Spatial and trophic niche differentiation in two sympatric lizards (Tropidurus torquatus and Cnemidophorus ocellifer) with different foraging tactics

Abstract In a ‘restinga’ habitat of southeastern Brazil, we studied the food habits and the microhabitat use of two lizards with distinct foraging modes: the tropidurid Tropidurus torquatus, a sit-and-wait predator, and the teiid Cnemidophorus ocellifer, a wide forager. The diet of the two species differed strongly, indicating a low level of similarity in their trophic niche. The sit-and-wait predator fed mainly on mobile prey, whereas the wide forager fed mainly on sedentary prey (larvae). The spatial niche breadth of T. torquatus was larger than that of C. ocellifer. Despite interspecific differences, the two species overlapped greatly in micro-habitat use. The data indicate that at Linhares the two lizard species differed more in food resources than in microhabitat, and that most of the food differences reflect the foraging patterns of the species.     

Patterns of coexistence in sexual and asexual species of Cnemidophorus lizards

Summary The lizard genus Cnemidophorus (family Teiidae) contains sexual as well as parthenogenetic species. The theoretical two-fold fitness advantage of asexuality does not translate into any obvious distributional or numerical superiority of the parthenogenic species in the southwestern US and northern Mexico where their ranges overlap. I tested the prediction that the genetically diverse sexual species should have a higher between-individual niche width than a similar sympatric asexual species by studying the prey in stomach contents of sympatric and allopatric populations of C. tigris (sexual) and C. sonorae (asexual) in southern Arizona. The expectation proved true for niche breadths based on both prey length and prey taxa categories. The within-individual component of niche breadth was not different between species. Meaningful comparisons between species in sympatry and allopatry are confounded by the uncontrolled differences in the availability and diversity of food items between sites. Before the generality of these results can be assessed the study should be repeated in other areas where sexual and asexual species are syntopic and of similar body size.     

High-throughput sequencing reveals dietary segregation in Malaysian babblers

The coexistence of numerous species within a community results from how those species use available resources. Babblers are one of the major groups of Malaysian insectivorous birds, which frequently forage in dense vegetation cover and have a high level of sympatry. Therefore, examining the diet, prey selection, and niche segregation of babblers can be challenging. In this study, we used high-throughput sequencing to investigate potential dietary overlap or segregation among 10 babbler species of the 4 genera of the family Pellorneidae and Timaliidae: Pellorneum, Malacopteron, Stachyris, and Cyanoderma in central peninsular Malaysia. We tested the hypothesis that trophically similar species may differ in resource use to avoid competitive exclusion. We identified 81 distinct arthropod taxa from fecal samples, belonging to 71 families representing 13 orders, which were predominantly from 16 dipteran, 13 lepidopteran, and 10 coleopteran families. Of all the prey taxa consumed, 45% were found to be distinct across the 10 babbler species, and ˂35% were shared simultaneously by ≥3 babbler species, indicating minimal dietary overlap. The black-throated babbler Stachyris nigricollis and moustached babbler Malacopteron magnirostre had the most generalist tendencies because they consumed a greater variety of prey taxa. Small dietary overlap values (Ojk) and a relatively wide range of food resources suggest that dietary segregation occurred among the studied babblers. The great diversity of prey consumed revealed the presence of dietary flexibility among the sympatric insectivorous birds, thus reducing any active dietary competition and facilitating the coexistence through niche partitioning.     

History and the global ecology of squamate reptiles

The structure of communities may be largely a result of evolutionary changes that occurred many millions of years ago. We explore the historical ecology of squamates (lizards and snakes), identify historically derived differences among clades, and examine how this history has affected present-day squamate assemblages globally. A dietary shift occurred in the evolutionary history of squamates. Iguanian diets contain large proportions of ants, other hymenopterans, and beetles, whereas these are minor prey in scleroglossan lizards. A preponderance of termites, grasshoppers, spiders, and insect larvae in their diets suggests that scleroglossan lizards harvest higher energy prey or avoid prey containing noxious chemicals. The success of this dietary shift is suggested by dominance of scleroglossans in lizard assemblages throughout the world. One scleroglossan clade, Autarchoglossa, combined an advanced vomeronasal chemosensory system with jaw prehension and increased activity levels. We suggest these traits provided them a competitive advantage during the day in terrestrial habitats. Iguanians and gekkotans shifted to elevated microhabitats historically, and gekkotans shifted activity to nighttime. These historically derived niche differences are apparent in extant lizard assemblages and account for some observed structure. These patterns occur in a variety of habitats at both regional and local levels throughout the world.     

