Native Seed Dispersers May Promote the Spread of the Invasive Japanese Raisin Tree (Hovenia Dulcis Thunb.) in Seasonal Deciduous Forest in Southern Brazil

Abstract

Hovenia dulcis (the Japanese raisin tree) is an invasive tree in seasonal deciduous forest in Southern Brazil. The species has an uncommon infructescence morphology, with dry fruits attached to fleshy peduncles that attract animals. This study assesses the interaction between the raisin tree and frugivore animals in seasonal deciduous forest and identifies potential dispersal relationships. Local fauna consumers and dispersers of the raisin tree were recorded by camera traps and by focal observation. Fruit removal was assessed by experiments that excluded certain animal groups while allowing access by others. We assessed seed dispersal by endozoochory by collecting the feces of birds and mammals found in the study area. The seeds found in the animal feces were then subjected to germination tests. A sampling effort of 2,305 traps/day was taken during the fructification period of the raisin tree. As a result, 28 species (16 birds and 12 mammals) were recorded from pictures taken by camera traps, and two more bird species were recorded via focal observation, for a total of 30 recorded species. Intact seeds of the raisin tree were found in the feces of Cerdocyon thous (crab-eating fox). No difference was found in seed germination between seeds obtained from fecal samples and the control. Ants can also be secondary dispersers of the raisin tree based on two observations made during the research field trips. The results obtained from this study suggest the raisin tree has different dispersal mechanisms with which different native dispersal agents are associated. Mid-size mammals, such as the crab-eating fox, are secondary dispersers by endozoochory, while birds are primary dispersers by sinzoochory.