Animal dispersal of two secondary-vegetation herbs into the evergreen rain forest of south-eastern Mexico

Abstract

Rain forests at Los Tuxtlas are islands surrounded by anthropogenic vegetation containing invasive species. Epizoochory is an important dispersal syndrome among invasive species but ecological studies are scant. In order to evaluate the movement of epizoochore diaspores into the mature forest, we selected two abundant secondary herbs with contrasting diaspore morphology, and five dispersers with different pelage type. We used stuffed mammals as a dummy and passed them through patches of these two plant species, counting the number of adhered diaspores. For dispersal into the forest, diaspores were manually adhered to dispersers, these were pulled along 100-m forest transects, counting the number of diaspores remaining at distance intervals. We observed the highest amount of detachment in the first 20 m of the forest edge. For Desmodium incanum diaspores with sticky hairs, adhesion to dispersers showed no differences among pelage types, therefore dispersal is determined mainly by diaspore detachment. Dispersers with long pelage (Didelphis marsupialis, Nasua narica and Procyon lotor) move diaspores for shorter distances, while dispersers with short pelage (Silvilagus floridanus and Philander opossum) are more likely to move diaspores for longer distances. In Pavonia schiedeana more diaspores (seeds with spines and hooks) were attached and remained attached on dispersers with long and thick pelage. Mean distance travelled for P. schiedeana diaspores varied between 11 and 2700 m. In D. incanum the distance travelled did not exceed 500 m. Based on comparisons between dispersal patterns and on ecological data of these two plant species and their potential dispersers, P. schiedeana has a higher probability of invading the forest and finding suitable habitats for establishment than D. incanum.