Abstract Detail

Bryology and Lichenology

Keuler, Rachel A [1], Garretson, Alexis [1], Saunders, Theresa [1], Erickson, Robert [1], St. Andre, Nathan [1], Grewe, Felix [2], Smith, Hayden [3], Lumbsch, Helge [4], St Clair, Larry [5], Leavitt, Steven [1].

Genome-scale data reveal the potential roleof hybrid speciation in lichen-forming fungi.

Advancements in molecular genetics have revealed that hybridization is common among plants, animals, and fungi, playing an important role in evolutionary dynamics and speciation. One genetic indicator of hybridization is the discordance between mitochondrial and nuclear phylogenetic trees. While hybridization has been well-documented in plant pathogenic fungi, the effects of this process on species boundaries in lichenized fungi are largely unexplored. Here we investigated the potential role of hybridization on the emergence of morphologically and reproductively distinct asexual vagrant lichen forms within a clade of rock-dwelling, sexually reproducing species, the Rhizoplaca melanophthalma group. We used phylogenomic data from both mitochondrial and nuclear genomes representing all known species within the R. melanophthalma complex to infer evolutionary relationships and potential hybridization/introgression. We inferred strongly supported phylogenies from both the nuclear and mitochondrial datasets, both recovering multiple independent origins of vagrant Rhizoplaca populations. We observed multiple instances of discordance between the mitochondrial and nuclear trees, including the clade comprising the asexual vagrant species R. haydenii, R. idahoensis, and a closely related rock-dwelling lineage. In spite of well-supported phylogenies, both from a concatenated super matrix approach and multiple coalescent-based species tree approaches, we recovered strong evidence of reticulation using a network approach that incorporates both incomplete lineage sorting and hybridization. These data suggest that the western North American subalpine endemic R. shushanii is likely the result of a hybrid speciation event, and hybridization may have also played a role in other taxa, including vagrant lineages. Here we provide novel perspective into the role of hybridization/introgression in the process of speciation in lichen-forming fungi based on genome-scale data. We discuss potential roles of hybridization/introgression in terms of generating novel traits in lichens. Furthermore, our results support the need for considering reticulate phylogenies when investigating species boundaries and evolutionary history, even in cases with well-supported topologies inferred from genome-scale data.

1 - Brigham Young University, Biology, 800 N 580 E St, Provo, UT, 84606, United States
2 - Field Museum, 1400 S Lake Shore Dr., Chicago, IL, 60605, United States
3 - Brigham Young University, 800 N 580 E St, Provo, UT, 84606, United States
4 - Department Of Botany, 1400 S. Lake Shore Drive, Chicago, IL, 60605, United States
5 - 193 Mlbm, Provo, UT, 84602, United States

Keywords:
Lichens
hybridization
phylogeny
evolution
speciation
DNA.

Presentation Type: Oral Paper
Session: BL, Bryology/Lichenology combined session
Location: Tucson G/Starr Pass
Date: Tuesday, July 30th, 2019
Time: 2:45 PM
Number: BL005
Abstract ID:190
Candidate for Awards:A. J. Sharp Award