Sébastien Couette

CONSTRUCTING, BOOTSTRAPPING, AND COMPARING MORPHOMETRIC AND PHYLOGENETIC TREES: A CASE STUDY OF NEW WORLD MONKEYS (PLATYRRHINI, PRIMATES)

Abstract Morphometric data sets are often phenetically analyzed by using various kinds of spatial, metric, or nonmetric multivariate analyses. Such methods produce results that are difficult to compare directly with molecular or morphological phylogenetic hypotheses, which are usually expressed by using nonspatial tree representations. Therefore, it is useful in a comparative approach to analyze, and above all to visualize, morphometric pairwise relationships as tree structures. For this purpose, several additive or ultrametric methods exist, which often return different topologies for the same data set. Objective criteria are thus needed to identify the tree-building algorithm (or algorithm family) best adapted to the nature and structure of the hierarchical signal under study. Here, we present our 4-step analysis protocol that allows the construction of a morphometric tree, statistically tested for confidence, to perform direct comparisons with a phylogenetic hypothesis. As an example, we apply this protocol to the analysis of an original morphometric data set (geometric 3-dimensional Procrustes analysis of skull morphology) involving 7 species of Callithrichinae, and then compare the resulting tree to a published molecular phylogenetic hypothesis. Differences between the 2 compared trees are qualitatively and quantitatively described, and are interpreted as the result of morphological convergences due to environmental conditions, and especially to morphofunctional constraints linked to diet.

Morphology of Howler Monkeys: A Review and Quantitative Analyses

Recognition of a particularly derived eco-behavioral strategy for the genus Alouatta has been crucial for studying and understanding its equally derived cranial and postcranial morphology. The unique architecture of the skull and mandible has very likely evolved in relation to both masticatory correlates associated with an increasingly folivorous diet as well as the use of vocal communication associated with social behavior and an energy-minimizing strategy. Comparisons of cranial morphology using three-dimensional geometric morphometrics have highlighted significant interspecific shape differences. Alouatta seniculus is the most divergent in both cranial and hyoid morphology and exhibits the most pronounced levels of sexual dimorphism in those areas. Cranial variability is expressed in facial prognathism and airorhynchy, basicranial flexure, and zygomatic height. Inter- and intraspecific differences based on these axes of variation are very likely linked to interspecific variations in diet, behavior, and life history. This is further evident in the dental anatomy of the genus, indicating adaptations to a shift to a more folivorous diet. In addition, recent studies provide further evidence for significant inter- and intraspecific variations in hyoid size and shape. Alouatta seniculus possesses the largest and most inflated hyoid bulla, and the species that occupy distributional extremes (A. palliata, A. caraya) are differentiated by highly distinct hyoid shapes. These data indicate a complex relationship between morphology and behavior, with possible biogeographic implications. In terms of postcranial morphology, the forelimb bears a mixture of features that favor quadrupedalism with restricted abduction and overhead extension, providing stable contact and support along branches. In contrast, the hind limb appears to allow for a wider range of movement in all joints, with an emphasis on thigh extension and abduction, leg rotation, and powerful grasping with a habitually inverted foot. Interspecific variation reveals traits that can be ultimately related to subtle differences in the frequency of use of different positional modes, associated with variable eco-social factors. These results, deriving from different anatomical regions, provide evidence for understanding morphological variation across howler species in terms of morphofunctional adaptations, environmental pressure, and niche partitioning.

Degree of terrestrial activity of the elusive sun-tailed monkey (Cercopithecus solatus) in Gabon: Comparative study of behavior and postcranial morphometric data.

We carried out a multidisciplinary study linking behavioral and morphological data from a little‐known guenon species, Cercopithecus solatus, endemic to Gabon. Over a period of 9 months, we documented the pattern of stratum use associated with postural and locomotor behavior by direct observation (650 hrs) of a semi‐free‐ranging breeding colony. We also conducted a morphometric analysis of the humerus and limb proportions of 90 adult specimens from 16 guenon species, including C. solatus. Field observations indicated that C. solatus monkeys spent a third of their time on the ground, similar to semi‐terrestrial guenon species. We detected two patterns of stratum use: at ground level, and in trees, at a height of 3–10 m. The monkeys spent more time on the ground during the dry season than the wet season, feeding mainly at ground level, while resting, and social behaviors occurred more frequently in the tree strata. Our study of humerus size and shape, together with the analysis of limb proportions, indicated morphofunctional adaptation of C. solatus to greater terrestriality than previously thought. We therefore characterize C. solatus as a semi‐terrestrial guenon, and propose a new hypothesis for the ancestral condition. By combining behavioral and morphological results, we provide new information about the adaptive strategies of the species, and the evolutionary history of guenons, thus contributing to the conservation of the sun‐tailed monkey in the wild. Am. J. Primatol. 77:1060–1074, 2015.

