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Published on: July 28, 2017
Phylogenetic analyses of "higher" Hamamelididae based on plastid sequence data
American Journal of Botany
|June 29, 2011
Summary
Phylogenetic analysis of chloroplast DNA reveals distinct evolutionary paths for "higher" Hamamelididae. Nothofagus is basal, with Fagaceae sister to wind-pollinated core hamamelids, suggesting new ordinal classifications.
Area of Science:
- Botany
- Evolutionary Biology
- Molecular Phylogenetics
Background:
- The
- higher
- Hamamelididae represent a diverse group of flowering plants with complex evolutionary histories.
- Previous classifications have been challenged by molecular data.
Purpose of the Study:
- To resolve phylogenetic relationships within the
- higher
- Hamamelididae using chloroplast DNA sequences.
- To investigate the evolutionary origins of key morphological traits, such as the cupule.
Main Methods:
- Phylogenetic analysis of chloroplast DNA matK gene sequences (approximately 1 kilobase) from 21 species and related outgroups.
- Parsimony analysis to construct a phylogenetic tree based on 258 informative nucleotide sites.
Main Results:
- A single most parsimonious tree identified three well-supported monophyletic groups.
- Nothofagus was found to be basal to the remaining
- higher
- hamamelids.
- Fagaceae was sister to a clade of core
- higher
- hamamelids characterized by wind-pollination and reduced pollen apertures.
- Three subclades within the core group were resolved: Myricaceae, (Casuarina-(Ticodendron-(Betulaceae))), and (Rhoiptelea-Juglandaceae).
Conclusions:
- The basal position of Nothofagus aligns with fossil evidence, supporting its exclusion from Fagaceae.
- Two hypotheses for cupule origin are proposed: ancestral origin with subsequent loss or independent origins.
- Reclassification of three clades (Nothofagaceae; Fagaceae; Juglandaceae, Rhoiptelea, Myricaceae, Casuarina, Ticodendron, and Betulaceae) at the ordinal level is suggested, abandoning traditional orders like Fagales.
- Chloroplast DNA matK sequences offer greater phylogenetic resolution and a higher consistency index compared to rbcL sequences for this group.
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