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Morphological evolution of Stephanodiscus (Bacillariophyta) in Lake Biwa from a 300 ka fossil record

Megumi Saito-Kato, Yoshihiro Tanimura, Shinobu Mori and Matthew L. Julius
Morphological evolution of Stephanodiscus (Bacillariophyta) in Lake Biwa from a 300 ka fossil record
Journal of Micropalaeontology (July 2015) 34 (2): 165-179


A series of intermittent changes in Stephanodiscus (Bacillariophyta) valve morphology was observed in sediment core materials collected from Lake Biwa, Japan. A constant sedimentation rate reveals a continuous but punctuated pattern of morphological evolution. Morphological parameters, including maximum diameter and fascicle number v. diameter ratio (fascicle density), showed long periods of stasis and less than 10 000-year directional changes. Specifically, directional decreases in fascicle density occurred at 200-190 and 160-150 ka, and increases in maximum diameter occurred at 130-120 ka. According to a morphology-based species definition, a non-branching phylogenetic lineage originating from a cosmopolitan ancestor can be presumed from a morphology-based cladistic analysis and the biostratigraphic record. Evolutionary modes were selected from directional change, random walk, stasis and combined models by a statistical test, paleoTS, to clarify that the sequential changes are composed of relatively long stasis modes and short directional change modes. Global climate change was probably an influence during the early stages of the history of Lake Biwa.

ISSN: 0262-821X
EISSN: 2041-4978
Serial Title: Journal of Micropalaeontology
Serial Volume: 34
Serial Issue: 2
Title: Morphological evolution of Stephanodiscus (Bacillariophyta) in Lake Biwa from a 300 ka fossil record
Affiliation: National Museum of Nature and Science, Department of Geology and Paleontology, Tsukuba, Japan
Pages: 165-179
Published: 201507
Text Language: English
Publisher: British Micropalaeontological Society, London, United Kingdom
References: 50
Accession Number: 2015-085002
Categories: Paleobotany
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes 3 appendices
Illustration Description: illus. incl. 1 plate, 2 tables, sketch map
N35°01'60" - N35°32'60", E135°49'60" - E136°16'00"
Secondary Affiliation: Saint Cloud State University,
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 201536
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