Host tracking or cryptic adaptation? Phylogeography ofPediobius saulius(Hymenoptera, Eulophidae), a parasitoid of the highly invasive horse‐chestnut leafminer

Abstract

Classical biological control is often advocated as a tool for managing invasive species. However, accurate evaluations of parasitoid species complexes and assessment of host specificity are impeded by the lack of morphological variation. Here, we study the possibility of host races/species within the eulophid wasp Pediobius saulius, a pupal generalist parasitoid that parasitize the highly invasive horse-chestnut leaf-mining moth Cameraria ohridella. We analysed the population genetic structure, host associations and phylogeographic patterns of P. saulius in Europe using the COI mitochondrial gene. This marker strongly supports a division into at least five highly differentiated parasitoid complexes, within two of which clades with differing degrees of host specialization were found: a Balkan clade that mainly (but not only) attacks C. ohridella and a more generalist European group that attacks many hosts, including C. ohridella. The divergence in COI (up to 7.6%) suggests the existence of cryptic species, although this is neither confirmed by nuclear divergence nor morphology. We do not find evidence of host tracking. The higher parasitism rates observed in the Balkans and the scarcity of the Balkan–Cameraria haplotypes out of the Balkans open the possibility of using these Balkan haplotypes as biological control agents of C. ohridella elsewhere in Europe.

The ‘generalism’ debate: misinterpreting the term in the empirical literature focusing on dietary breadth in insects

“…No doubt the continuing and more widespread application of high‐resolution DNA markers and other molecular techniques (sequencing, serological and chemical/biochemical) will reveal that many of the apparent polyphagous ‘generalists’ presently observed in nature are in fact morphologically similar/identical complexes of cryptic species (e.g. Atanassova et al ., ; Berenbaum, ; Xu et al ., ; Hernández‐López et al ., ; Tay et al ., ). Thus, ultimately specialism, the driving force in ecological and evolutionary divergence and the mechanism that leads to the units of biodiversity within the biosphere (Claridge et al ., ) dominates, often at a hitherto unimagined, extremely fine‐grained level, as some of the above examples clearly testify.…”

Molecular and cytogenetic differentiation within the Lariophagus distinguendus (Förster, 1841) species complex (Hymenoptera, Pteromalidae)

“…On the other hand, relatively strong differences in the structure of COI sequences between certain strains with the same karyotype do not necessarily indicate their species status (see e.g. Hernández-López et al 2012, Korenko et al 2018). Further molecular studies, which should also include nuclear markers for those strains that were not previously examined in this respect, are therefore needed (see König et al 2015).…”

An integrative study ofNecremnus Thomson (Hymenoptera: Eulophidae) associated with invasive pests in Europe and North America: taxonomic and ecological implications

“…If slight differences are misinterpreted as intraspecific variation, this can lead to the lumping of two or more species under a single taxonomic entity and the underestimation of true species diversity. Mounting evidence, mainly from the use of molecular data, is showing that some recognized morphospecies are in fact complexes of lineages that differ in critical behavioural and ecological features such as host range (Heraty et al ., 2007 ; Gebiola et al ., 2009 , 2012 ; Chesters et al ., 2012 ; Hernandez-Lopez et al ., 2012 ). Cryptic diversity is common amongst hymenopteran parasitoids, in which species confusion can have significant economic consequences because of their wide use as biological control agents.…”