellite data we evaluated patterns of population genetic and phylogeographic diversity and structure, demographic signals, ratios of pollen to seed dispersal, evidence for historical refugia, and association between elevation and diversity. Results showed strong phylogeographic (chloroplast, G ST = 0.831 and 0.898 for A. hilliana and A. spondylophylla, respectively) and contemporary (nuclear, F ST = 0.260 and 0.349 for A. hilliana and A. spondylophylla, respectively) genetic structure in both species. This indicates limited genetic connectivity via seed and pollen dispersal associated with Acacia species of small stature compared to taller tree and shrub acacias across the Pilbara bioregion. This effect of stature on genetic structure is superimposed on moderate levels of genetic diversity that were expected based on widespread ranges (haplotype diversity h = 25 and 12; nuclear diversity He = 0.60 and 0.47 for A. hilliana and A. spondylophylla, respectively). Contemporary genetic structure was congruent at the greater landscape scale, especially in terms of strong genetic differentiation among geographically disjunct populations in less elevated areas. Measures of diversity and connectivity were associated with traits of greater geographic population proximity, population density, population size, and greater individual longevity, and some evidence for range expansion in A. hilliana. Results illustrate that low stature is associated with limited dispersal and greater patterns of genetic differentiation for congenerics in a common landscape and highlight the complex influence of taxon-specific life history and ecological traits to seed and pollen dispersal. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Diversity, 2021
Maximising genetic diversity in conservation efforts can help to increase the chances of survival of a species amidst the turbulence of the anthropogenic age. Here, we define the distribution and extent of genomic diversity across the range of the iconic but threatened Acacia purpureopetala, a beautiful sprawling shrub with mauve flowers, restricted to a few disjunct populations in far north Queensland, Australia. Seed production is poor and germination sporadic, but the species occurs in abundance at some field sites. While several thousands of SNP markers were recovered, comparable to other Acacia species, very low levels of heterozygosity and allelic variation suggested inbreeding. Limited dispersal most likely contributed towards the high levels of divergence amongst field sites and, using a generalised dissimilarity modelling framework amongst environmental, spatial and floristic data, spatial distance was found to be the strongest factor explaining the current distribution of ...
Biogeographic origins and reproductive mode of naturalised populations of Acacia saligna
Australian Journal of Botany, 2012
Acacia saligna (Labill.) H.L.Wendl. is a species complex with an extensive history of anthropogenic utilisation and distribution. The taxon is naturalised and invasive in many countries. Extensive morphological variation makes accurate taxonomic identification of populations difficult. We used population genetic analysis to determine the biogeographic origins of 12 naturalised populations sampled from throughout south-eastern South Australia and assess the mode of reproduction (seedling or root suckering) at sites with active recruitment. Ten naturalised populations were assigned to Eastern ‘saligna’, although some also showed a lesser degree of affinity with other entities. A single population was assigned to Western ‘saligna’, but showed some affinity with Eastern ‘saligna’, and one population assigned to subsp. ‘lindleyi’ showed some affinity with Northern ‘lindleyi’. These assignments suggest that although several genetic entities of A. saligna are represented in South Australia...
PLOS ONE, 2016
The influence of geographic range on species persistence has long been of interest and there is a need for a better understanding of the genetic consequences for species with restricted distributions, particularly with the increasing rate of global species extinctions. However, the genetic effects of restricted range are often confounded by the impacts of population distribution. We compared chloroplast and nuclear genetic diversity and differentiation in two acacias, the restricted, patchily distributed Acacia atkinsiana and the widespread, semi-continuously distributed A. ancistrocarpa. Lower intra-population diversity and higher differentiation between populations were seen in A. atkinsiana compared to its widespread congener, A. ancistrocarpa. There was little evidence of geographical influences on population genetic structure in A. ancistrocarpa whereas A. atkinsiana exhibited nuclear genetic structure with isolation by distance, differentiation of near-coastal populations from those in the ranges, and differentiation of peripheral populations from those in the centre of the distribution. These results are consistent with expectations of the effect of geographic range and population distribution on genetic diversity, but indicate that distribution of populations rather than geographic range has influenced the observed genetic structure. The contrasting patterns observed here demonstrate that conservation approaches for species management and ecological restoration need to consider the distribution of populations in geographically restricted species.
