Molecular, morphological, and ecological differences between the terrestrial and aquatic forms of Oxyrrhynchium speciosum (Brid.) Warnst. (Brachytheciaceae)

Abstract

Oxyrrhynchium speciosum (Brid.) Warnst. is a relatively uncommon moss that can be found in wetland habitats across Europe and New Zealand. In this paper, we address the morphological, molecular and ecological relationships between the aquatic form of O. speciosum discovered in a deep, Chara-dominated lake (Budzisławskie, NW Poland) and its terrestrial relatives. Morphological assessments revealed a considerable difference between terretrial and deep-water samples of O.speciosum. The aquatic form of O. speciosum was, on average, 12 times larger, with more branched stems (4–30 times) and longer leaves (1–2 times).

Investigation of ITS1-5·8S-ITS2-26S region sequences, however, revealed no distinction between the terrestrial and aquatic forms. An analysis of the ecological data suggests that the presence of O. speciosum in deep lake habitats is not incidental (as with many land species developing in aquatic environments). On the contrary, aquatic forms have a distinct ecological niche. Our results confirm that both forms of O. speciosum are closely related to O. hians (Hedw.) Loeske (a terrestrial species). The data indicate that O. speciosum is nested within a well-supported O. hians clade and separation of these species may be connected with polyploidization that occurred during their evolution.

Keywords:

• Aquatic mosses
• Aquatic vegetation
• Chara-dominated lakes
• Habitat
• Molecular phylogeny
• Oxyrrhynchium hians
• Oxyrrhynchium speciosum

Acknowledgements

The authors are grateful to Dr J.E. Beever and Dr E.K. Cameron, Curator of AK, for providing the material from Lake Wanaka and to Prof. L. Hedenäs and Prof. A. Tehler, Curators of S, for providing the specimen from Storsjön. We thank Prof. Ryszard Ochyra (Institute of Botany, Polish Academy of Sciences) for help in identification of Oxyrrhynchium species and the assessment of their morphological features and Krystyna Strycharczuk for advice on determining ploidy level by flow cytometry. Many thanks to Dr M. Kelly (University of Newcastle, UK) whose comments helped to improve both the scientific content and language of the manuscript. The study was (partially) supported by a grant from the Polish Ministry of Science and Higher Education (No.304 100 31/32623) and application research of monitoring Lake Budzisławskie.

Taxonomic Additions and Changes: Nil