Taxonomic implications
Our two starting hypotheses explained the reported lack of sorting in mitochondrial and nuclear genes among nominal species, either as a single species exhibiting extreme morphological polymorphism or as two nominal species with restricted hybridisation between them. Instead, our results support the existence of a third lineage, along with H. maderiana and H. insularum MDB, consisting of the individuals from Porto Santo initially assigned to H. insularum . Hence, the fuzzy boundaries between the species would be due to incomplete lineage sorting. Interestingly, H. insularum exhibits intraspecific variation in shape and size across the islands (Crespo et al., 2022), which led Wunderlich (1992) to describe the species H. biscoitoi Wunderlich, 1992, based on specimens from Porto Santo. Subsequently, Crespo et al. (2022) proposed H. biscoitoi as a junior synonym ofH. insularum due to the lack of diagnostic morphological features and genetic distinctiveness. The lack of diagnostic features amongH. insularum specimens from different island populations (Madeira, Desertas, Bugio and Porto Santo), with only minor variations, could also be attributed to homogeneous genetic variation caused by incomplete lineage sorting. This process can preserve symplesiomorphic morphological states, as suggested by (Futuyma, 2010). Crespo et al. (2022) further proposed the existence of a phenotypic continuity between the two extremes represented by the nominal species H. maderiana or H. insularum . Notably, most specimens with intermediate size and/or yellowish pilosity on the anterior legs, found in Porto Santo, correspond to H. maderiana, as also recovered in our results. Unfortunately, the limited sample of specimens from the different islands prevented us from conducting quantitative morphological analyses to further test the morphological distinctiveness of the island populations of H. insularum.
The rejection of gene flow across the different species in our MadeiranHogna is surprising, given that recent studies have revealed the key role of gene flow between islands in promoting habitat adaptation inHogna species on the Galapagos Islands (De Busschere et al., 2015). In this regard, wolf spiders are well-reputed for their great ability for long-distance dispersal (Bonte et al., 2006; Dries & Maelfait, 2001), as already illustrated by the presence ofH. insularum in multiple islands. A possible explanation for the lack of hybridisation, or even a potential driver of speciation in our model system, could be found in the complex courtship behaviour exhibited by wolf spiders, which has frequently been used to diagnose species (Chiarle et al., 2013; Just et al., 2019). Although little is known about the courtship behaviour of Madeiran Hogna , the species pair H. maderiana and H. insularum differ in traits related to male signalling during courtship displays. Specifically, H. maderiana has pedipalps and front legs conspicuously marked in orange, which are absent in H. insularum . The absence of gene flow or hybridisation events in Hogna speciation may hint at the development of specific courtship behaviours during mating, which prevents genetic material from crossing between species and could promote speciation in Madeiran Hogna.