(NAS Colloquium) The Future of Evolution (2002) / Chapter Skim
Currently Skimming:
Human-caused Environmental Change: Impacts on Plant Diversity and Evolution
Human-caused Environmental Change: Impacts on Plant Diversity and Evolution
Pages 45-52
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 45... ...
Environmental Constraints in Plant Communities What are the major environmental variables that limit the abundance of terrestrial and aquatic plants, and which of these variables are being impacted significantly by human actions? In essence, plants may be limited by nutrients and other resources, by pathogens and herbivores, by disturbances, by dispersal abilities, and by the physical environment, including its climate.
|
From page 46... ...
followed the dynamics of North American forests after glacial recession, and observed time lags of thousands of years between a region having the appropriate climate for a tree species and the arrival of that species. Such time lags could greatly influence responses of plant communities to human-caused environmental changes (58~.
|
From page 47... ...
In total, human actions are modifying many environmental constraints that, in combination with intraspecific and interspecific trade-off, led to the evolution of extant plant species and thus influenced the composition, diversity, and functioning of terrestrial and aquatic plant communities. If current trends continue, within 50 to 100 years the suites of factors constraining the structure of many plant communities may fall outside the envelope of values that existed both before the industrial revolution and when many of the plant species evolved.
|
From page 48... ...
For instance, fertilization of the Park Grass plots with 4.8 g.m-2 of N as ammonium sulfate, led to dominance by the grassAgrost~s (84% of community biomass compared with an average abundance in unfertilized control plots of 12%)
|
From page 49... ...
Comparable patterns of dominance by a few formerly rare species, of competitive displacement of most existing species by these newly dominant species, and of high susceptibility to invasion by exotic species would be expected to occur for each of the types of human-caused changes in environmental conTilman and Lehman straints summarized above. In essence, a given habitat has various factors that constrain the fitness of the organisms that live there, and there is a trade-off surface that defines the potential responses (both within and among species)
|
From page 50... ...
3. Numerical solutions of evolutionary change in a weedy species growing in a spatially implicit habitat in which fitness is limited both by dispersal ability and by competitive ability, based on a model of phenotypic diffusion (36)
|
From page 51... ...
In total, this process suggests that the imposition of novel environmental constraints would lead to the eventual diversifi cation of the flora of a region, with the new flora filling in the empty niches created by novel human-caused environmental conditions. The process by which this is predicted to occur is one in which the ancestral progenitors of this new flora are small, fast-growing, weedy species.
|
From page 52... ...
(1986) in Community Ecology, eds.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.