Low Rate of Between-Population Seed Dispersal Restricts Genetic Connectivity and Metapopulation Dynamics in a Clonal Shrub

Abstract

Clonal species normally have low seed production, low recruitment rates and long lifespans, and it is expected that the rates of long-distance dispersal (LDD) of seeds will be low as well. Banksia candolleana is a clonal shrub in Mediterranean-type, fire-prone sclerophyll shrublands of southwestern Australia, whose reproductive biology and population dynamics contrast with those of co-occurring nonclonal congeneric species, all of which are restricted to a mosaic of sand dunes set within a matrix of inhospitable swales. Using microsatellite markers, we genotyped 499 plants in all 15 populations of B. candolleana within a 12-km2 area, assessed population genetic differentiation, and quantified the effective rate of interpopulation seed dispersal through genetic assignment of individuals to populations. We measured life history, reproductive and demographic attributes, and compared these with two co-occurring Banksia species, a non-clonal resprouter and a nonsprouter. B. candolleana has much higher levels of population genetic differentiation, and one-third the rate of interpopulation seed migration, as the other two species (2.2% vs 5.5−6.8% of genotyped plants inferred to be immigrants), though distances reached by LDD are comparable (0.3−2.3 km). The low rate of interpopulation dispersal was supported by an analysis of the age structure of three populations that suggests a mean interdune migration rate of <800 m in 200 years, and 60% of suitable dunes remain uninhabited. Thus, B. candolleana has poor properties for promoting long-distance dispersal. It is unclear if these are idiosyncratic to this species or whether such properties are to be expected of clonal species in general where LDD is less critical for species survival.

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 .…”

Evolution of a hotspot genus: geographic variation in speciation and extinction rates in Banksia (Proteaceae)

“…Unfortunately, this hypothesis will be difficult to test in Banksia until good data on dispersal ability (e.g. [28,29] become available for many species. Even then, with only two comparisons it would be difficult to support this hypothesis to the exclusion of possible confounding factors.…”

Biodiversity hotspots and Ocbil theory

“…teretifolius (Myrtaceae) Sampson et al (2013) x Banksia candolleana (Proteaceae) Merwin et al (2013) x Terrestrial fauna and flora with dated phylogenies reviewed Rix et al 2014.…”

“…x Banksia candolleana (Proteaceae) Merwin et al (2013) x Clonality and fine-scale genetic structure two rare sedges (Lepidosperma, Cyperaceae)…”