EVOLUTION OF GENOME SIZE IN DARKLING BEETLES (TENEBRIONIDAE, COLEOPTERA)

Thirty-seven species of tenebrionid beetles from mainland Spain and the Balearic Islands and Canary Islands have been surveyed for nuclear DNA content of Feulgen-stained spermatids. The range of 1C genome sizes among 44 species checked to date is relatively moderate at nearly fivefold, from 0.18 to 0.86 pg, with an average value of 0.36 pg, but it contrasts with the small range of chromosome numbers in these beetles. Highly significant correlations (p < 0.001) between genome size and either spermatid area or whole metaphase I chromosomal area were found in these species. Moreover, their nuclear DNA content also correlated significantly (p < 0.05) with diploid chromosome number. A striking difference between the average DNA content of Tentyriinae and Tenebrionidae was also detected, that of the Tentyriinae being clearly smaller. A possible trend towards decrease in genome size could possibly explain most of evolutionary divergence in Tenebrionidae except for Blaps and some Opatrini, which have probably undergone substantial increases of nuclear DNA content.