Families of Vascular Plants - EEB337H

Rosales - Rosaceae

Tribe Pyreae - How many genera?


The Pyreae have been the subject of considerable debate regarding the number of genera that should be recognized. Intergeneric hybridization is frequent (Robertson et al. 1991), to the extent that one worker (Kovanda 1965) has suggested that the subfamily could be thought of as a single genus. Mabberley (1997) has pointed out that much of the splitting of economically important temperate genera (e.g. apples, pears) can be seen as a holdover from pre-Linnaean folk taxonomies. However, as there is considerable morphological variation within the subfamily it seems unnecessary to act on Kovanda's extreme, straw-man point of view.

Variation in fruit and leaves within the Pyrodae 1
Fruit... \Leaves... Simple Compound
Follicle Kageneckia Gillenia (sister group of tribe Pyreae)
Capsule Lindleya, Vauquelinia  
Berry2 Amelanchier, Aria3, Chaenomeles, Chamaemeles, Chamaemespilus3, Cydonia, Docynia, Eriobotrya, Heteromeles, Malacomeles, Malus, Peraphyllum, Photinia, Pseudocydonia, Pyrus, Rhaphiolepis, Torminalis3 Cormus3, Sorbus3
Drupe2 Cotoneaster, Crataegus, Dichotomanthes, Hesperomeles, Mespilus, Pyracantha Osteomeles

Molecular evidence clearly supports the Maloideae as a monophyletic group1. However, the chloroplast genome has hardly differentiated at all within the subfamily (Evans 1999). Recent evidence of intergeneric relationships has come from nuclear genes as well as from some non-molecular synapomorphies (Campbell et al. 2007).

(Left) Flower and fruits of Kageneckia sp., University of California Botanical Garden. (Above) Immature inflorescence of Vauquelinia californica, Boyce Thompson Southwestern Arboretum. Photos: © R. C. Evans 1997

Malus domestica fruits. Photo: M. Ferguson, © 1998 Royal Ontario Museum.

Campbell et al. (2007) tree


1. Maloideae sensu lato comprise the traditional Maloideae with fleshy fruits derived from hypanthial ovaries, plus genera with capsular or follicular fruits (Kageneckia, Lindleya, Porteranthus, Vauquelinia) that previously were considered to belong to subfamily Spiraeoideae. Recent studies have shown these genera to be closely related to the traditional Maloideae on the basis of reproductive morphology (Evans 1999), chloroplast gene DNA sequences (Evans 1999), and patterns of nuclear gene duplication and sequence variation (Evans et al. 2000). These results have considerable significance for hypotheses about the origin of the Maloideae.

2. Maloideae fruits are traditionally thought of as being pomes, but this amounts to little more than saying that they have apple-like fruits. For purposes of contrasting fruit construction in the Maloideae here, a berry is a fleshy, indehiscent fruit as is a drupe; the latter differs in that the inner part of the fruit wall becomes woody, forming one or more pyrenes, within each of which a single seed is found.

3. These genera are segregates of Sorbus sensu lato.


References

Evans, R. C. 1999. Molecular, morphological, and ontogenetic evaluation of relationships and evolution in the Rosaceae. Ph.D. thesis, Botany Department, University of Toronto.

Evans, R. C., Alice, L. A., Campbell, C. S., Kellogg, E. A., & Dickinson, T. A. 2000. The granule-bound starch synthase (GBSSI) gene in the Rosaceae: multiple loci and phylogenetic utility. Molecular Phylogenetics & Evolution 17: 388-400. (abstract)

Kovanda, M. 1965. On the generic concepts in the Maloideae. Preslia 37: 27-34.

Robertson, K. R. 1974. The genera of Rosaceae in the southeastern United States. Journal of the Arnold Arboretum 55.

Robertson, K. R., Phipps, J. B., Rohrer, J. R. & Smith, P. G. 1991. A synopsis of genera in Maloideae (Rosaceae). Systematic Botany, 16: 376-394.


Rosaceae

The Families of Flowering Plants
DELTA database in natural language

L. Watson and M. J. Dallwitz


Rosaceae

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