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- Title
Combining geometric morphometrics, molecular phylogeny, and micropaleontology to assess evolutionary patterns in Mallomonas (Synurophyceae: Heterokontophyta).
- Authors
Siver, P. A.; Wolfe, A. P.; Rohlf, F. J.; Shin, W.; Jo, B. Y.
- Abstract
Synurophytes, also known as scaled chrysophytes, are ecologically important algae that produce an array of siliceous structures upon which their taxonomy is based. Despite occupying a key position within the photosynthetic heterokonts, the evolutionary history of synurophytes remains poorly constrained. Here, modern and Middle Eocene siliceous scales of the morphotaxon Mallomonas insignis are used as a model to investigate synurophyte evolutionary patterns. Structural details of scale morphology were examined comparatively with scanning electron microscopy and scored for geometric morphometric analyses to assess the stability of shape characters. Although consistent size differences exist (modern scales are larger than Eocene counterparts), the populations cannot be differentiated on the basis of shape or microstructural detail, implying considerable evolutionary stasis in scale morphology. A time-calibrated relaxed molecular clock analysis using a three-gene concatenated data set (27 strains) suggests that the M. insignis lineage predates the available fossil record, having diverged from closest congeneric taxa in the Cretaceous (≥94 Ma). However, the molecular analysis also implies that considerable genetic variability is present within several morphotaxa of Mallomonas, implying that substantial genetic variability has arisen despite the retention of uniform scale morphologies, and resulting in the widespread occurrence of cryptic taxa. Results from the synurophyte lineage are consistent with the notion of protracted ghost ranges (>10 Ma) implied by the molecular phylogenies of other algal groups, together pointing to the paucity of the fossil record of these organisms on these timescales.
- Subjects
CHRYSOPHYTES; ALGAE; TAXONOMY; MOLECULAR phylogeny; MICROPALEONTOLOGY; MALLOMONAS; HETEROKONTOPHYTA
- Publication
Geobiology, 2013, Vol 11, Issue 2, p127
- ISSN
1472-4677
- Publication type
Article
- DOI
10.1111/gbi.12023