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DIOECISM AND ITS CORRELATES IN THE CAPE FLORA OF SOUTH AFRICA
Author(s) -
Steiner Kim E.
Publication year - 1988
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1988.tb11250.x
Subject(s) - cape , flora (microbiology) , biology , dioecy , anemophily , pollination , temperate climate , ecology , endemism , botany , pollinator , pollen , archaeology , geography , genetics , bacteria
Floral sexuality is characterized for the flora of the Cape region of South Africa. Among angiosperms ( N = 8,497), monostylous hermaphroditism constitutes the largest proportion of species with 77.7%, followed by gynomonoecism (7.1%), dioecism (6.6%), andromonoecism (4.0%), monoecism (2.6%), heterostylous hermaphroditism (1.9%), polygamomonoecism (0.01%) and polygamodioecism (0.01%). The incidence of dioecism is significantly higher ( P < 0.001) at the species level for two smaller floras within the Cape flora that consist mostly of species‐rich fynbos vegetation (Cape of Good Hope Nature Reserve: 11.6% [ N = 1,349], Cape Hangklip: 9.7% [ N = 1,046]). The relatively high incidence of dioecism in all three floras compared to other temperate floras is due to the large number of Restionaceae species. Excluding these rush‐like plants, dioecism at the species level is only 3.0% for the Cape flora, 4.2% for the Cape Hangklip flora and 3.6% for the Cape of Good Hope flora. At the generic level there are no significant differences in the incidence of dioecism between the three floras. Among dioecious species and genera in the Cape flora, there is a higher than expected incidence of wind pollination, fleshy fruits and nonwoodiness when each variable is analyzed independently. The association between nonwoodiness and dioecy has not been reported for other floras and is due to the large proportion of nonwoody wind‐pollinated Restionaceae. If this family is excluded from the analysis, dioecy becomes associated with biotic pollination, fleshy fruits, and woodiness. Interactions among the variables themselves as well as with dioecism indicate the need for a joint analysis of the variables. At the genus level, analyses reveal the following: 1) There is a higher than expected incidence of wind pollination among dioecious plants with dry fruits. If the Restionaceae are excluded from the analysis, wind pollination is more common than expected only for woody plants with dry fruits. 2) Dioecious plants that are biotically pollinated have a significantly higher incidence of fleshy fruits than expected. 3) Dioecious plants with dry fruits that are biotically pollinated have a higher than expected incidence of woodiness. If the Restionaceae are excluded from the analysis, woodiness is more common than expected among both nonwind and wind‐pollinated dioecious genera.