Masticatory Apparatus Performance and Functional Morphology in the Extremely Large Mice from Gough Island.
biomechanics; biting; gape; islands; mandible
Since their arrival approximately 200 years ago, the house mice (Mus musculus) on Gough Island (GI) rapidly increased in size to become the largest wild house mice on record. Along with this extreme increase in body size, GI mice adopted a predatory diet, consuming significant quantities of seabird chicks and eggs. We studied this natural experiment to determine how evolution of extreme size and a novel diet impacted masticatory apparatus performance and functional morphology in these mice. We measured maximum bite force and jaw opening (i.e., gape) along with several musculoskeletal dimensions functionally linked to these performance measurements to test the hypotheses that GI mice evolved larger bite forces and jaw gapes as part of their extreme increase in size and/or novel diet. GI mice can bite more forcefully and open their jaws wider than a representative mainland strain of house mice. Similarly, GI mice have musculoskeletal features of the masticatory apparatus that are absolutely larger than WSB mice. However, when considered relative to body size or jaw length, as a relevant mechanical standard, GI mice show reduced performance, suggesting a size-related decrease in these abilities. Correspondingly, most musculoskeletal features are not relatively larger in GI mice. Incisor biting leverage and condylar dimensions are exceptions, suggesting relative increases in biting efficiency and condylar rotation in GI mice. Based on these results, we hypothesize that evolutionary enhancements in masticatory performance are correlated with the extreme increase in body size and associated musculoskeletal phenotypes in Gough Island mice. Anat Rec, 2019. (c) 2018 Wiley Periodicals, Inc.
Parmenter Michelle D; Nelson Jacob P; Weigel Sara E; Gray Melissa M; Payseur Bret A; Vinyard Christopher J
Anatomical record (Hoboken, N.J. : 2007)
2018
2018-12
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1002/ar.24053" target="_blank" rel="noreferrer noopener">10.1002/ar.24053</a>
Genetics of Skeletal Evolution in Unusually Large Mice from Gough Island.
Female; Male; Animals; *body size; *complex trait; *island syndrome; *phenotypic extreme; *pleiotropy; *Quantitative Trait Loci; *skeletal evolution; Body Size/*genetics; Bone and Bones/*anatomy & histology; Genetic Pleiotropy; Islands; Mice/*genetics; Molecular; *Evolution
Organisms on islands often undergo rapid morphological evolution, providing a platform for understanding mechanisms of phenotypic change. Many examples of evolution on islands involve the vertebrate skeleton. Although the genetic basis of skeletal variation has been studied in laboratory strains, especially in the house mouse Mus musculus domesticus, the genetic determinants of skeletal evolution in natural populations remain poorly understood. We used house mice living on the remote Gough Island-the largest wild house mice on record-to understand the genetics of rapid skeletal evolution in nature. Compared to a mainland reference strain from the same subspecies (WSB/EiJ), the skeleton of Gough Island mice is considerably larger, with notable expansions of the pelvis and limbs. The Gough Island mouse skeleton also displays changes in shape, including elongations of the skull and the proximal vs. distal elements in the limbs. Quantitative trait locus (QTL) mapping in a large F2 intercross between Gough Island mice and WSB/EiJ reveals hundreds of QTL that control skeletal dimensions measured at 5, 10, and/or 16 weeks of age. QTL exhibit modest, mostly additive effects, and Gough Island alleles are associated with larger skeletal size at most QTL. The QTL with the largest effects are found on a few chromosomes and affect suites of skeletal traits. Many of these loci also colocalize with QTL for body weight. The high degree of QTL colocalization is consistent with an important contribution of pleiotropy to skeletal evolution. Our results provide a rare portrait of the genetic basis of skeletal evolution in an island population and position the Gough Island mouse as a model system for understanding mechanisms of rapid evolution in nature.
Parmenter Michelle D; Gray Melissa M; Hogan Caley A; Ford Irene N; Broman Karl W; Vinyard Christopher J; Payseur Bret A
Genetics
2016
2016-12
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1534/genetics.116.193805" target="_blank" rel="noreferrer noopener">10.1534/genetics.116.193805</a>