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High levels of endemism among Galapagos basidiolichens

Abstract:

This study is a re-assessment of basidiolichen diversity in the Galapagos Islands. We present a molecular phylogenetic analysis, based on 92 specimens from Galapagos, using two nuclear ribosomal DNA markers (ITS and nuLSU). We also re-examined the morphology and anatomy of all sequenced material. The molecular results confirm our previous assessment that all Galapagos basidiolichens belong to the Dictyonema clade, which in Galapagos is represented by four genera: Acantholichen, Cora, Cyphellostereum, and Dictyonema. Most species previously reported from Galapagos in these genera were at the time believed to represent widely distributed taxa. This conclusion, however, has changed with the inclusion of molecular data. Although almost the same number of species is distinguished, the phylogenetic data now suggest that all are restricted to the Galapagos Islands. Among them, six species are proposed here as new to science, namely Cora galapagoensis, Cyphellostereum unoquinoum, Dictyonema barbatum, D. darwinianum, D. ramificans, and D. subobscuratum; and four species have already been described previously, namely Acantholichen galapagoensis, Cora santacruzensis, Dictyonema pectinatum, and D. galapagoense, here recombined as Cyphellostereum galapagoense. Our analysis is set on a very broad phylogenetic framework, which includes a large number of specimens (N = 826) mainly from Central and South America, and therefore strongly suggests an unusually high level of endemism previously not recognized. This analysis also shows that the closest relatives of half of the basidiolichens now found in Galapagos are from mainland Ecuador, implying that they reached the islands through the shortest route, with all species arriving on the islands through independent colonization events.