Recruitment Dynamics of Vachellia cornigera and Its Ant Occupants in Restored Tropical Forest
thesisposted on 27.07.2018, 00:00 by Anika Hazra
Community-level interactions, such as the mutualistic relationship between Vachellia cornigera and Pseudomyrmex ferrugineus, can be used as an indicator of habitat conditions. This system was studied in experimentally restored tropical forest plots in Los Tuxtlas, Mexico to determine the influence of restored habitat conditions on a well-known ant-plant relationship. The influence of habitat conditions, including restoration treatment, location within forest plot and forest canopy cover, on the recruitment of V. cornigera was determined. The influence of restoration treatment, location within forest plot and V. cornigera height on the ant occupancy of each V. cornigera individual was determined as well. The three occupancy states were: unoccupied, occupied by Pseudomyrmex ferrugineus, occupied by Pseudomyrmex gracilis (an exploitative ant species). A total of 131 V. cornigera individuals were recorded in the sampled restored forest subplots. Subplots that were restored by planting seedlings of animal-dispersed tree species hosted the greatest number of V. cornigera individuals. The edge of subplots had significantly more V. cornigera individuals than the interior of the subplots or the area just outside the edge. Canopy cover density, as measured using a Normalized Difference Vegetation Index, did not affect V. cornigera recruitment. Forty-one V. cornigera individuals were not occupied by ants, 27 were occupied by P. ferrugineus and 59 were occupied by P. gracilis. Restoration treatment did not influence ant occupancy, but both V. cornigera location and height did. The greatest proportions of ant-occupied V. cornigera individuals (69% for P. gracilis and 63% for P. ferrugineus) were found at the edge of subplots. The tallest individuals (64-500+ cm) were occupied by P. ferrugineus, the intermediate-sized individuals (18-500+ cm) were occupied by P. gracilis and the smallest (23-107 cm) were not occupied by ants. There appears to be positive edge effects in the study site; the greatest abundance of V. cornigera individuals grow at the edge and both ant species prefer to occupy individuals growing at the edge. Restoring forest with adequate edge habitat promotes the establishment of the mutualistic relationship between V. cornigera and P. ferrugineus.