An ecological comparison of two sympatric primates:Saguinus fuscicollis andCallicebus moloch of Amazonian Peru

The ecologies of two sympatric primates,Saguinus fuscicollis andCallicebus moloch, were compared during a four-month field study in southeastern Peru in order to examine the mechanisms by which these primate frugivores minimize competition for food and space.Saguinus fuscicollis andCallicebus moloch were found to differ dramatically both in diet and in use of the shared habitat. Specifically, tamarins and titis showed very little overlap in their choices of food plants or animal foods and they used distinctive foraging styles, exploiting very different parts of the habitat for animal prey. Significant interspecific differences were found in the use of particular support structures and strata within the forest, and in the density of vegetation preferred. These results suggest that resource competition between saddle-backed tamarins and dusky titis is minimal, a fact that could account for the high frequency of free association between the two species and the benign nature of these interspecific contacts.     

Fruit characters as a basis of fruit choice and seed dispersal in a tropical forest vertebrate community

Summary Interactions between a large community of vertebrate frugivore-granivores (including 7 species of large canopy birds, 19 species of rodents, 7 species of ruminants, and 6 species of monkeys), and 122 fruit species they consume, were studied for a year in a tropical rainforest in Gabon.The results show how morphological characters of fruits are involved in the choice and partitioning of the available fruit spectrum among consumer taxa. Despite an outstanding lack of specificity between fruit and consumer species, consideration of simple morphological traits of fruits reveals broad character syndromes associated with different consumer taxa. Competition between distantly related taxa that feed at the same height is far more important than has been previously supposed. The results also suggest how fruit characters could have evolved under consumer pressure as a result of consumer roles as dispersers or seed predators. Our analyses of dispersal syndromes show that fruit species partitioning occurs more between mammal taxa than between mammals and birds. There is thus a bird-monkey syndrome and a ruminant-rodent-elephant syndrome. The bird-monkey syndrome includes fruit species on which there is no pre-dispersal seed predation. These fruits (berries and drupes) are brightly colored, have a succulent pulp or arillate seeds, and no protective seed cover. The ruminant-rodent-elephant syndrome includes species for which there is pre-dispersal predation. These fruits (all drupes) are large, dull-colored, and have a dry fibrous flesh and well-protected seeds.     

Bat frugivory in two subtropical rain forests of Northern Argentina: Testing hypotheses of fruit selection in the Neotropics

Phyllostomid bats are prominent components of mammalian assemblages in the Neotropics. With many species specialized in frugivory, phyllostomids represent major partners of fleshy-fruited plants in the mutualism of seed dispersal. Here we present dietary data from two subtropical rainforests of Argentina, where fruit diversity is low and thus offer unique opportunities to test hypotheses of diet selection originally proposed for species-rich tropical assemblages. Particularly, we tested whether frugivorous phyllostomids exhibit pronounced dietary specialization in core plant taxa where fruit offer is greatly reduced as compared to tropical rainforests. We analyzed dietary overlap and niche breadth of subtropical frugivorous bats on the basis of >1000 dietary records plus >500 samples from a previous study in the region. We show that in the subtropics, frugivores from different genera remain faithful to their respective core plant taxa with few exceptions, rather than shifting toward alternative fruit resources available in the study sites. This supports predictions of specialization, which is confirmed to have a deep historical origin. The response of phyllostomid ensembles to restricted fruit diversity is at the level of species composition: absence of species for which preferred fruits do not occur in the sites. Taken together, these data lend strong support to hypotheses that explain coexistence of frugivorous phyllostomids on the basis of dietary specialization on core plant taxa with chiropterochorous fruits.     

