Fruit Production in Mature and Recently Regenerated Forests of the Appalachians

ABSTRACT Fleshy fruit is a key food resource for both game and nongame wildlife, and it may be especially important for migratory birds during fall and for resident birds and mammals during winter. Land managers need to know how land uses affect the quantities and species of fruit produced in different forest types and how fruit production varies seasonally and as young stands mature. During June 1999-April 2004, we quantified fleshy fruit abundance monthly in 31 0.1-ha plots in 2 silvicultural treatments: 1) young 2-age stands with low basal area retention, created by shelterwood-with-reserves regeneration cuts (R; harvested 1998–1999); and 2) uncut mature closed-canopy stands (M) in 2 common southern Appalachian, USA, forest types (upland hardwood and cove hardwood [CH] forests). Over the 5-year study period, total dry pulp biomass production was low and relatively constant in both M forest types (x̄ = 0.5-2.0 kg/ha). In contrast, fruit production increased each year in R, and it was 5.0 to 19.6 times greater in R than in M stands beginning 3–5 years postharvest. Two disturbance-associated species, pokeweed (Phytolacca americana) and blackberry (Rubus allegheniensis), produced a large proportion of fruit in R but showed different patterns of establishment and decline. Huckleberry (Gaylussacia ursina) recovered rapidly after harvest and was a major producer in both silvicultural treatments and forest types each year. Several herbaceous species that are not associated with disturbance produced more fruit in CHR. Few species produced more fruit in M than in R. Fruit production by most tree species was similar between R and M, due to fruiting by stump sprouts in R within 1–3 years postharvest. Fruit availability was highest during summer and early fall. American holly (Ilex opaca), sumac (Rhus spp.), and greenbriar (Smilax spp.) retained fruit during winter months but were patchy in distribution. In the southern Appalachians, young recently regenerated stands provide abundant fruit compared to mature forest stands and represent an important source of food for wildlife for several years after harvest. Fruit availability differs temporally and spatially because of differences in species composition, fruiting phenology, and the dynamic process of colonization and recovery in recently harvested stands. Land managers could enhance fruit availability for many game and nongame species by creating or maintaining young stands within forests.     

Long-term patterns of fruit production in five forest types of the South Carolina upper coastal plain

Fleshy fruit is a key food resource for many vertebrates and may be particularly important energy source to birds during fall migration and winter. Hence, land managers should know how fruit availability varies among forest types, seasons, and years. We quantified fleshy fruit abundance monthly for 9 years (1995–2003) in 56 0.1-ha plots in 5 forest types of South Carolina's upper Coastal Plain, USA. Forest types were mature upland hardwood and bottomland hardwood forest, mature closed-canopy loblolly (Pinus taeda) and longleaf pine (P. palustris) plantation, and recent clearcut regeneration harvests planted with longleaf pine seedlings. Mean annual number of fruits and dry fruit pulp mass were highest in regeneration harvests (264,592 ± 37,444 fruits; 12,009 ± 2,392 g/ha), upland hardwoods (60,769 ± 7,667 fruits; 5,079 ± 529 g/ha), and bottomland hardwoods (65,614 ± 8,351 fruits; 4,621 ± 677 g/ha), and lowest in longleaf pine (44,104 ± 8,301 fruits; 4,102 ± 877 g/ha) and loblolly (39,532 ± 5,034 fruits; 3,261 ± 492 g/ha) plantations. Fruit production was initially high in regeneration harvests and declined with stand development and canopy closure (1995–2003). Fruit availability was highest June–September and lowest in April. More species of fruit-producing plants occurred in upland hardwoods, bottomland hardwoods, and regeneration harvests than in loblolly and longleaf pine plantations. Several species produced fruit only in 1 or 2 forest types. In sum, fruit availability varied temporally and spatially because of differences in species composition among forest types and age classes, patchy distributions of fruiting plants both within and among forest types, fruiting phenology, high inter-annual variation in fruit crop size by some dominant fruit-producing species, and the dynamic process of disturbance-adapted species colonization and decline, or recovery in recently harvested stands. Land managers could enhance fruit availability for wildlife by creating and maintaining diverse forest types and age classes. © 2012 The Wildlife Society.     

