Wide outcrossing provides functional connectivity for new and old Banksia populations within a fragmented landscape
Habitat fragmentation affects landscape connectivity, the extent of which is influenced by the movement capacity of the vectors of seed and pollen dispersal for plants. Negative impacts of reduced connectivity can include reduced fecundity, increased inbreeding, genetic erosion and decreased long-term viability. These are issues for not only old (remnant) populations, but also new (restored) populations. We assessed reproductive and connective functionality within and among remnant and restored populations of a common tree, Banksia menziesii R.Br. (Proteaceae), in a fragmented urban landscape, utilising a genetic and graph theoretical approach. Adult trees and seed cohorts from five remnants and two restored populations were genotyped using microsatellite markers. Genetic variation and pollen dispersal were assessed using direct (paternity assignment) and indirect (pollination graphs and mating system characterisation) methods. Restored populations had greater allelic diversity (Ar = 8.08; 8.34) than remnant populations (Ar range = 6.49–7.41). Genetic differentiation was greater between restored and adjacent remnants (FST = 0.03 and 0.10) than all other pairwise comparisons of remnant populations (mean FST = 0.01 ± 0.01; n = 16 P = 0.001). All populations displayed low correlated paternity (rp = 0.06–0.16) with wide-ranging realised pollen dispersal distances (< 1.7 km) and well-connected pollen networks. Here, we demonstrate reproductive and connective functionality of old and new populations of B. menziesii within a fragmented landscape. Due to long-distance pollination events, the physical size of these sites underestimates their effective population size. Thus, they are functionally equivalent to large populations, integrated into a larger landscape matrix.
KeywordsBanksia menziesii Restoration Mating system Pollinator services Popgraph
Thanks to Janet Anthony for assistance with the genetic work undertaken in the laboratory and Carole Elliott and Bryn Funnekotter for providing comments and helpful suggestions for improving the paper. This work was supported by Rocla Quarry Products (now Hanson Construction Materials), a Holsworth Wildlife Research Endowment and a Friends of Kings Park writing scholarship to ALR, the Botanic Gardens and Parks Authority and a linkage grant to SLK from the Australian Research Council (LP100100620). ALR was supported by an Australian Postgraduate Award during this study.
Author contribution statement
ALR, PGN, EAS and SLK conceived and designed the research. ALR performed the study and analysed the data. Popgraph analysis was performed by ALR and RJD. All authors contributed to writing the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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