Deep Divergence between Island Populations in Lichenized Fungi

Macaronesia is characterized by a high degree of endemism and represents a noteworthy system to study the evolutionary history of populations and species. Here, we compare the population-genetic structure in three lichen-forming fungi, the widespread Lobaria pulmonaria and two Macaronesian endemics, L. immixta and L. macaronesica, based on microsatellites. We utilize population genetic approaches to explore population subdivision and evolutionary history of these taxa on the Canary Islands, Madeira, Azores, and the western Iberian Peninsula. A common feature in all species was the deep divergence between populations on the Azores, a pattern expected by the large geographic distance among islands. For both endemic species, there was a major split between archipelagos. In contrast, in the widespread L. pulmonaria, divergent individuals were distributed across multiple archipelagos, suggesting a complex evolutionary history involving repeated migration between islands and mainland.

Methods
The genotyping of microsatellites followed Werth et al. (2014). Fragment analyses were run on an automated capillary sequencer (3730xl DNA Analyzer, Life Technologies, Rotkreuz). Alleles were genotyped with an internal size standard (LIZ500) using GeneMapper version 3.7 (Life Technologies, Rotkreuz).

Reference

Werth S, Cheenacharoen S, Scheidegger C (2014) Propagule size is not a good predictor for regional population subdivision or fine-scale spatial structure in lichenized fungi. Fungal Biology 118:126-138. doi:10.1016/j.funbio.2013.10.009