Unexpected Diversity of Feeding Modes among Chisel-Mouthed Ethiopian Labeobarbus (Cyprinidae)

Trophic resource partitioning is one of the main drivers of adaptive radiation. The evolutionary diversification of large African barbs, the genus Labeobarbus, seems to be related to mouth polymorphism. The chisel-mouthed or scraping phenotype has repeatedly evolved within Labeobarbus. At least five ecomorphs with a scraping mouth morphology were detected in the waters of the Ethiopian Highlands and can be provisionally classified into two groups: (i) “Varicorhinus”-like, and (ii) “Smiling”-like. Previously, all Labeobarbus with a scraping-mouth morphology were considered to be periphyton feeders. Using data on morphology, diet and stable isotope ratios (C and N), we addressed the question: does a scraping-mouth morphology predict feeding on periphyton? Our study revealed that five scraper ecomorphs exhibited three main feeding modes: (i) periphyton-eating, (ii) herbivory–detritivory, and (iii) insectivory. Two cases of the parallel divergence of sympatric ecomorphs with distinct feeding modes (herbivory–detritivory vs. insectivory) were revealed in two geographically isolated basins. A significant difference in δ15N values was detected among sympatric scraper ecomorphs. A periphytonophagous scraper was rich in δ15N values that are comparable with those in sympatric piscivorous fish. This data sheds light on the possibility of the utilization of periphyton as a protein-rich food by fishes.

Dung Beetle Assemblages Attracted to Cow and Horse Dung: The Importance of Mouthpart Traits, Body Size, and Nesting Behavior in the Community Assembly Process

Dung beetles use excrement for feeding and reproductive purposes. Although they use a range of dung types, there have been several reports of dung beetles showing a preference for certain feces. However, exactly what determines dung preference in dung beetles remains controversial. In the present study, we investigated differences in dung beetle communities attracted to horse or cow dung from a functional diversity standpoint. Specifically, by examining 18 functional traits, we sought to understand if the dung beetle assembly process is mediated by particular traits in different dung types. Species specific dung preferences were recorded for eight species, two of which prefer horse dung and six of which prefer cow dung. Significant differences were found between the functional traits of the mouthparts of the dung beetles attracted to horse dung and those that were attracted to cow dung. Specifically, zygum development and the percentage of the molar area and the conjunctive area differed between horse and cow dung colonizing beetles. We propose that the quantitative differences in the mouthpart traits of the species attracted to horse and cow dung respectively could be related to the differential capacity of the beetles to filtrate and concentrate small particles from the dung. Hence, the dung preference of dung beetles could be related to their ability to exploit a specific dung type, which varies according to their mouthpart traits. Moreover, we found that larger and nester beetles preferred cow dung, whereas smaller and non-nester beetles preferred horse dung. This finding could be related to the tradeoff between fitness and parental investments, and to the suitability of the trophic resource according to the season and species phenology.

Relationships between biodiversity and ecosystem functioning proxies strengthen when approaching chemosynthetic deep-sea methane seeps

As biodiversity loss accelerates globally, understanding environmental influence over biodiversity–ecosystem functioning (BEF) relationships becomes crucial for ecosystem management. Theory suggests that resource supply affects the shape of BEF relationships, but this awaits detailed investigation in marine ecosystems. Here, we use deep-sea chemosynthetic methane seeps and surrounding sediments as natural laboratories in which to contrast relationships between BEF proxies along with a gradient of trophic resource availability (higher resource methane seep, to lower resource photosynthetically fuelled deep-sea habitats). We determined sediment fauna taxonomic and functional trait biodiversity, and quantified bioturbation potential (BPc), calcification degree, standing stock and density as ecosystem functioning proxies. Relationships were strongly unimodal in chemosynthetic seep habitats, but were undetectable in transitional ‘chemotone’ habitats and photosynthetically dependent deep-sea habitats. In seep habitats, ecosystem functioning proxies peaked below maximum biodiversity, perhaps suggesting that a small number of specialized species are important in shaping this relationship. This suggests that absolute biodiversity is not a good metric of ecosystem ‘value’ at methane seeps, and that these deep-sea environments may require special management to maintain ecosystem functioning under human disturbance. We promote further investigation of BEF relationships in non-traditional resource environments and emphasize that deep-sea conservation should consider ‘functioning hotspots' alongside biodiversity hotspots.

