Geography And Fruit

Over 1500 km long, Madagascar supports as rich and varied a flora as can be found anywhere in the tropics (Reitsma, 1988; Gentry, 1993; Lowry et al., 1997; Schatz, 2002), including rainforest, dry subtropical forest, and spiny desert. Many animal taxa are absent from Madagascar because of biogeographical history and ungulates, monkeys, many birds, and many bat taxa simply never reached the island. What effect does this absence have on the ecology of the rainforest? In most rainforests the primary pollinators and seed dispersers are insects, birds, and bats (Fleming et al., 1987; Bawa et al., 1990). Terborgh (1986) estimated that as much as 80% of Amazonia's mammalian biomass depends on fruit resources. In contrast, in Madagascar 8% of the birds are frugivores (Fleming et al., 1987). Bats are also relatively depauperate in diversity with 28 species, and almost all are insectivorous (Peterson, 1995). Lemurs may be the primary pollinators and seed dispersers in the rainforests of Madagascar (Kress et al., 1992; Overdorff, 1992; Nilsson et al., 1993; Wright and Martin, 1995; Balko, 1998; Ratsimbazafy, 2002; Wright et al., 2005a). Black-and-white ruffed lemurs, red-bellied lemurs, and brown lemurs, medium-sized (2-4 kg) diurnal primates, pass vine and tree seeds intact, and these sprout faster and with less mortality than seeds not passed through a primate gut (Dew and Wright, 1998). Indeed, in the Malagasy ecosystem it is actually possible to single out one animal group, lemurs, which have the greatest biomass of frugivores and may qualify as "keystone mutualists" (Gilbert, 1980).

Although in other tropical rainforests, such as Kibale Forest, Africa (Struhsaker, 1997; Chapman, 2005), Colombia, South America (Stevenson, 2005), and Barro Colorado Island, Central America (Milton, 2005), long-term phenology data show that fruit production varies greatly for individual trees, there are fruits available throughout those forests all year. And in rainforests such as Manu Park in the Peruvian Amazon, keystone resources such as figs (large-crowned) or nectar (abundant patches) provide food for frugivores during extended periods of fruit scarcity (Terborgh, 1983; Wright, 1989). Madagascar rainforests, unlike other forests with 12-14 species of sympatric primates (Table 1; see Figure 1 and 2), have a much longer period without fruits, up to 6 months a year (Wright, 1999). And Madagascar has fewer fig species, a staple during months with scarce fruiting in other rainforests (Goodman and Ganzhorn, 1997). These long periods without fruits are reflected in the fact that few lemurs are obligate frugivores (Fleming et al., 1987; Goodman and Ganzhorn, 1997; Balko and Underwood, 2005) but nonetheless, fruits, seeds, and flowers compose 40-90% of the annual diet of Eulemur, Varecia, Eulemur ssp., Propithecus, Microcebus, Cheirogaleus, and perhaps Mirza and Phaner (Overdorff, 1991, 1993; Wright and Martin, 1995; Ganzhorn and Kappeler, 1996; Hemingway, 1996, 1998; Balko, 1998; Atsalis, 1999; Ganzhorn et al.,

Table 1. Lemur species in the rainforest site of Ranomafana National Park"

Species Body mass (g) Biomass (kg/km2)

Table 1. Lemur species in the rainforest site of Ranomafana National Park"

Species Body mass (g) Biomass (kg/km2)

Avahi laniger, woolly lemur

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