Relationship between intraspecific variation in segment number and geographic distribution of Himantarium gabrielis (Linné, 1767) (Chilopoda: Geophilomorpha) in Southern Europe
Arthropods have mainly an invariant number of trunk segments. However, segment number increases with growth and post-embryonic development in certain arthropod groups. As concerns centipedes, most of geophilomorph species present intraspecific variation in the number of trunk segments that is not agerelated. Previous studies have shown that species of geophilomorphs from cold and temperate regions tend to have fewer segments than those from warmer regions. Here, we study the geographic pattern of variation at the phenotypic level in Himantarium gabrielis (Linné). To better understand the geographic patterning, we compared 436 specimens from the Balkan and the Apennine peninsulas. Data are provided, all of which reveal evidence of a difference between the peninsulas, towards an increased number of segments in the Balkan region in both sexes. Our results indicate that in males, the variation between the Apennine and the Balkan specimens approaches 32 segments, whereas in females the difference is even higher, reaching 48 segments. We also observed a bimodal distribution of segment numbers in Apennine samples but not in those from the Balkan region. We investigated possible relations of this bimodality with environmental and historical characteristics of the region.
Apennine, Balkans, bimodality, contingency tables, leg-bearing segments, Mediterranean region