Rod: Dysdera

The genus Dysdera Latreille, 1804, a species-rich group of spiders that includes specialised predators of woodlice, contains several complexes of morphologically similar sibling species. Here we investigate species limits in the Dysdera erythrina (Walckenaer, 1802) complex by integrating phenotypic, cytogenetic and molecular data, and use this information to gain further knowledge on its origin and evolution. We describe 16 new species and redescribe four poorly known species belonging to this clade. The distribution of most of the species in the complex is limited to southern France and the north-eastern Iberian Peninsula. The species studied do not show any obvious differences in habitat preference, and some of them even occur sympatrically at certain sites. They probably feed on the same type of prey as they readily capture woodlice. On the other hand, they differ in body size, mouthparts shape, sculpturing of carapace, morphology of the copulatory organs, karyotype and DNA sequences. Experimental interspecific mating showed a partial precopulatory behavioural barrier between Dysdera erythrina and Dysdera cechica, sp. nov. Our data suggest that karyotype evolution of the complex included chromosome fusions and fissions as well as translocations (between autosomes as well as autosomes and sex chromosomes). We hypothesise that chromosome rearrangements generating reproductive incompatibility played a primary role in speciation within Dysdera complexes. Dysdera spiders are poor dispersers, and their original distribution areas (forested areas in the Mediterranean) were repeatedly fragmented during Quarternary climatic oscillations, facilitating integration of chromosome rearrangements into karyotypes by genetic drift. Sympatric occurrence of closely related species may have been promoted by prey segregation as suggested by differentiation in body size in co-occurring species. The following new species are described: D. catalonica, sp. nov., Dysdera cechica, D. dolanskyi, sp. nov., D. fabrorum, sp. nov., D. garrafensis, sp. nov., D. graia, sp. nov., D. kropfi, sp. nov., D. minairo, sp. nov., D. portsensis, sp. nov., D. pradesensis, sp. nov., D. pyrenaica, sp. nov., D. quindecima, sp. nov., D. septima, sp. nov., D. stahlavskyi, sp. nov., D. tredecima, sp. nov. and D. undecima, sp. nov.

The dietary specialization in a woodlouse-eating spider Dysdera hungarica Kulczyñski (Araneae: Dysderidae) is studied using two types of laboratory experiments. In the first experiment, the rate of development of spiderlings reared on one of three diets: pure woodlice [composed of two species Oniscus asellus Linnaeus and Armadillidium vulgare (Latreille)], pure flies (Drosophila melanogaster Meigen), and a mixed woodlouse-fly diet, is studied. Spiders develop significantly faster on the woodlice-containing diets (i.e. pure woodlice and mixed diet) than on the fly diet. In the second experiment, the prey-choice for two woodlice species (O. asellus and A. vulgare) and a fly (D. melanogaster) is investigated. Dysdera hungarica spiders capture significantly more often flies than woodlice. These contrasting results reveal the different value of developmental and behavioural experiments. The dietary studies are assumed to provide better evidence of specialization than behavioural experiments, which might be misleading due to unnatural conditions. It is concluded that D. hungarica is a metabolically adapted woodlice specialist. The present study thus provides the first evidence of nutritional specialization on woodlice.