Developmental and Structural Section
Shannon, Robynn K. .
Developmental Patterns of Gender Expression in Urtica dioica L. (Urticaceae).
In this study I examined the developmental sequence of gender expression in two natural populations of the monoecious Urtica dioica subsp. gracilis, as well as in greenhouse cultures of rare monoecious individuals of the dioecious U. dioica subsp. dioica and monoecious progeny of artificial hybrids between these two subspecies, documenting patterns in the developmental sequence of male and female flower production. Excluding shoots that were unisexual or had mixed gender expression at every node (subsp. dioica and hybrid plants only), 71 different patterns were observed. I examined the extent of variability in developmental patterns of gender expression within taxon, as well as in traits such as initial gender, final gender, gender bias, number of gender “switches,” and relative proportions of mixed-gender and single-gender nodes. While there are clear trends in developmental pattern, initial gender, final gender, and other gender characters, not a single character examined is uniform for all shoots, even within subspecies. On the other hand, developmental patterns of gender expression in U. dioica are clearly not completely plastic. The observed trends do point to the influence of genotype, particularly when comparing each subspecies to the intersubspecific hybrids, as well as to each other. Shoots of subsp. gracilis were most likely by far to begin flower production with male flowers and end with female flowers, whereas shoots of subsp. dioica were more likely to both begin and end with mixed-gender flowering nodes. Hybrids between the two subspecies were intermediate in their developmental patterns of gender expression. On average, shoots of subsp. gracilis switched gender expression more often than shoots of subsp. dioica, but shoots of subsp. dioica produced a greater proportion of mixed-gender flowering nodes than those of subsp. gracilis. These apparently represent different strategies for producing both male and female flowers throughout much of the flowering season.
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1 - University of Connecticut, Department of Ecology & Evolutionary Biology, u-3043, 75 North Eagleville Road, Storrs, ct, 06269-3043, usa
Presentation Type: Poster:Posters for Sections
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM