Academic journal article Genetics

Hybridization in Large-Bodied New World Primates

Academic journal article Genetics

Hybridization in Large-Bodied New World Primates

Article excerpt

ABSTRACT

Well-documented cases of natural hybridization among primates are not common. In New World primates, natural hybridization has been reported only for small-bodied species, but no genotypic data have ever been gathered that confirm these reports. Here we present genetic evidence of hybridization of two large-bodied species of neotropical primates that diverged ~3 MYA. We used species-diagnostic mitochondrial and microsatellite loci and the Y chromosome Sry gene to determine the hybrid status of 36 individuals collected from an area of sympatry in Tabasco, Mexico. Thirteen individuals were hybrids. We show that hybridization and subsequent backcrosses are directionally biased and that the only likely cross between parental species produces fertile hybrid females, but fails to produce viable or fertile males. This system can be used as a model to study gene interchange between primate species that have not achieved complete reproductive isolation.

HYBRIDIZATION can be viewed as either a breakdown of species boundaries that could eventually result in the loss of pure parental species or a creative force that can lead to the formation of new recombinant lineages (ARNOLD 1997; DOWLING and SECOR 1997; BARTON 2001; MALLET 2005; ARNOLD and MEYER 2006). Regardless of which view is taken, studies of hybridization are crucial for understanding the basis of reproductive isolation and the origins of biodiversity (COYNE and ORR 2004). Hybridization among metazoans has traditionally been viewed as an unusual event, but a variety of genetic studies in the past few decades have shown that this phenomenon is rather common, especially between closely related taxa (MALLET 2005). Among primates, natural hybridization occurs in at least 26 of ~233 Old World species (e.g., baboons, guenons, macaques, lemurs) in which hybridization occurs at intraspecific (GROVES 1978; LERNOULD 1988), interspecific (PHILLIPSCONROY and JOLLY 1986; SAMUELS and ALTMANN 1986; STRUHSAKER et al. 1988;WATANABE and MATSUMURA 1991; BYNUM et al. 1997; EVANS et al. 2001; WYNER et al. 2002), and even intergeneric levels (DUNBAR and DUNBAR 1974; JOLLY et al. 1997). Among neotropical primates, only 8 of ~132 Newworld species have been suggested to form hybrids in the wild (COIMBRA-FILHO et al. 1993; PERES et al. 1996; MENDES 1997) and these include only small-bodied and very recently separated taxa. Furthermore, of the few reported cases of interspecific hybridization in the wild (SILVA et al. 1993; MENDES 1997), the taxonomic status of the species is questionable.

Here we present evidence of hybridization of two large-bodied neotropical primates, Alouatta palliata and A. pigra. These are morphologically (LAWRENCE 1933; SMITH 1970), socially (CROCKETT and EISENBERG 1987; TREVES 2001; VAN BELLE and ESTRADA 2006), behaviorally (CROCKETT and EISENBERG 1987; NEVILLE et al. 1988; WHITEHEAD 1995), and genetically (CORTÉS-ORTIZ et al. 2003) distinct howler monkey species that diverged ~3MYA(CORTÉs-ORTIZ et al. 2003). A. palliata is currently found from southern Veracruz in Mexico through the central part of Guatemala and the southern part of Belize, continuing to the south through Honduras, Nicaragua, Costa Rica, Panama, and the Pacific coast of Colombia and Ecuador. On the other hand, A. pigra is confined to the Yucatan peninsula in Mexico, Belize, and the central and eastern part of Guatemala (Figure 1). Although A. palliata and A. pigra are allopatric in most of their range, SMITH (1970) reported an area of sympatry in the state of Tabasco, Mexico. Currently this area is highly deforested and only small patches of vegetation with various degrees of disturbance can be found. During a series of expeditions, we surveyed the area where sympatry had been reported and found troops with individuals of both A. palliata and A. pigra (based initially on morphological characters), as well as individuals that possessed morphological features of both species. Using a multilocus approach, we present genetic data that show that these howler monkeys are hybridizing in Mexico. …

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