Morphological-dietary relationships within two assemblages of marine demersal fishes

In this study we have used morphological characters related to feeding and prey capture and dietary data to investigate the trophic organization within two assemblages of marine demersal fishes. Morphological and dietary disparities within fish assemblages were estimated from species similarities based on Euclidean distances plus species projections on the principal axes from multivariate analyses. The analyses of the morphological variables indicated that species in each assemblage comprised morphologically distinct groups strongly influenced by trophically linked characters. Stomach content analyses revealed that fish species in each assemblage were classified into three basic feeding groups: polychaete-shrimp feeders, crab feeders and fish feeders. These results indicated that food resource partitioning was operating within each assemblage. However, when morphological and trophic data were compared no significant correlations were found. The results did not particularly support the ecomorphological hypothesis that dietary differences are due to morphological differences, since similar diets do not correspond to similar morphologies. The patterns of trophic organization within the fish assemblages examined, possibly reflect differences among species due not only to the effect of ecological demands on morphology but also by their evolutionary history and constructional constraints imposed by phylogeny. This revised version was published online in August 2006 with corrections to the Cover Date.     

Dental root size in bats with diets of different hardness

The relationship between tooth roots and diet is relatively unexplored, although a logical relationship between harder diets and increased root surface area (RSA) is suggested. This study addresses the interaction between tooth morphology, diet, and bite force in small mammals, phyllostomid bats. Using micro computed tomography (microCT), tooth root morphology of two fruit‐eating species (Carollia perspicillata and Chiroderma villosum) and two insect‐eating species (Mimon bennettii and Macrotus californicus) was compared. These species did not differ in skull or estimated body size. Food hardness, rather than dietary classification, proved to be the strongest grouping factor, with the two insectivores and the seed‐processing frugivore (C. villosum) having significantly larger RSAs. Bite force was estimated using skull measurements; bite force significantly correlated with tooth RSA but not with body size. Although the three durophagous species did exhibit larger crowns, the area of the occlusal surface did not vary among the four species. There was a linear relationship between root size and crown size, indicating that the roots were not expanded disproportionately; instead the entire tooth was larger in the hard diet species. MicroCT allows the nondestructive quantification of previously difficult‐to‐access tooth morphology; this method shows the potential for tooth roots to provide valuable dietary, behavioral, and ecological information in small mammals. J. Morphol. 276:1065–1074, 2015. © 2015 Wiley Periodicals, Inc.     

Scale‐dependent effects of forest restoration on Neotropical fruit bats

Neotropical fruit bats (family Phyllostomidae) facilitate forest regeneration on degraded lands by dispersing shrub and tree seeds. Accordingly, if fruit bats can be attracted to restoration sites, seed dispersal could be enhanced. We surveyed bat communities at 10 sites in southern Costa Rica to evaluate whether restoration treatments attracted more fruit bats if trees were planted on degraded farmlands in plantations or island configurations versus natural regeneration. We also compared the relative influence of tree cover at local and landscape spatial scales on bat abundances. We captured 68% more fruit bat individuals in tree plantations as in controls, whereas tree island plots were intermediate. Bat activity also responded to landscape tree cover within a 200‐m radius of restoration plots, with greater abundance but lower species richness in deforested landscapes. Fruit bat captures in controls and tree island plots declined with increasing landscape tree cover, but captures in plantations were relatively constant. Individual species responded differentially to tree cover measured at different spatial scales. We attribute restoration effects primarily to habitat structure rather than food resources because no planted trees produced fruits regularly eaten by bats. The magnitude of tree planting effects on fruit bats was less than previous studies have found for frugivorous birds, suggesting that bats may play a particularly important role in dispersing seeds in heavily deforested and naturally regenerating areas. Nonetheless, our results show that larger tree plantations in more intact landscapes are more likely to attract diverse fruit bats, potentially enhancing seed dispersal.     

