Cryptic species complexes cause major challenges for taxonomists and alter understanding of species diversity. In Northern Europe, the Chrysis ignita species 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 of CO1, CO2, ATP8, ATP6, CO3, ND3, 16S and 12S rRNA, nine tRNAs and a partial sequence of CytB, as well as a 3880‐bp‐long sequence of the nuclear DNA covering a part of 18S rRNA, the ITS1, 5.8S rRNA, ITS2 and a part of 28S rRNA. Discrete diagnostic characters of each species sequence were retrieved using the Characteristic Attribute Organisation System algorithm and a molecular identification key was compiled. The study revealed a higher evolutionary rate of the genes ATP8, ATP6, CO3, ND3 and CytB compared to that of CO1, CO2 and 16S; the studied nuclear markers demonstrated a lower evolutionary rate than the mitochondrial markers. A consensus tree compiled based on the combined mtDNA and nuclear markers with a strongly supported topology resolved the position of the C. schencki – C. parietis sp.n. clade as sister to the C. ignita – C. impressa clade and supported the monophyly of the C. angustula – C. longula clade. We compiled a morphometric species identification key applying linear discriminant equations. The trophic differentiation was assessed using data on host preferences of ten Chrysis species 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, namely C. horridula sp.n. and C. parietis sp.n. Only C. mediata and C. solida were 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, the C. ignita complex 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.
Sex-specific patterns of individual growth, resulting in sexual size dimorphism (SSD), are a little studied aspect of the ontogeny related to the evolutionary history and affected by the ecology of a species. We used empirical data on the development of the predatory wasp Symmorphus allobrogus (Hymenoptera, Vespidae) to test the hypotheses that sexual differences of growth resulting in the female-biased SSD embrace the difference in (1) the egg size and the starting size of larva, (2) the larval development duration, and (3) the larval growth rate. We found that eggs developing into males and females have significant differences in size. There was no significant difference between the sexes in the duration of larval development. The relative growth rate and the food assimilation efficiency of female larvae were significantly higher than compared to those of male larvae. Thus, the SSD of S. allobrogus is mediated mainly by sexual differences in egg size and larval growth rate.
Two new species of Diodontus Curtis, 1834 (Hymenoptera: Pemphredonidae) are described. Diodontus polytylus Budrys new species is widespread in North Africa, from Libya and Chad to Morocco, as well as in southern Spain and Portugal. Diodontus guichardi Budrys new species was found in several localities in Morocco. The new species have small differences in their morphology; however, they can be easily separated using molecular characters. Comparison of 17 molecular markers has revealed that the highest evolutionary divergence is observed in mitochondrial gene ND6 and internal transcribed spacer ITS2. The variable regions of the nuclear rDNA genes 18S and 28S demonstrated the lowest evolutionary divergence; thus they were of the least use for species identification. The most coherent reconstruction of phylogeny, in comparison to other groups of markers, was obtained using exons of nuclear protein-coding genes. A provisional key to the species of D. minutus (Fabricius, 1793) species group of the Mediterranean Region is presented.
The application of trap-nests for the studies of cavity-nesting Hymenoptera eventually implies a need for immediate nest identification using its structure. Possible nest characters that may be potentially useful for the separation of closely related species are body size-dependent metrical parameters of brood cells. We studied the dependence of brood cell length on nesting cavity width in ten cavitynesting predatory wasp species. Five hypotheses were tested. We calculated the derived parameters of brood cells needed for testing the hypotheses and, applying correlation and linear regression, assessed the degree of fit of the actual data to the hypothesized dependences. In three studied wasp species, the dependences of cell length on nesting cavity width in the datasets of cells with the brood of different sex supported different hypotheses. The results of the study demonstrate that species-specific metrical differences between related species, if present, are likely to be found in the length and width of a cell, but not in its volume.
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