Hand specialization, sympatry, and mixed-species associations in callitrichines

Hand morphology in callitrichines (i.e., tamarins, marmosets, and Goeldi's monkey) is correlated with positional and foraging behaviors. This study examines hand shape in callitrichines using an allometric approach. It addresses a series of questions relating hand anatomy, insect foraging behavior, and resource partitioning in callitrichines. The main questions are: 1. Do the hands of Leontopithecus differ in shape from all other callitrichine taxa allowing it to perform highly manipulative prey foraging behaviors? 2. Are the hands of Saguinus fuscicollis adapted to manipulative foraging, and are they functionally similar to Leontopithecus' hands? 3. Is hand morphology in S. fuscicollis more similar to the hand morphology of sympatric tamarin species with whom it does not form mixed species troops (S. nigricollis and S. tripartitus) than to those sympatric tamarin species with whom it does form mixed troops (S. mystax, S. labiatus, and S. imperator)? Measurements of hand length (HL), width (HW), and thickness (HT) were taken from 1350 museum specimens of callitrichines (Callithrix, Cebuella, Leontopithecus, Saguinus, and Callimico), squirrel monkeys (Saimiri), and owl monkeys (Aotus). The analysis indicates that hand shape covaries with foraging strategy. Specifically, the hands of Leontopithecus are adapted for manipulative foraging and are relatively longer and more slender than the hands of other callitrichines. A similar pattern is observed in the hands of S. fuscicollis, S. tripartitus and S. nigricollis. These latter species, however, differ significantly in shape from all other tamarin species. Large differences in hand morphology are observed among tamarin species that form mixed-species troops. These anatomical differences may permit resource partitioning and coexistence among these closely related taxa. Hand shape, expressed as log HLGM (logged hand length divided by the geometric mean of all measurements), is a good predictor of manipulative and non-manipulative prey foraging techniques employed by callitrichines.     

A molecular phylogeny of four endangered Madagascar tortoises based on MtDNA sequences

Four of the five tortoise species in Madagascar, Pyxis arachnoides, P. planicauda, Geochelone radiata, and G. yniphora, are endemic and on the verge of extinction. Their phylogenetic relationships remain controversial and unresolved. Here we address the phylogeny of this group using DNA sequences for the 12S and 16S rDNA and cyt b genes in mitochondrial DNA. As outgroups we used two species of Geochelone, pardalis (mainland Africa) and nigra (Galápagos), as well as a more distant North American tortoise, Gopherus polyphemus. We conclude that the two Pyxis species are sister taxa and are imbedded in the genus Geochelone, rendering this latter genus paraphyletic. There is moderate support for the sister status of the two Madagascar Geochelone and for the monophyletic origin of all four endemics, suggesting a single colonization of the island. The separation of Madagascar from other land masses (90-165 mya) predates the origin of the endemic tortoises (estimated to be 14-22 mya). This suggests founding by rafting, a process known to have occurred with other tortoises. The derived morphological divergence of the Pyxis species in a relatively short period of time (13-20 my) stands in contrast to the notoriously slow rate of morphological evolution in most lineages of Chelonia.     

Molecular phylogenetic relationship of snow finch complex (genera Montifringilla, Pyrgilauda, and Onychostruthus) from the Tibetan plateau

The snow finch complex (Montifringilla, Pyrgilauda, and Onychostruthus) has its center of distribution on the Tibetan plateau, with six out of seven species in the genera occurring there. Phylogenetic relationships among these six species of three genera have been studied based on DNA sequence data obtained from the mitochondrial cytochrome b gene and the nuclear myoglobin gene. The results support monophyly of the snow finch complex group and three major evolutionary lineages are recognized. The first clade consists of ruficollis, blanfordi, and davidiana. These three taxa are sometimes placed in their own genus, Pyrgilauda, and the DNA data supports this. The three taxa nivalis, henrici, and adamsi have traditionally been placed in the genus Montifringilla, and they group together strongly in the present analysis. The results further suggest that nivalis and adamsi are more closely related to each other than are nivalis and henrici, despite that the latter two are often regarded as conspecific. The third distinct lineage within the snow finch complex consists of taczanowskii, which has been placed its own genus, Onychostruthus. This taxon has a basal position in the phylogenetic tree and is sister to all other snow finches. We estimated that taczanowskii split from the other taxa between 2 and 2.5 mya, i.e., about the time for the most recent uplift of the Tibetan plateau, "the Tibet movement", 3.6-1.7 mya. Cladogenesis within the Montifringilla and Pyrgilauda clades seems to be contemporary with the second phase of "Tibet movement" at 2.5 mya and the third phase at 1.7 mya and "Kunhuang movement" in 1.5-0.6 mya. The dramatic climatic and ecological changes following from the uplift of the Tibetan plateau, together with the cyclic contraction and expansion of suitable habitats during the Pleistocene, are probably the most important factors for the cladogenesis in snow finch complex.     

