Resource depletion and associated increases in interspecific competition are likely to influence differential habitat usage amongst a guild. We tested some prominent theoretical concepts using observed differences in seasonal habitat use amongst the savanna browser guild (elephant, giraffe, impala, kudu and nyala) in Hluhluwe-iMfolozi Park, South Africa. Herbivore locations (n = 3108) were recorded over 2 y using repeated road transects and, for elephant, GPS collars (187 254 downloads). Densities were calculated using a novel GIS approach designed to be a cost-effective method for annual censuses, but also able to cope with abrupt changes in visibility. Selectivity for (Manly's α) vegetation types, and overlap (Schoener's index) in vegetation type usage were calculated. Resource depletion in the dry season resulted in all members of the guild increasing selectivity for vegetation types (sum of absolute values away from the neutral value for Manly's alpha for the guild: dry seasons 3.97, 5.16; corresponding wet seasons 3.12, 3.68), but decreasing interspecific overlap (80% of Schoener's indices lower in dry season versus wet season). These effects were more marked over the second, more severe, dry season. We found support for the niche overlap hypothesis and the niche compression hypothesis. The Jarman–Bell principle was generally supported, although unexpectedly during the severe dry season elephant showed the most selectivity for vegetation type. The greater the resource depletion, the more relevant interspecific differences in habitat usage become in relation to the differential impacts of guild members.

Two synthetic DNA probes composed of tandemly repeated ‘core’ sequences (GACA and GATA) were used to examine genetic diversity at multiple variable-number-tandem-repeat (VNTR) loci within and among four spatially isolated Philippine populations of Rubus moluccanus L. (Rosaceae), an uncultivated bramble widely distributed throughout southeast Asia – Malesia. Central goals were to determine whether apomictic propagation was detectable in R. moluccanus and to examine whether populations isolated on separate islands, or on mountain tops on a single island, were genetically differentiated. Sampling 22 individuals per population, the findings include: (1) no two individuals shared identical VNTR band profiles and thus apomictic propagation was not detected; (2) the mean number of bands scored per individual was 24.3 (SD = 3.91) and the proportion of polymorphic loci within populations ranged from 0.69 to 1.00 (mean = 0.86 ± SD = 0.085); (3) the average proportion of bands shared between individuals within populations ranged from 0.39 to 0.67 (0.50 ± 0.067), while average interpopulation similarity ranged from 0.21 to 0.50 (0.32 ± 0.092); and (4) estimated heterozygosity within populations ranged from 0.42 to 0.79 (0.62 ± 0.083), while interpopulation heterozygosity ran from 0.62 to 0.81 (0.74 ± 0.062). Permutation tests were used to estimate the statistical significance of differences in similarity between populations. A Luzon population isolated by 1200 km was always significantly different in similarity tests when compared with each of the other three populations, all located on Mindanao (and separated by at least 100 km but less than 250 km). Of the latter three, only one population differed significantly from the other two in the degree of VNTR markers shared, possibly reflecting biogeographic partitioning suggested for the island. Across all populations, average estimated Fst was 0.154, although mean inter-island Fst (0.224) was significantly higher than mean intra-island Fst (0.085). These results suggest that, while intra-island gene flow is relatively high, significant differentiation of tropical species may occur even over short distances on individual islands. Preservation of only a limited number of populations may result in a significant loss of genetic diversity in such species.

The competition for resources increases size inequality in trees, particularly under low abiotic stress. Because mangrove communities are subject to site-specific salinity (and therefore abiotic stress) gradients, these habitats should differ in height–diameter allometry and size inequality. The size inequality (by the Gini Coefficient, G) and maximum potential height (Hmax from a height–diameter asymptotic model) were determined within the mangrove forest of a coastal lagoon in Veracruz, Mexico in 20 0.25-ha plots, 10 in interdistributary basins (IBs, lower salinity) having Avicennia germinans, Laguncularia racemosa and Rhizophora mangle and 10 in mudflats (MFs, higher salinity) dominated by A. germinans. Size inequality was significantly higher in IBs (G = 0.59 ± 0.02 vs. 0.39 ± 0.03). Due to their significant intercorrelation G, total basal area and density were synthesized in one PCA axis accounting for 67% of total variance and inversely correlated with salinity (R = −0.65, P = 0.003). The height–diameter scaling model reached a stable asymptote (Hmax range: 16–21 m; coefficient of variation CV: 7.7) in IBs, suggesting that trees can still increase their diameter after achieving maximum height. In MFs, no stable asymptote was reached (Hmax range: 11–26 m; CV: 32.5), suggesting a lower growth rate of diameter in the MF trees when compared with IB trees.

