Craniodental Characters in the Taxonomy of Propithecus

The indriid genus Propithecus comprises the sifakas, medium-sized lemurs endemic to the forests of Madagascar. Traditionally, scientists divided the genus into only 2 or 3 species —Propithecus diadema, P. verreauxi, and, since 1988, P. tattersalli— with 4 or 5 subspecies in each of the first 2 taxa, but recent authors have suggested that many more distinct species should be recognized. We draw from quantitative and qualitative studies of craniodental traits to evaluate further the phenetic distinctiveness and taxonomic status of each named form of Propithecus. We recognize 9–10 species in the genus. The 4 or 5 species of the Propithecus diadema group —P. diadema, P. candidus, P. perrieri, P. edwardsi, and perhaps P. holomelas, if distinct— share several derived features, including large average body size and a mandible specialized for rotational chewing, and clearly comprise a closely related complex. The 5 species of the Propithecus verreauxi group —P. verreauxi, P. coquereli, P. deckenii, P. coronatus, P. tattersalli— are each highly distinctive morphologically and likely do not comprise a monophyletic group. In particular, we point out the highly distinctive cranial features of Propithecus coronatus, which researchers have traditionally largely overlooked.     

Food Intake and Dietary Overlap in Native Lemur catta and Propithecus verreauxi and Introduced Eulemur fulvus at Berenty,Southern Madagascar

The introduction of Eulemur fulvus in 1975 into the Berenty Reserve and their recent attainment of population densities comparable to those of Lemur catta led us to analyze food partitioning among the 3 large prosimian species in the gallery forest. We assessed the diets of ring-tailed lemurs (Lemur catta), brown lemurs (Eulemur fulvus) and sifakas (Propithecus verreauxi) from food intake measurements during 3 successive short-term studies. All species exhibited marked seasonal changes in their major food categories. Dietary overlap was very high between ring-tailed lemurs and brown lemurs during 2 of 3 seasons, including the middle of the dry season. During the latter period, Eulemur appeared to compensate for a low quality diet by increasing the amount of food eaten. In contrast, Lemur fed on lower amounts of food and seemed more efficient at coping with fibrous plant materials. There is low dietary overlap of Lemur catta and Eulemur fulvus versus Propithecus, which exhibit by far the highest dietary diversity of the 3 species. We discuss sustainable coexistence among them, based on respective dietary adaptations and potential for dietary flexibility.     

Chemical Properties of the Diets of Two Lemur Species in Southwestern Madagascar

Seasonal dietary variations demonstrate the importance of certain plant parts during the year. A parallel analysis of their nutritional constituents provides further information on underlying patterns of consumption of the plant parts and the relative importance of key nutrients. I studied the diets of Lemur catta (ring-tailed lemurs) and Propithecus verreauxi verreauxi (sifakas), for 9 mo over a 13-mo period in the highly seasonal tropical dry forest site of Beza Mahafaly in southwestern Madagascar. I tested dietary plant parts for nutrients—protein, free amino acids, and sugars—and for 2 potential deterrents, phenolics and tannins, using plant extracts prepared in the field. I compared consumption of nutrients and secondary compounds throughout the year and between seasons. Nutrients are balanced throughout the year. The 2 lemur species do not appear nutrient-starved in either season, though actual quantities of nutrients and contributing food parts differ for each species. Lemur catta consumes high levels of sugar throughout the year, whereas Propithecus takes in higher levels of protein. The effects of phenolics and tannins are quantitative, and they appear to deter consumption of plant parts only past a certain threshold. Sifakas consume them in greater quantities than those of ring-tailed lemurs, which appear more sensitive to their effects. Sifakas may have a higher tolerance for secondary plant metabolites, which is consistent with reports for other folivores. The overall stability of nutrients throughout the year indicates no lean period that coincides with the decline in food abundance during the dry season, though actual caloric intake probably decreases.     

