Researchers have resolved a long-standing, unanswered evolutionary question and discovered that ants are more closely related to bees than they are to most wasps. (Credit: Axel Rouvin/Flickr)

Ants and bees are evolutionary ‘sisters’

Ants and bees are more closely related to each other than they are to social wasps such as yellow jackets, according to new gene sequencing analysis.

Scientists previously thought that ants and bees were more distantly related, with ants being closer to certain parasitoid wasps.

Ants, bees, and stinging wasps all belong to the aculeate (stinging) Hymenoptera clade—the insect group in which social behavior is most extensively developed.

“Despite great interest in the ecology and behavior of these insects, their evolutionary relationships have never been fully clarified. In particular, it has been uncertain how ants—the world’s most successful social insects—are related to bees and wasps,” says Phil Ward, professor of entomology at the University of California, Davis.

“We were able to resolve this question by employing next-generation sequencing technology and advances in bioinformatics. This phylogeny, or evolutionary tree, provides a new framework for understanding the evolution of nesting, feeding, and social behavior in Hymenoptera.”

“With a phylogeny or evolutionary progression that we think is reliable and robust, we can now start to understand how various morphological and/or behavioral traits evolved in these groups of insects, and even examine the genetic basis of these phenotypic changes,” says Joanna Chiu, assistant professor in the department of entomology and nematology.

Social animals

“This result should be important for future studies focused on eusocial evolution, as it suggests that morphology may not be a good indicator of evolutionary relatedness in these groups of organisms,” says Brian Johnson, assistant professor in the department of entomology and nematology.

Eusocial behavior is characterized by cooperative brood care, overlapping adult generations, and division of labor.

The scientists combined data from the transcriptome—showing which genes are active and being transcribed from DNA into RNA—and genomic (DNA) data from a number of species of ants, bees and wasps, including bradynobaenid wasps, a cuckoo wasp, a spider wasp, a scoliid wasp, a mud dauber wasp, a tiphiid wasp, a paper wasp, and a pollen wasp; a velvet ant (wasp); a dracula ant; and a sweat bee, Lasioglossum albipes.

Of particular interest was the finding that ants are a sister group to the Apoidea, a major group within Hymenoptera that includes bees and sphecid wasps (a family of wasps that includes digger wasps and mud daubers).

The findings, published in the journal Current Biology, provide a new perspective on lower Cretaceous fossil Cariridris bipetiolata, originally claimed to be the oldest fossil ant. Scientists later reinterpreted it to be a spheciform wasp.

“Our discovery that ants and apoids are sister taxa helps to explain difficulty in the placement of Cariridris,” the authors write, “and suggests that it is best treated as a lineage close to the root of the ant-apoid tree, perhaps not assignable with certainty to either branch.”

The scientists discovered that the ancestral aculeate wasp was likely an ectoparasitoid, which attacks and paralyzes a host insect and leaves its offspring nearby where they can attach to the outside of the host and feed from it.

Source: UC Davis

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