Evolution: The grey treefrog looks identical to the closely related cope’s treefrog, so much so, that even their DNA is almost identical. Both these frogs were at one point the same species. Some copes treefrogs were born with a mutation where instead of having the normal two sets of chromosomes, they had four. Those with four sets were able to breed with other individuals with the same mutation. They could not however, successfully breed with those with only two sets of chromosomes, separating them genetically. These frogs developed in genetic isolation from the copes treefrogs to the point that their calls became slower and lower pitched while physically, they remained the same. These became the grey treefrogs, also known as the tetraploid grey treefrog and can only be identified through their genetics, range, and of course, their call.
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Natural History: Come winter, grey treefrogs are able to freeze solid. For some populations, as soon as external temperatures reach -5°C (23°F), roughly 41.5% of the water in their bodies begins to freeze, holding them in suspended animation. In spring, they are able to thaw out completely unharmed. If humans were to do this, the cells in the body would die from ice forming within them. Grey treefrogs avoid this due to the glycerol that forms in the liver, glycerol is spread throughout the body through the blood stream and helps to protect the cells from desiccation and freezing. Urea also plays a role, this waste product clings to the cells of the frogs, helping to stop them from shrinking. This process is found in a number of frog species but with slight differences. Wood frogs are a classic example, although instead of glycerol, they use glucose that they converted from glycogen.
Conservation: Grey treefrogs are affected by the cutting of trees but not in the way one would expect, clearcutting in particular, has been found to have a positive affect on many developing grey treefrogs. Tadpoles that grow in ponds in clearcut areas have been found to develop quicker and with a higher success rate than their forest counterparts. The reason for this is still not well understood, though, the froglets in clearcut areas tend to be smaller, which may subject them to more predators in the future. While clearcutting may be beneficial to developing treefrogs, it can also help some species of tree. By allowing enough intact forest nearby, many slow growing trees or those that need direct sunlight, such as aspen and black cherry, can recolonize without having to compete with faster growing species. In contrast, selective cutting, only taking specific trees in a forest, creates small gaps of sunlight which fast growing species can easily make use of. If done right, both methods can be sustainable and allow for a balance between human use and nature.
Phenotypic Plasticity: A dragonfly larva waits beneath submerged vegetation. The contrasting red tail is his cue to strike. His mouthparts protrude with great speed but they only clip the thin membrane of a tail fin as the tadpole makes his escape. Grey treefrog tadpoles display phenotypic plasticity where individuals physically change to adapt to different environments. Stress hormones, induced by excessive levels of predation, cause the body to react by having their tail become taller, more blunt and red with contrasting dark blotches. These colours do not warn of any toxins but instead distract predators from their more delicate head and body. Tadpoles in wetlands with fewer predators will have a more slim tail, with little to no colouration, and be more active than their red counterparts. While dragonfly larva are their main predators, these tadpoles also fall prey to water scorpions, snakes, other amphibian larva, and even Blanding’s turtles as was observed.
Sources:
"Gray Treefrog." Ontario Nature, 2021, ontarionature.org/programs/community-science/reptile-amphibian-atlas/gray-treefrog/. Accessed 4 Nov. 2021. Hocking, D J., and R D. Semlitsch. "Effects of Experimental Clearcut Logging on Gray Treefrog (Hyla versicolor) Tadpole Performance." Bio One, Journal of Herpetology, 1 Dec. 2008, bioone.org/journals/Journal-of-Herpetology/volume-42/issue-4/07-294R1.1/Effects-of-Experimental-Clearcut-Logging-on-Gray-Treefrog-span-classgenus/10.1670/07-294R1.1.short. Accessed 4 Nov. 2021. Mills, Peter B. Metamorphosis. self-published, 2016, pp. 60-63. Parker, William C., et al. "Influence of Woody and Herbaceous Competition on Microclimate and Growth of Eastern White Pine (Pinus strobus L.) Seedlings Planted in a Central Ontario Clearcut." Science Direct, Forest Ecology and Management, 10 Oct. 2009, www.sciencedirect.com/science/article/abs/pii/S037811270900526X. Accessed 4 Nov. 2021. Storey, Janet M., and Kenneth B. Storey. "Adaptations of Metabolism for Freeze Tolerance in the Gray Treefrog, Hyla versicolor." Ken Story lab, Carleton University , 5 June 1984, www.kenstoreylab.com/wp-content/uploads/2016/03/Adaptations-of-metabolism-for-freeze-tolerance-in-the-gray-tree-frog-Hyla-versicolor.pdf?fbclid=IwAR3hRDUfYEki4_fPxNowPeZkIZuJuhJK3QKIK6hbmWaBFDS. Accessed 4 Nov. 2021. Vrijenhoek, Robert C. "Polyploid Hybrids: Multiple Origins of a Treefrog Species." Science Direct, Current Biology, 4 Apr. 2006, www.sciencedirect.com/science/article/pii/S096098220601253X. Accessed 4 Nov. 2021. |