Enough is enough: The effects of symbiotic ant abundance on herbivory, growth, and reproduction in an African acacia
Understanding how cooperative interactions evolve and persist remains a central challenge in biology. Many mutualisms are thought to be maintained by ‘‘partner fidelity feedback,’’ in which each partner bases their investment on the benefits they receive. Yet, we know little about how benefits change as mutualists vary their investment, which is critical to understanding the […]
Megaherbivores and cattle alter edge effects around ecosystem hotspots in an African savanna
Wild mammalian herbivores and cattle are fundamental drivers of African savanna ecosystems and have strong impacts on woody vegetation. However, few experimental studies have investigated the separate and combined influences of different large herbivores on spatial vegetation patterning. In East Africa, temporary cattle corrals (bomas) develop after abandonment into productive, treeless ‘glades’ that attract both […]
Effects of simulated shoot and leaf herbivory on vegetative growth and plant defense in Acacia drepanolobium
Plants have considerable ability to respond to herbivory, both with (above-ground) regrowth and with increased defense. We simulated both leaf and shoot herbivory in controlled, replicated experiments on individuals of Acacia drepanolobium in Laikipia, Kenya. These experiments were carried out on individuals that had experienced different, experimentally controlled histories of large mammalian herbivory. Both forms […]
Symbiotic ants as an alternative defense against giraffe herbivory in spinescent Acacia drepanolobium
We explore here the occurrence of aggressive ants in an apparently symbiotic relationship with the savanna tree Acacia drepanolobium and their effects on giraffe herbivory on the Athi-Kapiti Plains, Kenya. Trees taller than 1.3 m were more likely to be occupied by aggressive ants in the genus Crematogaster than were shorter trees. Ants were concentrated on shoot tips, the […]
Effects of natural and simulated herbivory on spine lengths of Acacia drepanolobium in Kenya
We present experimental evidence supporting the hypothesis that increased spine length in acacia species is a defense induced by herbivory. Acacia drepanolobium is the dominant tree over large areas of East Africa. Each individual tree is occupied by one of four ant species at our study site. Using two types of electric fences, we have […]
The impact of giraffe, rhino and elephant on the habitat of a black rhino sanctuary in Kenya
The habitat in an enclosed black rhino sanctuary, the Sweetwaters Game Reserve in Kenya, is being altered as populations of elephant, giraffee and black rhino increase. Height-specific browse impact data were recorded for 1075 trees of the dominant species, the whistling thorn, Acacia drepanolobium. Rhinos and elephants browsed 18% of these trees in 1 year, […]