In South America, the invasive feral pig (Sus scrofa Linnaeus) has become established in Argentina, Uruguay, Paraguay and in a wide range within Brazil, along the southern half of the Atlantic Forest, in the cerrado (savanna) and in the Pantanal wetland. The geographical ranges of the two most common South American native peccary (Tayassu pecari Link and Pecari tajacu Linnaeus) overlap almost entirely, and the feral pig now co-occurs with them in several areas. Because feral pig, white-lipped and collared peccary are considered ecological equivalents, there has been much speculation about possible competitive interactions among them (Desbiez et al. 2009, Sicuro & Oliveira 2002).

The Dipterocarpaceae in South-East Asia are known for their strict mast fruiting. During fruiting, pre-dispersal seed predation by insects contributes to mortality of dipterocarp seeds. We documented the community structure of insect seed predators on 11 Shorea species in Peninsular Malaysia. Fruits were sampled sequentially throughout seed development, and 2144 and 1655 individuals of seed predator weevils and moths were collected in two mast-fruiting events. Four weevils: Nanophyes shoreae, nanophyid sp. 1, Alcidodes dipterocarpi and Alcidodes humeralis, and one moth Andrioplecta shoreae were abundant in seeds of the Shorea species. The proportion of N. shoreae to the total predators became larger in the latter fruiting event than the former while that of Alcidodes spp. became smaller. The predator species composition changed during seed development; nanophyid spp. emerged from immature fruits while Alcidodes spp. emerged from mature fruits. Andrioplecta shoreae emerged from both immature and mature fruits. The level of host specificity measured by Kullback–Leibler distance was low for most predator species in both events. Predator species composition of many Shorea was similar to each other due to the dominance of N. shoreae though it might gradually differ with the phylogenetic distance between hosts. In conclusion, predator species composition of Shorea varied during seed development within a host rather than among hosts. Intermittent synchronized fruiting by congeneric Shorea trees would be advantageous to avoid pre-dispersal insect seed predators, and contribute to their reproduction.

Many tropical tree species have buttresses at the standard breast height (1.3 m above ground) of diameter measurement, with a presumable role in improving nutrient acquisition or tree anchorage in the ground (Newbery et al. 2009, Richter 1984). Measuring the diameter using standard dendrometrical tools such as callipers or graduated tapes, which require that the cross-section of the trunk has a convex shape, is then impossible (Nogueira et al. 2006). The recommended method in this case is to measure the diameter above the buttress (DAB), thus possibly leading to biased estimates of the basal area (West 2009), of tree above-ground biomass (Dean & Roxburgh 2006, Dean et al. 2003) and of tree growth (Metcalf et al. 2009). As an alternative, one can measure the basal area at breast height of buttressed trees, using a method that can deal with the irregular non-convex shape of the cross-section of the stem such as the Picus calliper, photogrammetry or 3D laser scanning (Badia et al. 2003, Dean 2003, Newbery et al. 2009).

Climbing plants provide efficient pathways for ants to access patchy arboreal resources. However, plant stems vary greatly in physical characteristics that are likely to influence ant locomotion. We collected, measured and identified ants foraging on 671 stems of climbing plants at the La Selva Biological Station, Costa Rica. We applied tuna baits to 70% of the observed stems to attract ants to a broad range of stem sizes. We used these data to examine relationships between relative stem roughness, growth form (herbaceous or woody), stem diameter and the body length of foraging ants representing 58 species. The size of the largest ants found on stems generally increased with stem size up to 3.2 mm diameter, whereas the size of the smallest ants present on stems did not vary with stem diameter. The largest ants in the forest (Paraponera clavata) used small stems (<2.7 mm diameter) only when attracted by baits. Average (± SE) ant body length was larger on woody (5.2 ± 0.32 mm) vs. herbaceous (3.3 ± 0.53 mm) stems, but did not differ between rough and smooth stems within these categories. Ant body-size distribution tended toward unimodality on smooth stems. We conclude that small stem diameter acts as a habitat filter based on ant body size, but only for the largest ants in the forest. The filter effect is reduced when ants are attracted to an artificially high quality resource.

