David J. Coates

Assessing the benefits and risks of translocations in changing environments: a genetic perspective

Translocations are being increasingly proposed as a way of conserving biodiversity, particularly in the management of threatened and keystone species, with the aims of maintaining biodiversity and ecosystem function under the combined pressures of habitat fragmentation and climate change. Evolutionary genetic considerations should be an important part of translocation strategies, but there is often confusion about concepts and goals. Here, we provide a classification of translocations based on specific genetic goals for both threatened species and ecological restoration, separating targets based on ‘genetic rescue’ of current population fitness from those focused on maintaining adaptive potential. We then provide a framework for assessing the genetic benefits and risks associated with translocations and provide guidelines for managers focused on conserving biodiversity and evolutionary processes. Case studies are developed to illustrate the framework.

Seed supply for broadscale restoration: maximizing evolutionary potential.

Restoring degraded land to combat environmental degradation requires the collection of vast quantities of germplasm (seed). Sourcing this material raises questions related to provenance selection, seed quality and harvest sustainability. Restoration guidelines strongly recommend using local sources to maximize local adaptation and prevent outbreeding depression, but in highly modified landscapes this restricts collection to small remnants where limited, poor quality seed is available, and where harvesting impacts may be high. We review three principles guiding the sourcing of restoration germplasm: (i) the appropriateness of using ‘local’ seed, (ii) sample sizes and population characteristics required to capture sufficient genetic diversity to establish self‐sustaining populations and (iii) the impact of over‐harvesting source populations. We review these topics by examining current collection guidelines and the evidence supporting these, then we consider if the guidelines can be improved and the consequences of not doing so. We find that the emphasis on local seed sourcing will, in many cases, lead to poor restoration outcomes, particularly at broad geographic scales. We suggest that seed sourcing should concentrate less on local collection and more on capturing high quality and genetically diverse seed to maximize the adaptive potential of restoration efforts to current and future environmental change.

Priority setting and the conservation of Western Australia's diverse and highly endemic flora

A fundamental role of government conservation agencies is to set priorities for the conservation and management of biodiversity. This is particulary important in an area such as Western Australia which has a rich and highly endemic flora with over 11,000 listed native vascular plants. Legislation provides an initial focus for priority setting through the listing and protection of threatened flora, although this excludes over 1900 Western Australian plant taxa which are poorly known but may be of conservation significance. The priority setting process for the conservation of this flora, discussed herein, focuses on single taxa, groups of taxa within geographic regions, populations and threatening processes. This process is particularly applicable to the highly diverse and endemic flora of the south-west Botanical Province. Within this region there has been extensive habitat loss and degradation over the last 100 years. Currently the prioritisation process has identified 95 critically endangered taxa in the southwest which require immediate remedial action to prevent extinction. Actions such as translocations are already showing promise, but with this number of critically endangered taxa and limited resources there may also need to be some ranking of taxa for immediate translocation. Although the priority setting process outlined here relates primarily to taxa, we emphasise that the conservation of this flora is also addressed at ecosystem and ecological community levels, and that each approach has its merits depending upon land tenure, location within the State and, in particular, the level of land degradation.

Defining conservation units in a rich and fragmented flora: implications for the management of genetic resources and evolutionary processes in south-west Australian plants

The south-west Australian flora shows a diverse array of evolutionary patterns and exceptionally high species diversity. A significant component of this flora consists of relictual species which often have naturally fragmented and geographically restricted distributions. Many of these species appear to apportion significant levels of genetic diversity among populations. Diversity at both the population and species level presents a major challenge to the development of appropriate conservation strategies for this flora. To be effective these strategies should not only aim to preserve current levels of species diversity, but also consider intraspecific variation and the evolutionary and ecological processes associated with the generation and maintenance of that variation. The identification and characterisation of conservation units, based on population genetic structure and phylogeographic patterns within species, provide a useful basis upon which more general conservation principals can be developed for the maintenance of these processes. Population genetic structure and phylogeographic studies are used to show how conservation units can be identified in Lambertia orbifolia, Acacia anomala, Stylidium coroniforme, Stylidium nungarinense and Banksia cuneata, and taxa from a range of other genera. Determining conservation units in these taxa defines not only suitable units for their conservation but also the appropriate geographical scale for management. These findings indicate the potential this approach can have in determining strategies and priorities for the conservation of the south-west Australian flora.

Extensive pollen dispersal in a bird-pollinated shrub, Calothamnus quadrifidus, in a fragmented landscape

Pollen dispersal was investigated in six populations of Calothamnus quadrifidus, a bird‐pollinated shrub in the fragmented agricultural region of southern Western Australia. Paternity analysis using six microsatellite loci identified a pollen source within populations for 67% of seedlings, and the remainder were assumed to have arisen from pollen sources outside the populations. Outcrossing was variable, ranging from 5% to 82%, and long‐distance pollen dispersal was observed in all populations with up to 43% of pollen sourced from outside the populations over distances of up to 5 km. This extensive pollen immigration was positively associated with population size but not isolation. Comparison of two populations of similar size but different density showed greater internal pollination and less selfing in the denser population, suggesting an influence of density on pollinator behaviour. The study revealed extensive long‐distance pollen dispersal for C. quadrifidus within this fragmented agricultural landscape and highlighted the interaction between reserve populations and isolated road verge remnants in maintaining genetic connectivity at the landscape scale.

