John and I sought ecological enlightenment today among the oaks of Halpatioke Park in Stuart, Florida, the home of several oak species, from massive gnarled Live Oaks to knee-high “Dwarf Live Oaks.” In-between, Myrtle Oak, is the center of today‘s attempt to interpret little things. Around here, Myrtle Oak is a a scrub species, usually shrubby or a small tree, potentially fairly good-sized but rarely so.. Its overall range is most of Florida and the coastal regions of nearby states. This species harbors mites.
Mites are so small we can scarcely see them, even with magnifiers, which might be why mite-plant relationships are mite-y under-studied. Gardeners may think of mites as pests, which is true enough, and some cause weird growth irregularities in their botanical hosts, such as bizarrely deformed fruit on Black Olive trees. But that is not the whole truth and nothing but the truth. Suppose you’re a plant species plagued by herbivorous mites, what is the best protection?
Predatory mites of course, fight fire with fire, and it turns out that many plant species provide homes for their guardian predators, which is not to say every aspect of mite-plant symbiosis is understood. Some good mites eat fungi. Speculators have speculated that mites may benefit host plants by providing a foliar feeding of their nitrogenous waste. I dunno about that, but it is interesting that the Myrtle Oak domatia seem to fill up with organic matter.
Whether or not the little guys make enough manure to matter, plants do provide fine accommodations for “good” mites. Such “domatia” (think domicile) come in three forms: leaf pits (as in white mangroves and in buttonwoods), caves under veins (as in grapes), and furry bushes made of tangled plant hairs where leaf veins join, as in today’s oak and others. The domatia in Myrtle Oak are conspicuous beneath the leaf.
If you flip over a Myrtle Oak leaf and spy with a hand lens (very) patiently you can spot tiny mites on the prowl, sometimes flushed from a domatium like a bunny from a bush.
CLICK HERE for a quick glimpse of a Myrtle Oak mite on the move.
Those who study mites have found that even “bad” mites have domatia too. Maybe they merely stole them, but other observers have a more interesting explanation…that to sustain good predatory mites the plant has to offer edible “bad” mites to pay the guardians in red meat. The plant may adaptively tolerate and even shelter prey for the hunters.