Unexpected species diversity of Malagasy primates (<Emphasis Type="Italic">Lepilemur</Emphasis> spp.) in the same biogeographical zone: a morphological and molecular approach with the description of two new species

Background  

The lemurs of Madagascar provide an excellent mammalian radiation to explore mechanisms and processes favouring species diversity and evolution. Species diversity, in particular of nocturnal species, increased considerably during the last decade. However, the factors contributing to this high diversity are not well understood. We tested predictions derived from two existing biogeographic models by exploring the genetic and morphological divergence among populations of a widely distributed lemur genus, the sportive lemur (Lepilemur ssp.) along a 560 km long transect from western to northern Madagascar.     

Use of Vocal Fingerprinting for Specific Discrimination of Gray (Microcebus murinus) and Rufous Mouse Lemurs (Microcebus rufus)

Advertisement calls are often important noninvasive tools for discriminating cryptic species and for assessing specific diversity and speciation patterns in nature. We investigated the contribution of these calls to uncover specific diversity in nocturnal Malagasy lemurs. We compared sexual advertisement and predator advertisement calls of two mouse lemur species, western gray and eastern rufous mouse lemurs (Microcebus murinus and M. rufus, respectively) living in two contrasting habitats (dry deciduous vs. rain forest), and analyzed them statistically. Both species emitted several highly variable whistle calls in the context of predator-avoidance. Intrapopulation variation was high and overlapped interspecific variation. Sexual advertisement calls, given in the mating context, displayed a totally distinct, species-specific acoustic structure. Whereas gray mouse lemurs produced rapidly multifrequency modulated, long trill calls, rufous mouse lemurs gave slowly frequency-modulated short chirp calls. Our results suggest specific status for gray and rufous mouse lemurs and indicate the importance of predation and social needs in shaping vocal communication.     

Species delimitation in lemurs: multiple genetic loci reveal low levels of species diversity in the genus Cheirogaleus

Background  

Species are viewed as the fundamental unit in most subdisciplines of biology. To conservationists this unit represents the currency for global biodiversity assessments. Even though Madagascar belongs to one of the top eight biodiversity hotspots of the world, the taxonomy of its charismatic lemuriform primates is not stable. Within the last 25 years, the number of described lemur species has more than doubled, with many newly described species identified among the nocturnal and small-bodied cheirogaleids. Here, we characterize the diversity of the dwarf lemurs (genus Cheirogaleus) and assess the status of the seven described species, based on phylogenetic and population genetic analysis of mtDNA (cytb + cox2) and three nuclear markers (adora3, fiba and vWF).     

Comparing the accuracy and precision of three techniques used for estimating missing landmarks when reconstructing fossil hominin crania

In some primate species, pelage colorations at birth contrast with adult colorations. The intensity of natal coats and their phylogenetic distribution is highly variable within primates. Natal coat coloration seems to change to adult coloration in most species when infants become independent from their mothers, but an accepted functional explanation for natal coats is not available. Here we describe pelage coloration change in sexually dichromatic redfronted lemurs (Eulemur fulvus rufus) in Kirindy Forest, and propose a new functional hypothesis for this phenomenon. In this species, infants are born with adult male coloration and female infants subsequently undergo a change in coloration. Using digital pictures and behavioral data collected on eight mother-offspring dyads from birth until the end of the coloration change, we 1) described timing and pattern of pelage developmentin redfronted lemur infants and 2) examined behavioral developmental correlates of the coloration change. The color change took place between 7 and 17 weeks of age and coincided with advanced physical independence; a pattern also found in monochromatic primate species with natal coats. No behavioral differences between male and female infants were found. Hypotheses about the ultimate function of natal coats focusing on enhanced infant care or reduced infanticide risk did not explain the pelage change in redfronted lemurs. The natal pelage pattern in this species may instead serve as sexual mimicry. Accordingly, female infants may mimic males during the most vulnerable developmental phase to avoid sex-specific aggression by adult females in a species with intense female-female aggression and competition.     

