Wild mixed groups of howler species (Alouatta caraya and Alouatta clamitans) and new evidence for their hybridization

• Published in: Primates 2008-04, Vol.49 (2), p.149-152
• Main Authors: Aguiar, Lucas M., Pie, Marcio R., Passos, Fernando C.
• Format: Article
• Language: English
• Subjects: Age Factors; Alouatta; Alouatta - physiology; Alouatta caraya; Animal behavior; Animal Ecology; Animal populations; Animal reproduction; Animals; Animals, Wild; Behavioral Sciences; Biodiversity; Biomedical and Life Sciences; Evolutionary Biology; Female; Hair Color; Hybridization; Hybridization, Genetic - physiology; Hybrids; Life Sciences; Male; Monkeys & apes; Phenotype; Population Density; Primates; Sex Ratio; Short Communication; Species Specificity; Zoology
• ISSN: 0032-8332; 1610-7365
• DOI: 10.1007/s10329-007-0065-y

Mixed species groups and hybridization are common among primates, yet these phenomena are rare and poorly understood for the genus Alouatta . In this study, we describe the composition of howler groups in a sympatric area of Alouatta caraya and Alouatta clamitans and provide new evidence for the occurrence of interspecific hybridization. Between October 2006 and April 2007, 11 howler groups were located in a 150-ha forest fragment: two monospecific groups of A. caraya , two monospecific groups of A. clamitans , two groups composed of A. clamitans and hybrid morphotypes ( A. caraya  ×  A. clamitans ), and five groups composed of both species together with hybrid morphotypes (mixed species groups). The average size of the studied groups was 5.2 ± 1.2 individuals. Monospecific and mixed groups (mixed species groups + groups with hybrids) did not differ significantly in their sizes. In total, the sex/age ratios were 1 AM:1.5 AF:0.2 SAM:0.5 JUV:0.2 INF and the species ratios were 1 A. caraya :1.6 A. clamitans :0.4 A. caraya  ×  A. clamitans . The ratio of immatures to 1AF was larger in the monospecific groups (0.75 immatures:1AF) than in mixed groups (0.29 immatures:1AF), possibly reflecting a lower viability in the latter. Two features of the hybrid morphotypes of the upper Paraná River support their status as true hybrids: the polymorphism of their coloration patterns and the extremely female-biased sex ratio. The effects of Haldane’s rule and population fragmentation on the interactions between both species are discussed.