Dietary Specialization Research Articles

Feeding ecology of the Green-cheeked Parakeet, Pyrrhura molinae (Psittaciformes, Psittacidae), in a subtropical forest of Argentina

Although there are studies on certain aspects of the feeding ecology of several species of Neotropical parrots, there is scarce ecological information about Pyrrhura molinae – a Psittacidae species which is widely distributed in South America and abundant in the Yungas of Argentina. For two years (May 2014 to June 2016), the composition and seasonal variation in the Green-cheeked Parakeet diet in the Yungas Piedmont forest in Jujuy, Argentina were examined. Furthermore, fruiting phenology transects were established to evaluate food resource availability and the patterns of food resource used by the Green-cheeked Parakeet. In 214 food plant trees, it was found that flower and dry fruit availability was highest in the dry season, and fleshy fruit production peaked in the wet season, but these phenology patterns for aged plant species suggest that there were no significant differences in food availability. The consumption of 18 plant species was recorded, being Celtis iguanaea (30.73%) and Trema micrantha (22.01%) the most consumed species. In terms of food items, fruits were the most consumed items, followed by seeds and flowers and, to a lesser extent, nectar and leaves. Levins’ niche breadth showed varying levels of diet specialisation amongst seasons, which was narrower (B = 0.28) in the wet season, indicating specialisation in diet during this season. There was a medium overlap in parakeet diet between seasons (Morisita Index = 0.59). We did not find a statistically significant relationship between resource availability and food use, but expansion and contraction in Levins Index and variation in food items consumed throughout the year and season demonstrate high flexibility in the diet. Like other congeners, the Green-cheeked Parakeet has a flexible diet that could be adjusted to the seasonal availability of food resources. These data may contribute to the design of conservation plans for the species and its habitat.

Meta-Analysis of Salmon Trophic Ecology Reveals Spatial and Interspecies Dynamics Across the North Pacific Ocean

We examined spatial patterns in diet, trophic niche width and niche overlap for chum, pink and sockeye salmon across the North Pacific during 1959–1969. This is a baseline period before major hatchery enhancement occurred coinciding with a negative phase of the Pacific Decadal Oscillation. Large-scale (between regions) and fine-scale (within regions) spatial and interspecies differences were apparent. In the Western Subarctic, all species tended to consume zooplankton. In the Bering Sea, chum consumed zooplankton, while sockeye and pink alternated between zooplankton and micronekton. In the Gulf of Alaska/Eastern Subarctic, chum and sockeye specialized on gelatinous zooplankton and cephalopod prey, respectively, while pink consumed a mixture of zooplankton and micronekton. The highest diet overlap across the North Pacific was between pink and sockeye (46.6%), followed by chum and pink (31.8%), and chum and sockeye (30.9%). Greater diet specialization was evident in the Gulf of Alaska/Eastern Subarctic compared to the Western Pacific. Generally, species had higher niche width and overlap in areas of high prey availability, and this was particularly evident for chum salmon. In addition to the large-scale trophic patterns, our data revealed novel fine-scale spatial patterns, including latitudinal, onshore-offshore, and cross-gyre gradients. Our results showed that pink tended to be more generalist consumers, and their diets may be a better reflection of overall prey presence and abundance in the environment. Conversely, chum and sockeye tended to be more specialist consumers, and their diets may provide a better reflection of interspecies dynamics or prey availability. This study provides a baseline for comparison with current and future changes in salmon marine ecology and North Pacific ecosystems. Finally, we identify two important data gaps that need addressing, that of improved taxonomic resolution diet data for Pacific salmon and focused research on sub-mesoscale oceanographic features that may play an important role in salmon health and productivity.