Y chromosome evidence of earliest modern human settlement in East Asia and multiple origins of Tibetan and Japanese populations

Background

A central question in evolutionary biology is how cryptic species maintain species cohesiveness in an area of sympatry. The coexistence of sympatrically living cryptic species requires the evolution of species-specific signalling and recognition systems. In nocturnal, dispersed living species, specific vocalisations have been suggested to act as an ideal premating isolation mechanism. We studied the structure and perception of male advertisement calls of three nocturnal, dispersed living mouse lemur species, the grey mouse lemur (Microcebus murinus), the golden brown mouse lemur (M. ravelobensis) and the Goodman's mouse lemur (M. lehilahytsara). The first two species occur sympatrically, the latter lives allopatrically to them.

Results

A multi-parameter sound analysis revealed prominent differences in the frequency contour and in the duration of advertisement calls. To test whether mouse lemurs respond specifically to calls of the different species, we conducted a playback experiment with M. murinus from the field using advertisement calls and alarm whistle calls of all three species. Individuals responded significantly stronger to conspecific than to heterospecific advertisement calls but there were no differences in response behaviour towards statistically similar whistle calls of the three species. Furthermore, sympatric calls evoked weaker interest than allopatric advertisement calls.

Conclusion

Our results provide the first evidence for a specific relevance of social calls for speciation in cryptic primates. They furthermore support that specific differences in signalling and recognition systems represent an efficient premating isolation mechanism contributing to species cohesiveness in sympatrically living species.     

Seasonal changes in general activity, body mass and reproduction of two small nocturnal primates: a comparison of the golden brown mouse lemur ( Microcebus ravelobensis) in Northwestern Madagascar and the brown mouse lemur ( Microcebus rufus) in Eastern Madagascar

To investigate for the first time the relationship between contrasting patterns of seasonal changes of the environment and activity, body mass and reproduction for small nocturnal primates in nature, we compared a population of golden brown mouse lemur (Microcebus ravelobensis) in a dry deciduous forest of northwestern Madagascar and of the brown mouse lemur (Microcebus rufus) in an evergreen rain forest of eastern Madagascar. Both species live under similar photoperiodic conditions. Golden brown mouse lemurs (GBML) were active during the whole period (May to December) irrespective of changing environmental conditions. In contrast, a part of the population of brown mouse lemurs (BML) showed prolonged seasonal torpor, related to body mass during periods of short day length and low ambient temperatures. Differences between species might be due to differences in ambient temperature and food supply. Body weight and tail thickness (adipose tissue reserve) did not show prominent differences between short and long photoperiods in GBML, whereas both differ significantly in BML, suggesting species-specific differences in the photoperiodically driven control of metabolism. Both species showed a seasonal reproduction. The rate of growth and size of the testes were similar and preceded estrous onset in both species suggesting a photoperiodic control of reproduction in males. The estrous onset in females occurred earlier in GBML than in BML. Estrous females were observed over at least 4 months in the former, but in only 1 month in the latter species. Intraspecific variation of estrous onset in GBML may be explained by body mass. Interspecific variation of female reproduction indicates species-specific differences in the control of reproduction. Thus, environmentally related differences in annual rhythms between closely related small nocturnal lemurs emerged that allow them to cope with contrasting patterns of seasonal changes in their habitats.     

Molecular Evidence of Reproductive Isolation in Sympatric Sibling Species of Mouse Lemurs

Recent morphological and molecular phylogenetic studies of mouse lemurs (Microcebus) living in the western and southern regions of Madagascar have shown that specific diversity had been considerably underestimated. In large part, this underestimate was due to the lack of sufficient specimens from given localities to assess properly the level of phenotypic variation within and between populations. The accurate delineation of specific boundaries has no doubt been confounded by the diminutive size, nocturnal habits, and subtle morphological variation characteristic of mouse lemurs, which can make field identification of individuals problematic. We illustrate the use of molecular phylogenetic analysis to reveal reproductive isolation in two sympatric mouse lemur species, Microcebus murinus and M. griseorufus. Their documentation in the Berenty Private Reserve in the extreme south of Madagascar verifies the historically-broad distribution of Microcebus griseorufus, a species recently resurrected from synonomy.     

