Three census methods for studying fruiting phenology and fruit production were compared: platform observation, fruit-trap collection and raked-ground survey. The estimation of fresh fruit mass varied greatly with the census method used. Moreover, the fruiting phenology recorded using the fruit-trap collection and raked-ground survey methods showed a delay of one to two months compared with the platform observation method. Any of the three methods can be used for the approximation of annual fruiting phenology, but that of fruit-trap collection is suited to measure the annual fruit production, and that of platform observation offers the best estimation of the quantity of fruit in tree crowns at a given time.

The relationship between Camponotus sp. ants and the carnivorous pitcher plant, Nepenthes bicalcarata, from Borneo were investigated. The ants nest in the hollow tendrils of the plant, and feed on large prey items caught by the pitchers. These are hauled from the pitcher fluid by the ants and consumed. When large prey items are absent, the ants feed upon mosquito larvae which inhabit the pitcher fluid. The accumulation of excess prey in pitchers can lead to putrefaction of the contents, and disruption of the pitcher's digestive system. Experiments on the possible benefits of the ants' behaviour to the plant showed that the accumulation of excess prey and the putrefaction of the pitcher contents were significantly reduced in the presence of the ants. The accumulation of ammonia in pitchers was unaffected by the presence of the ants when small prey were added to pitchers, but was reduced significantly in the presence of ants when large prey were added. It is suggested that Camponotus sp. and N. bicalcarata have a mutualistic association, from which the ants obtain food and nesting sites and, in return, prevent damaging accumulation of excess prey in the pitchers.

We compared reproductive characteristics of the dendrobatid frog Colostethus trinitatis at the Tamana cave in the Central Range hills and at five forest stream sites in the Northern Range hills of Trinidad. There were significant differences between sites in adult female body size, intraovarian clutch size (in absolute terms and relative to body size) and the size of tadpoles carried by male frogs. Clutch sizes ranged from 6 to 13 in the Northern Range samples and from 12 to 26 at Tamana. Adult male body size was similar at all sites. Tadpoles carried by male C. trinitatis at Tamana were significantly smaller (mean length 14.2 mm) than those carried by males at the five Northern range sites (mean length 16.4–16.7 mm). The smallest clutches and largest tadpoles were found at Mount St Benedict, where there was evidence of size-selective predation on tadpoles by fish. Tamana, where clutches were large and tadpoles small, differed from the Northern Range sites in terms of the physical environment (cave vs forest) and the abundance of invertebrates. We discuss possible ultimate and proximate causes of the differences in clutch size and tadpole size, particularly size-selective predation and availability of food.

Vertebrate attack accounted for 98.4% of all seed loss during the two months following dispersal. This accounted for, across all habitat types, 94% of Bursera, 76% of Spondias, 37% of Swietenia and 25% of Erythrina seeds artificially dispersed. Bursera, Spondias and Swietenia seeds in early successional habitat suffered significantly greater predation than in either older abandoned (30 y) or mature forest plots. Erythrina showed generally low loss to predation in all plots. Seeds attacked were more often removed from, rather than buried or eaten at, the dispersal site. In young secondary habitats, however, seeds of Bursera and Spondias were more frequently eaten at the site. Seeds dispersed individually rather than in larger aggregations (5, 10) were more likely to survive in mature forest and late secondary habitat. This advantage was lost in Bursera and Swietenia when they were dispersed to younger successional habitats.

At the early seedling stage, recruitment of Bursera and Swietenia was highest in the older secondary habitats. Seedlings of Erythrina showed the lowest overall losses to any of the mortality factors identified during the first two months of establishment. Seeds of forest tree species arriving in secondary habitat were more vulnerable to attack by non-flying vertebrates than in mature forest. Survival of seedlings of these species was most closely related to the moisture-conserving status of the habitat.