Trophic ecology of syntopic anurans of tropical stream communities

We investigated trophic resource partitioning in seven syntopic anurans from low- and mid-elevation stream habitats of a tropical riparian ecosystem by utilising stomach content analysis (SCA) and stable isotope analysis (SIA). Our SCA data revealed dietary similarities, narrow trophic niche breadth, and low dietary niche overlap in Ansonia muelleri, Limnonectes magnus, Occidozyga laevis, Megophrys stejnegeri, Pulchrana grandocula, Sanguirana mearnsi, and Staurois natator which could be attributed to these anurans’ selection of available local prey items. We confirmed ant-specialisation (myrmecophagy) of the Mindanao island endemic bufonid A. muelleri based on our temporal SCA dietary data. Our SIA estimates of assimilation of potential prey sources confirmed that L. magnus, P. grandocula, and O. laevis are generalist predators, opportunistically feeding on locally abundant insect prey items. This study on trophic resource partitioning in syntopic anurans provides the first picture of trophic interactions, i.e., predation and competition in stream communities in tropical riparian zones of a watershed ecosystem in northeast Mindanao of the southern Philippines.

Vector of Trophic Resource Partitioning in the Variability of Individuals of the Generalized form of the Large African Barbs of the Barbus (= Labeobarbus) Intermedius Complex, Ethiopia, Tana, Langano and Awasa Lakes

Analysis of the diversification of barbs of the generalized form of the Barbus (= Labeobarbus) intermedius complex in the monomorphic populations of Langano and Awasa lakes and in the polymorphic population of Lake Tana makes it possible to reveal parameters of the variability that is directed to trophic resource partitioning. The great similarity of the parameters revealed in the three studied water bodies shows that in monomorphic populations the structure of variability directed to trophic resource partitioning is identical to that in the polymorphic population. The concept of “vector of trophic resource partitioning” is introduced. In the polymorphic population, this vector makes the main contribution to the diversification of individuals, while its importance is secondary in monomorphic populations. It is concluded that the different evolutionary potential of polymorphic and monomorphic populations is determined by the specific weight of diversification caused by the vector of trophic resource partitioning. The original method of data analysis used in the study may be promising for studying similar situations in other systematic groups.

One more avenue for whale-watching contributions to science: the study of cetacean-cephalopod interactions

Cephalopods are the primary source of food for several species of odontocetes. The unstable nature of this trophic resource is likely to affect the ecology of their cetacean predators, and this can be reflected on their conservation status but also on the tourist activities which target the observation of these animals. However, the study of the cetacean-cephalopod interaction is limited by the heavy logistics and expense of dedicated scientific campaigns. Fortunately, this gap can be filled by coupling modern molecular tools with indirect sampling methods. In this note we test if whale watching activities, which represent an intense observation effort worldwide, could be a source of material for studies of cetacean-cephalopod interactions. All contacted companies welcomed the invitation and received the sampling kit. Nine samples were collected, most of them in close association with sperm whales. All samples were determined as the seven-arm octopus Haliphron atlanticus (Octopoda, Alloposidae). We conclude that, although the Azores may have particularly favorable conditions for participatory science, similar programs can be replicated elsewhere

Partitioning of trophic resource on example of the rodent community dwelling in the high mountain zone of the Eastern Caucasus

Quantitative and qualitative feeding characteristics of some rodent species co-living in the high mountain zone of the Eastern Caucasus (Republic of Daghestan) were investigated. The diet of S. uralensis consisted of 23 plant species, C. gud – 22 plant species, M. arvalis – 27 plant species, C. migtatorius – 26 plant species and D. nitedula – 19 plant species. The largest dietary breadths were M. arvalis and C. migtatorius and the least was S. uralensis. In spring, Carex spp. predominated in the diets of rodent species; in summer, the diets consisted mainly of cereals, and the autumn rodents diets consisted mainly of forbs and legumes. The maximum values of the dietary niches overlapping were found in pairs of the following species: S. uralensis C. gud, C. gud - C. migtatorius, M. arvalis C. migtatorius. Average values of the dietary niches overlapping for all rodents were 0.529, 0.277, 0.459, respectively, in spring, summer and autumn.