中国热带、亚热带栎属植物花粉形态多样性及其古气候意义

MORPHOLOGICAL DIVERSITY OF QUERCUS POLLEN AND ITS PALAEOCLIMATIC IMPLICATION IN TROPICAL AND SUBTROPICAL CHINA

本研究利用扫描电子显微镜对栎属(Quercus L.)植物中18个种[10种属于栎亚属(Quercus),8种来源于青冈亚属(Cyclobalanopsis)]的花粉进行了详细的外壁纹饰研究。这些栎属植物广泛分布于中国热带和亚热带地区。结果显示,落叶类型栎亚属花粉外壁具有瘤状或分散的瘤状纹饰,常绿类型栎亚属花粉具有棒状或聚合棒状纹饰,青冈亚属花粉具有皱波状、刺状或聚合棒状纹饰。花粉外壁纹饰特征可为栎属花粉化石的属内种级分类提供有效的鉴定依据。大量的现代栎属花粉研究显示,具有棒状纹饰的花粉多源自于分布在高海拔地区的常绿类型栎亚属植物,而具有皱波状和刺状纹饰的花粉多来源于相对低海拔地区分布的青冈亚属植物。在古环境重建中,栎属化石花粉的形态多样性不仅可以帮助我们可靠地区分关键地层中的常绿和落叶栎属植物,也可能成为指示不同海拔高度的潜在的古气候指标。

Modern pollen from 18 Quercus species(10 species belonging to subg. Quercus and 8 species from subg. Cyclobalanopsis) was morphologically examined by using scanning electron microscope to distinguish their sculpture types. These Quercus species are the typical arboreal components in the tropical and subtropical forests of China. Under high magnification, the pollen images showed that the deciduous subg. Quercus pollen has verrucate and scattered verrucate sculptues;evergreen subg. Quercus pollen has rodlike and agglomerated rodlike sculptures;subg. Cyclobalanopsis pollen has rodlike vertical, rodlike masked and agglomerated rodlike sculptures. The result shows that the ornamentation of the pollen exine is a valuable tool for infrageneric identification of fossil Quercus pollen. Nume-rous morphological investigations of Quercus pollen showed that pollen with rodlike sculpture character is mostly derived from evergreen subg. Quercus at high elevations. In contrast, pollen with rodlike vertical and rodlike masked sculpture characters is derived from subg. Cyclobalanopsis distributed at low elevations. For the palaeoclimatic reconstruction, morphological diversity of Quercus pollen not only helps us to distinguish evergreen and deciduous Quercus pollen, but also provides a potential proxy indicating elevation ranges of oak distribution.