Author: Malgorzata Pilot

A new paper has been published in Molecular Ecology Resources:

Reliability assessment of null allele detection: inconsistencies between and within different methods
M. J. DABROWSKI , M. PILOT, M. KRUCZYK, M. ZMIHORSKI ,H. M. UMER and J . GLIWICZ

Abstract
Microsatellite loci are widely used in population genetic studies, but the presence of null alleles may lead to biased results. Here, we assessed five methods that indirectly detect null alleles and found large inconsistencies among them. Our analysis was based on 20 microsatellite loci genotyped in a natural population of Microtus oeconomus sampled during 8 years, together with 1200 simulated populations without null alleles, but experiencing bottlenecks of varying duration and intensity, and 120 simulated populations with known null alleles. In the natural population, 29% of positive results were consistent between the methods in pairwise comparisons, and in the simulated data set, this proportion was 14%. The positive results were also inconsistent between different years in the natural population. In the null-allele-free simulated data set, the number of false positives increased with increased bottleneck intensity and duration. We also found a low concordance in null allele detection between the original simulated populations and their 20% random subsets. In the populations simulated to include null alleles, between 22% and 42% of true null alleles remained undetected, which highlighted that detection errors are not restricted to false positives. None of the evaluated methods clearly outperformed the others when both false-positive and false-negative rates were considered. Accepting only the positive results consistent between at least two methods should considerably reduce the false-positive rate, but this approach may increase the false-negative rate. Our study demonstrates the need for novel null allele detection methods that could be reliably applied to natural populations.

A paper on genetic diversity in a moulting colony of southern elephant seals from King George Island, South Shetlands Archipelago, has been published in Marine Ecology Progress Series:

Genetic diversity in a moulting colony of southern elephant seals in comparison with breeding colonies

Wiesław Bogdanowicz, Małgorzata Pilot, Marta Gajewska, Ewa Suchecka, Mikołaj Golachowski

ABSTRACT: Southern elephant seals (Mirounga leonina) migrate seasonally between pelagic foraging areas in the Southern Ocean and breeding and moulting sites on subantarctic islands. Here we characterized genetic diversity of the elephant seal moulting colony from King George Island (KGI), South Shetlands Archipelago, in comparison with breeding colonies described in earlier studies. Although KGI serves as a breeding site, the numbers of elephant seals are three times higher during the moulting season, suggesting post-breeding immigration from other sites, or large number of individuals skipping breeding season every year. High haplotype diversity and high percentage of shared haplotypes is consistent with the hypothesis of immigration from other South Atlantic colonies, which is also supported by satellite tracking data from earlier studies. Estimates of effective population size at both mtDNA and microsatellite loci were unexpectedly high as compared with the census size of the KGI colony, suggesting that they were elevated due to the presence of immigrants. However, we detected few immigrants and no genetic structure in the KGI colony, which could result from the genetic similarity between KGI and other breeding colonies from the South Atlantic, but could also be an effect of insufficient sampling scheme. These results show the need for genetic monitoring of southern elephant seal colonies throughout their annual cycle to better understand the range of their seasonal movements and patterns of gene flow. The southern elephant seal serves as model to study links between spatio-temporal environmental variability, population dynamics, and individual movements, physiology, and reproductive behavior. Understanding the patterns of dispersal and gene flow in this species is essential to adequately address these general questions.