Saxiloba: a new genus of placodioid lichens from the Caribbean and Hawaii shakes up the Porinaceae tree (lichenized Ascomycota: Gyalectales)

Abstract

The new genus Saxiloba is described with the two species S. firmula from the Caribbean and S. hawaiiensis from Hawaii. Saxiloba is characterized by a unique, placodioid thallus forming distinct lobes, growing on rock in shaded to exposed situations with a trentepohlioid photobiont and a fenestrate thallus anatomy with distinct surface lines. The material is often sterile, but Porina-like perithecia and ascospores had previously been described for the Caribbean taxon and were here confirmed for both species. Molecular sequence data also confirmed placement of this lineage in Porinaceae. Its position within that family supports the notion that Porinaceae should be subdivided into a larger number of genera than proposed in previous classification attempts. Compared to other Porinaceae, Saxiloba exhibits a unique morphology and anatomy that recalls taxa in the related family Graphidaceae and it substantially expands the known phenotypic variation within Porinaceae. The two recognized species are similar in overall morphology but, apart from their disjunct distribution and different substrate ecology, differ in lobe configuration, color and disposition of the crystal clusters and resulting surface patterns.

Unravelling the diversity of the lichen genus Porina (Porinaceae) in Mauritius

“…P. dolichophora and P. exasperatula (= P. dolichophora clade sensu Sobreira et al (2018)), but it belongs to the P. simulans-P. epiphylla clade (= Phylloporina clade sensu Sobreira et al (2018)). Moreover, the genus Saxiloba is represented by the single species sequenced so far, but instead of forming its own rather distinct lineage as shown in the original description of this genus (Lücking et al 2020), it is part of a strongly supported lineage with saxicolous and corticolous Porina species having crustose and non-lobate thalli (e.g. P. nuculoides and P. rupicola).…”

“…Liu "Taxonomic study of the lichen genus Porina Ach. from Chinese mainland"), with others from Baloch et al (2010), Diederich & Ertz (2020), Ertz et al (2019), Grube et al (2004), Lücking et al (2020), Miadlikowska et al (2014), andSobreira et al (2018) in order to include an exhaustive list of taxa belonging to the family Porinaceae and the genus Porina s.l. The sequences were aligned using MAFFT v.7.402 (Katoh et al 2002) on the CIPRES Web Portal (Miller et al 2010) and manually corrected for errors using Mesquite v.3.04 (Maddison & Maddison 2015).…”

“…Hafellner & Kalb 1995;Harris 1995;Malcolm & Vězda 1995). Two new genera were even recently described, based mainly on the thallus type in combination with molecular data: flabelliform squamules for the genus Flabelloporina Sobreira, M.Cáceres & Lücking and placodioid thallus with a fenestrate anatomy for the genus Saxiloba Lücking, Moncada & Viñas (Sobreira et al 2018;Lücking et al 2020). However, a splitting of the Porinaceae in small generic entities has not been widely accepted because characters are often shared between genera and are highly variable (e.g.…”

“…A generic rearrangement or at least a subgeneric arrangement of the Porinaceae could be possible but requires analyses supported by molecular data and a more complex combination of morphological characters instead of the previous rather schematic treatments (Lücking 2008: 271). A possible generic concept for Porinaceae was outlined using a molecular phylogeny, but the results were based on a single marker, the mtSSU (Sobreira et al 2018;Lücking et al 2020).…”

Further expansion of morphological variability in the Porinaceae (Ascomycota, Ostropales) with the placement of the enigmatic genus Gallaicolichen

“…After confirmation of the newly generated sequences as members of the Porinaceae, a dataset of mtSSU sequences was assembled for resolving the exact placement of the newly sequenced taxa in a broader phylogeny of the family Porinaceae. Sequences retrieved from GenBank were selected mainly from previous studies of the family (Sobreira et al 2018;Lücking et al 2020;Ertz & Diederich 2022;Sanders et al 2023), for a total of 122 sequences in the matrix. Four accessions of Coenogonium were selected as outgroup.…”