Fruit production is influenced by tree size and size‐asymmetric crowding in a wet tropical forest

In tropical forest communities, seedling recruitment can be limited by the number of fruit produced by adults. Fruit production tends to be highly unequal among trees of the same species, which may be due to environmental factors. We observed fruit production for ~2,000 trees of 17 species across 3 years in a wet tropical forest in Costa Rica. Fruit production was modeled as a function of tree size, nutrient availability, and neighborhood crowding. Following model selection, tree size and neighborhood crowding predicted both the probability of reproduction and the number of fruit produced. Nutrient availability only predicted only the probability of reproduction. In all species, larger trees were more likely to be reproductive and produce more fruit. In addition, number of fruit was strongly negatively related to presence of larger neighboring trees in 13 species; presence of all neighboring trees had a weak‐to‐moderate negative influence on reproductive status in 16 species. Among various metrics of soil nutrient availability, only sum of base cations was positively associated with reproductive status, and for only four species. Synthesis Overall, these results suggest that direct influences on fruit production tend to be mediated through tree size and crowding from neighboring trees, rather than soil nutrients. However, we found variation in the effects of neighbors and nutrients among species; mechanistic studies of allocation to fruit production are needed to explain these differences.     

Characteristics and abundance of vertebrate-dispersed fruits in temperate wet sclerophyll forest in southeastern Australia

The diversity, abundance and display characteristics of plants producing fleshy fruits were recorded in wet sclerophyll forest near Melbourne, Victoria. Fruit characteristics and nutrient content were recorded for 14 species of fruits occurring in the forest and these characteristics compared with similar studies in north temperate and tropical regions. Plants producing fleshy fruits were confined to understorey layers and comprised 13.5% of the native vascular flora. Most species displayed fruits conspicuously by ripening brightly coloured fruits synchronously in large displays. Annual fruit production at three sites ranged from 6.98 to 37.01 kg/ha. Fruit mass, seed number and size were variable but the proportion of pulp per fruit remained remarkably consistent between species. Most fruit pulp contained high quantities of soluble carbohydrates and little lipid or protein. Fruits from wet sclerophyll forest did not differ from fruits from other geographic areas in eight characteristics measured. Although taxonomically distinct, the species in wet sclerophyll forest were not significantly different from other temperate fruits, suggesting that fruit characteristics are under the influence of factors other than phylogeny.     

The relationship between fruit production and primate abundance in Neotropical communities

Ecological models predict a positive correlation between fruit production and primate abundance in the Neotropics. To test this relationship, I compiled information on primate abundance and calculated different indexes of fruit production for 30 Neotropical sites. These indexes can be grouped in three categories: (1) Fruit production estimates based on fruit traps, (2) basal area of endozoochorous trees and (3) density of these trees. The first estimate was the best predictor of both primate biomass ( r ²= 0.80) and species richness ( r ²= 0.64). The advantage of using fruit trap estimates is that they take into account production rates (which is not the case for basal area or density estimates), while the advantage of using basal area over density estimates is that it includes some of the expected variation due to tree size. However, using both basal area and density indexes I found a positive correlation between the basal area index and primate biomass for frugivorous monkeys and small platyrhines, but there was no correlation for folivorous and seed predator primates. I also found a positive correlation between pitheciine biomass and the abundance of Eschweilera trees. The analyses gave little support to the importance of suggested keystone resources such as figs and palms. Finally, when including climatic, geographic and plant diversity variables, fruit production continued to be a good predictor of primate biomass in the Neotropics, but primate species richness was best predicted by latitudinal gradients and plant species richness.     