Influence of fruit traits on the infestation of Dacus persicus in two fruit morphs of Calotropis procera

The larvae of Dacus (Leptoxyda) persicus (aak fruit fly) are key predispersal seed predators in Calotropis procera (Asclepiadaceae). Based on fruit characteristics, two morphs are distinguishable in C. procera viz., the soft-fruited morph (SF morph) and the hard-fruited morph (HF morph). The work reported here examined whether the fruit characteristics influenced the infestation by the aak fruit fly and, if so, what mechanism(s) were operative. Fruits in the SF morph were significantly more acceptable to the aak fruit fly than those of the HF morph irrespective of their size class and availability or fly population density. A general ranking of fruit acceptability for oviposition by the aak fruit fly within the fruit size class was: size class III ≥ size class II > size class I and IV. The negative relationship between fruit infestation and pericarp toughness, which is suggestive of trade-offs between the fly’s oviposition obligation and energy/time (predation risk) constraint, was found to correlate with the requirement of greater force to puncture the pericarp in the hard fruits. Lower penetrability of the pericarp in the hard fruits appeared to be primarily due to the thickness of pericarp and secondarily on account of the thickened walls of endocarpic–mesocarpic cells in the inner pericarpic layer. The present data point to the existence of two fruit morphs in C. procera differing in the acceptability of fruits for oviposition by the aak fruit fly primarily on account of toughness and internal structure of the pericarp.     

Frequencies of oral pathologies in a sample of 767 non-human primates

In this work 767 skulls of both wild caught and captive non-human primates were studied and the following characteristics were analyzed: frequency of caries and osteolytic phenomena, presence of apical or radicular cysts, degree of bone atrophy and parodontal tissue alterations, neoplasies, supernumerary teeth, and cusps. Caries and osteolytic phenomena were more frequent in captive animals because of their “anthropic” diet, while frequency of dental fractures was higher in wild primates because of their higher environmental stress. The most frequent pathologies observed in non-human primates were tartar, parodontopathies, and condylar wear, while caries and osteolytic phenomena were minimal. Condylar wear was very frequent but not very marked and possibly due to “physiological” responses and not, as in humans, to a force unbalance which occurs in masticatory dynamics of the temporomandibular joint.     

Mate choice and the genetic basis for colour variation in a polymorphic dart frog: inferences from a wild pedigree

Understanding how reproductive barriers evolve during speciation remains an important question in evolution. Divergence in mating preferences may be a common first step in this process. The striking colour pattern diversity of strawberry dart frog (Dendrobates pumilio) populations has likely been shaped by sexual selection. Previous laboratory studies have shown that females attend to male coloration and prefer to court with males of their own colour, suggesting that divergent morphs may be reproductively isolated. To test this hypothesis, we used molecular data to estimate pedigree relationships from a polymorphic population. Whereas in the laboratory both red and yellow females preferred to court with males of their own phenotype, our pedigree shows a pattern of assortative mating only for red females. In the wild, yellow females appear to be less choosy about their mates, perhaps because they incur higher costs associated with searching than females of the more common red phenotype. We also used our pedigree to investigate the genetic basis for colour-pattern variation. The phenotype frequencies we observed were consistent with those expected if dorsal background coloration is controlled by a single locus, with complete dominance of red over yellow. Our results not only help clarify the role of sexual selection in reducing gene flow, but also shed light on the mechanisms underlying colour-pattern variation among sympatric colour morphs. The difference we observed between mating preferences measured under laboratory conditions and the pattern of mate choice observed in the wild highlight the importance of field studies for understanding behavioural reproductive isolation.     

Food consumption and diet composition of the web-building spider Agelena limbata in two habitats

Summary Prey capture rate, food consumption, and diet composition of all developmental stages of the funnelweb spider Agelena limbata were estimated in woody and open habitats by a sight-count method. Prey availability was evaluated on the basis of two indices, i.e. the ratios of daily food consumption to dry weight of predator and to daily standard metabolic rate. These indices varied seasonally and between instars in this spider. Comparison of these indices between arthropod predators suggests that A. limbata live under conditions of relatively limited food supply. In the open habitat, the spiders reduced foraging activities to avoid heat stress at midday in summer because the sheet web was exposed to the direct rays of the sun and its temperature exceeded 40°C. The daily food consumption of adult spiders in the open habitat was about half of that in the woody habitat. The lower rate of energy intake of spiders in the open habitat may cause the observed smaller size of adults and lower fecundity. A. limbata captured a great range of prey comprising ten orders of arthropods and ate chemically defended insects, e.g. stink bugs, lady beetles, and ants which were rejected by many spiders. This generalistic foraging may be associated with limited and heterogeneous food supply in this spider.     

