A new study, one of the most comprehensive to date, uncovers an even more amazing story. Mammals were transformed into ant eaters, myrmecophages, a mind blowing twelve times since the time of dinosaurs! Using data on diets compiled by an international team of researchers for 4,099 species of mammals. Their work shed new light on the evolutionary history of these fascinating reptiles. An amazing 220 different mammal species are known to eat ants or termites. These discoveries uncover the remarkable adaptive strategies that allow these unique species to continue thriving on this otherwise toxic diet.
The discoveries point to another remarkable detail about mammals. There are only a few dozen species that evolved highly specialized traits to help them eat thousands of ants and termites each day efficiently. Yet these myrmecophagous lineages are still relatively rare, for eight of twelve evolutionary origins are represented by a single species. Such specificity begs to be explained by the ecological and evolutionary dynamics that drive dietary adaptations among mammals.
The Rise of Ants and Termites as a Food Source
Ants and termites together make up over 15,000 species. Even more remarkably, their combined biomass exceeds that of all living wild mammals. Mammals evolved to depend on them as an important food source, while insects fed on their surface during the Cretaceous period. This momentous change first took place about 145 million years ago. Even at their peak, ants and termites made up less than 1% of the world’s insect population during this period on Earth.
The evolutionary trajectory that has produced today’s myrmecophagous mammals is congruent with the big expansion in ant and termite diversity. Beginning by the Miocene epoch, about 23 million years ago, these insects flourished. Together, they made up an astounding 35% of all duplicates insect specimens. This dramatic increase likely provided new ecological opportunities for mammalian evolution, facilitating a shift toward specialized diets that included these insects.
The researchers used a time-calibrated tree of mammalian families to infer ancestral diets. Given that their analysis found a minimum of twelve independent origins of obligate myrmecophagy on a range of mammalian lineages. This multiplicity highlights the incredible flexibility of species, as they change with the times and with shifting food sources between seasons.
Dietary Adaptations in Mammals
Surprisingly, the study found that families such as Carnivora make up roughly a fourth of all the origins of myrmecophagy. This study suggests that all myrmecophages can be linked to ancestors that were insectivores or carnivores. This evolutionary pattern illustrates how any established diet can drive subsequent adaptations.
In particular, insectivorous species evolved a myrmecophagous diet about three times as often as species with a carnivorous diet. This trend shows that physiological traits related to insectivory have allowed some mammals to more readily adapt. Consequently, these quirky mammals make a living almost exclusively on a diet of ants and termites.
One particularly striking example is the Macroscelides, the giant elephant shrew genus. Through evolution, this genus transformed from consuming ants and termites to adopting an omnivorous lifestyle during the Eocene epoch. In addition to showing the wonderful complexity of dietary evolution, this case depicts the richness of how environmental pressures can shape feeding habits across time.
Implications for Mammalian Evolution
This research paints a more detailed picture of what mammalian evolution looked like. Even more important is that it underscores the complex connections between species and their preferred food. The development of anteaters shows an amazing adaptation to change in the mammals. They have brilliantly honed their adaptations to take advantage of every resource on their respective landscapes.
The paucity of myrmecophagous lineages begs deeper questions on ecological opportunity, niche filling, and competitive exclusion between species. It’s ants and termites that are doing so great! Their importance as a food source cannot be overemphasized for the survival of these mammals that depend upon them.