Dating the arthropod tree based on large-scale transcriptome data

Molecular sequences do not only allow the reconstruction of phylogenetic relationships among species, but also provide information on the approximate divergence times. Whereas the fossil record dates the origin of most multicellular animal phyla during the Cambrian explosion less than 540 million years ago(mya), molecular clock calculations usually suggest much older dates. Here we used a large multiple sequence alignment derived from Expressed Sequence Tags and genomes comprising 129genes (37,476 amino acid positions) and 117 taxa, including 101 arthropods. We obtained consistent divergence time estimates applying relaxed Bayesian clock models with different priors and multiple calibration points. While the influence of substitution rates, missing data, and model priors were negligible, the clock model had significant effect. A log-normal autocorrelated model was selected on basis of cross-validation. We calculated that arthropods emerged ~600 mya. Onychophorans (velvet worms) and euarthropods split ~590 mya, Pancrustacea and Myriochelata ~560 mya, Myriapoda and Chelicerata ~555 mya, and 'Crustacea' and Hexapoda ~510 mya. Endopterygote insects appeared ~390 mya. These dates are considerably younger than most previous molecular clock estimates and in better agreement with the fossil record. Nevertheless, a Precambrian origin of arthropods and other metazoan phyla is still supported. Our results also demonstrate the applicability of large datasets of random nuclear sequences for approximating the timing of multicellular animal evolution.     

An analysis of interspecific relationships ofSaguinus based on cranial measurements

The interspecific relationships of the following nine forms ofSaguinus were analyzed applying the multivariate analysis to the cranial measurements;S. oedipus, S. geoffroyi, S. leucopus, S. nigricollis, S. fuscicollis, S. labiatus, S. mystax, S. midas midas, andS. midas niger. Penrose's size distance was used to express the size factor among the nine forms; and for the shape factor, Q-mode correlation coefficients were utilized. The shape distance betweenS. oedipus andS. geoffroyi was almost equal to that betweenS. nigricollis andS. fuscicollis which are recognized as different species based on biogeographical evidence. Furthermore, the Penrose's size distance betweenS. oedipus andS. geoffroyi was quite large. Therefore, the results of this study support the hypothesis thatS. oedipus andS. geoffroyi are valid species. The analysis of the phylogenetic relationships among the nine forms was based on the shape factor only. The forms were divided into two main clusters: (1)S. oedipus, S. geoffroyi, andS. leucopus; (2)S. nigricollis, S. fuscicollis, S. labiatus, S. mystax, S. midas midas, andS. midas niger. In the former cluster,S. oedipus was more closely related toS. geoffroyi than either was toS. leucopus. The latter cluster was subdivided in two subclusters based on the degree of their affinity: (2a)S. nigricollis, S. fuscicollis, S. labiatus, andS. mystax; and (2b)S. midas midas andS. midas niger. In the former subcluster, [S. nigricollis, S. fuscicollis] and [S. labiatus, S. mystax] were classified into clusters, respectively. The ancestor of theS. nigricollis group differentiated intoS. oedipus, S. geoffroyi, andS. leucopus with the narrowing of the maxilla in the facial region, andS. midas midas andS. midas niger with the downward movement of rhinion.     

Field observations of the golden-mantled tamarin, Saguinus tripartitus, on the Río Curaray, Peruvian Amazonia

During a primatological survey on the Río Curaray in north-eastern Peruvian Amazonia, observations on the ecology and behaviour of the golden-mantled tamarin, Saguinus tripartitus, were made. Two groups consisting of 6 and 9 individuals were observed. The diet of one group that was observed in some detail consisted of fruit, insects (tettigoniid orthopterans) and gums. Patterns of height use were very similar to those observed in saddle-back tamarins, Saguinus fuscicollis. This similarity and the lack of evidence for sympatry with either S. fuscicollis or S. nigricollis lead to the suggestion that S. tripartitus should be reconsidered as a subspecies of S. fuscicollis rather than a species on its own; alternatively, other subspecies of S. fuscicollis should be raised in taxonomic rank.     

