This Special Issue is dedicated to Professor Pier Luigi Nimis on the occasion of his 70th birthday and retirement. It was our aim to publish papers addressing the three major research fields that Pier Luigi dealt with during his career: systematics and taxonomy, biomonitoring and ecology, and data resources and digitization. The papers in this Special Issue provide a vivid overview of the state of the art in the three research fields, and they reflect on Pier Luigi's outstanding contribution to lichenology. They offer a wide array of different methodologies, from the traditional approaches investigating lichen diversity and taxonomy by means of morpho-anatomical analyses, culture isolations and phylogenetic systematics, to the most modern sequencing techniques, and to the development of computer-aided tools and databases for facilitating lichen identification.
Pier Luigi was the promoter of lichen floristic and taxonomic research in Italy. There are 15 contributions centred on systematics and taxonomy. Many of these address diversity of the lichen mycobiont, including a description of the new genus Nimosora (Pérez-Ortega et al.), as well as papers resolving diversity and describing new species in Bacidia (Gerasimova et al.), Biatora (Palice et al.), Marchantiana (Søchting et al.), Peltigera (Miadlikowska et al.), Porina (Sanders et al.), Schaereria (Kantvilas) and Xanthoparmelia (Barcenas-Peña et al.). New lichen species are named in honour of Pier Luigi as Circinaria nimisii from Greece (Sohrabi et al.) and Coenogonium nimisii from Britain and Ireland (Malíček et al.). Two studies describe new species of lichenicolous fungi in Arthonia (Hafellner & Grube) and Tremella (Freire-Rallo et al.), including T. nimisiana. Further contributions deal with the taxonomy, phylogeny and biogeography of Lecidea atrobrunnea (Anantaprayoon et al.) and a nomenclatural analysis of Ramalina (Sipman & Ramírez Ordaya), and one contribution centres on the genetic diversity of Trebouxia in Punctelia (Garrido-Benavent et al.). Papers are sampled globally from both hemispheres, reaching from Australia and South Africa to northern Europe.
Pier Luigi also focused on biomonitoring and bioindication using lichens, while in recent years his interest centred on developing digital identification keys of lichens in many Italian regions and abroad. Four contributions in ecology and conservation address topics ranging from large-scale sampling of biodiversity patterns (Gheza et al.), including the effectiveness of the EU Habitats Directive (Frati & Brunialti), through the diversity and abundance of lithobiontic communities (Favero-Longo et al.), to the acclimation of individual species facing environmental change (Chinnery & Ellis). Papers on toolkits and databases include a presentation of the resource PhyloKey for lichen identification (Lücking et al.), and the presentation of database advances focused regionally on lichens in Ecuador (Yánez-Ayabaca et al.) and ethnolichenological information from Africa (Kinge et al.). There is an analysis of the reliability of iNaturalist (Munzi et al.), and a perspective on how urban lichens can contribute to biodiversity education projects (Zedda).
Together the contributed papers are a testimony of gratitude for a man who has devoted his entire life to lichenology and science.
Herewith, we also thank wholeheartedly all colleagues who served as reviewers of the contributed papers.
