The Eurasian badger-generated seed rain drives the natural (re)colonization of vacant human-altered areas by a keystone pioneer palm

Abstract

Seed dispersal is an essential ecological process for plant (re)colonization, especially in intensively human-altered habitats such as old-fields (i.e. abandoned farmlands) where seed arrival is often limited. Assessment of spatial patterns of mammal-generated seed rain and their matching with the spatial distribution of adult plants provides essential information on the patterns and pace of the (re)colonization processes. For instance, increased seedling survival far from adult plants could indicate density-dependent mortality (Janzen-Connell) effects whereas increased survival close to adult plants could suggest facilitative effects. Here, we characterized during two dispersal seasons the spatial distribution of feces from four frugivorous mammals and quantified its spatial association with the distribution of adult plants of the pioneer Mediterranean dwarf palm (Chamaerops humilis) in two old-fields in southwestern Spain. We also estimated the dispersal kernels of both emerged and surviving seedlings and assessed potential evidence for Janzen-Connell and/or facilitative effects. Using a spatially explicit approach, we revealed strong differences between study sites in the strength and scale of spatial associations between mammal feces with C. humilis seeds and adult dwarf palms, being strongly positive at small scales in one site and slightly positive at larger scales in the other one. Further, we found some evidence of both Janzen-Connell and facilitative effects depending on the study site. Altogether, our results emphasize the central role as seed disperser of the Eurasian badger (Meles meles) in the natural (re)colonization of Mediterranean old-fields and the spatial variations of the underlying mechanisms and demographic consequences for plant populations.