The question of sympatry is central to understanding the taxonomic status of S. tripartitus. There are three other tamarins species in the region, which, in the literature, have been considered to be partially sympatric.
S. fuscicollis lagonotus (Jiménez de la Espada, 1870)
In Peru, this saddleback tamarin occurs south of the Ríos Napo and Curaray, east to the Río Amazonas, and north of the Río Marañón (Aquino and Encarnación 1994). Hershkovitz (1977) and Tirira (2007) indicated that the western limit to its range was the Río Santiago, a north (left)-bank tributary of the Marañón. In their text, Aquino and Encarnación (1994, p. 14) indicated its occurrence further west and south to the Río Chinchipe, although their map (p. 108) takes it only as far west as the basin of the Río Cenepa [both also north (left)-bank tributaries of the Marañón] (Fig. 4). The Peruvian range is quite well documented in terms of collecting localities, with Hershkovitz (1977) listing specimens from the Ríos Nanay, Tigre, Pastaza, and upper Santiago. Significantly, Hershkovitz (1977) gives no localities north of the Río Curaray [one at the mouth of the Curaray was collected by the Olalla Bros.1926 and presumably from the south (right bank) of the river (Heymann 2000)]. Its type locality is based on syntypes from the three localities; two in Ecuador: “La Coca, Río Napo,” and “Humuyacu, Río Napo”, nearby [both plotted as locality 63, Fig. XIII.4, p. 916, in Hershkovitz (1977)] and Tarapoto in Peru, a tributary of the left bank of the Napo near and on the opposite bank of the mouth of the Curaray [locality 79, Fig. XIII.4, p. 916, in Hershkovitz (1977)]. Taropoto is also a locality for S. n. graellsi, as is the Río Curaray, and the reason Hershkovitz (1982) indicated sympatry between S. n. graellsi and S. f. lagonotus. If we follow the assertion of de la Torre (1996), it does not occur in eastern Ecuador between the Ríos Curaray and Tiputini, where S. tripartitus is present. Albuja (1994), on the other hand, said that S. f. lagonotus and S. tripartitus were both present in the Tiputini and Tambococha localities he reported (see Table 2). The range map of S. f. lagonotus provided by Tirira (2007) covers the entire range of S. tripartitus in Ecuador, and Tirira stated (p. 119), without explanation or reference, that the two tamarin species are sympatric in the north of the range of tripartitus near the Río Napo.
It was on the basis of supposed sympatry with S. f. lagonotus (through apparently coincident collecting localities) that Thorington (1988) argued that S. tripartitus should be considered a species. The key locality for Thorington’s argument of sympatry, however, was Puerto Indiana at the mouth of the Napo, but, as discussed above, Aquino and Encarnación (1996) failed to find any evidence that S.
tripartitus ever occurred there. Albuja (1994), however, noting that S. f. lagonotus was present at the two localities he recorded for S.
tripartitus (see Table 2), supported Thorington’s (1988) thesis that S. tripartitus should be considered a distinct species. De La Torre (1996), Kostrub (1997), and Heymann et al. (2002), on the other hand, found no evidence of sympatry. In Ecuador, they would apparently be sympatric south of the Río Napo, but de la Torre (1996) stated that: “To date, there are no reports of sites where any two of the (Ecuadorian) tamarin species live in sympatry” (p. 88). She observed S. f. lagonotus south of the Río Napo in areas close to the Jatun Sacha Research Station, the Añangococha Lake, and along the Pompeya Sur–Río Iro highway as far south as, but not south of, the Río Indillama, a south-bank tributary of the Napo. S. tripartitus occurs south of the Río Indillama to the Río Curaray. Heymann et al. (2002) recorded a clear separation of S. tripartitus (left bank of the Río Curaray) and S. f. lagonotus (right bank), and concluded that “The ecological similarity (of S. tripartitus) with S. fuscicollis and the lack of hard evidence for sympatry argue against it being a separate species” (p. 198). They agreed with Thorington (1988), however, in indicating that if S. tripartitus should be maintained as a distinct species, other S. fuscicollis subspecies should also be considered full species.
Although Aquino and Encarnación (1994) indicated that S. n. graellsi occurred south of the lower Napo to the Río Nanay, we believe that it is improbable (see below). We believe that the geographic ranges of S. f. lagonotus and S. n. graellsi do not overlap. During a survey in 2007, Matauschek (in prep.) encountered only S. f. lagonotus at all locations he visited on the right bank of the Napo, south of the Curaray in Peru. He saw both wild animals and pets (in three different villages). Also, local people clearly identified the resident tamarins on the pictures shown to them. There was no evidence for S. f. lagonotus occurring on the right bank of the Napo above the mouth of the Curaray.
