Low neighbourhood size and high interpopulation differentiation in the endangered shrub Grevillea iaspicula McGill (Proteaceae)

Mating system parameters and genetic diversity were examined for five popul ations of the endangered shrub Grevillea iaspicula (Proteaceae). Controlled pollinations show that G. iaspicula has an effective self-incompatibility system and little potential for agamospermy. This is reflected in uniformly high multilocus outcrossing rates (t(m) = 0.96-1.00). However, average pat ernal diversity within open-pollinated sibships is low (r(p) = 0.31-0.54), suggesting that mating within populations is quite restricted. Despite the small size of most populations (four of the five populations studied have f ewer than 20 reproductive individuals) the species still possesses moderate to high allelic richness (A = 1.6-2.5). Interpopulation genetic differenti ation is high (D = 0.04-0.32), suggesting that gene flow is limited, even a mong populations separated by only a few kilometres.