Seasonal feeding plasticity can facilitate coexistence of dominant omnivores in Neotropical streams

Coexistence of ecomorphologically similar species in diverse Neotropical ecosystems has been a focus of long-term debate among ecologists and evolutionary biologists. Such coexistence can be promoted by trophic plasticity and seasonal changes in omnivorous feeding. We combined stomach content and stable isotope analyses to determine how seasonal variation in resource availability influences the consumption and assimilation of resources by two syntopic fish species, Psalidodon aff. gymnodontus and P. bifasciatus, in the Lower Iguaçu basin. We also tested the impact of seasonality on trophic niche breadth and diet overlap of these two dominant omnivores. Seasonal changes in resource availability strongly influenced the consumption and assimilation of resources by the two fish species. Both species exhibited high levels of omnivory, characterized by high diversity of allochthonous resources in the wet season. Terrestrial invertebrates were the main component of diet during this season. However, in the dry season, both species reduced their isotopic niches, indicating diet specialization. High diet overlap was observed in both seasons, but the isotopic niche overlap was smaller in the dry season. Substantial reduction in the isotopic niche of P. bifascistus and a shift toward aquatic invertebrates can facilitate coexistence during this season of resource shortage. Feeding plasticity allows omnivorous fish to adjust their trophic niches according to seasonality, promoting the exploitation of different resources during periods of greater resource diversity. This seasonal variation could be an important mechanism that contributes to the resource partitioning and coexistence of dominant omnivores in Neotropical streams.

Seasonal paleoecological records from antler collagen δ13C and δ15N

AbstractCervids living in high latitudes have evolved to thrive in ecosystems that experience dramatic seasonal changes. Understanding these seasonal adaptations is important for reconstructing cervid life histories, ecosystem dynamics, and responses in the distant and not-so-distant past to changing seasonality caused by climate change. Cervid antlers provide a rare opportunity for insight into faunal seasonal ecology, as they are grown and shed each year. Stable isotopes of carbon and nitrogen measured directly from antlers have the potential to provide seasonal dietary data for individuals. If the isotopic signals in bone and antler are controlled by the same metabolic processes, then the stable carbon and nitrogen isotope compositions of collagen (δ13CColland δ15NColl) from incrementally grown antler tissue provide time-constrained dietary signals from the spring and summer growth season. Bone, by comparison, provides an average signal over several years. The amino acid (glutamate and phenylalanine) δ15N in antlers from modern captive caribou showed similar trophic discrimination factors to earlier results for other collagenous tissues (bone, tooth dentin, and cementum). Hence, growth rate was not the primary control on the stable isotope composition of antler collagen. We applied this knowledge to assess seasonal shifts in Quaternary fossils of three Cervidae species: elk (Cervus elaphus), moose (Alces alces), and caribou (Rangifer tarandus). Paired antler–bone δ13CColland δ15NCollfrom the same individual were used to identify differences between summer and annual diet and ecology. Intra-antler isotopic variability from serially sampled antlers was used to examine seasonal dietary shifts and specialization.

Individual diet specialization drives population trophic niche responses to environmental change in a predator fish population

Isotopic niche indices are increasingly used for assessing food web responses to ecological stress. Understanding the trophic mechanisms that result in ‘smaller’ or ‘larger’ isotopic niche space limits the utility of isotopic niche-based metrics. In this study, individual-level diet patterns were quantified for a meso-predatory fish (Gobiomorphus breviceps) in two contrasting lakes, one with stable macrophyte beds and the other a filamentous green algae dominated system. Metabarcoding of gut contents and stable isotope data from 48 fish were compared to abundance and isotopic compositions of macroinvertebrate prey communities. We examined whether: i) niche contraction occurs in response to reduced basal resource breadth and, ii) trophic niche contraction is caused by individual fish transitioning from diet-specialization to diet-generalism. Isotope niche contraction within the meso-predatory fish diet reflected altered macroinvertebrate food web structure within the low-macrophyte lake and additional population-level diet patterns. Niche contraction was associated with increased diet generalism; fish had more taxa (sequenced taxa) in their diet resulting in population-level diet homogenization. Isotopic and diet taxa composition dissimilarity were positively related indicating the isotopic niche reflects diet diversity between individuals. Resource partitioning analysis within populations demonstrated that the meso-predator population diet composition exhibited a non-random distribution of prey. Diet-specialization between individuals, or lack of, determined population trophic structure suggesting that food web structure was driven by diet compartmentalization. These findings illuminate food webs respond to disturbances such as macrophyte loss and suggest observed attributes of food web structure may be scale-independent emergent properties occurred-occurring at lower levels of trophic organization.

