Vertebrate Dispersal Syndromes in Some Australian and New Zealand Plant Communities, with Geographic Comparisons

Abstract

Fleshy fruits, which are apparently adapted for consumption by vertebrate seed-dispersal agents, are very common (often >70% of the species) in most tropical and subtropical rain forests, despite the taxonomic, historical, and ecological differences among regions. Fleshy fruits are moderately common in some north-temperate forests (up to 50% of the species) and some south-temperate moist forests (N.Z. 27-60%, Chile 45-70%). Less than 30 percent of the species of most Australian sclerophyll woodlands, heaths, and alpine communities have fleshy fruits. Wooded vegetation types in New Zealand average 19 to 56 percent of species with fleshy fruits. Shrublands in many regions vary greatly, and grasslands commonly have low frequencies of fleshy fruited species. Fruits suitable for consumption by volant dispersers are much more common than those suited for nonvolant dispersers in North American, Chilean, Queensland, and South African forests; in Neotropical forests fruits carried by flying vertebrates are somewhat more common than others, and in Gabon, fruits consumed by nonvolant dispersers outnumber those eaten by flying dispersal agents. The proportion of species with fleshy fruits frequently correlates with moisture availability, but correlations with other ecological factors (latitude, soil nutrients, succession) also have been reported. Fleshy fruits are about as common on trees as on smaller woody plants in wet tropical forests. Fleshy fruits are more commonly produced by shrubs, sometimes vines, than by trees or herbs in North American forests, some European forests and scrublands, and drier tropical forests. Thus, some patterns are beginning to emerge, but they represent only a starting place in our understanding of variation in the frequencies of fleshy fruited species in different floras and vegetation types. Most bird-dispersed fruits appear red or black (to human eyes); yellow or blue are occasionally common in the floras so far examined. Mammal-dispersed fruits are often brown, green, orange, or yellow. Large fleshy fruits of Queensland trees that are morphologically suited for dispersal by cassowaries and mammals are commonly red, orange/yellow, black, or green/brown and thus span the range of colors of typical bird or mammal fruits. However, in two samples of fruits in actual cassowary diets, red, black, and orange/yellow predominated. Few ecological correlates of fruit color spectra have yet emerged. MANY PLANT SPECIES produce fleshy fruits that are consumed by vertebrates, who then disperse the enclosed seeds. This mode of seed dispersal was termed endozoochory by van der Pijl (1972), and the fleshy, edible fruit pulp is generally considered to be adaptive in fostering dispersal by vertebrates. Although natural historians have been intrigued by vertebrate dispersal of seeds for many decades (e.g., Darwin 1859, Kerner 1895, Wallace 1923, Ridley 1930), only in the past decade has attention begun to focus on quantifying the (van der Pijl 1972) of traits associated with dispersal by particular kinds of animals (e.g., Janson 1983, Knight & Siegfried 1983, Gautier-Hion et al. 1985), the color spectra of fleshy fruits in various regions (op. cit., Wheelwright & Janson 1985), I Received 21 April 1987, revision accepted 4 November 1987. and habitat and geographic patterns in the commonness of vertebrate dispersal in various floras (e.g., Snow 1981, Webb & Tracey 1981, Gentry 1982, Howe & Smallwood 1982, Foster et al. 1986, Willson 1986). The purposes of this paper are to (1) survey the frequency of vertebrate dispersal syndromes in a variety of Australian and New Zealand vegetation types, (2) survey the color spectra of fleshy fruits in selected Australian and New Zealand vegetation types, and (3) compare these surveys with those of other regions for which data are