The role of nocturnal omnivorous lemurs as seed dispersers in Malagasy rain forests

Fruit-eating animals play important roles as seed dispersal agents in terrestrial systems. Yet, the extent to which seed dispersal by nocturnal omnivores may facilitate germination and the recruitment of plant communities has rarely been investigated. Characterizing their roles in seed dispersal is necessary to provide a more complete picture of how seed dispersal processes affect ecosystem functioning. We investigated the roles and impacts of two species of nocturnal omnivorous lemur species, Microcebus jollyae and M. rufus, on seed dispersal in Madagascar's rain forests, through analysis of fecal samples and germination experiments. Data show that these lemur species, which are among the world's smallest primates, dispersed 22 plant species from various forest strata and that the defecated seeds germinated faster and at higher rates than control seeds for the eight plant species we tested. Even though mouse lemurs dispersed both native and non-native plant species, non-native plant species represented a relatively small proportion (17%). These results demonstrate that overlooked nocturnal omnivores can act as important seed dispersers, which may have critical implications for forest regeneration and the maintenance of plant diversity in fragmented/degraded forests. Finally, we provide critical insights into the previously unobserved behavior and diet of endangered nocturnal lemurs for their effective conservation.     

Distribution and Geographic Variation in the Western Woolly Lemur (Avahi occidentalis) with Description of a New Species (A. unicolor

The western woolly lemur is distributed through central western, northwestern and possibly northern Madagascar and is traditionally viewed as a monotypic species (Avahi occidentalis) or as a subspecies of A. laniger. We present new data on body weights of Avahi which, together with previously available body weights, provide additional evidence for recognizing eastern and western woolly lemurs as two distinct species. We then reexamine the distributions of, and chromatic variation within and between, populations of western woolly lemurs. A comparative study of wild subjects and museum skins reveals that several geographically discrete morphs exist in western Avahi, which is clearly polytypic. Marked differences between populations in fur coloration suggest that 3 distinct taxa should be recognized. The populations differ considerably in their habitat structure. In addition, field observations suggest clear differences in population density between 2 of the populations. We describe and name one new species.     

Direct and Indirect Impacts of Raptor Predation on Lemurs in Southeastern Madagascar

I calculated rates of predation by 2 species of diurnal raptors, Polyboroides radiatus and Accipiter henstii, on the lemur community of Ranomafana National Park, Madagascar from 2700 h of observation and 470 prey deliveries at 7 nests of each hawk species. The 2 hawks consumed 7 of 12 lemurs found in the park region, with a body mass of 63–3500 g and including diurnal and nocturnal species of all group sizes. Calculations of predation rates indicate that raptor predation is a significant cause of mortality for lemur populations relative to other causes. Minimum rates of predation by Polyboroides radiatus and Accipiter henstii on Microcebus rufus, Cheirogaleus major, Avahi laniger, Hapalemur griseus, Eulemur fulvus rufus, Eulemur rubriventer, and Varecia variegata resulted in the raptors removing of 1–21% of the population per yr, similar to other rates of predation on primates documented in the literature. Modeling of lemur populations under varying levels of raptor predation pressure that I calculated found that one may attribute 3–17% of adult, juvenile, and infant mortality for nocturnal lemurs and 2–66% of adult, juvenile, and infant mortality for diurnal lemurs to diurnal raptor predation. Raptor predation may significantly depress intrinsic growth rates and carrying capacity of Avahi laniger, Hapalemur griseus, Eulemur fulvus rufus, Eulemur rubriventer, and Varecia variegata owing to their low fecundities, long life spans, and long age to sexual maturation. Nocturnal lemurs may best avoid predation by diurnal raptors by exhibiting a solitary lifestyle and cryptic antipredator tactics, whereas, diurnal lemurs benefit less by increasing group size than by using specific antipredator tactics.     

Isolation of new microsatellite markers and application in four species of mouse lemurs (Microcebus sp.)