Olfactory sensitivity to food odor components in the short-tailed fruit bat,Carollia perspicillata (phyllostomatidae,chiroptera)

Summary The absolute olfactory sensitivity in a frui-teating bat, Carollia perspicillata, was investigated. Eighteen monomolecular food odor components from 3 substance classes were tested using a sniff rate analysis method. Detection thresholds (Table 1) ranged from 3.6 · 10¹³ to 2.7 · 10¹⁰ molecules/cm³ air. Interindividual variation (N = 4) for a substance did not exceed one order of magnitude. Significant correlations between olfactory performance and carbon chain length of the odor molecule were found for two substance classes: Sensitivity to the aliphatic iso-alcohols increased linearly from C₂ to C₅, and a nonlinear correlation was found for the acetic esters, with the C₄- and C₇-forms being clearly better perceived than the other homologues. In acetic esters, the sensitivity for the n-forms of the molecule was significantly higher than for the iso-forms. No such correlation between stereo-isomers and olfactory perception was found for the n- and iso-forms of carbon acids and aliphatic alcohols. Fruit-typical odor components like ethyl butyrate (5.4 · 10¹⁰), n-pentyl acetate (2.8 · 10¹⁰), or linalool (1.8 · 10¹¹ molecules/cm³ air) were the most effective among all compounds tested, suggesting that the nutritional specialization of the bat may be associated with a specific spectrum of olfactory sensitivity.     

Dietary-morphological relationships of fishes in Liangzi Lake, China

Species in Liangzi Lake were clustered into four trophic groups: Hemiramphus kurumeus and Hemiculter bleekeri bleekeri fed predominantly on terrestrial insects; Carassius auratus auratus and Abbottina rivularis on non-animal food; Hypseleotris swinhonis, Ctenogobius giurinus, Pseudorasbora parva and Toxabramis swinhonis on cladocerans or copepods; Culterichthys erythropterus on decapod shrimps. Gut length, mouth width, mouth height, gill raker length and gill raker spacing, varied widely among species. With the exception of three species pairs ( H. swinhonis, C. giurinus; C. erythropterus, H. kurumeus; T. swinhonis, H. bleekeri bleekeri ), principal components analysis of morphological variables revealed over-dispersion of species. Canonical correspondence analysis of dietary and morphological data revealed five significant dietary-morphological correlations. The first three roots explained > 85% of the total variance. The first root reflected mainly the relationship of gut length to non-animal food, with an increase in gut length associated with an increase in non-animal food. The second root was influenced strongly by the relationship of the gill raker spacing to consumption of copepods, with an increase in gill raker spacing associated positively with copepods in the diet. The third root was influenced by the relationship of mouth gape to consumption of fish and decapod shrimps, with an increase in mouth gape associated with more fish and decapod shrimps in the diet. These significant dietary-morphological relationships supported the eco-morphological hypotheses that fish morphology influence food use, and morphological variation is important in determining ecological segregation of co-existing fish species.     

The effect of a dominant ant,Iridomyrmex purpureus,on resource use by ant assemblages depends on microhabitat and resource type

Abstract Behaviourally and ecologically dominant ants are thought to structure ant communities through their monopolization of resources. Effects of a dominant ant, Iridomyrmex purpureus, on resource use by ant communities were tested using an exclusion experiment on sandstone outcrops near Sydney, in south‐eastern Australia. The success of functionally different ants at honey and mealworm baits placed in rock and vegetation microhabitats was measured in a series of surveys before and after exclusion. I. purpureus was successfully excluded from the outcrops and patterns of resource use following I. purpureus exclusion were consistent with those of sites without I. purpureus and procedural control sites. At sites with I. purpureus, resources were discovered more rapidly, however, other ants were less successful, particularly on rock substrates. Iridomyrmex spp. were more successful on rock than in vegetation, however, in the presence of I. purpureus, the success of other Iridomyrmex on rock substrates and at honey baits was reduced. Camponotine and myrmicine ants had low success at baits and tended to be less successful in the presence of I. purpureus. In contrast, the opportunist Rhytidoponera metallica was not affected by the presence of I. purpureus and was more successful in the vegetation habitat. These findings indicate that the dominant ant affects the success of other ants at baits, particularly the ecologically similar Iridomyrmex. However, effects of I. purpureus on other taxa differ between habitats differing in complexity and resources differing in composition and defensibility.     

