Hyperolius viridiflavus ngorongorienis from Northern Tanzania. Lawson LP, HC Liedtke, M Menegon, SP Loader. 2018. Reproductive characteristics of two Hyperoliidae species (Afrixalus septentrionalis -Schiøtz 1974, and Hyperolius v. ngorongoriensis – Schiøtz 1975) from a miombo seasonal wetland in Northern Tanzania. Herpetology Notes 11:873-879. Many species of Hyperolius frogs have the curious trait of having polymorphic coloration. This means that individuals can be many different colors instead of a single color. As most species across vertebrates are fairly uniform in their coloration (either all males and all females are the same color, or all males are one color and all females are another color - sexual dichromatism), when you come across a species that is highly variable, the question that I usually think of is "Why?". What possible reasons would keep variation within a species?
One idea is to confuse predators. This is common in species where predators can get a "search image" for a certain coloration, which they then use to more quickly find individuals of that color. Whatever color is "rare" then ends up surviving and reproducing better. Which then leads to the population to shift towards more of the "rare" color individuals, which then are no longer rare...
Another possibility is that there may be fitness tradeoffs in the color morphs. In the common wall lizards native to Europe (Podarcis muralis), the yellow color morphs have more testosterone and have the associated traits of more aggression and more/smaller eggs than the red or white color morphs. They also have reduced immune responses that are also associated with higher testosterone (as seen in many species). These two life strategies, which I like to call "live fast and die young (yellow)" vs. "slow and steady wins the race (red and white)", are maintained in the species because different environmental years will favor different strategies. In a really great year with ideal weather and lots of food/resources, the yellow morphs can go to town reproducing a ton of offspring. In a poorer quality year, however, the red and white morphs will be more likely to have successful offspring because they will live longer and produce fewer eggs but with larger nutritional reserves in each egg so that each baby has a better chance of surviving in the harsh surroundings.
We don't know if there are fitness tradeoffs for the color morphs within Hyperolius species, but this would be a great area of future research. Overall, our understanding of Hyperolius frogs is still in its infancy (we are still naming many new species each year), but there is a lot left to learn!
One idea is to confuse predators. This is common in species where predators can get a "search image" for a certain coloration, which they then use to more quickly find individuals of that color. Whatever color is "rare" then ends up surviving and reproducing better. Which then leads to the population to shift towards more of the "rare" color individuals, which then are no longer rare...
Another possibility is that there may be fitness tradeoffs in the color morphs. In the common wall lizards native to Europe (Podarcis muralis), the yellow color morphs have more testosterone and have the associated traits of more aggression and more/smaller eggs than the red or white color morphs. They also have reduced immune responses that are also associated with higher testosterone (as seen in many species). These two life strategies, which I like to call "live fast and die young (yellow)" vs. "slow and steady wins the race (red and white)", are maintained in the species because different environmental years will favor different strategies. In a really great year with ideal weather and lots of food/resources, the yellow morphs can go to town reproducing a ton of offspring. In a poorer quality year, however, the red and white morphs will be more likely to have successful offspring because they will live longer and produce fewer eggs but with larger nutritional reserves in each egg so that each baby has a better chance of surviving in the harsh surroundings.
We don't know if there are fitness tradeoffs for the color morphs within Hyperolius species, but this would be a great area of future research. Overall, our understanding of Hyperolius frogs is still in its infancy (we are still naming many new species each year), but there is a lot left to learn!
RSS Feed