Abstract Detail

Paleobotanical Section

Bippus, Alexander Cole [1], Stockey, Ruth A. [2], Rothwell, Gar W. [3], Tomescu, Alexandru M.F. [4].

Phylogenetic relationships in the Polytrichaceae (Bryophyta): a morphology-based approach.

Phylogenetic studies place the Polytrichaceae as an early divergent lineage within Bryophyta (mosses), yet the pre-Cenozoic fossil record of the family consists of only one fossil from the Late Cretaceous. Expanding this sparse fossil record, a new polytrichaceous moss from the Early Cretaceous (136 Ma) Apple Bay locality (Vancouver Island, Canada) represents the oldest unequivocal record of Polytrichaceae and has spurred re-assessment of phylogenetic relationships within this family, based on morphology. The fossil moss has typical polytrichaceous features including leaves with sheathing bases and narrower blade, bearing adaxial lamellae, and well-developed conducting tissues. A bistratose lamina with an adaxial layer of mammillose cells and lamellae restricted to the costa characterize the extant genera Alophosia, Lyellia, and Bartramiopsis, which form a basal grade within Polytrichaceae. The small size, gemmae cups, and abaxially toothed lamina of the Apple Bay moss are similar to those of Alophosia, which is considered the basal-most lineage in the family. The morphological similarity of the Apple Bay moss with genera considered basal in the family and its stratigraphic position suggest that integrating this fossil into phylogenetic analyses may inform understanding of basal relationships in Polytrichaceae. The phylogeny of Polytrichaceae has been approached previously using gene sequences and morphology, the former producing coherent hypotheses of relationships while the latter has yielded low resolution. To assess the position of the Apple Bay moss, we assembled a morphological matrix for all extant genera in the family (18 genera, 36 species) and two fossils (Eopolytrichum and the Apple Bay moss), by optimizing characters used in previous analyses and adding new discrete and continuous characters (used for the first time in this group), to a total of more than 90 characters. Tree searches reveal that this dataset produces good phylogenetic resolution, many genera being recovered as monophyletic. In trees rooted with Tetraphis and Sphagnum, the Apple Bay moss groups with Alophosia and Lyellia in a clade that does not occupy a basal position. However, in unrooted networks, the Apple Bay moss groups with the unlikely combination Bartramiopsis and Dendroligotrichum. These results, as well as paraphyly or polyphyly of some genera (Lyellia, Pogonatum, Polytrichum, Notoligotrichum, Oligotrichum) highlight a need for reassessment of hypotheses of homology and character partitioning. Additionally, they also reveal a strong effect on tree topology of outgroup selection (e.g. Sphagnum, traditionally used as an outgroup, represents a long branch), emphasizing the need for experimentation with alternative outgroups.

1 - Humboldt State University , Biological Sciences , 1 Harpst Street, Arcata , CA, 95521, USA
2 - Oregon State University, Department of Botany and Plant Pathology, 2082 Cordley Hall, Corvallis, OR, 97331, USA
3 - Oregon State University and Ohio University, Botany and Plant Pathology, 2082 Cordley Hall, Oregon State University, Corvallis, OR, 97331, US
4 - Humboldt State University, Department Of Biological Sciences, 1 Harpst Street, Arcata, CA, 95521, USA

Keywords:
fossil
moss
Polytrichaceae
Phylogeny
continuous characters 
morphology
Cretaceous
permineralized
Anatomy
outgroup.

Presentation Type: Oral Paper:Papers for Sections
Session: 1
Location: Salon 5/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 8:00 AM
Number: 1001
Abstract ID:589
Candidate for Awards:Isabel Cookson Award,Maynard F. Moseley Award