Sibling species in theChrysis ignitacomplex: molecular, morphological and trophic differentiation ofBaltic species, with a description of two new cryptic species (Hymenoptera:Chrysididae)

Abstract

AbstractCryptic species complexes cause major challenges for taxonomists and alter understanding of species diversity. InNorthernEurope, theChrysis ignitaspecies group is one such complex with numerous sympatric sibling species. The objective of this paper is to assess the taxonomy of 15 species from this group using three different approaches: molecular, morphological and trophic differentiation. The analysed set of molecular markers included a 7400‐bp‐long sequence of the mitochondrial genome covering complete sequences ofCO1,CO2,ATP8,ATP6,CO3,ND3,16Sand12SrRNA, ninetRNAsand a partial sequence ofCytB, as well as a 3880‐bp‐long sequence of the nuclearDNAcovering a part of18SrRNA, theITS1,5.8SrRNA,ITS2and a part of28SrRNA. Discrete diagnostic characters of each species sequence were retrieved using theCharacteristicAttributeOrganisationSystem algorithm and a molecular identification key was compiled. The study revealed a higher evolutionary rate of the genesATP8,ATP6,CO3,ND3andCytBcompared to that ofCO1,CO2and16S; the studied nuclear markers demonstrated a lower evolutionary rate than the mitochondrial markers. A consensus tree compiled based on the combinedmtDNAand nuclear markers with a strongly supported topology resolved the position of theC. schencki – C.parietissp.n.clade as sister to theC. ignita – C. impressaclade and supported the monophyly of theC. angustula – C. longulaclade. We compiled a morphometric species identification key applying linear discriminant equations. The trophic differentiation was assessed using data on host preferences of tenChrysisspecies reared from trap‐nests; the analysis demonstrated that most of them are specialists exploiting a single or a few taxonomically related host species. In most cases, all three approaches supported the distinct status of the included species. Moreover, two previously undescribed species were consistently supported by the molecular methods. Therefore, we describe these as new, namelyC. horridulasp.n.andC. parietissp.n.OnlyC. mediataandC. solidawere not clearly distinguished using the molecular phylogeny reconstruction methods. However, based on distinctive niche divergence, the presence of molecular characters and morphometric differences, we consider them as phylogenetically young but distinct species. In view of the weak morphological and molecular differentiation, the widely overlapping distribution areas and often similar habitat preferences and the trophic specialization, theC. ignitacomplex presents a possible model for studies of sympatric cryptic speciation.This published work has been registered in ZooBank,http://zoobank.org/urn:lsid:zoobank.org:pub:1EBAF0E1‐5FB7‐4CF4‐A595‐C11982448360.