Comparative studies of leaf evolution in the California Chaparral
In an article published in the May 2004 issue of The American Naturalist, David D. Ackerly (Stanford University) compares the evolution of twelve lineages of the California Chaparral.
Which came first--trait or environment? This question lies at the heart of the study of adaptation by natural selection. In Mediterranean-type climates, many woody plants have small, tough, evergreen leaves (dubbed sclerophylls) which allow them to photosynthesize during the cool wet winters and survive the hot summer dry season. This paper presents the first comparative test of alternative hypotheses to explain these shared features. Did these traits evolve independently in different lineages, in response to the unique Mediterranean-type climate? Alternatively, did the traits evolve first in response to other factors, subsequently promoting the success of these lineages when summer drought conditions arose in the past few million years? Twelve independent plant lineages of the California chaparral were examined, using comparative methods that combine new phylogenetic information and statistical techniques. Only four of the twelve lineages showed the pattern expected if the leaves had evolved to suit the Mediterranean-type climate. In the other cases, the leaf traits appear to be ancestral characteristics of these lineages that predate the climatic conditions. These results, together with biogeographic and paleobotanical information, highlight the importance of ecological processes in concert with adaptive evolution in shaping the form
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Researchers at TU Graz calculate the most accurate gravity field determination of the Earth using 1.16 billion satellite measurements. This yields valuable knowledge for climate research.
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Researchers at Chalmers University of Technology, Sweden, have discovered a completely new way of capturing, amplifying and linking light to matter at the nanolevel. Using a tiny box, built from stacked atomically thin material, they have succeeded in creating a type of feedback loop in which light and matter become one. The discovery, which was recently published in Nature Nanotechnology, opens up new possibilities in the world of nanophotonics.
Photonics is concerned with various means of using light. Fibre-optic communication is an example of photonics, as is the technology behind photodetectors and...
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