THE VULNERABILITY OF POLLEN AND FUNGAL SPORES TO ANT SECRETIONS: EVIDENCE AND SOME EVOLUTIONARY IMPLICATIONS

Afin d'interpreter le role inhibiteur des glandes metapleurales sur la germination and the viabilite du pollen, une serie d'experiences est realisee avec les secretions de Myrmecia nigrista and les pollens de Brassica and Acacia.

Abstract

The quality of Brassica and Acacia pollen is adversely affected by exposure to secretions drawn from the metapleural gland of the ant Myrmecia nigriscapa . Ultrastructural studies show that the apparently lipoidal secretions destroy both the plasma membranes and those of the cytoplasmic organelles. Exposure to the integument of this ant prevents the normal hydration of pollen grains. Exposure to the integument of a species of Camponotus , which does not appear to possess metapleural gland openings, also reduces pollen quality. Mycelial development in seven species of soil‐dwelling fungi is inhibited by secretions of the metapleural gland. Two fungal species that are normally entomogenous are most vulnerable to the secretion. It is suggested that the metapleural gland is producing a powerful antibiotic and that the antibiosis that results from its activity, on one hand, alleviates the attacks of microorganisms in nest cavities, while on the other, incidentally kills pollen grains, possibly blocking the evolution of ant pollination systems.