Revealing the consequences of malebiased trophy h

Authors: Rolando RodríguezMuñoz Carlos Rodríguez del Valle María José Bañuelos Patricia Mirol

Publish Date: 2015/06/30

Volume: 16, Issue: 6, Pages: 1375-1394

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Abstract

Demographic models accounting for operational sex ratio OSR show that male numbers can have a substantial influence on the dynamics of wild populations We used the Cantabrian capercaillie a forest bird as a model to assess the effects of the reduction in the number of breeding males increased OSR associated to malebiased hunting on the genetics of the population We based our assessment in the comparison of the dynamics of neutral markers transmitted by both parents microsatellites versus markers transmitted only by females mitochondrial DNA—mtDNA Parallel to the analysis of field data we ran computer simulations to explore how different levels of OSR and two other important demographic factors population size and connectivity might influence the dynamics of genetic variation of microsatellites and mtDNA We found evidence of a genetic bottleneck and low genetic variability affecting microsatellites but not mtDNA early in our study period when malebiased hunting was more intense This was followed by a decline in mtDNA variation around 10–20 years later Simulations suggested that changes in genetic variation associated with high OSR had the closest similarity to those observed at the beginning of our study whereas a combination of reduced size and migration rate better resembled the patterns found later on Our findings indicate that malebiased hunting might have triggered the ongoing decline of the Cantabrian capercaillie on its own or in combination with habitat configuration and support the need to incorporate OSR into decision making for the management and conservation of exploited populationsWe are very grateful to K Pérez D Ramos JR Jiménez E González E de la Calzada an anonymous taxidermist and several hunters and small public and private collections for providing access to many of the preserved birds and old feather samples Many people collaborated in the collection of shed feathers we are especially grateful to the Environmental Administration of Asturias and their rangers as well as B Blanco A Fernández M González M Quevedo and L Robles J Cabot helped us with the specimens from the Estación Biológica de Doñana and J Barrerio with those from the Museo de Ciencias Naturales de Madrid Thanks also to the people of the Museo de Ciencias de Santiago de Compostela to JC Illera who made possible all Mac based analyses and to M Quevedo who made useful comments on the final version of the manuscript This work has been supported by the Natural Environment Research Council Grant 244 NE/E005403/1 FICYT IB08158 and POST1041 MICINN CGL201015990 and Agencia Nacional de Promoción Científica y Tecnológica PME 2151Starting around 3000 years ago the Cantabrian Mountains have undergone intensive human driven deforestation and forest fragmentation Muñoz Sobrino et al 1997 a process that intensified over the last 1000 years Woodlands lost and fragmentation are prevalent factors associated to the decline of forest fauna by reducing population size and connectivity Allendorf and Luikart 2007 Therefore together with male hunting habitat loss and fragmentation are potential factors that could explain the ongoing population decline in this area leading to a reduction in effective male and female population size and/or a reduction in population connectivity We used Easypop 201 Balloux 2001 to model the dynamics of number of haplotypes H haplotype diversity h number of alleles Ao expected and observed heterozygosity He and Ho and inbreeding coefficient F IS under various levels of 1 population size 2 population fragmentation ie variation in genetic flow by using migration rate as a proxy and 3 operational sex ratio We did not intend to accurately recreate the patterns of genetic variation that we found in the field through time but to get some insights on how different levels of each of the three parameters could influence genetic variation in mitochondrial versus nuclear DNAAlthough our aim is to get insights about what would be the most plausible explanation for the genetic patterns found in the field for the Cantabrian capercaillie our hypotheses should apply to a more general context Thus we hypothesize that in any similar species in terms of social structure and reproductive system a decrease in the number of reproductive males would reduce microsatellite variability but had limited or no effect on mtDNA variation conversely any factor reducing both the number of reproductive females and males overall drop in population size should result in a sharper drop in mtDNA than microsatellite variation A severe limitation in connectivity as a result of habitat loss and fragmentation would also have limited or no effect in mtDNA but would lead to a more inbred population when compared to the effects of a decrease in the number of reproductive malesThere is a possibility that the simulation results obtained for our study population are constrained in some way due to the use of genetic parameters coming from a declining population In order to check the generality of our hypotheses we have also explored these alternative scenarios for the black grouse Tetrao tetrix a polygynous lekking bird and a close relative of capercaillie To run the simulations we used demographic parameters extracted from the available literature on the large black grouse populations of Scandinavia We did not aim to develop a detailed demographic model but to explore how different levels of population size population connectivity or operational sexratio OSR might affect nuclear verus mitochondrial genetic variation in a demographically healthy population of a lekking birdAll the simulations are based in a metapopulation made by 16 identical populations The setting of most of the genetic and demographic parameters required by Easypop are shared by all the simulations regardless of what factor is being modeled These “fixed” parameters include the proportion of copulations by subordinate males the migration model the number of loci the mutation scheme rate and model and the number of possible allelic states All other parameters varied according to the factor being modeledDiagram representing the twodimension stepping stone migration model used in Easypop Each black dot represents a lek Leks are grouped in batches of 3–4 encircled that correspond to the populations in the simulation Migration rates correspond to movements among circles each circle being connected to the four closest circles around it with the exception of the borders where circles are connected to two circles at the corners or three circles at the sides other circles

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