We report the development of 13 new microsatellite markers for mouse lemurs (Microcebus sp.). Two markers were isolated from the fat tailed dwarf lemur (Cheirogaleus medius) and 11 from the grey mouse lemur (Microcebus murinus). A total of 561 individuals from four different species of mouse lemurs was genotyped with the newly developed markers. All markers showed Mendelian inheritance in 21 families of mouse lemurs. All markers show polymorphism in several species of mouse lemurs and seven amplified in C. medius. Among these new markers are the first 10 published for M. berthae and the first 11 for M. griseorufus.     

Forest Type Influences Population Densities of Nocturnal Lemurs in Manompana,Northeastern Madagascar

Forest loss, fragmentation, and anthropization threaten the survival of forest species all over the world. Shifting agriculture is one of these threatening processes in Madagascar. However, when its cycle is halted and the land is left to regenerate, the resulting growth of secondary forest may provide a viable habitat for folivorous and omnivorous lemur species. We aimed to identify the response of nocturnal lemurs to different successional stages of regenerating secondary, degraded mature, and mature forest across a mosaic-type landscape. We surveyed four nocturnal lemur species (Avahi laniger, Microcebus cf. simmonsi, Allocebus trichotis, and Daubentonia madagascariensis) in four forest types of varying habitat disturbance in northeastern Madagascar. We estimated densities in mature and regenerating secondary forest for the eastern woolly lemur (Avahi laniger) and mouse lemur (Microcebus cf. simmonsi), two sympatric species with folivorous and omnivorous diets respectively. We did not estimate densities of Allocebus trichotis and Daubentonia madagascariensis owing to small sample size; however, we observed both species exclusively in mature forest. We found higher population densities of A. laniger and M. cf. simmonsi in secondary than in mature forest, showing the potential of regenerating secondary forest for lemur conservation. Several environmental factors influenced the detectability of the two lemur species. While observer and habitat type influenced detection of the eastern woolly lemur, canopy height and vine density influenced detection of mouse lemurs. Understanding how different species with different diets interact with anthropogenically impacted habitat will aid future management decisions for the conservation of primate species.     

Lemur Diversity in Madagascar

A basic understanding of the taxonomy, diversity, and distributions of primates is essential for their conservation. This review of the status of the taxonomy of lemurs is based on a 5-d workshop entitled “Primate Taxonomy for the New Millennium,” held at the Disney Institute, Orlando, Florida, in February 2000. The aim is not to present a taxonomic revision, but to review our current understanding of the diversity and current and past ranges of lemurs and indicate where there is controversy, discrepancy, or lack of knowledge. Our goal therefore is to provide a baseline for future taxonomic investigation, as well as a clearer focus for research and conservation priorities. We here focus on the lemurs of Madagascar and recognize 5 families, 15 genera, and 99 species and subspecies. We list 39 species of lemurs described since 2000: 2 dwarf lemurs, Cheirogaleus; 11 mouse lemurs, Microcebus; a giant mouse lemur, Mirza; a bamboo lemur, Hapalemur; 17 sportive lemurs, Lepilemur; and 7 woolly lemurs, Avahi. Taxonomic revisions have resulted in the resurrection of a further 9 taxa. However, the figures do not represent the total diversity of Malagasy lemurs because more new species are being identified via new field studies and accompanying genetic research, and should be described in the near future.     

Frugivory and Seed Dispersal by Brown Lemurs in a Malagasy Tropical Dry Forest

In the Ankarafantsika tropical dry forest (northwestern Madagascar), the common brown lemur (Eulemur fulvus fulvus) is the largest frugivore and probably the sole disperser of large‐seeded plants (seed diameter > 10 mm). To investigate seed dispersal by this primate, I recorded the feeding activities of a troop; also conducted fecal analyses, germination trials on defecated seeds, and a vegetation survey over 1 yr (beginning Dec 2006). Brown lemurs mostly consumed fruit (68%). The fruit of Vitex beraviensis was the most exploited resource (21% of total feeding time). Among dung samples, 1126 contained intact seeds of 70 plant species, with a median of six seeds and two species per sample. These data indicate that the brown lemur population dispersed approximately 9854 seeds/km²/d. Although the number of annually defecated seeds was overwhelmingly the largest in Grewia triflora, many of the small seeds were often clumped in dung piles. In contrast, large seeds of V. beraviensis occurred in the largest number of dung samples. The rate and time of seed germination in V. beraviensis were improved by passage through brown lemur guts. Therefore, V. beraviensis may readily establish seedlings in sites of brown lemur fecal deposition. Vitex beraviensis and brown lemurs are probably involved in a strong mutualism. Twenty‐three large‐seeded plants were probably dependent on brown lemurs for seed dispersal and some of these species were common trees in the forest. Maintenance of these key plant–animal interactions will probably contribute to the conservation of species diversity and intact regeneration of the Ankarafantsika forest.     

