Costa Rica caterpillar decline spells trouble for ecosystems

Scientists have uncovered alarming declines in caterpillar diversity and their parasites across 22 years of monitoring in a protected forest in Costa Rica. Scientists studied the Lepidoptera order of moths and butterflies by collecting all externally feeding caterpillars — those found on leaves and not the inner tissue of a plant. They also collected the parasites that live off their caterpillar hosts, known as parasitoids, including wasps (order Hymenoptera) and flies (order Diptera).

Parasitoids require a host for development, eventually leading to their host’s death. Many parasites are extremely specialized, meaning they only parasitize certain host species.
The researchers’ findings suggest the loss of entire groups of dominant caterpillar genera. More than 40% of the 64 common caterpillar groups collected were found to be in decline. A direct consequence of these declines are reductions in parasitism: the researchers expect a 30% drop in parasitism over the next century. The findings raise concerns about declining ecosystem services such as biocontrol, a method of relying on parasitoids to keep agricultural pests such as herbivorous insects in check.

“This is really important because it’s interactions between species, not just high numbers of species, that are critical to keeping ecosystems healthy, stable and delivering ecosystem services,” says Manu Saunders, a research fellow and ecologist at the University of New England, who was not involved in the study.

Scientists conducted the study at La Selva, a biological research station on a 1,600-hectare (4,000-acre) patch of isolated forest on the Caribbean slope of Costa Rica’s Cordillera Central range, bordered by plantations responsible for global exports of banana, pineapple, and palm oil.

“La Selva, in many ways mirrors many lowland tropical forests: vulnerable to increases in temperature and flooding events, increased agricultural intensification, and marginalised protected areas,” says study lead author Danielle Salcido, a Ph.D. student at the University of Nevada, Reno. Even protected areas “are not immune to climate change or the land-use changes occurring immediately adjacent.”

Source: MONGABAY, 16 March 2020…