Dietary Diversification and Specialization in Neotropical Bats Facilitated by Early Molecular Evolution.

Dietary adaptation is a major feature of phenotypic and ecological diversification, yet the genetic basis of dietary shifts is poorly understood. Among mammals, Neotropical leaf-nosed bats (family Phyllostomidae) show unmatched diversity in diet; from a putative insectivorous ancestor, phyllostomids have radiated to specialize on diverse food sources including blood, nectar, and fruit. To assess whether dietary diversification in this group was accompanied by molecular adaptations for changing metabolic demands, we sequenced 89 transcriptomes across 58 species and combined these with published data to compare ∼13,000 protein coding genes across 66 species. We tested for positive selection on focal lineages, including those inferred to have undergone dietary shifts. Unexpectedly, we found a broad signature of positive selection in the ancestral phyllostomid branch, spanning genes implicated in the metabolism of all major macronutrients, yet few positively selected genes at the inferred switch to plantivory. Branches corresponding to blood- and nectar-based diets showed selection in loci underpinning nitrogenous waste excretion and glycolysis, respectively. Intriguingly, patterns of selection in metabolism genes were mirrored by those in loci implicated in craniofacial remodeling, a trait previously linked to phyllostomid dietary specialization. Finally, we show that the null model of the widely-used branch-site test is likely to be misspecified, with the implication that the test is too conservative and probably under-reports true cases of positive selection. Our findings point to a complex picture of adaptive radiation, in which the evolution of new dietary specializations has been facilitated by early adaptations combined with the generation of new genetic variation.

Effective use of meat of meat-and-egg chicken and eggs for the production of specialized semi-finished products

Poultry meat is a full-value food product for the population. It is widely used in general and specialized diets. Thanks to the work of breeders, breeds of meat-egg chickens with high egg production and high-quality meat were bred. At the same time, the meat of meat-egg chickens is somewhat inferior in organoleptic parameters to broiler meat, which to a lesser extent allows it to be used in the production of specialized meat-based food products. The paper presents the results of research on the development and production of specialized semi-finished products for the nutrition of pregnant women, using meat of meat-egg chicken. To increase the organoleptic characteristics and nutritional value of the developed semifinished products, a new product from chicken eggs is introduced into the latter – egg coagulated melange, enriched with kelp. Kelp is a source of iodine in a bioavailable form. Calcium enrichment of the developed semi-finished products was carried out by the product of the chicken egg-shell processing - a mineral concentrator, in which calcium is in an easily digestible form.The conducted studies, the results of which are presented in this article, allowed to establish that the enrichment of functional ingredients based on chicken eggs led to an increase in the nutritional value of semi-finished products, an improvement in organoleptic indicators. The introduction of kelp in the composition of enriched melange reduced the loss of iodine. Thus, efficient processing of poultry products was carried out: meat of meat-egg chicken (processing of the shell and the egg itself).

The Three Villages of Hepatic Encephalopathy.

Hepatic encephalopathy (HE) affects numerous stakeholders from a clinical, psychosocial, and financial perspective. The multilayered impact of HE is threefold and affects different groups or, for the purpose of this commentary, villages. The first village mediates HE development, including genetics, microbiome, and disease severity. The second village consists of those affected by HE-related consequences, including the patient, caregivers, society, and medical system. The third village required to manage HE includes a multidisciplinary team of inpatient and outpatient providers, mental health experts, physical therapists, and dietary specialists. Understanding and integration of these three villages can encourage individualized care for patients and families affected by hepatic encephalopathy.

Evaluating a trait-based approach to compare natural enemy and pest communities in agroforestry vs. arable systems.