Forest access restores foraging and ranging behavior in captive sifakas

Captive wildlife benefit from ecologically informed management strategies that promote natural behaviors. The Duke Lemur Center has pioneered husbandry programs rooted in species' ecology for a diversity of lemurs, including housing social groups in multiacre forest enclosures. We systematically document the foraging and ranging patterns of Coquerel's sifakas (Propithecus coquereli) living in these forest enclosures. Coquerel's sifakas are seasonal frugo-folivores that exhibit striking feeding flexibility in the wild. They are also one of the few members of the Indriidae family to persist in captivity. During all-day follows in the spring and summer of 2 consecutive years, we tracked the behavior of 14 sifakas in six forest enclosures. The sifakas' ranging and foraging patterns reflected those of wild sifakas in western Madagascar: On average, DLC sifakas occupied 3-day home ranges of 1.2 ha, traveled 473 m/day, and spent 26% of their time foraging for wild foodstuffs. The sifakas foraged most for young and mature leaves, fruits, nuts, and flowers from 39 plant species, especially red maple (Acer rubrum), tulip poplar (Liriodendron tulipifera), black locust (Robinia pseudoacacia), grapevine (Vitis rotundifolia), hickory (Carya spp.), and white oak (Quercus alba). Foraging patterns varied across seasons, enclosure areas, and groups, potentially reflecting differences in phenology, microhabitats, and individual preferences. While demonstrating that captive-bred primates express wild-like behaviors under ecologically relevant conditions, our results underscore the feeding flexibility of the Coquerel's sifaka. Captive wildlife exhibiting the range of species-specific behaviors are key resources for ecological research and might be best suited for future reintroductions.     

Chromosome banding patterns of the aye-aye,Daubentonia madagascariensis (primates,Daubentoniidae)

The aye-aye (Daubentonia madagascariensis) is an endangered prosimian primate found only on the island of Madagascar. It is the only extant representative of its family Daubentoniidae. The phylogenetic relationship of this species with other prosimians is unclear. Because a G-banded karyotype forDaubentonia has not previously been reported, blood for preparation of lymphocyte cultures was obtained from one of the four aye-ayes in captivity in the United States. The diploid chromosome number was 30. The karyotype consisted of 14 autosomal metacentrics, 10 autosomal submetacentrics, and 4 autosomal acrocentrics. The similarities between the G-banded chromosomes ofDaubentonia and those ofPropithecus, a member of the Indriidae, support the notion thatDaubentonia has a closer relationship with the Indriidae than with other Lemuriformes or the lorisoids.     

Diets of Two Lemur Species in Different Microhabitats in Beza Mahafaly Special Reserve,Madagascar

Studies of primate diets usually focus on differences that distinguish species or populations. However, variation in diet can occur at a more local level of groups within a population, especially in a non-homogeneous habitat. I compared dietary variation in food composition and toughness across groups of 2 lemur species in Beza Mahafaly special reserve, Madagascar. Beza Mahafaly contains an 80-ha reserve (Parcel 1) that, while small, hosts a dense population of Lemur catta (ring-tailed lemurs) and Propithecus verreauxi verreauxi (sifakas). Microhabitats in the eastern vs. western sides of the parcel are structurally and floristically distinct. Sifakas in this parcel have small, discrete home ranges and are morphological folivores. For these reasons, I expected that the 6 groups studied would eat a different menu of food plants but with similar toughness values. Ring-tailed lemurs have comparatively large, overlapping home ranges, and I expected that the 5 study groups would eat similar foods. Despite living in different microhabitats across the parcel, sifakas exhibit high dietary uniformity both in dietary plant species composition and the toughness of the foods. Food selection in sifakas operates on two distinct levels. Sifaka groups share many key food species that appear independent of local abundances, but the ranking of the foods within each group appears related to availability. Ring-tailed lemur groups are more heterogeneous in the composition of their diets relative to sifakas, though the time spent feeding on individual foods reveals a marked preference for the fruits of Tamarindus indica by all groups. Food toughness is consistent across the parcel with the exception of the most western group. Ring-tailed lemurs are highly specific feeders, but indiscriminate nibblers. Sifakas are targeted, balanced feeders. There does not appear to be a consistent microhabitat effect operating across species. Differences within sifaka and ring-tailed lemur populations in food composition and toughness, however, correspond to an east-west microhabitat gradient. Measures of dietary flexibility must take into account not only the plant species consumed and the different parts eaten but also their associated food properties and proportion of time spent feeding on them.     

Females are the ecological sex: Sex‐specific body mass ecogeography in wild sifaka populations (Propithecus spp.)

