In a study spanning over a decade, ecologists from the Michigan State University (MSU) concluded that diversity of snakes in a National Park in Central Panama has declined. The reason for this declination is clear according to data1 they published in Science. They find a clear pattern. Snake communities started to collapse after a fungal disease effectively wiped out local amphibian populations2. These amphibians served as food for the snakes.
The culprit fungus that killed the amphibians (like frogs and toads) was Batrachochytrium dendrobatidis2. It causes a disease called chytridiomycosis from which the amphibians could not recover leading to their decimation in 2004.
Ecologists were already conducting regular surveys in the area. When survey data was analysed, they observed that some snakes were becoming increasingly difficult to spot. They also noted that this decline in snake species richness began after the decimation of the amphibians. The snake species that showed maximum decline in detection were reported in the paper as follows:
- Rhadinaea decorata
- Sibon argus
- Clelia clelia
- Chironius grandisquamis
- Bothrops asper
- Leptophis depressirostris
- Leptodeira septentrionalis
- Rhadinaea vermiculaticeps
- Pliocerus euryzonus
On the other hand, there were also some species of snakes which showed increased detection, jeopardising the diversity1.
“Some species that are rare or hard to detect may be declining so quickly that we might not ever know that we’re losing them,” said Elise Zipkin, MSU integrative biologist and the study’s lead author. “In fact, this study is less about snakes and more about the general loss of biodiversity and its consequences.”
“We estimated an 85% probability that there are fewer snake species than there were before the amphibians declined,” Zipkin said. “We also estimated high probabilities that the occurrence rates and body conditions of many of the individual snake species were lower after the loss of amphibians, despite no other systematic changes to the environment.”
According to the researchers, this discovery is a perfect example of “cascading effects on biodiversity”. The loss of amphibians, as is happening globally, according to the researchers, is affecting other species, like these snakes. What else is this affecting? It is hard to tell. In the case of the snakes in Panama, researchers were already conducting surveys and chanced upon the discovery that snake populations were declining after the extinction of amphibians. However, researchers believe that this kind of cascading effects are increasingly common.
“But this phenomenon, in which a disturbance event indirectly produces a large number of ‘losers’ but also a few ‘winners,’ is increasingly common and leads to worldwide biotic homogenisation, or the process of formally dissimilar ecosystems gradually becoming more similar.”
“The huge die-off of frogs is an even bigger problem than we thought,” said Doug Levey, a program director in the National Science Foundation’s Division of Environmental Biology. “Frogs’ disappearance has had cascading effects in tropical food chains. This study reveals the importance of basic, long-term data. When these scientists started counting snakes in a rainforest, they had no idea what they’d eventually discover.”
Studies like these are informing us that basic data collection is a good practice. Such data will definitely help conservationists make informed forecasts and prevent large biodiversity loss, like with the Panamanian snakes, and any eventual cascading effects on biodiversity. Having said that I tend to always remember that the vast majority of species that ever lived on Earth are now extinct. Is this part of the biodiversity cycle (as species fade off, new species will take over)? Then, what’s the point of conservation? Aren’t we trying to take too much control of the “biodiversity”? I would like to hear your views. Post them in the “Reader Comments” section below and we can have a chat.
With inputs from MSU.
- 1.Zipkin, E. F., DiRenzo, G. V., Ray, J. M., Rossman, S. & Lips, K. R. Tropical snake diversity collapses after widespread amphibian loss. Science 814–816 (2020) doi:10.1126/science.aay5733.
- 2.Crawford, A. J., Lips, K. R. & Bermingham, E. Epidemic disease decimates amphibian abundance, species diversity, and evolutionary history in the highlands of central Panama. Proceedings of the National Academy of Sciences 13777–13782 (2010) doi:10.1073/pnas.0914115107.