Contribution of integrative taxonomy to tracking interspecific hybridisations between the biological control agent Torymus sinensis and its related taxa

Abstract

Native to China, the chestnut gall wasps Dryocosmus kuriphilus Yasumatsu (Hymenoptera, Cynipidae) has invaded several countries on three continents in about half a century. To reduce the negative impact on the chestnut industry, the hymenopteran parasitoid Torymus sinensis Kamijo (Hymenoptera, Torymidae) was firstly translocated from China to Japan and then from Japan to other countries. From an agronomic point of view, this classical biological control programme is perceived as a great success story even if in Japan it was overshadowed by evidence of hybridisation with the indigenous species Torymus beneficus Yasumatsu & Kamijo. Based on numerous specimens collected in France and Italy but also in Asia, as well as on published data, we detected molecular and phenotypic signatures of a possible hybridisation. Our results evidenced for the first time that the European stock of T. sinensis has some rare molecular signatures of historical hybridisation that took place in Japan (0.66% of the mitochondrial haplotypes). Our morphometric study also shows that European and Japanese T. sinensis are morphologically intermediate between the two species that hybridised. The identity of the early‐ and late‐season strains of T. beneficus is discussed. Torymus beneficus late‐season strain (TbL) is considered to be the same as T. sinensis and only the early‐season strain (TbE) is the true T. beneficus. Torymus beneficus is morphologically very close to T. sinensis, and the interspecific distance of COI, though large, is comparable with the larger intraspecific variability found in other Chalcidoidea species. Though the two could be regarded as subspecies, for the stability of nomenclature it is better to continue treating them as distinct species.

Genomics and ecological modelling clarify species integrity in a confusing group of butterflies

“…However, integration of additional information, such as ecological associations, not only helps to resolve evolutionary relationships among cryptic taxa but also provides insight into mechanisms that underlie their divergence (i.e., the ecological species concept; Andersson, 1990; Newton et al, 2020; Nosil, 2012; Rissler & Apodaca, 2007; Van Valen, 1976; Villegas et al, 2021). These approaches, making use of multiple types of data and analytical frameworks, are generally referred to as integrative species delimitation (Dayrat, 2005; Edwards & Knowles, 2014; Puillandre et al, 2012; Roe & Sperling, 2007; Schlick‐Steiner et al, 2010; Viciriuc et al, 2021). Operationally, integrative species delimitation is consistent with the widely‐applied General Lineage Concept, which acknowledges speciation to be a complex process that may be characterized using combinations of species criteria (de Queiroz, 1998, 2005, 2007).…”

“…These approaches, making use of multiple types of data and analytical frameworks, are generally referred to as integrative species delimitation (Dayrat, 2005;Edwards & Knowles, 2014;Puillandre et al, 2012;Roe & Sperling, 2007;Schlick-Steiner et al, 2010;Viciriuc et al, 2021). Operationally, integrative species delimitation is consistent with the widely-applied General Lineage Concept, which acknowledges speciation to be a complex process that may be characterized using combinations of species criteria (de Queiroz, 1998(de Queiroz, , 2005(de Queiroz, , 2007.…”