Phylogeographical patterns in chloroplast DNA variation within the Acacia acuminata (Leguminosae: Mimosoideae) complex in Western Australia

Abstract The Acacia acuminata complex includes three taxa, A. acuminata ssp. acuminata, A. acuminata ssp. burkittii and A. oldfieldii, along with several informal variants of A. acuminata. It is widespread throughout southern Australia with the centre of diversity in south‐west Western Australia. Phylogeographical patterns in the complex were investigated using a nested clade analysis of cpDNA RFLPs from 25 populations in Western Australia. Except for A. oldfieldii that was clearly identified as a distinct entity, haplotypes were not restricted to sub‐specific taxa or variants within A. acuminata. There was significant association between phylogenetic position of many haplotypes and their geographical distribution. The fine‐scale phylogeographical patterns were complex but at deeper levels in the phylogeny there was evidence of divergence between two lineages. The pattern of shared haplotypes between lineages suggests retention of ancestral polymorphism as a result of incomplete lineage sorting. The divergence of these lineages is consistent with fragmentation caused by climatic instability during the Pleistocene.

Genetic divergence and the mating system in the endangered and geographically restricted species, Lambertia orbifolia Gardner (Proteaceae)

Population genetic structure and the mating system were investigated in the endangered plant Lambertia orbifolia. This species is geographically restricted with two disjunct groups of populations. Twelve out of 19 allozyme loci were polymorphic and four were suitable for mating system studies. Levels of genetic variation within populations were comparable to other long-lived woody shrub endemics. Genetic divergence between population groups was very high (D = 0.252) and the FST over all populations was 0.441. Gene flow estimates within population groups were low even though the maximum geographical distance between any pair of populations is 15 km and could be attributed to the localized movement of bird pollinators. Mating system studies on four populations showed consistently low levels of outcrossing, compared with other Proteaceae. Correlations of outcrossed paternity were moderately high and all were significantly greater than zero. Values ranged from rp = 0.33, in the two largest and very dense populations, to the highest value of rp = 0.54 in a smaller low-density population. The current population genetic structure in L. orbifolia is probably the result of local extinction of intervening populations because of Pleistocene climatic change and increased aridity, and extended isolation of the two remnants. It is proposed that the phylogenetically distinct Narrikup population group be recognized as a separate conservation unit and be given high priority for conservation action.

Evaluating the influence of different aspects of habitat fragmentation on mating patterns and pollen dispersal in the bird-pollinated Banksia sphaerocarpa var. caesia

Habitat fragmentation can significantly affect mating and pollen dispersal patterns in plant populations, although the differential effects of the various aspects of fragmentation are poorly understood. In this study, we used eight microsatellite loci to investigate the effect of fragmentation on the mating system and pollen dispersal within one large and eight small population remnants of Banksia sphaerocarpa var. caesia, a bird‐pollinated shrub in the southern agricultural region of Western Australia. The large population had a much larger neighbourhood size and lower selfing rate, maternal pollen pool differentiation and within‐plot mean pollen dispersal distance than the small populations. Outcrossing was consistently high and ranged from 85.7% ± 2.6 to 98.5% ± 0.9, and mating patterns suggested nearest‐neighbour pollination. Pollen immigration into small populations ranged from 2.8% ± 1.8 to 16.5% ± 3.2. Using the small populations, we tested for correlations between various fragmentation variables and mating system and pollen dispersal parameters. We found significant negative linear relationships between population isolation and outcrossing rate; population shape and neighbourhood size; and conspecific density and mean pollen dispersal distance. There were significant positive linear relationships between population shape and pollen pool differentiation and between population size and number of different fathers per seed crop. Our results suggest that birds may use a series of fragmented populations as a vegetation corridor while foraging across the landscape and that population connectivity is a critical determinant of pollinator visitation. Our results also suggest that the effect of a linear population shape on the mating system and pollen dispersal is routinely underestimated.

The mating system and patterns of genetic variation in Banksia cuneata A. S. George, Proteaceae

The mating system and patterns of genetic variation were studied in the rare and geographically restricted species Banksia cuneata. Nine out of 20 allozyme loci analysed were polymorphic and six were considered suitable for estimating mating system parameters. Estimates of the outcrossing rate ranged from t = 0.67 to t = 0.95 and the effective selfing rate from E = 0.14 to E = 0.25, and showed significantly lower levels of outcrossing in two populations than reported for other Banksia species. This appeared to be due to increased biparental inbreeding associated with high plant density and reduced or altered pollinator activity associated with habitat disturbance. The six populations were clearly divided into two population groups ([Dmacr ], between groups = 0.088) with significant gene flow estimated among populations within groups but not amoung groups. Although B. cuneata has an extremely restricted geographical range and is largely bird-pollinated, significant differentiation has occurred between some populations over relatively small geographical distances. The differentiation correlates with certain ecological features of the region and is a likely result of the dissected population structure and relatively small sized populations found in this species.

Divergence in the chloroplast genome and nuclear rDNA of the rare Western Australian plant Lambertia orbifolia Gardner (Proteaceae)

The population genetic structure of the Australian plant Lambertia orbifolia was investigated for chloroplast DNA (cpDNA) and rDNA based on restriction fragment length polymorphism. Variation was assessed in 14–20 individuals from six populations with probes covering the majority of the chloroplast genome and the whole rRNA gene unit. For cpDNA, eight mutations were detected which were distributed over five haplotypes. Nucleotide diversity in the species was high and the majority of this diversity was distributed between populations with diversity within populations restricted to a single population. There was significant differentiation between the two regions in the species distribution with the Narrikup region being distinguished by a single haplotype that was characterized by six unique mutations. Variation in rDNA was detected with three gene length variants present in most individuals. However, the Narrikup region was characterized by homogenization of the gene unit to a single length variant in all individuals. The divergence of the Narrikup region suggests that the disjunction in the species distribution has been present for a long time and the two regions represent separate evolutionary lineages.