Testing the latitudinal gradient: a narrow-scale analysis of tenebrionid richness (Coleoptera, Tenebrionidae) in the Aegean archipelago (Greece)

The latitudinal pattern of tenebrionid (Coleoptera Tenebrionidae) biodiversity on the Aegean Islands (Greece) was analysed. To remove the obvious influence of area on species richness, several species-area relationships, including power, exponential, negative exponential, logistic, Gompertz, Weibull, Lomolino, and He-Legendre functions, were applied. Residuals were retained as measures of species richness corrected for area. The power function model appeared to be the most convenient one. Species richness was not statistically related to latitude. However, when the confounding effect of area was removed, tenebrionid species richness and levels of endemism increased significantly at lower latitudes. This latitudinal pattern can be explained both as a consequence of increasing mean annual temperatures at lower latitudes (favouring thermophilic species) and as a reflection of the role in speciation played by southern areas during Tertiary land evolution and Pleistocene eco-geographic conditions.