Herbivory of eight common species at El Verde from 1994 to 1996



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In seasonal and aseasonal tropical forests, leaf production is often highly synchronous, concentrating herbivore resources in only a few months. As a result levels of herbivory on young leaves can vary throughout the year. To determine the importance of food availability on herbivory, leaf phenology and leaf damage were studied in an aseasonal forest, Luquillo Experimental Forest (LEF) in Puerto Rico. Leaf production was associated with an increase in light availability but leaf damage was relatively constant throughout the year. Leaf phenology and leaf damage was compared between LEF and a seasonal forest, Barro Colorado Island (BCI) Panamá. In BCI leaf production was associated with increases in water availability and leaf damage was significantly higher on leaves produced after the peak in leaf production. Leaf damage was significantly lower in LEF in comparison with BCI. Differences in the trophic structure between the two forests may explain the differences in levels of leaf damage. The density of frogs and lizards in LEF was approximately an order of magnitude greater than in BCI and these predators may limit the populations of herbivores and reduce leaf damage levels.

Date Range: 
1994-11-01 00:00:00 to 1996-09-01 00:00:00

Publication Date: 

2011-06-07 00:00:00

Additional Project roles: 

Name: Miguel C Leon Role: Data Manager
Name: Mitchell Aide Role: Associated Researcher


Leaf phenology and leaf damage were measured on plants (1-2 m in height) in the understory. Plants were located in plots along La Prieta, upper Sonadora and Ox cart trails. Two shrubs, Palicourea riparia (Rubiaceae) and Piper glabrecens (Piperaceae) and six tree species, Casearia arborea (Flacourtiaceae), Dacryodes excelsa (Burseraceae), Guarea guidonia (Meliaceae), Manilkara bidentata (Sapotaceae), Sloanea berteriana (Elaeocarpaceae) and Tabebuia heterophylla (Bignoneaceae) were studied. These species were chosen because they are among the most common species in at this site (Zimmerman et al. 1994). There have been few studies on the herbivore community of LEF, but Schowalter (1994) collected the major invertebrates associated with five common tree species and found that Lepidoptera, Coleoptera and Homoptera (cicadellids principally) were the most abundant herbivores, that are the principal herbivores in different type of forest (Duckett, pers. comm.).  In addition different species of walking sticks (Phasmida) are also important herbivores in LEF (Garrison & Willig 1996).

LEAF PHENOLOGY AND LEAF DAMAGE CENSUSES. --The study was conducted from November 1994 to October 1995 (year one) and from November 1995 to October 1996 (year two). Twenty individuals of each species were marked. All individuals were located in the understory. Each month, all new, full expanded leaves were counted and a maximum of ten leaves per plant was marked with plastic telephone wire. One month later, leaf area and area damaged were measured for all marked leaves using a plastic grid. Although this method may overestimate consumption by herbivores and underestimate the effect on leaf area (Coleman & Leonard 1995), there are few alternatives for determining multispecies patterns of leaf damage in tropical forest. In addition, the leaf production and leaf damage data were compared with data from BCI (Aide 1993) which were obtained using the same methodology.

ANALYSIS. --Leaves produced within a month by a single individual were considered independent events (leaf cohorts). For each individual, the monthly proportion of annual leaf production was calculated. For estimating the annual pattern of leaf production for the species, average leaf production of the twenty individuals was calculated for every month. Patterns of monthly leaf production for the eight species was calculated by averaging the means of each species. Patterns of leaf phenology were compared between years using a Kolmogorov-Smirnov test (Ott 1993). Cross correlations were performed to determine if rainfall, light intensity or day length were important cues for leaf production (Statistix 1996). A maximum lag time of two months was used for this analysis.

Monthly percent leaf damage was calculated for each leaf cohort. Total damaged area on the marked leaves was divided by the total potential leaf area. If a leaf was missing, the average size of the remaining leaves were calculated and the area was added to the total damaged area and to the total potential leaf area. All species showed a peak in leaf production during May - June and percent leaf damage was compared between the cohorts produced during the month of peak leaf production and the cohorts produced during the remaining months. The same comparison was made by combining data from all species. Percent leaf damage was compared between years using the Mann-Whitney U test.

Patterns of leaf production and leaf damage were compared between LEF and data obtained from BCI (32 species; 21 families) in 1987 (Aide 1993). Leaf phenology was compared using the Kolmogorov-Smirnov test. The Mann-Whitney U test was used for comparing leaf damage. Because all LEF species had synchronous leaf production, a second comparison of leaf damage was made only with the synchronous species from BCI (10 spp.).



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