New Cretaceous fossils shed light on the early evolution of ants
Ants comprise one lineage of the triumvirate of eusocial insects and experienced their early diversification within the Cretaceous. The success of ants is generally attributed to their remarkable social behavior. Recent studies suggest that the early branching lineages of extant ants formed small colonies of either subterranean or epigeic, solitary specialist predators.
|This is a general dorsal view of holotype of new late Cretaceous worker ants Ceratomyrmex ellenbergeri |
[Credit: WANG Bo]
Remarkable exceptions to this pattern of generalized morphologies are ants with bizarre mouthparts in which both female castes have modified heads and bladelike mandibles that uniquely move in a horizontal rather than vertical plane. Haidomyrmecines have puzzled evolutionary biologists as to their specific ecology, with the mandibles apparently acting as traps triggered by sensory hairs in a way distinct from that of modern trap-jaw ants.
Not all ants cooperate in social hunting, however, and some of the most effective predatory ants are solitary hunters with powerful trap jaws. Models of early ant evolution predict that the first ants were solitary specialist predators, but discoveries of Cretaceous fossils suggest group recruitment and socially advanced behavior among stem-group ants.
|This is a life-like reconstruction of Ceratomyrmex ellenbergeri |
[Credit: YANG Dinghua]
Together with other Cretaceous haidomyrmecine ants, the new fossil suggests that at least some of the earliest Formicidae were solitary specialist predators. In addition, it demonstrates that soon after the advent of ant societies in the Early Cretaceous, at least one lineage, the Haidomyrmecini, became adept at prey capture, independently arriving at morphological specializations that would be lost for millions of years after their disappearance near the close of the Mesozoic. The exaggerated condition in the new fossil reveals a proficiency for carriage of large-bodied prey to the exclusion of smaller, presumably easier-to-subdue prey, and highlights a more complex and diversified suite of ecological traits for the earliest ants.
The study has been published online in Current Biology.
Source: Chinese Academy of Sciences Headquarters [May 30, 2016]