Recent speciation and phenotypic plasticity within a parthenogenetic lineage of levantine whip spiders (Chelicerata: Amblypygi: Charinidae)

• Published in: Molecular phylogenetics and evolution 2022-10, Vol.175, p.107560-107560, Article 107560
• Main Authors: Baker, Caitlin M., Ballesteros, Jesús A., Aharon, Shlomi, Gainett, Guilherme, Armiach Steinpress, Igor, Wizen, Gil, Sharma, Prashant P., Gavish-Regev, Efrat
• Format: Article
• Language: English
• Subjects: Genotyping-by-sequencing; Molecular clock; Population genomics; Sarax; Sympatry; Troglophile
• ISSN: 1055-7903; 1095-9513
• DOI: 10.1016/j.ympev.2022.107560

[Display omitted] •Sarax ioanniticusandS. israelensisare troglophilic whip spiders found in the Levant.•COI and ddRAD support that they are distinct species that split ∼7.27 Mya.•We confirmed both Sarax species are parthenogenetic in Israel.•We found phenotypic variation in eyes, despite lack ofgenetic variation in both species.•Parthenogenesis suggests variation in eyes as a result of epigenetic mechanisms. Caves constitute ideal study systems for investigating adaptation and speciation, as the abiotic conditions shared by aphotic habitats exert a set of environmental filters on their communities. Arachnids constitute an important component of many cave ecosystems worldwide. We investigated the population genomics of two whip spider species: Sarax ioanniticus, a widely distributed parthenogenetic species found across the eastern Mediterranean; and S. israelensis, a recently described troglomorphic species that is endemic to caves in Israel. Here, we show that S. israelensis is completely genetically distinct from S. ioanniticus and most likely also a parthenogen. Counterintuitively, despite the lack of genetic variability within S. ioanniticus and S. israelensis, we discovered considerable variation in the degree of median eye reduction, particularly in the latter species. Natural history data from captive-bred specimens of S. israelensis validated the interpretation of parthenogenesis. Our results are most consistent with a scenario of a sexual ancestral species that underwent speciation, followed by independent transitions to apomictic parthenogenesis in each of the two daughter species. Moreover, the lack of genetic variability suggests that variation in eye morphology in S. israelensis is driven exclusively by epigenetic mechanisms.