Maple Phylogeny

Taxonomy

1. Morphological characters diagnostic of maples:
- a. Trees and shrubs with oppositely arranged leaves
- b. Fruit a samara with asymmetric wing (keys)
2. Phylogenetic Position of Acer :
- Maples have been considered as a genus (Acer) in Aceraceae including Acer and Dipteronia (2 species). Morphological analyses have however shown that Aceraceae may be embedded within Sapindaceae (Judd et al. 1994). Molecular data seem to support the proposition; nevertheless, the support for the paraphyly of Sapindaceae with respect to Aceraceae is weak and the only fallout taxon from Sapindaceae is Xanthoceras, a monotypic genus in eastern Asia (Harrington et al. 2005). We need more evidence for the systematic position of Xanthoceras, which is important for testing the monophyly Sapindaceae and taxonomic treatment of Aceraceae.

3. Closest Relative of Acer :
- The most closely related taxon of Acer is Dipteronia, which is distributed in China, with two species. Dipteronia sinensis has a wide distribution in much of China, while D. dyeriana is narrowly distributed in Yunnan Province of southwestern China. Both species have pinnate compound leaves and samara with circular wings.

1. Pax, Ferdinand (1885): 110 species divided into I-VI groups based on relative position of nectary discs to stamens and further into 13 sections.

2. Rehder, Alfred (1905) recognized a segregate section from Pax’s section Lithocarpa.
3. Koizumi, Gen-Ichi (1911) erected five more new sections: Cissifolia, Parviflora, Carpinifolia, Palmatoidea, and Diabolica.
4. Nakai, Takenoshin (1915): proposed section Ginnala
5. Pojarkova, Antonina (1933)
6. Momotani, Yoshida (1962) based on chemical characters (above).
7. Ken Ogata (1967): Six groups and 25 sections.
8. Piet de Jong (1976). 14 sections.
9. Recent phylogenetic studies recognized some of the sections [Hasebe et al. 1998 (cp DNA data), Ackerly and Donoghue 1998 (nrDNA ITS), Suh et al. 2000 (ITS), Pfosser et al. 2002 (ITS and trnL-F), Tian et al. 2002 (ITS and trnL-F), Li et al. 2006 (psbM-trnT), Grimm et al. 2007 (ITS), and Renner et al. 2007]. Nevertheless, taxon sampling was not comprehensive and relationships among sections were generally unresolved (see below).
10. Piet de Jong (2004) suggested another classification system of Acer based on morphology as well as recent molecular studies recognizing 156 species and 19 sections (see table below).
11. Xu et al. Flora of China: 130 species worldwide and 110 species in China.
Distribution (Xu 1999)
12. Monophyletic clades recognized by a combined analysis of nuclear (nrDNA ITS and RT-1) and chloroplast (rpl16, trnL-F, psbM-TrnD, ndhF, and psbA-trnH) sequences (Li et al. unpublished).