Diversified farming systems, for example those that incorporate agroforestry elements, have been proposed as a solution that could maintain and improve multiple ecosystem services. However, habitat diversification in and around arable fields has complex and inconsistent effects on invertebrate crop pests and their natural enemies. This hinders the development of policy recommendations to promote the adoption of such management strategies for the provision of natural pest control services. Here, for the first time, we conducted a trait-based approach to investigate the effect of farming system on plant, invertebrate herbivore, and invertebrate natural enemy communities. We then evaluated this approach by comparing the results to those generated using a traditional taxonomic approach. At each of three working farms, we sampled within an agroforestry field (a diverse farming system comprising alleys of arable crops separated by tree rows), and within a paired non-diversified area of the farm (arable control field). Each of 96 sample points was sampled between 8 and 10 times, yielding 393,318 invertebrate specimens from 344 taxonomic groups. Diet specialization or granivory, lack of a pupal stage, and wing traits in invertebrates, along with late flowering, short flowering duration, creeping habit, and perenniality in plants, were traits more strongly associated with agroforestry crop alleys than the arable control fields. We hypothesize that this is a result of reduced habitat disturbance and increased habitat complexity in the agroforestry system. Taxonomic richness and diversity were higher in the agroforestry crop alleys compared to the arable control fields, but these effects were stronger at lower trophic levels. However, functional trait diversity of natural enemies was significantly higher in the agroforestry crop alleys than the arable control fields, suggesting an improved level of biocontrol, which was not detected by traditional diversity metrics. Of eight key pest taxa, three were significantly suppressed in the agroforestry system, while two were more abundant, compared to the arable control fields. Trait-based approaches can provide a better mechanistic understanding of farming system effects on pests and their natural enemies, therefore we recommend their application and testing in future studies of diversified farming systems.

Global distribution and conservation of avian diet specialization

AbstractEcologically specialist species are more prone to extinction than generalist species, yet the global distribution and conservation of ecological specialism is poorly understood. Here, we show that the global distribution of avian dietary specialization is roughly congruent with overall bird species richness for resident and breeding species, as well as for non‐breeding species. However, some areas harbour a higher number of diet specialist birds than expected given overall species richness (e.g. the Amazon, Gabon and Cameroon in Central Africa, extensive parts of Indonesia and some parts of northern Eurasia, Baltic cost and Mediterranean areas for resident and breeding birds, and tropical zone and south part of subtropical zone in South America for non‐breeding birds). These areas represent hotspots of avian specialization that need to carefully be considered in conservation strategies. We found that overall, 49.6% of resident and breeding species and 45.5% of non‐breeding diet specialist species are adequately represented by the global protected area system, but that this percentage is lower for the most threatened species. Policies that modify conservation planning approaches to include measures of specialization alongside other more traditional metrics of biodiversity could improve the protection of biodiversity in the face of rapidly accelerating anthropogenic threats.

Eye fluke infection changes diet composition in juvenile European perch (Perca fluviatilis)

Intraspecific diet specialization, usually driven by resource availability, competition and predation, is common in natural populations. However, the role of parasites on diet specialization of their hosts has rarely been studied. Eye flukes can impair vision ability of their hosts and have been associated with alterations of fish feeding behavior. Here it was assessed whether European perch (Perca fluviatilis) alter their diet composition as a consequence of infection with eye flukes. Young-of-the-year (YOY) perch from temperate Lake Müggelsee (Berlin, Germany) were sampled in two years, eye flukes counted and fish diet was evaluated using both stomach content and stable isotope analyses. Perch diet was dominated by zooplankton and benthic macroinvertebrates. Both methods indicated that with increasing eye fluke infection intensity fish had a more selective diet, feeding mainly on the benthic macroinvertebrate Dikerogammarus villosus, while less intensively infected fish appeared to be generalist feeders showing no preference for any particular prey type. Our results show that infection with eye flukes can indirectly affect interaction of the host with lower trophic levels by altering the diet composition and highlight the underestimated role of parasites in food web studies.