S. nigricollis nigricollis (Spix, 1823)
Information on the distribution of Spix’s black-mantled tamarin, S. n. nigricollis, is confused and conflicting. Its type locality is “the north bank of the Río Solimões, near São Paulo de Olivença, Amazonas, Brazil”, and Hershkovitz (1977, 1982) placed it between the Ríos Solimões-Amazonas and Içá-Putumayo, at least as far west as the mouth of the Río Napo. Encarnación et al. (1990) and Aquino and Encarnación (1996) suggested its occurrence west from there along the left (north) bank of the Río Napo in Peru, upstream to the Ríos Lagartococha and Güeppi on the border with Ecuador, where according to Hershkovitz (1982) it is replaced by S. nigricollis graellsi. In a recent exploration along the Río Napo, C. Matauschek (in prep.) encountered S. n. nigricollis on the north bank of the Napo opposite San Felipe, a village 270 km down the Rio Napo from the Ecuadorian border, and from there further east on different locations north of the Napo and the Amazon (for example, the Ríos Ampiyacu and Apayacu, see Fig. 2). Montenegro and Escobedo (2004) saw black-mantle tamarins, which they presumed were S. n. nigricollis, not graellsi, between the Ríos Amazonas and Putumayo in Peru, in numerous localities they surveyed in the basins of the Río Yaguas, a south (right-bank) tributary of the Putumayo, and the Ríos Apayacu and Ampiyacu, both (left-bank) tributaries of the Amazonas (see Fig. 1).
In Colombia, Hernández-Camacho and Cooper (1976) and Defler (1994) reported that it occurs north of the Río Putumayo to the Río Caquetá and east to the Brazilian border, indicating its, as yet undocumented, presence between the Ríos Japurá and Iça in Brazil (Hershkovitz 1977, 1982). Evidence for its occurrence north of the Río Putumayo in Colombia is sparse, however. As discussed in detail by Defler (1994, 2004), the occurrence of S. n. nigricollis in Puerto Leguízamo (Fig. 2) was based on a specimen in the collection of the Instituto de Ciencias Naturales (ICN), registered as being from the “Quebrada El Hacha”, a left (north)-bank affluent of the Putumayo (collectors H. Granados and H. Arévalo). A number of specimens in the same collection are labeled as from between the Ríos Caqueta and Putumayo. Hernández-Camacho and Cooper (1976) noted, however, that “the population of the upper Putumayo River has a dull and brownish cast to the lower back and hind limbs, as well as some grizzled yellow and black in the saddle” and concluded that: “This population is thus more reminiscent of S. fuscicollis than is the lower Putumayo and Leticia population, which has a rich ferruginous cast to the lower back and hind limbs and no yellowish tones in the saddle area” (pp. 37–39). Evaluating this, Defler (1994, 2004) concluded that the tamarins thought to be S. n. nigricollis to the north of the Río Putumayo are, in fact, dull specimens of S. fucicollis fuscus, and recorded that Philip Hershkovitz, in a personal communication to Defler, believed the same.
South of the Río Putumayo, the range of S. n. nigricollis perhaps overlaps with S. tripartitus between the Ríos Yuvineto and Güeppi, as argued by Encarnación et al. (1990) and Aquino and Encarnación (1996). Bravo and Borman (2008) carried out mammal surveys at five sites between the Ríos Napo and Putumayo in Ecuador and Peru: west of the middle Río Lagartococha (Garzacocha), on the south (right) bank of the upper Río Güeppi (Güeppicillo) (both in the Cuyabeno Faunal Production Reserve in Ecuador), on the right (east) bank of the Río Lagartacocha (Redondococha) in the proposed Airo Pai Communal Reserve (Peru), the south (right) bank of the Río Güeppi in the proposed Güepi National Park (Peru), and on the upper reaches of the Río Peneya (Aguas Negras), a right-bank tributary of the Putumayo (Peru) (see Fig. 2). Bravo and Borman (2008) reported S. nigricollis in all these sites. They made no mention of subspecies, but published a photograph of an infant/juvenile (their Fig. 8A) that appears to be S. n. nigricollis, not graellsi. They made no mention of S. tripartitus.
S. nigricollis graellsi (Jiménez de la Espada, 1870)
Graells’ black-mantle tamarin occurs in the upper Amazon, in southern Colombia, eastern Ecuador, and northeastern Peru. Its range is not well known, however, and our interpretation of the current evidence indicates that it is probably more restricted than is indicated by Hershkovitz (1977, 1982). The type locality is “banks of Río Napo near Tarapoto, and Destacamento, near confluence with the Marañón, Loreto, Peru” (Hershkovitz 1977). Cabrera (1958) restricted it to Tarapoto, and Hershkovitz (1977) restricted it further to “right bank Río Napo, opposite Tarapoto and above the mouth of the Río Curaray” (locality 79, p. 629). Destacamento is plotted by Hershkovitz as being on the right bank of the Río Napo, just above its mouth (locality 91, map, p. 626). The Río Tarapoto is a left-bank (north) tributary of the Río Napo.