Restoration Ecology, 2010
It is essential to understand the patterns of pollen dispersal in remnant vegetation occupying highly disturbed landscapes in order to provide sustainable management options and to inform restoration programs. Direct and indirect methods of paternity analysis were used to detect genetic contamination via inter-subspecific pollen dispersal from a planted stand of nonlocal Acacia saligna ssp. saligna (ms) into remnant roadside patches of local A. saligna ssp. lindleyi (ms). Genetic contamination was detected in 25.5% (indirect paternity assignment) to 32% (direct paternity assignment) of ssp. lindleyi progeny and occurred over a distance of 1.6 km. The results support studies that suggest genetic continuity is maintained by high levels of pollen dispersal in temperate entomophilous species. The results also indicate that patchily distributed remnant populations may be exposed to substantial amounts of genetic contamination from large-scale restoration with native taxa in the highly fragmented agricultural landscape of southern Western Australia. Management practices to reduce the risk of genetic contamination are considered.
Biological Journal of The Linnean Society, 2016
Comparative studies of sympatric species that integrate both phylogeographical and population genetic approaches provide insight into how demographic events and life history traits shape adaptive potential and drive species persistence. Such studies are rare for species-rich and strongly structured environments, especially those of the southern hemisphere. For two sympatric, perennial shrubs of the south-west Western Australian semi-arid zone, Grevillea globosa and Mirbelia sp. Bursarioides, we assessed historical and contemporary genetic diversity and structure, demographic processes and ratios of pollen to seed dispersal. Phylogeographical structure was not detected and haplotype networks were star-like. Number of haplotypes, nucleotide diversity, haplotype diversity, and allelic diversity were statistically significantly lower for G. globosa than for M. sp. Bursarioides. Levels of haplotype divergence and more contemporary genetic divergence and expected heterozygosity were lower for G. globosa than for M. sp. Bursarioides, but differences were not statistically significant. Both species exhibited signals of isolation by distance and low pollen to seed dispersal ratios (5.26:1 and 6.88:1). Grevillea globosa displayed signals of historical and contemporary demographic expansion. Results imply an important role for aspects of seed ecology that impact population demography, as well as direct dispersal and a significant contribution of seed dispersal to genetic connectivity in a semi-arid landscape.
Applications in Plant Sciences, 2015
Premise of the study: Microsatellite markers were developed for the common arid Australian shrub Acacia ligulata (Fabaceae) and the threatened overstory trees A. melvillei and A. pendula . • Methods and Results: DNA sequence data generated by 454 sequencing were used to identify microsatellite nucleotide repeat motifs. Including previously developed primer sets, we report on the development of 10 polymorphic microsatellite loci for each species. Six of these were novel for A. melvillei and A. ligulata , and fi ve were novel for A. pendula , while fi ve more each were transferred from primers developed for related species ( A. carneorum and A. loderi ). We found three to 17 alleles per locus for each species, with high multilocus genotypic diversity within each of two A. ligulata and A. pendula stands, and one A. melvillei population. A second A. melvillei stand appeared to be monoclonal. • Conclusions: These markers will allow assessment of population genetics, mating systems, and connectedness of populations of these and possibly other arid-zone acacias.
Australian Journal of Botany, 2011
Traditional morphological taxonomic classification is problematic in the Acacia saligna (Labill.) H.L.Wendl. species complex. Reliable identification of entities within the species is essential due to its extensive use both in Australia and overseas, its propensity for weediness, and its ongoing development for use in agroforestry. We used a Bayesian analysis approach to assess genetic structure in populations across the species natural range and to define the natural distributions of various genetic entities. The results indicate that three highly divergent genetic entities are apparent in the A. saligna species complex with further fine-scale genetic subdivision present within two. The three primary genetic entities correspond to the informally described subsp. ‘saligna’ and subsp. ‘pruinescens’ combined, subsp. ‘stolonifera’, and subsp. ‘lindleyi’. Within this primary structure two further entities are apparent; one separating subsp. ‘saligna’/‘pruinescens’ into eastern and weste...