Institut Català de Paleontologia Miquel Crusafont, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Barcelona, Spain.
Proc Biol Sci. 2012 Aug 22;279(1741):3339-46. doi: 10.1098/rspb.2012.0689. Epub 2012 Apr 25.
Here, we test whether the increase in tooth height in insular endemics results from the expansion of the dietary niche under resource limitation, as widely considered, or whether it represents an investment in dental durability in response to the selection for extended longevity under low levels of extrinsic mortality. We tested these hypotheses in the extremely hypsodont fossil bovid Myotragus balearicus from the Balearic Islands, an ideal model to study the evolutionary trends on islands. Dental abrasion was significantly lower in the insular bovid than in highly hypsodont continental artiodactyls, suggesting that feeding habits are not the sole driving force behind increased crown height. However, the estimated longevity for M. balearicus based on dental durability was two times that predicted from body mass. Survivorship curves confirm that an extraordinarily large number of individuals approached the longevity of the species. Our results, hence, provide evidence that hypsodonty in insular endemics is the outcome of selection for increased durability of the permanent dentition in association with an extended lifespan. In the context of insularity, our results lend additional support to the disposable soma theory of ageing confirming the dependency of somatic maintenance and repair on lifespan, and its control by resource availability and extrinsic mortality.
在这里，我们测试了岛屿特有种中牙齿高度的增加是否是由于在资源限制下饮食生态位的扩大，就像人们普遍认为的那样，还是代表了对牙齿耐用性的投资，以应对在低水平的外在死亡率下选择延长寿命。我们在来自巴利阿里群岛的极其高冠齿的化石有蹄类动物 Myotragus balearicus 中检验了这些假设，这是研究岛屿上进化趋势的理想模型。与高度高冠的大陆有蹄类动物相比，岛屿上的有蹄类动物的牙齿磨损明显较低，这表明饮食习惯并不是导致冠高增加的唯一驱动力。然而，基于牙齿耐用性估计的 M. balearicus 的预期寿命是根据体重预测的两倍。生存曲线证实，大量个体接近了该物种的寿命。因此，我们的研究结果为岛屿特有种的高冠齿是为了增加永久性牙齿的耐用性而选择的结果提供了证据，这与延长寿命有关。在岛屿环境的背景下，我们的结果为衰老的可抛弃体理论提供了额外的支持，证实了身体维护和修复对寿命的依赖性，以及寿命由资源可用性和外在死亡率控制。
