CU Researcher: More accurate species delimitation could help us protect biodiversity more effectively
Zoologist Daniel Jablonski from Comenius University studies how a more balanced and innovative perception of biodiversity could help us protect it more effectively. A paper authored by three researchers and based on current trends in DNA research was recently published by the Proceedings of the National Academy of Sciences (PNAS), a renowned, U.S.-based interdisciplinary journal.
By: CU External Relations Office
At present, over a million species of organisms living on Earth have been described but many more are still waiting for a taxonomic delimitation, or description. By describing living or extinct organisms and cataloguing them we can research them and understand the processes of evolution and ecology. As a result of this work, national and transnational lists are compiled and effective protection can be ensured. Wildlife legislation in many countries depends on described species and that leads to an explosion of efforts to classify every genetically distinct population as a new species. This causes a phenomenon sometimes called 'taxonomic inflation'.
"Defining a species is sometimes not as easy as we might assume. Some descriptions are based on surprisingly vague criteria, and the populations in question may not really represent separate species. This can artificially increase the numbers of species and destabilize their cataloguing," Daniel Jablonski from the Faculty of Natural Sciences of Comenius University explains the pitfalls of species classification. By designating each genetically distinct evolutionary lineage as a species limited nature conservation resources are diverted away from species that are truly at risk.
Daniel Jablonski therefore teamed up with molecular taxonomy experts Christoph Dufresnes and Nikolay Poyarkov to propose a standardized approach to the delimitation of species and subspecies, particularly among animals. They published their paper in the prestigious PNAS journal, issued by the National Academy of Sciences of the U.S. Their novel approach is based on genomic phylogeography and our knowledge of how speciation in nature occurs. "During the process of speciation, populations are isolated by geographical or ecological barriers and develop into separate lineages. When these lineages meet again by chance, they try to reproduce. The differences in their DNA that accumulated over time will cause their partial incompatibility. We found out that sister evolutionary lineages which were estimated to have diverged over three or four million years ago hybridize less readily than younger lineages. Lineages or populations are considered separate species if they have a limited rate of exchange of genetic information, and this could theoretically be one of the criteria for establishing whether specific lineages are species or not,” Jablonski explains.
The authors propose to describe genetically unique, but evolutionarily younger and reproductively still compatible lineages representing intraspecific diversity, as subspecies. In this way they can be given a scientific name, their evolutionary history can be studied, and they can be placed on red lists and protected. "Our proposal could satisfy the need to protect evolutionarily unique albeit reproductively compatible populations without artificially increasing the number of species. These lineages, which are also often endemic and play a huge role in the evolution of the species, are usually not specially protected. The reason is the fact that they are not described as species," adds Jablonski. One example is the recent description of the endemic populations of Chloe’s spadefoot toad Pelobates balcanicus chloeae, or the world's longest legless lizard Pseudopus apodus levantinus from the Middle East. Their discovery triggered an increased interest in these endemic populations and their protection. In practice, this new approach could make it possible to recognise higher biodiversity without increasing the number of species, so that protection of animals is more efficient and based on their evolutionary history.
The image shows Chloe’s spadefoot from Greece which represents an example of a young lineage that separated relatively recently, at the beginning of the Pleistocene, approximately two million years ago. In order to emphasize the genetic uniqueness of these amphibians, which still retain some reproductive compatibility with sister lineages of the species, and also to highlight the importance of their conservation, scientists have described this population as a separate subspecies Pelobates balcanicus chloeae.