Physical and chemical properties of fruit and seeds eaten byPithecia andChiropotes in Surinam and Venezuela

Pithecia pithecia andChiropotes satanas are seed predators that eat fruits with hard pericarps. We measured resistance to puncturing and crushing of fruit and seeds eaten by these two pitheciins at two localities: in evergreen rain forest at Raleighvallen-Voltzberg, Surinam, and in tropical dry/transitional moist forest on islands in Guri Lake, Venezuela. Average measurements of pericarp hardness were similar at both sites for fruit eaten byChiropotes, but a higher maximum value was obtained at the rainforest site.Chiropotes andPithecia both ate fruits that had harder pericarps than did fruits eaten byAteles paniscus, but crushing resistances of seeds eaten were lower than values forAteles. Thus, both pitheciins selected fruits with hard pericarps and soft seeds, although there were notable intergeneric differences in hardness of fruit ingested. When fruit became scarce,Pithecia ate more flowers, whileChiropotes continued to eat fruits with hard seed coverings. Chemical analysis of species of seeds eaten byPithecia suggests that they avoided seeds with extremely high tannin levels, though they tolerated moderate tannin levels in combination with high levels of lipids. We propose that sclerocarpic harvesting (the preparation and ingestion of fruit with a hard pericarp) allows pitheciin monkeys to obtain nutritious seeds, with reduced tannins, that are softer than those ingested by other frugivores.Presented at XIIIth Congress, International Primatological Society, July 27, 1990.     

Segregation of habitat and prey in two sympatric carnivorous plant species,Drosera rotundifolia and Drosera intermedia

Summary Labelled nitrogen was used to evaluate the effects of intensive forest management on soil nitrogen transformations. The total release of N into inorganic forms (ammonium plus nitrate) was much greater than net N mineralization in all treatments. Immobilization of N by microbes was greatest in minimally-treated harvested plots, while the turnover of N within soil microbes was greatest in intensively-treated plots. Ammonium was immobilized 2.4–3.2 times more rapidly than nitrate in havested plots; nitrification in disturbed sites could thus increase the availability of N to regrowing vegetation.     

Chimpanzees' (Pan troglodytes) choice of prey among termites (macrotermitinae) in western Tanzania

This study examines factors affecting chimpanzees' preying on termites, especially their choice of prey species. Regular surveys of a large sample of termite-mounds in the Mahale Mountains, Tanzania, confirmed that chimpanzees of B Group obtainedMacrotermes, which were relatively uncommon, by the use of fishing-tools, but ignored the much more abundantOdontotermes. This preference appeared to reflectMacrotermes' more extended swarming period, greater accessibility, larger size, and less noxious taste than the soldiers ofOdontotermes. Similar factors probably underly the chimpanzees' choice ofMacrotermes at Gombe, butPseudacanthotermes spiniger are also common there, and their absence from the diet is less easily explained. In contrast, the chimpanzees of K Group at Mahale prey mainly onP. spiniger;Macrotermes are apparently absent, andP. spiniger appear to be more abundant, accessible, and palatable than the alternativeOdontotermes.     

The foraging ecology of two sympatric gobiid fishes: importance of behavior in prey type selection

Synopsis The foraging ecology of two temperate marine gobies (Pisces: Gobiidae) was studied in rocky subtidal habitats off Santa Catalina Island, California. The bluebanded goby, Lythrypnus dalli, foraged from exposed ledges and fed on planktonic and benthic prey, although planktonic prey were more important in diets by number and weight. The more cryptic zebra goby, Lythrypnus zebra, remained hidden under rocks and in crevices feeding on benthic prey almost exclusively. The active selection of particular prey taxa from the two prey sources (water column and substratum), mediated by species-specific differences in foraging behavior, resulted in interspecific differences in type, number, size and weight of prey consumed. Interspecific differences in foraging ecology reflect the selection of prey most readily available to these fishes that occupy specific and fixed microhabitats within rocky reefs.     

