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Integration between ecology and biogeography provides insights into how niche specialization affects the geographical distribution of species. Given that rivers are not effective barriers to dispersal in three parapatric species of squirrel monkeys (Saimiri vanzolinii, S. cassiquiarensis and S. macrodon) inhabiting floodplain forests of Central Amazonia, we tested whether forest structure and tree diversity may explain species differences in niche specialization and spatial segregation. We sampled 6617 trees of 326 species in three habitats (high várzea, low várzea and chavascal) used by three Saimiri species, and estimated tree species richness in each of them. For each tree, we measured variables known to influence habitat use in primates, such as crown area and presence of lianas, epiphytes and hemi-epiphytes. We used ANOVA to compare these variables and performed multivariate analyses (NMDS, ANOSIM and SIMPER) to evaluate dissimilarities in forest structure among each habitat inhabited by the three Saimiri species. We identified differences in the tree species richness, crown area and presence of lianas, epiphytes and hemi-epiphytes between the three habitats for all Saimiri species. NMDS demonstrated that areas of high and low várzeas occupied by S. vanzolinii were clearly separated from the other species. We also found that different plant species contributed to dissimilarity among Saimiri ranges. Our findings support the hypothesis that tree community structure may promote niche specialization and spatial segregation among primates. We discuss how these patterns could have been favored by historical changes in forest flood patterns, the evolutionary history of Saimiri spp., and past competition.

Federal University of Par? - Campus Castanhal. Faculty of Veterinary Medicine. Laboratory of Wild Animal Biology and Medicine. Castanhal, PA, Par?, Brazil / Institute of Sustainable Development Mamirau?. Tef?, AM, Brazil. Federal University of Par? - Campus Castanhal. Faculty of Veterinary Medicine. Laboratory of Wild Animal Biology and Medicine. Castanhal, PA, Par?, Brazil / Minist?rio da Sa?de. Secretaria de Vigil?ncia em Sa?de. Instituto Evandro Chagas. Centro Nacional de Primatas. Ananindeua, PA, Brasil. Minist?rio da Sa?de. Secretaria de Vigil?ncia em Sa?de. Instituto Evandro Chagas. Centro Nacional de Primatas. Ananindeua, PA, Brasil. State University of Norte Fluminense Darcy Ribeiro. Laboratory of Animal Reproduction and Breeding. Campos dos Goytacazes, RJ, Brazil. Institute of Sustainable Development Mamirau?. Tef?, AM, Brazil. Institute of Sustainable Development Mamirau?. Tef?, AM, Brazil. Federal University of Par? - Campus Castanhal. Faculty of Veterinary Medicine. Laboratory of Wild Animal Biology and Medicine. Castanhal, PA, Par?, Brazil. Federal University of Par? - Campus Castanhal. Faculty of Veterinary Medicine. Laboratory of Wild Animal Biology and Medicine. Castanhal, PA, Par?, Brazil. Sperm morphometry can be applied to identify different animal groups and species and to evaluate sperm quality. Furthermore, knowledge on species-specific differences will help to enhance biological information, as well as to develop efficient reproductive technologies. The aims in the present study were to describe sperm morphometry from the recently characterized species S. collinsi and S. vanzolinii, to verify if the morphometric sperm patterns are similar or different between both species, and to determine if the sperm morphometry is affected by the levels of sperm defects using the S. collinsi as a model. Semen was collected from S. collinsi (n = 10) and S. vanzolinii (n = 2) monkeys, and sperm was submitted to morphological analysis. From the 10 samples from S. collinsi, five presented sperm of poor quality and two subgroups were formed for this species, i.e. high and poor quality sperm. Data on sperm motility and vigour were analysed, as well morphometric parameters on sperm head and tail. It was observed the normal morphometry was correlated with high quality sperm. Poor quality sperm presented smaller and 7% more ellipticity in their head, when compared with high quality sperm. Sperm from S. vanzolinii presented larger head than those from S. collinsi, but tail lengths were similar. Sperm morphometry can be used as a complementary tool to predict sperm motility and vigour for the S. collinsi species, and S. collinsi appear as a suitable model for S. vanzolinii.

Population monitoring of endangered species is essential to the improvement of their management and conservation plans. The black-headed squirrel monkey (Saimiri vanzolinii) is a vulnerable species on the IUCN Red List and has extreme geographical endemism, exhibiting the smallest known distribution among Neotropical primates (ca. 870 km2 ), over 90% of which occurs in white-water flooded forests within the Mamiraua Sustainable Development Reserve (MSDR), Brazilian Amazonia. To assess the effectiveness of this protected area in conserving the species, we conducted population monitoring of black-headed squirrel monkeys across five consecutive years (2009-2013) on nine trails 2 km each. Each year samples included both low and high river water periods. We used the distance sampling method, recording the distance to each observed social group as well as counting component individuals. We also calculated annual encounter rates based on the number of individuals sighted every 10 km traveled. Densities ranged from 256 individuals/km2 (2011) to 453 individuals/km2 (2013), and no seasonal differences were detected. Population size was estimated to be 147,848 mature individuals. Encounter rates ranged from 100 individuals/10 km (2010) to 179 individuals/10 km (2013); no significant difference among years was found. We found that S. vanzolinii populations remained stable throughout the years, which indicates that the MSDR has been playing an essential role on protecting this species. Due to difficulties of fulfilling assumptions of the distance sampling method, we consider the encounter rate analysis to be more effective for monitoring this and other Saimiri species. Given the critical endemism and worrying conservation status of S. vanzolinii, we suggest that monitoring of the species population should be carried out regularly.

