Abstract Detail

Systematics

Dickinson, Tim [1], Haripersaud, Padmattie [1], Yan, Xue Qi [2], Talent, Nadia [1], Zarrei, Mehdi [3].

Polyploidy, niches, diversification: where does gametophytic apomixis fit in?

Crataegus series Cerrones (C. section Douglasia) is a small agamic complex of black-fruited hawthorns found in the central Rocky Mountain and adjacent Great Basin states. The Cerrones comprise diploid C. saligna, and its two allotetraploid derivatives, C. erythropoda and C. rivularis, all three forming a clade in a well-supported cpDNA phylogeny. The pollen parent of these allotetraploids is likely one or both of the widely distributed, red-fruited tetraploids, C. chrysocarpa (C. section Coccineae) and C. macracantha (C. section Macracanthae). Unlike C. saligna, all four tetraploids are expected to be self-compatible, and all four are pseudogamous, facultative apomicts. The geographic ranges of the Cerrones tetraploids are intermediate in size between that of diploid C. saligna and those of the two red-fruited tetraploids. All three Cerrones occupy approximately the same climatic niche, and this niche overlaps with only portions of those of C. chrysocarpa and C. macracantha. Quantification of the major and minor venation of the leaves of all five species indicates that the venation of the Cerrones tetraploids is intermediate in density between that of diploid C. saligna (most dense) and that of the two red-fruited tetraploids (least dense). What explains the pattern of geographic parthenogenesis seen in the contrast between the range of diploid C. saligna and the ranges of the tetraploids? We suggest that, in common with other members of C. section Douglasia studied in the Pacific Northwest, the principal effect of polyploidy is to enhance dispersal. Once self-fertile allotetraploids have been formed (presumably via an evanescent triploid bridge), any isolated individual is able to produce abundant crops of clonal seed, while still retaining the capacity to participate in biparental reproduction as either a seed or (more likely) a pollen parent. Adaptation to a xeric niche was undoubtedly important in the evolution of C. saligna, but it would appear that the greater dispersability of its allotetraploid descendants has outweighed any effects of their less specialized leaf vascular architecture. We suggest that the relationships seen in this small agamic complex between the gametophytic self-incompatibility of the Rosaceae tribe Maleae and the polyploidy, hybridity, and gametophytic apomixis that are frequent in Crataegus (and some of the other genera of the Maleae) are likely to be found elsewhere in the genus, especially where taxonomic complexity is considered to be greatest.

Related Links:
North American black-fruited hawthorns

1 - Royal Ontario Museum, Natural History, 100 Queen's Park, Toronto, ON, M5S 2C6, Canada
2 - University of Toronto, Ecology & Evolutionary Biology, 25 Willcocks St., Toronto, ON, M5S 3B2, Canada
3 - The Hospital for Sick Children, The Centre for Applied Genomics (TCAG), Peter Gilgan Centre for Research and Learning, 686 Bay St., Toronto, ON, M5G 0A4, Canada

Keywords:
geographic parthenogenesis
hybridization
Crataegus
Maleae
Rosaceae.

Presentation Type: Oral Paper
Session: 41, Basal Rosids & Rosids I
Location: 101/Savannah International Trade and Convention Center
Date: Wednesday, August 3rd, 2016
Time: 11:15 AM
Number: 41013
Abstract ID:583
Candidate for Awards:None