Kay Lucek

Understanding how reproductive isolation is maintained between closely related taxa is a central question in evolutionary biology. Here, we investigate the mechanisms underlying divergence and isolation between two sister butterflies, Erebia palarica and Erebia meolans , which occur in sympatry in the Cantabrian Mountains (N Spain) and in allopatry elsewhere. Using an integrative approach, we combine genetic, genome synteny and cytogenetic analyses, Wolbachia screening, and geometric morphometrics to assess their evolutionary history and elucidate potential reproductive barriers between these species. The phylogeographic pattern suggests that both species diverged in allopatry, coming into secondary contact along the Cantabrian Mountains after the last glacial maximum. Both mitochondrial and nuclear markers recover reciprocal monophyly, indicating the absence of recent hybridisation. The identical chromosome numbers in both species (2 n = 28), the absence of major chromosomal rearrangements or straightforward genitalia differentiation, and the presence of the same Wolbachia strain in all infected individuals suggest that neither chromosomal rearrangements nor Wolbachia ‐induced incompatibilities contribute to their reproductive isolation in sympatry. In contrast, morphometric analyses show a significant divergence in wing size consistent with asymmetric character displacement: sympatric populations of E. palarica exhibit larger wings relative to both allopatric conspecifics and sympatric E. meolans , whereas E. meolans shows little size variation across northern Spain. Our findings point to wing size divergence in E. palarica as a response to sympatry with E. meolans . Overall, this study provides novel empirical evidence for morphometric character displacement in the family Nymphalidae, highlights the importance of multidisciplinary approaches for understanding species differentiation, and sets a framework for future genomic studies of speciation and reproductive isolation between closely related taxa.

DNA metabarcoding is an emerging approach to study diets across a broad range of species but requires careful optimisation of the sample collection method and substrate used. The suitability of different sample types to identify the diet of the target species remains under investigated. Here, we address these knowledge gaps by collecting four different sample types - faeces, beak swabs, talon swabs, and soil samples - during nest visits of white-tailed eagles ( Haliaeetus albicilla ) during the 2025 breeding season in South Greenland. We further investigated whether some eagle dietary taxa could act as vectors for microplastic pollution. Our analyses revealed a broad diet, with 25 dietary taxa for white-tailed eagles. Lumpfish ( Cyclopterus lumpus ) was the most frequently detected dietary taxon in the diet, which was composed of 75 % fish, 19 % birds, and 7 % mammals. Our findings indicate that diets varied strongly between nesting sites. Although each sample type was efficient in capturing diet, soil and beak swabs were most promising for eagles and gave comparable results. On the other hand, faeces provided a distinct dietary profile with a reduced detection of fish, while requiring an increased sample size, and talon swabs missed rare food items. Finally, we recovered microplastic contamination in 33 % of our samples, but no dietary taxon was associated with microplastic pollution. Taken together our results underline the overlooked value of soil from nests to provide dietary information and highlight the necessity to deepen our knowledge of Arctic food webs and their microplastic contamination.

Gene flow between diverging species can reshuffle genomic variation and greatly influence the speciation process, sometimes reinforcing, sometimes eroding species boundaries. However, the effect of ecological and historical processes on the patterns of introgression remains poorly understood. Here, we focus on the evolutionary history of Heliconius besckei , a geographically restricted butterfly endemic to the Brazilian Atlantic Forest, together with the mimetic H. melpomene nanna , the sympatric non-mimetic H. ethilla narcaea , and its closely related H. numata robigus . Using whole-genome sequencing, genome-wide tests of introgression, demographic modelling and palaeoclimatic species distribution models, we tested the extent and timing of interspecific gene flow in relation to mimicry, ecological context, and changes in geographic overlap. Despite strong genomic differentiation among the four focal Heliconius species, we detected widespread signatures of interspecific gene flow, greatly influenced by geographical overlap. Demographic models including post-divergence gene flow were better supported than strict-isolation models. In addition, genome-wide introgression analyses showed more numerous and larger candidate introgressed regions between H. besckei and H. ethilla narcaea , consistent with recurrent opportunities for exchange between these currently sympatric species. Species distribution models further recovered repeated expansions of suitable habitat for H. besckei during cold periods, providing a potential geographic context for secondary contact within the Atlantic Forest. Together, our results reveal recurrent gene flow occurring under different temporal, geographic, and potentially selective contexts, and show that the evolutionary history of a geographically restricted lineage can be shaped by repeated genetic exchange while substantial species differentiation is maintained.

