SEED RESERVES IN THE CENTRAL MONTE DESERT, ARGENTINA - IMPLICATIONS FOR GRANIVORY

It has been suggested that lower rates of granivory in South American warm deserts compared to their Noah American counterparts arose from a reduction of seed reserves in the former owing to the extinction of a rgyrolagid marsupials. We measured seed reserves in two habitats of th e central Monte Desert in an attempt to detect such seed decline, but to no avail. After moderate rainfall, maximum seed standing crops reac hed 16,000 and 23,000 seeds m(-2) in shrublands and open forests, resp ectively. Under the canopy of trees and shrubs there were 19,000 and 3 7,000 seeds m(-2); whereas in exposed areas there were c. 10,000 seeds m(-2) in both habitats. Seed banks in other South American semi-arid areas showed similar values. Total grass seeds as well as those presum ably preferred by ants also seem to be similar in both continents. Hen ce, granivory in South America, as has been already reported for Austr alia, is lower than in North America in spite of the great similarity of seed bank sizes. Moreover, argyrolagids were unlikely seed-hoarding granivores, therefore some other reason than argyrolagid extinction s hould be sought to explain the lack of specialized seed-eating mammals , and the smaller overall seed consumption rates in South American des erts. (C) 1997 Academic Press Limited.