Long‐distance dispersal of seeds in the fire‐tolerant shrubBanksia attenuata

Abstract

Long‐distance dispersal (LDD) of seeds enables alleles, individuals and species of plants to (re)colonize suitable but remote habitats.Banksia attenuatais a long‐lived resprouting shrub restricted to dune crests in fire‐prone sclerophyll shrublands of the Eneabba sandplain, southwestern Australia. Highly polymorphic microsatellite DNA genetic markers and population assignment tests were employed to identify LDD immigrants among 788 individuals from 27 stands ofB. attenuatacomprising a metapopulation. Of the 487 (61.8% of the total) individuals unambiguously assigned to a unique source population, 27 (5.5%) were identified as immigrants by assignment to a known population other than that from which they were sampled, while the remaining 460 were assigned to the population from which they were sampled. The distance between source and sink populations for these immigrants ranged from 0.2 to 2.6 km, averaging 1.4 km, and broadly trending in the direction of seasonal winds. These results suggest thatB. attenuatahas similar long‐distance seed dispersal properties as its co‐occurring shorter‐lived and fire‐sensitive congener,B. hookeriana, despite fewer, larger and less mobile seeds. The frequency and distance of LDD for seeds observed in both species (5.5–6.8%) helps explain the persistence of populations on these geographically isolated dunes, where they are subject to local extinction from recurrent fire and severe summer drought, and will remain important under predicted climate change conditions. Analysis also revealed that species richness of the functional group to whichB. attenuatabelongs was positively correlated with the number of immigrants identified per dune, and such correlation was likely driven by environmental properties of the dunes, particularly water availability.