Strong Gene Flow Undermines Local Adaptations in a Host Parasite System

Abstract

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.

A geographic mosaic of coevolution between Eurosta solidaginis (Fitch) and its host plant tall goldenrod Solidago altissima (L.)

“…2007; Seppa et al. 2020), and its impact on geographic mosaics of coevolution has been experimentally demonstrated (Forde et al. 2004).…”

“…Mathematical models show that gene flow among hot spots and cold spots can significantly impact the distribution of coevolved traits (Nuismer et al 1999;Gomulkiewicz et al 2000;Fernandes et al 2019). Coevolution in the presence of gene flow has been demonstrated (Lively 1999;Burdon et al 2002;Martin-Galvez et al 2007;Seppa et al 2020), and its impact on geographic mosaics of coevolution has been experimentally demonstrated (Forde et al 2004). Gene flow can impact the structure of geographic mosaics of coevolution, influencing the distribution of traits of interacting species (Dybdahl and Lively 1996;Chaves-Campos et al 2011).…”

Chemically Insignificant Social Parasites Exhibit More Anti-Dehydration Behaviors than Their Hosts

“…Polistes biglumis is a non-parasitic, boreo-mountain species [74]. In the Alps, populations are small and geographically isolated (although gene flow occurs between close populations [75]). Colonies are founded by a single foundress in South-facing prairies on gentle mountain slopes at 1200-2000 m. a.s.l.…”

Lack of Evidence for Local Adaptation of the Endangered Karner Blue Butterfly to Its Sole Larval Hostplant—The Wild Lupine

“…In some cases, such as in salmon, it has led to divergent evolution in unrelated populations, likely as a result of the highly structured spatial organization of this economically valuable species [5]. In another case related to the host-parasite interaction between the paper wasp Polistes biglumis and its parasite Polistes atrimandibularis, physical barriers (mountains) did not impede gene flow despite different levels of selective forces operating at low and high altitudes resulting in a "geographic mosaic of co-evolution" [13]. Despite the substantial number of studies on local adaptation, information related to local adaptation in invertebrate specialist herbivores is still scarce; especially, on the role this process may have on the outcome of insect reintroduction programs in the wild.…”