Conservation biology of shadbush, Amelanchier (Rosaceae): evidence from systematics, population structure and reproductive ecology

Dibble, Alison

FIELD WORK: Chapter one: 'Morphological variation in shadbush Amelanchier (Rosaceae) at a taxonomically complex population in Maine'. Chapter two: 'Distribution and conservation of two northeastern North American species of Amelanchier (Rosaceae)'. Chapter three: 'Species definitions in agamospermous taxa: the case of Amelanchier nantucketensis'. Chapter four: 'Pollination ecology of Amelanchier nantucketensis (Rosaceae): solitary bees and andropetaly'. The study sites for Chapter 1 & 4 includes an area adjacent to Duck Brook. 'Conservation in asexual plants such as Amelanchier is complicated by hybridization, polyploidy, and agamospermy, which obscure species limits. Nantucket shadbush, A. nantucketensis, is a candidate for federally endangered, while the status of Amelanchier lucida, an endemic of Nova Scotia, is poorly known. I studied morphological variation in Amelanchier using multivariate techniques in (1) a large, mixed population in Bar Harbor, Maine, and (2) A. nantucketensis and seven relatives of northeastern North America. I examined ploidy, megasporogenesis, and pollination ecology including diversity of bees. I report a field survey of A. nantucketensis and its relatives from Nova Scotia to Maryland, and a phylogenetic analysis involving 28 morphological characters and nine species.' 'Multivariate analyses revealed distinct clusters of morphs at Bar Harbor, but each cluster includes 2-6 groups. Amelanchier nantucketensis resembles A. stolonifera f. micropetala in 13 characters. The phylogenetic hypothesis was well-resolved but poorly supported except for a clade of A. stolonifera f. micropetala and A. nantucketensis; these two separated only by ovary summit pubescence, which varies. Amelanchier obovalis may be a sister group. Amelanchier stolonifera f. micropetala is lumped into A. nantucketensis and the species has more than 65 known populations with distinct suite of bees; it is faculatively agamospermic pseudogamous, tetraploid, and sets fruit when pollen from other morphs is applied.' 'Andropetaly, with fertile pollen on petals, is found in Amelanchier nantucketensis, and is associated with low plant stature, high floral density, and a large number of stems; unidentified chemical or visual attractants may also be important. I compared A. nantucketensis and A. humilis to see if bees prefer andropetalous over normal flowers where floral display was similar. Bee abundance and diversity were higher on andropetalous plants, perhaps because high floral density affords efficient foraging.' 'Conservation is recommended for Amelanchier nantucketensis at local and state, but not federal, levels because of numerous populations and colonizing habit. Management strategies should include the solitary bees that associate with A. nantucketensis. Conservation for A. lucida appears unwarranted because it closely resembles A. stolonifera.' 'These four thesis chapters were prepared as manuscripts for submission to journals. Chapter one will be submitted to American Journal of Botany with co-authors Christopher S. Campbell, Wesley A. Wright, and Craig W. Greene. Chapter two was submitted to Rhodora in February 1995 with coauthor Campbell. Chapter three will be submitted to Systematic Botany with Campbell and Wright. Chapter four will be submitted to Ecology with Francis A. Drummond and Wallace E. LaBerge (Illinois Natural History Survey, Champaign, Illinois).' Appendix 1 contains box plots of raw means for seven Amelanchier groups studied at Bar Harbor, Maine. /STUDY LOCATIONS:/ /MOUNT DESERT ISLAND/Duck Brook