We present a genome assembly from a female specimen of Melitaea varia (Grisons Fritillary; Arthropoda; Insecta; Lepidoptera; Nymphalidae). The assembly contains two haplotypes with total lengths of 610.50 megabases and 544.55 megabases. Most of haplotype 1 (99.89%) is scaffolded into 32 chromosomal pseudomolecules, including the W and Z sex chromosomes. Haplotype 2 was assembled to scaffold level. The mitochondrial genome has also been assembled, with a length of 15.17 kilobases. Gene annotation of this assembly on Ensembl identified 14,173 protein-coding genes.

We present a genome assembly from afor high molecular weight female specimen of Erebia triaria (de Prunner’s Ringlet; Arthropoda; Insecta; Lepidoptera; Nymphalidae). The assembly contains two haplotypes with total lengths of 521.30 megabases and 412.03 megabases. Most of haplotype 1 (99.7%) is scaffolded into 17 chromosomal pseudomolecules, including the Z 1 , Z 2 , and W sex chromosomes. Haplotype 2 was assembled to scaffold level. The mitochondrial genome has also been assembled, with a length of 15.26 kilobases. Gene annotation of this assembly on Ensembl identified 14,057 protein-coding genes.

We present a genome assembly from a male specimen of Pyrgus malvoides (Southern Grizzled Skipper; Arthropoda; Insecta; Lepidoptera; Hesperiidae). The assembly contains two haplotypes with total lengths of 746.71 megabases and 747.11 megabases. Most of haplotype 1 (99.8%) is scaffolded into 31 chromosomal pseudomolecules, including the Z sex chromosome. Haplotype 2 was assembled to scaffold level. The mitochondrial genome has also been assembled, with a length of 15.41 kilobases. Gene annotation of this assembly on Ensembl identified 14,715 protein-coding genes.

We present a genome assembly from a female specimen of Spialia sertorius (Red-underwing Skipper; Arthropoda; Insecta; Lepidoptera; Hesperiidae). The assembly contains two haplotypes with total lengths of 364.57 megabases and 323.91 megabases. Most of haplotype 1 (99.92%) is scaffolded into 32 chromosomal pseudomolecules, including the W and Z sex chromosomes. Haplotype 2 was assembled to scaffold level. The mitochondrial genome has also been assembled, with a length of 15.34 kilobases. Gene annotation of this assembly on Ensembl identified 12,823 protein-coding genes.

We present a genome assembly from a female specimen of Boloria pales (Shepherd’s Fritillary; Arthropoda; Insecta; Lepidoptera; Nymphalidae). The assembly contains two haplotypes with total lengths of 382.99 megabases and 364.88 megabases. Most of haplotype 1 (99.96%) is scaffolded into 30 chromosomal pseudomolecules, including the Z sex chromosome. Haplotype 2 was assembled to scaffold level. The mitochondrial genome has also been assembled, with a length of 15.17 kilobases. Gene annotation of this assembly on Ensembl identified 12,117 protein-coding genes.

Chromosomal rearrangements are hypothesized to facilitate speciation by suppressing recombination in locally adapted genomic regions, yet how they shape evolutionary rates during rapid divergence remains poorly understood. Here, we investigate the genomic architecture of two sister Carex (Cyperaceae) species on Réunion Island, which rapidly diverged (∼0.5 Mya) to occupy contrasting tropical-montane and dry-subalpine habitats. Using chromosome-level assemblies and population genomics, we show that genomic divergence is not uniform across the genome but is concentrated within specific large-scale inversions. Crucially, genes within these structural variants exhibit significantly accelerated rates of protein evolution, as evidenced by elevated ω, compared to the collinear genome. This is consistent with recombination suppression and subsequent relaxation of purifying selection driving these patterns, which may complement or even outweigh the signal of positive selection. Functional analysis and environmental associations reveal that these “genomic accelerators” include key adaptive loci: Inversions on chromosomes 14 and 28 are enriched for mechanosensitive ion channels and auxin transport, which is consistent with facilitating the interspecific physiological shift to aridity. Partial redundancy analyses reveal that ongoing intraspecific ecological adaptation is highly polygenic across the collinear genome. Our results demonstrate that genomic architecture actively dictates evolutionary speed, suggesting that certain lineages boosted by structural variants may bypass the typical constraints of purifying selection to rapidly exploit vacant ecological opportunities.