Paternal bottlenecks in fragmented populations of the grassland daisy Rutidosis leptorrhynchoides

Allozyme markers were used to estimate mating system parameters in nine fra gmented populations of the grassland daisy Rutidosis leptorrhynchoides that differed in size and spatial isolation. Multilocus estimates of outcrossin g rate did not differ significantly among populations, all indicating a hig h level of outcrossing (t(m) = 084-1.0). Small populations showed greater d ivergence than large populations between the allele frequencies in the popu lation and those in the pollen pool, indicating paternal bottlenecks. Isola ted populations of fewer than 200 individuals also exhibited higher correla tions of outcrossed paternity (r(p)) than larger populations, indicating th e production of more full-sibs within families. The combination of paternal bottlenecks and correlated paternity increases the genetic identity of pro geny across families and predisposes populations to biparental inbreeding i n subsequent generations. As over half the remaining populations of R. lept orrhynchoides contain fewer than 200 plants, such second-order inbreeding m ay threaten the viability of the species if it is associated with significa nt inbreeding depression.