Biogeography of lemurs in the humid forests of Madagascar: the role of elevational distribution and rivers

Aim Elucidation of the influence of river systems on the distribution of lemurs. Location Humid forests of Madagascar. Methods We review the elevational distribution of Malagasy lemurs to address hypotheses of the role of rivers as physical barriers. Main conclusions Rivers are barriers for some species. However, several lemurs have altitudinal ranges that are higher than the headwaters of a given river, and in such cases these species are able to disperse across the source.     

Comparison of plant secondary metabolites and digestibility of three different boreal coniferous trees

Moose (Alces alces L.) prefer to browse Pinus sylvestris over other coniferous trees. One reason for this preference might be due to differences in the chemical composition of various coniferous plants, and/or differences in digestibility. We evaluated the in-sacco digestibility of P. sylvestris, Pinus contorta and Picea abies using a fistulated cow (Bos taurus). Additionally, we determined the chemical profile of the different plant species (with emphasis on specific phenolics) and we modified the concentration of the individual phenolic (+)catechin in plant material of P. sylvestris to test the influence of this particular phenolic on digestibility in vitro (IVDMD). The in-sacco experiment revealed the highest digestibility of dry matter, and neutral detergent fibre for P. sylvestris. In addition, the concentration of nitrogen was significantly higher, and the concentrations of total phenolics and condensed tannins were significantly lower in P. sylvestris than in the other species. Individual phenolics showed high variation but were low in P. sylvestris, whereas P. contorta and P. abies had at least one species-specific phenolic compound of high concentration each. We found no changes in the digestibility of samples in which we experimentally elevated (+)catechin content.     

Geographic Variation in Populations of Microcebus murinus in Madagascar: Resource Seasonality or Bergmann's Rule?

Gray mouse lemurs (Microcebus murinus) occur in western Madagascar from the evergreen littoral rain forests at the southern tip of the island to the seasonal dry deciduous forests of the west and northwest. The wide geographic distribution allows researchers to investigate whether ecogeographic variations reflect adaptations to ambient temperatures, as a proxy for constraints of thermoregulation, or to rainfall, as a proxy of food availability. We compared body mass, number of litters/yr, and longevity for 3 populations: 1 from the evergreen littoral rain forest of the south (Mandena: annual mean temperature 23°C, 1600 mm rain/yr), 1 from the dry deciduous forest of the west (Kirindy/CFPF: 25°C, 800 mm), and 1 from the dry deciduous forest of northwestern Madagascar (Ampijoroa: 27°C, 1200 mm). Body mass decreases with increasing ambient temperature from south to north (Mandena > Kirindy/CFPF > Ampijoroa). The number of litters/yr was highest in the littoral rain forest (2 or 3 litters/yr) and decreased with decreasing rainfall (Mandena > Ampijoroa > Kirindy/CFPF). Life expectancy is lowest in the littoral forest (13% recaptures of mouse lemurs between years) and high (ca. 30–40% recaptures between years) in the dry forests (Mandena < Kirindy/CFPF and Ampijoroa). We postulate that constraints of thermoregulation result in the latitudinal gradient of body mass. Reduced resource productivity or seasonality is reflected in differences in reproductive rates, which seemed to be traded off against longevity. Thus body mass, longevity, and reproductive parameters respond differently to ambient conditions.     

Multivariate analysis of initial orientation in homing pigeons: Is there a “preferred compass direction”?

The mean vanishing direction of homing pigeons of a given release often deviates from the home direction considerably. Any kind of geographical systematic in these deviations might give us a hint on the distribution of the information involved in the homing process. Analysis of releases arranged symmetrically around the home loft with methods of circular statistics could not resolve the pending question of site-specificity vs. directional effects in the initial orientation of homing pigeons unambiguously. In part, this ambiguity comes about by the facts that

Taxonomic Revision of Mouse Lemurs (Microcebus) in the Western Portions of Madagascar

The genus Microcebus (mouse lemurs) are the smallest extant primates. Until recently, they were considered to comprise two different species: Microcebus murinus, confined largely to dry forests on the western portion of Madagascar, and M. rufus, occurring in humid forest formations of eastern Madagascar. Specimens and recent field observations document rufous individuals in the west. However, the current taxonomy is entangled due to a lack of comparative material to quantify intrapopulation and intraspecific morphological variation. On the basis of recently collected specimens of Microcebus from 12 localities in portions of western Madagascar, from Ankarana in the north to Beza Mahafaly in the south, we present a revision using external, cranial, and dental characters. We recognize seven species of Microcebus from western Madagascar. We name and describe 3 spp., resurrect a previously synonymized species, and amend diagnoses for Microcebus murinus (J. F. Miller, 1777), M. myoxinus Peters, 1852, and M. ravelobensis Zimmermann et al., 1998.     

