Fine-scale genetic structure and gene dispersal in Centaurea corymbosa (Asteraceae) I. Pattern of pollen dispersal

Abstract

Pollen dispersal was characterized within a population of the narrowly endemic perennial herb, Centaurea corymbosa, using exclusion-based and likelihood-based paternity analyses carried out on microsatellite data. Data were used to fit a model of pollen dispersal and to estimate the rates of pollen flow and mutation/genotyping error, by developing a new method. Selfing was rare (1.6%). Pollen dispersed isotropically around each flowering plant following a leptokurtic distribution, with 50% of mating pairs separated by less than 11 m, but 22% by more than 40 m. Estimates of pollen flow lacked precision (0-25%), partially because mutations and/or genotyping errors (0.03-1%) could also explain the occurrence of offspring without a compatible candidate father. However, the pollen pool that fertilized these offspring was little differentiated from the adults of the population whereas strongly differentiated from the other populations, suggesting that pollen flow rate among populations was low. Our results suggest that pollen dispersal is too extended to allow differentiation by local adaptation within a population. However, among populations, gene flow might be low enough for such processes to occur.

Fine-Scale Genetic Structure and Gene Dispersal in Centaurea corymbosa (Asteraceae). II. Correlated Paternity Within and Among Sibships

“…Some unifications: The TwoGener approach was dewasps (Nason et al 1998)], where multiple paternity within fruits is the exception rather than the rule. A vised to infer pollen dispersal distances on the basis of the pattern of differentiation among pollen pools havsignificant impact of the timing of sib fertilization has also been reported recently in A. julibrissin (Irwin et al ing fertilized different maternal sibships Smouse 2001, 2002;Smouse et al 2001;. In animal-pollinated species, correlated paternity within fruits is reduced when pollen loads from different et al 2004).…”

“…This can be the degree of plant isolation or of the heterogeneity of the proximity of the nearest neighbors, the F S values done unambiguously at a locus unless both the offspring and its mother are heterozygous for the same pair of within each family were regressed on the number of flowering plants situated within 20 m of the mother alleles. For example, if an offspring carries alleles A and B and its mother alleles B and C, it means the father plant (20 m being approximately the mean distance between mates; Hardy et al 2004) as well as on the brought allele A. However, if the mother carried alleles A and B, the father could have brought allele A or allele variance of the distances to the five closest flowering plants.…”

“…Finally, the level of correlated paternity is a key parameter analyses, these approaches are much more convenient to apply (nonexhaustive sampling) and can be used on which many methods rely: for instance, as is detailed in the discussion, the so-called "TwoGener" approach with less-polymorphic markers. Maximum-likelihood approaches have also been developed to assess whether recently developed to assess pollen dispersal distances Smouse 2001, 2002;Smouse et al a particular pair of individuals are half-or full-sibs (e.g., González-Martínez et al 2003Irwin et al 2003;Austerlitz et al 2004) is fundamentally based on the level of correlated paternity.…”

“…Moreover, to assess if there was an effect of sibships, F S , was estimated following the approach deof selfing and biparental inbreeding, r p , 2⌽ FT and 2F S are all estimators of the proportion of full-sibs (P FS ) scribed previously in this section. Using 1000 simulation replicates, we assessed the 95% confidence intervals on within progeny arrays (Ritland 1988;Austerlitz and Smouse 2001). Similarly, 2F ij estimates the proportion the F S values.…”

“…When maternal sib pairs were distinguished according Correlated mating within progeny arrays: The paternity analysis detailed in Hardy et al (2004) identified the to the relative positions of seeds within and among capitula, or according to the sampling date of seeds (and thus fathers of 121 outcrossed progenies, making 121(121 Ϫ 1)/2 ϭ 7260 offspring pairs, 148 of these being maternal the phase of the flowering period when fertilization occurred), no significant effect was observed on F S values sib pairs (offspring sharing the same mother). Twentynine of these sib pairs were full-sibs, so that maternal (Table 1).…”