Previous work in primates has shown that body size often covaries with ecological parameters related to resource or energy availability in the environment. This relationship may differ for males and females as access to resources has greater importance for reproductive success in females. We test the hypotheses that (1) female body mass may be more tightly constrained than male body mass by ecological variables, and (2) female body mass may respond more strongly than male body mass to changes in ecological variables (i.e., population‐specific female mass may vary more across an ecological gradient than male mass). Specifically, we investigate the relationship between climatic variables and sex‐specific body mass in Propithecus, a genus in which species‐specific body mass has already been demonstrated to covary significantly with climatic variables. Data from 733 wild sifakas are used to identify sex‐specific body mass for 27 populations representing all nine described sifaka species, and climatic data for each population are derived from the WorldClim database. We use phylogenetic generalized least squares models to demonstrate that body mass in both sexes is significantly correlated with annual rainfall and number of dry months. Furthermore, coefficients of determination are always higher for female models, and coefficients for each climatic variable are higher for females in all significant models. These results support the two hypotheses tested, indicating that ecological forces can have a greater impact on female mass than on male mass in primates. Am J Phys Anthropol 151:77–87, 2013. © 2013 Wiley Periodicals, Inc.     

Characterization of 20 microsatellites marker loci in the golden-crowned sifaka (<Emphasis Type="Italic">Propithecus tattersalli)</Emphasis>

The golden-crowned sifaka (Propithecus tattersalli) is one of the most critically endangered species of Propithecus endemic to a limited area in the Daraina region of north-eastern Madagascar. This species is endangered due to habitat loss and fragmentation, a consequence of deforestation. Twenty nuclear microsatellite loci were isolated from genomic DNA derived from a Propithecus tattersalli from the Daraina area in north-eastern Madagascar. Population genetic parameters were estimated on 20 individuals from two Daraina forest fragments to determine the potential utility of this marker suite for future studies on the golden-crowned sifaka.     

Intake,digestibility, and passage of a commercially designed diet by two propithecus species

The digestibility and passage of an experimental diet was used to compare the digestive physiology of two Propithecus species: P. verreauxi and P. tattersalli. Though both animals have a similar feeding ecology, the captive status of P. verreauxi is considered more stable than that of P. tattersalli. The test diet included a local tree species, Rhus copallina, at 15% of dry matter intake (DMI) and Mazuri Leafeater Primate Diet at 85% of DMI. The chemical composition of the diet (dry matter basis) was 25% crude protein, 34% neutral detergent fiber (NDF), and 22% acid detergent fiber (ADF) with a gross energy of 4.52 kcal/g. After a 6 week acclimation to the experimental diet, animals were placed in research caging. After a 7 day adjustment period, animals were dosed with chromium mordant and Co‐EDTA as markers for digesta passage and all feed refusals and feces were collected at timed intervals for 7 days. Digestibility values, similar for both species, were approximately 65% for dry matter, crude protein, and energy, and 40% and 35% respectively, for NDF and ADF. Transit times (17–18.5 hr) and mean retention times (31–34 hr) were not significantly different between species, and there was no difference between the chromium mordant and Co‐EDTA. Serum values for glucose, urea, and non‐esterified fatty acids (NEFA) were obtained during four different time periods to monitor nutritional status. While there was no change in serum glucose, serum urea increased over time. The NEFAs increased across all four time periods for P. verreauxi and increased for the first three periods then decreased in the last period for P. tattersalli. Results obtained indicate no difference in digestibility nor digesta passage between species, and that both Propithecus species were similar to other post‐gastric folivores. Am. J. Primatol. 48:237–246, 1999. © 1999 Wiley‐Liss, Inc.     

Relative growth of the limbs and trunk in sifakas: Heterochronic,ecological, and functional considerations

