Insect – plant interrelationships are amazingly complex and curious, likely the result of eons of co-evolution. Galls are abnormal growths caused by mites, fungi, and insects, the product of intimate and often species-specific associations.
Domatia are different. They are not ‘abnormal’; They are tiny ‘chambers’ produced by plants that house arthropods (insects).
Common grape vine (Vitis rotundifolia) has domatia on the undersides of leaves. This native grape vine grows from Delaware southward throughout the southeastern U.S. and is well-adpated to warm and humid conditions. Unlike grapes of exotic origin, common grape is tolerant of native insect pests and diseases.
Domatia likely are an adaptation that plays a role in this tolerance. A paper published in the Florida Entomologist found that the number of insects living in domatia on common grape increased dramatically with the onset of the spring rainy season. 47% of the tiny insects, mostly mites, were fungivorous (fungus-eating) and nearly 8% were predatory. Less than 1% were herbivorous (plant-eating).
What a magnificent, mutualistic plant – insect relationship!
Common grape vine is common throughout the Oslo Riverfront Conservation Area. When this nature preserve was purchased, vigorous ‘Tarzan” grape vines with woody trunks many inches thick were present in the hammock area, but these magnificent old vines were cut out by Indian River County Parks personnel. Common grape vine colonizes sunny, open areas as shown below by Sam (Bob Montanaro’s dog) posing in the scrubby pine flatwoods at south Oslo Riverfront Conservation Area.