mutualism between ants and the barrel cactus
The Tucson region is home to a unique cactus: the Fishhook barrel cactus, a plant specific to the Sonoran desert region. Its unique feature is the nectar that it produces year-round at the base of its thorns, attracting several species of ants who, on their end, protect the cactus from predators (mostly stink bugs); a quid pro quo that biologists call mutualism.
Research has already been done on this duo, with results showing that cactuses protected by ants yield more fruit than their unprotected counterparts.
During my internship in biology with Dr. Judie Bronstein's team at the University of Arizona, I had the opportunity to observe this species and it's 6 legged associates. The observations took into account the diversity of species encountered, whether plants or animals, and the nature of their interractions; this in order to try to learn more about the nature of the exchanges ruling these communities.
Does the size and number of predators influence the number of ants? Do the ants encountered (up to three species shared the cactuses) follow a specific organization? Do other neighboring cactuses (Chollas, other mutualistic cactuses) influence the ants' "efforts" to protect their cactus?
Photos below:
on the left: Fishhook barrel cactuses are aptly named. The fishhook thorns obviously prevent nibblers such as deer and javelinas.
on the right: On a fishhook cactus, a Crematogaster type ant licks the base of the thorns to collect the nectar.
Naturalist observations, on the edge of strict science, gives us a chance to ask questions that experiments avoid at times, and therefore offers a wider range of consideration that can then be integrated in scientific processes. This is the approach that my hosting laboratory, dedicated to mutualism, had me do during the month and a half of field work.
It helped me understand the relationships between the many biological and environmental factors of the Sonoran desert, and to also see the dangers that climate change has created for these communities.
