Conservation biology is an eclectic field of research drawing from fields of biology such as evolution, ecology, population genetics, and phylogenetics with the goal of protecting and conserving biodiversity on Earth. Among these fields, the study of evolution has vastly influenced conservation biology and made the field possible in many ways. Evolution played a key role in changing our mindsets to a point where conserving biodiversity made sense. It also gave conservation biologists the tools needed to analyze populations and communities. In addition, the process of listing rare species is dependent on theory provided by evolution.
Evolutionary theory changed our mindset about our role in nature
If you think about how humans viewed their role in nature before evolutionary theory became ubiquitous, you will find that it was fundamentally different the way we view it today. For example, Aristotle’s scheme for classifying life conveyed the idea that all life is organized as a gradient from simple to complex with humans being the most complex form of life. Although several early philosophers, such as Lao Tsu (the founder of Taoism), encouraged the concept of conservation, it wasn’t until there was a paradigm shift in the way that we view life on earth that conservation biology could really happen. In fact, even with early naturalists, rare species were specifically sought out because they were considered valuable collections (Farber). Philosophically this paradigm shift consisted of several realizations: the earth is old, life changes over time, the degradation of teleology as a form of reasoning, and humans are a part nature (Bowler).
Although Charles Darwin’s mechanism of natural selection was not initially well accepted, once his ideas were synthesized with those Gregor Mendel there was an explosion of new research. Scientists were beginning to understand concepts such as what causes invasive species to proliferate, how changes in the allele frequencies happen in populations, and overall more about the diversity of life. Many of these fields of research are what conservation biology draws upon. When Theodosius Dobzhansky said that “nothing in biology makes sense except in the light of evolution”, that certainly includes the field of conservation biology.
Evolution gives conservation biologists tools for analyzing populations and communities.
Through development of the field of population genetics, scientists began to realize that diversity within a population can be necessary for the population to adapt to changing environments. In addition, small population sizes were found to decrease genetic diversity through genetic drift (see Freeman and Harron, section 7.5).
With ideas from the field of ecology, conservation biologists have developed methods of estimating the future of a population given rates of survival and reproduction. The tracking and monitoring of life history stages in plants is called plant demography. The idea behind it is that if you find the rates of survival and development in a sample of individuals you can estimate whether the population will grow, shrink, or stay the same size. One example of a species being monitored for the rate of decline is Calochortus howellii, a serpentine endemic Lily of South Western Oregon. In the early 1990’s Dr. Nancy Fredericks used demography to predict the population size every year up to the present. Our lab has been monitoring the Calochortus howellii since 2006, 16 years since Dr. Fredericks made her predictions, and found that the effective population size of the population has been reduced due to a large amount of fruit and underground bulb herbivory. This has caused the population to shrink outside of the confidence intervals predicted by Dr. Fredericks and is therefore unlikely to be due to the rate of decline she predicted. Currently we are planning on creating exclusion fences to reduce capsule herbivory to see if that will increase the population size to the rate she predicted.
Drawing from concepts of biogeography we can learn why many species are restricted to specific localities. For example, Calochortus howellii, unlike most plants, can tolerate the high magnesium and low calcium concentrations in the soil. Our lab has hypothesized that it is restricted to serpentine soils not because of its physiology, but simply because it is outcompeted on non-serpentine soils (Procter and Woodell).
But not only rare plants can tolerate serpentine soils. One current project my lab is working on is assessing the threat of an invasive, serpentine tolerant weed in the mustard family called Allysum murale. Allysum murale concentrates heavy metals in some of its leaves as an adaptation to allow it to live on a variety of otherwise uninhabitable sites. It was planted in SW Oregon with the intention of smelting the leaves to mine for nickel. Currently it is spreading wildly through SW Oregon’s serpentine habitat and threatens to out-compete many rare native species restricted to the area, such as Calochortus howellii. Through understanding evolution we can hypothesize that the population is increasing dramatically due to the lack of selection pressures present in its native habitat. We also know that this area should be considered a very important habitat given the rare plant species there that have a unique evolutionary history, and provide much biodiversity to SW Oregon.
Evolutionary theory provides criteria for species protection status.
One of the first steps in establishing a conservation plan for any rare plant is to determine species distribution and habitat associations. However, if this rare species is difficult to distinguish from sympatric species based on morphological characters, or if the taxon’s status is questionable, these inconsistencies introduce a layer of ambiguity which can hamper the process of listing the plant for protection.
