ABSTRACT
The phylogenetic relationships of twelve species of Chauliognathus were investigated by studying the mitochondrial cytochrome oxidase I gene. A 678 bp fragment of the COI gene was sequenced to test the hypothesis that the Müllerian mimicry species of the "yellow-black" complex make up a monophyletic clade, separated from species with other colour patterns. The data set was analysed by neighbour-joining, maximum parsimony and maximum likelihood procedures. The results support a single origin of the yellow-black colour pattern during the evolution of the genus, with one main clade formed by Chauliognathus lineatus, C. tetrapunctatus, C. riograndensis, C. flavipes, C. octomaculatus, C. fallax, and another one formed by two species, C. expansus and C sp 1, plus an orange-black-coloured species. The nucleotide divergences found between C. sp 3 (black) and the other species studied fall within the level expected for species from different genera. The similarity of colour patterns of the yellow-black species has been considered an example of Müllerian mimicry by conservation of the ancestral state with some minor modifications.
Subject(s)
Animals , Coleoptera/genetics , DNA, Mitochondrial , Phylogeny , Polymorphism, Genetic , Base Sequence , Molecular MimicryABSTRACT
Beetles of the species Chauliognathus fallax Germar 1824 are polymorphic for elytron colouration with six morphs distinguished on the basis of black pigmentation on a yellow background. We investigated samples of C. fallax taken in eight consecutive weeks aiming to determine the frequency of the morphs which were grouped, for statistical analysis, into three classes according to elytra pigmentation as well as the possible occurrence of assortative mating. Our results showed a variation in the frequency of the classes throughout the season, both in males and females, with the maximum frequency of each class at the fourth and fifth week. The three classes (A, B, C) showed the same pattern of variation, and class B was always the more frequent. To test randomness of matings two approaches were taken: in the first, we compared the frequency of each class in copulating and non-copulating insects. In the second, the frequency of each class in the whole sample was taken as the probability of occurrence of the respective class; then, using the criterion of the probability of independent events we calculated the expected proportion of copulating insects for each pair of events. Both methods gave non-significant differences, suggesting that the matings were random.