Toyama Ken S, Junes Karina, Ruiz Jorge, Mendoza Alejandro, Pérez Jose M
Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, M5S 3B2, Canada; Laboratorio de Estudios en Biodiversidad (LEB), Universidad Peruana Cayetano Heredia, Av. Honorio Delgado 430, Urb. Ingeniería, S.M.P., Lima, Peru.
Laboratorio de Estudios en Biodiversidad (LEB), Universidad Peruana Cayetano Heredia, Av. Honorio Delgado 430, Urb. Ingeniería, S.M.P., Lima, Peru.
Zoology (Jena). 2018 Aug;129:45-53. doi: 10.1016/j.zool.2018.06.004. Epub 2018 Jun 19.
Ontogenetic shifts from an insectivorous diet towards an herbivorous one are well known in lizards. Energetic, behavioral and morphological factors have been linked to this pattern, but the latter have received less attention, especially with respect to head morphology. It is known that robust heads are related to stronger bite forces, consequently facilitating the consumption of harder or tougher, more fibrous items such as plants. In this study the ontogeny of diet and head morphology of the omnivorous tropidurid lizard Microlophus thoracicus are described. We found a significant ontogenetic shift from a mainly insectivorous diet in juveniles to a mainly herbivorous one in adults. In parallel, we measured the length, height and width of the head of the studied individuals. We found that adult individuals showed proportionally taller and wider heads when compared to juveniles, and that these increases in proportional head dimensions were significantly correlated with the increase in plant material in the diet that we observed. Additionally, we compared the morphologies of adults and juveniles of M. thoracicus and two other Microlophus species known to be insectivorous. These comparisons showed that M. thoracicus adults have proportionally more robust heads when compared to their insectivorous congeners, which is in agreement with the hypothesized link between head morphology and diet characteristics. The results of this study suggest that the known relationship between herbivory and head morphology is maintained even in an ontogenetic context, but further study is needed to determine the effect of other selective pressures which influence these changes in morphology.
在蜥蜴中，从食虫性饮食向草食性饮食的个体发育转变是众所周知的。能量、行为和形态学因素都与这种模式有关，但后者受到的关注较少，尤其是在头部形态方面。众所周知，强壮的头部与更强的咬合力有关，因此有助于食用更硬、更坚韧、纤维更多的食物，如植物。在这项研究中，描述了杂食性热带蜥蜴米氏角蜥（Microlophus thoracicus）的饮食和头部形态的个体发育过程。我们发现，幼年个体的饮食主要为食虫性，而成年个体则主要为草食性，这一转变具有显著的个体发育特征。同时，我们测量了所研究个体头部的长度、高度和宽度。我们发现，与幼年个体相比，成年个体的头部相对更高更宽，而且这些头部尺寸比例的增加与我们观察到的饮食中植物性物质的增加显著相关。此外，我们比较了米氏角蜥成年个体和幼年个体以及另外两种已知为食虫性的角蜥属物种的形态。这些比较表明，与食虫性的同属物种相比，米氏角蜥成年个体的头部相对更粗壮，这与头部形态和饮食特征之间的假设联系相符。这项研究的结果表明，即使在个体发育的背景下，草食性与头部形态之间的已知关系依然存在，但还需要进一步研究来确定影响这些形态变化的其他选择压力的作用。