Historical biogeography of tamarins,genus Saguinus: the molecular phylogenetic evidence

Hypotheses of the historical biogeography of tamarins (genus Saguinus) based on variation in coat colors and body size are tested using phylogenetic relationships inferred from mitochondrial DNA (mtDNA) sequence data. Samples from all 12 species of Saguinus and several subspecies are included in the analysis. Approximately 1,200 bases of mtDNA sequence from the cytochrome b and D-loop regions are reported for the tamarins and several outgroup taxa. Parsimony analysis of the mtDNA sequence data reveals Saguinus to be a monophyletic taxon composed of two major clades: one, the Small-bodied clade, contains S. nigricollis, S. tripartitus, and S. fuscicollis, and the other, the Large-bodied clade, contains the other nine species. The phylogenetic relationships among tamarins inferred from the mtDNA sequence data reject previous hypotheses for the historical biogeography of tamarins and suggest different dispersal routes for this group of New World monkeys. The molecular data suggest that tamarins dispersed across South America in two major waves from an origin somewhere south of the Amazon. One wave moved in a westerly direction, whereas the other moved in a northeastern direction toward the Amazon delta and then west along the northern portion of the continent into northern Colombia and Panama. Am J Phys Anthropol 108:65–89, 1999. © 1999 Wiley-Liss, Inc.     

Molecular systematics, zoogeography, and evolutionary ecology of the atlantic parrotfish genus Sparisoma

Parrotfishes of the genus Sparisoma (Scaridae) are ecologically important tropical reef fishes restricted to the Atlantic Ocean. We investigated phylogenetic relationships among the eight extant species within this genus using mitochondrially encoded 12S and 16S ribosomal genes. Our molecular data support the view that (i) Sparisoma originated approximately 14-35 million years ago (mya), probably in the tropical western Atlantic, off Brazil; (ii) there have been at least four discrete bouts of cladogenesis within the genus, with the most recent one ( approximately 2.8-5.6 mya) involving four events in both the east and the west Atlantic and across the Atlantic; and (iii) the genus invaded the eastern Atlantic on two different occasions, probably by at least two different routes. The data also offer support for Bellwood's ideas concerning the evolutionary changes in adult feeding patterns and habitat use within Scarids. Specifically, they support the evolutionary position of the ecological traits of Sparisoma as intermediate within the family.     

A biogeographical analysis of Muhlenbergia (Poaceae: Chloridoideae: Cynodonteae: Muhlenbergiinae)

A phylogeny based on the analysis of six DNA sequence markers (ITS, ndhA intron, rpl32-trnL, rps3, rps16 intron, and rps16-trnK) is used to infer ancestral areas and divergence times, and reconstruct the biogeographical history and evolution of 150 of the 183 (82%) species of Muhlenbergia. Our results suggest that the genus originated 9.3 mya in the Sierra Madre (Occidental and Oriental) in Mexico, splitting into six lineages: M. ramulosa diverging 8.2 mya, M. subg. Muhlenbergia at 5.9 mya, M. subg. Pseudosporobolus at 5.9 mya, M. subg. Clomena at 5.4 mya, M. subg. Bealia at 4.3 mya, and M. subg. Trichochloa at 1 mya, each of these with a high probability of Sierra Madrean origin. Our results further suggest that founder-event speciation from Sierra Madre to South America occurred independently multiple times in all five subgenera during the Pleistocene and late Pliocene. One long-distance dispersal event most likely originating from Central or Eastern North America to East and Central Asia occurred 1.6–1 mya in M. subg. Muhlenbergia. In our cladogram, members of M. subg. Trichochloa show little genetic resolution, suggesting very low levels of divergence among the species, and this may be a consequence of rapid radiation.     

Mitochondrial phylogeny, taxonomy and biogeography of the silvered langur species group (Trachypithecus cristatus)