White-eyed vireos (Vireo griseus) winter in the forests and secondary growth of the Yucatan Peninsula where Bursera simaruba (Burseraceae) is an abundant tree. Twenty-five per cent of all white-eyed vireos observed foraging visited Bursera trees. In addition, presence and abundance of territorial white-eyed vireos in small forest patches were correlated with the size of the Bursera crop. Vireos were the most reliable dispersers of Bursera seeds. These birds visited 32 of 35 trees observed for at least three hours. They accounted for approximately half of all bird visits, and two-thirds of the seeds dispersed. Most of the other species rarely visited (<5% of visits) or failed to remove seeds from the tree.

Peculiarities of phenology and fruit structure may contribute to the tendency of Bursera to be dispersed by relatively few species. The capsules of Bursera fruits do not open when the fruit ripens; birds apparently locate ripe fruit using visual cues, although these are few. In addition, only a small portion of the crop ripens daily over a 7- or 8-month period. The vireo-Bursera simaruba relationship, found regionally on the Yucatan Peninsula, may result from the prolonged fruit ripening period (October-March), the relatively depauperate frugivore community and the relatively high density of small Bursera trees in the hurricane-disturbed dry forests.

Small trees at all times, and all trees from October to February, depend upon territorial vireos for continuous, highly efficient local dispersal of a small number of fruits. In March and April residual fruits ripen rapidly and synchronously, attracting a greater variety of visitors for broad spectrum dispersal during a period of food scarcity. Thus, Bursera has an unusual two-phase phenological pattern, perhaps alternately to take advantage of both specialized and opportunistic dispersers.

Measurements of reproductive allocation, fertility and iteroparity were made on females of four species of woodlice (Isopoda: Oniscidae) from southern Africa. In three of the species between-population comparisons were made. The average body mass of reproductive females was smaller than in temperate woodlice and because of a positive scaling between body mass and fertility: brood sizes were rarely larger than 30 young and usually between 5 and 20. Reproductive allocation ranged from 16 to 27% of female pre-birth live mass and differed significantly between species. Associations between reproductive allocation and body mass were all positive although only significant in two of the populations. A small number of females produced more than one brood during the study and iteroparity appears the most likely reproductive tactic in these species.

In woodlice a restriction on body size results in lower fecundity as brood size is ultimately determined by the size of the marsupium. It is postulated that a tactic of repeated reproduction, with a relatively conservative allocation of resources to each reproductive event to enhance survival probabilities, would be favoured, particularly in an environment where juvenile mortality and the chance of complete brood failure is high.

Some savanna areas in the Orinoco Llanos region in Venezuela are characterized by the abundance of small forest groves, resulting in a parkland landscape. We hypothesized that forest groves are the result of colonization of the open savanna by forest species, facilitated by the activity of leaf-cutting ants. In this paper we present results from a field study conducted on an ecotonal belt between a deciduous gallery forest and an open savanna in the western Llanos of Venezuela. In seven transects, trees, groves and leaf-cutting ant nests were counted, size parameters evaluated and distance from grove to forest measured. Soil chemical analysis and microclimatic measurements were performed in the forest, grassland and groves. Floristic composition of the woodland component of the savanna (scattered trees) was very dissimilar from that of the forest, but the composition of the groves was essentially a mixture of both woodland and forest species. Woodland trees were present in all groves, whereas forest trees were present only in larger groves. The size structures of populations of the two types of trees differed significandy according to the size of the grove; also, woodland tree population structure differed significantly between open savanna and groves. The frequency of groves with Atta laevigata nests increased with the size of the grove, and groves with forest trees were positively associated with the presence of nests. A. laevigata nests improved the soil of groves, increasing N, Mg, Ca and organic carbon, but other soil properties were not modified. Temperatures at ground level in the dry season were ameliorated in the groves compared with the grassland, and this effect increased with the size of the grove. We concluded that a dynamic process of grove formation is facilitated by the aggregation of a few woodland trees, followed by the successful invasion of forest trees and a leaf-cutting ant nest. The results did not show any clear sequence of arrival of the ants or the forest trees, but it seems clear that these two would act synergistically, improving conditions for each other.