Specializations and limitations in the utilization of food resources by the carp,Cyprinus carpio: a study of oral food processing

Synopsis The wide variety of aquatic food is considered to be instrumental for the diversification in fish species. Yet their abilities and inabilities of handling food are poorly known. For these reasons the food processing and feeding repertoire of the adult carp, Cyprinus carpio, fed on a variety of food types, were analyzed by light and X-ray cinematography of the head parts and by electromyography of the head and body muscles during feeding. Nine stereotyped movement patterns (particulate intake, gulping, rinsing, spitting, selective retention of food, transport, crushing, grinding and deglutition) compose the feeding process, their sequence and frequency were adjusted to the type of food. Following quantitative morphological analysis at macroscopic, light- and electronmicroscopical level, the relations between the functioning and architecture of the feeding apparatus were established. The structure and dimensions of the mouth opening, the protrusible upper jaw, the slit-shaped pharyngeal cavity, the palatal and postlingual organ, the branchial sieve, the pharyngeal masticatory apparatus and the distribution of taste buds, mucous cells and muscle fibers along the oropharyngeal surface were the directive structural characters used for estimating the abilities in food processing. The specializations for utilizing food items and its limitations, derived from structural and functional data, are compared with diet data found in the literature in order to evaluate the relative position of the carp in competition for food in the aquatic environment. It is established that the ‘omnivorous’ carp is specialized in effective handling of several categories of aquatic food, even when these are mixed with non-food (bottom invertebrates <4% SL in diameter) since the palatal organ enables the carp to separate food from non-food. This includes very hard-skinned food items, processed with the powerful pharyngeal jaws of the fish, and to a lesser extent zooplankton (>250 μm). The carp is at the same time very limited in processing long and struggling prey (e.g. fish) as well as vegetable matter, due to the lack of oral teeth and the specialized morphology of its pharyngeal chewing apparatus. These feeding abilities agree with diet data from literature. The reported herbivorism of carp illustrates its opportunism in feeding behaviour. Specialization in feeding is discussed and the necessity to take into account the total series of post-capture feeding actions for a more complete view on trophic specialization. Food intake and the intra-oral food processing of carp are bound to the structures of its sensory, central processing and effector apparatus and to the plasticity in their functioning. These together determine its feeding efficiency in exploiting the available aquatic food resources. Next to ethological and ecological studies functional morphology is another important tool to explain the trophic interactions of fish.     

The use of benzyladenine in orchard fruit growing: a mini review.

Plant growth regulators (PGRs) can be well integrated into orchard production systems. Benzyladenine (BA) can be considered to be an endogenous-like compound which provides very little risk to the environment. A precondition of precocious bearing in young trees is the development of a canopy structure which has good cropping potential and this can be achieved by using BA. Fruit thinning with BA in mature trees can result in larger fruit size and increased return bloom the following year. However, the temperature dependence of the thinning response remains a problem to be resolved. The efficiency of PGRs is determined by the physiological age of trees, by the environmental conditions at application and by the application methods used.     

Hormonal regulation of ripening in the strawberry,a non-climacteric fruit

Anthocyanin accumulation is one measure of ripening in the strawberry (Fragaria ananassa Duch.), a non-climacteric fruit. Neither aminoethoxyvinylglycine, an inhibitor of 1-aminocyclopropane carboxylic acid synthase, nor inhibitors of ethylene action (silver, norbornadiene) affected anthocyanin accumulation in ripening fruit. When the achenes were removed from one half of an unripe fruit there was an accelerated accumulation of anthocyanin and induction of phenylalanine ammonia lyase on the de-achened portion of the ripening fruit. These effects of achene removal could be prevented by the application of the synthetic auxins 1-naphthaleneacetic acid or 2,4-dichlorophenoxyacetic acid to the de-achened surface. The introduction of 1-naphthalene acetic acid into intact unripe strawberry fruit through the peduncle delayed their subsequent ripening, as measured by the accumulation of anthocyanin, loss of chlorophyll and decrease in firmness. These findings suggest that the decline in the concentration of auxin in the achenes as strawberry fruit mature modulates the rate of fruit ripening.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - AVG aminoethoxyvinylglycine - NAA 1-naphthaleneacetic acid - PA1 phenylalanine ammonia-lyase - POA phenoxyacetic acid - 2,4-D 2,4-dichlorophenoxyacetic acid     

