Neotropical Entomology 35(5): 579-587 (2006)

Several alternative interpretations of the pollen records of lake sediments in the Amazonia may arise due to a lack of understanding of the modern environments, mainly related to pollen–vegetation relationship. Therefore, in this work, we studied the modern pollen rain in sediments of the Amendoim Lake, plateaus of the Serra Sul dos Carajás, southeastern Amazonia. This study indicates the predominance of pollen grains from forest formation (ombrophilous forests and capão florestal) over montane savanna in the lake sediments, despite the fact that montane savanna occupies ~90% of the drainage basin. Additionally, these sediments reflect stronger signal of pollen from ombrophilous forests that occur in the slopes of the plateau. Important components of montane savanna such as Vellozia and Cereus were not observed in the modern pollen rain, which may be related to their shorter flowering periods restricted to the beginning of wetter conditions. The absence of Sacoglottis, Trichilia, Clusia, Emmotum, Guapira and Simarouba in the pollen rain is likely associated with different pollination strategy. The occurrence of windblown pollen of Alchornea, Pseudolmedia, Ilex and Cecropia, which are found from low to highlands of the Carajás region, reinforces a regional vegetation signal in sediments. Several plants from the studied site have been improperly described, according to taxonomy and ecology. For example, the current occurrence of Ilex and Styrax in the study site clearly suggests that they cannot be used as indicators of colder palaeoclimate conditions, as previously described. In addition, Poaceae can be found in drier to wetter substrate conditions, and abundance of their pollen grains in lakes can significantly vary according to relief morphology and cannot indicate palaeovegetation openness. Therefore, this work is a good background for further palaeobotany studies for this region.

No abstract

No abstract

The leaf oils of Xylopia aromatica, X. cayennensis, X. emarginata and X. nitida were obtained by hydrodistillation and analysed by GC-MS. The main compounds found in the oil of X. aromatica were bicyclogermacrene (36.5%), spathulenol (20.5%) and limonene (4.6%). The oil from X. cayennensis was dominated by α α α α α-pinene (29.2%), β β β β β-pinene (16.5%), caryophyllene oxide (14.5%), bicyclogermacrene (14.5%), germacrene D (4.7%) and 1,8-cineole (4.5%). The major constituent identified in the oil of X. emarginata was spathulenol (73.0%). The main components found in the oil of X. nitida were γ γ γ γ γ -terpinene (44.1%), p-cymene (13.7%), α α α α α-terpinene (12.6%) and limonene (11.3%). Early papers indicated that spathulenol and caryophyllene oxide are also important volatile compounds found in the leaf oils of Xylopia, Duguetia and Guatteria species. At first sight they could be considered as chemotaxonomic markers to these Annonaceae genera.