Heidi Nistelberger

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.

Phylogeographic evidence for two mesic refugia in a biodiversity hotspot

Phylogeographic studies of flora in species-rich south-western Australia point to complex evolutionary histories, reflecting patterns of persistence and resilience to climatic changes during the Pleistocene. We asked whether coastal areas of the mid-west and south, as well as granite outcrops and inland ranges, have acted as major refugia within this region during Pleistocene climatic fluctuations by analysing phylogeographic patterns in the shrub Calothamnus quadrifidus R.Br. (Myrtaceae). We determined variation in chloroplast DNA data for 41 populations across the geographic range. Relationships and major clades were resolved using parsimony and Bayesian analyses. We tested for demographic and spatial expansion of the major clades and estimated clade divergence dates using an uncorrelated, lognormal relaxed clock based on two conservative chloroplast mutation rates. Two distinct phylogeographic clades were identified showing divergence during the Pleistocene, consistent with other phylogeographic studies of south-west Australian flora, emphasising the impact of climatic oscillations in driving divergence in this landscape. The southern clade was more diverse, having higher haplotype diversity and greater genetic structure, while the northern clade showed evidence of fluctuation in population size. Regions of high haplotype diversity with adjacent areas of low diversity observed in each clade indicated the locations of two coastal refugia: one on the south coast and another along the mid-west coast. This is the first evidence for major Pleistocene refugia using chloroplast genetic data in a common, widespread species from this region.

Strong phylogeographic structure in a millipede indicates pleistocene vicariance between populations on banded iron formations in semi-arid Australia

The Yilgarn Banded Iron Formations of Western Australia are topographical features that behave as terrestrial islands within the otherwise flat, semi-arid landscape. The formations are characterised by a high number of endemic species, some of which are distributed across multiple formations without inhabiting the intervening landscape. These species provide an ideal context for phylogeographic analysis, to investigate patterns of genetic variation at both spatial and temporal scales. We examined genetic variation in the spirostreptid millipede, Atelomastix bamfordi, found on five of these Banded Iron Formations at two mitochondrial loci and 11 microsatellite loci. Strong phylogeographic structuring indicated the five populations became isolated during the Pleistocene, a period of intensifying aridity in this landscape, when it appears populations have been restricted to pockets of moist habitat provided by the formations. The pattern of reciprocal monophyly identified within the mtDNA and strong differentiation within the nuclear microsatellite data highlight the evolutionary significance of these divergent populations and we suggest the degree of differentiation warrants designation of each as a conservation unit.

Isolation and characterisation of 14 microsatellite loci from a short-range endemic, Western Australian tree, Banksia arborea (C.A. Gardner)

Fourteen nuclear microsatellite markers were developed for the short-range endemic tree, Banksia arborea to examine patterns of genetic diversity and structure across the species’ restricted distribution. One hexanucleotide, three trinucleotide and 10 dinucleotide repeat loci were developed and tested on 24 individuals from one population. The number of alleles per locus ranged from 2 to 11. Observed and expected heterozygosity ranged from 0 to 0.833 and 0.044 to 0.823 respectively. All loci showed independent inheritance and null alleles are suspected to occur in four loci.

Isolation and characterization of microsatellites in the woody shrub, Banksia sphaerocarpa var. caesia (Proteaceae)

Microsatellite markers were developed for the Australian bird‐pollinated woody shrub Banksia sphaerocarpa var. caesia to study gene flow among populations in a highly fragmented landscape. Eight loci were developed, and in a sample of 40 individuals from one population, the number of alleles per locus ranged from five to 21 and observed heterozygosities ranged from 0.385 to 0.914. All eight loci showed independent inheritance. Analysis of open‐pollinated progeny arrays confirmed Mendelian inheritance at seven loci, while null alleles were suspected at the remaining locus.

Isolation and characterisation of 11 microsatellite loci from the Western Australian Spirostreptid millipede, Atelomastix bamfordi

Nuclear microsatellite markers were developed for the Western Australian, short-range endemic millipede Atelomastix bamfordi to study patterns of population genetic structure across the species’ terrestrial island-like distribution. Five dinucleotide, one trinucleotide, four tetranucleotide and one pentanucleotide repeat loci were developed and tested on 22 individuals sampled from one population. The number of alleles per locus ranged from 2 to 11 and observed heterozygosity ranged from 0.091 to 0.773. Null alleles were suspected to occur at four loci, but all 11 loci showed independent inheritance. Four loci were useful in cross-amplification in another Atelomastix species.

Isolation and characterisation of ten microsatellite loci from a Western Australian tree, Banksia sessilis (Proteaceae)

Ten nuclear microsatellite markers were developed for Banksia sessilis, a tree endemic to Western Australia to assess whether patterns of genetic diversity and structure reflect the taxonomic varieties currently described, one of which is a priority species for conservation. One tetranucleotide, three trinucleotide and six dinucleotide repeat loci were tested on 24 individuals from each of two populations. All loci showed independent inheritance and were polymorphic. The number of alleles ranged from two to seven. Observed heterozygosity ranged from 0.083 to 0.750 and expected heterozygosity from 0.080 to 0.718.