Determinants of resource use in lizard assemblages from the semiarid Caatinga,Brazil

Nonsessile animals could partition the use of resources in different axes, reducing the effects of competition and allowing coexistence. Here, we investigated the spatial and trophic niche dimensions in four lizard assemblages in the Neotropical semiarid Caatinga to investigate the determinants of resource use and the extent to which lizards partition their niches. We sampled each lizard assemblage once, for 10 days, in the dry season of 2017 and 2018. In two lizard assemblages, we detected nonrandom niche overlap patterns that were higher or lower than expected by chance. The high niche overlap patterns suggest that either there is intense current competition for available microhabitats or an abundance of microhabitats. The lower niche overlap may be influenced by the presence of species adapted to sandy habitats (psammophilous), suggesting that spatial partitioning detected has historical basis, which is supported by the pPCA results and by the lack of patterns in the realized niche distribution of species across niche space. We detected trophic niche partitioning in three lizard assemblages. In one assemblage, we discovered random spatial and trophic niche overlap patterns, revealing that competition is not a determining factor in the structure of that assemblage. In fact, phylogenetic effects were predominantly the main determinants of resource use in the four studied lizard assemblages. Arid and semiarid habitats cover about one third of land surface of the world. Comparisons between our findings and those from other regions of the world may aid identify general trends in the lizard ecology of dry environments.     

Prey foraging of red titi monkeys, Callicebus cupreus, in comparison to sympatric tamarins, Saguinus mystax and Saguinus fuscicollis

We compared the prey capture strategies of red titi monkeys, Callicebus cupreus, with those of sympatric mustached, Saguinus mystax, and saddleback tamarins, Saguinus fuscicollis, to examine whether animal prey is important in niche differentiation between these Neotropical primates. We collected data on strata and substrate use during foraging, on prey searching and capturing, and on prey type of two C. cupreus groups and one group each of S. mystax and S. fuscicollis during a 5-month field study in northeastern Peruvian Amazonia. Our results showed that C. cupreus differed both from S. mystax and S. fuscicollis in prey capture strategies: (1) C. cupreus used lower forest strata for prey search and capture than S. mystax and higher forest strata than S. fuscicollis. (2) C. cupreus captured prey on a higher variety of substrates than S. mystax and more often on open microhabitats compared to S. fuscicollis. (3) C. cupreus captured prey more often directly than S. mystax and rarely by manual search, in contrast to S. fuscicollis. (4) C. cupreus fed exclusively on arthropods and focused on Hymenoptera, in contrast to both tamarin species that focused on Orthoptera and included vertebrates in their diet. These findings indicate that animal prey plays a role in niche differentiation between C. cupreus and S. fuscicollis/S. mystax and might facilitate the coexistence of these three sympatric species.     

Limitation of similarity and feeding habits in three syntopic species of newts (Triturus, Amphibia)

Differences in body size between both species and sex were observed to be close to Hutchinsonian ratios in an assemblage of three species of newts (Triturus italicus, T alpestris and T carnifex) in southern Italy According to feeding, differences in body size were not related with a strict food niche segregation The diet of larger newt included indeed all the prey eaten by smaller newts but showed new prey types Differences between species were more marked than between sexes of the same species, despite a strong sexual dimorphism in body size Larger newts foraged in a wider range of microhabitats and exhibited a greater diversity of foraging tactics Triturus italicus fed essentially on plankton and chironomids in shallow water at the banks of the pond Triturus alpestris foraged also in deeper water, particularly on lsopods in vegetation Prey fallen on the water surface constituted the main part of T carnifex diet According to recent data on newt evolution, speciation consisted in the reduction of body size Our data show that this process has been related with a specialization of the diet and of habitat use     

Niche segregation among sympatric Amazonian teiid lizards

We examined standard niche axes (time, place, and food) for three sympatric teiid lizards in the Amazon rain forest. Activity times during the day were similar among species. Ameiva ameiva were in more open microhabitats and had higher body temperatures compared with the two species of Kentropyx. Microhabitat overlaps were low and not significantly different from simulations based on Monte Carlo analysis. Grasshoppers, crickets, and spiders were important in the diets of all three species and many relatively abundant prey were infrequently eaten (e.g., ants). Dietary overlaps were most similar between the two species of Kentropyx even though microhabitat overlaps were relatively low. A Monte Carlo analysis on prey types revealed that dietary overlaps were higher at all ranks than simulated overlaps indicating that use of prey is not random. Although prey size was correlated with lizard body size, there were no species differences in adjusted prey size. A. ameiva ate more prey items at a given body size than either species of Kentropyx. Body size varies among species, with A. ameiva being the largest and K. altamazonica the smallest. The two species of Kentropyx are most distant morphologically, with A. ameiva intermediate. The most distant species morphologically are the most similar in terms of prey types. A morphological analysis including 15 species from four genera revealed patterns of covariation that reflected phylogenetic affinities (i.e., taxonomic patterns are evident). A cluster analysis revealed that A. ameiva, K. pelviceps, and K. altamazonica were in the same morphological group and that within that group, A. ameiva differed from the rest of the species. In addition, K. pelviceps and K. altamazonica were distinguishable from other species of Kentropyx based on morphology. Received: 26 December 1998 / Accepted: 15 September 1999     

