Isolated peaks teem with unique insect communities

For a study of parasitic wasp communities on the mountains of the interior highlands of Arkansas, one of the sites chosen was Mount Magazine State Park in Arkansas, which rises 709 meters (2,326 feet) above sea level. With cooler and wetter climates than the nearby lowlands, each of these communities exhibits its own communities of parasitic wasps – and likely other insects – that differ from the fauna of insects found on other mountains and in the surrounding valleys, according to a new study published in August in Environmental entomology. (Photo courtesy of Allison Monroe)

By Ed Ricciuti

Ed Ricciuti

Ed Ricciuti

It’s not quite Sir Arthur Conan-Doyle’s lost world dinosaurs, but the insect life found by scientists atop the so-called “sky islands” in Arkansas is truly unique.

“Sky island” is a term popularized in the 1960s to describe isolated mountains with distinctly different environments than the surrounding lowlands. Conan-Doyle foreshadowed such environments in his account of an expedition that explored a plateau rising above the jungle, where prehistoric dinosaurs, reptiles, and “ape men” had passed through the ages.

Although not as dramatic as the dinosaurs, isolated endemic populations of animals of all sizes excite scientists. According to a study published in August in Environmental entomologysuch distinct assemblages of insects of the order Hymenoptera (sawflies, bees, wasps, and ants) live atop the highlands of Oklahoma, Arkansas, Missouri, and Illinois called the highlands interior lands.

The study, conducted by student researchers at Hendrix College in Conway, Arkansas, focused on parasitic wasps inhabiting three mountains, but the results can be extrapolated to other sky islands in the region and their insects in general. , according to the researchers.

“Since each sky island in our study exhibited unique community characteristics of Hymenoptera, it is reasonable to predict that other insects would follow the same pattern,” the authors write. The mountains studied were Petit Jean Mountain at 253 meters (830 ft), Mount Magazine at 709 meters (2,326 ft), and Rich Mountain at 747 meters (2,451 ft).

Parasitic Hymenoptera are an innumerable group, with around 50,000 species identified and possibly millions in all. Typically, they parasitize other insects by laying their eggs in host eggs, larvae, or pupae. They are of immense ecological importance as they are adapted to specific hosts, including many species of pests, which they can regulate, like natural pest control managers. “We chose parasitic Hymenoptera as the focal group because they are considered bioindicators of broader diversity patterns, especially those of other insects,” the authors write.

The interior highlands, centered on Missouri and Arkansas and including the Ouachita Mountains and the Ozark Plateau, were chosen as the study site because they have been above sea level for 320 million years ago, probably serving as a refuge for ecological communities avoiding the impact of the Pleistocene. glaciers. The region is the only major mountainous area between the Appalachians and the Rockies, covering far more area than the Black Hills of South Dakota. Typical of the interior highlands, Mount Magazine is 10 degrees Fahrenheit cooler than normal temperatures in the lower, humid landscape, with an annual rainfall of 54 inches. Crowned by upland hardwood forests and upland pine and hardwood forests, these mountains rise from grasslands, with vegetation ranging from tallgrass prairie to lowland pine hardwood forests and lowland hardwoods.

Much of the area where the research was conducted is on state and federal land. Sweating in the hot summer sun, the search party hiked hiking trails from the prairies to the woods. They set up traps, then collected insects there.

“Although evidence is mounting that the interior highlands are home to unique species compared to other areas of the North American continent, less is known about how the region’s mountain peaks compare in terms of biodiversity,” write the researchers. “We used parasitic wasps to explore biodiversity patterns in high-altitude areas of Arkansas to determine if these patterns are similar to those exhibited by other sky island regions.”

Each vertex had its distinct community of parasitoid species, indicating that the same is true for Hymenoptera in general and even for other insect groups. On a given mountain peak, the communities differed stratigraphically, with those on the ground being distinct from those in the forest canopy.

The results of the study suggest the need for further research. “Our study suggests that these mountainous areas are important regions of North American biodiversity and should be individually assessed for conservation efforts to preserve their distinctive community structure,” the authors write.

Elaborating on the study, lead author Allison Monroe, says, “This study is important for a variety of reasons. Parasitic wasps are deeply important to our environment but are often overlooked if not deeply hated.

Monroe, now a Ph.D. candidate for Oregon State University College of Forestry, says, “Arkansas is an incredibly biodiverse state with high rates of agricultural production, but there is little research on insect biodiversity trends and their applied impacts. on various land management strategies within this system. We hope this article sheds light on the extraordinary diversity of Arkansas, the importance of wider insect biodiversity, and the importance of pests in our nature conservation efforts.

Ed Ricciuti is a journalist, author and naturalist who has been writing for over half a century. His latest book is called Bears in the Backyard: Big Animals, Sprawling Suburbs, and the New Urban Jungle (Countryman Press, June 2014). His missions have taken him around the world. He specializes in nature, science, conservation issues and law enforcement. A former curator at the New York Zoological Society, and now the Wildlife Conservation Society, he may be the only man ever bitten by a coatimundi on Manhattan’s 57th Street.