Assessing niche partitioning of co‐occurring sibling bat species by DNA metabarcoding

Niche partitioning through foraging is a mechanism likely involved in facilitating the coexistence of ecologically similar and co‐occurring animal species by separating their use of resources. Yet, this mechanism is not well understood in flying insectivorous animals. This is particularly true of bats, where many ecologically similar or cryptic species coexist. The detailed analysis of the foraging niche in sympatric, cryptic sibling species provides an excellent framework to disentangle the role of specific niche factors likely involved in facilitating coexistence. We used DNA metabarcoding to determine the prey species consumed by a population of sympatric sibling Rhinolophus euryale and Rhinolophus mehelyi whose use of habitat in both sympatric and allopatric ranges has been well established through radio tracking. Although some subtle dietary differences exist in prey species composition, the diet of both bats greatly overlapped (O_jk = 0.83) due to the consumption of the same common and widespread moths. Those dietary differences we did detect might be related to divergences in prey availabilities among foraging habitats, which prior radio tracking on the same population showed are differentially used and selected when both species co‐occur. This minor dietary segregation in sympatry may be the result of foraging on the same prey‐types and could contribute to reduce potential competitive interactions (e.g., for prey, acoustic space). Our results highlight the need to evaluate the spatial niche dimension in mediating the co‐occurrence of similar insectivorous bat species, a niche factor likely involved in processes of bat species coexistence.     

Co-existence and niche segregation of three small bovid species in southern Mozambique

Niche segregation among three small antelopes – red duiker, common duiker and suni – was investigated in a coastal savanna woodland/forest mosaic. It was expected that these similar‐sized concentrate selectors would show differentiation in diet choice to decrease competition. Diet composition did not vary significantly among the different vegetation types. For all three antelope species, the number of dietary items was large, with a minimum of 70 different food items per species. Dietary specialization was low, with only 10% of the food items being exclusively used by each of the species. The ranks of food items were positively correlated among species in the wet season, but not in the dry season. Diet breadth significantly decreased in the dry season. The use of exclusive species was significantly larger in the dry season with lowest values recorded for the common duiker. Diet overlap in the wet season was considerable, but significantly decreased in the dry season, the time of food scarcity. The dry season data showed evidence for niche segregation, although this was not based on displacement. As niche segregation in the dry season was coupled to a random apportionment of diet items among antelope species, it cannot be interpreted as the result of competitive displacement.     

The role of biotic interactions in shaping distributions and realised assemblages of species: implications for species distribution modelling

Predicting which species will occur together in the future, and where, remains one of the greatest challenges in ecology, and requires a sound understanding of how the abiotic and biotic environments interact with dispersal processes and history across scales. Biotic interactions and their dynamics influence species' relationships to climate, and this also has important implications for predicting future distributions of species. It is already well accepted that biotic interactions shape species' spatial distributions at local spatial extents, but the role of these interactions beyond local extents (e.g. 10 km² to global extents) are usually dismissed as unimportant. In this review we consolidate evidence for how biotic interactions shape species distributions beyond local extents and review methods for integrating biotic interactions into species distribution modelling tools. Drawing upon evidence from contemporary and palaeoecological studies of individual species ranges, functional groups, and species richness patterns, we show that biotic interactions have clearly left their mark on species distributions and realised assemblages of species across all spatial extents. We demonstrate this with examples from within and across trophic groups. A range of species distribution modelling tools is available to quantify species environmental relationships and predict species occurrence, such as: (i) integrating pairwise dependencies, (ii) using integrative predictors, and (iii) hybridising species distribution models (SDMs) with dynamic models. These methods have typically only been applied to interacting pairs of species at a single time, require a priori ecological knowledge about which species interact, and due to data paucity must assume that biotic interactions are constant in space and time. To better inform the future development of these models across spatial scales, we call for accelerated collection of spatially and temporally explicit species data. Ideally, these data should be sampled to reflect variation in the underlying environment across large spatial extents, and at fine spatial resolution. Simplified ecosystems where there are relatively few interacting species and sometimes a wealth of existing ecosystem monitoring data (e.g. arctic, alpine or island habitats) offer settings where the development of modelling tools that account for biotic interactions may be less difficult than elsewhere.     

