Abstract Detail

Bryology and Lichenology

Otero, Ana [1], Lumbsch, Helge Thorsten [2], Grewe, Felix [3].

Revisiting species-pair concept in genus Usnea (Parmeliaceae, Ascomycota).

Species-pairs have been the subject of extensive discussions in lichenology since the original hypothesis by Du Rietz (1924). As originally proposed in this paper, the production of soredia and isidia versus apothecia are the only systematic differences in considering two taxa as a species-pair. Moreover, the author mentioned that sterile and fertile taxa may differ in their ecology, thus regarding those with overlapping distributions to the taxonomical rank of variety. Since first mentioned in the literature, the concept has been broadened and adapted by many authors, and even other terminologies have been used, such as counterparts species (Hale, 1965). Some authors have also argued that sorediate taxa would have to be derived from non-sorediate taxa, considering the former as evolutionary ends and downplaying the distribution ranges as a criteria for considering species pair (Poelt, 1963, 1970). The advent and improvement of methodologies such as chemical characterization and DNA sequencing have challenged the more conservative hypotheses. New studies showed the ability of sterile taxa to generate high levels of genetic variation (even greater than fertile counterparts) (Culberson, 1986; Schuster, 1985). Later, the breakthrough of modern molecular phylogenetic markers revolutionized systematics of lichen-forming fungi where the extremely high plasticity in morphological characters hindered the understanding of complex evolutionary histories and led to an underestimation of lineage differentiation (Lumbsch and Leavitt, 2011). Ultimately, Next Generation Sequencing (NGS) and particularly the more affordable reduced representation methods such as RAD-sequencing are being used to unveil speciation under complex scenarios such as adaptive radiations, incomplete lineage sorting, and hybridization (Andrews et al., 2016; Grewe et al., 2017).The genus Usnea, one of the most iconic beard-like macrolichens, comprises more than 600 spp. and is one of the largest genera of Parmeliaceae. The cosmopolitan nature of its lineages including some living in the most harsh terrestrial environments on both hemispheres, together with the exceptionally high intra-specific morphological variation (as shown by the numerous taxonomical treatments), makes this genus an ideal model to investigate extrinsic and intrinsic factors underlying complex evolutionary histories. Moreover, Usnea has several species pairs that were earlier described on either their morphology, chemistry, or by DNA genotyping. We used reference-based RADseq methodologies (successfully addressed previously, Grewe et al., 2018) to revisit four well-known species pair groups within Usnea: (a) U. intermedia/U. perplexans and U. florida/U. subfloridana occurring in the northern hemisphere and (b) U. trachycarpa/U. subantarctica and U. antarctica/U. aurantiaco-atra from the southern hemisphere. We conducted an integrative study combining morphological, chemical, ecological, and genomic approaches with the aim to shed light on the species delimitation of these four intriguing cases and ultimately to reconstruct how these taxa were derived taxonomically.

1 - The Field Museum, Grainger Bioinformatics Center, Science and Education, 1400 S DuSable Lake Shore Dr., Chicago, Illinois, 60605
2 - The Field Museum, Botany, 1400 S DuSable Lake Shore Dr, Chicago, Illinois, 60605, Estados Unidos
3 - The Field Museum, Grainger Bioinformatics Center, Science and Education, 1400 S Dusable Lake Shore Dr, Chicago, Illinois, 60605, Estados Unidos

Keywords:
Beard-like lichens
high-throughput sequencing  
species delimitation
speciation.

Presentation Type: Oral Paper
Number: BL1003
Abstract ID:655
Candidate for Awards:A. J. Sharp Award