Gluten and Autism Spectrum Disorder

An expanding body of literature is examining connections between Autism Spectrum Disorder (ASD) and dietary interventions. While a number of specialist diets have been suggested as beneficial in ASD, gluten has received particularly close attention as a potentially exacerbating factor. Reports exist suggesting a beneficial effect of the gluten-free diet (GFD) in ameliorating behavioural and intellectual problems associated with ASD, while epidemiological research has also shown a comorbidity between ASD and coeliac disease. However, both caregivers and clinicians have expressed an uncertainty of the value of people with ASD going gluten-free, and as the GFD otherwise receives considerable public attention a discussion which focuses specifically on the interaction between ASD and gluten is warranted. In this review we discuss the historical context of ASD and gluten-related studies, and expand this to include an overview of epidemiological links, hypotheses of shared pathological mechanisms, and ultimately the evidence around the use and adoption of the GFD in people with ASD.

Specialist predation covaries with colour polymorphism in tawny owls

Understanding intraspecific phenotypic variation in prey specialisation can help to predict how long-term changes in prey availability affect the viability of these phenotypes and their persistence. Generalists are favoured when the main food resources are unpredictable compared to specialists, which track the availability of the main prey and are more vulnerable to changes in the main food resource. Intraspecific heritable melanin-based colour polymorphism is considered to reflect adaptations to different environments. We studied colour morph-specific diet specialisation in a generalist predator, tawny owl (Strix aluco), during offspring food provisioning in relation to mammal prey density. We hypothesised that the grey morph, with higher fitness than the brown in Northern boreal conditions, is more specialised in mammalian prey than the brown morph, which in turn has higher fitness than the grey in the temperate zone. We found a higher diversity of prey delivered to the nest by brown fathers compared to grey ones, which also depended on the overall mammalian prey availability. Brown fathers provided proportionally fewer mammalian prey than grey in poor, but not in favourable mammal prey years. Our results suggest that the brown morph is more generalistic and reacts more strongly to variations in food supply than the grey morph, which may be a beneficial strategy in an unpredictable environment caused by environmental degradation.Significance statementDiet choice of a species may vary depending on fluctuations in the abundance of their food resource, but also within a population, there can be adaptations to use different food resources. The tawny owl exhibits a grey and a reddish-brown colour morph and is considered a generalist predator eating both mammal and bird prey. We find that the diet of the reddish-brown morph is more diverse than that of the grey. When the tawny owls’ main prey, small mammals, are abundant both colour morphs prey on mammals, but in years with less small mammals, the reddish-brown morph is more prone of switching to small bird predation than the grey. The generalist strategy of the brown morph is likely to be more favourable than a stricter specialisation in small mammals of the grey under recently reoccurring irregularities in small mammal dynamics.

Digging Deeper into the Ecology of Subterranean Ants: Diversity and Niche Partitioning across Two Continents

Soil fauna is generally understudied compared to above-ground arthropods, and ants are no exception. Here, we compared a primary and a secondary forest each on two continents using four different sampling methods. Winkler sampling, pitfalls, and four types of above- and below-ground baits (dead, crushed insects; melezitose; living termites; living mealworms/grasshoppers) were applied on four plots (4 × 4 grid points) on each site. Although less diverse than Winkler samples and pitfalls, subterranean baits provided a remarkable ant community. Our baiting system provided a large dataset to systematically quantify strata and dietary specialisation in tropical rainforest ants. Compared to above-ground baits, 10–28% of the species at subterranean baits were overall more common (or unique to) below ground, indicating a fauna that was truly specialised to this stratum. Species turnover was particularly high in the primary forests, both concerning above-ground and subterranean baits and between grid points within a site. This suggests that secondary forests are more impoverished, especially concerning their subterranean fauna. Although subterranean ants rarely displayed specific preferences for a bait type, they were in general more specialised than above-ground ants; this was true for entire communities, but also for the same species if they foraged in both strata.