The squirrel monkey, Saimiri, is a pan-Amazonian Pleistocene radiation. We use statistical phylogeographic methods to create a mitochondrial DNA-based timetree for 118 squirrel monkey samples across 68 localities spanning all Amazonian centers of endemism, with the aim of better understanding (1) the effects of rivers as barriers to dispersal and distribution; (2) the area of origin for modern Saimiri; (3) whether ancestral Saimiri was a lowland lake-affiliated or an upland forest taxa; and (4) the effects of Pleistocene climate fluctuation on speciation. We also use our topology to help resolve current controversies in Saimiri taxonomy and species relationships. The RondÔnia and Inambari centers in the southern Amazon were recovered as the most likely areas of origin for Saimiri. The Amazon River proved a strong barrier to dispersal, and squirrel monkey expansion and diversification was rapid, with all speciation events estimated to occur between 1.4 and 0.6. Ma, predating the last three glacial maxima and eliminating climate extremes as the main driver of squirrel monkey speciation. Saimiri expansion was concentrated first in central and western Amazonia, which according to the "Young Amazon" hypothesis was just becoming available as floodplain habitat with the draining of the Amazon Lake. Squirrel monkeys also expanded and diversified east, both north and south of the Amazon, coincident with the formation of new rivers. This evolutionary history is most consistent with a Young Amazon Flooded Forest Taxa model, suggesting Saimiri has always maintained a lowland wetlands niche and was able to greatly expand its range with the transition from a lacustrine to a riverine system in Amazonia. Saimiri vanzolinii was recovered as the sister group to one clade of Saimiri ustus, discordant with the traditional Gothic vs. Roman morphological division of squirrel monkeys. We also found paraphyly within each of the currently recognized species: S. sciureus, S. ustus, and S. macrodon. We discuss evidence for taxonomic revision within the genus Saimiri, and the need for future work using nuclear markers. © 2014 Elsevier Inc.

Summary Morphological information on the reproductive system allows the understanding of ecological and behavioural aspects of different species as well as supports the development of conservational strategies. Unfortunately, for many species, not enough relevant and precise information is available. In the present study, we describe for the first time the macroscopic and histological aspects of female genital organs and external female genitalia of Saimiri macrodon, Saimiri cassiquiarensis and Saimiri vanzolinii. We perform a comparison between these three peripatric species and investigate the possibility of their reproductive morphology to act as a factor of reproductive isolation. We have found that these species share many similarities in most of the analysed organs. Although some important differences were identified that may play an important role in the evolution of the components of the reproductive system of these species, those differences are not enough to compose a mechanism of reproductive isolation for these three species of Saimiri. The results of this study may be used to support the development of biotechnological approaches of reproduction and strategies for conservation programmes and management of threatened species of this genus, particularly S. vanzolinii, considered to be a vulnerable species to extinction.

This study was supported by the Mamirau? Institute for Sustainable Development (IDSM) (EcoVert-1.3.2011) and National Primate Center (CENP) (project 01/2014), Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior, CAPES (Brazil) (fellowship), and Federal University of Par? (UFPA) (project no 482570/2010-5). Minist?rio da Sa?de. Secretaria de Vigil?ncia em Sa?de. Instituto Evandro Chagas. Centro Nacional de Primatas. Ananindeua, PA, Brasil / Federal University of Par?. Laboratory of Wild Animal Biology and Medicine. Castanhal, PA, Brazil. Federal University of Par?. Laboratory of Wild Animal Biology and Medicine. Castanhal, PA, Brazil / Utrecht University. Faculty of Veterinary Medicine. Utrecht, The Netherlands. Federal University of Par?. Laboratory of Wild Animal Biology and Medicine. Castanhal, PA, Brazil. Mamirau? Institute for Sustainable Development. Tef?, AM, Brazil. Minist?rio da Sa?de. Secretaria de Vigil?ncia em Sa?de. Instituto Evandro Chagas. Centro de Inova??es Tecn?logica. Ananindeua, PA, Brazil. Federal University of Par?. Laboratory of Wild Animal Biology and Medicine. Castanhal, PA, Brazil. Differential phenotypic characteristics for taxonomic diagnosis purposes are well determined in the genus Saimiri (squirrel monkey). However, data on its reproductive characteristics are lacking. Our aim was to determine testicular biometry and correlate with seminal analysis in captive (Saimiri collinsi) and free living (Saimiri vanzolinii, Saimiri cassiquiarensis, and Saimiri macrodon) squirrel monkeys. Testicular length, width, height, circumference, and volume were measured. Testicular biometry showed no differences between right and left testicles within the same species, as well as among species. Semen collected by electroejaculation was constituted of a liquid and coagulated fraction, or only one of them. No significant difference was observed between mean volumes of liquid (49.2?68.9 ?L: S. collinsi; 28.3?59.8 ?L: S. vanzolinii; 5?7.1 ?L: S. cassiquiarensis; and 0 ?L: S. macrodon) and coagulated (65.4?142.1 ?L: S. collinsi; 125.8?142.5 ?L: S. vanzolinii; 175?176.8 ?L: S. cassiquiarensis; and 500 ?L: S. macrodon) fractions within species or when each fraction was compared among the studied species. No correlation between testicular volume and seminal volume was observed when liquid (R = 0.31, S. collinsi; R = 0.69, S. vanzolinii) and coagulated (R = 0.32, S. collinsi; R = 0.37, S. vanzolinii) fractions were evaluated. No sufficient data were obtained for the other two species. Seminal quality was similar among species, and the most common defect was coiled tail. The method of electroejaculation yielded satisfactory results on these species, under field conditions.