Limb, trunk, and body weight measurements were obtained for growth series of Milne-Edwards's diademed sifaka, Propithecus diadema edwardsi, and the golden-crowned sifaka, Propithecus tattersalli. Similar measures were obtained also for primarily adults of two subspecies of the western sifaka: Propithecus verreauxi coquereli, Coquerel's sifaka, and Propithecus verreauxi verreauxi, Verreaux's sifaka. Ontogenetic series for the larger-bodied P. d. edwardsi and the smaller-bodied P. tattersalli were compared to evaluate whether species-level differences in body proportions result from the differential extension of common patterns of relative growth. In bivariate plots, both subspecies of P. verreauxi were included to examine whether these taxa also lie along a growth trajectory common to all sifakas. Analyses of the data indicate that postcranial proportions for sifakas are ontogenetically scaled, much as demonstrated previously with cranial dimensions for all three species (Ravosa, 1992). As such, P. d. edwardsi apparently develops larger overall size primarily by growing at a faster rate, but not for a longer duration of time, than P. tattersalli and P. verreauxi; this is similar to results based on cranial data. A consideration of Malagasy lemur ecology suggests that regional differences in forage quality and resource availability have strongly influenced the evolutionary development of body-size variation in sifakas. On one hand, the rainforest environment of P. d. edwardsi imposes greater selective pressures for larger body size than the dry-forest environment of P. tattersalli and P. v. coquereli, or the semi-arid climate of P. v. verreauxi. On the other hand, as progressively smaller-bodied adult sifakas are located in the east, west, and northwest, this apparently supports suggestions that adult body size is set by dry-season constraints on food quality and distribution (i. e., smaller taxa are located in more seasonal habitats such as the west and northeast). Moreover, the fact that body-size differentiation occurs primarily via differences in growth rate is also due apparently to differences in resource seasonality (and juvenile mortality risk in turn) between the eastern rainforest and the more temperate northeast and west. Most scaling coefficients for both arm and leg growth range from slight negative allometry to slight positive allometry. Given the low intermembral index for sifakas, which is also an adaptation for propulsive hindlimb-dominated jumping, this suggests that differences in adult limb proportions are largely set prenatally rather than being achieved via higher rates of postnatal hindlimb growth. Our analyses further indicate that the larger-bodied P. d. edwardsi has a higher adult intermembral index than P. tattersalli and P. verreauxi, thus supporting the allometric argument regarding the interspecific scaling of limb proportions in arboreal primates which employ vertical postures (Cartmill, 1974,1985; Jungers, 1978, 1985). Lastly, additional analyses indicate that P. d. edwardsi exhibits significant sexual dimorphism where adult females are larger than adult males in about one-third of all adult comparisons, whereas P. tattersalli exhibits significant sexual dimorphism in about one-fifth of all adult comparisons. Among western sifakas, adult P. v. coquereli exhibit significant sex dimorphism in about one-third of all comparisons, whereas adult P. v. uerreauxi show no significant differences between the sexes. Given that all taxa are ontogenetically scaled, this suggests that sexual dimorphism develops via such processes as well. Interestingly, our data indicate that sex dimorphism is allometric, with larger-bodied taxa like P. d. edwardsi being more dimorphic.     

Interspecific Responses of Ringtailed Lemurs to Playback of Antipredator Alarm Calls Given by Verreaux's Sifakas

The ringtailed lemur, Lemur catta, and Verreaux's sifaka, Propithecus verreauxi verreauxi, are diurnal prosimians living sympatrically in Madagascar. Species-specific alarm calls emitted by each of these two species in response to aerial and terrestrial predators differ acoustically. Behavioural responses of ringtailed lemurs evoked by playbacks of conspecific alarm calls differ when the vocalizations were produced in response to aerial predators as opposed to terrestrial predators. We conducted playback experiments on two populations of ringtailed lemurs, using two types of sifaka alarm calls. One population consisted of free-ranging groups which lived sympatrically with sifakas, the other was a colony group which had no contact with sifakas. The results illustrate that the former group of lemurs can perceive what type of predators the sifaka calls refer to, whereas the latter group was not able to recognize the difference in the calls.     

Characterization of 13 microsatellite marker loci in Verreaux's sifaka (Propithecus verreauxi)

The Verreaux's sifaka (Propithecus verreauxi) is one of the species of Propithecus, living in the dry forest of southwest Madagascar. This species is endangered due to the loss and fragmentation of its natural habitat, a consequence of deforestation. Thirteen novel nuclear microsatellite loci were isolated and characterized in three populations of Verreaux's sifaka. The marker suite proved informative with an average of 8.9 alleles per locus and observed heterozygosity across the three populations of 0.675.     

Characterization of 20 microsatellite marker loci in Coquerel's sifaka (Propithecus coquereli)

The Coquerel's sifaka (Propithecus coquereli) is one of the species of Propithecus, living in the dry forest of northwest Madagascar. This species is endangered due to the loss and fragmentation of its natural habitat, consequential of deforestation. Twenty nuclear microsatellite loci were isolated from genomic DNA derived from a free ranging Coquerel's sifaka from the Mariarano Classified Forest, Madagascar. Population genetic parameters were estimated as baseline values from samples collected in that forest.     

