From the Apennines to the Alps: colonization genetics of the naturally expanding Italian wolf (Canis lupus) population

Abstract

Wolves in Italy strongly declined in the past and were confined south of the Alps since the turn of the last century, reduced in the 1970s to approximately 100 individuals surviving in two fragmented subpopulations in the central-southern Apennines. The Italian wolves are presently expanding in the Apennines, and started to recolonize the western Alps in Italy, France and Switzerland about 16 years ago. In this study, we used a population genetic approach to elucidate some aspects of the wolf recolonization process. DNA extracted from 3068 tissue and scat samples collected in the Apennines (the source populations) and in the Alps (the colony), were genotyped at 12 microsatellite loci aiming to assess (i) the strength of the bottleneck and founder effects during the onset of colonization; (ii) the rates of gene flow between source and colony; and (iii) the minimum number of colonizers that are needed to explain the genetic variability observed in the colony. We identified a total of 435 distinct wolf genotypes, which showed that wolves in the Alps: (i) have significantly lower genetic diversity (heterozygosity, allelic richness, number of private alleles) than wolves in the Apennines; (ii) are genetically distinct using pairwise F(ST) values, population assignment test and Bayesian clustering; (iii) are not in genetic equilibrium (significant bottleneck test). Spatial autocorrelations are significant among samples separated up to c. 230 km, roughly correspondent to the apparent gap in permanent wolf presence between the Alps and north Apennines. The estimated number of first-generation migrants indicates that migration has been unidirectional and male-biased, from the Apennines to the Alps, and that wolves in southern Italy did not contribute to the Alpine population. These results suggest that: (i) the Alps were colonized by a few long-range migrating wolves originating in the north Apennine subpopulation; (ii) during the colonization process there has been a moderate bottleneck; and (iii) gene flow between sources and colonies was moderate (corresponding to 1.25-2.50 wolves per generation), despite high potential for dispersal. Bottleneck simulations showed that a total of c. 8-16 effective founders are needed to explain the genetic diversity observed in the Alps. Levels of genetic diversity in the expanding Alpine wolf population, and the permanence of genetic structuring, will depend on the future rates of gene flow among distinct wolf subpopulation fragments.

The genetic structure of the Lithuanian wolf population

“…All of these wolves were males which hunted in north-eastern and south-eastern Lithuania, and they carried rare haplotypes (W3-LT and W5-LT). Malebiased migration of wolves was also observed between the Alps and north Apennines [53]. The presence of immigrants might explain a linkage disequilibrium found in a few pairs of loci and slight deviation from HardyWeinberg equilibrium.…”

Fine-scale genetic structure suggests low levels of short-range gene flow in a wolf population of the Italian Apennines

“…Field data on radio-collared wolves show slight or no difference in dispersal patterns between sexes (Mech 1987;Gese and Mech 1991;Kojola et al 2006), whereas male-biased dispersal is suggested by genetic investigations carried out in North America and Europe (Lehman et al 1992;Seddon et al 2005;Fabbri et al 2007;Vonholdt et al 2008).…”

A genome-wide perspective on the evolutionary history of enigmatic wolf-like canids

“…4; Hewitt 1996). Italy and Spain were among the most divergent populations (Italy: mean F ST = 0.15, Spain: mean F ST = 0.11) (Supplemental Table S3C), which likely reflect historic Ice Age isolation as well as drift from recent population contractions (Randi and Lucchini 2002;Lucchini et al 2004;Fabbri et al 2007;Gray et al 2009). Other genetically distinct populations include Eastern and Northern Europe, China, the Middle East, and Southwest Asia (Fig.…”