Aim Genome‐wide genetic data can provide key input for both taxonomy and conservation, but its use in this context remains limited. In this study, we performed the first genome‐wide assessment of genetic variation in two populations of the Eurasian lynx, the Balkan population, the most threatened, and the Caucasian population, a possible glacial refugium, with the aim to place them in the context of the species, investigate their demographic history and evaluate their genetic status. Location The Balkans and the Caucasus. Methods We obtained whole genome resequencing data from seven Balkan and 12 Caucasian lynx, and analysed them along with novel and existing data from other populations. Based on a total 105 whole genome and 114 mitogenome sequences, we reconstructed phylogenetic and historical relationships, ancient and recent demography, and patterns of genetic diversity and inbreeding. Results Both the Balkan and the Caucasian lynx appear as distinct mitochondrial lineages that diverged from the rest of the Eurasian lynx lineages ca. 92.6 kya, and from each other ca. 46.4 kya. Autosomal data suggest, however, that the Balkan lynx is closely related with the Carpathian population, and revealing alarmingly low genetic diversity and high inbreeding. In contrast, the Caucasian lynx shows a longer history of relative isolation from the rest of lynx populations and high genetic diversity, consistent with its large long‐term effective population size. Main conclusions The taxonomic status of the Balkan lynx remains unresolved due to the evidence of long‐term isolation in the mitogenome, contrasting with extensive autosomal admixture and intense recent genetic drift in the nuclear genome. Our results alert on genetic risks and call for the consideration of genetic rescue from closely related Carpathian lynxes. In contrast, substantial mitogenomic and autosomal divergence with no signs of genetic drift supports the identification of the Caucasian lynx as a separate subspecies with good genetic health.

The sea hare Bursatella leachii (de Blainville 1817) (Mollusca: Gastropoda: Heterobranchia: Aplysiidae) is a pantropical sea slug that has colonized the Mediterranean Sea in modern times. Because the initial records in the non-native range started in the Eastern Mediterranean, and its pattern of spread was relatively consistent with those observed in well-known Lessepsian invaders, B. leachii is commonly considered to be a migrant from the Red Sea. In this study, we investigate for the first time the origin of the Mediterranean populations of B. leachii inferring their population structure and assessing relatedness levels of different regional populations. Sequence data from the cytochrome oxidase I were used to conduct population genetic analyses on this species, particularly by investigating the genetic structure of Atlantic, Mediterranean, and Indo-Pacific populations. Our results confirm that B. leachii is a truly pantropical species which displays geographic structure among major ocean basins. More importantly, sequenced Mediterranean and Atlantic animals share similar or identical haplotypes, which are distinct in at least 5 substitutions from haplotypes recovered from Indo-Pacific specimens. The results suggest that the Mediterranean population of B. leachii here examined probably have an Atlantic origin, and for the first time casts doubts on the assumed primary pathway of migration into the Mediterranean Sea.

The ragged sea hare (Bursatella leachii) and the long-tailed sea hare (Stylocheilus striatus) are two widely distributed species of benthic heterobranch sea slugs. In this paper, integrative taxonomic analyses have been conducted to detect possible cryptic diversity. Our results revealed that both nominal species are actually species complexes, consisting of five genetically distinct taxa. Two of them belong to the genus Bursatella and three to the genus Stylocheilus. The name B. leachii is retained for a widely distributed species, present in the Atlantic, the Mediterranean, and parts of the Indo-Pacific region. The name B. ocelligera is resurrected for the other species, restricted to the Indo-Pacific and co-occurring with B. leachii in that area. With the present data, it is not possible to test whether B. leachii and B. ocelligera have evolved allopatrically in the Atlantic and Indo-Pacific or sympatrically in the latter. Bursatella leachii has been able to maintain gene flow between the Atlantic and the Indo-Pacific Oceans, possibly because of a combined effect of the Agulhas Leakage process and the ability to survive the colder waters of South Africa. On the contrary, the three species of Stylocheilus are allopatric; the name S. striatus is retained for an Indo-Pacific species, while the names S. polyomma and S. rickettsi are resurrected for species inhabiting the Western Atlantic and the Eastern Pacific respectively. Finally, the discovery of a museum specimen mistakenly identified as B. leachii, but bearing a shell in its adult form, led to the resurrection of the genus Phycophila, previously synonymised with Aplysia. Phycophila euchlora, the only species described to date, is distributed in the Central and Western Pacific Ocean.

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