Mechanisms affecting the fate of Prosopis flexuosa (Fabaceae, Mimosoideae)seeds during early secondary dispersal in the Monte Desert, Argentina

VILLAGRA, P.E.; MARONE, LUIS; CONY, MARIANO A

AUSTRAL ECOLOGY

Blackwell

Lugar: Carlton; Año: 2002 vol. 27 p. 416 - 421

1442-9985

The fate of seeds during secondary dispersal is largely unknown for most species in most ecosystems.This paper deals with sources of seed output of  Prosopis flexuosa  D.C. (Fabaceae, Mimosoideae) from the surfacesoil seed-bank.  Prosopis flexuosa  is the main tree species in the central Monte Desert, Argentina. In spite of occasionalhigh fruit production,  P. flexuosa  seeds are not usually found in the soil, suggesting that this species does not form apersistent soil seed-bank. The magnitude of removal by animals and germination of  P. flexuosa  seeds wasexperimentally analysed during the first stage of secondary dispersal (early autumn). The proportion of seedsremoved by granivores was assessed by offering different types of diaspores: free seeds, seeds inside intact endocarps,pod segments consisting of 2–3 seeds, and seeds from faeces of one herbivorous hystricognath rodent, the mara( Dolichotis patagonum ). The proportion of seeds lost through germination was measured for seeds inside intactendocarps, seeds inside artificially broken endocarps, and free seeds. Removal by ants and mammals is the mainfactor limiting the formation of a persistent soil seed-bank of  P. flexuosa : >90% of the offered seeds were removedwithin 24 h of exposure to granivores in three of four treatments. Seeds from the faeces of maras, on the other hand,were less vulnerable to granivory than were other types of diaspores. These results suggest that herbivory might bean indirect mechanism promoting seed longevity in the soil (and likely germination) by discouraging granivoreattack. On the other hand, germination did not seem to have an important postdispersal impact on the persistenceof  P. flexuosa  seeds in the soil. Both direct and indirect interactions between vertebrate herbivores and plants mayfoster  P. flexuosa ’s seed germination in some South American aridᕖﭸ샷퀀휁