Gorongosa 2024-FULL-FINAL - Flipbook - Page 39
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GORONGOSA SP ECIAL
For every plant-eating insect,
there are often one or even two
parasitoid wasps that feed on it.
In Massad’s case, this has meant a very basic task:
matching caterpillars with their adult forms as moths
or butterflies, something that hasn’t fully been done in
many parts of Africa and other tropical areas, as well
as matching caterpillars to plants, and parasitoids to
caterpillars. Massad has found, for example, that for
every plant-eating insect, there are often one or even
two parasitoid wasps that feed on it. Her research, she
says, can “answer questions about specialization, which
is important ecologically because we know the tropics
are more species-rich than other areas of the world.”
One of the hypotheses about why the tropics are
more species-rich than other areas of the world is that
life here has become more specialized. In the tropics, a
particular kind of caterpillar will often feed on just one
kind of host plant, whereas in the temperate zone they
might feed on multiple host plants. This creates more
species over time as plants evolve to protect themselves
from herbivores, and herbivores evolve to tolerate new
plant defenses.
Massad’s ecological research offers a peek into climate change. “We studied how changes in precipitation can affect parasitism rates,” she says. “And so,
if you interrupt the parasitism, you interrupt that
top-down control, and you have more herbivory and
natural systems that might be able to be affected.”
This kind of work has previously been done by Lee
Dyer, Massad’s doctoral advisor at Tulane University,
who has studied caterpillars in Arizona, Ecuador, and
Costa Rica. Dyer is a coauthor on a 22-year caterpillar
collection study from Costa Rica that shows 40 percent
of common caterpillar groups and their parasitoids were
in decline—with effects throughout the ecosystem.
This type of research is valuable beyond Gorongosa,
Massad says. It adds to our knowledge of the diversity
of ecological interactions, which is a more informative
metric of ecosystem diversity and health than species
richness on its own. The data help us understand how
simple or networked food webs are, which indicates
how resilient to change ecosystems may be. In the long
term, these data can show how climate change affects
ecological interactions, and also provide information
on insect decline.
“Any time we can gather more data on ecological
interactions from ecosystems that haven’t been studied yet, we are gaining knowledge about the ubiquity
or particularity of patterns in nature,” Massad says.
Katharine Gammon is a freelance science writer based in Santa
Monica, California, who writes about environment, science, and
parenting. She is presently reporting from Gorongosa National
Park in Mozambique. You can find her on X (formerly known as
Twitter) @kategammon.
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