Explaining geographical variation in the isotope composition of mouse lemurs (Microcebus)

Aim We sought to quantify geographical variation in the stable isotope values of mouse lemurs (Microcebus) and to determine whether this variation reflects trophic differences among populations or baseline isotopic differences among habitats. If the latter pattern is demonstrated, then Microcebus can become a proxy for tracking baseline habitat isotopic variability. Establishing such a baseline is crucial for identifying niche partitioning in modern and ancient communities. Location We studied five species of Microcebus from eight distinct habitats across Madagascar. Methods We compared isotopic variation in C₃ plants and Microcebus fur within and among localities. We predicted that carbon and nitrogen isotope values of Microcebus should: (1) vary as a function of abiotic variables such as rainfall and temperature, and (2) covary with isotopic values in plants. We checked for trophic differences among Microcebus populations by comparing the average difference between mouse lemur and plant isotope values for each locality. We then used multiple regression models to explain spatial isotope variation in mouse lemurs, testing a suite of explanatory abiotic variables. Results We found substantial isotopic variation geographically. Ranges for mean isotope values were similar for both Microcebus and plants across localities (carbon 3.5–4.0‰; nitrogen 10.5–11.0‰). Mean mouse lemur and plant isotope values were lowest in cool, moist localities and highest in hot, dry localities. Rainfall explained 58% of the variation in Microcebus carbon isotope values, and mean plant nitrogen isotope values explained 99.7% of the variation in Microcebus nitrogen isotope values. Average differences between mouse lemur and plant isotope values (carbon 5.0‰; nitrogen 5.9‰) were similar across localities. Main conclusions Isotopic data suggest that trophic differences among Microcebus populations were small. Carbon isotope values in mouse lemurs were negatively correlated with rainfall. Nitrogen isotope values in Microcebus and plants covaried. Such findings suggest that nitrogen isotope values for Microcebus are a particularly good proxy for tracking baseline isotopic differences among habitats. Our results will facilitate future comparative research on modern mouse lemur communities, and ecological interpretations of extinct Holocene communities.     

Seasonal differences in hair growth rates of captive aye-aye,red ruffed,and black-and-white ruffed lemurs

Hair can be an important source of biological information, providing a record of such things as pollutant exposure, hormonal levels, and stable isotope ratios. Hair as a biological sample is easily accessible, easily stored, and resists degradation. Analysis of hair is particularly useful when studying rare and endangered species, such as lemurs, since it can be sampled noninvasively. However, to better interpret the results of stable isotope or other analyses, it is important to understand hair growth rates. We measured hair growth rates in captive aye-ayes (Daubentonia madagascariensis), red ruffed lemurs (Varecia rubra), and black-and-white ruffed lemurs (Varecia variegata), both in winter (December 23, 2013, to January 13, 2014) and summer (July 10–31, 2013) at the Duke Lemur Center. Hair growth per week in all three species of lemurs differed significantly between the boreal summer and boreal winter. The aye-aye, black-and-white ruffed lemur, red ruffed lemur had a mean weekly hair growth of 0.195, 0.209, and 0.232 cm, respectively, in the summer. While the aye-aye, black-and-white ruffed lemur, and red ruffed lemur had a mean weekly hair growth of 0.239, 0.464, and 0.479 cm, respectively, in winter. We found no effect of age on hair growth rates, neither in the boreal summer, nor in the boreal winter for black-and-white ruffed lemurs and red ruffed lemurs. A pregnant black-and-white ruffed female displayed negligible hair growth during the northern winter, suggesting that pregnancy may affect the partitioning of resources away from such things as hair growth.     