Age- and sex-related dietary specialization facilitate seasonal resource partitioning in a migratory shorebird.

Dietary specialization is common in animals and has important implications for individual fitness, inter‐ and intraspecific competition, and the adaptive potential of a species. Diet composition can be influenced by age‐ and sex‐related factors including an individual's morphology, social status, and acquired skills; however, specialization may only be necessary when competition is intensified by high population densities or increased energetic demands.To better understand the role of age‐ and sex‐related dietary specialization in facilitating seasonal resource partitioning, we inferred the contribution of biofilm, microphytobenthos, and benthic invertebrates to the diets of western sandpipers (Calidris mauri) from different demographic groups during mid‐winter (January/February) and at the onset of the breeding migration (April) using stable isotope mixing models. Western sandpipers are sexually dimorphic with females having significantly greater body mass and bill length than males.Diet composition differed between seasons and among demographic groups. In winter, prey consumption was similar among demographic groups, but, in spring, diet composition differed with bill length and body mass explaining 31% of the total variation in diet composition. Epifaunal invertebrates made up a greater proportion of the diet in males which had lesser mass and shorter bills than females. Consumption of Polychaeta increased with increasing bill length and was greatest in adult females. In contrast, consumption of microphytobenthos, thought to be an important food source for migrating sandpipers, increased with decreasing bill length and was greatest in juvenile males.Our results provide the first evidence that age‐ and sex‐related dietary specialization in western sandpipers facilitate seasonal resource partitioning that could reduce competition during spring at the onset of the breeding migration.Our study underscores the importance of examining resource partitioning throughout the annual cycle to inform fitness and demographic models and facilitate conservation efforts.

A window to the world of global insect declines: Moth biodiversity trends are complex and heterogeneous

Moths are the most taxonomically and ecologically diverse insect taxon for which there exist considerable time-series abundance data. There is an alarming record of decreases in moth abundance and diversity from across Europe, with rates varying markedly among and within regions. Recent reports from Costa Rica reveal steep cross-lineage declines of caterpillars, while other sites (Ecuador and Arizona, reported here) show no or only modest long-term decreases over the past two decades. Rates of decline for dietary and ecological specialists are steeper than those for ecologically generalized taxa. Additional traits commonly associated with elevated risks include large wingspans, small geographic ranges, low dispersal ability, and univoltinism; taxa associated with grasslands, aridlands, and nutrient-poor habitats also appear to be at higher risk. In temperate areas, many moth taxa limited historically by abiotic factors are increasing in abundance and range. We regard the most important continental-scale stressors to include reductions in habitat quality and quantity resulting from land-use change and climate change and, to a lesser extent, atmospheric nitrification and introduced species. Site-specific stressors include pesticide use and light pollution. Our assessment of global macrolepidopteran population trends includes numerous cases of both region-wide and local losses and studies that report no declines. Spatial variation of reported losses suggests that multiple stressors are in play. With the exception of recent reports from Costa Rica, the most severe examples of moth declines are from Northern Hemisphere regions of high human-population density and intensive agriculture.

The diversity and function of intestinal microorganisms in four geographic Cephalcia chuxiongica (a pine defoliator) populations

AbstractSymbiotic microbiomes play important roles in hosts’ adaptation and evolution. Here, the gut bacterial communities in Cephalcia chuxiongica, a key pest of pines in China, were studied for the first time by using 16S rRNA amplicon sequencing. The composition of gut bacterial communities differed in different C. chuxiongica geographic populations but interestingly, the phylogeny and diversity of gut microbiota correlated with host geographic/genetic distance, that is the microbiota was more similar as the geographic/genetic distance decreased, and vice versa. The various microbes performed similar functions and showed functional complementation, in which most of identified KEGG pathways were shared by different populations with metabolism being the most dominant functional pathway and the function of major microbes associated with host dietary specialization (pine needles), such as cellulose degradation. In addition, some microbes also associated with host biological characteristics, such as Wolbachia with parthenogenesis and Serratia with the long‐term larval diapause in C. chuxiongica. Therefore, the synergy of environmental and host factors shapes the structure of gut microbiota and gut microbiota play essential roles in host physiology and adaptation, suggesting some kind of symbiosis and coevolution. These results demonstrate the important contribution of gut microbiota and provide a sound foundation for developing control strategies for this pest.

