Introduction to Conservation Genetics: Take Home Messages

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Throughout the book we focus on a number of primary concepts that define the core of conservation genetics. At the end of the book we have included a final section summarizing these main messages:

1. The biological diversity of the planet is being rapidly depleted due to direct and indirect consequences of human activities (habitat destruction and fragmentation, over-exploitation, pollution and movement of species into new locations).
2. The major genetic concerns in conservation biology are inbreeding depression, loss of genetic diversity, genetic drift over-riding natural selection, population fragmentation, genetic adaptation to captivity, and taxonomic uncertainties.
3. Inbreeding, loss of genetic diversity and loss of adaptive evolution are inevitable in all small closed populations.
4. Inbreeding has deleterious effects on reproduction and survival (inbreeding depression) in almost every species that has been adequately investigated.
5. Loss of genetic diversity reduces the ability (evolutionary potential) of populations to adapt in response to environmental change. Quantitative genetic variation for reproductive fitness is the primary component of genetic diversity involved in adaptive changes.
6. Genetic factors generally contribute to extinction risk, sometimes having major impacts on persistence.
7. Ignoring genetic issues in the management of threatened species will often lead to sub-optimal management and in some cases to disastrous decisions.
8. The objective of genetic management is to preserve threatened species as dynamic entities capable of adapting to environmental change.
9. The first step in genetic management of a threatened species is to resolve any taxonomic uncertainties and to delineate any management units within species. Studies using genetic markers can typically aid in resolving these issues.
10. Genetic management of wild populations is in its infancy and is not generally adequate or optimal to ensure long term viability (largely because genetic issues are often ignored).
11. The greatest unmet challenge in conservation genetics is to manage fragmented populations to minimise inbreeding depression, loss of genetic diversity and loss of adaptive evolution. Translocations among isolated fragments, or creation of corridors for migration are required to minimise extinction risks, but they are being implemented in very few cases. Concerns about possible outbreeding depression (often exaggerated) have discouraged translocations to address the impacts of population fragmentation.
12. Captive breeding provides a means for conserving species that are incapable of surviving in their natural habitats. Captive populations of threatened species are typically managed to retain 90% of their genetic diversity for 100 years, using minimisation of kinship.
13. Genetic deterioration in captivity resulting from inbreeding depression, loss of genetic diversity and genetic adaptation to captivity, reduces the probability of successfully reintroducing species to the wild.
14. Population sizes of N_e much greater than 50 (N > 500) are required to avoid inbreeding depression and N_e = 500-5,000 (N = 5,000-50,000) are required to retain evolutionary potential. Many wild and captive populations are too small to avoid inbreeding depression and loss of genetic diversity in the medium term.
15. Molecular genetic analyses contribute to conservation by determining the genetic structure of populations, aiding detection of illegal hunting and trade, and by providing essential information on unknown aspects of species biology.
16. Genetic factors represent only one component of extinction risk. Wild populations face threats from both deterministic factors (habitat loss, over exploitation, introduced species and pollution) that contribute to population declines, and stochastic factors (demographic and environmental stochasticity, catastrophes and genetic stochasticity) that become increasingly important in small populations. Genetic factors typically interact with other factors.
17. The combined impacts of all ‘non-genetic’ and genetic threats faced by populations can be assessed using population viability analysis (PVA). PVA is also used to evaluate alternative management option to recover threatened species.

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