Conservation Biology? Where ? When? How ? Why?

WHERE?  ............. IN THE WORLD

WHEN? .................IMMEDIATELY!

HOW?....................PROTECT AND RESTORE BIODIVERSITY, INCLUDING UNDERSTANDING AND MINIMIZING HUMAN IMPACTS ON THE NATURAL WORLD.

EDUCATE, EVALUATE, ANALYZE, PROTECT AND RESTORE

WHY?.....................THE WELFARE OF THE HUMAN SPECIES (ECOLOGICAL, ECONOMIC AND HUMAN) REQUIRES THE PRESERVATION OF BIODIVERSITY.

WHAT DO YOU THINK?

HOW, WHEN, WHERE TO INTERVENE FOR CONSERVATION?

HOW?

• KEEP THE EVOLUTIONARY POTENTIAL

• ALLOWING SPECIES TO CHANGE

 WHAT TIMESCALE?

• AVOIDING CURRENT EXTINCTION

• KEEPING THEM EVOLUTIONARY POTENTIAL

• KEEPING THEM POTENTIAL SPECIATION

WHAT TO KEEP?

• CHARACTERS THAT MAKE A GROUP DIFFERENT

WHEN YOU HAVE TO ACT?

• WHEN THE POPULATION IS AT RISK?

• WHEN THE SPECIES IS IN DANGER?

Molecular Markers as Tools for Genetic Diversity Analysis

In the last 20 years molecular genetics has used a lot of neutral molecular markers such as microsatellites in different studies of population biology, which has allowed to know and evaluate the impact of genetic drift on the diversity of genes in populations, the gene flow within and between populations and the degree of inbreeding present in populations. Recent technological advances in molecular biology allow the scanning of the entire genome; gene expression pattern is useful to make actual estimates of the level of genetic variation within individuals of a population and among populations becoming thus a tool for conservation biology.

Conservation genetics is a growing field as revealed by the increasing numbers of papers published on this topic over the past ten years. The graph shows the frequency of papers containing the term ‘conservation genetics’ and the respective name of the marker in a Web of Science search :(http://thomsonreuters.com/products_services/science/science_products/a-z/web_of_science) plotted against time. The total number of papers has increased from four in 1990 to 682 in 2009.

Reference:
Ouborg NJ, Pertoldi C, Loeschcke V, Bijlsma R, Hedrick PW (2010). Conservation genetics in transition to conservation genomics. Trends Genet 26: 177-187. http://dx.doi.org/10.1016/j.tig.2010.01.001

Genomics and the Future of the Conservation Genetics

A temporal framework for conservation biology

The tree used here is based on the history of sea turtles inferred from molecular sequence comparisons (Bowen & Karl 1996; Dutton et al. 1996). The process of conserving sea turtles may start with the systematists identifing seven extant species which require protection. Subsequently, ecologists identify the key habitat features that allow sea turtles to survive and thrive on an ecological timescale of a few tens of thousands of years. Finally, evolutionary biologists identify the raw materials for future prosperity and diversification. See figure 1

The temporal framework for setting conservation priorities allocates responsibilities in three distinct temporal spheres (past, present, and future) to three disciplines (systematics, ecology, and evolution). 

Reference:

1. Bowen, Brian W. Preserving genes, species, or ecosystems? Healing the Fractured Foundations of Conservation Policy. Molecular Ecology (1999), S5–S10.

Conservation genetics targets to conservation genomics

What is the central objective of conservation genetics?

Learn to understand and reduce genetic problems of different populations such as the Florida Panthers  (Felis concolor), the Puerto Rico parrots (Amazona vittata), the Royal Island wolves (Canis lupus), bighorn sheep (Ovis canadensis), the woodpecker (Dendrocopos medius) and the Asiatic lions (Panthera leo persica), among others (Hedrick, 1995; O'Brien, 1994; Frankham et al., 2002). Different genetic factors may be involved the loss of genetic variation and inbreeding depression have received the most attention therefore be treated more carefully. Small populations are more vulnerable because different stochastic factors (demography, environmental and catastrophic) accelerated its decline and lead to two vortices of extinction.  See figure 1

REFERENCES:

1. O’Brien S. J. 1994. A role for molecular genetics in biological conservation. Proc. Natl.Acad. Sci. 91:5748-5755.


2. Hedrick P.W. 1995. Gene flow and genetic restoration: the Florida panther as a casestudy. Cons. Biol. 9:996-1007.


3, Frankham R., J.D. Ballou, y D.A. Briscoe. 2002. Introduction to conservation genetics.Cambridge, Reino Unido.

