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Leaf Change and Fruit Production in Six Neotropical Moraceae Species

Katharine Milton
Journal of Ecology
Vol. 79, No. 1 (Mar., 1991), pp. 1-26
DOI: 10.2307/2260781
Stable URL: http://www.jstor.org/stable/2260781
Page Count: 26
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Leaf Change and Fruit Production in Six Neotropical Moraceae Species
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Abstract

(1) New leaves and fruits of the Moraceae are prominent components in the diets of vertebrate primary consumers on a pantropical basis. In many cases, feeding data suggest that such items from particular genera or species are available in particular habitats for most or all of an annual cycle. (2) To investigate annual production patterns of new leaves and fruits in Moraceae, a 2-year study was carried out in Panama on individuals of six Moraceae species, Ficus insipida and F. yoponensis (subgenus Pharmacosycea), F. obtusifolia and F. costaricana (subgenus Urostigma), Cecropia insignis and Poulsenia armata, using bi-weekly inventories of materials in standardized collection plots and data from canopy scans. (3) Both Urostigma species were deciduous but flushed immediately after leaf drop; other species were evergreen. Dead leaves were shed by all species throughout both years. All species produced large crops of new leaves at intervals shorter than 1 year. Although annual leaf production occasionally showed clustering for a particular species, in general, there was considerable intraspecific variability in the timing of new leaf production. Some individuals of three species (P. armata, C. insignis and F. yoponensis) produced small quantities of new leaves more or less continuously with occasional peaks in new leaf production. Other individuals of these and other species produced large numbers of new leaves more or less episodically. (4) All species initiated fruit crops at intervals averaging < 1 year. In four species, intervals between fruit initiations averaged <26 weeks. Annual fruit production in five species was intraspecifically asynchronous and, within species, individuals tended to alter the time(s) of year of fruit initiation. C. insignis, the only dioecious species in the sample, had a single synchronized period of fruit production each year, lasting approximately 6 months. Trees of F. costaricana showed fruit in the crown for periods lasting 2, 3 or more consecutive months. Inflorescence production in two larger trees of P. armata took place more or less continuously. At the individual level, 87% of the sample trees produced fruit crops at least once per year and many produced more than one. (5) Overall, phenological activities were more pronounced in the drier half of the year. In spite of this trend, at least some leaf shed, leaf flush and fruit production took place throughout the year in most species. A bimodal trend was noted for some phenological events in some species (e.g. leaf shed and leaf flush in F. yoponensis). (6) As a family, as species and, frequently, as individuals, these Moraceae exhibited phenological traits that would tend to make their new leaves and/or fruits available to primary consumers in this forest for much or all of an annual cycle. Similar patterns of frequent and/or intraspecifically asynchronous new leaf and fruit production are predicted to be generally characteristic of Moraceae in other tropical forest areas of both the New and Old Worlds. This fruit production pattern is suggested to be an ancient trait of the family, perhaps arising in response to selective pressures related both to outcrossing advantages and improved dispersal of unusually tiny seeds. (7) The reproductive phenology of Ficus species in this study contrasted with that of C. insignis and P. armata in that individuals of the Ficus species were able to produce massive fruit crops at any time of year. This temporal flexibility with respect to the timing of fruit crops appears to relate, at least in part, to the obligate mutualism of fig trees with wasp pollinators.

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