Elucidating species richness in lichen fungi: The genusSticta(Ascomycota: Peltigeraceae) in Puerto Rico

Abstract

Traditional taxonomic studies provide only a limited understanding of species richness within a group. Their usefulness for assessing species diversity could also be limited as many lack sufficient sampling and/or fail to integrate different data types for assessing species boundaries. To explore the challenges and limitations of estimating species richness in lichens, we employed an integrative taxonomic approach to elucidate diversification patterns of the genus Sticta (Peltigeraceae) in Puerto Rico. Specimens were collected throughout the island, and a six‐locus dataset was generated to infer phylogenetic relationships among Puerto Rican Sticta and their continental counterparts. Phylogenetic analysis was combined with species delimitation methods and analysis of morpho‐anatomical characters to assess diversity patterns and clarify species‐level taxonomy. We found that Sticta is represented by 16 species in Puerto Rico and that at least 11 (69%) of them are potentially endemic to the island. We describe eight of these in this work: S. borinquensis sp. nov., S. corymbosa sp. nov., S. densiphyllidiata sp. nov., S. guilartensis sp. nov., S. harrisii sp. nov., S. parvilobata sp. nov., S. riparia sp. nov., and S. tainorum sp. nov. These species do not cluster in a monophyletic assemblage but are scattered over the broader Sticta phylogeny, indicating at least eight separate dispersal events. Putative endemic species were found to have close allies occurring in South America. Careful re‐examination of material revealed phenotypical characters that separate most species, suggesting low levels of cryptic diversity. We highlight that integrating molecular methods and other sources of information in species discovery along with comprehensive sampling efforts can greatly enhance our knowledge about diversity patterns in poorly studied groups and regions. Furthermore, species and ecosystems in the Caribbean are being threatened by substantial human‐driven changes (e.g., deforestation, climate change). Consequences of these impacts include reduction in already restricted habitats and potential extinction. We argue that studies analyzing species diversity within a phylogenetic framework could better inform conservation efforts aimed at addressing these challenges.

Species in lichen-forming fungi: balancing between conceptual and practical considerations, and between phenotype and phylogenomics

“…While reciprocal monophyly as an exclusivity criterion for species delimitation is intuitively appealing, metapopulation lineages may not be recovered as monophyletic of a number of reasons (Knowles and Carstens 2007), including incomplete lineage sorting in recently diverged species, introgression and hybridization (see below), porous or "semi-permeable" species boundaries, and other evolutionary scenarios (Joly et al 2009;Steenkamp et al 2018). Therefore, emerging lineages nested within a paraphyletic residual have been accepted as recently evolving species under certain circumstances (Wheeler and Nixon 1990;Crisp and Chandler 1996;Wheeler and Platnik 2000;Funk and Omland 2003;Freudenstein et al 2017;Mercado-Díaz et al 2020). It is further expected that diverging lineages also diverge in phenotype, including morphology, anatomy, chemistry, metabolism, and physiology, owing to either neutral mechanisms such as genetic drift, selective forces in diverging environments, selecting of sexual partners, or hybridization (Cohan and Hoffmann 1989;Harrington and Rizzo 1999;Grube and Kroken 2000;McGuigan et al 2005;Pfennig et al 2007;Mercader et al 2009;Schoustra et al 2012;Vigoder et al 2015;Ament-Velásquez et al 2020).…”

First records of Sticta weigelii s.str. from Bolivia confirmed by molecular data

“…Lobes are variously indented (Galloway, 1994(Galloway, , 1997(Galloway, , 2007Moncada, 2012;Moncada & Lücking, 2012;Moncada et al, 2014b). Until now, more than 200 species of Sticta have been described (Moncada & Lücking, 2012;Moncada et al, 2013aMoncada et al, , 2013bMoncada et al, , 2020Moncada et al, , 2021aMoncada et al, , 2021bLücking et al, 2017;Mercado-Díaz et al, 2020), but according to Moncada et al (2013bMoncada et al ( , 2021b the number of species belonging to this genus is more than twice as high. The discrepancy between the described and the potential number of Sticta species is related to the fact that in many countries no detailed studies have been undertaken.…”

“…The discrepancy between the described and the potential number of Sticta species is related to the fact that in many countries no detailed studies have been undertaken. For example, recent research conducted on Sticta in Puerto Rico revealed the presence of more than ten taxa potentially endemic to that island (Mercado-Díaz et al, 2020). Bolivia, conversely, is one of the relatively understudied countries in term of the presence of Sticta species.…”

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

“…In contrast, island lichen biota are generally considered low in endemism with rates estimated between 10% and 30% (Weber 1986;Eldredge & Miller 1995;Aptroot & Bungartz 2007;Smith 2013). However, recent molecular approaches and detailed morphological revisions suggest the opposite with endemism in lichen fungi often comparable to that of vascular plants (Moncada et al 2014(Moncada et al , 2017Bungartz et al 2016;Dal Forno et al 2017;Lücking et al 2017;Mercado-Díaz et al 2020).…”