DOI: 10.5061/dryad.h70rxwdkf
title: Data from: Context matters: the landscape matrix determines the population genetic structure of temperate forest herbs across Europe

description: Context. Plant populations in agricultural landscapes are mostly
 fragmented and their functional connectivity often depends on seed and
 pollen dispersal by animals. However, little is known about how the
 interactions of seed and pollen dispersers with the agricultural matrix
 translate into gene flow among plant populations. Objectives. We aimed to
 identify effects of the landscape structure on the genetic diversity
 within, and the genetic differentiation among, spatially isolated
 populations of three temperate forest herbs. We asked, whether different
 arable crops have different effects, and whether the orientation of linear
 landscape elements relative to the gene dispersal direction matters.
 Methods. We analysed the species’ population genetic structures in seven
 agricultural landscapes across temperate Europe using microsatellite
 markers. These were modelled as a function of landscape composition and
 configuration, which we quantified in buffer zones around, and in
 rectangular landscape strips between, plant populations. Results.
 Landscape effects were diverse and often contrasting between species,
 reflecting their association with different pollen- or seed dispersal
 vectors. Differentiating crop types rather than lumping them together
 yielded higher proportions of explained variation. Some linear landscape
 elements had both a channelling and hampering effect on gene flow,
 depending on their orientation. Conclusions. Landscape structure is a more
 important determinant of the species’ population genetic structure than
 habitat loss and fragmentation per se. Landscape planning with the aim to
 enhance the functional connectivity among spatially isolated plant
 populations should consider that even species of the same ecological guild
 might show distinct responses to the landscape structure.
description: The data refer to 42, 34 and 36 populations of the forest herbs
 Anemone nemorosa, Oxalis acetosella and Polygonatum multiflorum,
 respectively, sampled in seven 5 x 5 km² landscape windows across Europe
 (North France, Belgium, West Germany, East Germany, South Sweden, Central
 Sweden,  Estonia). The location of each population is published in the
 related dataset https://doi.org/10.5061/dryad.tb2rbp00k .
 The dataset comprises <br> (a) pairwise
 genetic differentiation among populations within landscape
 windows The microsatellite allele data used to
 calculate pairwise genetic differentiation among populations are available
 and have been described in the related dataset
 https://doi.org/10.5061/dryad.tb2rbp00k . We used two measures of genetic
 differentiation,
 <em>G''</em><sub>ST</sub> (Meirmans
 & Hedrick 2011, Mol Ecol Resour 11(1):5-18) and
 <em>D</em><sub>PS</sub> (= 1 minus the proportion
 of shared alleles).   (b) landscape
 metrics calculated for buffer zones around each population
 We calculated a set of landscape metrics (see Table 1 of the
 original article) in buffer zones around each herb population. Several
 buffer distances were chosen to reflect range sizes and forage distances
 of potential seed and pollen dispersal vectors (Table 1 of the original
 article): 125 m, 250 m, 500 m, 1000 m and 2000 m. For each buffer zone, we
 calculated the percent cover of different area-based land-use types, the
 relative length of different linear landscape elements (= total length
 divided by buffer area) and two index measures, i.e. the Shannon diversity
 of land-use types and the density of all land-use patch edges (Table 1).
 Since the effect that a linear landscape element exerts on gene dispersal
 might depend on its orientation relative to the movement direction of
 vectors (orthogonal vs. parallel), we calculated also the orthogonal and
 parallel length component of each linear landscape element (see Figure 1c
 and d in the original article). In buffer zones, the parallel direction
 corresponds to the direction from the midpoint of the linear element to
 the population centre. The orthogonal-to-parallel length ratio was then
 used as conditioning variable in statistical models. Moreover, the effect
 of settlement areas on gene dispersal vectors might depend on the relative
 proportion of sealed or built-up area vs. unsealed green areas, such as
 gardens. The latter might serve as forage habitat for pollinators,
 particularly, when many fruit trees or ornamental shrubs can be found
 there. Therefore, we used also the proportion of green settlement area as
 conditioning variable in statistical models. <br>
 (c) landscape metrics calculated for landscape strips connecting
 populations. We calculated the same set of landscape
 metrics also for rectangular landscape strips connecting the centres of
 each pair of herb populations within landscape windows. We chose several
 width-to-length ratios for the landscape strips connecting the herb
 populations to account for the fact that different pollen and seed
 dispersal vectors have different sight distances for their orientation and
 thus will move more or less linearly through the landscape: 1:7, 1:5, 1:3,
 1:2 and 2:3. As for buffer zones, we also calculated the orthogonal and
 parallel length component of each linear landscape element. Here, the
 parallel direction corresponds to the connection line between population
 centres.
description: See the README file.