Leaf phenology and leaf traits of the fern Oleandra pistillaris were examined in relation to canopy cover (open and understorey) and seasonal reduction in rainfall in a wet tropical montane forest, Indonesia. Although the annual rainfall is high, rainfall is relatively less in June and July. Stomatal density and diameter were greater in the open than in the understorey (229 versus 167 mm−2 for stomatal density and 33 versus 29 μm for stomatal diameter). The stable carbon isotope ratio (δ13C) of leaves, positively correlated with water use efficiency, was higher in the open than in the understorey (mean δ13C −30 versus −33‰). Therefore, it is considered that leaves have high gas-exchange capacities per leaf area in the open where water availability would be limited, compared with the understorey. In contrast, leaf mass per area (LMA) was lower and leaf life span was longer in the understorey than in the open (25 versus 34 g m−2 for LMA and 2.1 and 1.6 y for leaf life span). These thin leaves with a long life span in the understorey would contribute to efficient light capture and photosynthetic production per leaf mass. The number of leaves per stem decreased during the period with less rainfall in both the open and understorey conditions, which should reduce the water loss from plants, but increased again after the period with less rainfall. Stem growth rate was higher in the open than in the understorey, and the seasonal reduction in rainfall hardly affected stem growth rate in either open or understorey conditions. This study concludes that O. pistillaris responds to canopy cover and seasonal reduction in rainfall by adjusting leaf traits and leaf phenology, respectively.

The competitive influence of the root system of the exotic grass Urochloa brizantha and the widespread forb Leonotis nepetifolia on the emergence, survival and early growth of the seedlings of eight tropical heliophilous herbaceous species, six early-successional woody species and five late-successional woody species from Brazil, grown in 3500-cm3 pots and in greenhouse without light restriction were assessed. The density of fine-root systems produced by the forb and the grass in pots were 6.8 cm cm−3 soil and 48.1 cm cm−3 soil, respectively. Seedlings survival of the heliophilous herbaceous, early- and late-successional woody species were 86%, 70% and 100% in presence of the forb root system and 12%, 14% and 100% in competition with grass root system, respectively. The competitive pressure applied by the grass root system on seedling growth of the heliophilous herbaceous, early- and late-successional woody species were 2.4, 1.9 and 1.4 times greater than the forb root system. Total root length of the heliophilous herbaceous, early- and late-successional woody species grown without competitors were 13, 33 and 5 times greater than in competition with forb, and were 66, 54 and 6 times greater than in competition with grass root system, respectively. The averages of fine-root diameter of plants grown without competitors were 209 μm for the heliophilous herbaceous, 281 μm for early-successional trees and 382 μm for late-successional trees. The root system of the forb did not avoid seedling establishment of most plant species, but the grass root system hampered more the establishment of heliophilous herbaceous and early-successional woody species than the seedling establishment of late-successional woody species. The different density of root systems produced in soil by the forb and the grass, and the distinct root traits (e.g. root diameter and root tissue density) of the early- and late-successional plant species can explain the differences in the establishment of seedlings of plant species belonging to different groups of tropical succession when exposed to below-ground competition.

A total of 14 spotlight surveys were carried out from January 1992 to February 1993 along 37 km of the Klias River in north-western Sabah, Malaysia. Surveys were at low tide between 1900 and 0600 h from a survey boat at 15 km h−1 by two observers. A total of 221 sightings were made, which varied between 2 and 29 per survey (mean 15.8). A total of 55 juvenile crocodiles were captured, with 16 recaptures. Calculated density was 0.9–1.8 individuals km−1, while the estimated crocodile population was 46.1 ± 10.2 (SD) for the survey area. Percentage sightings according to total length were: 42% ≤0.5 m; 40% >0.5-≤1.0 m; 5% > 1.0-≤3.0; and 13% eyes only. Recapture of 16 tagged juveniles suggested that hatchlings ≤0.5 m total length remained within >0.5 km of their release point for at least one month, and juveniles 0.5-≤1.0 m more than one year. Hatchlings had growth rates between 0.01 and 0.08 cm d−1 and 0.3 and 1.5 g d−1, while larger juveniles grew at least 0.11 cm d−1 and 2.7–2.9 g d−1. Stomachs of hatchlings and juveniles contained crabs (Ocypodidae), prawns (Atyidae), insects and small fish (Hemiramphidae). Relatively large numbers of juvenile Crocodylus porosus (82.4%) in the Klias River suggests that the area, though under hunting pressure, is desirable as a site for the conservation of C. porosus in the Sabah.

