North—South Patterns within Arboreal Ant Assemblages from Rain Forests in Eastern Australia1

This paper describes the ant assemblages sampled from rain forest canopies ranging from southern Victoria through to Cape York Peninsula, Australia, and also in Brunei. Specifically, it examines the influence of decreasing latitude and variations in elevation on the character, richness, and abundance of the arboreal rain forest ant fauna, and also the relative contribution of ants to the total arthropod community. The sites that were examined included: cool temperate Nothofagus cunninghamii forest from a range of locations in Victoria; cool temperate N. moorei forest at both Werrikimbe and Styx River, New South Wales; notophyll vine forest in Lamington National Park, southeast Queensland; high elevation notophyll vine forest in Eungella National Park, central Queensland; complex notophyll vine forest at Robson Creek, Atherton Tablelands, north Queensland; complex mesophyll vine forest at Cape Tribulation, north Queensland; and mixed dipterocarp forest in Brunei. Although these sites represent a gradient increasingly tropical in character, botanically speaking, Eungella is less tropical than Lamington because of its high elevation. All samples were obtained by fogging the canopy with a rapid‐knockdown pyrethrin pesticide. In all cases, circular funnels were suspended beneath the foliage of individual trees or small plots of mixed canopy. Arthropods were collected four hours after fogging. Following ordinal sorting, ants were identified and counted to morphospecies level. The resulting catch were then standardized across sites as numbers caught per 0.5 m² sampling funnel. Generic and species richness were higher at the lowland tropical Cape Tribulation sites than at the sites to the south and was comparable with values in the Brunei site. Species richness was negatively correlated with latitude and elevation. Within the Australian rain forest, the lowland/highland break appears to be the strongest predictor of ant relative abundance, with a weaker latitudinal relationship superimposed.     

The Role of Arboreal Seed Dispersal Groups on the Seed Rain of a Lowland Tropical Forest1

Most tropical plants produce fleshy fruits that are dispersed primarily by vertebrate frugivores. Behavioral disparities among vertebrate seed dispersers could influence patterns of seed distribution and thus forest structure. This study investigated the relative importance of arboreal seed dispersers and seed predators on the initial stage of forest organization–seed deposition. We asked the following questions: (1) To what degree do arboreal seed dispersers influence the species richness and abundance of the seed rain? and (2) Based on the plant species and strata of the forest for which they provide dispersal services, do arboreal seed dispersers represent similar or distinct functional groups? To answer these questions, seed rain was sampled for 12 months in the Dja Reserve, Cameroon. Seed traps representing five percent of the crown area were erected below the canopies of 90 trees belonging to nine focal tree species: 3 dispersed by monkeys, 3 dispersed by large frugivorous birds, and 3 wind‐dispersed species. Seeds disseminated by arboreal seed dispersers accounted for ca 12 percent of the seeds and 68 percent of the seed species identified in seed traps. Monkeys dispersed more than twice the number of seed species than large frugivorous birds, but birds dispersed more individual seeds. We identified two distinct functional dispersal groups, one composed of large frugivorous birds and one composed of monkeys, drop dispersers, and seed predators. These groups dispersed plants found in different canopy strata and exhibited low overlap in the seed species they disseminated. We conclude it is unlikely that seed dispersal services provided by monkeys could be compensated for by frugivorous birds in the event of their extirpation from Afrotropical forests.     

Tropical Rain Forest Recovery from Cyclone Damage and Fire in Samoa1

In 1990 and 1991, Samoa was struck by two cyclones, Ofa and Val. In the Tafua Rain Forest Preserve on the island of Savai'i, one part of the forest also burned after the first cyclone. Here we report on patterns of regeneration and changes in tree species composition in the Tafua lowland rain forest after five years of recovery from cyclone and fire disturbance. In the unburned area, tree canopy cover increased from 27 percent after the last cyclone to 58 percent, and in the burned area from below 12 to 49 percent. Nine of the ten most common tree species decreased in relative abundance in the entire forest after the last cyclone. One fast growing pioneer species, Macaranga harveyana now makes up 42 percent of the total number of trees (>5 cm DBH) in the unburned area and 86 percent in the burned area. Large interspecific differences occur in size distribution and there are at least four distinguishable regeneration patterns, which may be related to shade tolerance. Mean number of species per plot was generally higher in the unburned area than in the burned area, while the Shannon evenness index was higher in the unburned than in the burned area only for trees above 1 cm DBH. Species with fruits known to be fed upon by birds and/or bats generally made up a larger proportion of all trees in the burned than in the unburned area. In contrast to other studies of post‐cyclone regeneration, in which recovery is often rapid due to resprouting of trees, recovery in the Tafua forest was a slow process with regeneration more dependent on vertebrate seed dispersal than on resprouting.     

