Emerging Entomology Research from a New Biodiversity Hotspot
When most of us conjure up images of biodiversity, the southeastern United States rarely (if ever) comes to mind. People more often associate this region with vast agricultural lands filled with cotton and tobacco. However, like any good entomologist can tell you, amazing things can be found in unlikely places, and at the Southeastern Branch meeting of the Entomological Society of America last week researchers gathered to share their stories of the world’s newly named biodiversity hotspot, as well as vital information on protecting the agriculture within it.
From taxonomy to ecology to microbiomics, entomologists covered an array of topics. Here are some highlights:
- Tiny creatures matter—and we keep finding more of them. At this year’s biodiversity symposium, researchers shared new species descriptions, state records, and collecting methods. Brittany Owens from the Louisiana State Arthropod Museum didn’t have to go far to find her new beasts—the insect collection where she works, housing tens of thousands of the group of beetles she studies, was full of undescribed specimens. Her group, the pselaphine rove beetles, are tiny (only a few millimeters long), but are considered by some as “tigers of the leaf litter” for their predatory behavior. Through her work Owens has described numerous new species, which often involves dissecting out their microscopic genitalia to elucidate differences. The fact that so many new species were already collected but awaiting description goes to show that both a lack of taxonomists and threats to our biodiversity collections (further weakened by NSF halting this type of funding this past week) impede our knowledge of the true diversity of this region. Tommy McElrath of University of Georgia, not to be outdone, also discussed his work on little brown beetles (family Monotomidae) in Georgia, and revealed that we have been underestimating their diversity by almost half in that state. These beetles are important decomposers, predators of wood-boring beetles, and even serve as pollinators.
- Sometimes a sweet tooth is not so sweet. One of the biggest subjects of the meeting was the sugarcane aphid (Melanaphis sacchari). Although the name implies a sweet little insect restricted to sugarcane, it has recently infested another host, sorghum (Sorghum bicolor), which is grown more broadly across the region for seed and syrup. Although only sporadically found in the Southeast since about 1999 (specifically Louisiana and Florida on sugarcane), in 2013 populations in southwestern Louisiana were found on sorghum. Whether this was a shift by existing aphids from sugarcane or newly introduced populations with a broader palate is unknown. What we do know is that the aphid has spread very rapidly. For example, it was first detected in North Carolina in 2015 and by the end of the year was present in at least 40 counties across the state. Farmers are seeking help from entomologists on how to best manage the pest; luckily, researchers in the region have been assessing new potential hosts, surveying resistant varieties of sorghum, testing various chemicals, and advising on best practices for protecting this crop.
- We aren’t the only ones looking for a cure to bee decline. Bumblebees (Bombus sp.) not only get sick, but may also try to self medicate, says Rebecca Irwin at North Carolina State University. Where might a bee find a pharmacy their size? Luckily they are surrounded by nature’s drugstores: plants. It turns out that the secondary compounds developed by plants for protection also show up in nectar. Irwin wanted to know if sick bumblebees sought out spiked nectar and whether the ingredients helped them with their illness (in her studies, a protozoan parasite). She found that infected bees did prefer nectars with defensive compounds, but when nectar containing the most preferred compound (thymol) was fed to sick bees, their longevity was not increased compared to those that were not medicated. It is not clear whether these results were due to the experimental method (monitoring the short-term rather than long-term longevity of the bees), but one take-home message was to offer bees a larger diversity of flowers, not just in color and shape, but also in medicinal compound composition.
- For cockroaches, poop is an invitation to the party. German cockroaches (Blattella germanica) defecate—a lot. They also prefer living in large groups, one of the reasons you usually don’t see just one (and if you do you’re likely to find more). So, how do these pests locate their friends and potential mates? Ayako Wada-Katsumata at North Carolina State University may have the most likely answer: They send chemical messages in their frass (a polite term entomologists use for fecal pellets). She showed that various bacteria in the excrement of cockroaches produce volatile chemicals that other cockroaches home in on. When cockroaches are “cured” of these bacteria, their frass is significantly less attractive. Furthermore, when these sterile cockroaches are once again provided with the bacteria, their frass becomes more attractive. The practical applications of this research are immense, including developing better baits using bacterial attractants that could make controlling these pests more efficient.
- Parasitoids beware: Some hosts are deadly. Parasitoids are an important group of insects that, unlike most parasites, kill their host. Many are used as biological control agents of other insects to reduce pest numbers. As Laura Kraft—a graduate student at University of Georgia—showed, sometimes microorganisms in the host can have large effects on their parasitoids. In her system, aphids (specifically pea aphids, Acyrthosiphon pisum) containing the bacterium Hamiltonella defensa were able to fight off the internal larvae of the exotic parasitoid wasp Aphidius ervi. However, a native parasitoid wasp, Praon pequodorum, is able to resist the effects of these microorganisms. Through caged experiments, she was able to show that after several generations, the susceptible Aphidius populations plummeted while those of the resistant Praon increased. Whether this change in population occurs out in the field is unknown, but the need to understand all of the players in these systems is apparent.
- When native and exotic plants mix, it’s bad news for the native. Many homes in the region have yards containing both native plants and ones brought in from other areas of the world. The effect of this type of heterogeneous landscape on plant herbivores is not fully understood—do pestiferous herbivores feed on plants more or less readily when non-natives are close by? Graduate student Carl Clem of Auburn University set out to answer this question experimentally by planting native red maples (Acer rubrum) surrounded by other red maples or distantly related crape myrtles (Lagerstroemia sp.). He found that caterpillar abundance was significantly greater on the red maples surrounded by crape myrtles than surrounded by other red maples. The mechanisms are not completely known, but it is likely that in the absence of native hosts (caterpillars are not adapted to the exotic hosts), they overwhelm the few suitable hosts in the area.
This post is published in Macroscope