Mating patterns and pollen dispersal in a natural knobcone pine (Pinus attenuate Lemmon.) stand

Abstract

Mating system and effective pollen dispersal were studied in a natural stand of knobcone pine (Pinus attenuata Lemmon.) using 11 isozyme loci. Analyses were performed by fitting neighbourhood and mixed-mating models to multilocus genotypic arrays of offspring from four mother trees. Neighbourhoods consisted of all potential outcross males within 11 m of each mother tree (44, on average). Average outcrossing rates of the mother trees were estimated to be 0.97 and 0.96 for the respective models, whereas the population-wide outcrossing rate based on the mixed-mating model and a broader sample of mother trees was 0.92. The estimated proportion of offspring sired by males outside the neighbourhood of each mother tree was 0.56. Thus about 41 per cent of matings resulted from outcrossing with nearby males (within neighbourhoods). Distance and direction of individual males from mother trees and the size (tree height) of males played significant roles in determining outcross mating patterns within neighbourhoods. Male mating success increased with both proximity and tree size, although males east of mother trees accounted for more offspring than males in other directions.Despite the role of proximity, directionality and tree size in determining mating success within neighbourhoods, the effective number of males mating with each female seems to be large.Keywords: gene flow, mating success, mating Pinus attenuata. IntroductionMating systems and patterns of pollen dispersal play a central role in plant population genetics (Levin & Kerster, 1974;Hamrick, 1989). They influence effective population size and the degree of population subdivision resulting either from drift or differential selection. In addition, they affect levels of inbreeding and genetic structure within populations. Knowledge of mating systems and gene flow is also important for managing breeding populations (Levin & Kerster, 1974;Adams & Birkes, 1991) and for designing efficient genetic conservation strategies (Ledig, 1986;Hamrick et al., 1991 (Clegg, 1980;Brown, 1990; Mitton, 1992). Mating pattern analysis, however, has usually been restricted to estimation of parameters in the mixedmating model, which subdivides all mating events into two classes: self-fertilization and random outcrossing (Fyfe & Bailey, 1951). The mixed-mating model makes several assumptions, including that the probability of an outcross is independent of maternal genotype, and outcross pollen-pool allele frequencies are homogeneous across maternal parents (Brown et a!., 1985;Neale & Adams, 1985).Evidence in forest trees, however, indicates that these and other assumptions of the mixed-mating model are often violated (Mitton, 1992). In addition, this mating model does not describe patterns of outcross mating within populations, such as the extent to which male mating success is a function of proximity to females or pollen fecundity.Methods of estimating fertilities of individual males within populations, based on genotypic arrays 252 J. BURCZYK ETAL.of offspring of individual mothers, wer...

Inter-sexual competition in a dioecious grass

“…Little is known about mechanisms responsible for this pattern, although spatial segregation of the sexes is widespread, occurring in over 30 species from 20 families (Bertiller et al 2002;Bierzychudek and Eckhart 1988;Dudley 2006;Eppley et al 1998;Iglesias and Bell 1989;Korpelainen 1991;Lokker et al 1994;Shea et al 1993;Stark et al 2005). Spatial segregation of males and females is surprising in sessile organisms because an increase in distance between the sexes should reduce fertilization success and presumably the fitness of each individual (e.g., Bawa and Opler 1977;Brazeau and Lasker 1992;Burczyk et al 1996;Levitan et al 1992).…”

Allocating individuals to avoid inbreeding in ex situ conservation plantations: so far, so good

“…The rest of parameters are as in Figure 4 Conserv Genet (2009) 10:45-57 55 and even better performance is expected in more inbred conservation populations. Finally, the new method is amenable to modifications accounting for other factors affecting the probability of mating, such as differences in male fecundity (for instance, due to quantity and/or quality of pollen; Burczyk et al 1996;Oddou-Muratorio et al 2005) or phenological overlapping (Robledo-Arnuncio et al 2004 and references therein). A simple way to account for these factors would be to introduce weights in the probability of mating, p(x, y), in equation (1) of the form: k i u ij = P k2N k k u kj ; where k i is the male fecundity of the ith individual, u ij the phenological overlapping of the ith pollen donor with the jth mother tree and N is the total number of trees in the plantation.…”

Reconstruction of pedigrees in clonal plant populations

“…include the sampling location of the genotypes (e.g. Adams et al, 1992;Burczyk et al, 1996;Smouse et al, 1999;Hadfield et al, 2006). In principle, it is possible to add the corresponding prior probability distributions in our model.…”

“…Ellstrand and Marshall (1985) and Meagher and Thompson (1987). It has been used mainly to find correlations between phenotypes and reproductive success, or to estimate pollen-mediated gene flow (Smouse and Meagher, 1994;Burczyk et al, 1996;Smouse et al, 1999;Meagher et al, 2003;Wright and Meagher, 2004). To a lesser extent, parentage inference and related methods are used to estimate recent rates of self-fertilization (selfing) in a population (Ritland and Jain, 1981;David et al, 2007;Wilson and Dawson, 2007;Jarne and David, 2008).…”