Genetic contributions to dental dimensions in brown-mantled tamarins (Saguinus fuscicollis) and rhesus macaques (Macaca mulatta).

OBJECTIVES: The use of dental metrics in phylogenetic reconstructions of fossil primates assumes variation in tooth size is highly heritable. Quantitative genetic studies in humans and baboons have estimated high heritabilities for dental traits, providing a preliminary view of the variability of dental trait heritability in nonhuman primate species. To expand upon this view, the heritabilities and evolvabilities of linear dental dimensions are estimated in brown-mantled tamarins (Saguinus fuscicollis) and rhesus macaques (Macaca mulatta). MATERIALS AND METHODS: Quantitative genetic analyses were performed on linear dental dimensions collected from 302 brown-mantled tamarins and 364 rhesus macaques. Heritabilities were estimated in SOLAR using pedigrees from each population, and evolvabilities were calculated manually. RESULTS: Tamarin heritability estimates range from 0.19 to 0.99, and 25 of 26 tamarin estimates are significantly different from zero. Macaque heritability estimates range from 0.08 to 1.00, and 25 out of 28 estimates are significantly different from zero. DISCUSSION: Dental dimensions are highly heritable in captive brown-mantled tamarins and free-ranging rhesus macaques. The range of heritability estimates in these populations is broadly similar to those of baboons and humans. Evolvability tends to increase with heritability, although evolvability is high relative to heritability in some dimensions. Estimating evolvability helps to contextualize differences in heritability, and the observed relationship between evolvability and heritability in dental dimensions requires further investigation.

Vocal divergence and discrimination of long calls in tamarins: A comparison of allopatric populations of Saguinus fuscicollis nigrifrons and S. f. lagonotus.

Divergence in vocalizations can reduce gene flow by serving as a premating barrier during secondary contact between previously isolated populations. In primates, vocal divergence in long calls of separated populations has been documented, yet recognition of these differences by the respective populations has seldom been studied in the field. To investigate this issue, we studied populations of two subspecies of saddle-back tamarins (Saguinus fuscicollis nigrifrons and S. f. lagonotus) that are separated by the Amazon River in Peru. We recorded long calls of each subspecies and detected significant differences between the populations in the number of notes per call, duration of calls, and shifts in starting frequency of notes over the length of calls. In addition, a population of S. f. nigrifrons responded more overtly in measures of approach to playback of long calls of its own subspecies compared to long calls of S. f. lagonotus. These results are consistent with the hypothesis that allopatric divergence of long calls might contribute to reproductive isolation of these subspecies of saddle-back tamarins, which adds to growing evidence suggesting full species status for these taxa.

Endocrine monitoring of the ovarian cycle and pregnancy in the saddle-back tamarin (Saguinus fuscicollis) by measurement of steroid conjugates in urine.

Direct measurements of urinary immunoreactive estrone conjugates (E1C) and pregnanediol glucuronide (PdG), were applied to monitoring the ovarian cycle (n = 9) and pregnancy (3 full term pregnancies, 2 mid-term abortions) in Saguinus fuscicollis. During the ovarian cycle, urinary E1C concentrations revealed a high degree of day-to-day variability and appeared to be uninformative in reflecting cyclic ovarian function. In contrast, PdG was a reliable indicator of ovarian cyclicity with excretion patterns corresponding well with plasma progesterone profiles. Luteal phase PdG concentrations were on average 4-7-fold higher than corresponding follicular phase values. On the basis of changes in circulating progesterone, a mean cycle length of 25.7 ±1.0 days with an average follicular phase of 7.1 ± 0.6 days and a mean luteal phase of 18.6 ± 0.7 days, was found (n = 14 cycles). Following conception, both urinary steroid conjugate concentrations increased and elevated levels were maintained beyond the normal luteal phase length, allowing pregnancy to be determined at around day 25-30. During mid- to late pregnancy, PdG levels declined while E1C concentrations continued to be elevated until approximately 6 weeks before parturition when a decrease occurred. Both hormones showed a clear and rapid fall to follicular phase values following termination of pregnancy at either parturition or mid-term abortion. Post partum ovulations (n = 5) occurred on average 17-18 days following birth with four ovulations leading to conceptions. The results demonstrate the potential of urinary steroid conjugate analysis as a practical and reliable method for non-invasive monitoring of reproductive status in the female saddle-back tamarin. © 1995 Wiley-Liss, Inc.

Interspecific relations in a mixed-species troop of moustached tamarins, Saguinus mystax, and saddle-back tamarins, Saguinus fuscicollis (Platyrrhini:Callitrichidae), at the Río Blanco, Peruvian Amazonia.

This study examined the social interactions between moustached tamarins, Saguinus mystax, and saddle-back tamarins, Saguinus fuscicollis, living in a mixed-species troop at the Río Blanco, Peruvian Amazonia, between July 1985 and July 1986. Mixed-species troops were common among the S. mystax and S. fuscicollis populations in the Río Blanco study area; 72% of all sightings of S. mystax and 82% of all sightings of S. fuscicollis were in mixed-speices troops (study group excluded from analysis). In the study group, the two species spent on average 82% of time in association. Interactions were observed at a rate of one per 5 h of observation. Most interactions (96%) were agonistic. About 70% of agonistic interactions occurred at small food resources (crown diameter < 5 m and/or limited number of ripe fruits). Moustached tamarins were always dominant over saddle-back tamarins. Friendly interactions were extremely rare and were restricted to play invitations. Mutual calling was observed in the morning before the two species joined each other and during the day when they became separated. It is concluded that interspecific interactions and mutual calling incur some costs to the associated species but that these costs may be low.

Taxonomic status of Saguinus tripartitus (Milne-Edwards, 1878).