Successional Patterns of Microfungi in Fallen Leaves of Ficus pleurocarpa (Moraceae) in an Australian Tropical Rain Forest1

Successional patterns of microfungi on decaying leaves of Ficus pleurocarpa were assessed as part of a study to enumerate microfungi in tropical rain forest leaf litter. Leaves degraded into fragments over a period of 3 mo. Two methods were applied, a direct observational method and a particle filtration protocol. Using a direct method, 104 species were observed, while 53 sporulating taxa and 100 sterile morphotaxa were isolated by particle filtration. Overall patterns of succession were confirmed by both methods, but the relative abundance of species detected differed between the two methods. Nonmetric Multidimensional Scaling identified at least four successional stages and suggested that microfungal communities increased in similarity with advancing decay. Data collected by the direct method indicated a slow but steady decline of diversity with advancing decay, whereas an increase in diversity was detected by particle filtration. Synecological succession studies provide a useful tool to identify patterns and generate hypotheses. Understanding the underlying causes of successional patterns will require further autecological studies.     

Abundance of Gall Midges on Poulsenia armata (Moraceae): Importance of Host Plant Size and Light Environment in Tropical Rain Forests1

We studied the effects of contrasting light environments on the relationship between the host plant size of Poulsenia armata and the abundance of two gall midges in a tropical rain forest in Veracruz, Mexico. The number and density of two gall morphs (i.e., laminar and vein‐petiole galls) were positively correlated with plant size only in trees found in the forest but not in gaps. The availability of foliar area of P. armata trees was greater in forest gaps than in the forest. The foliar area was positively correlated with the abundance of laminar galls in trees in forest sites, but not with vein‐petiole galls. We concluded that the abundance of two morphs of gall midges on P. armata was associated with host plant size only in the forest trees. Larger plants had more galls than small plants, although this relationship was affected by local light environments.     

Nocturnal Fungi: Airborne Spores in the Canopy and Understory of a Tropical Rain Forest1

Pathogens and other symbiotic fungi that infect above‐ground plant parts commonly disperse as airborne spores. Here we present diel patterns of the density of airborne fungal spores in the canopy and understory of a tropical rain forest. Spores were 52‐fold more abundant in the understory than in the canopy. Additionally, spores were 5‐ to 35‐fold more abundant at night than during the day, associated with environmental conditions conducive to germination and plant infection.     

Ants Induce Domatia in a Rain Forest Tree (Vochysia vismiaefolia)1

In Amazonian rain forest trees of Vochysia vismiaefolia (Vochysiaceae), ants were found to induce twig structures that resembled classical ant domatia. This phenomenon is novel for ant‐plants, which commonly develop domatia without the activity of ants. Eight species of ants were recorded inside the domatia of six individual trees, but domatia were most numerous and characteristic when induced and inhabited by an undescribed species of Pseudomyrmex on two trees. To investigate the mechanism of domatium growth, we drilled holes into young twigs: the expansion of the twig diameter surrounding the holes was significantly accelerated, comparable to domatia formation. Domatia induction is discussed as a putative step in the evolution of ant‐plants.     

Predicting the Long-Term Effects of Hunting on Plant Species Composition and Diversity in Tropical Forests

Hunting can change abundances of vertebrate seed predators and seed dispersers, causing species‐specific changes in seed dispersal and seed predation and altering seedling communities. What are the consequences of these changes for the adult plant community in the next generation and beyond? Here, I derive equations showing how reduced seed dispersal reduces plant reproduction by intensifying kin competition, increasing vulnerability to natural enemies, and reducing the proportion of seeds passing through disperser guts. I parameterize these equations with available empirical data to estimate the likely effects on next‐generation abundances. I then consider the indirect effects and longer‐term feedbacks of changed seed or adult abundances on reproductive rates due to density‐dependent interactions with natural enemies and mutualists, as well as niche differentiation with competitors, and discuss their likely qualitative effects. The factors limiting seed disperser and seed predator populations in natural and hunted forests emerge as critical for determining the long‐term effects of hunting on rates of seed dispersal and seed predation. For example, where seed dispersers are held to a constant abundance by hunters, decreases in the availability of their preferred food plants are expected to lead to increased per‐seed dispersal probabilities, potentially to the point of compensating for the initial disperser decline. I close by discussing the likely reversibility of hunting‐induced changes in tropical forests and key questions and directions for future research.     

Landscape Patterns of Tropical Forest Recovery in the Republic of Palau1

A GIS (geographic information systems) database was constructed from aerial photographs, a vegetation map, and topographic map data of the Ngeremeduu Bay Drainage Area (NBDA), Palau, to examine relationships between upland land cover dynamics, environmental variables, and past land use. In 1992, 82.9 percent of the NBDA was forest, 16.6 percent was grassland, and 0.5 percent consisted of village areas. Between 1947 and 1992, there was a 11.2 percent reduction of grassland area primarily due to a 10.9 percent increase in forest cover. These land cover changes led to larger, more continuous stretches of forest and numerous, highly fragmented grassland patches. Significant relationships (P 0.001) were found between the spatial distribution of forest and grassland cover and slope, elevation, soil pH, and percent soil organic matter. These patterns, however, may have resulted from past farm site selection rather than from ecological relationships. Our results indicate that areas of forest expansion were significantly (P 0.001) associated with the location of abandoned agricultural communities. In addition, over 92 percent of areas of forest expansion occurred within 100 m of established forest. These results suggest that the proximity of established forest facilitate forest recovery following human disturbance.     

