Skip to main content
Research article - Peer-reviewed, 2021

The Plot Thickens: Haploid and Triploid-Like Thalli, Hybridization, and Biased Mating Type Ratios in Letharia

Ament-Velásquez, Sandra Lorena; Tuovinen, Veera; Bergström, Linnea; Spribille, Toby; Vanderpool, Dan; Nascimbene, Juri; Yamamoto, Yoshikazu; Thor, Göran; Johannesson, Hanna


The study of the reproductive biology of lichen fungal symbionts has been traditionally challenging due to their complex lifestyles. Against the common belief of haploidy, a recent genomic study found a triploid-like signal in Letharia. Here, we infer the genome organization and reproduction in Letharia by analyzing genomic data from a pure culture and from thalli, and performing a PCR survey of the MAT locus in natural populations. We found that the read count variation in the four Letharia specimens, including the pure culture derived from a single sexual spore of L. lupina, is consistent with haploidy. By contrast, the L. lupina read counts from a thallus' metagenome are triploid-like. Characterization of the mating-type locus revealed a conserved heterothallic configuration across the genus, along with auxiliary genes that we identified. We found that the mating-type distributions are balanced in North America for L. vulpina and L. lupina, suggesting widespread sexual reproduction, but highly skewed in Europe for L. vulpina, consistent with predominant asexuality. Taken together, we propose that Letharia fungi are heterothallic and typically haploid, and provide evidence that triploid-like individuals are hybrids between L. lupina and an unknown Letharia lineage, reconciling classic systematic and genetic studies with recent genomic observations.


lichens; heterothallism; mating type locus; ploidy; hybridization

Published in

Frontiers in fungal biology
2021, volume: 2, article number: 656386

Authors' information

Ament-Velásquez, Sandra Lorena
Uppsala University
Tuovinen, Veera
Uppsala University
Tuovinen, Veera
Swedish University of Agricultural Sciences, Department of Ecology
Bergström, Linnea
Uppsala University
Spribille, Toby
University of Alberta
Vanderpool, Dan
University of Montana
Nascimbene, Juri
University of Bologna
Yamamoto, Yoshikazu
Akita Prefectural University
Swedish University of Agricultural Sciences, Department of Ecology
Johannesson, Hanna
Uppsala University

UKÄ Subject classification

Biochemistry and Molecular Biology

Publication Identifiers

DOI: 10.3389/ffunb.2021.656386

URI (permanent link to this page)