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Abstract Detail


Dickinson, Tim [1], Talent, Nadia [1], Lance, Ron [2].

Crataegus subgenus Americanae: tools with which to sort out eastern North American hawthorns.

Sorting eastern North American hawthorns into biologically plausible taxa informed by information on the phylogeny of the genus is a goal now well within reach. A magisterial treatment of the genus in North America has been published in Flora North America that tackles the problem of synonymizing superfluous names. A profusely illustrated field guide for the Southeastern United States provides descriptions and keys also, likewise informed by the author’s extensive field experience. Both these publications have benefited from data that have come from flow cytometric estimates of ploidy level, in both leaves and seeds, and from studies of DNA sequence variation. These latter studies have largely supported the morphologically based infrageneric classification of Crataegus into subgenera, sections, and series. Where molecular data disagreed with prior interpretations of morphology, they have led to insights into the roles of hybridization and gametophytic apomixis in hawthorn evolution. These insights have been achieved, however, mainly in western North America where the hawthorn flora is less complicated. Nevertheless, we suggest that elsewhere on the continent the time is ripe to use these tools to test the taxonomic hypotheses that have been advanced. Testing them can be concomitant with exploring a number of additional research problems. To what extent is morphological variation indicative of adaptation? Elsewhere, variation in relative allocation of resources to dispersal as opposed to establishment appears to be important, possibly more so than features representing possible adaptations to climatic extremes. What are the population genetic consequences of frequent apomixis, and how do they correlate with morphological evidence for distinct microspecies? Comparison of microsatellite variation in seed families between a sexual diploid and a tetraploid apomict has substantiated expectations based on embryology and pollination experiments. Finally, what do hawthorns and other Maleae (e.g. Amelanchier, Cotoneaster, Hesperomeles, Malus, Photinia, and Sorbus in the wide sense), to say nothing of genera like Acaena, Alchemilla, Polylepis, Potentilla, Prunus, Rosa, Rubus, and Spiraea, contribute to the discussion of the relationship between gametophytic apomixis, polyploidy, and diversification?

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Related Links:
North American black-fruited hawthorns
Haws - A Guide to the Hawthorns of the Southeastern U.S.

1 - Royal Ontario Museum, Natural History, 100 Queen's Park, Toronto, ON, M5S 2C6, Canada
2 - North American Land Trust , Land Manager, Big Ridge, 100 Hickory Hill Road, Chadds Ford, PA, 19317, USA

gametophytic apomixis

Presentation Type: Poster
Session: P, Systematics Section/ASPT Posters
Location: Exhibit Hall/Savannah International Trade and Convention Center
Date: Monday, August 1st, 2016
Time: 5:30 PM This poster will be presented at 5:30 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PSY029
Abstract ID:578
Candidate for Awards:None

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