Seed Dynamics in Relation to Gaps in a Tropical Montane Rainforest of Hainan Island, South China： （I） Seed Rain

Seed dynamics is an important part of stand dynamics in forest ecosystems. In this paper, 26 gaps were randomly selected to study the influence of gaps on the spatial and temporal patterns of seed rains in a tropical montane rainforest of Hainan Island, South China. Three zones for each gap, including outside gap zone （Non-gap）, transitional gap zone （EG-CG）, and central gap zone （CG）, were designed, and fourseed traps （each lm x lm in size） were placed in each zone. Seed rains were collected by these traps every 10 days from June 2001 to May 2002. Seed rain varied greatly with season and generally exhibited a pattern of unimodal change during the study period： seed abundance and species richness were both greater in the wet season than in the dry season. Gaps significantly influenced the temporal patterns of both species richness and density of seed rains. Gaps had no significant influences on the spatial distribution patterns of seed rain species richness, but significantly affected the spatial distribution pattern of seed rain densities. Among the three different zones of gaps, the outside gap zone generally received more seeds inputs than the two other gap zones.     

Removal of Nonnative Vines and Post‐Hurricane Recruitment in Tropical Hardwood Forests of Florida1

In hardwood subtropical forests of southern Florida, nonnative vines have been hypothesized to be detrimental, as many species form dense “vine blankets” that shroud the forest. To investigate the effects of nonnative vines in post‐hurricane regeneration, we set up four large (two pairs of 30 X 60 m) study areas in each of three study sites. One of each pair was unmanaged and the other was managed by removal of nonnative plants, predominantly vines. Within these areas, we sampled vegetation in 5 X 5 m plots for stems 2 cm DBH (diameter at breast height) or greater and in 2 X 0.5 m plots for stems of all sizes. For five years, at annual censuses, we tagged and measured stems of vines, trees, shrubs and herbs in these plots. For each 5 X 5 m plot, we estimated percent coverage by individual vine species, using native and nonnative vines as classes. We investigated the hypotheses that: (1) plot coverage, occurrence and recruitment of nonnative vines were greater than that of native vines in unmanaged plots; (2) the management program was effective at reducing cover by nonnative vines; and (3) reduction of cover by nonnative vines improved recruitment of seedlings and saplings of native trees, shrubs, and herbs. In unmanaged plots, nonnative vines recruited more seedlings and had a significantly higher plot‐cover index, but not a higher frequency of occurrence. Management significantly reduced cover by nonnative vines and had a significant overall positive effect on recruitment of seedlings and saplings of native trees, shrubs and herbs. Management also affected the seedling community (which included vines, trees, shrubs, and herbs) in some unanticipated ways, favoring early successional species for a longer period of time. The vine species with the greatest potential to “strangle” gaps were those that rapidly formed dense cover, had shade tolerant seedling recruitment, and were animal‐dispersed. This suite of traits was more common in the nonnative vines than in the native vines. Our results suggest that some vines may alter the spatiotemporal pattern of recruitment sites in a forest ecosystem following a natural disturbance by creating many very shady spots very quickly.     

Home Range Size of Sympatric Squirrel Species Inhabiting a Lowland Dipterocarp Forest in Malaysia1

Home range sizes and spatial overlap of four sympatric squirrel species were investigated in a lowland dipterocarp forest in Malaysia using a radio‐tracking method. The population density of Callosciurus caniceps was highest and C. notatus was next highest, while C. nigrovittatus and Lariscus insignis were scarce. C. caniceps was larger than C. nigrovittatus and C. notatus while L. insignis was extremely small. For females, home range size was smaller in L. insignis than Callosciurus spp., which may support the body weight hypothesis: larger species have larger home ranges. Among the three Callosciurus species, female C. caniceps had the smallest home range. These differences were accounted for by habitat characteristics rather than by density or body weight; C. caniceps was dominant in bushy areas and used crowded small trees while C. notatus and C. nigrovittatus used large trees in the forest. In this study, home range size did not change seasonally; this differs from studies in temperate regions, possibly because food availability is much less variable among seasons in tropical rain forest. Home range overlap among heterospecific individuals was common but different species seemed to partition space by using different vertical levels of the forest. Consequently, the home range size and spatial overlap of sympatric squirrel species may be affected by habitat diversity in tropical rain forest.