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Cranial and Appendicular Skeletal Elements Show Correlated Responses to Selection among Large‐Bodied and Small‐Bodied Tamarins
Author(s) -
Agosto Elizabeth R,
Auerbach Benjamin M
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.578.16
Subject(s) - appendicular skeleton , skull , biology , anatomy , skeleton (computer programming) , humerus , postcrania , clavicle , condyle , scapula , selection (genetic algorithm) , artificial intelligence , computer science , botany , taxon
Correlated evolution among the appendicular skeleton and cranium is largely unexamined. The skeletal elements of the skull, neck, and upper thorax share soft tissue and developmental pathways, and so we hypothesize that these elements exhibit share responses to evolution. If such a relationship exists, we anticipate that correlated responses to evolutionary forces may be related to changes in body size over time. This study assesses the response to selection among four basicranial, five shoulder girdle, and three appendicular dimensions using retrospectively estimates selection gradients among two species of tamarins, large‐bodied Saguinus oedipus and the small‐bodied Saguinus fuscicollis illigeri , and an estimated mid‐species condition. The sample for this study consists of 50 individuals of each species; these data were used both in the primary analysis and to estimate a sample of individuals of intermediate body size. Vectors of estimated selection gradients necessary to evolve one tamarin species into another and from an intermediate state to large and small body sizes were analyzed using the following measurements: foramen magnum length and width, condylar length, size of the nuchal region, the length and width of the glenoid fossa and humeral head, and the lengths of the scapula, scapular spine, humerus, and clavicle. A 95% confidence interval was estimated for each selection gradient using a non‐parametric bootstrap. Results show correlated responses to selection among cranial and post‐cranial elements. These analyses demonstrate that most traits evolved by correlated responses to selection on other traits, and most significantly between cranial and post‐cranial traits. We show that the basicranium, scapula, and humerus are not evolving independently. While most of the observed responses to selection appear to follow expected changes in body size, the width and length of the foramen magnum, and the length of the scapula and humeral head do not, and may be reflecting underlying genetic covariances affecting these traits. This study demonstrates that the scapula and the head have mutual constraint, and that treating functional trait complexes as evolutionary isolated groups of traits may be overlooking important trait interactions. We cannot argue any longer that shoulder morphology reflects selection on the shoulder alone.