Petr Nguyen

A new subfamily of bagworm moths is described: Tenuipsychinae subfam. nov., to accompany the new genus Tenuipsyche gen. nov. and 2 new species, Tenuipsyche davisi sp. nov., and Tenuipsyche nishidai sp. nov., based on unique and unusual morphology, biology, and their phylogenetic position inferred via phylogenomic analysis of 13 mitochondrial protein-coding genes and 3 nuclear markers. The biology is highly distinctive in that the fungal-feeding larvae construct long, narrow bags permanently affixed to a substrate, rendering them sessile, a very unusual condition among the Psychidae. Furthermore, the genera Antillonatus, Acoremata, Guttulapsyche, and Lamyristis are transferred to Tenuipsychinae due to shared adult morphology. Species in the subfamily have winged female forms and appear to occur on most continents across the world within tropical and subtropical areas where many undescribed taxa are known. Phylogenetic analysis confirms that Tenuipsychinae is a monophyletic subfamily which forms a sister clade to the previously described female winged subfamilies Arrhenophaninae and Pseudarbelinae.

Plants produce broad spectra of metabolites comprising primary metabolites involved in core physiological processes and specialized metabolites mediating responses to biotic and abiotic stress. Understanding how these various components of the metabolome respond to different environmental pressures can help us to understand drivers of phytochemical diversity and its role in plant ecology and evolution. We investigated how climatic stress, soil resources, and herbivory influence various measures of phytochemical diversity in four willow species along an elevational gradient (950–2250 m a.s.l.), focusing on flavonoids, salicinoids, and primary metabolites. Harsher climates increased metabolite concentrations, particularly salicinoids, but reduced flavonoid richness and overall structural α‐diversity. Similar responses in primary metabolites suggest that these shifts extend beyond defence chemistry. Chemical properties showed the strongest shifts in flavonoids and salicinoids and weaker changes in primary metabolites. β‐diversity generally increased with elevation and was most strongly associated with climate, while soil nutrients contributed to shifts in β‐diversity of salicinoids and primary metabolites. Willow species showed weak genetic differentiation across elevation, suggesting limited population divergence. Together, these results indicate that elevational shifts in willow chemistry involve broad but uneven reorganization across the metabolome, with different metabolite groups and measures of diversity plastically responding to different drivers.

Chromosomal rearrangements act as barriers to gene flow and can thus promote speciation. In moths and butterflies (Lepidoptera), which possess holocentric chromosomes facilitating karyotype changes, chromosome fusions are more common than fissions. Yet, limited evidence suggests that when speciation involves chromosomal rearrangements, it is most often linked to fissions. Notable karyotypic variation is observed in three clades of the subfamily Polyommatinae (Lycaenidae), with chromosome numbers ranging from n = 10 to 225. We investigated genome sizes and karyotypes in several species of the genera Polyommatus and Lysandra with modal and derived high chromosome numbers. Our findings showed no support for polyploidy, confirming previous conclusions about karyotypic diversification via chromosome fragmentation in this butterfly family. Species with high chromosome numbers have slightly larger genomes, which indicate a potential role of repetitive sequences but contradict the hypothesis of holocentric drive. Ends of fragmented chromosomes were healed with telomeres synthesized de novo, which were significantly larger than those of species with modal karyotype. No interstitial telomeric sequences were detected on autosomes. Internal telomeric signals on sex chromosomes, however, revealed multiple sex chromosome systems in Polyommatus (Plebicula) dorylas and Polyommatus icarus, with two karyotype races differing in sex chromosome constitution in the latter. Notably, the W chromosome resisted fragmentation, presumably due to its epigenetic silencing.