Effects of enhanced UV-B radiation on fitness of an alpine species Cerastium glomeratum Thuill

Aims Information about how species respond to extreme environments, such as high UV-B radiation, is very useful in estimating natural ecosystem structure and functions in alpine areas. Our aim is to examine the effect of enhanced UV-B radiation on the fitness of an alpine meadow annual species on Qinghai-Tibet Plateau.Methods Plants of Cerastium glomeratum Thuill. were exposed to ambient (control) or ambient plus supplemental UV-B radiation (enhanced), simulating a 9% ozone depletion over Gannan, China (102°53′E, 34°55′N, 2900 m in altitude), up to leaf senescence and fruit maturation. Plant height, flower phenology, biomass allocation and reproductive parameters of the species were measured.Important findings Plant height in C. glomeratum was reduced by enhanced UV-B radiation at early growth stages and compensated with ongoing development. Fruit biomass, aboveground biomass, total biomass and reproductive effort (fruit dry mass/aboveground biomass) were not affected by enhanced UV-B radiation, but a significant increase in root/shoot ratio was found. Enhanced UV-B radiation delayed onset of flowering by 1 day and shortened duration of flowering by 5 days in C. glomeratum. But because of the long period of flowering time (83–88 days), this did not make any significant effect on flower number, seed number, pollination success (number of seeds per fruit) or reproductive success (fruit to flower ratio) in C. glomeratum. Enhanced UV-B radiation had no effect on seed germination and seed mass either. And the high production and low germination rate of the seed might be the strategy of C. glomeratum to survive the extreme environments on alpine meadow. All these results showed that C. glomeratum was tolerant to enhanced UV-B radiation.     

The distribution,density and biomass density of lizards in a semi–arid environment of northern Kenya*

An attempt was made to determine the species composition, density and biomass density of lizards in some of the principal land units in South Turkana. Thirteen species were recorded. Density estimates were determined from quadrat sampling in representative habitats. Because the number of lizards active was found to vary with time of day and temperature, minimum density estimates were obtained by confining counts to peak activity periods. Biomass density was calculated from the product of species density and the mean population weight measured from shot specimens. The biomass density estimate of the lizard fauna was found to be about 4–5% of the large mammal fauna, and appreciably more in the more arid land units. The species composition of South Turkana lizards show affinities to the Somali fauna, though not to the extent of the East Rudolf fauna, suggesting a more recent penetration of arid–adapted species.     

Fruiting phenology of palms and trees in an Atlantic rainforest land-bridge island

Tropical forests show periods of scarcity and high fruit production in the same year and/or between years. Palms are an important component of Neotropical rainforests and a significant food resource for several frugivores. Therefore, their role as keystone resource may be exacerbated in highly impoverished areas. In Anchieta Island, São Paulo/Brazil, human settlements have modified and impoverished the forest, mainly through overharvesting and the introduction of exotic plants and several mammal species. We assessed the offer of fruits consumed by vertebrate frugivores at this island, the vegetation of which is belonging to the Brazilian Atlantic rainforest. We compared whether the fruiting patterns and fruit fall differ between palms and trees, and discuss the importance of palms as a food resource for frugivores and the implications for Anchieta Island conservation. Phenological patterns were seasonal for both trees and palms; however, the times of fruiting occurrence differed. Fruit fall biomass was at least twice lower than reported for other Atlantic rain forests and was also different between trees and palms. Palms contributed more than 80% of the overall fruit fall biomass. Palms may constitute an alternative food resource in periods of low fruit availability, although they do not provide resources for the entire assemblage of vertebrate frugivores. Energy-rich fruits, such as those produced by palms, may play an important role in the maintenance of frugivore populations in isolated, disturbed environments with a high density of vertebrate frugivores, low diversity of fruiting species and fruit biomass such as those found on Anchieta Island.     

Large-scale spatial variation in palm fruit abundance across a tropical moist forest estimated from high-resolution aerial photographs

