The evolution of primate communities and societies in Madagascar

During their 120 to 165 million years of isolation, the flora and fauna of Madagascar evolved, to a large extent, independently of the African mainland.¹ In contrast to other oceanic islands, Madagascar is large enough to house the major components of tropical ecosystems, allowing tests of evolutionary hypotheses on the level of complete communities. Taking lemurs, the primates of Madagascar, as an example, evolutionary hypotheses correctly predict the organization of their community structure with respect to ecological correlates. Lemur social systems and their morphological correlates, on the other hand, deviate in some respects from those of other primates. Apparently, lemur social systems are influenced by several selection pressures that are weak or rare in other primates. These include variable activity patterns and avoidance of infanticide. The interspecific variation in lemur social systems therefore offers a unique opportunity for a comprehensive study of the determinants of primate social systems.     

The skeleton of early Eocene Cantius, oldest lemuriform primate

A recently discovered partial skeleton of the adapid Cantius trigonodus from the early Eocene Willwood Formation of the Bighorn Basin, Wyoming, documents substantial new information about the anatomy of the oldest lemuriform primates. It is very similar in all features to its descendant, middle Eocene Notharctus, and both exhibit numerous resemblances to certain extant Malagasy lemurs, particularly Lepilemur, Propithecus, Lemur, and Hapalemur griseus. Like these forms, Cantius had relatively long hind limbs and short forelimbs. Forelimb traits (prominent brachialis flange of the humerus, well-developed olecranon process of the ulna, and strong shafts of the ulna and radius) suggest active use of the forelimbs in progression. Specializations in the hind limb (e.g., expanded articular surface of the femoral head, narrow and elevated patellar trochlea and prominent lateral trochlear ridge, posteriorly oriented femoral and tibial condyles, narrow and elongate talus, and hallucal metatarsal with prominent peroneal tubercle) indicate capabilities for leaping and for powerful grasping with an opposable hallux. Cantius was presumably primitive in having a relatively long ischium and much more distal inferior tibial tuberosity than most extant lemurs--traits suggesting that powerful extension of the thigh and flexion at the knee were important in its locomotion and posture. We interpret Cantius as an active arboreal quadruped with a propensity for leaping. The existence of this skeletal structure in one of the oldest primates of modern aspect suggests that it represents the primitive lemuriform morphology.     

The influence of social organisation on leadership in brown lemurs (Eulemur fulvus fulvus) in a controlled environment

Studies on leadership during group movements in several lemur species showed that females were responsible for the travelling choices concerning time and direction. Interestingly, in these species females are dominant over males. We investigated the influence of social organisation upon leadership processes by studying a lemur species in which social organisation is characterized by the absence of female dominance: the brown lemur (Eulemur fulvus fulvus). The study was conducted on a semi-free ranging group of 11 individuals and the analysis performed on 69 group movements showed that all the individuals could initiate a group movement. In 34 cases, the whole group moved. There was no significant difference in the number of start attempts or in the number of group members involved from one initiator to another. Moreover, there was no effect of sex or age of the initiator on the number of individuals following it or on the speed of the joining process. Therefore, the leadership observed is widely distributed to all group members. These results support the hypothesis of an influence of social organisation upon the decision-making processes but still remain to be studied in a more relevant ecological context.     

Codominant autosomal inheritance of polymorphic red cell acid phosphatases of lemurs and some properties of the enzymes

Red cell acid phosphatase phenotypes of 207 captive animals of the genera Lemur, Hapalemur, and Propithecus were determined by starch gel electrophoresis and phosphatase-specific staining. In Lemur fulvus, three phenotypes, designated A, B, and AB, were observed. In each of the species L. catta, L. macaco, L. mongoz, and L. variegatus, a single phenotype was observed. In Hapalemur griseus, three phenotypes were found: A, B, and AB. In Propithecus verreauxi, a single phenotype was found. Examination of breeding records in conjunction with the results of the electrophoretic analyses supports the conclusion that the erythrocytic acid phosphatases in this group of nonhuman primates are the products of at least two codominant autosomal alleles. There is a wide range of specific activities of the acid phosphatases as determined by colorimetric assays. The values range from 60.6 moles of p-nitrophenol released per gram of hemoglobin per 30 min in Lemur catta to 429.1 moles in Propithecus verreauxi. The enzymes of L. fulvus and P. verreauxi were purified approximately 400-fold, and Michaelis-Menten constants were determined on the purified preparations. For L. fulvus phenotype A, K _m =0.8 mM; for L. fulvus phenotype B, K _m =0.8 mM; and for P. verreauxi, K _m =0.6 mM; the substrate in each case was p-nitrophenylphosphate.The work reported here was taken in part from a doctoral dissertation submitted by G.A.M. to the Graduate School of Duke University in partial fulfillment of the requirements for the Doctor of Philosophy degree. This work was supported by grants from the National Science Foundation (Nos. GS 39635X and BNS-74-02504), the USPHS (fellowship to G.A.M., No. GM-02007), and the Wenner-Gren Foundation (No. 2697).     

Phylogenetic Affinities Among the Extant Malagasy Lemurs (Lemuriformes) Based on Morphology and Behavior

The difficulty in achieving a consensus on the phylogenetic relationships of lemuriform primates has been due largely to the lack of a lemur fossil record and to the lack of an appropriate outgroup that would facilitate polarization of character states. Recent findings allow us to polarize some of the bony characters, but to a large extent this problem still remains. In the past, phylogenetic analyses have focused on specialized character sets such as dentition or basicranial traits, or they have employed differential weighting schemes to a more variable set of characters. In the analysis presented here, I combined all relevant characters available in the literature into one data set but restricted my selection to those traits having discontinuous states and for which no contradictory coding schemes were published. I reduced the assumptions in this analysis by removing most external weighting and ordering effects on these data sets. The available data from the literature were supplemented with data from my own observations at the Duke University Primate Center. Data were collected for 25 characters and 20 taxa and were submitted to a cladistic analysis. Some important findings from this study include support for (1) a sister-group relationship between Lepilemur and the Indridae, (2) a sister-group relationship between the Lemuridae (except Varecia) and the Indridae/Lepilemur clade, (3) a monophyletic genus Eulemur, and (4) the exclusion of Varecia from the Lemuridae.     

Surveys of sympatric lemurs at Anjamena, north-west Madagascar

In order to assess the status of lemurs along the lower reaches of the Mahavavy in north-west Madagascar, we carried out transect line sampling at Anjamena between April and August 1995. These data were complemented by additional absence–presence surveys conducted in 1994 and 1995 in many of the remaining forested areas of the region. This is the first study of lemur population density estimates for the faunal subregion between the rivers Mahavavy and Betisboka. Six sympatric lemurs are found at Anjamena: Cheirogaleus medius, Eulemur fulvus rufus, E. mongoz, Lepilemur sp., Microcebus murinus and Propithecus verreauxi coronatus. Data suggest that in some parts of the region large numbers of lemurs may still be found (E. f. rufus 121 individuals per km², E. mongoz (45), Lepilemur sp. (110), M. murinus (85) and P. v. coronatus (173)). No density data are provided for C. medius. In conclusion, as high lemur population densities may still be found and, in particular, P. v. coronatus is not known to exist in any protected area, Anjamena could serve as an important addition to the protected area system of north-west Madagascar.