Differences in stable isotope composition within and among zooplanktivorous Utaka cichlid populations from Lake Malawi

Stable isotope analysis was used to determine whether five sympatric zooplanktivorous cichlids of the Utaka assemblage from Lake Malawi vary in isotopic signature as an indication of possible differences in food resource composition. The isotopic composition of the Utaka in combination with literature data about diet composition suggests that these species exploit a narrow range of zooplanktonic prey types. At five sampling locations, significant differences in δ¹³C and δ¹⁵N were detected among species but a consistent pattern across locations was absent. Significant intraspecific differences between locations were found. These differences were relatively low in view of the large geographic distances between the populations and there was no consistent spatial pattern among the species. The observed differences may be indicative of local variations in diet composition, which may help in reducing niche overlap among these zooplanktivores.     

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.     

Ecological organization of a Chihuahuan desert lizard community

Summary Niche relationships among 11 diurnal lizard species were studied for 3 years. The community appeared to be subdivided spatially into different subsets of only four to six species. Coexisting species of each subgroup were separated further by differential utilization of microhabitats. In late spring and early summer, when food shortage is likely, dietary overlaps between syntopic species were generally low but increased broadly after the rains, when food became plentiful. Because of the high similarity in prey-size utilization among large and medium species, effects of prey selection according to size were generally slight except for very different-sized species. Overlap in the three-dimensional resource space was high between Cnemidophorus scalaris and C. tigris, but close observation of the ecology of the two populations showed many small differences between them. We suggest that the very diversified ecological opportunism of C. scalaris allows it to coexist with C. tigris in a very heterogeneous ecosystem. Several hypotheses are discussed to explain the ecological determinism of resource partitioning within such a community.     

Community-wide character displacement in New Zealand skinks

Aim  To test for community-wide character displacement in New Zealand skinks.
Location  Four small islands in the New Zealand archipelago.
Methods  (1) We conducted a field experiment on a single island to evaluate whether prey size selection is correlated with lizard body size. We pitfall trapped 69 skinks from three species, measured several aspects of their morphology and presented each animal with a variety of different-sized prey in a food choice experiment. (2) We tested whether the morphological characteristics associated with prey size selection were evenly partitioned in four island skink communities using null models.
Results  Prey size selection was associated with skink morphology; larger skinks consumed larger prey. Null model analyses showed support for evenly displaced body sizes on one island, weak support on one island and no support on two islands.
Main conclusions  Results showed mixed support for community-wide character displacement in New Zealand skinks. Differences in body sizes appear to reflect the use of different-sized prey. Even differentiation in body sizes on one island suggests that species coexistence is facilitated by interspecific differences in prey size selection. However, little support was found on other islands, suggesting that other factors, such as interspecific differences in habitat selection and/or diurnal activity patterns, may interact with differences in prey size selection to promote coexistence among New Zealand skinks.     

The foraging ecology of two pairs of congeneric demersal fish species: importance of morphological characteristics in prey selection

The feeding habits of two sympatric species pairs of demersal fish ( Mullus barbatus-Mullus surmuletus, Serranus cabrilla-Serranus hepatus ) which occupy the shallow coastal area (25–30 m) in Iraklion Bay were investigated from samples collected on a monthly basis (August 1990 to August 1992). Stomach content analyses revealed that all of them were carnivores, feeding mainly on benthic invertebrates, and that each species consumed a narrow range of prey species with no significant dietary overlap. The morphology of their feeding apparatus was compared to examine the effect of any morphological differences on food selection and resource partitioning between the fish species. The species could be distinguished on the basis of the size of their mouth gape, the number of gill rakers and the length of their intestine. This study shows that each species pair follows a different strategy segregating along food niche dimensions. In particular, M. barbatus and M. surmuletus segregate their feeding niche consuming different prey taxa with similar sizes whereas S. cabrilla and S. hepatus differ considerably with respect to the degree to which prey species contribute to their diets coupled with differences in mean prey sizes.     