Sex chromosomes have evolved repeatedly across eukaryotes. The emergence of a sex‐determining (SD) locus is expected to progressively restrict recombination, driving convergent molecular differentiation. However, evidence from taxa like teleost fishes, representing over half of vertebrate species with unmatched diversity in SD systems, challenges this model. Teleost sex chromosomes are often difficult to detect as they experience frequent turnovers, resetting the differentiation process. Nothobranchius killifishes, which include the XY system shared by N. furzeri and N. kadleci and X₁X₂Y systems in six other species, offer a valuable model to study sex chromosome turnovers. We characterised X₁X₂Y systems in five killifish species and found that sex chromosomes evolved at least four times independently. Sex‐determining regions resided near centromeres or predicted chromosome rearrangement breakpoints in N. brieni and N. guentheri, suggesting recombination cold spots may facilitate sex chromosome evolution. Chromosomes representing the XY system in N. furzeri/N. kadleci were sex‐linked also in the outgroup Fundulosoma thierryi, with several genes, including gdf6, residing in the region of differentiation. Although the X₁X₂Y systems of N. guentheri, N. lourensi (both Coastal clade), and N. brieni (Kalahari clade) involved different chromosomes, they shared a potential SD region. We uncovered two sex‐linked evolutionary strata of distinct age in N. guentheri. However, its potential SD gene amhr2 was located in the younger stratum and is hence unlikely to be the ancestral SD gene in this lineage. Our findings suggest recombination landscapes shape sex chromosome turnover and that certain synteny blocks are repeatedly co‐opted as sex chromosomes in killifishes.

Hybridization can create novel chemical traits and enhance plant adaptability to diverse environments. This study examined the effects of hybridization on chemical diversity and ecological interactions in Salix alba×fragilis hybrids from the Elbe River basin (Czechia). We analysed leaf metabolites of hybrids and their parental species for concentration, richness, and structural α- and β-diversity, linking them to herbivorous insect assemblages and soil conditions. Hybrids exhibited intermediate metabolite concentration and richness but showed higher structural α-diversity and distinct structural β-diversity compared with their parents. Hybrid-specific metabolites were structurally related to parental metabolites, indicating minor structural modifications rather than major changes to metabolic pathways following hybridization. Herbivore assemblages were influenced by metabolite richness or structural α-diversity. However, insect group responses varied, and herbivory damage did not correlate with leaf chemistry or differ between hybrids and parents. Soil nitrogen correlated with metabolite structural β-diversity, with hybrids displaying greater chemical variation along nitrogen gradients. These results highlight that hybridization significantly altered structural metabolite diversity. Yet, the structural changes were relatively minor which, together with group-specific responses of herbivores, could explain their modest effect on herbivory. Instead, they may enable these hybrids to flexibly respond to soil conditions, possibly contributing to their widespread occurrence.

Chromosomal rearrangements are crucial in speciation, acting as barriers to gene flow. Holocentric chromosomes, such as those in Lepidoptera, can facilitate karyotype changes. Despite chromosome fusions being more common, speciation events are mostly linked to fissions. Notable karyotypic variation is observed in three clades of the subfamily Polyommatinae (Lycaenidae), with chromosome numbers ranging from n = 10 to n = 225. This study used flow cytometry and molecular cytogenetic analyses to investigate genome sizes and karyotypes in several species of the genera Polyommatus and Lysandra with derived and modal chromosome numbers. The findings show no support for polyploidy, supporting karyotypic diversification via fragmentation of chromosomes. Species with high chromosome numbers have larger genomes, which indicates a potential role of mobile elements but contradicts the hypothesis of holocentric drive. Telomeric signals were detected at the ends of fragmented chromosomes. No interstitial telomeric sequences were detected on autosomes. Interstitial telomeric signals on sex chromosomes, however, revealed multiple sex chromosome systems in Polyommatus dorylas and Polyommatus icarus , with two karyotype races differing in sex chromosome constitution in the latter. Pool-seq and coverage analyses indicated shared fusion of sex chromosomes with an autosome bearing the rDNA locus, followed by a fusion with chromosome 20 in the Czech population. Notably, the W chromosome resists fragmentation, likely due to epigenetic silencing protecting it from activity of mobile elements.

