Links between aboveground and belowground (“green” and “brown” worlds) food webs are known to occur at different trophic levels and can be stabilizing interactions. From experimental results from different climates in the U.S., fungivorous-mite prey appears to play a role in the presence and abundance of predatory mites in these two communities, one belowground, one aboveground. In a 2014 experiment with the belowground, detritus-based microarthropod community in a mesic forest in Illinois, USA, predatory mites were found to increase in abundance in association with the increase in the fungivorous mite Tarsonemus sp. (Tarsonemidae, Acari) due experimental supplementation of detritus, suggesting these may be an important prey resource.
In 2019, many specimens of Tarsonemus sp. were collected from leaves in multiple cucurbit agricultural fields in South Carolina, USA in association with cucurbit powdery mildew (Podosphaera xanthii) and a foliar predatory mite Proprioseiopsis mexicanus. Our previous experimental observations led us to ask, 1) what is the value of Tarsonemus for the survival and reproduction of P. mexicanus and 2) what is the capability of P. mexicanus to limit the population of Tarsonemus through consumption?
Two laboratory experiments were conducted using cultured Tarsonemus and P. mexicanus to answer these questions. Ten female P. mexicanus that were starved for 24 hours were each given 10 Tarsonemus every 12 hours and monitored for oviposition. Eggs laid (n = 15) were continually supplied with Tarsonemus and monitored every 12 hours for hatching and developmental changes. To investigate the ability of P. mexicanus to limit Tarsonemus populations, fifty-two female P. mexicanus were sequestered individually, starved for 24 hours, and then provided 15 Tarsonemus. Arenas were monitored at 15 minutes and one hour after Tarsonemus were introduced to P. mexicanus.
Results/Conclusions
P. mexicanus females developed in 3.2 days (SD± 0.63) on average. Females took 2.0 (± 1.1) days on average to oviposit after a male was introduced and laid an average of 1.7 (± 0.59) eggs per day. We also tested whether P. mexicanus were consuming P. xanthii, but found that juvenile P. mexicanus expired at the protonymph stage. On average, predators consumed 3.4 (SD ± 1.8) Tarsonemus in 15 minutes and 6.5 (SD ± 2.4) in one hour.
The performance of P. mexicanus on Tarsonemus prey compared favorably to high-quality non-prey resources tested previously, suggesting fungivores traveling from soils to feed on plant pathogens may be important in moving energy between aboveground and belowground food webs.