without having to isolate and cultivate them individually. For 

 example, using nucleic-acid sequencing, microbes can be identified 

 from ribosomal RNA, as well as from genomic DNA. These techniques, 

 described in Appendix III, are applicable to natural ecosystems 

 with highly diverse microbial communities and consortia. 



Several questions, set out below, are critical to determining 

 the trajectory of ecosystem structure and function under 

 environmental alterations. The answers provide critical 

 information about how the biological systems will be affected by 

 environmental perturbations, and will themselves affect the 

 environment. 



1. How does chronic stress alter species diversity? 



a) What rate of environmental change causes species 

 diversity to change? 



b) What is the trajectory of change in species diversity as 

 a function of increasing perturbance? 



2. What is the relationship between functional redundancy and 

 species diversity? What is the effect of stress on functional 

 redundancy? 



3 . How will changes in environmental variance affect genetic 

 diversity within a population? 



a) Is genetic diversity independent of environmental change 

 or related to it? 



b) How is intraspecific genetic diversity affected by 

 competition? 



c) How does intraspecific genetic diversity affect the rate 

 of change in functional redundancy during stress? 



Many of these questions can be addressed by molecular 

 biological techniques; indeed, in many cases, molecular biology has 

 had its greatest impact in ecology in elucidating community 

 structure and diversity. Techniques which exploit pattern 

 differences (polymorphisms) in nucleic acid restriction fragments 

 (RFLPs) , and the rapidity and ease of use of the PCR can be used to 

 assay intraspecific genetic diversity. Comparative analyses of 

 nucleic acid sequences, particularly of rRNA sequences, are 

 revolutionizing our understanding of microbial diversity and 

 phylogenetics. In addition, sequence analyses provide information 

 for designing species or group-specific hybridization probes that 



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