Fruit abundance is a critical factor in ecological studies of tropical forest animals and plants, but difficult to measure at large spatial scales. We tried to estimate spatial variation in fruit abundance on a relatively large spatial scale using low altitude, high‐resolution aerial photography. We measured fruit production for all 555 individuals of the arborescent palm Astrocaryum standleyanum across 25 ha of mapped tropical moist forest on Barro Colorado Island, Panama, by visually counting fruits from the ground. Simultaneously, we used high‐resolution aerial photographs to map sun‐exposed crowns of the palm across the same area, which were then linked to ground‐mapped stems. First, we verified that the fruit crop size of individual trees was positively associated with both crown presence on aerial photos and crown area visible on aerial photos. Then, we determined how well spatial variation in Astrocaryum fruit density across the study area was predicted by spatial densities of photo‐detected crowns and crown area compared to spatial densities of ground‐mapped stems and stem diameters. We found a positive association of fruit crop size with crown visibility on aerial photographs. Although representing just one third of all individuals in the study area, photo‐detected crowns represented 57% of all fruits produced. The spatial pattern of photo‐detected crowns was strongly correlated with the spatial pattern of fruit abundance based on direct fruit counts, and correctly showed the areas with the highest and lowest fruit abundances. The spatial density of photo‐detected crowns predicted spatial variation in fruit abundance equally well as did the spatial density of ground‐mapped stems. Photo‐detected crown area did not yield a better prediction. Our study indicates that remote sensing of crowns can be a reliable and cost‐effective method for estimating spatial variation in fruit abundance across large areas for highly distinctive canopy species. Our study is also among the few to provide empirical evidence for a positive relationship between crown exposure of forest trees and fruit production.     

Fruit biomass availability along a forest cover gradient

Habitat loss is the main driver of the current high rate of species extinction, particularly in tropical forests. Understanding the factors associated with biodiversity loss, such as the extinction of species interactions and ecological functions, is an urgent priority. Here, our aim was to evaluate how landscape‐scale forest cover influences fruit biomass comparing different tree functional groups. We sampled 20 forest fragments located within landscapes with forest cover ranging from 2 to 93 percent in the Atlantic forest of southern Bahia, Brazil. In each fragment, we established five plots of 25 × 4 m and carried out phenological observations on fleshy fruit throughout 1 year on all trees ≥5 cm dbh. We estimated fruit availability by direct counting of all fruits and derived fruit biomass from this count. We used spatial mixed linear models to evaluate the effects of forest cover on species richness, abundance, and fruit biomass. Our results indicated that forest cover was the main explanatory variable and negatively influenced the total richness and abundance of zoochoric and shade‐tolerant but not shade‐intolerant species. A linear model best explained variations in richness and abundance of total and shade‐tolerant species. We also found that forest cover was positively correlated with the fruit biomass produced by all species and by the shade‐tolerant assemblages, with linear models best explaining both relationships. The loss of shade‐tolerant species and the lower fruit production in fragments with lower landscape‐scale forest cover may have implications for the maintenance of frugivore, seed dispersal service, and plant recruitment.     

The role of forest structure and human occupation in structuring mammal assemblages in oligotrophic ecosystems of Central Amazonia

Large mammals are vulnerable to extinction, and respond directly to ecological gradients within the forest and to the intensity of forest product use by humans. In this study, we evaluated the effects of differences in forest structure and human occupation history on the composition of medium and large‐sized mammal assemblages of the terra‐firme forests of the Anavilhanas National Park, one of the most oligotrophic Amazonian ecosystems. Mammal surveys were conducted along 11 linear transects of 4 km, six of which were located in areas once inhabited by people and managed until the year that the park was created (over 30 years ago), and five in areas that were not inhabited at that time. We detected 469 individuals of 26 species during diurnal and nocturnal sampling, and 11 additional species outside transects. Human occupation history was strongly related to forest structure components. Fruit biomass, canopy cover and tree size were strongly associated with uninhabited areas, and influenced the structure of mammal assemblages. A direct relationship between diet category and species size was observed. Large frugivore‐herbivores and carnivores were more closely associated with areas with more fruit, larger trees and greater canopy cover. In contrast, small arboreal frugivore‐omnivores associated more closely with open canopy and smaller trees. Our study indicated that the effects of human occupation history on forest structure are still evident three decades after the removal of local people from the park. This long‐term effect can be explained by the low resilience of the Anavilhanas environments, demonstrating the fragility of mammal assemblages in face of anthropogenic variation in forest structure in the oligotrophic ecosystems of the Negro River basin.     

