Strong gene flow undermines local adaptations in a host parasite system

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Seppä , P , Bonelli , M , Dupont , S , Hakala , S M , Bagnères , A-G & Lorenzi , M C 2020 , ' Strong gene flow undermines local adaptations in a host parasite system ' , Insects , vol. 11 , no. 9 , 585 . https://doi.org/10.3390/insects11090585

Title: Strong gene flow undermines local adaptations in a host parasite system
Author: Seppä, Perttu; Bonelli, Mariaelena; Dupont, Simon; Hakala, Sanja Maria; Bagnères, Anne-Geneviève; Lorenzi, M. Cristina
Contributor: University of Helsinki, Evolution, Sociality & Behaviour
University of Helsinki, Organismal and Evolutionary Biology Research Programme
Date: 2020-09-01
Language: eng
Number of pages: 19
Belongs to series: Insects
ISSN: 2075-4450
URI: http://hdl.handle.net/10138/319859
Abstract: Simple Summary The co-evolution of hosts and parasites depends on their ability to adapt to each other's defense and counter-defense mechanisms. The strength of selection on those mechanisms may vary among populations, resulting in a geographical mosaic of co-evolution. The boreo-montane paper wasp Polistes biglumis and its parasite Polistes atrimandibularis exemplify this type of co-evolutionary system. Here, we used genetic markers to examine the genetic population structures of these wasps in the western Alps. We found that both host and parasite populations displayed similar levels of genetic variation. In the host species, populations located near to each other were genetically similar; in both the host and the parasite species populations farther apart were significantly different. Thus, apparent dispersal barriers (i.e., high mountains) did not seem to restrict gene flow across populations as expected. Furthermore, there were no major differences in gene flow between the two species, perhaps because P. atrimandibularis parasitizes both alpine and lowland host species and annually migrates between alpine and lowland populations. The presence of strong gene flow in a system where local populations experience variable levels of selection pressure challenges the classical hypothesis that restricted gene flow is required for local adaptations to evolve. The co-evolutionary pathways followed by hosts and parasites strongly depend on the adaptive potential of antagonists and its underlying genetic architecture. Geographically structured populations of interacting species often experience local differences in the strength of reciprocal selection pressures, which can result in a geographic mosaic of co-evolution. One example of such a system is the boreo-montane social wasp Polistes biglumis and its social parasite Polistes atrimandibularis, which have evolved local defense and counter-defense mechanisms to match their antagonist. In this work, we study spatial genetic structure of P. biglumis and P. atrimandibularis populations at local and regional scales in the Alps, by using nuclear markers (DNA microsatellites, AFLP) and mitochondrial sequences. Both the host and the parasite populations harbored similar amounts of genetic variation. Host populations were not genetically structured at the local scale, but geographic regions were significantly differentiated from each other in both the host and the parasite in all markers. The net dispersal inferred from genetic differentiation was similar in the host and the parasite, which may be due to the annual migration pattern of the parasites between alpine and lowland populations. Thus, the apparent dispersal barriers (i.e., high mountains) do not restrict gene flow as expected and there are no important gene flow differences between the species, which contradict the hypothesis that restricted gene flow is required for local adaptations to evolve.
Subject: 1181 Ecology, evolutionary biology
AFLP
Dispersal
DNA microsatellites
Gene flow
Genetic diversity
Local adaptations
mtDNA
Polistes
Social parasitism
Spatial genetic structure
AFLP
dispersal
DNA microsatellites
gene flow
genetic diversity
local adaptations
mtDNA
Polistes
social parasitism
spatial genetic structure
POLISTES-BIGLUMIS-BIMACULATUS
SOCIAL PARASITE
POPULATION-STRUCTURE
PAPER WASP
ATRIMANDIBULARIS HYMENOPTERA
SEQUENCE ALIGNMENT
DNA
COEVOLUTION
VESPIDAE
ANT
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