With a distribution ranging from mainland Southeast Asia to the Sunda region, the silvered langur species group is the most widely distributed species complex of the genus Trachypithecus. However, the systematic classification of its members and the phylogenetic relationships among them are less understood, leading to different classification schemes and proposed distribution zones. To address these issues, we sequenced a 573 bp long fragment of the mitochondrial cytochrome b gene from 115 silvered langurs (68 individuals from known origin). According to our data, five monophyletic clades were detected, which refer to the five taxa auratus, cristatus, germaini, margarita and mauritius. The phylogenetic relationships among them are not well resolved, indicating a radiation-like splitting event, which was estimated to have occurred about 0.95-1.25 mya. Within T. cristatus, two major clades were detected, with one comprising specimens from Sumatra, Borneo and the Natuna archipelago, and the other solely individuals from the Malaysian peninsula. According to our findings, we propose to rank all five taxa as distinct species. While T. auratus, T. germaini, T. margarita and T. mauritius seem to be monotypic, T. cristatus should be split into two subspecies, with the Malaysian form being described as new form here. From a phylogeographic perspective, the species group most likely originated on Java. During the early Pleistocene, its range was expanded to the Malaysian peninsula and to the Southeast Asian mainland. Later on, the Malaysian form colonised further regions of the Sunda region, including Sumatra, Borneo and the Natuna archipelago.     

Historical biogeography of the widespread macroalga Sargassum (Fucales,Phaeophyceae)

Sargassum is a cosmopolitan brown algal genus spanning the three ocean basins of the Atlantic, Pacific and Indian Oceans, inhabiting temperate, subtropical and tropical habitats. Sargassum has been postulated to have originated in the Oligocene epoch approximately 30 mya according to a broad phylogenetic analysis of brown macroalgae, but its diversification to become one of the most widespread and speciose macroalgal genera remains unclear. Here, we present a Bayesian molecular clock study, which analyzed data from the order Fucales of the brown algal crown radiation (BACR) group to reconstruct a time-calibrated phylogeny of the Sargassum clade. Our phylogeny included a total of 120 taxa with 99 Sargassum species sampled for three molecular markers – ITS-2, cox3 and rbcLS – calibrated with an unambiguous Sargassaceae fossil from between the lower and middle Miocene. The analysis revealed a much later origin of Sargassum than expected at about 6.7 mya, with the genus diversifying since approximately 4.3 mya. Current geographic distributions of Sargassum species were then analyzed in conjunction with the time-calibrated phylogeny using the dispersal-extinction-cladogenesis (DEC) model to estimate ancestral ranges of clades in the genus. Results strongly support origination of Sargassum in the Central Indo-Pacific (CIP) region with subsequent independent dispersal events into other marine realms. The longer history of diversification in the ancestral CIP range could explain the much greater diversity there relative to other marine areas today. Analyses of these dynamic processes, when fine-tuned to a higher spatial resolution, enable the identification of evolutionary hotspots and provide insights into long-term dispersal patterns.     

Interspecific variation of scent-marking behaviour in wild tamarins, Saguinus mystax and Saguinus fuscicollis.

The scent-marking behaviour of sympatric moustached, Saguinus mystax, and saddle-back tamarins, Saguinus fuscicollis, was compared in order to explore interspecific differences and potential sources of variation. The author examined basic patterns of scent marking (types, intensity, complexity), substrate use (type, orientation, height), and social patterning of scent marking in three groups of S. mystax and one group of S. fuscicollis at the Estación Biológica Quebrada Blanco, Peruvian Amazonia. S. mystax and S. fuscicollis differed significantly in the relative frequency of different types, and in the intensity and complexity of scent marking. Only S. fuscicollis showed allomarking. They also differed significantly in the type, orientation and height of substrates used for scent marking which corresponded to general differences in substrate use. In S. fuscicollis, but very rarely in S. mystax, two or more group members marked the same site sequentially or simultaneously. 'Collective scent marking', i.e. simultaneous scent marking by most or all group members, occurred only in S. fuscicollis. Since both tamarin species live sympatrically in mixed-species groups, ecological factors are unlikely to account for the differences found in scent-marking behaviour (except for differences in substrate use). They probably relate to as yet unknown differences in social and reproductive strategies of the two species.     

A phylogeographic investigation of the kelp genus Laminaria (Laminariales,Phaeophyceae), with emphasis on the South Atlantic Ocean

