PS 4-39
Seeds harvesting by P. barbatus in habitats transformed by human activities
Seeds included in the diet of harvester ants have been broadly studied in deserts of North and South America, however very few is known for inter-tropical deserts such as the Tehuacán-Cuicatlán valley, a semiarid zone in central Mexico. At this place local people carried out a high diversity of activities such as agriculture, grazing, firewood and fruit collection, having as consequence the transformation of habitats. In this study the main question was: How transformation of habitat is affecting the seed composition of the diet of the harvester ant Pogonomyrmex barbatus? Seeds in the diet of P. barbatus were studied analyzing the discarded material accumulated in middens of fifteen nests, five in each of three habitats which have been under the effect of human activities: An abandoned field crop, an open shrubland with evidence of human activities, and a closed shrubland with low evidence of human activities. We hypothesized that habitats under intense human activities would have few abundance and diversity of seeds because they offer few resources for harvester ants and their harsh conditions reduce their foraging activity.
Results/Conclusions
Abundance and diversity of seeds found at nest middens was statistically different among the tree types of habitat studied. Nest middens analyzed from habitats with intense human activities (MA and CC) had high abundance of seeds and species richness than those from the most preserved habitat (MC). Seeds of Asteraceae and Poaceae were the most abundant and common at the nest middens independently of the habitat analyzed. Seed of Flaveria sp., Poaceae sp. 3 and Arstida sp. were the most abundant species found at middens and, on the contrary to our expectations, they were always more abundant at the abandoned field crop. Our results suggest the high abundance and diversity found at abandoned field crop and open shrubland are related to the presence of annual plants such as grasses and asteraceae which can produce high quantities of seeds which are used by P. barbatus. We also suggest the effect of the intermediate disturbance which can increase the availability of resources available for ants in habitats such as the open shrubland.