The evolution of body size in termites

Area of Science:

• Evolutionary biology
• Insect evolution
• Social evolution

Background:

• Termites, social cockroaches, were hypothesized to have undergone unidirectional body size reduction after evolving eusociality.
• This hypothesis lacked testing within a phylogenetic framework.

Purpose of the Study:

• To reconstruct termite body size evolution using a phylogenetic approach.
• To test the hypothesis of unidirectional body size reduction in termites.

Main Methods:

• Utilized head width measurements from 1638 extant and fossil termite species.
• Employed phylogenetic comparative methods to analyze body size evolution.

Main Results:

• Unidirectional body size reduction model was only supported when fossil species were excluded.
• Analyses including fossil data indicated body size diversification alongside speciation.
• The common ancestor of modern termites was estimated to be similar in size to modern species.
• Body size variability, not reduction, correlated with advanced termite social features.

Conclusions:

• Miniaturization in termites likely occurred at the evolutionary origin of the group.
• Subsequent social complexification did not drive further body size reduction.
• Termite body size evolution is characterized by diversification rather than a simple reduction trend.