One of my first projects when joining my lab was to determine whether Sisyrinchium hitchcockii, a rare Iris, constituted a valid species. Two very similar taxa, S. idahoense and S. bellum, overlap its range and the keys currently being used to distinguish it relied on underground characters (which would require the plant being dug out of the ground). We compared these three species from three major aspects: morphology, chromosome number, and molecular analysis. After combining our phylogenetic tree with data from other species of Sisyrinchium on genbank, we had a fairly good idea about the evolutionary history of the species. Once we mapped the chromosome numbers on the tree we noticed that there were several polyploidy events which we think precipitated the speciation of Sisyrinchium. Given the results of our morphological data we were able to compile a taxonomic key, using characters in the flowers, to distinguish S. hitchcockii from other closely related Sisyrinchium species. Because of the uniqueness in its morphology, chromosomal polyploidy, and non-coding DNA, we found that S. hitchcockii should be considered a valid species. Currently we are trying to publish our data in order to ensure the protection of the species.
Conclusion
Through working on many rare species recovery projects I believe that my research has been related to evolution greatly. Conservation biology wouldn’t even have been a field of science if we truly believed that we were the most important species on Earth. Much of the research necessary for understanding the reason a species is rare and methods to augment the population rely on an understanding of evolutionary theory. Evolution is so important that a unique evolutionary history is a major criterion for protecting the species. Today evolutionary theory continues to shed light on questions in conservation biology.
References
Bowler, P, J. 2003. Evolution: The History of an Idea, 3rd ed. University of California Press.
Farber, P, L. 2000. Finding Order in Nature. John Hopkins University Press.
Freeman, S, and J. Herron. 2007. Evolutionary Analysis, 4th ed. Pearson Benjamin Cummings.
Procter, J. and S. Woodell. The Ecology of Serpentine Soils. Advances in ecological research (9)
Pgs. 255-366.
Web resources
My lab’s website:
http://www.oregon.gov/ODA/PLANT/CONSERVATION/index.shtml
A website with many conservation biology resources:
http://www.istl.org/06-winter/internet1.html
The Angiosperm Phylogeny website (just because it’s cool): http://www.mobot.org/mobot/research/apweb/
Botany Photo of the Day (if you subscribe they will email you cool photos of plants and info about them):
http://www.botanicalgarden.ubc.ca/potd/
Whenever I think of evolution and conservation biology, I think of them in terms of animals. I forget that these concepts have important implications for plants as well. I don't have much knowledge about or interest in plants and so it was good to read an article discussing plants from a perspective I can relate to.
ReplyDeleteYou said that, in the case of the C. howellii, your lab has hypothesized that restriction to a specific locality is due to being out-competed rather than physiology. Would you assume that the ability of the Lily to tolerate the harsh conditions of high magnesium and low calcium to have evolved, or at least been magnified, since finding a "niche" in the serpentine soil? Was it found in both soil types before being out-competed or was it able to build on the little tolerance it had and therefore proliferate in the serpentine soil?
I think it's awesome that you were able to determine that Sisyrinchium hitchcockii was a valid species and create a key to identify it from the other species. Were the other two species, S. bellum and S. idahoense, too similar morphologically to be keyed out using morphology? Why were they dependent on underground characters?
"Conservation biology wouldn't even have been a field of science if we truly believed that we were the most important species on Earth."
Just a thought - sometimes I question the motives of some conservationists. It seems as if some of them do believe that humans are the most important species, and are working to conserve other species because of selfish motives. Preservation for future generations may not be a selfish goal for an indvidual, but sounds selfish in terms of the human race. Conservation by the humans for the humans.
This comment has been removed by the author.
ReplyDeleteI had never really thought about evolutionary theory paving the way for conservation biology, but it does make a lot of sense. The ancient "Ladder of Nature" type of mindset really didn't lend to the conservation of rare flora and fauna, and Darwin's idea of humans as just another beast could certainly shift that mindset of humans as these special masters of all things to humans being simply another creature that natural selection is working on.
ReplyDeleteOne thing I always found interesting about evolution and conservation biology, however, is the idea of interfering with nature when it may be taking its natural course. Take the spotted owl for instance. Barred owls from the east are slowly creeping their way west and mating with the spotted owl, creating a hybrid that is often times more fit for the environment than the spotted owl. Barred owls themselves are also taking over. With the hybrids diluting the spotted owl gene pool and barred owls shoving them out of their habitat, the spotted owl is in very real danger of becoming extinct, especially in places like British Columbia. There are many people who are attempting to stop this from happening in an attempt to save the spotted owl. But you have to ask, is this just evolution taking place? This new organism is more fit for environment, so shouldn't it be "survival of the fittest"? Of course it's not that simple, because there's the problem of humans being at fault, and the spotted owl being a creature many want to keep on this earth. But then again, it is completely natural for species to go extinct. Where do we draw the line between trying to save all the biodiversity we can in this world, and letting evolution take its course?