Genetic tests of the isolation of rare coastal dwarf populations of Banksia spinulosa

Abstract

In southern New South Wales, a suite of widespread plant species exhibit short-statured ‘dwarf’ growth forms on coastal headlands. It is unclear whether such populations are genetically distinct or whether dwarfism is a plastic response to the environment. We used four microsatellite markers to assess genetic differentiation among populations from coastal and inland sites for Banksia spinulosa var. spinulosa. We sampled plants from six locations, including from three ‘dwarf’ and three ‘normal’ populations. Mean levels of genetic diversity were slightly higher in the forest (Na = 7.07 ± 0.25; He = 0.80 ± 0.09) than on the coast (Na = 5.92 ± 0.70; He = 0.72 ± 0.10). In general, populations displayed genotypic diversity expected for outcrossed sexual reproduction, with 161 of 172 individuals displaying unique genotypes and mean values of FIS close to zero. However, we found evidence of at least limited clonal replication in each of four populations and, within one coastal population, 11 of 27 individuals displayed one of three replicated genotypes, implying that the effective population size may be considerably smaller than would be inferred from the number of plants at this site. Relative to studies with other Proteaceae, this set of populations showed low, although significant, levels of differentiation (global FST = 0.061; P < 0.001), with extremely low, although significant, divergence of forest and coastal populations (FRT = 0.009; P < 0.001). There was no evidence of isolation by distance. These data imply that coastal dwarf populations are genetically similar to more extensive inland populations but in at least one case, may be at a greater risk of extinction because of low effective population size.

Field of Dreams: Restitution of Pollinator Services in Restored Bird‐Pollinated Plant Populations

“…H e = 0.54–0.59) reflected levels recorded in the adjacent remnant site ( H e = 0.53), indicating successful genetic management in the collection of seed and establishment of seedlings in the restoration sites. However, these values are lower than those found at microsatellite loci for natural populations of other Banksia species (average H e = 0.60–0.77; He & Lamont ; He et al ; O'Brien et al ; Merwin et al ; Llorens et al ; Ritchie & Krauss ). This was a surprising result given a widespread distribution, generally large populations, obligate outcrossing and extensive pollen movement in B .…”

Does provenance matter? Fitness is not determined by genetic distance or the scale of pollen dispersal inGrevillea sphacelata(Proteaceae)

“…Our data support the population genetic studies carried out with other Proteaceae, including a range of Grevillea spp., in revealing similar patterns of population differentiation within and among populations of both predominantly bird‐ and insect‐pollinated self‐incompatible species (Millar, Byrne & Coates, ; O'Brien et al ., ; Forrest et al ., ). This is surprising, as observational (Roberts, Ayre & Whelan, ; Holmes et al ., ; Whelan, Beynon & Ayre, ) and experimental evidence (England et al ., ) suggests that, in foraging within subpopulations, birds are more likely than the most common insect visitors to move pollen between plants, producing higher rates of outcrossing and longer distance pollen flow within populations (Ayre, Whelan & Reid, ; Whelan et al ., ).…”

High adult mortality and failure of recruitment in a population of Banksia spinulosa following high‐intensity fire

“…Established plants are able to resprout from below-ground lignotubers. Populations of B. spinulosa have been found to be highly outcrossed and genetically diverse (Carthew et al 1988;Ayre et al 2010;O'Brien et al 2010). Episodes of sexually produced recruitment needed to maintain this diversity are only expected after fires but long-lived lignotubers and low mortality rates mean that even very rare germination events might be sufficient to maintain population persistence.…”

“…2010; O'Brien et al . 2010). Episodes of sexually produced recruitment needed to maintain this diversity are only expected after fires but long‐lived lignotubers and low mortality rates mean that even very rare germination events might be sufficient to maintain population persistence.…”