Candidate Gene, Genome Scanning and Association Mapping Approaches

As we mentioned on our last post, there are different approaches for answering conservation-related questions, using population genomics techniques. Today, we are going to describe three of them.

A candidate gene is a gene known to have a biological and or functional impact on a specific trait or disease. Usually, the candidate gene approach is used in case-control studies in which mutations on a certain gene (or genes) are analyzed. For example, to identify genetic risk factors for complex disorders such as alcoholism, this approach tests the effects of genetic variants of a potentially contributing gene in an association study [1].

The genome scan approach identifies marker loci that are linked to selectively-relevant target loci through ‘genetic hitch-hiking’ [2].

v  Marker loci: DNA sequence with a known location on a chromosome that can be used to identify individuals or species

v  Genetic hitch hiking: process by which an allele may increase in frequency by virtue of being linked to a gene that is positively selected [3]

ü  Positive selection: increases the prevalence of adaptive traits

Method of mapping quantitative trait loci that involves searching for genotype-phenotype correlations in unrelated individuals [4].

v  Quantitative trait: a trait that has measurable phenotypic variation and/or environmental influences. Two classic examples of quantitative traits are height and weight. The loci that modulate these traits are therefore called QTLs [5].   

References:                        

[1] "The candidate gene approach". Alcohol Res Health 24 (3): 164–8. 2000. PMID 11199286.

[2] Smith, J.M., Haigh, J., 1974. Hitch-hiking effect of a favorable gene. Genet. Res. 23, 23–35.

[3] Barton, N H (2000-11-29). "Genetic hitchhiking". Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences 355 (1403): 1553–1562.

[4] Myles S, Peiffer J, Brown PJ, Ersoz ES, Zhang Z, et al. (2009) Association mapping: critical considerations shift from genotyping to experimental dsign. Plant Cell 21: 2194-2202.

[5] Abiola O, Angel JM, Avner P, et al. (2003) The nature and identification of quantitative trait loci: a community’s view. Nat Rev Genet. Nov;4(11):911-916. 

Conservation via Population Genomics Approaches

Population genomics can be briefly described as the use of genome-wide sampling to identify and separate locus-specific effects from genome-wide effects [1].

Although there are different approaches for population genomics, they all share the following basic steps [1]:

 

When answering a conservation-related question using population genomics techniques, the following approaches are available:

Want to know more about these approaches? A thorough description will be available on our next post. Stay tuned!

References:

[1] Luikart, G. et al. (2003) The power and promise of population genomics: from genotyping to genome typing. Nat. Rev. Genet. 4, 981–994.

Conservation Genetics or Genomics?

For all of you who, like me, are new to this field, a brief description of both conservation genetics and genomics would come in handy. According to Ouborg et al. (2010), conservation genetics is characterized by assessing relationships between population size and neutral sequence variation. But, what is neutral sequence variation? Well, there is a theory called The Neutral Theory of Molecular Evolution; it will help us understand what neutral variation is.

According to The Neutral Theory of Molecular Evolution, the vast Majority of evolutionary changes at the molecular level are caused by random drift of selectively neutral mutants which do not affect fitness, therefore referred to as neutral. [1]

On the other hand, conservation genomics assesses relationships between population size and both neutral and selectively important variation, both in terms of sequence variation and gene expression variation, and thereby incorporates potential effects of selection. Conservation genomics also incorporates the influence of environmental conditions on sequence variation (via selection) and on gene expression variation. [2] 

[2]

References:

[1] Kimura, M (1983). The neutral theory of molecular evolution. Cambridge (page xi)

[2] Ouborg NJ, Pertoldi C, Loeschcke V, Bijlsma R, Hedrick PW (2010). Conservation genetics in transition to conservation genomics. Trends Genet 26: 177-187. http://dx.doi.org/10.1016/j.tig.2010.01.001