Rafflesia arnoldii, the largest flower in the world, is a parasite that lives most of its life inside the vines it parasitizes. According to recent genomic research, an astounding percentage of the parasites’ genes have been destroyed in this group of plants.
Do vines have parasites?
At least for gall wasps, karma exists. These tiny insects leave their larvae in trees so that their young can nutrient-leech off the plants. However, it turns out that a parasitic vine also feeds off the parasitic wasps.
Similar to gall midges and gall flies, gall wasps nest inside developing oak trees to take advantage of the trees’ propensity to develop a little tumor-like formation when irritated. After that, the wasp larvae mature inside the oaks, where they create tiny embryonic sacs from which they can draw nutrients from the remainder of the tree. That is a snub. They are tiny, highly structured balls that the wasp, not the tree, controls.
The love vine, Cassytha filiformis, is another parasite that infests some oak trees. Because the love vine is an obligatory parasite, it must adhere to another plant in order to exist because it cannot do it on its own. Love vines lack substantial leaves, are unable to sustain themselves physically, and are unable to procure their own food or water. As an alternative, they embed their creepers into the internal tissues of woody trees and bushes so they can extract nutrients and water for their own use. These growths, known as haustoria, resemble root systems. Many plants may withstand a love vine without dying, but if it grows too quickly and persists for too long, the host plant may be killed.
The researchers who made this finding were initially just interested in the species of gall wasp known as Belonocnema treatae, but while doing so they discovered a number of galls with associated haustoria. As a result, they returned to the field and collected more. The galls that the vine attacked tended to be around 35% larger than usual, but the wasps within didn’t fare as well, indicating that the love vine was taking nutrients away from the larvae as they grew. Although the larger galls contained more nutrients, a higher proportion of the attacked galls—45% versus just 2% of the unattacked galls—had dead wasps inside.
In addition, the vine doesn’t appear to be acting inadvertently. Typically, love vines will sprout from stems, buds, and the tops or sides of leaves. Galls, however, are made nearly entirely on the underside of leaves by gall wasps. Since it is improbable that they would have met by chance, the discovery of vines tied to galls shows that the vine was able to locate the researchers.
When the researchers recognized what they had found, they went back to the area and paid closer attention. They found that love vines also prey on five other kinds of gall-forming wasps and flies in addition to an other, less frequent type of gall wasp.
Who knows how many additional parasite connections we’ve been blissfully unaware of if biologists who have studied galls for decades might have missed this. According to the researchers, there are 4,500 species of parasitic plants and 13,000 kinds of flora that produce galls. Both species are widespread throughout the world. There is a lot of possible overlap there. Hopefully there will be lots more parasite versus parasite combat in the future.