Ecoevolutionary dynamics of the gut microbiota at the macroscale level, that is, in across-species comparisons, are largely driven by ecological variables and host genotype. The repeated explosive radiations of African cichlid fishes in distinct lakes, following a dietary diversification in a context of reduced genetic diversity, provide a natural setup to explore convergence, divergence and repeatability in patterns of microbiota dynamics as a function of the host diet, phylogeny and environment. Here we characterized by 16S rRNA amplicon sequencing the gut microbiota of 29 cichlid species from two distinct lakes/radiations (Tanganyika and Barombi Mbo) and across a broad dietary and phylogenetic range. Within each lake, a significant deviation between a carnivorous and herbivorous lifestyle was found. Herbivore species were characterized by an increased bacterial taxonomic and functional diversity and converged in key compositional and functional community aspects. Despite a significant lake effect on the microbiota structure, this process has occurred with remarkable parallels in the two lakes. A metabolic signature most likely explains this trend, as indicated by a significant enrichment in herbivores/omnivores of bacterial taxa and functions associated with fiber degradation and detoxification of plant chemical compounds. Overall, compositional and functional aspects of the gut microbiota individually and altogether validate and predict main cichlid dietary habits, suggesting a fundamental role of gut bacteria in cichlid niche expansion and adaptation.

Hermann's tortoise (Testudo hermanni), the best‐known western Palaearctic tortoise species, has a rare natural distribution pattern comprising the Mediterranean areas of the Iberian, Apennine, and Balkan Peninsulas, as well as Sicily, Corsica and Sardinia. The western part of this range is traditionally considered habitat for T. h. hermanni, while T. h. boettgeri occurs in the Balkans. Taxonomy of this tortoise has been challenged in recent years, with the two subspecies being considered full species and the central Dalmatian populations of T. h. boettgeri being considered a third species, T. hercegovinensis. Using an mtDNA fragment approximately 1150 bp long (cytochrome b gene and adjacent portion of tRNA‐Thr gene), we investigated mtDNA diversity with regard to contrasting concepts of two subspecies or three species. Seven closely related haplotypes were identified from the western Mediterranean and 15 different, in part much‐differentiated, haplotypes from the Balkans. Western Mediterranean haplotypes differ from Balkan haplotypes in 16–42 mutation steps. One to seven mutation steps occur within western Mediterranean populations. Balkan haplotypes, differing in 1−37 nucleotides, group in parsimony network analysis into three major assemblages that display, in part, a similar degree of differentiation to that of western Mediterranean haplotypes relative to Balkan haplotypes. Rates of sequence evolution are different in both regions, and low divergence, palaeogeography and the fossil record suggest a slower molecular clock in the western Mediterranean. While monophyly in western Mediterranean haplotypes is well‐supported, conflicting evidence is obtained for Balkan haplotypes; maximum parsimony supports monophyly of Balkan haplotypes, but other phylogenetic analyses (Bayesian, ML, ME) indicate Balkan haplotypes could be paraphyletic with respect to the western Mediterranean clade. These results imply a process of differentiation not yet complete despite allopatry in the western Mediterranean and the Balkans, and suggest all populations of T. hermanni are conspecific. In the western Mediterranean no clear geographical pattern in haplotype distribution is found. Distribution of Balkan haplotypes is more structured. One group of similar haplotypes occurs in the eastern Balkans (Bulgaria, Republic of Macedonia, Romania and the Greek regions Evvia, Macedonia, Peloponnese, Thessaly and Thrace). Two distinct haplotypes, differing in eight to nine mutation steps from the most common haplotype of the first group, are confined to the western slope of the Taygetos Mts. in the Peloponnese. Yet another group, connected over between four and 23 mutation steps with haplotypes of the eastern Balkan group, occurs along the western slope of the Dinarid and Pindos Mts. (Istria, Dalmatia, western Greece). Taygetos haplotypes are nested within other haplotypes in all phylogenetic analyses and support for monophyly of the other Balkan groups is at best weak. We conclude that using the traditional two subspecies model should be contin...

No abstract

No abstract