Worlds within islands:

Deciphering the evolutionary mechanisms driving gut microbiome biogeography using an oceanic island system

We are very excited to announce that the American Genetic Association has awarded us with an Evolutionary, Ecological, or Conservation Genomics (EECG) grant for our research within the Fringilla team at the University of Oviedo.

Until recently, microbial taxa were largely considered cosmopolitan. Deep sequencing of microbial communities in diverse environments has revealed a more complex scenario, where dispersal is limited by suitable habitats and interspecific competition. In bacterial gut microbiomes, both host selection and high competition may restrict dispersal and drive biogeographical patterns. Gut bacterial communities often show congruent evolutionary histories with their hosts, which has led to the expectation that co-evolution is the main mechanism driving this pattern. This issue remains contentious, since distinguishing co-evolution from vicariance (due to selective pressure from shared biogeographical patterns) is challenging. We make use of the recent diversification of the Fringilla genus across the oceanic islands of Macaronesia as a natural experiment. Our project combines a replicated sampling with a multi-genomic dataset (1500 bp of the 16S region for bacterial profiling, DNA metabarcoding of diet composition, and genome wide profiling of the host) to infer the mechanisms driving gut microbiome diversification. The overall aims of this project are to discern: (i) the relative contribution of host genetic landscape and local environmental pressures in driving gut microbiome biogeographical patterns, and; (ii) to what extent these processes drive co-diversification.

Study sampling design of Fringilla sps. across Macaronesia. Sampling sites of the common chaffinch species complex (Fringilla spp.) are shown as red dots and sample sizes are in brackets next to location name. The sampling localities of the endemic and endangered Gran Canaria blue chaffinch (F. polatzeki) as well as the endemic and near threatened Tenerife blue chaffinch (F. teydea) are shown in blue along with sample sizes. The black arrows illustrate the known step-wise colonization history of F. coelebs from mainland Europe, to the Azores archipelago, followed by Madeira and ending in the Canary Islands (Recuerda et al. 2021). Note that the Fringilla genus is absent from the two large unsampled islands (Fuerteventura and Lanzarote) in the Canary Islands.

References:

Recuerda, M., J. C. Illera, G. Blanco, R. Zardoya, and B. Milá. 2021. Sequential colonization of oceanic archipelagos led to a species-level radiation in the common chaffinch complex (Aves: Fringilla coelebs). Mol. Phylogenet. Evol. 164:107291.