Abstract
We present phylogenetic analyses of the fruticose Ramalinaceae based on extensive collections from many parts of the world, with a special focus on the Vizcaíno deserts in north-western Mexico and the coastal desert in Namibia. We generate a four-locus DNA sequence dataset for accessions of Ramalina and two additional loci for Niebla and Vermilacinia. Four genera are strongly supported: the subcosmopolitan Ramalina, the new genus Namibialina endemic to SW Africa, and a duo formed by Niebla and Vermilacinia, endemic to the New World except the sorediate V. zebrina that disjunctly occurs in Namibia. The latter three genera are restricted to coastal desert and chaparral where vegetation depends on moisture from ocean fog. Ramalina is subcosmopolitan and much more diverse in its ecology.We show that Ramalina and its sister genus Namibialina diverged from each other at c. 48 Myrs, whereas Vermilacinia and Niebla split at c. 30 Myrs. The phylogeny of the fruticose genera remains unresolved to their ancestral crustose genera.Species delimitation within Namibialina and Ramalina is rather straightforward. The phylogeny and taxonomy of Vermilacinia are fully resolved, except for the two youngest clades of corticolous taxa, and support current taxonomy, including four new taxa described here. Secondary metabolite variation in Niebla generally coincides with major clades which are comprised of species complexes with still unresolved phylogenetic relationships. A micro-endemism pattern of allopatric species is strongly suspected for both genera, except for the corticolous taxa within Vermilacinia. Both Niebla and saxicolous Vermilacinia have chemotypes unique to species clades that are largely endemic to the Vizcaíno deserts.The following new taxa are described: Namibialinagen. nov. with N. melanothrix (comb. nov.) as type species, a single new species of Ramalina (R. krogiae) and four new species of Vermilacinia (V. breviloba, V. lacunosa, V. pustulata and V. reticulata). The new combination V. granulans is introduced. Two epithets are re-introduced for European Ramalina species: R. crispans (= R. peruviana auct. eur.) and R. rosacea (= R. bourgeana auct. p.p). A lectotype is designated for Vermilacinia procera. A key to saxicolous species of Vermilacinia is presented.
Highlights
Strong support is detected for the delimitation of two lineages for the fruticose genera: (1) Ramalina as sister to a strongly delimited group endemic to the coastal desert in SW Africa assigned to the new genus Namibialina, the relationship between the two genera being strongly supported; (2) two genera (Niebla and Vermilacinia), endemic to coastal deserts along the Pacific coast in the New World, strongly supported together and, further, sister to three species of Cliostomum, including the type species (C. corrugatum), but with weak support
One lineage contains two genera (Niebla + Vermilacinia) with all species but one restricted to coastal deserts of the New World subjected to oceanic fog and the other is divided into two genera, one (Namibialina) only with species with the same ecological requirements, but with a disjunct distribution (SW Africa) and the other (Ramalina) widely distributed throughout the world, with a basal species (R. sinensis) that is widespread throughout the Northern Hemisphere
We could not support this hypothesis with our dataset; only a rather small LSU sequence is available for that species that could complement the loci used in this study and its inclusion in our analysis resolved it at the base of the Niebla + Vermilacinia clade in an unsupported position
Summary
The genus is at the cutting edge of research about the very nature of lichenization as several species [mostly R. farinacea (L.) Ach.] have been shown to host and use several strains or even species of their green algal partners within the same thallus (Casano et al 2015; Catalá et al 2016; Moya et al 2017). The genus Ramalina is included in the well-supported Ramalinaceae s.l. together with well-known genera such as Bacidia De Not., Bacidina Vězda, Biatora Fr.: Fr., Bilimbia De Not., Lecania A. The remaining genera form a highly variable assemblage, a basal and poorly supported clade including Megalaria grossa (Pers. ex Nyl.) Haffellner and Lopezaria versicolor (Flot.) Kalb and Haffelner as sister to a much stronger supported clade, including Cliostomum griffithii (Sm.) Coppins and Vermilacinia cephalota (Tuck.) Spjut and Hale as sister to four accessions of Ramalina (Miadlikowska et al 2014)
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