Geography-related sub-generic diversity within the Mediterranean trapdoor spider genus Nemesia ( Araneae , Mygalomorphae , Nemesiidae )

Three different male and female super-specific types are distinguished according to variations in the morphology of the bulb and spermathecae within the genus Nemesia Audouin, 1826. Plotting the distributions of these sexual types on a map of the Mediterranean indicates the existence of geography-related sub-generic diversity in which the Nemesia fauna of the eastern Mediterranean differs markedly from that of the western Mediterranean. While the eastern Mediterranean Nemesia fauna is highly homogeneous, the fauna of the western Mediterranean is very diverse. The eastern and western Nemesia faunae appear to overlap in the central Mediterranean. Efforts to relate the specific bulb types to the particular types of spermathecae described here were only partly successful.

The trapdoor spider genus Nemesia Audouin, 1826 is currently considered to be a potentially valuable model system for studies in evolutionary biology (Decae 2010, Arnedo pers. comm.).The fact that Nemesia exhibits high species diversity in the geographically confined region of the Mediterranean offers exceptional opportunities for studies on local variation and speciation.Moreover, the common occurrence of Nemesia throughout the region, both on islands and continents, in a range of different habitats (from sandy shores to alpine heights and from semi-deserts to humid forests), its supposedly sedentary habits, its poor capacity for dispersal and its probably ancient origin, reveals the genus as a coherent sample of evolving lineages that offer highly prospective opportunities for virtually all lines of biological research.Unfortunately, this potential for biological research into Nemesia is hampered by a lack of basic knowledge.The taxonomy of Nemesia is poorly resolved and partly confused, the real species diversity cannot even be estimated and there is no good insight into the internal organization of the genus in terms of the possible existence of sub-generic groups.A basic problem is that classical spider taxonomy is exclusively focused on morphological variation in preserved specimens, and that such variation is very difficult to observe in Nemesia.Study of the taxonomically most informative morphological structures -male and female sexual organs and the spinnerets -has become common practice only very recently, which means that the whole taxonomical framework of the genus urgently needs revision.A productive first step might be to try recognizing Nemesia species groups based on the variation of the bulb and the spermathecae types, and matching the sexes.The recognition of evolutionary older sub-generic groups within Nemesia would have particular significance if it could be linked to the geographical dynamics of the Mediterranean; a region with a history of major geographical shifts (ager 1980) and dramatic geophysical events such as the Messinian salinity crisis (Krijgsman et al. 1999) and the formation of glacial refugia during the Pleistocene (méDail & DiaDema 2009).This paper is a first attempt to discover such geography-related sub-generic diversity within Nemesia.

Material and Methods
This study is based on variations in the morphology of both male and female sexual organs (i.e.bulbs and spermathecae).Because no objective criteria exist for classifying different types of spider bulbs and spermathecae, the classifications used here are necessarily arbitrary and provisional.The classifications adopted are, however, based on experience resulting from detailed observations of well over one thousand Nemesia specimens and as such might function as practical tools for discovering broad scale patterns in Nemesia sub-generic diversity.A Ceti-Medo.2 stereomicroscope with camera lucida equipment was used for examining and drawing bulbs and spermathecae submerged in 70 % ethanol.Bulbs were drawn from the organ on the right hand side of the spider in ventral view.Spermathecae were prepared for study by dissection and removing the coverage of greasy tissue mechanically with sharpened needles.This method leaves the spermathecae in situ with minimal damage to the spider specimens.Drawings were done in pencil and Artline pens for graphical design.Registration of species identity, geographical origin of each specimen and classification of sexual types were compiled in a Microsoft Excel sheet.
Six different 'sexual types', three male-types (Fig. 1) and three female-types (Fig. 2), could be distinguished.A sample of 107 and 47, collected at localities widely spread throughout the Mediterranean Region was classified according to these sexual types.The results were plotted on a map of the Mediterranean using DIVA-GIS (Hijmans et al. 2005).In an effort to match male and female sexual types, ten established species -for which both sexes were represented in the sample -were compared (Tab. 1) and set in a geographical context.

Results
Plotting 107 male records, classified according to three different bulb-types (Fig. 1), on a map shows a distinct difference between the eastern and western Mediterranean (Fig. 3).Type-A bulbs (i.e.longitudinal ribs on the proximal embolus) are the only bulb-type present in the eastern Mediterranean.In the western Mediterranean

Discussion
Perhaps the most obvious conclusion to be drawn from this study is that the Nemesia fauna in the eastern Mediterranean differs strongly from that in the western Mediterranean.While the eastern fauna appears to be highly homogeneous -all Nemesia species occurring east of approximately 14.5 E have Type-A bulbs and Type-D spermathecae -the fauna of the western Mediterranean is highly diverse (Figs. 3 & 4).All designated male and  in Nemesia diversity, it also shows that an improved taxonomy is urgently needed as a prerequisite for exploiting the great potential of Nemesia as a biological model taxon as indicated in the Introduction.