Cryptic diversity and symbiont interactions in rock-posy lichens

Abstract

Identifying factors that influence species interactions is central to research in symbiotic systems. While lichens represent iconic models of symbiosis and play important roles in understanding the biology of symbiotic interactions, patterns of interactions in lichen symbionts and mechanisms governing these relationships are not well characterized. This is due, in part to the fact that current taxonomic approaches for recognizing diversity in lichen symbionts commonly fail to accurately reflect actual species diversity. In this study, we employed DNA-based approaches to circumscribed candidate species-level lineages in rock-posy lichen symbionts (mycobiont=Rhizoplaca s. lat. species; photobiont=Trebouxia species). Our results revealed a high degree of cryptic diversity in both the myco- and photobionts in these lichens. Using the candidate species circumscribed here, we investigated the specificity of the symbionts toward their partners and inferred the relative importance of various factors influencing symbiont interactions. Distinct mycobiont species complexes, ecozones, and biomes are significantly correlated with the occurrence of photobiont OTUs, indicating that complex interactions among mycobiont lineages, ecogeography, and microhabitat determine interactions between photobionts and their mycobionts in lichen symbiosis. One-to-one specificity between mycobiont and photobiont species was not found, with the exception of R. maheui that associated with a single Trebouxia OTU that was not found with other Rhizoplaca s. lat. species. We estimated the most recent common ancestor of the core Rhizoplaca group at c. 62.5Ma, similar in age to the diverse parmelioid core group in the well-studied family Parmeliaceae. However, in contrast to Parmeliaceae, species in Rhizoplaca were found to associate with a narrow range of photobionts. Our study provides important perspectives into species diversity and interactions in iconic lichen symbiotic systems and establishes a valuable framework for continuing research into rock-posy lichens.

The complexity of symbiotic interactions influences the ecological amplitude of the host: A case study inStereocaulon(lichenized Ascomycota)

“…Moreover, Leavitt et al. () found multiple Trebouxia species‐level lineages at all studied sites, but their abundance varied considerably.…”

“…Lichens generally associate with multiple lineages belonging to a single photobiont genus. Indeed, a wide range of Trebouxia lineages are phycobionts of species belonging to various lichen genera, for example, Protoparmelia , Rhizoplaca , Tephromela, Xanthoparmelia, Xanthoria and Xanthomendoza (Leavitt et al., , ; Muggia et al., ; Muggia, Leavitt, & Barreno, in press; Nyati et al., ), and high infrageneric diversity of Asterochloris phycobionts has also been observed in species of Cladonia (Bačkor et al., ; Beiggi & Piercey‐Normore, ; Piercey‐Normore & DePriest, ; Škaloud & Peksa, ; Yahr et al., ) and Lepraria (Nelsen & Gargas, , ; Peksa & Škaloud, ; Škaloud & Peksa, ). It is an interesting fact that only a few other lichens, which have crustose growth and (generally) a poorly developed cortex (Helms, ; Thüs et al., ), are known to build their thalli with phycobionts belonging to different Trebouxiophycean genera ( Lepraria borealis , Engelen, Convey, & Ott, ; Micarea , Yahr et al., ; Bagliettoa and Verrucaria nigrescens , Thüs et al., ; Voytsekhovich & Beck, ; Diploschistes muscorum , Wedin et al., ).…”

“…Previous ecological studies on lichen phycobionts focused mainly on the type of growth substrate (Bačkor et al., ; Leavitt et al., ; Muggia et al., ). Several studies have investigated the effects of various climatic conditions (Fernández‐Mendoza et al., ; Grande et al., ; Leavitt et al., ; Marini, Nascimbene, & Nimis, ; Peksa & Škaloud, ; G. Singh et al., ). As of late, Rolshausen, Dal Grande, Sadowska‐Deś, Otte, and Schmitt () described mutualist‐mediated climatic niche expansion.…”

“…Previous ecological studies on lichen phycobionts focused mainly on the type of growth substrate (Bačkor et al, 2010;Leavitt et al, 2013;Muggia et al, 2014). Several studies have investigated the effects of various climatic conditions (Fernández-Mendoza et al, 2011;Grande et al, 2017;Leavitt et al, 2016;Marini, Nascimbene, & Nimis, 2011;Peksa & Škaloud, 2011;G. Singh et al, 2017).…”

Characterization of microsatellite markers in the cosmopolitan lichen-forming fungus Rhizoplaca melanophthalma (Lecanoraceae)

“…(Leavitt et al 2011(Leavitt et al , 2013(Leavitt et al , 2016b, many of which occur in sympatry in Western North America. In Western North America the distribution area of these species extends from the northern boreal zone to Mexico along the Rocky Mountains with a center of diversity in the Great Basin region (Leavitt et al 2011).…”