Improved chromosome-level genome assembly of the Glanville fritillary butterfly (Melitaea cinxia) integrating Pacific Biosciences long reads and a high-density linkage map

Background The Glanville fritillary (Melitaea cinxia) butterfly is a model system for metapopulation dynamics research in fragmented landscapes. Here, we provide a chromosome-level assembly of the butterfly's genome produced from Pacific Biosciences sequencing of a pool of males, combined with a linkage map from population crosses. Results The final assembly size of 484 Mb is an increase of 94 Mb on the previously published genome. Estimation of the completeness of the genome with BUSCO indicates that the genome contains 92–94% of the BUSCO genes in complete and single copies. We predicted 14,810 genes using the MAKER pipeline and manually curated 1,232 of these gene models. Conclusions The genome and its annotated gene models are a valuable resource for future comparative genomics, molecular biology, transcriptome, and genetics studies on this species.

The genome sequence of the Glanville fritillary, Melitaea cinxia (Linnaeus, 1758)

We present a genome assembly from an individual male Melitaea cinxia (the Glanville fritillary; Arthropoda; Insecta; Lepidoptera; Nymphalidae). The genome sequence is 499 megabases in span. The complete assembly is scaffolded into 31 chromosomal pseudomolecules, with the Z sex chromosome assembled. Gene annotation of this assembly on Ensembl has identified 13,666 protein coding genes.

Improved chromosome level genome assembly of the Glanville fritillary butterfly (Melitaea cinxia) based on SMRT Sequencing and linkage map

The Glanville fritillary (Melitaea cinxia) butterfly is a long-term model system for metapopulation dynamics research in fragmented landscapes. Here, we provide a chromosome level assembly of the butterfly’s genome produced from Pacific Biosciences sequencing of a pool of males, combined with a linkage map from population crosses. The final assembly size of 484 Mb is an increase of 94 Mb on the previously published genome. Estimation of the completeness of the genome with BUSCO, indicates that the genome contains 93 - 95% of the BUSCO genes in complete and single copies. We predicted 14,830 gene models using the MAKER pipeline and manually curated 1,232 of these gene models. The genome and its annotated gene models are a valuable resource for future comparative genomics, molecular biology, transcriptome and genetics studies on this species.

Associations between the larval-pupal parasitoids Erycia furibunda and E. festinans (Diptera: Tachinidae) and respectively, the sympatric and syntopic butterflies Euphydryas aurinia provincialis and Melitaea cinxia (Lepidoptera: Nymphalidae)

Several studies on butterfly ecology and biology of Melitaeini butterflies have been carried out in the past, however the factors affecting butterfly mortality and the role of natural enemies on population dynamics are not yet fully known. Larval survival plays a key role in determining butterfly population size and distribution range; thus, knowing the sources and variation in larval mortality is essential understanding and predicting population dynamics. Butterfly larval mortality is generally ascribed to abiotic factors, predators and parasitoids (mainly Diptera and Hymenoptera). Among Diptera, tachinids parasitize primarily larval Lepidoptera. In this paper, we report the results of 5-year observations in the wild and captivity on the tachinids, Erycia furibunda and E. festinans, parasitoids of caterpillars of a population of Euphydryas aurinia spp. provincialis and Melitaea cinxia in Central Italy revealing their host specifity. The hosts, E. aurinia and M. cinxia, and parasitoids, E. furibunda and E. festinans, inhabit the same habitat and their life cycles highly overlap, nevertheless, the parasitoids maintain their host specifity: E. furibunda as parasitoid of E. aurinia; E. festinans as parasitoid of M. cinxia. This was confirmed by our findings during the butterfly breeding activities carried out for over five years. Although the role of chemical cues in host finding requires further research, according to our observations the presence of only E. furibunda on larval webs of E. aurinia let us suppose that the mechanism by which E. furibunda locates its host could be based on olfactory cues emitted by feeding damage to host plants that act from afar. Similarly, the mechanism of host finding used by E. festinans could act to select its host, M. cinxia. Furthermore, we illustrate some diagnostic features of adults for the identification of the studied parasitoids.

Variation in Melitaea cinxia gut microbiota is phylogenetically highly structured but only mildly driven by host plant microbiota, sex or parasitism

Originality-Significance StatementThe factors contributing to the assembly of microbiota in animals are extremely complex, and thus a comprehensive understanding of the mechanisms shaping host-associated microbial communities in natural ecosystems requires extensive ecological studies and appropriate statistical methods. In this study, we investigated the bacterial microbiota associated with the caterpillars of the Glanville fritillary (Melitaea cinxia), which is a long-term-studied ecological model system. We assessed the structure of variation in both occurrence and abundance of gut microbial communities of individuals collected in the wild with joint-species modelling, with the aim to relate the microbial community structure with multiple potentially impacting covariates: host plant microbiota and metabolites, hosts’ sex, potential parasitoid infection, and family structure. These covariates exhibited substantial correlation with multiple microbial taxa’s occurrences, which correlations were consistent for phylogenetically related groups of taxa, but varied across the whole microbial community; on the contrary, only few correlations were found with taxa’s abundances. The dominating co-occurrence pattern of microbiota assembly, which effectively split caterpillar individuals into two distinct groups, was, however, unrelated to any of the considered covariates.SummaryUnderstanding of what ecological factors shape intraspecific variation of insect microbiota is still relatively poor. In Lepidopteran caterpillars, microbiota is assumed to be mainly composed of transient bacterial symbionts acquired from the host plant. We sampled Glanville fritillary (Melitaea cinxia) caterpillars from natural populations to describe the microbiome and to identify potential factors that determine the structure of the microbial community, including the sex of the host, the impact of parasitoid infection, and the possible link between host plant and caterpillar microbiota. Our results demonstrate high variability of microbiota composition even among caterpillars that shared the same host plant individual. The observed variation in microbiota composition is partially attributed to the measured properties of the host or its plant microbial and chemical composition, and is aligned with microbial phylogenetic structure, with related taxa exhibiting similar patterns. However, the prevailing part of the observed variation was not associated with any of the assessed characteristics, although it followed a pronounced segregation structure: in some caterpillars the microbial communities were dominated by several related Enterobacteriaceae taxa, while in others these taxa were absent. Our results challenge previous findings that the host plant properties are the major drivers of microbiota communities of insect herbivores.

To which species should the name heynei Rühl, [1893] (Lepidoptera: Nymphalidae) be referred?

Historical records of Melitaea cinxia (Linnaeus, 1758) and M. arduinna (Esper, [1783]) from the mountains of Central Asia, including named subspecies and forms, are reviewed with particular reference to the name heynei Rühl, [1893], which has been associated with both of the aforementioned species. It is concluded that the name heynei should be associated with M. arduinna and not M. cinxia. For the sake of nomenclatural stability, a specimen of M. arduinna from the southern slope of Alai Mountains (Kyrgyzstan, Daroot-Korgon) is designated as the neotype of Melitaea cinxia var. heynei Rühl, [1893]. The morphological features of M. cinxia and M. arduinna, including the subspecies of the latter, are compared and figured. The historic and recent misidentifications of M. cinxia as M. arduinna and vice versa are exemplified.