Evidence for dietary niche separation based on infraorbital foramen size variation among subfossil lemurs

Dental caries in living and extinct strepsirrhines with insights into diet

Dental caries is one of the most common diseases afflicting modern humans and occurs in both living and extinct non-human primates, as well as other mammalian species. Compared to other primates, less is known about the etiology or frequency of caries among the Strepsirrhini. Given the link between caries and diet, caries frequency may be informative about the dietary ecology of a given animal. Understanding rates of caries in wild populations is also critical to assessing dental health in captive populations. Here, we examine caries frequency in a sample of 36 extant strepsirrhine species (n = 316 individuals) using odontological collections of wild-, non-captive animals housed at the American Museum of Natural History by counting the number of specimens characterized by the disease. Additionally, in the context of studying caries lesions in strepsirrhines, case studies were also conducted to test if similar lesions were found in their fossil relatives. In particular, two fossil strepsirrhine species were analyzed: the earliest Late Eocene Karanisia clarki, and the subfossil lemur Megaladapis madagascariensis. Our results suggest that caries affects 13.92% of the extant individuals we examined. The frugivorous and folivorous taxa were characterized by the highest overall frequency of caries, whereas the insectivores, gummivores, and omnivores had much lower caries frequencies. Our results suggest that caries may be common among wild populations of strepsirrhines, and in fact is more prevalent than in many catarrhines and platyrrhines. These findings have important implications for understanding caries, diet, and health in living and fossil taxa.

The sensory ecology of primate food perception, revisited

Twenty years ago, Dominy and colleagues published "The sensory ecology of primate food perception," an impactful review that brought new perspectives to understanding primate foraging adaptations. Their review synthesized information on primate senses and explored how senses informed feeding behavior. Research on primate sensory ecology has seen explosive growth in the last two decades. Here, we revisit this important topic, focusing on the numerous new discoveries and lines of innovative research. We begin by reviewing each of the five traditionally recognized senses involved in foraging: audition, olfaction, vision, touch, and taste. For each sense, we provide an overview of sensory function and comparative ecology, comment on the state of knowledge at the time of the original review, and highlight advancements and lingering gaps in knowledge. Next, we provide an outline for creative, multidisciplinary, and innovative future research programs that we anticipate will generate exciting new discoveries in the next two decades.

Evolutionary and phylogenetic insights from a nuclear genome sequence of the extinct, giant, "subfossil" koala lemur Megaladapis edwardsi

No endemic Madagascar animal with body mass >10 kg survived a relatively recent wave of extinction on the island. From morphological and isotopic analyses of skeletal "subfossil" remains we can reconstruct some of the biology and behavioral ecology of giant lemurs (primates; up to ∼160 kg) and other extraordinary Malagasy megafauna that survived into the past millennium. Yet, much about the evolutionary biology of these now-extinct species remains unknown, along with persistent phylogenetic uncertainty in some cases. Thankfully, despite the challenges of DNA preservation in tropical and subtropical environments, technical advances have enabled the recovery of ancient DNA from some Malagasy subfossil specimens. Here, we present a nuclear genome sequence (∼2× coverage) for one of the largest extinct lemurs, the koala lemur Megaladapis edwardsi (∼85 kg). To support the testing of key phylogenetic and evolutionary hypotheses, we also generated high-coverage nuclear genomes for two extant lemurs, Eulemur rufifrons and Lepilemur mustelinus, and we aligned these sequences with previously published genomes for three other extant lemurs and 47 nonlemur vertebrates. Our phylogenetic results confirm that Megaladapis is most closely related to the extant Lemuridae (typified in our analysis by E. rufifrons) to the exclusion of L. mustelinus, which contradicts morphology-based phylogenies. Our evolutionary analyses identified significant convergent evolution between M. edwardsi and an extant folivore (a colobine monkey) and an herbivore (horse) in genes encoding proteins that function in plant toxin biodegradation and nutrient absorption. These results suggest that koala lemurs were highly adapted to a leaf-based diet, which may also explain their convergent craniodental morphology with the small-bodied folivore Lepilemur.

Enamel chipping in Taï Forest cercopithecids: Implications for diet reconstruction in paleoanthropological contexts

