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I have stolen the original title from this article for this post as I must admit that the topic is beyond my knowledge. I do have a master in zoology, but back then we learned very little about genetics.
Anyway, Frantisek Kovarik and several other co-workers have recently published a study on the evolutionary dynamics of rDNA clusters on chromosomes of buthid scorpions. The study provides the first analysis of karyotype evolution within a phylogenetic context for the whole of the family Buthidae. For more information you can check out the abstract or the article.
We examined the distribution of genes for major ribosomal RNAs (rDNA) on holokinetic chromosomes of 74 species belonging to 19 genera of scorpions from the family Buthidae using fluorescence in situ hybridization (FISH). Our analysis revealed differences between the two main evolutionary lineages within the family. The genera belonging to the ‘Buthus group’, with a proposed Laurasian origin, possess one pair of rDNA mainly in an interstitial position, with the only exceptions being the terminal location found in some Hottentotta and Buthacus species, possibly as a result of chromosome fissions. All the remaining buthid ‘groups’ possess rDNA found strictly in a terminal position. However, the number of signals may increase from an ancestral state of one pair of rDNA loci to up to seven signals in Reddyanus ceylonensis Kovařík et al., 2016. Despite the differences in evolutionary dynamics of the rDNA clusters between the ‘Buthus group’ and other lineages investigated, we found a high incidence of reciprocal translocations and presence of multivalent associations during meiosis in the majority of the genera studied. These phenomena seem to be typical for the whole family Buthidae.
Šťáhlavský F, Nguyen P, Sadílek D, Štundlová J, Just P, Haddad CR, et al. Evolutionary dynamics of rDNA clusters on chromosomes of buthid scorpions (Chelicerata: Arachnida). Biological Journal of the Linnean Society. 2020;Online first:1-19. [Subscription required for full text]
Thanks to Frantisek Kovarik for sending me their article!