Conservation genetics of forest trees in the era of rapid environmental changes: from descriptions to applications

I organize a small workshop, which is entitled as above, on April in Tsukuba, during the 121th annual meeting of Japanese Forest Society. Here is rough draft of my idea for the workshop.

Conservation genetics is one of the study area within conservation biology, which aimed to minimize the exiting risk of species due to genetic consequences. In addition, it could also be defined as resource management science, which aimed to ensure sustainable use of biological resources using genetics as tools and guidelines in terms of rapid environmental changes.

In early 1990s, conservation genetic was incorporated into forest science. In 1992, F. Thomas Ledig published a paper which discussed human impact of genetic diversity in forest ecosystems. As far as I know, "genetic diversity" itself was central issue during the early age of conservation genetics, and the factor affecting to genetic diversity such as inbreeding, fragmentation or range contraction was also discussed. In fact, many of study was addressed to description of genetic diversity and mating system of small populations at that time.

However, implications from those studies was limited for conservation practices. While genetic diversity of small population was well discussed, the role of genetics in conservation biology was still anecdotal. Questions came up, "How much genetic diversity should we keep?", "How do we incorporate the genetics in management practices", and "What is genetic diversity?".

Genetic diversity is metrics or indicator of population viability. Processes which affect to (neutral) genetic diversity should be similar to processes which affect to species diversity, and thus it should reflect the impact of previous and current perturbation to population, in terms of fragmentation and range contraction. In addition, inbreeding may result in reduction of population viability because of deleterious genes.

Thanks to advances in statistical modelling technique and genetics analysis, recent studies have addressed to quantitative assessment of process which affected genetic diversity, and thus to population viability. Next challenge in area is providing a framework for conservation planner to minimize the impact to genetic diversity and population viability, such as genetic population viability analysis under multiple scenarios.

Another issue in conservation genetics is climate change. Earth's climate is changing as rapidly as which tree species has never been experienced and considerable attention has focused on the fate of forest and forestry. Species often adapted to local environment, and they may be able to adapt to environmental changes, which enabled by genetic diversity within population. Thus, researchers have focus on mechanism of local adaptation since last couple of years.

Classically, evidence of local adaptation was well tested by provenance test or common garden experiment in forestry. Most of results from those studies supported the trees have adapted to along with latitudinal and altitudinal gradient, and it was reflected to seed transfer guidelines for plantations.

In terms of climate change, researchers are discussing to change seed transfer guideline to enable track species to optimum climate niches, which is so-called "assisted migration" or "managed relocation". Forestry department of BC Canada have already started the trial of assisted migration in major species in forestry (see Nature's article for detail). In fact, there are still strong resistance to assisted migration among researchers. But starting trial from now may be necessary to prepare for taking action in future. There is still a lot of uncertainty in this topic.

Rapid evolution of species to adapt new environment should also be incorporated to conservation genetic in terms of climate change. Using a theory of quantitative genetics, Russell Lande proposed a maximum limit of environmental change which species could adapt to. Also empirical evidence of rapid evolution along with environmental change was found in higher animals, for example three-pined stickleback and Darwin's finch. But, theoretical and empirical knowledge in forest trees is scare.

Furthermore, recent advances in genomics have enabled us to investigate the genes which responsible for local adaptation. Currently, the result is restricted in few adaptive traits in few major species in north America and Europe. To my knowledge, however, some big genomics projects are still intensively addressing to this issue. I hope the result from those genemics project become applicable to conservation genetics in near future.

Finally, I would like to emphasize the necessity to incorporate resource inventory, economics and policy making into conservation genetics. As the focus of conservation genetics become broader to regional, national or international scale, conservation cannot be restricted to natural science, rather effective management of genetic resources and policy making which considering the scientific knowledge are required to archive objectives.

In this workshop, I would like to invite several speakers to discuss those issues.

Needs for assisted migration?

Rapid climate change has already caused changes to habitat for plant and animal species, leading to local extinction of some species, if species could not recolonize to new habitat or adapt to local environment. The subject of assisted migration (or managed relocation), which intends species to transfer to the suitable habitat outside of species range, has become common for couple of years.

When I learned about the subjects of assisted migration, I could not accept it as the real matter at first. But now, I have realized that the needs for the assisted migration is became widely accepted, as the risk of species extinction has been evaluated from the myriad researches such as long-term ecosystem monitoring and climate-niche model studies. Actually, some guidelines to decide assisted migration has already been proposed.

On the other hands, some researchers have questioned whether assisted migration would be an effective strategy to conservation, because of its risks. Transferring the species to the outside of the original species range cause similar problems as invasion of exotic species to recipient habitat: extirpation of local species, introduction of new pests and herbivore, and hybrids between local and introduced species have already been reported. Consequently, they insisted that the risks of assisted migration were often uncertain, and precautionary principle which species should not be transferred to the outside of habitat should be undertaken.

Discussions on this topic has been continued on TREE. Majority of them insisted that the necessity of individual and qualitative assessment of needs, benefits and risks of assisted migration, albeit to precautionary principle. On the contrary, one mentioned that assisted migration is not a fundamental solution to prevent extinction, but a "techno-fix".

The problem underlying the transfer of species along with climate change is slightly different from other problems on conservation biology. Existing problems such as habitat degradation or invasive species probably have "ideal states", which is preservation of habitat or original state before invasive species had been introduced. However, loss of habitat due to climate change does not have such "ideal state", rather the situation is continued to be getting worse, and may not be recovered. The motivation is to make a situation to better, at most. Therefore "do-nothing policy" may not be a better solution, and precautionary principle could not be applied to this type of problem.

As the most of authors pointed out, the vulnerability of species to extinct with climate change, and the potential risks underlying assisted migration are often uncertain. Small scale experiment of assisted migration in various endangered genera or species should urgently be taken to reduce uncertainty.

Original article:http://motoshi.tk/index.php?Web%C6%FC%B5%AD%2F2009-07-13