Convergence in the use of resources may occur between distantly related organisms. A major ecological resource in which members of various taxa may be interested is a cavity for nesting. A variety of social hymenopterans and vertebrates may nest within tree cavities in tropical ecosystems. We used 241 nest-boxes placed in seven Kenyan localities to investigate the use of nesting cavities by members of distant taxa and discuss whether interaction between them is a potential factor shaping cavity-nester communities in tropical regions. The nest-boxes were occupied by social insects (ants, bees and wasps) (30.1% of nest-boxes in April–May and 33.1% in September–October) and vertebrates (birds and mammals) (20% and 7.7%, respectively). Hymenopterans were more abundant in forest boxes (36.2% of nest-boxes occupied in April–May and 37% in September–October), whereas savannas had lower figures (21.7% and 31.3%, respectively). Among vertebrates, most occupants of nest-boxes in savanna were birds (17.8% of nest-boxes occupied vs. 8% in mammals), while mammals predominated in forests (4.9% of the nest-boxes occupied vs. 0.3% in birds). Spatial and temporal patterns of occupation highlight the potential that interaction between distant taxa may have on the access to nesting cavities. More nest-boxes remained unoccupied in forested areas than in savanna areas suggesting that a shorter supply of nesting sites in the savanna may be a source of competition. The simultaneous occupation of a nest-box by two different taxa was exceptional, also supporting the hypothesized inter-taxon competition.

The forests of western Amazonia support high site-level biological diversity, yet regional community heterogeneity is poorly understood. Using data from line transect surveys at 37 forest sites in south-eastern Peru, we assessed whether local primate assemblages are heterogeneous at the scale of a major watershed. We examined patterns of richness, abundance and community structure as a function of forest type, hunting pressure, land-management regime and geographic location. The primate assemblage composition and structure varied spatially across this relatively small region of Amazonia (≈ 85 000 km2), resulting from large-scale species patchiness rather than species turnover. Primate species richness varied among sites by a factor of two, community similarity by a factor of four and aggregate biomass by a factor of 45. Several environmental variables exhibited influence on community heterogeneity, though none as much as geographic location. Unflooded forest sites had higher species richness than floodplain forests, although neither numerical primate abundance nor aggregate biomass varied with forest type. Non-hunted sites safeguarded higher abundance and biomass, particularly of large-bodied species, than hunted sites. Spatial differences among species assemblages of a relatively generalist taxon like primates in this largely undisturbed forest region imply that community heterogeneity may be even greater in more species-rich taxa, as well as in regions of greater forest habitat diversity.

Leafing phenology of two dry-forest sites on soils of different depth (S = shallow, D = deep) at Shipstern Reserve, Belize, were compared at the start of the rainy season (April–June 2000). Trees ≥ 2.5 cm dbh were recorded weekly for 8 wk in three 0.04-ha plots per site. Ten species were analysed individually for their phenological patterns, of which the three most common were Bursera simaruba, Metopium brownei and Jatropha gaumeri. Trees were divided into those in the canopy (> 10 cm dbh) and the subcanopy (≤ 10 cm dbh). Site S had larger trees on average than site D. The proportion of trees flushing leaves at any one time was generally higher in site S than in site D, for both canopy and subcanopy trees. Leaf flush started 2 wk earlier in site S than site D for subcanopy trees, but only 0.5 wk earlier for the canopy trees. Leaf flush duration was 1.5 wk longer in site S than site D. Large trees in the subcanopy flushed leaves earlier than small ones at both sites but in the canopy just at site D. Large trees flushed leaves earlier than small ones in three species and small trees flushed leaves more rapidly in two species. Bursera and Jatropha followed the general trends but Metopium, with larger trees in site D than site S, showed the converse with onset of flushing 1 wk earlier in site D than site S. Differences in response of the canopy and subcanopy trees on each site can be accounted for by the predominance of spring-flushing or stem-succulent species in site S and a tendency for evergreen species to occur in site D. Early flushing of relatively larger trees in site D most likely requires access to deeper soil water reserves but small and large trees utilize stored tree water in site S.

