Morphometric analyses of Ateles: systematic and biogeographic implications.

Area of Science:

• Primatology and Evolutionary Biology
• Neotropical Biodiversity and Biogeography
• Morphometrics and Phylogenetics

Background:

• Understanding neotropical biodiversity patterns requires evaluating models of vicariance and parapatry.
• Spider monkeys (Ateles) are a key genus for studying South American evolutionary history.
• Previous classifications may not fully reflect current morphometric data.

Purpose of the Study:

• To examine cranial and dental morphometric patterns in South American spider monkeys (Ateles).
• To test predictions of vicariance and parapatry models using multivariate analyses.
• To revise taxonomic relationships and understand biogeographic processes in the Neotropics.

Main Methods:

• Analysis of cranial and dental morphometric data from 284 spider monkey specimens.
• Standardization for sex differences and factor analysis to control for body size effects.
• Independent discriminant analyses, pooled data cluster analysis, and dendrogram construction.

Main Results:

• Morphometric data revealed three distinct taxa, differing from current classifications.
• A ring species-like cline of relationships was observed around Amazonia, with intergradation across major rivers.
• Evidence supports tierra firme and forest refugia models, but with nuances regarding Amazonian refugia and pelage patterns.

Conclusions:

• Current spider monkey classification is discordant with morphometric data, indicating at least three independent taxa.
• Major Amazonian rivers may not function as complete barriers to gene flow as previously thought.
• Parapatric differentiation, potentially driven by assortative mating, may explain incipient speciation in some populations.