Sexual Asymmetry based on Flowering Assessment in a Clonal Seed Orchard of Pinus densiflora

Abstract

Two equations were formulated in order to estimate the degree of sexual asymmetry for monoecious species. The concepts of the equations were formulated on the basis of the effective population numbers of female and male parents [i.e, As(v)], and the differences of relative frequency between genders [i.e., As(x)]. These equations were applied to estimate the degree of sexual asymmetry based on the empirical data of flowering assessment in a clonal seed orchard of Pinus densiflora. The yearly variation in the production of female and male strobili was found. The effective population numbers at gamete levels (vfand vm) and clone level (vb) varied among 8 observation years. Both As(x)and As(v)were negatively correlated with effective numbers at gamete and clone levels. Averages of female and male strobilus production and estimates of sexual asymmetry were negatively correlated but the correlation was not significant. The correlations among effective number of clone (vb), arithmetic mean of female and male effective numbers (va) and estimate of sexual asymmetry [As(x)] were strong and significant. Relatively larger difference between vb and va were found when higher level of sexual asymmetry were observed.

Genetic worth and diversity across 18 years in a Nordmann fir clonal seed orchard

“…A phenotypic correlation between clonal means of accumulated female and male strobili production was absent, leaving room for some sexual asymmetry, as found for pines (Kang and Lindgren 1998), but in contradiction to findings for Picea abies (Kjaer 1996;Kjaer and Wellendorf 1997). Choi et al (2004) estimated the sexual asymmetry for Pinus densiflora across 8 years to be 0.176, a little lower than the 0.218 we found. In our study, broad-sense heritability for male and female strobili production averaged 0.22 and 0.24, respectively, based on actual numbers.…”

“…Ninety-two percent of the accumulated cone crop was produced in 10 out of 18 years (∼56%), which was less than that reported by Choi et al (2004), who found that 6 of 8 years (∼75%) produced 90% of the cone crop in P. densiflora. Our findings were very similar to the results from orchard studies including early harvest years: Kroon et al (2009) found, based on years with seed, that 10 of the 15 seed harvest years (∼67%) produced 90% of the seed crop in P. sylvestris, but when the years with no seed were included, this implied that only 10 out of 30 years (∼33%) gave 90% of the total cone crop.…”

“…The clones' relative contributions of male and female gametes, respectively, were described by a ratio for each clone as c i /p i. Furthermore, this sexual asymmetry was quantified using the differences in relative frequency between sexes: the absolute value of (c i −p i )/2 and the accumulated asymmetry for the orchard clones was estimated as A s (x) =0.5∑│(c i −p i )│ summed across all clones, according to Choi et al (2004), with the larger values representing the more pronounced differences between the respective male and female strobili production.…”

“…As stated by Kroon et al (2009), rather few studies have followed clone differences in flowering abundance over longer periods of time (e.g. Eriksson et al 1973 (6 years); ElKassaby et al 1989 (8 years)) and, to the authors' knowledge, none for the genus Abies, and in general very few time series include both male and female strobili registrations (Schmidtling 1983;Nikkanen and Ruotsalainen 2000;Choi et al 2004). …”

Sexual Symmetry in Natural Populations of the Patagonian Cypress (Austrocedrus chilensis)

“…When studying the performance of seed orchards of monoecious species, it is particularly useful to reduce the definition of sexual symmetry to 'equal contribution of gametes through pollen and ovules ' (CHOI et al, 2004). However, under a broader sense, sexual symmetry in a population is defined as equal allelic frequencies among the reproduction effective gametes of both sexes, the term "effective" referring to those gametes that managed to merge into new zygotes forming viable seeds, also called 'successful gametes'.…”