期刊
PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES
卷 280, 期 1768, 页码 -出版社
ROYAL SOC
DOI: 10.1098/rspb.2013.1708
关键词
palynology; polyploidy; Cheirolepidiaceae; evolution; mass extinctions
资金
- board of Utrecht University
- Marie Curie International Incoming Fellowship, within the 7th European Community Framework Programme [PIIF-GA-2012-328245]
Polyploidy (orwhole-genome doubling) is a keymechanismfor plant speciation leading to new evolutionary lineages. Several lines of evidence show that most species among flowering plants had polyploidy ancestry, but it is virtually unknown for conifers. Here, we study variability in pollen tetrad morphology and the size of the conifer pollen type Classopollis extracted from sediments of the Triassic-Jurassic transition, 200 Ma. Classopollis producing Cheirolepidiaceae were one of the most dominant and diverse groups of conifers during the Mesozoic. We show that aberrant pollen Classopollis tetrads, triads and dyads, and the large variation in pollen size indicates the presence of unreduced (2n) pollen, which is one of the main mechanisms in modern polyploid formation. Polyploid speciation may explain the high variability of growth forms and adaptation of these conifers to different environments and their resistance to extreme growth conditions. We suggest that polyploidy may have also reduced the extinction risk of these conifers during the End-Triassic biotic crisis.
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