Patterns of musculoskeletal growth and dimensional changes associated with selection and developmental plasticity in domestic and wild strain turkeys.

Kristin K Stover,Daniel M Weinreich,Elizabeth L Brainerd,Thomas J Roberts

doi:10.1002/ece3.3881

Abstract

Domestication is a type of experimental evolution in which humans have artificially selected for specific desired traits. Selected strain animals can be utilized to identify correlated responses by comparing them to the wild strain. In particular, domestic turkeys have been selected for increased body mass and high‐growth rate, most significantly over the past 60 years. Yet it remains unclear how artificial selection has affected the morphology and evolution of the musculoskeletal system as a whole. Here, we compare growth rate over 21 weeks, hind limb bone scaling across ontogeny via in vivo CT scanning, and muscle proportions in wild and domestic turkeys to identify differences in structural scaling and the potential contributions of selection and developmental plasticity to whole‐organism morphology. The domestic turkeys grew at a higher rate (0.14 kg/day vs. 0.05 kg/day) and reached over 3 times the body mass of wild birds. Comparing the proportional muscle masses in adult turkeys, only the trunk had a greater mass ratio in the domestic turkey, driven solely by M. pectoralis (2.8 times larger). The proportional increase in only breast meat and no other muscles highlights the surgical precision attainable with artificial selection. The domestic turkey femur and tibiotarsus displayed increases in polar moment of area, apparently maintaining torsional strength as body mass increased. The lack of dimensional change in the more vertically held tarsometatarsus is consistent with the pattern expected due to developmental plasticity. These results from the domestic turkey emphasize that there are morphological limits to preserving the balance between growth and function, and varying rates of trait evolution can further complicate this equilibrium.

Highlights

Artificial selection on domestic species can be very strong, resulting in animals that are quite distinct from their wild ancestors (Larson & Fuller, 2014; Lega, Raia, Rook, & Fulgione, 2015; Trut, Oskina, &Kharlamova, 2009)
Body mass is known to be more heritable than leg health parameters in turkeys (Kapell et al, 2017; Swalander, Burnside, & Glover, 2012), so we find it somewhat surprising that the domestic turkey’s bone strength, as indicated by polar moment of area (PMA), keeps pace with the wild turkey and predictions from isometry
A combination of bone remodeling due to supporting the domestic turkeys’ increasing body mass during growth and selection for walking ability has probably lead to the conserved PMA dimensions we found in these birds

Summary

| INTRODUCTION

Artificial selection on domestic species can be very strong, resulting in animals that are quite distinct from their wild ancestors While artificial selection has increased overall body mass in domestic turkeys, individual muscle proportions may be different from those of wild turkeys. We seek to understand how the morphology of muscles and bones has changed in the domestic turkey with increased body mass. This study can give us insight into musculoskeletal changes associated with increased body mass in other organisms, such as how the human body responds to obesity We can utilize these rapidly evolved turkeys to appreciate larger trends in the evolution of the musculoskeletal system, by describing how labile the system can be under known selective regimes of the commercial poultry industry (Neeteson et al, 2016)

| METHODS

| DISCUSSION

| CONCLUDING REMARKS

CONFLICT OF INTEREST