Sex chromosomes of teleost fishes often have low levels of differentiation and undergo frequent turnovers. Annual Nothobranchius killifishes comprise representatives with male-heterogametic XY or X1X2Y sex chromosome systems, scattered across their phylogeny, nested within species lacking cytologically detectable sex chromosomes. They thus provide a suitable system to study sex chromosome evolution and turnover. Here, we combined molecular cytogenetics and genomic analyses to examine several multiple sex chromosome systems in Nothobranchius spp. and their outgroup Fundulosoma thierryi. We used fluorescence in situ hybridization with three sex chromosome-specific painting probes and bacterial artificial chromosomes (BAC) bearing eight orthologues of genes found to be repeatedly co-opted as master sex determining (MSD) genes in fishes. Our results suggest at least four independent origins of sex chromosomes in the genus Nothobranchius. The synteny block carrying amhr2 gene was shared by X1X2Y systems of N. brieni, N. guentheri and N. lourensi, but the autosomal additions and the overall neo-Y chromosome structure differed among these species. On the other hand, gdf6 gene was localized to neo-Y of F. thierryi. None of the mapped MSD gene candidates seems to determine sex in N. ditte. We further sequenced genomes of F. thierryi female and N. guentheri male by long-read platforms and performed analyses of male and female Pool-seq data and coverage to delimit their non-recombining regions, determine degree of their differentiation, and thus complement the cytogenetic data in assessing potential MSD genes. We found low level of sex chromosomes differentiation in F. thierryi. In N. guentheri, however, we identified two distinct evolutionary strata on neo-Y. The amhr2 gene resides in the younger stratum and has low allelic variation, which questions its role in sex determination.

Sex chromosomes play an outsized role in adaptation and speciation, and thus deserve particular attention in evolutionary genomics. In particular, fusions between sex chromosomes and autosomes can produce neo‐sex chromosomes, which offer important insights into the evolutionary dynamics of sex chromosomes. Here, we investigate the evolutionary origin of the previously reported Danaus neo‐sex chromosome within the tribe Danaini. We assembled and annotated genomes of Tirumala septentrionis (subtribe Danaina), Ideopsis similis (Amaurina), Idea leuconoe (Euploeina) and Lycorea halia (Itunina) and identified their Z‐linked scaffolds. We found that the Danaus neo‐sex chromosome resulting from the fusion between a Z chromosome and an autosome corresponding to the Melitaea cinxia chromosome (McChr) 21 arose in a common ancestor of Danaina, Amaurina and Euploina. We also identified two additional fusions as the W chromosome further fused with the synteny block McChr31 in I. similis and independent fusion occurred between ancestral Z chromosome and McChr12 in L. halia. We further tested a possible role of sexually antagonistic selection in sex chromosome turnover by analysing the genomic distribution of sex‐biased genes in I. leuconoe and L. halia. The autosomes corresponding to McChr21 and McChr31 involved in the fusions are significantly enriched in female‐ and male‐biased genes, respectively, which could have hypothetically facilitated fixation of the neo‐sex chromosomes. This suggests a role of sexual antagonism in sex chromosome turnover in Lepidoptera. The neo‐Z chromosomes of both I. leuconoe and L. halia appear fully compensated in somatic tissues, but the extent of dosage compensation for the ancestral Z varies across tissues and species.

Satellite DNA (satDNA) is a rapidly evolving class of tandem repeats, with some monomers being involved in centromere organization and function. To identify repeats associated with (peri)centromeric regions, we investigated satDNA across Southern and Coastal clades of African annual killifishes of the genus Nothobranchius. Molecular cytogenetic and bioinformatic analyses revealed that two previously identified satellites, designated here as NkadSat01-77 and NfurSat01-348, are associated with (peri)centromeres only in one lineage of the Southern clade. NfurSat01-348 was, however, additionally detected outside centromeres in three members of the Coastal clade. We also identified a novel satDNA, NrubSat01-48, associated with (peri)centromeres in N. foerschi, N. guentheri, and N. rubripinnis. Our findings revealed fast turnover of satDNA associated with (peri)centromeres and different trends in their evolution in two clades of the genus Nothobranchius.