Intrapopulation fixation index dynamics in finite populations with variable outcrossing rates

Abstract

The intrapopulation fixation index ( f ) is inversely related to the outcrossing rate (t). Results obtained from data on molecular markers of natural populations have shown that these values are highly variable, even when measured in the same group of individuals. It is thus suggested that factors besides those described in Wright's genetic equilibrium must be operating. Using simulated data sets this study shows that the finite size condition of a population is sufficient to spread the estimated f values along a range at equilibrium, as opposed to keeping them at the theoretical equilibrium point. The variation in outcrossing rates can amplify this range considerably. Correlation between estimated f values obtained from different loci in this condition showed to be negatively related to the outcrossing rates, and positively related to the variance of these rates along generations. The finite size of populations associated to small fluctuations in t mean values over time may explain the usually reported high variation among estimated f values of different loci.

Mixed-Mating Model of Reproduction Revealed in European Phytophthora cactorum by ddRADseq and Effector Gene Sequence Data

“…The reproduction mode is also traceable by means of the values of F-statistics; if only selfing occurs in the population, the heterozygosity decreases to close to zero over several generations [77], and the fixation index (F st ) among populations increases to 1 [22]. Outbreeding decreases both the fixation (F st ) and inbreeding (F is ) indices [78]. In heterothallic P. andina, inbreeding coefficient F is values between −0.13 and −0.07 were considered to be associated with outbreeding, or an isolation-breaking effect, which is congruent with the low revealed rate of clones in those populations [79], similar conclusions were made by other authors in other species [50,51].…”

Fine-scale genetic structure overrides macro-scale structure in a marine snail: nonrandom recruitment, demographic events or selection?

“…Heterogeneous values of the F IS index could also be strongly influenced by small population sizes. This, associated with outcrossing rates smaller than a unity, might result in variable F IS > 0 values in different loci within a sample (Coelho & Vencovsky, 2003). Thus, if our samples indeed represent small and not totally panmitic populations, it is possible that the observed heterogeneity within samples is an outcome of the finite conditions of natural L. flava populations.…”

Seeing the forest through the trees: comprehensive inference on individual mating patterns in a mixed stand of Quercus robur and Q. petraea

“…Individual variation may have significant implications for a population and for the entire species. For example, individual variation in self-fertilization can lead to unpredictable oscillations in inbreeding rates (Coelho and Vencovsky, 2003) and thus may be a basis for stronger ( positive or negative) inbreeding effects than predicted by simple models. Therefore, identifying individual mating parameters is a first step towards understanding the diversity of mating system variation.…”