Effect of temperature and social environment on worker size in the ant Temnothorax nylanderi

Warm temperatures decrease insect developmental time and body size. Social life could buffer external environmental variations, especially in large social groups, either through behavioral regulation and compensation or through specific nest architecture. Mean worker size and distribution of worker sizes within colonies are important parameters affecting colony productivity as worker size is linked to division of labor in insect societies. In this paper, we investigate the effect of stressful warm temperatures and the role of social environment (colony size and size of nestmate workers) on the mean size and size variation of laboratory-born workers in the small European ant Temnothorax nylanderi. To do so, we reared field-collected colonies under medium or warm temperature treatments after having marked the field-born workers and removed the brood except for 30 first instar larvae. Warm temperature resulted in the production of fewer workers and a higher adult mortality, confirming that this regime was stressful for the ants. T. nylanderi ants followed the temperature size rule observed in insects, with a decreased developmental time and mean size under warm condition. Social environment appeared to play an important role as we observed that (i) larger colonies buffered the effect of temperature better than smaller ones (ii) colonies with larger workers produced larger workers whatever the rearing temperature and (iii) the coefficient of variation of worker size was similar in the field and under medium laboratory temperature. This suggests that worker size variation is not primarily due to seasonal environmental fluctuations in the field. Finally, we observed a higher coefficient of variation of worker size under warm temperature. We propose that this results from a disruption of social regulation, i.e. the control of nestmate workers over developing larvae and adult worker size, under stressful conditions.

A new galago species for South Africa (Primates: Strepsirhini: Galagidae)

The primate fauna of South Africa has historically been viewed as comprising three diurnal cercopithecoid taxa — chacma baboons (Papio ursinus), vervet (Chlorocebus pygerythrus) and samango monkeys (Cercopithecus albogularis) — and two nocturnal lorisoid species — the thick-tailed greater galago (Otolemur crassicaudatus) and the southern lesser galago (Galago moholi). Here we report the positive identification of a third galago species within South Africas borders: the Mozambique dwarf galago or Grants galago, Galagoides granti (Thomas and Wroughton, 1907). The taxon was previously held to be restricted to Mozambique, eastern Zimbabwe, Malawi and Tanzania, but we have also observed it in the sand forest of Tembe Elephant Park and the Tshanini Community Reserve, near the Mozambique border. The species was formerly mistaken for Galago moholi, erroneously (we believe) extending the range of the latter species into northern KwaZulu-Natal. In South Africa the two small galagos are unlikely to have overlapping ranges: Galago moholi prefers dry savanna woodlands, whereas Galagoides granti is apparently confined to dry sand forest. However, both species may coexist with the larger and more widespread Otolemur crassicaudatus, an inhabitant of moist savanna, forest edge and thicket. The true South African ranges of both small galago species need to be ascertained.

Eocene paleoecology of Adapis parisiensis (Primate, Adapidae): From inner ear to lifestyle

European adapids, especially Adapis parisiensis, have been extensively studied over the past two centuries, essentially for taxonomic and phylogenetic purposes. Analyses of dental, cranial, and postcranial morphology have led to various hypotheses about the diet, locomotion, and lifestyle of this fossil primate species. As the morphology of Adapis parisiensis is not directly comparable to any extant species, some interpretations are still debated. The inner ear is crucial to several functional parameters, such as auditory acuity, balance, agility, orientation, and head motion speed during locomotion. We examined the inner ear morphology of Adapis parisiensis in order to make some functional inferences, using μCT techniques to access the internal morphology without damaging the fossil specimens. We analyzed the length and shape of the cochlea, the size of the oval window, and the size and orientation of the semicircular canals of seven Adapis parisiensis crania. Results indicate that the species was more sensitive to high frequencies than low frequencies. Results for locomotion style are different, depending on the method used. Results about the coefficient of agility are in good agreement with previous studies, proposing a slow/medium slow locomotion for the fossil species. In contrast, angular velocity magnitude (AVM) results show a great range of variation in the locomotor repertory for Adapis parisiensis, probably indicating that the model used is not adapted to the study of the fossil record. A comparison to measurements of extant strepsirhines leads us to conclude that Adapis parisiensis was probably monogamous and solitary, with a small home range. Anat Rec, 300:1576–1588, 2017.