Tropical Biology Section
Chen, Xi , Cannon, chuck , Raquet, Virginie .
Evolution of fruit and seed morphology in the Asian stone oaks (Lithocarpus: Fagaceae).
Seed size and chemistry to predation are major determinants of plant life history and reproductive strategy. In the paleotropical stone oaks (Lithocarpus: Fagaceae), two major fruit types can be identified, based upon the relationship of the nut and cupule. “Acorns” are formed by a small cupule in a large, free, and exerted bare nut sits. “Enclosed receptacle” (ER fruit) are formed by fusion of the nut to the cupule, within which the seed is entirely enclosed. In these two fruit types, two tissue types, exocarp and receptacle, have exchanged their protective functions. The ER fruit type is confined to three relatively small and clearly delineated sections, each representing an independent derivation of the fruit type. These sections are found in relatively small geographic range with several species endemic to small areas of Borneo or Indochina. To understand the evolutionary patterns leading to this dramatic morphological innovation, we examined fruit and seed morphology in relation to an ITS phylogeny. Fruit and seed morphology were described using multivariate morphometric analyses of outline shape of the two major tissues. Our results indicate that ER fruits are larger, have thick woody protective covering, and contain larger seeds. Additionally, the evolutionary transition between these ER species and their acorn-bearing ancestors was dramatic, involving large morphological changes in both fruit and seed. The independent occurrence of the ER fruit type in well-separated lineages, both phylogenetically and geographically, indicates strong convergent patterns of evolution towards the ER morphology. This suggests that the fruit type confers some selective advantage, perhaps by preventing seed predation and allowing these species to fruit independently of community wide mast events. We are currently conducting chemical analyses of seeds to determine the amount of chemical protection. If ER fruit provide primarily mechanical protection, a trade-off between chemical and morphological protection may be evident.
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1 - Texas Tech University, Biological science, 223 Indiana Ave B209, Lubbock, TX, 79415, USA
2 - Texas Tech University, Biological science, Department of Biological Sciences, Box 43131, Texas Tech University, Lubbock, TX, 79410-3131, USA
3 - Botanical Research Institute of Texas, 509 Pecan Street, Suite 101, Fort Worth, Texas, 76102, USA
ER fruit (enclosed receptacle).
Presentation Type: Poster:Posters for Sections
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM