دانلود رایگان مقاله شکارگری دانه و حذف از مدفوع در یک اکوسیستم خشک

Abstract

The fate of dispersed seeds from mammal faeces depends both on the animal that finds the seeds and environmental conditions. We explored the simultaneous influence of microhabitat and food availability on seed predation and removal from faeces by different animals in a protected Prosopis flexuosa open woodland site of the central Monte desert (Argentina). Using exclusion trials on simulated cattle faeces, we quantified seed predation in situ (within cages) and seed removal from faeces by rodents and ants in two different microhabitats (under shrub cover and on bare soil). This was done for two levels of availability of P. flexuosa fruits (during the fruiting season of P. flexuosa and when there are no fruits on the ground). We found that 67.9% of seeds remained in faeces, 28.9% were removed, and 3.2% were depredated in situ. Rodents removed more seeds under shrub cover than on bare soil, and during the non-fruiting period than during the fruiting period, whereas ants removed similar proportions of seeds in different microhabitats but almost exclusively during the fruiting season. This work acknowledges the complexity of dispersal processes and identifies the relative importance of some environmental factors for seed fate.

Discussion

We evaluated key interactions during one stage of the dispersal process of Prosopis, and found that the probability of a seed being removed or depredated from faeces differs between predators, which in turn are affected differentially by type of microhabitat and availability of P. flexuosa fruits. Experiments assessing all these factors acting together can help us estimate the relative importance of environmental conditions for seed removal, and may allow us to identify and understand the ecological scenarios favouring seed survival. In P. flexuosa open forest of the central Monte desert, seeds in cattle faeces are removed mainly by small rodents under shrub cover and during the non-fruiting period. In situ seed predation is very low, and the highest proportion ofseeds is depredated by rodents during the non-fruiting period. One limitation of this study based on experimental estimations is the simplification of seed-animal interactions occurring in the study system, considering only cattle as P. flexuosa disperser (they certainly are not the only dispersers), and only rodents and ants assecondary seed dispersers. Dung beetles could have a role in seed removal between the first 48 h after dung deposition (fresh dung) but, due to their low abundance in the livestock-excluded sites, their role as seed removers may be less important (M. B. Maldonado, pers. comm.).