Section II: Genetic Resource and Land Capability

11

Genetic Diversity in Natural Resources Management

Introduction....................................................................................................87

What Is Genetic Diversity?

How Can Genetic Techniques Inform Management Decisions?.............88

Demographics and Extinction Risk • Resolving Taxonomic Status and Determining Relevant Conservation Units • Determining Population Structure • Captive Breeding Programs • Managing Invasive Species • Wildlife Forensics • Crop and Livestock Management • Genetic Ecotoxicology

How Is Genetic Diversity Measured and Interpreted?..............................92

Conservation Genomics................................................................................93

omas Josep Spatial Analyses of Genetic Diversity..........................................................94

McGreevy Conclusion.'........................................ 95

Boston University . . , , ~.

Acknowledgments..........................................................................................96

Jeffrey A. Markert References........................................................................................................96

Providence College Bibliography....................................................................................................99

Introduction

What Is Genetic Diversity?

Genetic diversity is the amount of variation in the sequence of four nucleotides (adenine, thymine, cytosine, and guanine) that comprise deoxyribonucleic acid (DNA) within individuals, populations, or species. The particular combination of nucleotides within an individual is called a genotype.111 From an information theoretic approach, population genetic diversity represents the amount of information stored in DNA within a population above and beyond the information common to all individuals.12,31 Thus, genetic diversity represents the maximum amount of information available to code for distinct physical characteristics (phenotypes) within a group. Less information means fewer distinct phenotypes, decreasing the likelihood that some individuals in a population have characteristics suited to the next environmental challenge. These challenges may include things like new diseases, introduced predators, or altered physical environments. In diploid organisms, inbreeding depression-like effects also may reduce individual fitness when both copies of a segment of DNA within an individual are identical. The probability of this occurring is higher in populations with lower genetic diversity.

From a wildlife management perspective, we would expect that groups with lower levels of genetic diversity are at greater risk for extinction. Experimental studies support this expectation. For example, when genetic diversity is experimentally manipulated in isolated plant populations, those with lower genetic diversity are dramatically less fit.141 Similarly, work using short-lived crustaceans as a model shows that even minor losses of genetic diversity greatly increase extinction risk when low-diversity populations are challenged with suboptimal environments.151

The importance of conserving genetic diversity is recognized by the International Union for Conservation of Nature (IUCN) as a major component of biodiversity.111 In the United States, genetic diversity has been recognized as an important resource that should be conserved since the drafting of the Endangered Species Act (ESA) of 1973. Further rationale for why genetic diversity matters was explained by the House of Representatives in House Resolution 37, the precursor to the ESA of 1973:161

“From the most narrow possible point of view, it is in the best interests of mankind to minimize the losses of genetic variations. The reason is simple: they are potential resources. They are keys to puzzles which we cannot yet solve, and may provide answers to questions which we have not yet learned to ask.”

There are still important puzzles to solve and unasked questions in conservation genetics. In the past 40 years, researchers have developed and refined a strong set of genetic tools that address key aspects of conservation biology. These techniques have been used to inform management decisions for wild and captive populations since the 1980s, but the full utility of these tools is yet to be realized.171 One major limitation has been the communication disconnect between research scientists and resource managers in some jurisdictions. The first goal of this entry is to help bridge this gap by providing an overview of the type of information that can be gained with molecular genetic techniques to inform a wide range of management decisions. The second goal is to discuss future directions that will reduce the cost and expand the utility of molecular genetic techniques in the management of natural resources.

 
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