I suppose evolving to eat two of the most plentiful insects on the planet it's a pretty darn safe bet evolutionarily speaking.
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One possibility is that it is exceptionally difficult to re-evolve baseline feeding features once you become heavily specialized. It could also be that betting on ants and termites tends to pay off
I'm betting a mix of both. I think myrmecophagy is an evolutionary strategy bound to appear when other niches are unavailable due to competition, and to restrict them further.
I'll use the order Pilosa for the sake of example. Consider the following two maps:
The first one shows the suborder Vermilingua (anteaters), the second one Folivora (sloths). Here are their diets and ranges:
Clade | Diet | Areas |
---|---|---|
Vermilingua (anteaters) | ant/termite eaters | jungle (Amazon), savanna (Cerrado), swamps (Pantanal) |
Folivora / genus Bradypus (three-toed sloths) | picky leaf eaters, koala/panda style | jungle (Amazon), savanna (Cerrado) |
Folivora / genus Choloepus (two-toed sloths) | omnivores | jungle (Amazon) |
I'm simplifying the ranges, mind you. Regarding Choloepus' omnivory, TL;DR they eat whatever won't outrun a sloth (eh) - berries, carrion, a few insects, even a lizard or two.
Note all three can be found in the jungle, but only the specialised eaters can be found in the savanna. I don't think this is a coincidence: the plant life in Amazon is so abundant that monkeys and birds can't call dibs on all energy sources there, but the same does not apply to Cerrado. This makes Choloepus' omnivory viable in the former, but not the later - in Cerrado you won't outcompete birds and monkeys, so the specialised diets pay off there.
But let's say some Vermilingua species developed a mutation enabling a wider diet; they can eat berries, although it's a rather small part of their diet. That mutation would likely make them worse at ant/termite-eating, and put them into direct competition with other species - it's a gambit that simply doesn't pay off.
So they're mostly "stuck" with myrmecophagy. And there's selective pressure against diversification, at least in environments where food is a primary concern (instead of predation).
I think this reasoning can be extended into other clades that are eating ants and termites, too.
Taking a moment to recognize the insanely thorough formatting on that comment. I didn't even know Lemmy comments could look that clean. Well done sir.
Thank you! Although, to be fair, 90% of that is Lemmy's markdown being really good - rich enough to feel resourceful, but not complex enough to feel overwhelming. (Also, in-comment images are a godsend.)
If interested, click on the "view source" button, and you'll see how I formatted it.
Zot.
B.C. fan or UCI alumni?