Does early learning drive ecological divergence during speciation processes in parasitoid wasps?

Abstract

Central to the concept of ecological speciation is the evolution of ecotypes, i.e. groups of individuals occupying different ecological niches. However, the mechanisms behind the first step of separation, the switch of individuals into new niches, are unclear. One long-standing hypothesis, which was proposed for insects but never tested, is that early learning causes new ecological preferences, leading to a switch into a new niche within one generation. Here, we show that a host switch occurred within a parasitoid wasp, which is associated with the ability for early learning and the splitting into separate lineages during speciation. Lariophagus distinguendus consists of two genetically distinct lineages, most likely representing different species. One attacks drugstore beetle larvae (Stegobium paniceum (L.)), which were probably the ancestral host of both lineages. The drugstore beetle lineage has an innate host preference that cannot be altered by experience. In contrast, the second lineage is found on Sitophilus weevils as hosts and changes its preference by early learning. We conclude that a host switch has occurred in the ancestor of the second lineage, which must have been enabled by early learning. Because early learning is widespread in insects, it might have facilitated ecological divergence and associated speciation in this hyperdiverse group.

Lariophagus distinguendus (Hymenoptera: Pteromalidae) (Förster)—Past, Present, and Future: The History of a Biological Control Method Using L. distinguendus against Different Storage Pests

“…After the appointment of Steidle as the head of the Department of Animal Ecology at Hohenheim University, Germany, another center of L. distinguendus research was established. Steidle focused on basic research about the mechanisms of speciation with a focus on early learning and courtship behavior, using L. distinguendus as a model system [66]. It could be shown that the species L. distinguendus de facto consists of two species.…”

“…It could be shown that the species L. distinguendus de facto consists of two species. While one of these two species is a generalist on many different hosts, the other apparently has a narrower host range and is unwilling to parasitize S. granarius , a fact that could have a huge impact on the application [66]. Furthermore, Steidle picked up earlier applied work looking at the dispersal ability of L. distinguendus , this time studying the dispersal of the wasps outside the commodity, applied as an empty storage treatment against residual pest populations [67].…”

“…(4) L. distinguendus strains should be selected in accordance to the pest species against which they are applied [66]. Especially strains originating from the host S. paniceum might be specialized on that host and are thus inefficient against other hosts [66].…”

“…Especially strains originating from the host S. paniceum might be specialized on that host and are thus inefficient against other hosts [66]. …”

Systematics and biological control

“…Consequently, knowledge of phylogenetic relatedness can be used to predict the host range of a biological control agent or target pest (Sheppard et al, 2005). However, predicting potential host ranges should not be based solely on phylogenetic relationships because numerous ecological (Hoffmeister, 1992;Stireman and Singer, 2003) and behavioral (König et al, 2015) factors also influence host associations. When explicit phylogenies are unavailable, biological classifications can be harnessed to select sets of species appropriate for testing.…”