The symbiotic playground of lichen thalli - a highly flexible photobiont association in rock-inhabiting lichens

Abstract

The development of characteristic thallus structures in lichen-forming fungi requires the association with suitable photoautotrophic partners. Previous work suggests that fungi have a specific range of compatible photobionts and that selected algal strains are also correlated with the habitat conditions. We selected the rock-inhabiting crust lichen Protoparmeliopsis muralis, which exhibits high flexibility in algal associations. We present a geographically extended and detailed analysis of algal association patterns including thalli which host superficial algal colonies. We sampled 17 localities in Europe, and investigated the photobiont genotypic diversity within and between thalli and compared the diversity of intrathalline photobionts and externally associate algal communities between washed and unwashed thalli by single-strand conformation polymorphism analyses and ITS sequence data. The results show that (1) photobiont population within the lichen thalli is homogeneous; (2) multiple photobiont genotypes occur within single areoles and lobes of individual lichens; and (3) algal communities which superficially colonize the lichen thalli host taxa known as photobionts in unrelated lichens. Photobiont association patterns are extremely flexible in this ecologically versatile crust-forming lichen. We suggest that lichen surfaces represent a potential temporary niche for free-living stages of lichen photobionts, which could facilitate the establishment of further lichens in the proximal area.

Myrmecia israeliensis as the primary symbiotic microalga in squamulose lichens growing in European and Canary Island terricolous communities

“…. These results raise questions about the levels of specificity and the strategies followed by lichenized fungi to associate with a certain alga available in the substrate pool (Muggia et al 2013;Meessen & Ott, 2013;Williams et al 2017).…”

Unexpected associated microalgal diversity in the lichen Ramalina farinacea is uncovered by pyrosequencing analyses

“…The first half was vortexed 3 times for 5 min at 2000 rpm with Milli-Q sterile water; this water was kept and labeled HW (H 2 O washing). The second half was washed as described by Muggia et al [23] using a 1% solution of Tween80 in distilled sterile water; this washing water was also kept and labeled MW (Muggia washing).…”

“…Two thalli of Ramalina farinacea (thallus A and B) were first rehydrated for 24 h. Thallus A was divided at the base into two halves: the first was washed with sterile water (HW), and the second was treated as described by Muggia et al [23] (MW). The two halves were paralleled and divided into three sections: an apical zone (A), a middle zone (M) and a basal zone (B).…”

“…Although 454 pyrosequencing has been already surpassed by other NGS approaches, it still represents a powerful and complementary approach to the traditional Sanger sequencing or fingerprinting techniques for biodiversity assessments. Several authors have also uncovered the promiscuity of phycobionts associated with lichen thalli using analyses of conformation polymorphism of the ITS fragments [11,23], microsatellites [24], and microscopic examinations [6,25]. Because high-throughput sequencing (HTS) allows the detection of a vast number of genotypes, which otherwise remain underestimated with conventional PCR amplifications [26], meta-community studies represent a potential tool to address questions about lichen phycobiont populations and their interactions with the surrounding environments [27].…”

Coordinated ultrastructural and phylogenomic analyses shed light on the hidden phycobiont diversity of Trebouxia microalgae in Ramalina fraxinea

“…Recent developments in DNA-based sequence delimitation of species boundaries in algae have been recently discussed (Leliaert et al, 2014). At present, nrITS sequences continue to be the most commonly used molecular markers for phylogenetic reconstructions among lichen microalgae (Muggia et al, 2013;Nelsen and Gargas, 2008;Piercey-Normore, 2006;Škaloud and Peksa, 2010). However, molecular studies based solely on algal nrITS sequences, sometimes lead to an Fig.…”