Reconstructing the demographic history of populations is a central issue in evolutionary biology. Using likelihood-based methods coupled with Monte Carlo simulations, it is now possible to reconstruct past changes in population size from genetic data. Using simulated data sets under various demographic scenarios, we evaluate the statistical performance of Msvar, a full-likelihood Bayesian method that infers past demographic change from microsatellite data. Our simulation tests show that Msvar is very efficient at detecting population declines and expansions, provided the event is neither too weak nor too recent. We further show that Msvar outperforms two moment-based methods (the M-ratio test and Bottleneck) for detecting population size changes, whatever the time and the severity of the event. The same trend emerges from a compilation of empirical studies. The latest version of Msvar provides estimates of the current and the ancestral population size and the time since the population started changing in size. We show that, in the absence of prior knowledge, Msvar provides little information on the mutation rate, which results in biased estimates and/or wide credibility intervals for each of the demographic parameters. However, scaling the population size parameters with the mutation rate and scaling the time with current population size, as coalescent theory requires, significantly improves the quality of the estimates for contraction but not for expansion scenarios. Finally, our results suggest that Msvar is robust to moderate departures from a strict stepwise mutation model.

The fine-scale pattern of correlated paternity was characterized within a population of the narrow-endemic model plant species, Centaurea corymbosa, using microsatellites and natural progeny arrays. We used classical approaches to assess correlated mating within sibships and developed a new method based on pairwise kinship coefficients to assess correlated paternity within and among sibships in a spatio-temporal perspective. We also performed numerical simulations to assess the relative significance of different mechanisms promoting correlated paternity and to compare the statistical properties of different estimators of correlated paternity. Our new approach proved very informative to assess which factors contributed most to correlated paternity and presented good statistical properties. Within progeny arrays, we found that about one-fifth of offspring pairs were full-sibs. This level of correlated mating did not result from correlated pollen dispersal events (i.e., pollen codispersion) but rather from limited mate availability, the latter being due to limited pollen dispersal distances, the heterogeneity of pollen production among plants, phenological heterogeneity and, according to simulations, the self-incompatibility system. We point out the close connection between correlated paternity and the "TwoGener" approach recently developed to infer pollen dispersal and discuss the conditions to be met when applying the latter.C ORRELATED paternity refers to the fact that dif-or embryo abortion, as well as resource allocation to each sex (Charnov 1982). Under limited seed dispersal, ferent offspring may be sired by the same father.where interacting individuals are likely sibs, it may also Within maternal progeny arrays it is often referred to act on the type of competitive interactions involved (e.g., as "correlated mating" and can be expressed by the kin selection; Hamilton 1964; Schuster and Mitton fraction of full-sib pairs (e.g., Ritland 1989; El-Kassaby 1991; Rousset and Billiard 2000), the average fitness and Jaquish 1996) or by the number of different fathers of competing siblings (Young 1981; Schmitt and Ehrinvolved (e.g., Campbell 1998). In this context, pure hardt 1987; Karron and Marshall 1990, 1993), or half-sib and pure full-sib families represent the extreme the success of mating events between nearby individuals alternatives of a continuum from uncorrelated to totally when inbreeding depression or self-incompatibility occorrelated mating events (e.g., polyads of mimosoid lecurs. Second, together with the outcrossing rate, the gumes and tropical figs; Nason et al. 1998). Correlated pattern of correlated mating is a key parameter of the paternity can also be considered between maternal mating system (Ritland 1988 and can provide progeny arrays, where it can be expressed by the relative valuable information on pollination biology because it proportions of (paternal) half-sibs and non-sibs.depends on a set of biological factors related in particuIn plant populations, correlated paternity is impor...