Patterns of infestation by the trombiculid mite Eutrombicula alfreddugesi in four sympatric lizard species (genus Tropidurus) in northeastern Brazil

We studied the parasitism by the chigger mite Eutrombicula alfreddugesi on four sympatric lizard species of the genus Tropidurus in Morro do Chapéu, Bahia state, Brazil: T. hispidus, T. cocorobensis, T. semitaeniatus and T. erythrocephalus. For each species, we investigated the patterns of infestation and analyzed to which extent they varied among the hosts. We calculated the spatial niche breadth of the chigger mite on the body of each host species and the distribution of mites along the hosts' bodies for each Tropidurus species. All four species of Tropidurus at Morro do Chapéu were parasited by the chigger mite, with high (97-100%) prevalences. Host body size significantly explained the intensity of mite infestation for all species, except T. erythrocephalus. The body regions with highest intensity of infestation in the four lizard species were the mite pockets. The spacial niche width of the chigger varied consistently among the four lizards species studied being highest for T. erytrocephalus and lowest for T. cocorobensis. We conclude that the distribution and intensity with which lizards of the genus Tropidurus are infested by Eutrombicula alfreddugesi larvae results from the interaction between aspects of host morphology (such as body size and the occurrence and distribution of mite pockets) and ecology (especially microhabitat use).     

How equally sized piscivorous birds and fish sharing common food resources may reduce possible feeding interactions between them?

The diets of sympatric predators may overlap, especially when their body sizes are similar and foraging area is relatively small. It may be also supposed that some differences in their foraging strategies may counteract competitive interactions among them, and therefore be of advantage to these species. To reveal such phenomena the composition of food of cormorant and adult pikeperch was studied in the Dobczyce Reservoir (S Poland) from June to November 2002. The main prey species were the same and the range of prey size was similar for both piscivores. Despite these similarities, the potential for dietary overlap was strongly reduced due to two differences in their foraging patterns: (1) different preferred prey species (cormorants foraged mainly roach, whereas pikeperch selected juvenile percids); (2) different size of simultaneously selected prey (in summer, cormorants selected larger prey, while in autumn larger prey was selected by pikeperch). These differences may be explained by some general features of birds and fishes, which determine the costs to the individual of capturing prey. The observed selection of different prey species and sizes may be also important for the co-occurrence of other piscivorous birds and fishes sharing common food resources.     

Resource partitioning in sympatric langurs and macaques in tropical rainforests of the central Western Ghats, south India

In a competitive sympatric association, coexisting species may try to reduce interspecific interactions as well as competition for similar resources by several ecological and behavioral practices. We studied resource utilization of three sympatric primate species namely, lion-tailed macaques (Macaca silenus), bonnet macaques (M. radiata) and Hanuman langurs (Semnopithecus entellus) in a tropical rainforest of the central Western Ghats, south India. We studied resource use, tree-height use, foraging height, substrate use when consuming animal prey and interspecific interactions. The results revealed that across the year, there was very limited niche overlap in diet between each species-pair. Each primate species largely depended on different plant species or different plant parts and phenophases from shared plant species. Primate species used different heights for foraging, and the two macaque species searched different substrates when foraging on animal prey. We also recorded season-wise resource abundance for the resources shared by these three primate species. While there was low dietary overlap during the dry season (a period of relatively low resource abundance), there was high dietary overlap between the two macaque species during the wet season (a period of high resource abundance for the shared resources). We observed only a few interspecific interactions. None of these were agonistic, even during the period of high niche overlap. This suggests that the sympatric primate species in this region are characterized by little or no contest competition. Unlike in some other regions of the Western Ghats, the lack of interspecific feeding competition appears to allow these primates, especially the macaques, to remain sympatric year-round.     

Resource partitioning by three species of newts during their aquatic phase

This paper describes the multidimensional niche of syntopic smooth newts Triturus vulgaris. alpine newts Triturus alpestris. and Italian crested newts Triturus carnifex. which constitute a complex community of eight components (the three species and their larvae, plus juvenile and neotenic alpine newts) All the potentially limiting resources (seasonal time, diel time, habitat and food) are analyzed as single niche dimensions, and then the real multidimensional niche is calculated Resource states are objectively defined, using an algorithm that groups the significant resource categories The larvae were segregated by prey, season, habitat, and water depth, in order of decreasing importance, their overlap was very low when their complete multidimensional niche was considered, and therefore they have few opportunities for present–day competition The adults were largely segregated by season and water depth, and to a lesser degree by habitat and prey, their multidimensional niches overlapped to a certain degree, thus leaving conditions for ongoing competition Considenng all the species and the life stages together, the order of importance for segregation was season, prey, habitat, water depth and diel activity, with a low overlap in the complete niche Differences m prey size were probably due to morphological constraints, differences in diel activity had very little effect on segregation except m separating larvae from the adults, and were likely promoted by need to avoid mutual predation and cannibalism It remains to be tested whether seasonal, habitat, and water depth differences are due to competitive pressures or to ecophysiological constraints     

