Background:

Plant-plant facilitation provides benefits to the protected species since the host species reduces the intensity of stressful physical conditions. However, it has been hypothesized that the outcome of the interaction could be regulated by the characteristics of the interacting species and that herbivores could counteract the benefits of protective plants.

Question:

Can cactus size and identity of neighboring plants influence the herbivory of the columnar cactus P. leucocephalus?

Studied species / Mathematical model:

Pilosocereus leucocephalus (Poselg.) Byles & G.D. Rowley /One-way ANOVA, Repeated measures ANOVA, Analysis of covariance and linear regression.

Study site and dates:

San Ignacio, Veracruz, Mexico. April to May 2019.

Methods:

We randomly selected 60 P. leucocephalus plants growing underneath the canopy of seven species of shrubs and P. leucocephalus plants growing ≥ 3 m away from other species and exposed to full sunlight conditions. We obtained the size of the P. leucocephalus plants (size of main stem from ground to apex) and determined the intensity (number of bites on the stem) of vertebrate herbivory.

Results:

The number of bite scars by small vertebrate species was significantly higher on the stems of cacti established in open spaces than on those underneath the canopy of seven shrub species and increased significantly with the stem size of the protected species.

Conclusions:

We conclude that herbivory damage by rodents on a giant cactus in a dry tropical forest depends on cactus size and the identity, but not the shade, of the nearest neighbor.