- 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.