Effects of Local Plant Density and Incomplete Dichogamy on the Reproductive Success of the Rare Neotropical Palm Geonoma epetiolata

Density dependent processes are known to influence reproduction and establishment of plant populations. In this study, we evaluated the effects of local density and sexual expression on the reproductive success of the rare palm species Geonoma epetiolata in Costa Rica. We classified individuals in two density categories based on distances to the two nearest neighbors and recorded the occurrence of sexual overlap on each individual. Overlap between pistillate and staminate flowers in monoecious plants allows geitonogamous pollination, potentially reducing dependence on mates for reproduction. We measured plant size and light availability, and evaluated the influence of these variables on pollination success, fruit production, fruit abortion and seed mass. Pollination success significantly increased with density but there was no effect of sexual overlap. In contrast, there was no effect of density on the probability of initiated fruit, and a negative effect on fruit set. Fruit abortion was lowest in isolated plants with no sexual overlap. Plant size and light did not contribute to variation in reproductive success. In conclusion, the pollination advantage of plants in dense neighborhoods does not compensate reproductive losses incurred by fruit abortion, possibly due to mating among genetically related individuals. Geonoma epetiolata is threatened by habitat loss and poaching of seeds for the horticultural market. High fruit abortion rates associated with density in G. epetiolata suggest that seed collections from the remnant wild populations of this palm species may cause bottlenecks that further threaten population viability.     

The line transect method for estimating densities of large mammals in a tropical deciduous forest: An evaluation of models and field experiments

We have evaluated techniques of estimating animal density through direct counts using line transects during 1988–92 in the tropical deciduous forests of Mudumalui Sanctuary in southern India for four species of large herbivorous mammals, namely, chital (Axis axis). sambar (Cervus unicolor). Asian elephant (Elephas maximus) and gaur (Bos gaurus) Density estimates derived from the Fourier Series and the Half-Normal models consistently had the lowest coefficient of variation. These two models also generated similar mean density estimates. For the Fourier Series estimator, appropriate cut-off widths for analyzing line transect data for the four species are suggested. Grouping data into various distance classes did not produce any appreciable differences in estimates of mean density or their variances, although model fit is generally better when data arc placed in fewer groups. The sampling effort needed to achieve a desired precision (coefficient of variation) in the density estimate is derived. A sampling effort of 800 km of transects returned a 10% coefficient of variation on estimate for ehital; for the other species a higher effort was needed to achieve this level of precision. There was no statistically significant relationship between detectability of a group and the size of the group for any species. Density estimates along roads were generally significantly different from those in the interior of the forest, indicating that road-side counts many not be appropriate for most species.     

Effects of Single and Recurrent Wildfires on Fruit Production and Large Vertebrate Abundance in a Central Amazonian Forest

Wildfires are an increasing threat to tropical rainforests, yet little is known about their effects on fruit production and forest wildlife. We examined the effects of both single and recurrent wildfires on fruit production and large vertebrate abundance in a central Amazonian terra firme forest for 3 years following a large fire event. The estimated mortality of 42 and 74% of stems ≥10 cm in once- and twice-burnt forest led to a substantial loss of fruiting tree basal area (29 and 62% were lost in once- and twice-burnt forest, respectively) and crown coverage of fruiting woody lianas (89 and 97% were lost in once- and twice-burnt forest, respectively). Some important tree families producing fleshy fruits were less abundant than expected in once- and twice-burnt forest, suggesting that tree mortality was non-random in terms of species composition. Asynchronous fruit production was affected, and burnt forest transects sustained a much lower fruiting basal area, and fewer fruiting species during the dry season period of fruit scarcity. The number of fruiting trees in once- and twice-burnt forest was higher than the number predicted from actual levels of tree mortality recorded in each fire disturbance treatment, suggesting some surviving trees which may have benefited from higher irradiance levels and lower competition for resources. Many large frugivores and other vertebrate species declined in response to single fires, and most primary forest specialists were extirpated from twice-burnt forest, which sustained a higher number of species associated with second growth and other disturbed habitats.     

