The terpenes, sterols, alkaloid (glaucine) and alpha-tocopherol show seasonal variation for Croton hemiargyreus hemiargyreus and Croton echinocarpus. The amounts of triterpenes are higher during the tropical summer and in most samples the major sesquiterpene was characterized as caryophyllene. The seasonal variation of glaucine showed a maximum between June and October for C. hemiargyreus, and ...

Over the past decade, researchers have used variation in the chemical composition of fish otoliths (earstones) to address a number of ecological questions, such as stock assessment and assessing rates of movement of individuals among habitats or life-history stages. However, these methods have yet to be applied successfully to the study of larval connectivity, a major unanswered question in mar...

Poison frogs contain an alkaloid-based chemical defense that is sequestered directly from a diet of alkaloid-containing arthropods. Geographic and temporal variation in alkaloid defense is common in poison frogs and is generally attributed to differences in the availability of alkaloid-containing arthropods. Variable chemical defense in poison frogs may have important consequences for predator-...

[1] The mean cloud albedo over a spatial or temporal domain depends not only on the mean cloud condensation nucleus (CCN) spectrum but also on the CCN spectrum variation. When the variation of CCN spectrum is neglected, cloud albedo calculated using the mean CCN spectrum is positively biased. The CCN spectrum variation due to either variation in size distribution or chemical composition, as wel...

Geographical variation in chemical tolerance within a species can significantly influence results of whole animal bioassays, yet a literature survey showed that the majority of articles using bioassays did not provide detail on the original field collection site of their test specimens confounding the ability for accurate replication and comparison of results. Biological variation as a result o...

Anther volatiles of 12 Ranunculaceae species distributed in six genera (Anemone, Aquilegia, Caltha, Pulsatilla, Ranunculus, and Trollius) were investigated by thermal desorption of anthers in quartz microvials inserted into a modified injector. Chemical analysis (GC-MS) yielded a total of 116 compounds from which 103 compounds could be identified. A great diversity of compounds was observed, in...

Specialist herbivores and pathogens could induce negative conspecific density dependence among their hosts and thereby contribute to the diversity of plant communities. A small number of hyperdiverse genera comprise a large portion of tree diversity in tropical forests. These closely related congeners are likely to share natural enemies. Diverse defenses could still allow congeners to partition...

Natural hybridization is a frequent phenomenon in plants. It can lead to the formation of new species, facilitate introgression of plant traits, and affect the interactions between plants and their biotic and abiotic environments. An important consequence of hybridization is the generation of qualitative and quantitative variation in secondary chemistry. Using the literature and my own results,...