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.

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

Allele frequency data of Lobaria immixta, L. macaronesica, and L. pulmonaria for six fungal microsatellite loci (LPu09, LPu15, LPu23, LPu24, LPu25, LPu28, Walser et al. 2003; Widmer et al. 2010) in each of 51 populations. Each entry represents the frequency of a given allele (row) in each population (column). Population names as in Table S1. Colored shading above population names refers to geographic regions or countries. Alleles are named by a combination of the locus name and allele length. Grey shading indicates populations where the endemic species (Lobaria immixta, L. macaronesica) did not occur.

References

Walser JC, Sperisen C, Soliva M, Scheidegger C (2003) Fungus-specific microsatellite primers of lichens: application for the assessment of genetic variation on different spatial scales in Lobaria pulmonaria. Fungal Genetics and Biology 40 (1):72-82. doi:10.1016/S1087-1845(03)00080-X

Widmer I, Dal Grande F, Cornejo C, Scheidegger C (2010) Highly variable microsatellite markers for the fungal and algal symbionts of the lichen Lobaria pulmonaria and challenges in developing biont-specific molecular markers for fungal associations. Fungal Biology 114:538-544. doi:10.1016/j.funbio.2010.04.003