- Author: Kathy Keatley Garvey
Professor Karban of the Department of Entomology and Nematology, who has maintained a study site at Bodega Marine Reserve in central California since 1982, links the decrease to temperature.
“I've been surveying seaside daisies for spittlebugs at Bodega Bay every spring for the past 35 years and found that the number of these highly visible and previously widespread insects was related to temperature,” Karban said.
However, since the spring of 2006, the UC Davis researchers have found no spittle masses on the Bodega Bay Reserve's coastal prairie. Other researchers have also detailed how sensitive spittlebugs are to environmental conditions.
The meadow spittlebugs, Philaenus spumarius, thrive in cool, moist habitats and suck plant juices, feeding on xylem fluid and excreting most of it as a foamy white mass known as spittle. The mass protects them from desiccation, predation and parasitism. In past years, Karban and Huntzinger found an abundance of meadow spittlebugs feeding onseaside daisy (Erigeron glaucus) and the non-native ice plant (Carpobrotus edulus).
The Karban-Huntzinger research paper, “Decline of Meadow Spittlebugs, a Previously Abundant Insect, Along the California Coast,” is especially important in light of alarming research in Germany dubbed “Insect Armageddon.” In that research, published last October in the journal PLOS ONE, German scientists investigated aerial insect biomass across 96 protected preserves in the country. They found that three-quarters of flying insects had disappeared over the past 25 years.
The earth's climate is warming at a rate of 0.2 degrees Celsius per decade over the past 30 year, according to the National Aeronautics and Space Administration. California's coast has also experienced climate change; the recent severely hot years in the state have also been severely dry. Models of future climates predict that the warming trend will continue and that variability in conditions, for example, droughts, also will increase in frequency and severity.
“Whether the altered climates we face globally will change our ecological communities will depend on how able individual species are to adapt to the new conditions,” the UC Davis researchers explained. “Since meadow spittlebugs were widespread and abundant, we might have assumed that they would not be threatened by climate change. What we have found is that even this species has not been able to adjust physiologically or ecologically. If the pattern they show is common, we may also see surprising changes in the abundance or distribution of other insects as well. These changes are likely to have dramatic and unexpected effects on the functioning of ecosystems.”
- Author: Kathy Keatley Garvey
Now UC Davis researchers have found that some plants excrete a stickylike glue to entrap sand so predators won't eat them.
Graduate student Eric LoPresti and his major professor, ecologist Rick Karban, professor in the UC Davis Department of Entomology and Nematology, found that two plants, sand verbena Abronia latifolia and the honeyscented pincushion plant Navarretia mellita appear to deliberately make themselves unappealing with a coat of “sand armor.”
Sand entrapment on plant surfaces is called psammophory or sand armor, they said in newly published research in the journal Ecology.
Thus, herbivores like rabbits and bison, avoid eating them. “Sand and soil are nonnutritive and difficult for herbivores to process, as well as visually identical to the background,” they wrote in their abstract.
LoPresti and Karban set out to investigate whether the sand-coating serves as a camouflage or a shield from predators or both.
“We experimentally investigated whether this sand coating physically protected the plant from herbivores or increased crypsis (or the ability of an animal to avoid observation or detection),” they said. “We tested the former hypothesis by removing entrapped sand from stems, petioles, and leaves of the sand verbena Abronia latifolia and by supplementing natural sand levels in the honeyscented pincushion plant Navarretia mellita. Consistent with a physical defensive function, leaves with sand present or supplemented suffered less chewing herbivory than those with sand removed or left as is.”
They tested the “possible crypsis effect” by coating some sand verbena stems with green sand, matching the stem color, as well as others with brown sand to match the background color. “Both suffered less chewing herbivory than controls with no sand and herbivory did not significantly differ between the colors, suggesting crypsis was not the driving resistance mechanism.”
Since their paper's online publication, the work has been featured in Newsweek, Discover and on CBC Radio.