Biology session

Species of genus Eresus are easy to recognize due to their male’s bright red coloured abdomen and their black spots. The conspicuous coloration is apparently a Batesian mimicry where the mimic has resemblance to unpleasant tasting/poisonous things. Males with the active (more dangerous) lifestyle use multiple models (like ladybirds and firebugs). Despite most of Eresus species are red and black, some species’ males have different colourations: various black and white patterns with no red colours. During my research I was looking for answers how these two aposematic signals originated and distributed.

We have two hypotheses: the red colour appeared as an evolutionary novelty, which should predict a monophyletic red aposematic signal clade. Alternatively, multiple appearances and disappearances could have happened predicting mosaic distribution of the character.

To test our hypotheses, we needed to reconstruct a stable phylogenetic tree, inferred from a multigene (COI, 28S and 16S) approach. During the research maximum likelihood and Bayesian trees have been calculated. The topology of the tree was constant, thus an adequate foundation for such a character evolution analysis. Based on our results the black and white pattern is plesiomorph and a single origin of red-and-black coloration was well supported. At the same time multiple changes to other black-and-white have been observed.

Comparing the geographic distribution, we suggested with possible models for the black and white species.