Evolution of Mammal Tooth Patterns: New Insights From a Developmental Prediction Model

Abstract

The study of mammalian evolution is often based on insights into the evolution of teeth. Developmental studies may attempt to address the mechanisms that guide evolutionary changes. One example is the new developmental model proposed by Kavanagh et al. (2007), which provides a high-level testable model to predict mammalian tooth evolution. It is constructed on an inhibitory cascade model based on a dynamic balance of activators and inhibitors, regulating differences in molar size along the lower dental row. Nevertheless, molar sizes in some mammals differ from this inhibitory cascade model, in particular in voles. The aim of this study is to point out arvicoline and murine differences within this model and to suggest an alternative model. Here we demonstrate that the inhibitory cascade is not followed, due to the arvicoline's greatly elongated first lower molar. We broaden the scope of the macroevolutionary model by projecting a time scale onto the developmental model. We demonstrate that arvicoline evolution is rather characterized by a large gap from the oldest vole to more recent genera, with the rapid acquisition of a large first lower molar contemporaneous to their radiation. Our study provides alternative evolutionary hypotheses for mammals with different trajectories of development.K E Y W O R D S : Arvicolinae, evo-devo, evolution, inhibitory cascade, rodents.

Patterning by heritage in mouse molar row development

“…Second, the sequential development of the cheek tooth row is likely to be an integrated system, in which the development of molars and rudimentary buds is not independent. Recent articles have shown that during the first, second, and third molar sequential development, each developing molar exerts an inhibitory influence on the next developing molar (36,37). The present study suggests that this model should be extended to include the rudimentary buds that presumably represent premolars, meaning that the premolar rudiments would have an influence on patterning of molars (Fig.…”

“…Therefore, earlier events (ED 10.5-12.0) should be responsible for the positioning of the MS, which might be the first of a cascade that patterns the whole tooth row. Such a cascade has already been suggested for the patterning of M1, M2, and M3 (10,36,37), and rudimentary buds could act in it, independently of their later fate. This result would be reminiscent of the situation known in fish, in which a pioneer tooth often sets the stage for the development of an entire row (38).…”

Testing a developmental model in the fossil record: molar proportions in South American ungulates

“…In accordance with the IC model, it should be possible to determine m3 size (5 product of mesiodistal and buccolingual measurements) by using m1 size, following the relationship m3 5 0.655m1 (Renvoisé et al 2009). Among the groups examined herein, for the multiple regressions (Table 2, parts A) a significant relationship between m3 and m1 size was found for ''Meridiungulata'' and Astrapotheria.…”

Quantitative genetics provides predictive power for paleontological studies of morphological evolution

“…Hlusko et al (1) offer the example of the complex relationship between teeth and body size. Sexual dimorphism in size, including the dentition, is common in primates (18,19), but proportional tooth size is also linked to molecular genetic cascades of activators and inhibitors that produce sequences of molar teeth, and those proportions are linked to dietary function across a wide range of mammals, including primates (20)(21)(22)(23)(24). Selection for body size, sexual dimorphism, and dietary A B specialization can thus all have competing effects on primate dental traits (Fig.…”