Evolutionary insights into the eco-phenotypic diversification of Dysdera spiders in the Canary Islands

The spiders of the genus Dysdera are renowned for including woodlouse specialists. In the Canary Islands, Dysdera underwent remarkable local diversification, and 48 endemic species have been reported to date. We aim to disentangle the evolutionary history underpinning this diversity, with particular emphasis on the evolution of the trophic ecology. We collected specimens belonging to 17 Dysdera species along with the co-occurring potential prey. We performed prey capture experiments with these specimens to assess which species accepted woodlice as prey and how they captured them and used statistical extrapolation and published phylogenetic information to infer the evolution of these dietary and behavioral traits. We identified four capture tactics and trait reconstruction analyses that inferred oniscophagy as the ancestral state. We found several instances of polyphagy that evolved from trophic specialist ancestors. When including the trophic strategy, predatory behavior, body size, and habitat type, it was revealed that at all sites, the co-occurring Dysdera species differed by at least one trait, suggesting the role of adaptive radiation via character displacement. We hypothesize that the colonization of the newly emerged islands by the Dysdera species was probably followed by the recurrent evolution of both woodlice specialists and non-oniscophagous species. The radiation of Dysdera in the Canary Islands indicates that diet specialization can evolve to polyphagy.

Evolution of tooth crown shape in Mesozoic birds, and its adaptive significance with respect to diet

Both the evolution of tooth morphology and the relationship between dental features and diet in toothed birds have long been studied. Here we quantify variation in tooth crown shape in 28 key Mesozoic bird species, and examine differences in dental morphology among birds belonging to different taxonomic groupings and inferred to have had different diets. Using geometric morphometric methods (GMM) and phylogenetic comparative methods (PCM), we found few clear differences in tooth crown shape between different taxonomic and ecological categories, and our analysis provides little support for many dietary inferences drawn in previous studies. However, the Solnhofen Archaeopteryx, Jeholornis, Protopteryx, Pengornis, Longipteryx, Tianyuornis, Mengciusornis, Ichthyornis and Hesperornis all were found to possess relatively specialized tooth crown shapes, perhaps reflecting specialized diets such as insectivory, granivory, piscivory and consumption of soft-shelled arthropods. Similarity in tooth crown shape across many Mesozoic birds may indicate the lack of dietary specialization, and the association between tooth form and diet may have been weakened in any case by ‘functional replacement’ of the dentition by a horny beak and, in many cases, gastroliths.

Mammal species occupy different climates following the expansion of human impacts

Cities and agricultural fields encroach on the most fertile, habitable terrestrial landscapes, fundamentally altering global ecosystems. Today, 75% of terrestrial ecosystems are considerably altered by human activities, and landscape transformation continues to accelerate. Human impacts are one of the major drivers of the current biodiversity crisis, and they have had unprecedented consequences on ecosystem function and rates of species extinctions for thousands of years. Here we use the fossil record to investigate whether changes in geographic range that could result from human impacts have altered the climatic niches of 46 species covering six mammal orders within the contiguous United States. Sixty-seven percent of the studied mammals have significantly different climatic niches today than they did before the onset of the Industrial Revolution. Niches changed the most in the portions of the range that overlap with human-impacted landscapes. Whether by forcible elimination/introduction or more indirect means, large-bodied dietary specialists have been extirpated from climatic envelopes that characterize human-impacted areas, whereas smaller, generalist mammals have been facilitated, colonizing these same areas of the climatic space. Importantly, the climates where we find mammals today do not necessarily represent their past habitats. Without mitigation, as we move further into the Anthropocene, we can anticipate a low standing biodiversity dominated by small, generalist mammals.