The genus Laminaria has a wide distribution range compared with other kelp genera because it is found in both the North and the South Atlantic, on both sides of the North Pacific, as well as in the Mediterranean. Hypotheses behind this biogeographical pattern have been discussed by several authors but have not yet been fully evaluated with time‐calibrated phylogenies. Based on the analysis of four molecular markers (ITS2, rbcL, atp8 and trnWI), our goal was to reassess the Laminaria species diversity in South Africa, assess its relationship with the other species distributed in the South Atlantic and reconstruct the historical biogeography of the genus. Our results confirm the occurrence of a single species, L. pallida, in southern Africa, and its sister relationship with the North Atlantic L. ochroleuca. Both species belonged to a clade containing the other South Atlantic species: L. abyssalis from Brazil, and the Mediterranean L. rodriguezii. Our time‐calibrated phylogenies suggest that Laminaria originated in the northern Pacific around 25 mya, followed by at least two migration events through the Bering Strait after its opening (~5.32 mya). Today, the first is represented by L. solidungula in the Arctic, while the second gave rise to the rest of the Atlantic species. The colonization of the North Atlantic was followed by a gradual colonization southward along the west coast of Europe, into the Mediterranean (~2.07 mya) and two recent, but disconnected, migrations (~1.34 and 0.87 mya) across the equator, giving rise to L. abyssalis in Brazil and L. pallida in southern Africa, respectively.     

A cladistic analysis of interspecific relationships ofSaguinus

The dental and cranial morphologies of all species ofSaguinus, S. oedipus, S. geoffroyi, S. leucopus, S. nigricollis, S. fuscicollis, S. labiatus, S. mystax, S. imperator, S. bicolor, andS. midas are examined. The following hypotheses are developed by cladistic methodology, using only synapomorphic characters to assess the interspecific relationships ofSaguinus.Saguinus are divided into two main groups; one consists ofS. oedipus, S. geoffroyi, andS. leucopus, and the other includesS. inustus, S. nigricollis, S. fuscicollis, S. labiatus, S. mystax, S. imperator, S. bicolor, andS. midas. In the former group,S. oedipus is more closely related toS. geoffroyi than either is toS. leucopus. In the latter group,S. labiatus, S. mystax, andS. imperator are classified into one group, andS. bicolor andS. midas form one monophyletic group.     

Glass in the water: Molecular phylogenetics and evolution of Indian glassy perchlets (Teleostei: Ambassidae)

Glassfishes of the family Ambassidae, comprising around 50 species, are distributed in the Indo‐West Pacific where they inhabit marine, estuarine, and freshwater ecosystems. We investigated for the first time the molecular phylogenetic and evolutionary relationships of this group using a combined dataset of mitochondrial and nuclear genes, particularly focusing on the taxa occurring in the Indian subcontinent. Results revealed that marine and freshwater genera of Ambassidae diverged during the Paleocene (~62 mya). The enigmatic monotypic genus Chanda is nested within the larger clade currently recognized as Parambassis, indicating its paraphyly. Based on cleared and stained osteological preparations and phylogenetic placement of Chanda nama, we hypothesize that the elongated and protruding lower jaw is an autapomorphic character that might have evolved for the lepidophagous habit of the species. The southern Indian species of Parambassis, Parambassis dayi, and Parambassis thomassi, which formed a monophyletic group, probably diverged from other species of Parambassis and Chanda nama around the Eocene (~42 mya) and can potentially be recognized as a distinct genus in view of the apomorphic characters such as the presence of serration on the ventral fringe of interopercle, densely serrated palatine and ectopterygoid, and the presence of more than 30 serrations along the lower preopercle and the posterior edge. Our analysis provides new insights into the evolution and phylogenetic relationships of glassy perchlets, including detailed relationships among the Indian species within this family.     

Plumage based classification of the bowerbird genus Sericulus evaluated using a multi-gene, multi-genome analysis

Past classifications of taxa within the bowerbird genus Sericulus (family: Ptilonorhynchidae) conflict since the discovery of hybrids identified though male plumage characteristics. We use molecular data to help define species within this genus, and by estimating a phylogeny, test for lability in the evolution of male plumage patterns. Because this genus includes the most brightly colored bowerbird species, and is hypothesized to be the basal genus of the avenue building bowerbird clade, the organization of the four taxa within this genus is especially important in understanding how bowerbird plumage coloration evolved. Analyses of two mitochondrial and six nuclear gene regions confirm the basal placement of Sericulus in the avenue building bowerbirds and Sericulus monophyly, and suggests the Australian S. chrysocephalus is the basal Sericulus species. Our analysis additionally supports the existence of three New Guinea Sericulus species, contrary to some previous plumage based classifications, as they are genetically equidistant from each other. Molecular and geographic data of New Guinea are consistent suggesting a series of speciation events starting approximately 3.7-4.3MYA leading to four extant Sericulus species. The absence of resolution within the New Guinea species precludes any statements of trait lability, but does suggest that traits under high selection pressures may not accurately indicate species level distinctions within this genus.     

Variations in dental measurements between Saguinus species and their systematic relationships.

