Evolution of feeding niches in new world monkeys

Abstract

The adaptive radiation of modern New World monkeys unfolded as the major lineages diversified within different dietary-adaptive zones predicated upon a fundamentally frugivorous habit. The broad outlines of this pattern can be seen in the fossil record, beginning in the early Miocene. Cebids are obligate frugivorous predators. The smallest forms (Cebuella, Callithrix) are specialized exudativores, and the largest (cebines) are seasonally flexible omnivores, feeding particularly on insects (Saimiri) or "hard" foods, such as pith and palm nuts (Cebus), when resources are scarce. The smaller-bodied atelids (Callicebus, Aotus) may use insects or leaves opportunistically, but pitheciins (saki-uakaris) specialize on seeds as their major protein source. The larger atelines (Alouatta, Brachyteles) depend on leaves or on ripe fruit (Ateles). Locomotion, body size, and dietary adaptations are linked: claws and small body size opened the canopy-subcanopy niche to callitrichines; climbing and hanging, the fine-branch setting to the atelines; large size and strength, semiprehensile tails, and grasping thumbs, the extractive insectivory of Cebus; deliberate quadrupedalism, the energy-saving transport of folivorous Alouatta. Body size increases and decreases occurred often and in parallel within guilds and lineages. Conventional dietary categories, particularly frugivory, are inadequate for organizing the behavioral and anatomical evidence pertinent to evolutionary adaptation. Related models of morphological evolution based on feeding frequencies tend to obfuscate the selective importance of "critical functions," responses to the biomechanically challenging components of diet that may be determined by a numerically small, or seasonal, dietary fraction. For fossils, body size is an unreliable indicator of diet in the absence of detailed morphological information. More attention needs to be given to developing techniques for identifying and quantifying mechanically significant aspects of dental form, the physical properties of primate foods, their mode of access, and the cycles of availability and nutritional value.

Modeling lineage and phenotypic diversification in the New World monkey (Platyrrhini, Primates) radiation

“…Conversely, we show that the diet ecological dimension alone is not 10 enough to explain the platyrrhine body mass diversification. These outcomes support a 11 more complex scenario where platyrrhine evolution is likely related to size changes 12 among the main lineages linked to a multidimensional niche (Rosenberger, 1980(Rosenberger, , 1992. …”

“…Phenotypic 15 disparity is expected to be partitioned among subclades early in an early niche-filling 16 scenario of adaptive radiation. We also calculated the morphological disparity index 17 Body mass is proposed to be strongly related to diet among platyrrhines 23 (Rosenberger, 1980(Rosenberger, , 1992 In the BM model, body size evolves up the phylogeny via random walk and disparity 5 accumulates over time (Felsenstein, 1985). To model adaptive evolution in platyrrhine 6 size variation, we implemented seven Ornstein-Uhlenbeck models (OU; Hansen, 1997) 7 with either one, three, four or five optima.…”

“…To build the ecological models, or adaptive evolution hypotheses, we first 17 assigned each extant species to an ecological niche according to published works 18 (Rosenberger, 1992 of ecological variables and avoid multicollinearity; these PCs describe broad variation 5 in ecology (i.e., diet composition, diet quality and locomotion PCs) and were used to 6 group species in the different ecological niches (see below). It is important to remark 7 that although these niche models are based on real datasets, they are hypotheses 8 modelling the ancestral partition of platyrrhine niches.…”

“…The 11 overall fit of the models of body mass evolution to these hypothetical niches is shown in 12 Table 2. The OU model with 5 body mass optima (OU-MD5), following the 13 multivariate niche hypothesis of Rosenberger (1980Rosenberger ( , 1992, was the best supported, with 14 an Akaike weight well above the other candidate models, which performed poorly in 15 comparison. Taking into consideration the proposed phylogenetic relationships of the 16 fossils with extant clades (Rosenberger, 1992 show a slowdown in diversification rates toward present times (Fig.…”

Lost and found: The third molars of Callimico goeldii and the evolution of the callitrichine postcanine dentition

“…Assuming that Callimico evolved from an ancestor that resembled marmosets and tamarins in its An alternative to the dwarfing hypothesis was proposed by Rosenberger (1992) and 400 Spencer (1999), who both suggested that M3 loss was related to an adaptive shift involving 401 greater emphasis on food harvesting or processing using the antemolar dentition. Spencer (1999), 402 in particular, argued that when such a shift involves an increase in the mechanical advantage of 403 the jaw adductors to increase the efficiency of force production at anterior bite points, M3 404 function may in some cases be compromised, resulting it its reduction or loss.…”