四川卧龙国家级自然保护区三种高山同域鸡形目鸟类的时空生态位比较

高海拔山区气候条件恶劣, 资源匮乏, 探究同域分布的近缘物种如何利用有限的资源以实现稳定共存, 对于了解高山生态系统生物多样性格局的形成和维持机制具有重要意义。鸡形目鸟类飞行能力弱, 属于典型的地栖物种, 生态位空间相对狭窄, 可能面临更高的种间竞争压力。本研究旨在比较几种同域分布的鸡形目鸟类的时空生态位, 为了解高山生态系统同域物种的共存机制提供新的研究案例。2020年4-9月, 研究人员在四川卧龙国家级自然保护区海拔3,300-4,200 m的高山区域进行了野外调查, 通过样线法和样方法对鸡形目鸟类群落优势物种绿尾虹雉(Lophophorus lhuysii)、雉鹑(Tetraophasis obscurus)和雪鹑(Lerwa lerwa)繁殖期的微生境进行调查, 使用红外相机对其活动节律进行监测, 并运用核密度估计法从微生境利用和日活动节律两个生态维度进行了种间生态位比较。结果显示, 雪鹑在微生境利用和日活动节律上均与其他两个物种存在显著差异。绿尾虹雉与雉鹑在微生境的利用上具有相似偏好; 但绿尾虹雉的早活动高峰晚于雉鹑, 晚活动高峰早于雉鹑, 表现出显著的种间日活动节律差异; 然而, 整合两个维度后, 绿尾虹雉和雉鹑的整体生态位仍然高度重叠, 没有显著分化。本研究表明高山鸡形目物种间的生态位分化体现于多个不同的生态维度, 并且不同物种之间的分化方式有所差异。在空间和时间生态位上的显著分化使雪鹑与同域物种间的竞争压力相对较小, 有利于其实现稳定共存。而绿尾虹雉与雉鹑的整体生态位高度重叠, 建议进一步对其食性开展研究, 探讨营养生态位上的潜在种间分化。     

Does whole‐organism performance constrain resource use? A community test with desert lizards

Discovering the mechanisms by which communities of co‐existing species exist has proven to be one of the greatest challenges for evolutionary ecologists. A recent perspective emphasizes the role of functional traits, such as whole‐organism performance, as key limiting factors in the evolution of communities, yet few studies have examined this possibility. We examine how bite force and morphology influence the ability of ten lizard species in a single community to access insect prey, as defined by prey type and prey hardness. We gathered over 3 years of data from a desert lizard community comprised of ten species and found significant variation among species for bite force and prey hardness, as well as significant differences in performance and niche breadth for each species. In general, higher levels of absolute bite force broadens resource accessibility (sizes of prey), and does not generally result in a reduced ability to access smaller prey. For example, large lizard species that are hard biters can still consume soft prey. On the other hand, small lizard species that are weak biters are more limited in their ability to access hard prey, although the overall decline in resource accessibility is modest. Our findings highlight how functional traits can influence which species can access key resources within a community of similar species. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, ●● , ●●–●●.     

Optimal foraging constrains macroecological patterns: body size and dietary niche breadth in lizards

Aim  To explore and identify probable mechanisms contributing to the relationships among body size, dietary niche breadth and mean, minimum, maximum and range of prey size in predaceous lizards.
Location  Our data set includes species from tropical rainforests, semi-arid regions of Brazil, and from deserts of the south-western United States, Australia and the Kalahari of Africa.
Methods  We calculated phylogenetic and non-phylogenetic regressions among predator body size, dietary breath and various prey size measures.
Results  We found a negative association between body size and dietary niche breadth in 159 lizard species sampled across most evolutionary lineages of squamate reptiles and across major continents and habitats. We also show that mean, minimum, maximum and range of prey size were positively associated with body size.
Main conclusions  Our results suggest not only that larger lizards tend to eat larger prey, but in doing so offset their use of smaller prey. Reduction of dietary niche breadth with increased body size in these lizards suggests that large predators target large and more profitable prey. Consequently, the negative association between body size and niche breadth in predators most likely results from optimal foraging. Though this result may appear paradoxical and runs counter to previous studies, resources for predators may be predictably more limited than resources for herbivores, thus driving selection for more profitable prey.