L. Hufford, DEVELOPMENTAL MORPHOLOGY OF FEMALE FLOWERS OF GYROSTEMON AND TERSONIAAND FLORAL EVOLUTION AMONG GYROSTEMONACEAE, American journal of botany, 83(11), 1996, pp. 1471-1487
Floral simplifications and specializations in the evolution of Gyroste
monaceae have confused the systematics of the family. Recent phylogene
tic analyses have demonstrated their placement among Capparales. This
investigation presents a phylogenetic analysis of Gyrostemonaceae, dem
onstrating that Codonocarpus and Gyrostemon form a clade that is the s
ister group of Cypselocarpus, Tersonia, and Walteranthus. These phylog
enetic results and data on development of Gyrostemon and Tersonia are
used to discuss the morphology and evolutionary diversification of fem
ale flowers of Gyrostemonaceae. The uniseriate perianth of Gyrostemona
ceae consists of four to eight tepals with an unusual lateral to media
n developmental sequence. The female flowers of Gyrostemon and Tersoni
a display no distinctive evidence of an androecium, although the forme
r has late-forming, primordium-like structures positioned between the
tepals and gynoecium that may be the vestiges of either a second peria
nth series or the androecium. The gynoecium of Gyrostemonaceae is sync
arpous, although the two main clades in the family differ in the expre
ssion of ovarian synorganization. The Codonocarpus-Gyrostemon clade is
unusual in having largely separate carpels that are only syncarpous b
ecause the ventral side of each is formed by the flank of the floral a
pex. All Gyrostemonaceae, however, incorporate the flank of the floral
apex as the ventral side of the carpel, and this is the location of o
vule development. On the basis of its placement in a clade that includ
es Tersonia and Walter-anthus, the uniloculate and uniovulate gynoeciu
m of Cypselocarpus may be pseudomonomerous. All Gyrostemonaceae have l
arge stigmas that are typical of anemophilous taxa, and they differ fr
om most other Capparales in this attribute. Among Capparales, Gyrostem
onaceae may be most similar to Ochradenus (Resedaceae), which also app
ears to be anemophilous. It is unclear whether the similarities of Och
radenus and Gyrostemonaceae are homologies, indicative of a close rela
tionship between the two groups, or evolutionary parallelisms associat
ed with separate shifts to anemophily.