Seed cleaning of Strychnos ramentifera (Loganiaceae) by ants in Maracá Island, Brazilian Amazonia.

Thousands of plant species rely on ants to disperse their seeds, including many South American epiphytes and vines, which, apart from minimizing competition among seedlings, may also reduce competition among different plant species (Handel & Beattie, 1990). The lianas of the Genus Strychnos (Loganiaceae) are recognized as having fruits with highly poisonous seeds containing strychnine in the integuments, which are, nevertheless, dispersed endozoochorously by highly-specialized frugivores (i.e., spider monkeys, Genus Ateles) (Van Roosmalen, 1985, pers. comm.), mostly under an emergent tree where they spend the night (Mendes Pontes, unpubl. data; Van Roosmalen, pers. comm). Fungus-growing ants (Myrmicinae, Attini) are known to collect various types of vegetal matter, among which is fruit pulp, in order to cultivate fungal stock inside their nests (Holldobler & Wilson, 1990), (Lewinsohn, 1980; Pedroni, 1993; Oliveira et al., 1995). Timely removal of fruit pulp from fallen seed has been shown to reduce seed mortality by decreasing fungal attack, which otherwise may be the major mortality factor in the pre-dispersal stage on the forest floor (Primack, 1995). Additionally, by removing the seed pulp of tropical fruit found on the forest floor, the attines facilitate seed germination of otherwise vertebrate-dispersed plants (Oliveira et al., 1995; Leal & Oliveira, 1998). Strychnos ramentifera Ducke (Loganiaceae) is an extremely rare Amazonian liana (Van Roosmalen, 1985), which has been recorded as endozoochorously dispersed only by Ateles belzebuth belzebuth (Cebidae) (Nunes, 1992; Mendes Pontes, unpubl. data), a nonetheless endangered primate (IUCN 2002 – VU A1c), in only one locality in Brazilian Amazonia. I report on cleaning of non-dispersed S. ramentifera seeds by attine ants, which may enhance dispersion efficiency by preventing fungal infestation and increasing germination rates.