Complex patterns of mating revealed in a Eucalyptus regnans seed orchard using allozyme markers and the neighbourhood model

Abstract

The neighbourhood model apportions offspring of individual mother plants to self-fertilization, outcrossing to males within a circumscribed area around the mother plant (the neighbourhood), and outcrossing to males outside the neighbourhood. Formerly the model was applied only to haploid pollen gametes in the offspring of conifers, but is extended so that it can be used with genotypic data from diploid offspring of both angiosperms and gymnosperms. In addition, it is shown that the mating parameters can be estimated without independent estimates of allele frequencies in the pollen pools outside the neighbourhood; thus the model might be applied effectively to natural populations exposed to unknown external pollen sources. Parameters of the neighbourhood mating model were estimated for a 10-year-old seed orchard population of the insect-pollinated tree, Eucalyptus regnans, in southeast Australia, which contained a mixture of two geographical provenances (Victoria and Tasmania). The mating patterns revealed were complex. Crosses between trees of the same provenance occurred three times more often than crosses between trees of different provenances. Levels of self-fertilization and patterns of mating within neighbourhoods were influenced by provenance origin, crop fecundity and orchard position (central vs. edge) of mother trees. Gene dispersal, however, was extensive, with approximately 50% of effective pollen gametes coming from males more than 40 m away from mother trees (average distance between neighbouring trees was 7.4 m). Thus, insect pollinators are efficient promoters of cross-fertilization in this orchard, with the result that the effective number of males mating with each female is large.

Comparison of pollen gene flow among four European beech (Fagus sylvatica L.) populations characterized by different management regimes

“…Paternity analysis was conducted by using both a maximum likelihood approach (Gerber et al, 2000) and a mating model approach (Burczyk et al, 2002). The maximum likelihood approach is aimed at assigning paternity to each analysed seed and allows one to estimate individual reproductive success of local adults, whereas by the mating model approach dispersal parameters and selection gradients at the population level (and their confidence intervals) are jointly estimated.…”

“…The mating model paternity analysis was performed by using the neighbourhood model, originally introduced by Adams and Birkes (1991) and extended by Burczyk et al (2002), implemented in the program NM+ (Chybicki and Burczyk, 2010a). The program allows estimating parameters of the neighbourhood model taking into account the estimated null allele frequencies for each scored locus.…”

“…To overcome methodological uncertainties related to different gene flow pattern analyses, we used two different approaches among the most common in dispersal studies on plants (Gerber et al, 2000;Burczyk et al, 2002;Bacles et al, 2006). In both approaches we employed recently developed techniques to take into account and correct possible genotyping errors that can inflate gene flow rates (Bacles and Ennos, 2008;Chybicki and Burczyk, 2010a).…”

Size advantage for male function and size‐dependent sex allocation in Ambrosia artemisiifolia, a wind‐pollinated plant

“…We selected sets of seeds and parents genotyped at least for five of the six loci. For paternity analysis, we employed the program NM+ v. 1.1 (Chybicki & Burczyk, 2010, 2012) instead of MEMM (Klein, Desassis, & Oddou‐Muratorio, 2008) because the former enables us to estimate not only pollen dispersal kernel but also selection gradients on MRS in which we can evaluate relative contribution of height and MRI; we applied a neighborhood model (Burczyk, Adams, Moran, & Griffin, 2002) implemented in the program NM+ to 2,102 seeds which were genotyped. On the other hand, NM+ does not estimate individual reproductive success and we need to examine how it could vary with the effects of the spatial position of individual plants in the experimental population.…”

The effects of inbreeding, genetic dissimilarity and phenotype on male reproductive success in a dioecious plant

“…As in previous work [22,56,63], we assumed that the fecundities for qualitative and quantitative traits were multiplicative; i.e. that the fecundity of a male individual m with phenotypic value z mi at trait i and z mj at trait j was f i (z mi ) f j (z mj ).…”