DOI: 10.5061/dryad.sf7m0cgj5
title: Latitudinal trends in genetic diversity and distinctiveness of Quercus robur rear edge forest remnants call for new conservation priorities

description: Knowledge of the spatial distribution of intraspecific genetic variation
 is essential for planning conservation actions, designing networks of
 protected areas, and informing possible assisted migration strategies.
 Although the Italian peninsula harbours unique genetic variation as a
 legacy of Quaternary migrations, only sporadic genetic information is
 available for forest tree species. Here, we present the first
 geographically comprehensive genetic characterisation of Quercus
 robur, an iconic broadleaved species of European floodplain forests, in an
 area which acted as a primary glacial refugium for the species. 745
 individuals from 25 populations were sampled and genotyped with 16
 microsatellite markers. Their genetic structure was assessed through
 various metrics of diversity and distinctiveness, as well as by Bayesian
 clustering and multivariate methods. The demographic history of inferred
 gene pools was evaluated through Approximate Bayesian Computation
 analysis. Genetic distinctiveness showed a decline with increasing
 latitude, while allelic richness reached its peak in central Italy. A
 south-to-north trend in the complexity of the genetic structure was
 observed, with peninsular Italy being characterised by intermingled gene
 pools in contrast to the relative homogeneity exhibited by northern
 populations. Demographic inference indicated that the southern gene pool
 has been genetically isolated since the penultimate interglacial, whereas
 populations from central Italy persisted locally in a mosaic of small
 refugia during the last glaciation. Our results brought out the
 complexity of the genetic structure of forest trees’ populations in
 southern Europe. At least three Q. robur refugia contributed to the
 genetic layout of extant populations after the last glacial period, but
 refugial areas were probably even more numerous in central Italy. Such a
 detailed characterization sheds new light on the priorities to be
 established for the conservation of highly fragmented Q. robur populations
 in an area rich in diversified genetic lineages.
description: # Latitudinal trends in genetic diversity and distinctiveness of Quercus
 robur rear edge forest remnants call for new conservation priorities
 Dataset DOI: [10.5061/dryad.sf7m0cgj5](10.5061/dryad.sf7m0cgj5) ##
 Description of the data and file structure ### Files and variables File:
 Avanzi\_et\_al\_DATA\_Quercus\_robur\_25pop\_729ind.xlsx Genetic data of
 745 *Quercus robur* individuals from 25 populations sampled throughout
 Italy, characterized with a set of 16 nuclear microsatellite markers
 (PIE020, PIE223, PIE242, PIE102, PIE239, PIE227, PIE271, PIE267, PIE215,
 QrZAG7, MsQ13, QrZAG112, QrZAG20, QpZAG15, QpZAG110, QrZAG96).  The
 genotypes of 46 *Quercus petraea*, 26 *Quercus pubescens* and 8 *Quercus
 frainetto* individuals are also provided (Sheet 1). These additional
 genotypes were used in a Bayesian clustering analysis performed with
 STRUCTURE to exclude the presence of individuals ‘misclassified’ as *Q.
 robur*, which would bias estimates of genetic diversity and structure.
 Based on this analysis, 16 trees were identified as ‘misclassified’ and
 excluded from the final dataset, consisting of 729 individuals (Sheet 2).
 All details are available in the paper.