Antemortem enamel chipping in living and fossil primates is often interpreted as evidence of hard-object feeding (i.e., 'durophagy'). Laboratory analyses of tooth fracture have modeled the theoretical diets and loading conditions that may produce such chips. Previous chipping studies of nonhuman primates tend to combine populations into species samples, despite the fact that species can vary significantly in diet across their ranges. Chipping is yet to be analyzed across population-specific species samples for which long-term dietary data are available. Here, we test the association between enamel chipping and diet in a community of cercopithecid primates inhabiting the Taï Forest, Ivory Coast. We examined fourth premolars and first molars (n = 867) from naturally deceased specimens of Cercocebus atys, Colobus polykomos, Piliocolobus badius,Procolobus verus, and three species of Cercopithecus. We found little support for a predictive relationship between enamel chipping and diet across the entire Taï monkey community. Cercocebus atys, a dedicated hard-object feeder, exhibited the highest frequencies of (1) chipped teeth and (2) chips of large size; however, the other monkey with a significant degree of granivory, Co. polykomos, exhibited the lowest chip frequency. In addition, primates with little evidence of mechanically challenging or hard-food diets-such as Cercopithecus spp., Pi. badius, and Pr. verus-evinced higher chipping frequencies than expected. The equivocal and stochastic nature of enamel chipping in the Taï monkeys suggests nondietary factors contribute significantly to chipping. A negative association between canopy preference and chipping suggests a role of exogenous particles in chip formation, whereby taxa foraging closer to the forest floor encounter more errant particulates during feeding than species foraging in higher strata. We conclude that current enamel chipping models may provide insight into the diets of fossil primates, but only in cases of extreme durophagy. Given the role of nondietary factors in chip formation, our ability to reliably reconstruct a range of diets from a gradient of chipping in fossil taxa is likely weak.

Does the primate pattern hold up? Testing the functional significance of infraorbital foramen size variation among marsupials

OBJECTIVES

The relative size of the infraorbital foramen (IOF) has been used to infer the ecology of extinct primates for several decades. Primates have relatively smaller IOFs than most other mammals, which may result from the fact that they pre-process and manipulate food with their hands rather than their muzzles. In primates, relative IOF area co-varies with diet, where insectivores and folivores have relatively smaller IOFs than frugivores. We wanted to determine whether the observed patterns associated with IOF variation hold across other orders.

MATERIALS AND METHODS

We examined how relative IOF area differs among marsupials occupying different ecological niches. Marsupials were chosen because they converge with primates in both ecology and morphology, but unlike primates, some marsupials approach and pre-process foods only with their muzzles. We measured IOF area and cranial lengths from 72 marsupial species, and behavioral feeding data were obtained from a subset of this sample (N = 20).

RESULTS

Relative IOF area did not vary significantly between substrate preferences. However, relative IOF area differed significantly by diet category (P < 0.001). Species that specialize in feeding on non-grassy leaves have significantly smaller relative IOF areas than species which primarily feed on grasses, insects, vertebrates, or some combination thereof. Behavioral analyses support that folivorous marsupials approach and remove food with the hands more often than marsupials from other dietary groups.

DISCUSSION

Results suggest that relatively small IOF area may reflect increased reliance on the hands while feeding, and that relative IOF size can be used as an indicator of feeding behavior.

Dental topography indicates ecological contraction of lemur communities

Understanding the paleoecology of extinct subfossil lemurs requires reconstruction of dietary preferences. Tooth morphology is strongly correlated with diet in living primates and is appropriate for inferring dietary ecology. Recently, dental topographic analysis has shown great promise in reconstructing diet from molar tooth form. Compared with traditionally used shearing metrics, dental topography is better suited for the extraordinary diversity of tooth form among subfossil lemurs and has been shown to be less sensitive to phylogenetic sources of shape variation. Specifically, we computed orientation patch counts rotated (OPCR) and Dirichlet normal energy (DNE) of molar teeth belonging to 14 species of subfossil lemurs and compared these values to those of an extant lemur sample. The two metrics succeeded in separating species in a manner that provides insights into both food processing and diet. We used them to examine the changes in lemur community ecology in Southern and Southwestern Madagascar that accompanied the extinction of giant lemurs. We show that the poverty of Madagascar's frugivore community is a long-standing phenomenon and that extinction of large-bodied lemurs in the South and Southwest resulted not merely in a loss of guild elements but also, most likely, in changes in the ecology of extant lemurs.

Leaf nutritional quality as a predictor of primate biomass: further evidence of an ecological anomaly within prosimian communities in Madagascar

The correlation between the biomass of forest primates and a chemical index of the average nutritional quality of leaves in tropical forests has been repeatedly documented since 1990. We tested the role played by protein : fibre on lemur biomass in a gallery forest in southern Madagascar. Plant species abundance was determined based on transect censuses. We calculated an average ratio of protein-to-fibre in leaves and an abundance-weighted ratio, i.e. the mean weighted by the basal area of tree species, to be compared with the figures available for other forest ecosystems in Madagascar and a number of anthropoid habitats. Lemur densities were evaluated through compilation of previous studies made from prior to 1975 and up until 2011 based on strip censuses and/or identification of all groups supplemented with new censuses. A high mean ratio of protein to fibre (> 0.4) supports high folivore biomass at 390 kg km−2 (reaching 630 kg km−2 in the closed-canopy forest area) compared with primate communities in other Malagasy forests (protein : fibre: < 0.5; folivore biomass: < 440 kg km−2), as predicted. However, the data corroborate the finding that the total biomass of lemur communities as well as the biomass of folivorous lemur species are low compared with those of African and Asian primate communities for a given protein : fibre ratio. Tree diversity and leaf production do not consistently explain this pattern. In contrast, the extinction of large folivorous lemurs during the past two millennia presumably allowed too little time for smaller-sized species to evolve equally effective morphological and physiological specializations for processing a large range of fibrous foods.