Toljagic Olja, Voje Kjetil L, Matschiner Michael, Liow Lee Hsiang, Hansen Thomas F
Department of Biosciences, Centre for Ecological and Evolutionary Synthesis, University of Oslo, Blindernveien 31, NO-0371 Oslo, Norway.
Zoological Institute, University of Basel, Vesalgasse 1, 4051 Basel, Switzerland.
Syst Biol. 2018 Jan 1;67(1):145-157. doi: 10.1093/sysbio/syx059.
The Late Cretaceous appearance of grasses, followed by the Cenozoic advancement of grasslands as dominant biomes, has contributed to the evolution of a range of specialized herbivores adapted to new diets, as well as to increasingly open and arid habitats. Many mammals including ruminants, the most diversified ungulate suborder, evolved high-crowned (hypsodont) teeth as an adaptation to tooth-wearing diets and habitats. The impact of different causes of tooth wear is still a matter of debate, and the temporal pattern of hypsodonty evolution in relation to the evolution of grasslands remains unclear. We present an improved time-calibrated molecular phylogeny of Cetartiodactyla, with phylogenetic reconstruction of ancestral ruminant diets and habitats, based on characteristics of extant taxa. Using this timeline, as well as the fossil record of grasslands, we conduct phylogenetic comparative analyses showing that hypsodonty in ruminants evolved as an adaptation to both diet and habitat. Our results demonstrate a slow, perhaps constrained, evolution of hypsodonty toward estimated optimal states, excluding the possibility of immediate adaptation. This augments recent findings that slow adaptation is not uncommon on million-year time scales.
晚白垩世草本植物的出现，随后是新生代草原作为主要生物群落的发展，这促进了一系列适应新食性以及日益开阔和干旱栖息地的特化食草动物的进化。许多哺乳动物，包括最具多样性的有蹄类亚目反刍动物，进化出高冠（高齿冠）牙齿，以适应磨损牙齿的食性和栖息地。不同牙齿磨损原因的影响仍存在争议，高齿冠进化相对于草原进化的时间模式仍不清楚。我们基于现存分类群的特征，提出了一种改进的鲸偶蹄目时间校准分子系统发育树，并对反刍动物祖先的食性和栖息地进行了系统发育重建。利用这个时间线以及草原的化石记录，我们进行了系统发育比较分析，结果表明反刍动物的高齿冠进化是对食性和栖息地的双重适应。我们的结果表明，高齿冠向估计的最佳状态的进化是缓慢的，可能受到限制，排除了立即适应的可能性。这进一步证明了近期的研究发现，即在百万年的时间尺度上，缓慢适应并不罕见。