Variation in the Meaning of Alarm Calls in Verreaux’s and Coquerel’s Sifakas (<Emphasis Type="Italic">Propithecus verreauxi,P. coquereli</Emphasis>)

The comprehension and usage of primate alarm calls appear to be influenced by social learning. Thus, alarm calls provide flexible behavioral mechanisms that may allow animals to develop appropriate responses to locally present predators. To study this potential flexibility, we compared the usage and function of 3 alarm calls common to 2 closely related sifaka species (Propithecus verreauxi and P. coquereli), in each of 2 different populations with different sets of predators. Playback studies revealed that both species in both of their respective populations emitted roaring barks in response to raptors, and playbacks of this call elicited a specific anti-raptor response (look up and climb down). However, in Verreaux’s sifakas, tchi-faks elicited anti-terrestrial predator responses (look down, climb up) in the population with a higher potential predation threat by terrestrial predators, whereas tchi-faks in the other population were associated with nonspecific flight responses. In both populations of Coquerel’s sifakas, tchi-fak playbacks elicited anti-terrestrial predator responses. More strikingly, Verreaux’s sifakas exhibited anti-terrestrial predator responses after playbacks of growls in the population with a higher threat of predation by terrestrial predators, whereas Coquerel’s sifakas in the raptor-dominated habitat seemed to associate growls with a threat by raptors; the 2 other populations of each species associated a mild disturbance with growls. We interpret this differential comprehension and usage of alarm calls as the result of social learning processes that caused changes in signal content in response to changes in the set of predators to which these populations have been exposed since they last shared a common ancestor.     

Dietary Flexibility and Feeding Strategies of <Emphasis Type="Italic">Eulemur</Emphasis>: A Comparison with <Emphasis Type="Italic">Propithecus</Emphasis>

Despite the great variety of habitats in Madagascar, Eulemur has successfully populated most forested habitats on the island. Although the high dietary flexibility of Eulemur is often credited as one of the drivers of its evolutionary success, other behavioral evidence suggests a limited capacity for dietary switching. To shed light on the feeding strategies of Eulemur, we compared the dietary flexibility between populations of this genus with that of another widespread lemur taxon, Propithecus. We hypothesized that Eulemur would show greater dietary flexibility than Propithecus, which has a digestive system specialized for folivory, and that Eulemur living in dry forests would switch its diet from fruit to other food seasonally. To examine these hypotheses, we performed a phylogenetic least-squares analysis on 10 populations of Eulemur and 7 of Propithecus to assess the contribution of environmental variables and body mass on their dietary flexibility while controlling for phylogenetic relatedness. Eulemur relied heavily on fruit and did not show large variations in primary food over the year. Propithecus consumed leaves and fruits equally and exhibited considerable flexibility across seasons. Therefore, in contrast to our predictions, the anatomical specialization for fiber digestion heightens dietary flexibility in Propithecus. At the intrageneric level, we found similar ecogeographic variation; populations of both genera with heavier body mass consumed more fruit. As we predicted, Eulemur in drier habitats switched the diet from fruit to alternative food more frequently. To compensate for low dietary flexibility, Eulemur mostly adopts a power-feeding strategy by which it increases energy expenditure to acquire patchily distributed fruit resources.     

Chromosome Painting Technique Contributes to Constructions of Evolutionary Trees of Lemurs

We used human-specific probes for chromosomes 3, 11, 14, 15, 17, 19, 21 to paint chromosomes of four species of Indridae (Avahi laniger, Indri indri, Propithecus verreauxi, and P. diadema). All human chromosome probes hybridized specifically to chromosome segments or to whole arms of indrid chromosomes. In general, the results obtained by chromosome painting confirm those obtained by R-banding except for some reciprocal translocations undetected by R-banding. Our findings confirm that in the evolution of the Indridae, Avahi laniger first emerges, then Indri and Propithecus share a common trunk. After populational evolution, this sister clade diverged.     

Genetic variability in migratory and endemic island songbirds (genus Vireo): A comparative assessment using molecular and morphological traits

Low genetic variation is thought to increase the risk of extinction in island species; however, these species can differ both in terms of endemism and gene flow. In a previous study, the endemic species of Puerto Rico (V. latimeri) and Jamaica (V. modestus and V. osburni) were shown to have less genetic variability than a continental relative, V. griseus. In this study, a migratory island species, V. altiloquus, is analyzed together with the endemics in order to (1) compare levels of genetic variation in migratory and endemic island species, and (2) assess this variation using both molecular markers and morphological traits. Each island species is also compared to a continental relative (V. griseus for the endemic species, and V. olivaceus for the migratory species). Variability in random amplified polymorphic DNA markers was significantly lower in the endemic species than in either migratory population. All island populations had significantly lower levels of variation than their respective continental relatives, but with significantly greater reduction in the endemic species. In contrast, the morphological measures revealed only two cases with a significantly lower CV in an endemic species compared to V. altiloquus or V. griseus. All others exhibited either no differences in CV or greater levels in the island populations. While the molecular results generally correspond to predictions of lower variability in endemic vs. migratory island species and island vs. continental species, the morphological comparisons do not, and therefore may not be useful for quick, field-based assessments of underlying genetic variability. This revised version was published online in July 2006 with corrections to the Cover Date.     