When partitioning is not an option: Resource availability predicts intraguild interactions in two isolated Amazonian primate assemblages

Assemblage structure and acquisition of high-value resources will usually be affected by changes in resource availability and differential competitive abilities of assemblage members. In fragmented habitats where carrying capacity limits are exceeded due to high population densities and biomass, interspecific interactions can be expected to occur at a high frequency, potentially turning into an important cost for coexistence. We studied assemblage- and guild-level patterns of interspecific interactions in two highly diverse isolated primate assemblages in southern Amazonia. Specifically, we assessed the effects of temporal variation in fruit availability on the rates of interspecific interactions between gray woolly monkeys (Lagothrix lagotricha cana), one of the largest tree-dwelling mammals of the Amazon forests, and nine syntopic primate species. We found that fruit availability positively predicted rate of intraguild interactions in contrast to overall assemblage interaction rate. We did not find statistical evidence for the effect of fruit availability on the assemblage rates of type-dependent (i.e., agonistic or non-agonistic) and context-dependent (i.e., feeding or non-feeding) interactions. However, there was a clear trend toward increased feeding-related and agonistic-related interactions as fruit availability increased, with agonistic interactions mostly occurring at guild-level. These results provide support for a significant role of fruit availability in structuring spatial–temporal intraguild interactions at our study sites. Costly interspecific interactions and spatial habitat overlap can be expected to occur at a high frequency in highly diverse assemblages living in human-modified landscapes, which in turn, can have potentially negative impacts to the species involved.     

Differential diet breadths and species coexistence in leafroller-hunting eumenid wasps

There are, at least, three possible ways in which similar species coexist; resource partitioning, interference competition, and exploitation competition. Here, I investigated which way contributed to the coexistence of leafroller-hunting eumenid wasp species. Resource partitioning and, in addition, differential diet breadths proved to promote species coexistence in this case. First, I analyze the prey records and diet overlap of four eumenid species in a local area. The larger two eumenids hunted similar-sized prey items and had similar potential taxonomic prey uses. But the diet breadth of the subsocial eumenid was much wider than that of the solitary one. As a result, the diet overlap between the two large eumenids decreased. This was because the solitary eumenid attend repeatedly to the same hunting site inhabited by one abundant prey species, while the subsocial one made random hunting. On the other hand, the two medium-sized eumenids partitioned resources according to prey size. Secondly, I related these results to prey choice by several other species of eumenid obtained from literature sources. Ten Japanese common eumenids were divided into four groups according to their prey size. In each of the four groups, 2 to 3 wasp species differentiated the habitat (1 group) or coexisted by means of differential diet breadths (parallel with differential sociality, 2 groups).     

