An evaluation of vertebrate seed dispersal syndromes in four species of black nightshade (Solanum sect. Solanum) |
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Authors: | Teri Tamboia Martin L Cipollini Douglas J Levey |
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Institution: | (1) Department of Botany, University of Florida, 32601 Gainesville, FL, USA;(2) Department of Zoology, University of Florida, 32601 Gainesville, FL, USA;(3) Present address: Department of Biology, West Virginia University, 26505 Morgantown, WV, USA;(4) Present address: Department of Biology, 430 Berry College, 30149 Mount Berry, GA, USA |
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Abstract: | We examined the ecological relevance of bird versus mammal dispersal syndromes in four species of Solanum, S. americanum Type A, S. americanum Type B, S. ptychanthum, and S. sarrachoides. These plants were selected because their morphological characteristics, such as fruit color, mass, and persistence, resembled those typically associated with classically-defined bird and mammal dispersal syndromes. We monitored persistence of tagged fruits, compared physical and chemical chaacteristics, performed fruit preference trials with northern bobwhite quail (Colinus virginianus), deer mice (Peromyscus maniculatus), and American robins (Turdus migratorius), and assessed differences in use of olfactory cues by foraging deer mice. We predicted that principal components analysis of physical and chemical characteristics would place fruits of these species along a clear gradient from bird to mammal dispersal syndromes (S. americanum Type A, S. americanum Type B, S. ptychanthum, and S. sarrachoides). However, physical and chemical characteristics did not consistently follow the gradient. Also, contrary to expectations, both birds and mammals demonstrated a preference for S. americanum Types A and B, both bird fruits. Deer mice and bobwhite quail showed much less discrimination among fruit types than did American robins. While the relatively strong odor of the green-fruited S. sarrachoides suggested a mammalian attractant, deer mice discovered the relatively odorless S. americanum Type A significantly more quickly. We conclude that in Solanum, suites of morphological characteristics resembling bird and mammal dispersal syndromes are not good predictors of fruit choice by birds and mammals. We note, however, that this conclusion is based on a sample of three animal species. Alternative explanations for fruit character suites should be considered. For example, the adaptive significance for an association of green coloration of ripe fruit with impersistence (dropping when ripe), as in S. sarrachoides and some S. ptychanthum, may relate more to photosynthesis and carbon balance in detached fruits than to disperser attraction. |
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Keywords: | Frugivory Fruit chemistry and morphology Seed dispersal syndromes vertebrate Food choice Solanum |
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