Drought stress as a mortality factor in two pairs of sympatric species of Collembola at Spitsbergen, Svalbard

Desiccation resistance was investigated experimentally in two species pairs of Collembola: Hypogastrura viatica and H. longispina, and Folsomia sexoculata and F. quadrioculata. A previous field study in Ny-Ålesund, Svalbard, showed clear habitat segregation between the species, related to two concomitant gradients of habitat cover and soil moisture. H. longispina and F. sexoculata inhabit areas with high habitat cover and soil moisture, whereas F. quadrioculata is mainly found in drier areas with high cover and H. viatica exploits the whole range of humidities/habitat cover. The desiccation experiments were aimed at testing if drought is likely to be a limiting factor for the distribution of H.?longispina and F. sexoculata. Drought was induced experimentally by testing different temperatures at a constant relative humidity. Temperature recordings from the field showed that temperatures within the range tested in the experiments occur naturally. H. longispina was highly drought sensitive compared to H. viatica, and desiccation stress probably acts as a limiting factor for its distribution in the area. F. sexoculata, was, however, much more resistant to desiccation than F. quadrioculata. For F. sexoculata, resistance to desiccation may show a trade-off in favour of tolerating a wider range of humidities, or be the result of a cuticular adaptation related to long dispersal distances and/or tolerance to submergence. For F. quadrioculata, desiccation may be an important mortality factor (but not limiting), contributing to high between-population variability in density and demography.     

Gene expression during two alternative pathways of ovary development in Pisum sativum: fruit development and ovary senescence

Pea ovaries are induced to enter a fruit development pathway involving physiological and morphological changes by pollination or application of plant growth regulators. In the absence of these stimuli, overies stop growing and enter an alternative pathway of senesecence that leads to their degeneration. We have used two dimensional polyacrylamide gel electrophoresis in search of molecular changes underlying fruit development and ovary senescence at the level of total accumulated proteins, newly synthesized proteins, and translatable, RNA populations. We have found changes in gene expression during the processes of ovary formation and ovary senescence. Stimuli that induce fruit set do not appreciably alter the overall patterns of synthesized proteins or translatable RNAs, indicating that fruit development is apparently a natural continuation of ovary formation. However, ovary senescence is an alternative pathway that involves the presence of new RNA messengers and proteins as well as the disappearance of others. These changes were detected earlier than any morphological or structural changes could be observed in the ovary.     

Chimpanzees' choices of prey between two sympatric species ofMacrotermes in the Campo Animal Reserve,Cameroon

Details are presented relating to chimpanzees' choices between two sympatric species of termites,Macrotermes lillijeborgi andM. vitrialatus, as food in the Campo Animal Reserve, southwest Cameroon, West Africa. An attempt was made to determine the various factors that affected such choices. The two species of termites seemed to have almost the same value in terms of ecological factors. However, chimpanzees fed almost exclusivelyonM. lillijeborgi, using digging sticks and fisching probes, during the study period which extended from the end of August to the middle of January, with their feeding activity showing peak at the beginning of the rainy season. By contrast,M. vitrialatus was rarely eaten in spite of the ease with which such prey could be obtained, namely, by desctruction of termite mounds by hand, without the need for tools. The reason that the chimpanzees discriminated between the two species of termite cannot be explained in terms of ecological factors such as size of prey, seasonal differences in termite activity, etc. Sticks used as tools were fairly uniform in size and character, mainly because of physical constraints related to the structure of termite mounds, and the brush-like ends of sticks seemed to be incidentaly byproducts of the chimpanzee's choice of plant species. Ecological factors could provide chimpanzees with a basis for the use of some kind of tool and help them modify it, while other factors, for example, something akin to leisure or the chimpanzee's interest in use of a tool, could provide an opportunity for inventing some tool-using behavior or for maintaining such behavior. These different factors, not being exclusive of one another, might affect the invention and maintenance of tool using-behavior at different phases. It is possible that chimpanzee's choice of prey may not always be the most efficient or appropriate in a given ecological situation.