The role of ant-tended extrafloral nectaries in the protection and benefitof a Neotropical rainforest tree

One possible function of extrafloral nectaries is to attract insects, parti cularly ants, which defend plants from herbivores. We determined whether an ts visiting saplings of the tree Stryphnodendron microstachyum microstachyu m (Leguminosae) provide protection (decreased plant damage due to ant moles tation or killing of herbivores) and benefit (increased plant growth and re production associated with ant presence) to the plant, We compared ant and herbivore abundance, herbivore damage and growth of ant-visited plants and: ant-excluded plants grows in sun and shade microhabitats of a 6-ha plantat ion in Costs Rice over a 7-month period. Results show that ants provided pr otection to plants not by reducing herbivore numbers but by molesting herbi vores. Ants also reduced the incidence of pathogen attack on leaves. Protec tion was greater in the shade than in the sun, probably due to lower herbiv ore attack in the sun. Protection was also variable within sun and shade ha bitats, and this variability appeared to be related to variable ant visitat ion. Results also indicate that ant presence benefits the plant: ant-visite d plants grew significantly more in height than ant-excluded planes. The cu ltivation of ants may serve as an important natural biological control in t ropical forestry and agroforestry systems, where increased plant density ca n otherwise lead to increased herbivore attack.