The Pleistocene species pump past its prime: Evidence from European butterfly sister species.

The Pleistocene glacial cycles had a profound impact on the ranges and genetic make-up of organisms. While it is clear that the contact zones that have been described for many sister taxa are secondary and have formed in the current interglacial, it is unclear when the taxa involved began to diverge. Previous estimates based on small numbers of loci are unreliable given the stochasticity of genetic drift and the contrasting effects of incomplete lineage sorting and gene flow on gene divergence. Here, we use genome-wide transcriptome data to estimate divergence for 18 sister species pairs of European butterflies showing either sympatric or contact zone distributions. We find that in most cases, species divergence predates the mid-Pleistocene transition or even the entire Pleistocene period. We also show that although post-divergence gene flow is restricted to contact zone pairs, they are not systematically younger than sympatric pairs. This suggests that contact zones are not limited to the initial stages of the speciation process, but can involve notably old taxa. Finally, we show that mitochondrial divergence and nuclear divergence are only weakly correlated and mitochondrial divergence is higher for contact zone pairs.

The genome sequence of the Pearl-bordered Fritillary, Boloria euphrosyne (Linnaeus, 1758).

We present a genome assembly from an individual male Boloria euphrosyne (the Pearl-bordered Fritillary; Arthropoda; Insecta; Lepidoptera; Nymphalidae). The genome sequence is 400.4 megabases in span. Most of the assembly is scaffolded into 31 chromosomal pseudomolecules, including the Z sex chromosome. The mitochondrial genome has also been assembled and is 15.17 kilobases in length. Gene annotation of this assembly on Ensembl identified 19,138 protein coding genes.

The genome sequence of the Arctic Skipper, Carterocephalus palaemon (Pallas, 1771).

We present a genome assembly from an individual male Carterocephalus palaemon (the Arctic Skipper; Arthropoda; Insecta; Lepidoptera; Hesperiidae). The genome sequence is 394.5 megabases in span. The whole assembly is scaffolded into 31 chromosomal pseudomolecules, including the Z sex chromosome. The mitochondrial genome has also been assembled and is 15.78 kilobases in length. Gene annotation of this assembly on Ensembl identified 17,032 protein coding genes.

The genome sequence of the northern brown argus, Aricia artaxerxes (Fabricius, 1793).

We present a genome assembly from an individual Aricia artaxerxes (the northern brown argus; Arthropoda; Insecta; Lepidoptera; Lycaenidae). The genome sequence is 458 megabases in span. Most of the assembly (99.99%) is scaffolded into 23 chromosomal pseudomolecules, including the assembled Z sex chromosome. The mitochondrial genome has also been assembled and is 15.8 kilobases in length. Gene annotation of this assembly on Ensembl has identified 12,688 protein coding genes.

Estimating the rates of crossover and gene conversion from individual genomes.

Recombination can occur either as a result of crossover or gene conversion events. Population genetic methods for inferring the rate of recombination from patterns of linkage disequilibrium generally assume a simple model of recombination that only involves crossover events and ignore gene conversion. However, distinguishing the 2 processes is not only necessary for a complete description of recombination, but also essential for understanding the evolutionary consequences of inversions and other genomic partitions in which crossover (but not gene conversion) is reduced. We present heRho, a simple composite likelihood scheme for coestimating the rate of crossover and gene conversion from individual diploid genomes. The method is based on analytic results for the distance-dependent probability of heterozygous and homozygous states at 2 loci. We apply heRho to simulations and data from the house mouse Mus musculus castaneus, a well-studied model. Our analyses show (1) that the rates of crossover and gene conversion can be accurately coestimated at the level of individual chromosomes and (2) that previous estimates of the population scaled rate of recombination ρ=4Ner under a pure crossover model are likely biased.

The genome sequence of the orange-tip butterfly, Anthocharis cardamines (Linnaeus, 1758).

We present a genome assembly from an individual female Anthocharis cardamines (the orange-tip; Arthropoda; Insecta; Lepidoptera; Pieridae). The genome sequence is 360 megabases in span. The majority (99.74%) of the assembly is scaffolded into 31 chromosomal pseudomolecules, with the W and Z sex chromosomes assembled. Gene annotation of this assembly on Ensembl has identified 12,477 protein coding genes.

The genome sequence of the scarce swallowtail, Iphiclides podalirius.

The scarce swallowtail, Iphiclides podalirius (Linnaeus, 1758), is a species of butterfly in the family Papilionidae. Here, we present a chromosome-level genome assembly for Iphiclides podalirius as well as gene and transposable element annotations. We investigate how the density of genomic features differs between the 30 Iphiclides podalirius chromosomes. We find that shorter chromosomes have higher heterozygosity at four-fold-degenerate sites and a greater density of transposable elements. While the first result is an expected consequence of differences in recombination rate, the second suggests a counter-intuitive relationship between recombination and transposable element evolution. This high-quality genome assembly, the first for any species in the tribe Leptocircini, will be a valuable resource for population genomics in the genus Iphiclides and comparative genomics more generally.

The genome sequence of the clouded yellow, Colias crocea (Geoffroy, 1785).

We present a genome assembly from an individual female Colias crocea (also known as Colias croceus; the clouded yellow; Arthropoda; Insecta; Lepidoptera; Pieridae). The genome sequence is 325 megabases in span. The complete assembly is scaffolded into 32 chromosomal pseudomolecules, with the W and Z sex chromosome assembled. Gene annotation of this assembly on Ensembl has identified 13,803 protein coding genes.

The genome sequences of the male and female green-veined white, Pieris napi (Linnaeus, 1758).

We present genome assemblies from a male and female Pieris napi (the green-veined white; Arthropoda; Insecta; Lepidoptera; Pieridae). The genome sequences of the male and female are 320 and 319 megabases in span, respectively. The majority of the assembly (99.79% of the male assembly, 99.88% of the female) is scaffolded into 24 autosomal pseudomolecules, with the Z sex chromosome assembled for the male and Z and W chromosomes assembled for the female. Gene annotation of the male assembly on Ensembl has identified 13,221 protein coding genes.