Feeding by seed bugs and weevils enhances germination of wild Gossypium species.

Seeds of Gossypium sturtianum and G. thurberi do not readily germinate under most conditions. Increased germination of G. sturtianum was associated in nature with the presence of a seed bug, Oxycarenus luctuosus. Experimental and descriptive studies were conducted in Australia and Arizona to test the hypothesis that more seeds of G. sturtianum and G. thurberi germinated during their first wet season from bolls that had been attacked by insects than from unattacked bools. In Australia, seeds from G. sturtianum bolls that had been caged with O. luctuosus were more likely to germinate than those caged without bugs. In Arizona USA, seeds of G. thurberi were attacked by boll weevils, Anthonomus grandis, and seed bugs, Sphyrocoris punctellus. Weevils destroyed 21%, scarified another 26%, and left undamaged the remaining 53% of the seeds in attacked bolls. Seeds of G. thurberi from bolls with weevils and seed bugs that were not destroyed by these insects were more likely to germinate during their first wet season than seeds from unattacked bolls. All three insects probably increase germination by breaking the impermeable seed coat. The ecological and evolutionary consequences of this interaction are not known.