The lack of female dominance in golden‐brown mouse lemurs suggests alternative routes in lemur social evolution

Female dominance is a well‐known trait of lemurs, although it has not been reported from all species and is still often unexplored, especially in the nocturnal species. We examined the intersexual dominance relationships in Microcebus ravelobensis, a congener of M. murinus who is well known for its female dominance. Given the many similarities in biology, it was predicted that M. ravelobensis should also possess female dominance. Seventeen unfamiliar male–female pairs were formed with animals captured in northwestern Madagascar and kept in a two‐cage setting (one cage for each animal) for up to 1 week. Four encounter experiments were conducted with each pair. In contrast to the expectations, females were not consistently dominant over their male partners. Only 3 of 17 dyads developed a clear agonistic asymmetry, among which were two cases of male dominance and only one case of female dominance. Because body mass differences did not explain the findings, various other possible explanations are discussed. It is suggested that food may not be the driving factor of female dominance in mouse lemurs. Instead, it is hypothesized that species‐specific differences in the quality of sleeping sites (i.e., tree holes) and in social grouping patterns may better explain why some mouse lemur species have female dominance, whereas others like the golden‐brown mouse lemur do not. It is concluded thatthese arguments and hypotheses may even hold true for other solitary foragers and may thereby lead to a better understanding of the variable social evolution in lemurs and primates in general. Am J Phys Anthropol, 2013. © 2012 Wiley Periodicals, Inc.     

Evidence of prolonged torpor in Goodman’s mouse lemurs at Ankafobe forest,central Madagascar

The small-bodied mouse lemurs of Madagascar (Microcebus) are capable of heterothermy (i.e., torpor or hibernation). The expression of these energy-saving strategies has been physiologically demonstrated in three species: M. berthae, the pygmy mouse lemur (daily torpor), M. murinus, the gray mouse lemur (daily torpor and hibernation), and M. griseorufus, the reddish-gray mouse lemur (daily, prolonged torpor and hibernation). Additional evidence, based on radiotracking and seasonal body mass changes, indicated that mouse lemur capabilities for heterothermy extended to M. lehilahytsara, the Goodman’s mouse lemur. In this study, we confirm the use of hibernation in Goodman’s mouse lemurs at a new location, a high-plateau forest fragment in Ankafobe, central Madagascar. Our evidence is based on sleeping site monitoring of radiocollared individuals and the retrieval of three mouse lemurs from inside a tree hole, all of which displayed a lethargic state. Though our data are preliminary and scant, we show that hibernation occurs in high-plateau mouse lemurs, and suggest that a buffered environment (i.e., tree holes instead of nests) may be crucial to avoiding potentially extreme ambient temperatures.     

Comparison of Reproductive Characteristics and Changes in Body Weight Between Captive Populations of Rufous and Gray Mouse Lemurs

The nocturnal Malagasy mouse lemurs are among the smallest primates worldwide. Several sibling species are known. Of these, the rufous and the gray mouse lemur differ with respect to morphology, genetics, and communication. They might also differ in seasonal reproduction and body weight changes. We investigated and compared reproductive activities and changes in monthly body weight in males and females of successfully breeding colonies of both species under the same photoperiodic conditions. Females of both species showed estrous cycles only during the long-day period. Rufous mouse lemur females seemed to have a shorter gestation than their sibling species (57 vs. 62 days). The number of estrous cycles (2.25 vs. 2.5/season) and their lengths (59 vs. 52 days) were similar. Litter size (2) seemed to be similar. Latency of estrous occurrence after photoperiodic stimulation was longer in Microcebus rufus than in its sibling species (71.6 and 42.3 days). The same was true for the onset of the growth of the testes. The rate of growth and size of the testes were similar, and precede the estrous onset in both species. The reproductive activity was shorter in both sexes of the rufous than of the gray mouse lemurs. In both species, body weight showed similar seasonal changes. Males lost more weight during the breeding season than females did. In rufous mouse lemurs, body weight was similar in both sexes during the nonbreeding season. In gray mouse lemurs, sexes differed throughout the year.