Historical biogeography and phenotype‐phylogeny of Chroodiscus (lichenized Ascomycota: Ostropales: Graphidaceae)

Aim To analyse the historical biogeography of the lichen genus Chroodiscus using a phenotype‐based phylogeny in the context of continental drift and evolution of tropical rain forest vegetation. Location All tropical regions (Central and South America, Africa, India, Southeast Asia, north‐east Australia). Methods We performed a phenotype‐based phylogenetic analysis and ancestral character state reconstruction of 14 species of the lichen genus Chroodiscus, using paup * and mesquite ; dispersal–vicariance analysis (DIVA) and dispersal–extinction–cladogenesis (DEC) modelling to trace the geographical origin of individual clades; and ordination and clustering by means of pc‐ord , based on a novel similarity index, to visualize the biogeographical relationships of floristic regions in which Chroodiscus occurs. Results The 14 species of Chroodiscus show distinctive distribution patterns, with one pantropical and one amphi‐Pacific taxon and 12 species each restricted to a single continent. The genus comprises four clades. DIVA and DEC modelling suggest a South American origin of Chroodiscus in the mid to late Cretaceous (120–100 Ma), with subsequent expansion through a South American–African–Indian–Southeast Asian–Australian dispersal route and late diversification of the argillaceus clade in Southeast Asia. Based on the abundance of extant taxa, the probability of speciation events in Chroodiscus is shown to be extremely low. Slow dispersal of foliicolous rain forest understorey lichens is consistent with estimated phylogenetic ages of individual species and with average lengths of biological species intervals in fungi (10–20 Myr). Main conclusions The present‐day distribution of Chroodiscus can be explained by vicariance and mid‐distance dispersal through the interconnection or proximity of continental shelves, without the need for recent, trans‐oceanic long‐distance dispersal. Phylogenetic reconstruction and age estimation for Chroodiscus are consistent with the ‘biotic ferry’ hypothesis: a South American origin and subsequent eastward expansion through Africa towards Southeast Asia and north‐eastern Australia via the Indian subcontinent. The present‐day pantropical distributions of many clades and species of foliicolous lichens might thus be explained by eastward expansion through continental drift, along with the evolution of modern rain forests starting 120 Ma, rather than by the existence of a hypothetical continuous area of pre‐modern rain forest spanning South America, Africa and Southeast Asia during the mid and late Cretaceous.     

Seasonal variation of elemental status in the lichen Ramalina menziesii tayl. From two sites in southern California: Evidence for dry deposition accumulation

In southern California the lichen Ramalina menziesii was transplanted from a relatively unpolluted area to a highly polluted area for three periods over a year. During each period multi-element analyses of both water leachable extracts and residual fractions from the leached thallus were analyzed at 2-week intervals. Total concentrations were calculated by adding these two measurements. Total concentration of most elements did not exhibit distinct seasonal patterns but the higher concentrations exceeded background levels by factors of 1.3–3.7, depending on the element. In contrast, the elements in the leachates at the control and the polluted site exhibited distinct seasonal patterns with higher concentrations generally present in summer than in winter. High leachable concentrations were only found during dry periods, and consequently the leachable fraction was assumed to represent primarily dry deposition accumulation, particularly as the magnitude of the differences was higher at the polluted site. These elemental patterns reflected not only atmospheric deposition patterns, but also intracellular release of elements as injury occurred and to a lesser extent accumulation of marine aerosols and soil particulates.