Influences of Domestication and Island Evolution on Dental Growth in Sheep

Madeleine Geiger,Abagael R West,Sinead Marron,Robert J Asher

doi:10.1007/s10914-018-9452-y

Madeleine Geiger, Abagael R West + Show 2 more

Open Access

https://doi.org/10.1007/s10914-018-9452-y

Copy DOI

Abstract

Domestication and island evolution can lead to changes of life history along the slow-fast gradient. Shifts of life history patterns, in turn, are potentially related to alterations of patterns and timing of tooth eruption. Schultz’s rule predicts an earlier eruption of molars relative to premolars as fecundity increases during the domestication process. On the other hand, evolution on a predator-free, resource limited island might lead to a generally slow life history and delayed tooth eruption, as in the Plio-Pleistocene Balearic caprine Myotragus. In this study, we investigate tooth eruption and its relation to life history in a unique sheep population that is an example of both domestication and island evolution: the ancient and feral Soay sheep (Ovis aries) of the St. Kilda archipelago, Scotland. Tooth eruption timing and sequence is investigated in a comparative framework featuring new data on other domestic sheep (O. aries), including European mouflon (O. a. musimon), as well as wild sheep (O. vignei, O. cycloceros, O. arkal, O. orientalis, O. ammon). These data indicate that the order of eruption is similar in wild and domestic sheep, despite the fundamental life history changes that came about with domestication. However, in contrast to other domestic sheep breeds, Soay sheep erupt their teeth at an absolute older age and also tend to grow more slowly, which resembles the evolutionary trend in island-adapted Myotragus. Despite these similarities, Soay sheep do not share the slow life history pattern inferred for Myotragus, highlighting the distinctive nature of tooth eruption in Soay sheep.

Highlights

Populations evolving on islands experience special environmental conditions and selection pressures not usually present on the mainland
There is some variation in tooth eruption as it relates to the absolute age among individuals, cheek teeth eruption sequences are similar in the wild and domestic sheep (Fig. 1, Table 4, Online Resource 2)
Domestication and its fundamental influence on the biology of sheep, notably life history, do not change the sequence of dental eruption in domestic sheep compared to their wild relatives

Summary

Introduction

Populations evolving on islands experience special environmental conditions and selection pressures not usually present on the mainland. These include a founder effect, a lack of predator pressure, low interspecific competition, and high intraspecific competition (see e.g., Sondaar 1977 and van der Geer et al 2010 for detailed reviews). Some of the phenotypic alterations that result from such selection pressures are similar in island and domestic mammals, e.g., increased size variation and shortening of limbs (Sánchez-Villagra et al 2016). The absence of predators and competitors from an island may lead to selection for faster growth and life history, e.g., earlier sexual maturity (e.g., Raia et al 2003)

Methods

Results

Discussion

Conclusion