ABSTRACT
Body size is one of the most obvious characteristics of an animal and a feature that has important ecological and evolutionary implications (Peters 1983, Calder 1984, LaBarbera 1989, Hanken & Wake 1993). For example, it is commonly observed that maximum diversity occurs in the smaller size classes of taxonomic and trophic groups and in naturally occurring assemblages of animals (Brown 1981, Griffiths 1992). In addition, small species are typically more abundant than large species (Damuth 1981,
© A.D.Ansell, R.N.Gibson and Margaret Barnes, Editors
UCL Press
1991). Despite their diversity and abundance, small species are often more susceptible to predation than larger species (Stanley 1979 in Brown & Maurer 1986, Werner & Gilliam 1984), they may have more restricted prey options than larger species (Brooks & Dobson 1965, Wasserman & Mitter 1978) and may be less successful competitors (Schoener 1983, Persson 1985, Morse 1980 in Brown & Maurer 1986). A range of mechanisms has been proposed to account for the diversity and abundance of small species despite the impacts of larger predators and competitors. Foremost among these are: (a) life-history strategies that promote short generation times and high intrinsic rates of increase (May 1978, Marzluff & Dial 1991), (b) habitat associations and behaviour that reduce predation (Werner 1984) and (c) resource partitioning that allows small species to coexist with larger competitors (Schoener 1974). In addition, Hutchinson (1959) proposed that small species are more diverse because small size permits animals to become specialized to small diversified elements of the environmental mosaic.
