Search

The flowers of the mangrove palm Nypa fruticans attracts a diverse array of potential pollinators. However, little is known about the pollination mechanism and which functional groups are the key pollinators. Inflorescences of nine nipa palms of different flowering stages were observed three times a day between sunrise and sunset in Thailand. The apparent entomofauna activity was recorded and all inflorescences were collected for extraction and identification of the beetle fauna. Beetles extracted from female inflorescences were measured for pollen load. In addition, thermogenesis was recorded over two days on two separate inflorescences. The most frequent visitors were species of nitidulid (genus Epuraea and the subfamily Cillaeinae) and curculionid beetles. Although they only carried small amounts of pollen grains, these groups of beetles were omnipresent. Thermogenesis peaked around 6.30 am with temperature elevations reaching 6 degrees above ambient. The result obtained in this study are compared with those of previous studies conducted elsewhere in Thailand and in the Philippinies. The combined evidence strongly suggests a pivotal role in pollination of beetle visitors to the inflorescences of Nypa fruticans.

A Danish beech (Fagus sylvatica) forest was studied during a period of five years, to reveal temporal and spatial patterns in the ground vegetation within a year and between years. In 1994, twenty stations were established in commercially managed forests south of Aarhus, and the frequency of the vascular plants was recorded in 40 stratified random Raunkiier circles (0.1m2). The sampling was repeated in 1995, 1997 and 1998. The seasonal variation in species frequencies was furthermore studied in nine of the permanent stations. The findings were summarised in terms of species richness and averaged Ellenberg ecological values, and analysed with clustering analysis and ordination. We applied Steinhaus similarity index and detrended correspondence analysis to detect fluctuation and succession. To test for significant vegetation changes, a non-parametric Mantel test was used. The species richness and Ellenberg's indicator values were unchanged during the five years. The classification results, however, differed between the years. In particular, changes in the quantitative similarity between years were high (12–23%), and this was supported by ordination. We conclude that the vegetation in the study area, at least in the studied 5-years period, did not how signs of clear successional trends, but merely changes in species abundance, which we associate with short-term fluctuation. Further studies, on different time scales, of vegetation dynamics in forests should be initiated, in order to make better descriptions of plant communities, and to detect possible successional trends. We suggest that such studies also include long term monitoring of environmental parameters in a nested, permanent sampling design.

The leaf anatomy of the genera Phytelephas, Palandra and Ammandra (Arecaceae) is described and compared. The anatomical features considered to be of taxonomic importance include: the distribution of fibre bundles and minor veins in mesophyll and hypodermis, the relative size of the cells of the stomatal complex and whether the costal bands of eleongated cells are conspicuous in surface view or not. Species of Palandra and Phytelephas form an anatomically homogenous group. The two species of Ammandra differ in their anatomy, although they have several xeromorphic adaptations in common. This is peculiar as they both grow in humid habitats.