Table 2. Intermediacy of allotetraploid Crataegus douglasii Lindl. and C. rivularis Nutt. with respect to their diploid progenitors in C. subg. Sanguineae Ufimov and sympatric tetraploid members of C. subg. Americanae El-Gazzar.

Ploidy level data as in Talent & Dickinson (2005) and Zarrei et al., (2015). Morphological and ecological data summarized from T. A. Dickinson, unpubl. mss; descriptors as in Dickinson et al. (2008). Geographic distribution (Canada, United States) as per Phipps (2015).

Allotetraploid Crataegus douglasii
	C. subg.Sanguineae C. suksdorfii (2x)	allotetraploid	C.subg.Americanae(4x) (C. chrysocarpa s.l., C. macracantha s.l.)
Thorn length	Short	Intermediate	Long
Leaf toothing	5—7/1.0 cm	8—10/1.0 cm	7—12/1.0 cm
Calyx lobe length	Short	Intermediate	Long
Calyx lobe margination	Teeth absent	Intermediate	Teeth abundant
Stamens per flower	Ca. 20	Ca. 10	Ca. 10
Styles per flower	(3-) 4—5 (-6)	3—4 (-5)	2—3 (-5)
Ecological amplitude	Narrow	Broad	Broad
Geographic range	Northern CA, western OR, southwestern WA	AB, BC, CA, ID, MT, ON, OR, WA	Nearly transcontinental
Allotetraploid Crataegus rivularis
	C.subg.Sanguineae C. saligna (2x)	allotetraploid	C.subg.Americanae(4x) (C. chrysocarpa s.l., C. macracantha s.l.)
Thorn length	Short	Short	Long
Calyx lobe pubescence	Absent	Sparse	Abundant
Calyx lobe margination	Teeth few or absent	Intermediate	Teeth abundant
Stamens per flower	Ca. 20	Ca. 10	Ca. 10
Styles per flower	4—5	3—4 (-5)	2—4 (-5)
Ecological amplitude	Narrow	Broad	Broad
Geographic range	Western CO, northeastern UT	AZ, CO, ID, NM, NV, UT, WY	Nearly transcontinental