MHC Variability of a Small Lemur in the Littoral Forest Fragments of Southeastern Madagascar

Habitat fragmentation inhibits gene flow between populations often resulting in a loss of genetic diversity with possible negative effects on fitness parameters. In vertebrates, growing evidence suggests that such genetic diversity is particularly important at the level of the major histocompatibility complex (MHC) because its gene products play an important role in immune functions. Diversity in the MHC is assumed to improve population viability. Here, we investigated the impact of forest fragmentation on the genetic variability of one of the functionally important parts of the MHC, DRB exon 2, of the endemic mouse lemur Microcebus murinus by comparing populations inhabiting two littoral forest fragments of different size in southeastern Madagascar. Twelve different alleles of DRB exon 2 were found in 145 individuals of M. murinus with high levels of sequence divergence between alleles. In both subpopulations, levels of genetic diversity were high, and the genetic analyses revealed only limited effects of fragmentation. Significantly more non-synonymous than synonymous substitutions were found in the functionally important antigen recognition and binding sites indicating selection processes maintaining MHC polymorphism. This is the first study on MHC variation in a free-ranging Malagasy lemur population.     

Sequence identification and characterization of human carnosinase and a closely related non-specific dipeptidase

Carnosine (beta-alanyl-L-histidine) and homocarnosine (gamma-aminobutyric acid-L-histidine) are two naturally occurring dipeptides with potential neuroprotective and neurotransmitter functions in the brain. Peptidase activities degrading both carnosine and homocarnosine have been described previously, but the genes linked to these activities were unknown. Here we present the identification of two novel cDNAs named CN1 and CN2 coding for two proteins of 56.8 and 52.7 kDa and their classification as members of the M20 metalloprotease family. Whereas human CN1 mRNA and protein are brain-specific, CN2 codes for a ubiquitous protein. In contrast, expression of the mouse and rat CN1 orthologues was detectable only in kidney. The recombinant CN1 and CN2 proteins were expressed in Chinese hamster ovary cells and purified to homogeneity. CN1 was identified as a homodimeric dipeptidase with a narrow substrate specificity for Xaa-His dipeptides including those with Xaa = beta Ala (carnosine, K(m) 1.2 mM), N-methyl beta Ala, Ala, Gly, and gamma-aminobutyric acid (homocarnosine, K(m) 200 microM), an isoelectric point of pH 4.5, and maximal activity at pH 8.5. CN2 protein is a dipeptidase not limited to Xaa-His dipeptides, requires Mn(2+) for full activity, and is sensitive to inhibition by bestatin (IC(50) 7 nM). This enzyme does not degrade homocarnosine and hydrolyzes carnosine only at alkaline pH with an optimum at pH 9.5. Based on their substrate specificity and biophysical and biochemical properties CN1 was identified as human carnosinase (EC ), whereas CN2 corresponds to the cytosolic nonspecific dipeptidase (EC ).     

Tree dispersal strategies in the littoral forest of Sainte Luce (SE-Madagascar)

Zoochory is the most common mode of seed dispersal for the majority of plant species in the tropics. Based on the assumption of tight plant-animal interactions several hypotheses have been developed to investigate the origin of life history traits of plant diaspores and their dispersers, such as species-specific co-evolution, the low/high investment model (low investment in single fruits but massive fruiting to attract many different frugivores versus high investment in single fruits and fruit production for extended periods to provide food for few frugivores), and the evolution of syndromes which represent plant adaptations to disperser groups (e.g. birds, mammals, mixed). To test these hypotheses the dispersal strategies of 34 tree species were determined in the littoral forest of Sainte Luce (SE-Madagascar) with the help of fruit traps and tree watches. The impact of fruit consumers on the seeds was determined based on detailed behavioral observations. Phenological, morphological and biochemical fruit traits from tree species were measured to look for co-variation with different types of dispersal. No indication for species-specific co-evolution could be found nor any support for the low/high investment model. However dispersal syndromes could be distinguished as diaspores dispersed by birds, mammals or both groups (mixed) differ in the size of their fruits and seeds, fruit shape, and seed number, but not in biochemical traits. Five large-seeded tree species seem to depend critically on the largest lemur, Eulemur fulvus collaris, for seed dispersal. However, this does not represent a case of tight species-specific co-evolution. Rather it seems to be the consequence of the extinction of the larger frugivorous birds and lemurs which might also have fed on these large fruits. Nevertheless these interactions are of crucial importance to conserve the integrity of the forest.     

Disproportional Representation of Primates in the Ecological Literature

We address the question why papers dealing with the ecology of primates are so sparsely represented in the general ecological literature. A literature analyses based on entries in Web of Science and PrimateLit reveals that despite a large number of papers published on primates in general and on the ecology of primates, only a very small fraction of these papers is published in high-ranking international ecological journals. We discuss a number of potential reasons for the disproportion and highlight the problems associated with experimental research on wild primates and constraints on sample size as major issues.