Trophic ecology of two Pithecopus species (Anura: Phyllomedusidae) living in syntopy in southern Bahia,Brazil

To coexist, two species should use available resources in different ways. These differences may happen in three different dimensions: temporal, spatial and trophic. In frogs, differences in trophic dimensions are mainly due to different sizes and types of ingested prey. We studied the diet of two syntopic Pithecopus species, addressing prey selectivity and sharing of food resources. Fieldwork was undertaken at the Michelin Ecological Reserve, southern Bahia, between the years 2011 and 2012. Stomach contents were retrieved using a flushing procedure and data on prey availability was obtained. Of the 16 invertebrate categories found in the environment, 11 were consumed by P. rohdei and 12 by P. nordestinus, features that characterize a generalist diet. The most abundant category in the diet of P. nordestinus was Diptera while Hemiptera was the most consumed prey category for P. rohdei. Trophic niche overlap was high considering the size of ingested prey and lower for categories. The selectivity index showed that both species used the resources available in the environment in a slightly different way. The differences found concerning trophic ecology of these two species seem to be sufficient to allow coexistence in the studied area.     

Compositional similarity and the distribution of geographical range size for assemblages of native and non-native species in urban floras

There is evidence that, within a region, non-native species introduced from nearby sources (extralimital native) promote homogenization and non-native species introduced from distant sources (exotic) promote differentiation of species composition. A possible explanation for these associations is that they are related to differences in the distribution of geographical range size. We test this by examining geographical ranges, delineated within a defined region, for assemblages of vascular plants in eight urban floras in the USA. Across floras, native species had the largest, least variable ranges and the greatest proportion of shared species. Exotic species had the most variable ranges with concentrations of species with small and large ranges and the lowest proportion of shared species. Extralimital natives had concentrations of species with intermediate-sized ranges and intermediate proportions of shared species. These results suggest that patterns of compositional similarity were associated with the relative strength and equality of two opposing patterns within species range size distributions: species with small vs. large ranges. In general, concentrations of species with small ranges promoted low levels and concentrations of species with large ranges promoted high levels of compositional similarity. However, patterns documented for exotic species will likely continue to develop, possibly taking on new forms, depending on how geographical distributions and the rate of introductions of exotic species change over time. Our findings also suggest that processes underlying these patterns have operated at two spatiotemporal scales. The first scale reflects historical consequences of anthropogenic activities occurring within regional extents that have promoted the introduction of extralimital natives; the second scale reflects modern consequences of anthropogenic activities operating at an increasingly global extent that have promoted the introduction of exotic species.     

Nitrogen and energy requirements of the short-tailed fruit bat (Carollia perspicillata): fruit bats are not nitrogen constrained

 Nitrogen (N) and energy (E) requirements were measured in adult Carollia perspicillata which were fed on four experimental diets. Bats ate 1.3–1.8 times their body mass ⋅ day^-1 and ingested 1339.5–1941.4 kJ ⋅ kg^-0.75 ⋅ day^-1. Despite a rapid transit time, dry matter digestibility and metabolizable E coefficient were high (83.3% and 82.4%, respectively), but true N digestibility was low (67.0%). Mass change was not correlated with E intake, indicating that bats adjusted their metabolic rate to maintain constant mass. Bats were able to maintain constant mass with digestible E intake as low as 1168.7 kJ ⋅ kg^-0.75 ⋅ day^-1 or 58.6 kJ ⋅ . Metabolic fecal N and endogenous urinary N losses were 0.87 mg N ⋅ g^-1 dry matter intake and 172.5 mg N ⋅ kg^-0.75 ⋅ day^-1, respectively, and bats required 442 mg N ⋅ kg^-0.75 ⋅ day^-1 (total nitrogen) or 292.8 mg N ⋅ kg^-0.75 ⋅ day^-1 (truly digestible nitrogen) for N balance. Based on E and N requirements and digestibilities, it was calculated that non-reproductive fruit bats were able to meet their N requirements without resorting to folivory and without over-ingesting energy. It was demonstrated that low metabolic fecal requirements allowed bats to survive on low-N diets. Accepted: 23 June 1996     

Geographical ecology of Paraguayan bats: spatial integration and metacommunity structure of interacting assemblages

