Ants and bees are surprisingly more genetically related to each other
than they are to social wasps such as yellow jackets and paper wasps, a
team of University of California, Davis, scientists has discovered. The
groundbreaking research is available online and will be
published Oct. 21 in the print version of the journal Current Biology.
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Bull ant showing the powerful mandibles and the relatively large compound eyes
that provide excellent vision [Credit: WikiCommons] |
Using state-of-the-art genome sequencing and bioinformatics, the
researchers resolved a long-standing, unanswered evolutionary question.
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, said senior author and ant specialist Phil Ward,
professor of entomology at UC Davis.
“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,” Ward said. “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.”
The collaborators included Ward, Assistant Professor Joanna Chiu,
Assistant Professor Brian Johnson, graduate student Marek Borowiec and
postdoctoral researcher Joel Atallah, all with the UC Davis Department
of Entomology and Nematology; and visiting scientist Ernest K. Lee of
the Sackler Institute for Comparative Genomics, American Museum of
Natural History.
“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,” Chiu said.
Johnson, whose lab studies the genetics, behavior, evolution and health
of honeybees, noted that the study showed that ants and bees are more
closely related than previously thought.
“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,” he said.
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 UC Davis results also 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 wrote in the
paper, “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.
