The Asiatic oak weevil, an invasive beetle with the potential to alter forest composition, takes advantage of shelters built by leaf-tying caterpillars in oak trees.
Ecosystem engineers are species capable of altering the environment and creating new habitats for other species. Beavers are the most popular ecosystem engineers – their shelters create dams that extend wetland areas, facilitating the colonization of aquatic plant species and other vegetation-associated organisms. Because of their role in enhancing habitat heterogeneity and promoting local species diversity, ecosystem engineers should be important targets for promoting the conservation of species and ecosystems. However, for every rule there is an exception. Even though ecosystem engineers can be positively associated with the establishment of local diversity, now there is evidence that invasive species can also take advantage of the habitat modification promoted by these natural engineers.
In a study that just came out in the Ecology journal, Baer and Marquis use an experimental approach with artificial caterpillar shelters to investigate the effects of ecosystem engineering on the abundance and host preference of the invasive beetle Cyrtepistomus castaneus, known as the Asiatic oak weevil. Oak trees are the favorite meal of C. castaneus; the weevil larvae eat the roots and the adults consume the leaves of these tree species. Although differences in leaf quality among different species of oaks influence the host-tree preference of weevils, the presence of leaf-ties was proven to have a positive role on the abundance of this invasive beetle species. The study not only explains what factors drive C. castaneus to explore certain species of oaks, but also sheds light on the relevance of ecosystem engineers in promoting the invasion of a forest habitat by a non-native species. Invasive species often have a set of conditions in common that facilitates initial establishment in a new environment, such as flexible resource usage and high reproductive rates. It is undetermined whether ecosystem engineers have a decisive role on facilitating initial ecosystem colonization of invasive weevils, and even other invasive species. However, weevils are not the only ones that benefit from these ecosystem engineers, since it is known that caterpillars that produce leaf tie shelters also increase the diversity of native arthropods.
“ Even though people usually think about invasive species succeeding because they find new food and avoid old enemies, it may also depend on how helpful their new neighbors are” – Christina Baer