Hernández-Camacho and Cooper (1976) wrote that in Colombia, it occurs south from the right (south) bank of the upper Río Caquetá to the ríos Sucumbíos and Putumayo on the border with Ecuador. They recorded that it could also be found in the neighborhood of Puerto Asís on the upper Putumayo, east to the vicinity of Puerto Leguízamo, north bank of the Río Putumayo. As discussed above for S. n. nigricollis, these authors indicated a probability that the form graellsi is sympatric with S. n. nigricollis in the region of Puerto Leguízamo, and Hernández-Camacho and Cooper (1976) and Hernández-Camacho and Defler (1989) and Defler (1994) listed graellsi as a full species as a result. The conclusion of Defler (1994, 2004) and Hershkovitz (pers. comm. to Defler 1994, 2004), however, was that the specimens considered to be S. n. nigricollis were in fact just dull-colored S. fuscicollis fuscus. In his most recent assessment, Defler (2004) listed graellsi as a subspecies of S. nigricollis. Genetic data (Matauschek et al., submitted) support this assessment. Groves (2001, 2005) maintained graellsi as a full species based on Hernández-Camacho and Cooper’s (1976) supposition of its sympatry with nigricollis.
Hershkovitz (1982) argued that there is no definite evidence for S. n. graellsi occurring north of Ecuador and suggested that black-mantle tamarins reported by Hernández-Camacho and Cooper (1976) may be either S. n. nigricollis or S. n. hernandezi. He restricted its northern limit to the Ríos Putumayo and Sucumbíos (Río San Miguel), indicating as such that it does not occur in Colombia at all.
According to Hershkovitz (1982), in Ecuador, S. n. graellsi extends throughout a large part of the Amazon region, south from the Ríos Putumayo and San Miguel, west to the foothills of the Andes. The altitudinal range is between 100 and 1,000 m (Hershkovitz 1982). S. n. graellsi is supposed to occur north of the Río Napo in Ecuador, and to extend east only as far the ríos Güepi and Lagartococha on the frontier with Peru (Hershkovitz 1982), where it should be replaced by S. n. nigricollis (see Hershkovitz 1982; Aquino and Encarnación 1996). However, in Peru, Matauschek (in prep.) encountered tamarins north of the Napo between Pantoja and Torres Causana that phenotypically matched S. n. graellsi exclusively. Consequently the border between S. n. graellsi and S. n. nigricollis must lie further southeast in Peru. The only larger river in this area is the Río Tamboryacu. The river itself seems unlikely to form a barrier for the tamarins because of its course, which is more or less parallel to the Río Napo, leaving much space for dispersal between the Putumayo and the Tamboryacu. It seems more likely that the large area of low, seasonally flooded várzea forest surrounding the vast stream network of the Tamboryacu could form a barrier for the tamarins, which are scarce and rarely seen in this type of forest. The approximate area is marked in white with a question mark in Fig. 4.
It has been recorded recently in a number of localities in northern Ecuador between the Ríos Napo and Putumayo, including the basins of the ríos Aguarico, Cuyabeno, and Pacuyacu (S. de la Torre, in litt. 1996). Borman (2002) recorded S. nigricollis (presumably graellsi) at Sinangoe on the Río Cofanes (a left-bank tributary of the upper Aguarico) and from the upper Río Bermejo (a right-bank tributary of the Putumayo) in Ecuador. However, it has not been found in the Yasuní National Park, covering the basin of the Río Yasuní, where it would seem that only S. tripartitus and, according to Albuja (1994) but not de la Torre (pers. obs. 1996), S.
fuscicollis lagonotus occur.
Hershkovitz (1977) suggested that the range in Ecuador may extend as far south as the right bank of the upper Río Santiago, although in his later publication (1982), he was more conservative, giving the north (right) bank of the Río Pastaza as the limit. The specimens from the Ríos Pastaza and Tigre are from their uppermost reaches in Ecuador. Hershkovitz (1982) showed the four localities, numbers 19–22, on his Fig. 3 (p. 653), and listed them as follows:
Yana Rumi (Río), mouth of Río Pindo Yacu, 1°38′S, 76°59′W. R. Olalla, December, 1934, February, 1935;
Pindo Yacu (Río), joins Río Cunambo, upper Río Tigre at 2°08′S, 76°04′W. R. Olalla, October, 1934, above junction with Río Cunambo at 250 m;
Pastaza (Río), 2°05′S, 500 m. C. S. Webb; and
Capahuara or Capihuara (Río), mouth at Río Pastaza, 2°03′S, 76°51′W. R. Olalla, November 1934, above mouth at 300 m.