Phylogeography of related diadromous species in continental and island settings,and a comparison of their potential and realized dispersal patterns

Aim To compare patterns of potential and realized dispersal in ecologically similar and phylogenetically related amphidromous shrimps (Atyidae) in continental and island‐dominated landscapes. Location Eastern Australia and the Caribbean region. Methods Population genetic and phylogeographic analyses of mitochondrial DNA data for Australatya striolata from eastern Australia (a continental landscape) and Atya scabra from the Caribbean (an island‐dominated landscape). Results Australatya striolata contained two highly divergent genetic lineages in eastern Australia, corresponding to the disjunct northern and southern populations, respectively. These lineages probably represent allopatric cryptic species, both of which were found to have genetically homogeneous population structures within their regions of occurrence. Atya scabra was genetically homogeneous throughout the Caribbean. Recent population expansions were detected for Atya scabra in the Caribbean, but not for northern or southern Australatya striolata. Main conclusions The findings of this study are consistent with previously reported patterns of genetic population structure in amphidromous species in both continental and island‐dominated landscapes, suggesting that potential for widespread dispersal is typically matched by realized patterns of panmixia. We therefore raise the hypothesis that landscape setting (i.e. continent or island‐dominated) does not influence dispersal patterns in amphidromous species. Further studies, especially of population genetic patterns of amphidromous species on continents, are needed to test this idea. Interestingly, results of the genetic neutrality tests led us to hypothesize that demographic and drift‐mutation equilibrium is attainable although not always evident for amphidromous species on continents, but is not attainable for those species distributed across island settings.     

Richness and composition of plants and birds on land‐bridge islands: effects of island attributes and differential responses of species groups

Aim To test relationships between the richness and composition of vascular plants and birds and attributes of habitat fragments using a model land‐bridge island system, and to investigate whether the effects of fragmentation differ depending on species natural history traits. Location Thousand Island Lake, China. Methods We compiled presence/absence data of vascular plant and bird species through exhaustive surveys of 41 islands. Plant species were assigned to two categories: shade‐intolerant and shade‐tolerant species; bird species were assigned to three categories: edge, interior, and generalist species. We analysed the relationships between island attributes (area, isolation, elevation, shape complexity, and perimeter to area ratio) and species richness using generalized linear models (GLMs). We also investigated patterns of composition in relation to island attributes using ordination (redundancy analysis). Results We found that island area explained a high degree of variation in the species richness of all species groups. The slope of the species–area relationship (z) was 0.16 for all plant species and 0.11 for all bird species. The lowest z‐value was for generalist birds (0.04). The species richness of the three plant species groups was associated with island area per se, while that of all, generalist, and interior birds was explained mainly by elevation, and that of edge bird species was associated primarily with island shape. Patterns of species composition were most strongly related to elevation, island shape complexity, and perimeter to area ratio rather than to island area per se. Species richness had no significant relationship with isolation, but species composition did. We also found differential responses among the species groups to changes in island attributes. Main conclusions Within the Thousand Island Lake system, the effects of fragmentation on both bird and plant species appear to be scale‐dependent and taxon‐specific. The number of plant species occurring on an island is strongly correlated with island area, and the richness of birds and the species composition of plants and birds are associated with variables related to habitat heterogeneity. We conclude that the effects of fragmentation on species diversity and composition depend not only on the degree of habitat loss but also on the specific patterns of habitat fragmentation.     

Demography of Propithecus verreauxi at Beza Mahafaly,Madagascar: Sex ratio,survival, and fertility, 1984–1988

Eighty-five sifakas (Propithecus verreauxi) have been captured, marked, released, and monitored between September 1984 and August 1988 at the Beza Mahafaly Special Reserve in southwest Madagascar. Estimates are presented of the age and sex structure of this population and of age-specific fertility and survival. Using data from this and other studies, it is shown that sifaka tertiary sex ratios do not depart significantly from 50:50, but that they do differ significantly from those of haplorhine primates, which have strongly female-biased tertiary sex ratios. Two demographic mechanisms that could give rise to this distinction are considered: 1) intermittently male-biased birth cohorts among sifakas and 2) different patterns of survivorship in haplorhines and sifakas.