Abstract Detail

Paleobotanical Section

Hu, Shusheng [1], Taylor, David W. [2].

Predictions of early Cretaceous floral structure and pollination biology by fossil pollen proxy.

Understanding of the structure of early flowers and pollination biology had been indirect because a 10 my gap between the earliest accepted angiosperm pollen and flowers. Yet fossil pollen size has been shown to be correlated with certain floral characteristics and pollinators. We use the size of the earliest unequivocal Early Cretaceous angiosperm pollen to predict potential pollinators and carpel structure. From the Valanginian (mean 19.5 µm) to the Aptian (29.0 µm) the average maximum dimension size increases by 49% and is significantly smaller during the earlier stages than the Aptian or the average of the lower size range in living monosulcate families. In addition, the size distributions changes with the size range 20-24 µm having the highest percentage during the Valanginian, the less than 20 µm size range the highest during the Hauterivian and Barremian, and 25 to 40 µm highest during the Aptian. The average size of pollen from the Aptian is not significantly different than the lower size range in living monosulcate families and the higher percentage of larger grains is also similar. In addition, significant size variation is not found between temperate (England) and tropical (Africa) localities during the Hauterivian and Aptian, yet significantly smaller grains are found at the temperate localities during the Barremian, when a warm pulse occurred. These data support the hypothesis that early angiosperm had initially insect and ambophilous pollinated flowers, and that length of the pollen tubes were short indicating of short styles and apocarpy. The driving forces for changes in angiosperm pollen size appear to be due to increases in advanced pollination include nectar feeders and wind, and the evolution of longer styles and syncarpy. Placement of the earliest reported grains suggest the origin of Cretaceous angiosperms appears to be around the Tethys basin with later radiation probably related to pollination specialization in tropical areas of Africa and South America.

Broader Impacts:

1 - Yale University, Peabody Museum of Natural History, 170 Whitney Ave., New Haven, CT, 06511
2 - Indiana University Southeast, Department of Biology, 4201 Grant Line Road, New Albany, IN, 47150

Keywords:
pollen
angiosperm
Cretaceous
evolution
ancestral.

Presentation Type: Oral Paper:Papers for Sections
Session: 23
Location: 555A/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 9:00 AM
Number: 23005
Abstract ID:311