These are the only records south of the Río Napo in Ecuador, and the reason Hershkovitz (1982) tentatively extended the range to the entire lowland Amazonian region of Peru between the ríos Napo and Pastaza to the ríos Amazonas and Marañón. Both de la Torre (1996) and Tirira (2007) restrict S. n. graellsi to the north of the Napo in Ecuador. Tirira (2007) discounted the Pastaza and Tigre records for this species listed by Hershkovitz (1982), saying only that: “The validity of certain populations to the south of the Río Napo, in the provinces of Orellana and Pastaza, is motive for controversy” (p. 118).
Aquino and Encarnación (1994) reported, however, that S. n. graellsi has never been found along the ríos Tigre and Pastaza despite a number of primatological surveys along these rivers between 1981 and 1986. They indicated that S. n. graellsi extends eastwards from Ecuador into Peru along the right (south) bank of the Río Napo and that the range in Peru is restricted to the region between the Ríos Nanay and Napo-Curaray. Matauschek (in prep.) could find no evidence for S. n. graellsi along the Río Nanay (Santa María, Diamante Azul) in 2007 and 2008. Castro and Soini (1977) recorded only S. fuscicollis at the Nanay field station, just south of the river on the lower reaches. Aquino et al. (2005) surveyed the Río Aushiri (right-bank affluent of the Napo) in 2005 and in the area between the Ríos Curaray and Nashiño (left-bank affluent of the Curaray) in 2007 and 2008. They found no evidence for the presence of S. n. graellsi, encountering only S. tripartitus.
Hershkovitz (1982) gave just three localities for S. n. graellsi in Peru. Two are type localities quite distant from each other. The third is “Curaray (Río), boca (=mouth) at Río Napo” collected by Olalla and Sons in 1925. Heymann’s (2000) and Heymann et al.’s (2002) finding that S. n. graellsi does not occur along either bank of the Río Curaray puts the Tarapoto and mouth of the Curaray localities (both number 4, p. 655) in doubt. Likewise, Hershkovitz (1977, p. 629) gives the (type) locality of Destacamento as “near confluence with Marañón” but mapped it at the confluence of the Río Napo. The third Peruvian locality of Hershkovitz (1982) is listed as “Destacamento (=Francisco Orellana), Río Napo, at the junction with Río Amazonas” (Hershkovitz 1977, locality 91, p. 626; 1982, locality 5, p. 652). There is another Francisco de Orellana (Puerto), which is at the mouth of the Río Coca, an affluent of the Napo, in Ecuador (Fig. 2), a region where it would seem that S. n. graellsi certainly does occur, and which, suggestively, is also near or at (the same locality as) the type locality of S. f. lagonotus, also described by Jiménez de la Espada. Francisco de Orellana at the mouth of the Río Coca is also known as “Coca”.
If we accept that S. n. graellsi is limited to the north of the Río Napo in Ecuador, does not occur between the Ríos Curaray and Napo in Ecuador or Peru, and does not occur along the right bank of the Curaray in Peru, it is very difficult to accept that it occurs between the lower Río Napo and Río Nanay in Peru. This supposition is either based on erroneous localities (either incorrect labels or incorrect interpretation of them), or, if tamarins considered to be graellsi have been seen there, that they are in fact a similar but distinct taxon.
S. n. graellsi is largely restricted to Ecuador north of the Río Napo, including the basin of the Río Cuyabeno, and probably occurring in Peru between the Ríos Napo and Putumayo west possibly as far the upper reaches of the Río Tamboryacu. Evidence for its presence in Colombia is based on a preserved specimen from the Comisaría of Putumayo, and a number of reliable sightings [for example, on the right bank of the Río Guamués, reported in Moynihan (1976), who said that their appearance conformed to the description S. n. graellsi provided by Hershkovitz (1966); but no specimens were obtained], and captive specimens from Puerto Asís, east to the vicinity of Puerto Leguízamo (Hernández-Camacho and Cooper 1976).
The distribution of S. n. graellsi has yet to be clearly defined. Hernández-Camacho and Cooper (1976) informed that in Colombia between the upper reaches of the Ríos Putumayo and Caquetá, “S. graellsi is undoubtedly sympatric with S. fuscicollis fuscus throughout its range” (p. 39), and this is confirmed by Defler (1994, 2004). It does not occur between the Ríos Curaray and Napo in Peru and Ecuador, and is not, therefore, sympatric with S. tripartitus.