We examined the relative contributions of regional spatial characteristics and local environmental conditions in determining Paraguayan bat species composition. We used a suite of full and partial redundancy analyses to estimate four additive partitions of variance in bat species composition: (a) unexplained variation, (b) that explained purely by spatial characteristics, (c) that explained purely by local environmental conditions and (d) that explained jointly by space and environment. The spatial component to bat species composition was greater than the environmental component and both pure spatial and pure environmental characteristics accounted for significant amounts of variation in bat species composition. Results from variance decomposition suggest that the mass effects model describes metacommunity structure of Paraguayan bats better than species sorting or neutral models. Such mass effects may potentially be general for bats and could explain the inability of purely local factors to fully account for bat community organization. Mass effects also have substantial conservation implications because rescue effects may enhance the persistence of mobile species in fragmented landscapes with relatively few protected sites.     

Grass greenness and grass height promote the resource partitioning among reintroduced Burchell's zebra and blue wildebeest in southern Mozambique

Differences in the selection of habitat and specific dietary items support resource partitioning and coexistence of sympatric African grazing herbivores, such as zebra and wildebeest. In Maputo Special Reserve (MSR), southern Mozambique, these two species were extirpated during the civil war (1977–1992); since 2010, they have been reintroduced into the Reserve. Identifying the resource selection by reintroduced species and how these species coexist, while utilising the same resources, is both of ecological interest and important for the management of wildlife communities and parks. This is a key application of our research. Therefore, the present study investigated resource partitioning between Burchell's zebra (Equus burchelli, Smuts 1832) and blue wildebeest (Connochaetes taurinus, Burchell 1823) in the MSR. We conducted the study from July 2016 to June 2017. The data were collected by direct observation, driving the vehicle along the reserve's roads that covered the vegetation communities where zebras and wildebeest are known to commonly occur. The composition of the diet and specific features of the grass grazed by the two species, including greenness, height, and the number of stems, were assessed. The widely available grass, Aristida barbicollis, contributed most to the diet of both herbivores. The dietary overlap between the two herbivores was higher during the dry season (95%) than wet season (86%). Resources partitioning appears to be determined, principally, by the height and greenness of the grass, with the zebra grazing taller grass, which may facilitate the access of the wildebeest to the greener, lower proportion of the forage. That results follow the expectation that, among native herbivores, overlap in resource use is not expected based on evolutionary segregation.     

Eco‐morphological attributes and feeding habits in coexisting characins

The head morphology and feeding habits of pairs of characin species (family Characidae) that coexist in four different coastal rainforest streams were analysed. Coexisting species differed in size, but were very similar in eco‐morphological attributes. Gut analyses revealed differences in feeding preferences for each coexisting species, indicating resource partitioning. A pattern of organization in species pairs that was repeated in the four studied streams was noticed. The pattern consisted of one slightly larger species with a feeding preference for items of allochthonous origin and another smaller species with a preference for autochthonous items. The hypothesis that small morphological differences enable the current coexistence of those species pairs was proposed. Furthermore, the results show ecological equivalence among different species in the studied streams.     

Reproduction and growth in three species of West African fruit bats

This study outlines the reproduction periods of the African fruit bats Epomops buettikoferi, Epomophorus garnbianus , and Micropteropus pusillus at two West African savanna sites: a wet southern Guinea savanna and a drier southern Sudanese savanna. At both sites the two annual birth periods were timed such that both lactation by only one weaning period coincided with the rainy season peaks in fruit availability. On this basis we propose that lactation rather than weaning was the important determinant of the timing of reproduction. There was no evidence of cycling of testes size in males corresponding with the seasonal mating periods. E. buettikoferi and M. pusillus females mated at six months and gave birth at the age of 12 months. Males of the two species reached puberty by 11 months and seven months, respectively. Growth rates did not differ between cohorts growing through the wet and dry season and E. buettikoferi and M. pusillus grew at rates of 276 mg/day and 116 mg/day, respectively.