西双版纳阳春砂仁栽培的两种模式的比较研究

 阳春砂仁(Amomum villosum)种植对热带湿性季节雨林的影响十分显著,对次生林的影响不大。为保护热带雨林,改变现有阳春砂仁栽培模式,探讨雨林下种阳春砂仁改为次生林下种植阳春砂仁的可行性,比较研究了热带雨林和次生林下阳春砂仁的生长状况和产量。次生林和雨林林下阳春砂仁壮株密度和生物量均明显高于其它株型,同类型林下阳春砂仁笋、苗和衰老株密度差异不显著,但衰老株生物量显著高于笋和苗。次生林和雨林下阳春砂仁笋和苗的密度之和分别为衰老株的1.45和2.18倍,远多于衰老株数量。表明阳春砂仁种群能够维持稳定。值得注意的是阳春砂仁产量很低,茎生物量比很高（0.58以上）,果实生物量比极低（约0.01）,增产潜力较大。在水分较充足的一块次生林样地阳春砂仁果实产量高达211.149 0 kg•hm-2,远高于其它样地。阳春砂仁喜湿可能与其较低的根生物量比和浅根系有关。阳春砂仁叶面积指数、壮株和全部植株生物量与果实产量呈极显著的正相关。次生林和雨林林下阳春砂仁生物量、产量叶面积指数和各株型密度差异均不显著。研究结果表明次生林下可以种植阳春砂仁。     

Influence of Fruit Availability on Ecological Overlap among Four Neotropical Primates at Tinigua National Park,Colombia1

Data on fruit abundance and ecological overlap among Ateles belzebuth, Lagothrix lagothricha, Cebus apella, andAlouatta seniculus were gathered during 13 months at Tinigua National Park (Colombia), in an effort to test the following hypotheses concerning competition for fruits. Coexistence is possible because: (1) during periods when fruit availability is limited, the species utilize different resources; and (2) the species have different fruit preferences independent of fruit production in the forest. Differences were found in resource use (diet and habitat) for all four species. Despite these differences, all four devoted large proportions of time feeding on fruit. Fruit abundance influenced their activity patterns. Ninety percent of all interspecific aggressive interactions (TV = 69) were seen in fruiting trees. The first hypothesis was best supported, given that all species significantly increased their intake of the vegetative parts of plants during periods of fruit scarcity. Fruit partitioning during periods of scarcity was observed clearly only for one pair of species (C. apella and L. lagothricha). In general, the second hypothesis was not supported as a mechanism for reducing competition because most fruit species were consumed by more than one primate species. Fruit preferences, however, may be particularly important in explaining differences in niche overlap between the most ecologically similar species: A. belzebuth relied heavily on the fruits of one palm species (Oenocarpus bataud) during periods of fruit scarcity and abundance, while L. lagothricha completely ignored this fruit.     

The influence of elevated CO2 on species phenology, growth and reproduction in a Mediterranean old-field community

We studied the effects on the phenology, growth and reproduction of 19 Mediterranean species, of elevating the atmospheric CO₂ concentration ([CO₂]) to twice-ambient. Intact monoliths were taken from an old-field and put, during a six month growing season, into growth chambers in which external climatic conditions were mimicked and [CO₂] was regulated. Fruit set time was significantly changed in six species under elevated [CO₂] and leaf and branch senescence accelerated in most species. Grasses had fewer leaves and legumes were more branched at peak production under elevated [CO₂] than under ambient. Plant seed number was not significantly changed under elevated [CO₂], whereas the reproductive effort of grasses was significantly depressed. Reproductive and vegetative characteristics showed related responses to [CO₂], as species with enhanced biomass had a hastened fruit set time, a higher number of fruits per plant and a higher reproductive biomass under elevated [CO₂] than under ambient conditions, while species with depressed biomass had a delayed fruit set time, a lower number of fruits per plant and a lower reproductive biomass. Our results also show a high interspecific variability in [CO₂] response, but some trends emerged at the family level: the production of vegetative and reproductive modules were depressed in grasses and slightly stimulated in legumes.     

