Yet over the past 66 million years, mammals across the globe have repeatedly gone down this path—not once or twice, but at least a dozen times. From anteaters and aardvarks to pangolins and aardwolves, the so-called myrmecophages (animals that feed on ants and termites) have evolved similar traits: they’ve lost most or all of their teeth, grown long sticky tongues, and learned to consume insects by the tens to hundreds of thousands each day.
A new study reveals that this extreme dietary specialization, once thought rare and mysterious, has emerged independently in mammals at least 12 times in the last 66 million years (i.e., since the Cenozoic era began). This is a striking example of convergent evolution and shows just how powerful ants and termites have been in shaping mammalian history.
“The number of distinct origins for myrmecophagy was certainly surprising, as was the discovery that their origins seem to quite neatly follow the trend of growth across ant and termite colony sizes throughout the Cenozoic,” Thomas Vida, first author of the study and a researcher at the University of Bonn, told Ars Technica.
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:
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.