DOI: 10.5061/dryad.j6q573nb5
title: Secondary contact zones of closely-related Erebia butterflies overlap with narrow phenotypic and parasitic clines

description: Zones of secondary contact between closely related taxa are a common
 legacy of the Quaternary ice ages. Despite their abundance, the factors
 that keep species apart and prevent hybridisation are often unknown. Here
 we study a very narrow contact zone between three closely related
 butterfly species of the Erebia tyndarus species complex. Using genomic
 data, we first determined if gene flow occurs and then assessed whether it
 might be hampered by differences in chromosome number between some
 species. We found interspecific gene flow between sibling species that
 differ in karyotype by one chromosome. Conversely, only F1 hybrids
 occurred between two species that have the same karyotype, forming a steep
 genomic cline. In a second step, we fitted clines to phenotypic,
 ecological and parasitic data to identify the factors associated with the
 genetic cline. We found clines for phenotypic data and the prevalence of
 the endosymbiont parasite Wolbachia to overlap with the genetic cline,
 suggesting that they might be drivers for separating the two species.
 Overall our results highlight that some gene flow is possible between
 closely-related species despite different chromosome numbers, but that
 other barriers restrict such gene flow.
description: The Morphology.txt file contains the Procrustes coordinates from
 19 landmarks that were set across the right forewing of Erebia butterflies
 (for each landmark the respective x and y coordinates are indicated). For
 a visual depiction of the landmarks please see Figure S1 of the study. For
 each specimen its ID, species, collection date, latitude (°N), longitude
 (°E) and sex are indicated. The Niche.txt contains the
 ecological data for each specimen that were used for the multivariate
 niche reconstruction.<br> For each specimen its ID, species,
 collection date, latitude (°N), longitude (°E) and sex are indicated.
 Additional variables are:<br> clou7          monthly mean cloudines
 July<br> clou8          monthly mean cloudines August<br>
 clou9          monthly mean cloudines September<br> mind7        
  monthly moisture index July<br> mind8          monthly moisture
 index August<br> mind9          monthly moisture index
 September<br> prec7          monthly mean precipitation
 July<br> prec8          monthly mean precipitation August<br>
 prec9          monthly mean precipitation September<br> tave7    
      monthly mean of average temperature July<br> tave8        
  monthly mean of average temperature August<br> tave9        
  monthly mean of average temperature September<br> ddeg      
  annual degreedays with 3°C threshold<br> slope_25     
  slope<br> tmax_sum25     maximum temperature in Summer<br>
 tmax_wint25    maximum temperature in Winter<br> tmin_fall25  
  minimal temperature in Fall<br> tmin_spr25     minimal temperature
 in Spring<br> swb            annual average site water
 balance<br> sfroyy         annual average # of frost days during
 growing season<br> pday           # of precipitation days per
 growing season