Bat-pollinated (chiropterophilous) flowers are characterized by a wide-throated corolla, foetid odour, production of a copious amount of pollen and nectar, and most importantly nocturnal blooming (Faegri & van der Pijl 1979). In India, out of the 28 chiropterophilous plants reported (Subramanya & Radhamani 1993) only Ceiba pentandra (Bombacaceae) has been investigated in some detail (Nathan et al. 2005).

The root and trunk characteristics of species in a complex, lowland, evergreen, tropical rainforest at a seasonally inundated, coastal site on siliceous sands were examined. Roots in the soil were predominantly colonized by arbuscular mycorrhizal fungi although ectomycorrhizas were found on four species which contributed almost 25% of total basal area. Surface root mats were not a characteristic of the study site. In contrast, the ability to produce apogeotropic (upwardly growing) aerial roots which grew on and within the bark on trunks and branches was a consistent feature of the dominant species of trees in this forest. Eleven species representing eight families and constituting more than 85% of the basal area at the site produced these roots. Most trunks with DBH greater than 20 cm supported apogeotropic aerial roots produced by a range of species including themselves. Apogeotropic roots were most frequently found on the basal 0.5 m of trunks; however, they did occur up to 5 m above the forest floor. Apogeotropic aerial roots originated both from epicormic buds under the bark and from soil, and they were frequently colonized by arbuscular mycorrhizal and ectomycorrhizal fungi. There was a strong association between the ability to support these upwardly growing roots and the occurrence of laminated papery and flaky bark. We postulate that production of apogeotropic roots may provide a mechanism for nutrient uptake and root respiration during periods of inundation, for intercepting nutrients in stemflow and/or for extracting nutrients from bark.

We aimed at (1) determining how community-wide disruptions affect visitation by frugivores at trees and (2) estimating the impact of visitation shifts on seed fate following fruit consumption, especially seed removal. We compared the seed fate of a frugivore-dispersed tree species (Tetragastris altissima, Burseraceae) in four forested islands with that for a mainland continuous forest at Saint-Eugène, French Guiana. Tetragastris trees attracted opportunistic frugivore species available in the area, the most productive trees attracting more consumer species. Only primates, which are more susceptible to forest disturbances than birds and have low abilities to cross a non-forested matrix, were more frequent at Tetragastris on the mainland than on islands. Only opportunistic frugivorous primate species acting as low-efficiency seed dispersers were recorded. As a result, seed removal was equally low among habitats (nearly 26%), high percentages of seeds dropping below tree crowns. The scarcity of large-bodied specialist frugivorous primates throughout the landscape probably explained this low removal. Our results underline how difficult it is to generalize the cascading effects of disruptions in a frugivore community on tree seed fate, these effects likely varying according to the tree species and animal community involved.

The genetic diversity of Myrciaria floribunda, a common Atlantic Forest tree, was investigated in six populations located in two small fragments (10 and 18 ha), two medium-sized fragments (36 and 44 ha) and one large fragment (3003 ha). Two populations occur in the large fragment. It is expected that smaller fragments should have lower genetic diversity and higher inbreeding. Distances between fragments varied from 0.66 to 10 km. On average 32 young trees smaller than 20 cm basal girth were sampled in each population. Allozyme electrophoresis was carried out, and six loci were scored. The effective number of alleles was lower for populations of the two small fragments (1.46 and 1.51) and higher for populations of the large (1.62 and 1.71) and medium ones (1.69 and 1.84). Small fragments showed lower values of expected and observed heterozygosities than large and medium fragments. Most of the genetic variability occurs within populations, and there was a moderate genetic variation among them ($\hat{\theta}_p$ = 0.097). Our findings show a tendency of lower genetic diversity within small and isolated fragments and higher genetic differentiation among them. But, few correlations between genetic diversity indices and fragment features (size and isolation) were significant.