A review of specimens and field notes of Carlos Olalla and his sons showed that they collected Saguinus tripartitus and Saguinus fuscicollis lagonotus at the same place on the right bank of the lower Rio Napo in Peru. Thus, these two forms are sympatric, although they probably occur in different habitats. Therefore, Saguinus tripartitus should be treated as a distinct species, not as a subspecies of Saguinus fuscicollis.

The ecology of seed dispersal in two species of callitrichid primates (Saguinus mystax and Saguinus fuscicollis).

Data collected during a 12-month field investigation of mixed species troops of Saguinus mystax and Saguinus fuscicollis in the Amazon Basin of north-eastern Peru indicate that callitrichid primates play an important role in tropical forest seed dispersal. Moustached and saddle-back tamarins were observed to ingest seeds from a variety of tree and liana species and pass them unharmed. These seeds tended to be large and heavy, and passed through the tamarin digestive tract in one to three hours. Experimental plantings of defecated seeds yielded a germination success rate of 70%. The specific gravity of these seeds (weight/volume) was inversely correlated with passage time and apparently had an indirect influence on the distance that seeds were dispersed from the parent tree. In the case of three preferred fruiting species, Leonia glycycarpa, Pourouma sp., and Hippocrateaceae #283, the present distribution of adult trees closely resembled the pattern of the seed shadow created by Saguinus. Moustached and saddle-back tamarins appeared to be reliable and high-quality dispersal agents for a number of tree and liana species. In this role, they are likely to exert an important influence on the composition, distribution, and regeneration patterns of Amazonian rain forest.

Social influences on estrogen excretion and ovarian cyclicity in saddle back tamarins (Saguinus fuscicollis).

The effects of different social living conditions on estrogen excretion and on the ovarian cycle of saddle back tamarins were investigated. Urinary estrogens were monitored as indices of ovarian cyclicity in groups of adult females living under the following experimental conditions: (1) five parous females, each living with an adult castrated male (in one of the females plasma estradiol and progesterone were also measured); (2) five adult daughters living with their families. Each daughter was then removed from her family and paired with a vasectomized male. After pairing, scent marks collected from the family were introduced daily to one of the daughters and her mate. Scent exposure was then discontinued and hormone excretion measured for several weeks. The remaining four daughters were not exposed to family scent. The females living with castrated males showed urinary estrogen cycles of an average length of 17.5 ± 1.0 days. The plasma estrogen cycle was of the same length. The females studied under condition 2 showed low, noncycling estrogen levels while living in their families. They responded to pairing with an increase in the level of urinary estrogens, and four out of five showed regular estrogen cyclicity. The fifth female exposed to family scent marks after pairing also showed an increase in urinary estrogens. However, as long as scent transfer was maintained, no cycle was observed. Estrogen excretion increased again, and cyclicity commenced when scent transfer was discontinued. It is concluded that ovarian estrogen production is suppressed and cyclicity does not occur as long as daughters live in their families. Release from suppression and perhaps stimulation by the male cause a rapid increase in estrogen levels and the onset of cyclicity. Chemical stimuli produced by the family, perhaps particularly by the mother, may be involved in reproductive suppression.

Population recovery in the moustached tamarin (Saguinus mystax): Management strategies and mechanisms of recovery.

In 1978, 66% of the individuals of Saguinus mystax and 9.5% of Saguinus fuscicollis were cropped from a population at the Yarapa river, Peru. The effects of cropping on the remaining tamarin population were evaluated by conducting censuses in 1981 and 1982 and by trapping and release of Saguinus mystax in 1981. Three hundred kilometers of trail were covered in the censuses, and all the groups within the 1.9-km2 study area were located. Within three years after cropping, the population of S. mystax had increased by 124%, more than double the size left in 1978. Increased reproductive rate, early breeding, and reduced infant mortality contributed to the recovery. On the other hand, S. fuscicollis had decreased by 12% in the three years following the cropping but had increased in the fourth year to a level slightly below the precropping density. The cropping of more S. mystax than S. fuscicollis might have contributed to the decline of the latter. The cropping of a sizable percentage of S. mystax from a natural population does not seem to impair its recuperative powers. It may take longer than four years for a population exhibiting high density, such as that at the Yarapa site, to recover completely.

The impact of cropping on wild populations of Saguinus mystax and Saguinus fuscicollis in Peru.

A transect census technique was used to estimate the population densities of Saguinus mystax and Saguinus fuscicollis at two sites in Peru. Cropping of these two species had occurred five years before the census at one site and two years before at the other. The populations of S. mystax at both sites had recovered completely from cropping, and the relationship between S. mystax and S. fuscicollis had not been altered at one site and had been reversed in favor of S. mystax at the other.

Growth and development in the saddle-back tamarin: The sequence and timing of dental eruption and epiphyseal union.

A cross-sectional sample of 121 colony-born saddle-back tamarins, Saguinus fuscicollis, was examined to identify the sequence and timing of dental eruption and epiphyseal union. The state of dental development of the deciduous and permanent dentitions was recorded as erupted or non-erupted on the basis of gingival penetration. Eighteen areas of union of long bone epiphyseal and other secondary centers, the union of the primary elements of the innominate, and the spheno-occipital synchondrosis were examined. The state of union at the areas was recorded on a three-point scale of not united, uniting, and united. The data indicated that deciduous incisors and canines were present at birth and that all deciduous teeth were erupted by 12 weeks. The first permanent tooth, M(1), erupted between weeks 16 and 23; the permanent dentition was fully erupted by 45 weeks. Union of the long bone epiphyses began in the third month at the distal humerus and continued until the first quarter of the second year. The secondary centers at the ischial tuberosity and iliac crest were united slightly later than four and six years of age, respectively. Regression analysis of the data indicate their potential use as parameters for predicting age in feral specimens.