A comparison of three sampling techniques to estimate the population size of caterpillars in trees

Three sampling techniques commonly used to estimate the population size of caterpillars and sawfly larvae in trees (branch samples, frass production, water basins), were compared with respect to sampling error and economic costs. At the level of tree populations (e.g. forests), on an arbitrary date, the mean caterpillar intensity per tree (expressed in numbers of larvae or their biomass per 100 shoots) was predicted from the mean frass production per tree (expressed in mg frass per m² forest floor per day). At the level of the single tree, the frass production on an arbitrary date was related to the population intensity, but, due to the large sampling error, did not provide an accurate prediction. Summing the frass produced over the whole season reduced this error and predicted the seasonal abundance of larvae in single trees, estimated as their maximum intensity or their density (numbers of larvae or their biomass per m² forest floor). The maximum population intensity was not related to the population density. The sampling techniques suffer from large errors unrelated to larval abundance. The main sources of error (i.e. weather or predation of the larvae) usually cause an underestimation of population size. Labour, the main cause of high costs, was low in the basin technique and high in the frass production technique. Possible ways of reducing errors and applications of the three techniques are discussed.     

An efficient strategy to estimate intensity and prevalence: sampling metacercariae in fishes

Accurate estimates of population-level parameters of parasites, such as prevalence and mean intensity, require large sample sizes. The processing of such samples becomes an overwhelming task when parasites are abundant, as with trematode metacercariae in fishes. In the present study, a subsampling method reduced processing time while maintaining an accurate estimation of metacercariae prevalence and intensity across 3 trematode species and 2 fish species. By double sampling, we generated regression models to predict total intensity from a combination of subsamples. The key to this approach lies in choosing the best strategy from a large number of potential subsampling routines. We selected the most efficient routine by weighing the costs and benefits of each. This approach, however, could not provide an estimate of parasite abundance when no parasites occurred in the initial subsample. To estimate prevalence accurately, our subsampling algorithm prescribed an additional sampling sequence using a new, optimal regression model. In addition, we optimized the technique to measure three parasite species infecting a single host simultaneously. This efficient subsampling procedure decreased the overall processing time per host by up to 91% while obtaining accurate (R2 > 0.8) estimates for both prevalence and intensity.     

Diet and seasonal changes in sympatric gorillas and chimpanzees at Kahuzi–Biega National Park

Based on 8 years of observations of a group of western lowland gorillas (Gorilla beringei graueri) and a unit-group of chimpanzees (Pan troglodytes schweinfurthii) living sympatrically in the montane forest at Kahuzi–Biega National Park, we compared their diet and analyzed dietary overlap between them in relation to fruit phenology. Data on fruit consumption were collected mainly from fecal samples, and phenology of preferred ape fruits was estimated by monitoring. Totals of 231 plant foods (116 species) and 137 plant foods (104 species) were recorded for gorillas and chimpanzees, respectively. Among these, 38% of gorilla foods and 64% of chimpanzee foods were eaten by both apes. Fruits accounted for the largest overlap between them (77% for gorillas and 59% for chimpanzees). Gorillas consumed more species of vegetative foods (especially bark) exclusively whereas chimpanzees consumed more species of fruits and animal foods exclusively. Although the number of fruit species available in the montane forest of Kahuzi is much lower than that in lowland forest, the number of fruit species per chimpanzee fecal sample (average 2.7 species) was similar to that for chimpanzees in the lowland habitats. By contrast, the number of fruit species per gorilla fecal sample (average 0.8 species) was much lower than that for gorillas in the lowland habitats. Fruit consumption by both apes tended to increase during the dry season when ripe fruits were more abundant in their habitat. However, the number of fruit species consumed by chimpanzees did not change according to ripe fruit abundance. The species differences in fruit consumption may be attributed to the wide ranging of gorillas and repeated usage of a small range by chimpanzees and/or to avoidance of inter-specific contact by chimpanzees. The different staple foods (leaves and bark for gorillas and fig fruits for chimpanzees) characterize the dietary divergence between them in the montane forest of Kahuzi, where fruit is usually scarce. Gorillas rarely fed on insects, but chimpanzees occasionally fed on bees with honey, which possibly compensate for fruit scarcity. A comparison of dietary overlap between gorillas and chimpanzees across habitats suggests that sympatry may not influence dietary overlap in fruit consumed but may stimulate behavioral divergence to reduce feeding competition between them.