Multivariate analysis is applied to dental measurements of Saguinus species to analyse their systematic relationships. The shape distance between Saguinus midas midas and S. midas niger is larger than that between S. nigricollis and S. fuscicollis, both of which are generally recognized as valid species. In dental form, S. bicolor is the closest relative of S. midas. S. inustus is not linked to S. leucopus. S. geoffroyi and S. leucopus, as S. inustus shows closer affinity with S. labiatus and S. mystax than with the former 3 species.     

Evolutionary systematics in African gerbilline rodents of the genus Gerbilliscus: inference from mitochondrial genes

Gerbilliscus has recently been proposed as an endemic African rodent genus distinct from the Asian Tatera. A molecular phylogeny of the genus, including nine species from southern, western and eastern Africa, is presented here based on the analysis of the cytochrome b and 16S mitochondrial genes. With an adequate taxonomic sampling over a wide geographic range, we here provide a clear picture of the phylogenetic relationships between species and species groups in this genus. Three distinct clades were resolved, corresponding to major geographical subdivisions: an eastern clade that possibly diverged first, then a southern and a western clades which appeared later. We suggest two possible hypotheses concerning the dispersal of the genus across Africa, considering also the patterns of karyotypic variation. Finally, we discuss the taxonomic status of G. gambianus and the relationships between Gerbillurus and Gerbilliscus, as previous studies have suggested that the former should be included in the latter. Our data seem to support the synonymy of the two taxa and suggest that Gerbillurus and Gerbilliscus lineages diverged from a common ancestor appeared in eastern Africa.     

Vertical clinging, small body size, and the evolution of feeding adaptations in the Callitrichinae.

Primates of the subfamily Callitrichinae (Callimico, Callithrix, Leontopithecus, and Saguinus) are small-bodied New World monkeys (105-700 g) possessing clawlike nails on all manual and pedal digits excluding the hallux. Specialized nails in these genera serve a critical function in feeding by enabling tamarins and marmosets to cling to trunks and other large vertical supports while exploiting food resources. Within the subfamily, there is evidence of at least four distinct large-branch feeding patterns. These include (1) seasonal exudate feeding and occasional trunk foraging (many Saguinus spp.); (2) exploitation of bark surface insects and the use of trunks as a platform to locate terrestrial prey (Saguinus fuscicollis, S. nigricollis, and Callimico); (3) manipulative foraging and bark stripping to locate concealed insects and small vertebrates (Leontopithecus); and (4) tree gouging and year-round exudate feeding (many Callithrix). Large-branch feeding and the use of vertical clinging postures appear to be a primary adaptation among virtually all callitrichines, distinguishing them ecologically from other platyrrhine taxa. Given the anatomy and behavior of extant callitrichines, Saguinus appears to be the most ecologically generalized member of this subfamily, and species of this genus may provide useful models for reconstructing the feeding and foraging adaptations of early callitrichines.     

The range of the golden-mantle tamarin, <Emphasis Type="Italic">Saguinus tripartitus</Emphasis> (Milne Edwards, 1878): distributions and sympatry of four tamarin species in Colombia,Ecuador, and northern Peru

A detailed understanding of the range of the golden-mantle tamarin, Saguinus tripartitus (Milne Edwards, 1878), in Amazonian Peru and Ecuador is of particular relevance, not only because it is poorly known but also because it was on the basis of its supposed sympatry with the saddleback tamarin (S. fuscicollis lagonotus) that Thorington (Am J Primatol 15:367-371, 1988) argued that it is a distinct species rather than a saddleback tamarin subspecies, as was believed by Hershkovitz (Living new world monkeys, vol I. The University of Chicago Press, Chicago, 1977). A number of surveys have been carried out since 1988 in the supposed range of S. tripartitus, in both Ecuador and Peru. Here we summarize and discuss these issues and provide a new suggestion for the geographic range of this species; that is, between the ríos Napo and Curaray in Peru and extending east into Ecuador. We also review current evidence for the distributions of Spix's black-mantle tamarin (S. nigricollis nigricollis), Graells' black-mantle tamarin (S. n. graellsi), and the saddleback tamarin (S. fuscicollis lagonotus), which are also poorly known, and examine the evidence regarding sympatry between them. We conclude that despite the existence of a number of specimens with collecting localities that indicate overlap in their geographic ranges, the fact that the four tamarins are [corrected] of similar size and undoubtedly very similar in their feeding habits militates strongly against the occurrence of sympatry among them.