Dental functional traits of mammals resolve productivity in terrestrial ecosystems past and present

Abstract

We have recently shown that rainfall, one of the main climatic determinants of terrestrial net primary productivity (NPP), can be robustly estimated from mean molar tooth crown height (hypsodonty) of mammalian herbivores. Here, we show that another functional trait of herbivore molar surfaces, longitudinal loph count, can be similarly used to extract reasonable estimates of rainfall but also of temperature, the other main climatic determinant of terrestrial NPP. Together, molar height and the number of longitudinal lophs explain 73 per cent of the global variation in terrestrial NPP today and resolve the main terrestrial biomes in bivariate space. We explain the functional interpretation of the relationships between dental function and climate variables in terms of long-and short-term demands. We also show how the spatially and temporally dense fossil record of terrestrial mammals can be used to investigate the relationship between biodiversity and productivity under changing climates in geological time. The placement of the fossil chronofaunas in biome space suggests that they most probably represent multiple palaeobiomes, at least some of which do not correspond directly to any biomes of today's world.

Computational biomes: The ecometrics of large mammal teeth

“…Another functional characteristic of the teeth of herbivorous mammals commonly used to estimate climatic conditions is the presence of lophs (Liu et al, 2012;Fortelius et al, 2016;. Globally, the higher the average loph count of the community, the lower the mean annual temperature is expected to be (Liu et al, 2012).…”

“…Globally, the higher the average loph count of the community, the lower the mean annual temperature is expected to be (Liu et al, 2012). High average loph counts denote the presence of topographically prominent longitudinal lophs, an uncommon feature among hippos, suids and among large shares of primates and elephants.…”

“…Ecometrics can be used for reconstructing past climate and environments (Eronen et al, 2010b;Meloro and Kovarovic, 2013;Saarinen, 2015;Sukselainen et al, 2015;Fortelius et al, 2016), understanding evolution of faunal communities (Eronen et al, 2009), analysing macroevolution patterns (Schnitzler et al, 2017) and understanding the functional relationships between organisms and their environments (Eronen et al, 2010a;Lawing et al, 2012;Liu et al, 2012;Polly and Head, 2015;Zliobaite et al, 2016;Barr, 2017). Different traits have been explored for ecometric analyses.…”

“…For plants, leaf shapes have been considered (Wolfe, 1995;Traiser et al, 2005). For animals, considered traits include teeth (Eronen et al, 2010a;Liu et al, 2012;Meloro and Kovarovic, 2013;Polly and Head, 2015;Fortelius et al, 2016;Zliobaite et al, 2016), limbs and locomotion (Polly and Head, 2015;Barr, 2017;Levering et al, 2017), skeletal traits (Lawing et al, 2012), as well as body mass (Meloro and Kovarovic, 2013). Traditionally, the term ecometrics refers to the analysis of animal traits.…”

“…We then analyze those trends across climatic zones. This approach differs from common ecometric modeling, where global models are constructed with the aim of accurately predicting climate based on the traits of species communities (see e.g., Liu et al, 2012). Instead, redescription mining identifies associations between dental traits and climate which hold locally.…”