Page 199 - PC2019 Program & Proceedings

PLANT CANADA 2019

S183. In praise of larger genera: looking at the Amelanchier-Hesperomeles-Crataegus clade
(Rosaceae tribe Maleae)
1
2
Dickinson, T. ; R. Ufimov ; D. Metsger
1
1 Royal Ontario Museum
2 Komarov Botanical Institute RAS
The value of larger, more inclusive genera is apparent to us. While it can be argued that taxonomic ranks
are arbitrary and need only map to monophyletic groups, large genera focus attention on relatively recent
evolutionary radiations that appear to have followed on from major divergences. Based on DNA sequence
data from several loci, the Rosaceae comprise three supertribes of which one, the Pyrodae, includes both
some plants with dry dehiscent fruits and the berry- and drupe-bearing fruit trees in tribe Maleae. This
tribe includes three major clades, of which the more basal one is made up of Amelanchier and its
segregate genera, Hesperomeles, and Crataegus. Relative to Amelanchier, Hesperomeles and Crataegus
share the synapomorphies of (1) a pattern of leaf secondary venation resembling but somewhat different
from camptodromous; (2) producing determinate lateral shoots, the tips of which may become sclerified
so that they form a thorn, variously leafy or leafless; and (3) producing polypyrenous drupes rather than
berries. Likewise, both genera exhibit a trend toward producing fewer-seeded fruits. The possibility of
treating Hesperomeles as a sixth subgenus in Crataegus (much as has been done with Mespilus) appeals
to us because of the way doing so enforces a comprehensive interpretation of evolution in the
Hesperomeles-Crataegus lineage (leaf venation, thorns, fruit type). A MorphoBank project supporting
this research is accumulating images representing phenotypes of these genera.

Tim Dickinson (tim.dickinson@utoronto.ca)

S184. Molecular and morphological data reveal hidden diversity in common North American
Frustulia species (Amphipleuraceae)
1
Bouchard, A. ; P. Hamilton ; J. Starr 1
2
1 University of Ottawa
2 Canadian Museum of Nature
Frustulia is an established diatom genus that is common and widespread across North America. Like
many diatom genera, Frustulia has been the subject of taxonomic confusion. Although recent studies have
examined taxa from Europe and New Zealand, there exists no detailed genetic data for North American
individuals. Using both molecular (rbcL and 18S rRNA sequences) and morphological (frustule
characters and shape analysis) data, we investigated common taxa from the genus in North America. We
recognized eight taxa in this study, including two unknowns. A new species, F. gibsonea sp. nov., is
described. This species was found in previous studies and described as F. cf. krammeri based on
morphology. The use of molecular characters demonstrates that the group is a distinct species. Despite
differences in molecular sequences, F. gibsonea and F. krammeri are similar morphologically, showing
overlap using traditional measurements and shape analysis. This suggests that the combination of
molecular and morphological data can help in deciphering cryptic taxa. We were unable to separate F.
saxonica, F. crassinervia, and F. krammeri based on molecular data alone, although they could be
separated using morphology. The low sequence divergence values obtained between the three taxa
indicate that they are very closely related. Future research, focusing on less conserved genes, will be
necessary to resolve these taxonomic complexes. Alternatively, this morphological variation may be the
result of phenotypic variation.

Andreanne Bouchard (abouc103@uottawa.ca)

Page 197 of 339