Abstract The arrangement of scutes on the carapaces of extant chelonians is very similar among species, but intraspecific deviations from typical scute patterns are common. Because intraspecific variation may relate to inbreeding depression, unfavourable egg incubation conditions and the presence of environmental pollutants, investigations of carapacial scute patterns in natural populations can enhance insight into the ecologies and survival challenges of chelonians. A population of the tortoise Homopus signatus, inhabiting an arid range with substantial annual rainfall variation, was sampled to record carapacial scute patterns. The typical pattern of H. signatus consisted of five vertebral scutes, four pairs of costal scutes, a cervical and a supracaudal scute, and 12 pairs of marginal scutes. Although it was expected that size classes (i.e. representing tortoises born in different years) and sexes would have different percentages deviations from the typical scute pattern as a result of different egg incubation conditions, percentages were similar among size classes and sexes. A high percentage of 44% (25% if counts of the relatively variable marginal scutes were excluded) of all tortoises had deviant carapacial scute patterns. Since the study population was situated in a relatively pristine area and supernumerary carapacial scutes appear related to egg incubation conditions in other chelonians, the wide variation in carapacial scute patterns in wild H. signatus may be the result of frequently challenging incubation conditions in the species’ harsh environment.

中文翻译：

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斑点陆龟自然种群中甲壳盾图案的广泛变化，Homopus signatus

摘要 现存龟类甲壳上的盾甲排列在物种之间非常相似，但与典型盾甲图案的种内偏差很常见。由于种内变异可能与近亲繁殖抑制、不利的卵孵化条件和环境污染物的存在有关，因此对自然种群中的甲壳盾模式的调查可以增强对龟类生态和生存挑战的了解。对居住在年降雨量变化很大的干旱地区的陆龟 Homopus signatus 种群进行采样以记录甲壳盾模式。H. signatus 的典型形态包括 5 块椎板、4 对肋板、1 对颈盾和 1 对尾板，以及 12 对边缘板。尽管预计尺寸等级（即 代表不同年份出生的陆龟）和性别会由于不同的卵孵化条件而与典型的龟甲模式有不同的百分比偏差，大小等级和性别之间的百分比相似。所有陆龟中有 44% 的高比例（如果排除相对可变的边缘盾牌的数量，则为 25%）具有异常的甲壳盾模式。由于研究种群位于相对原始的区域，并且额外的甲壳盾似乎与其他龟类的卵孵化条件有关，野生海龟的甲壳盾模式的广泛变化可能是该物种经常具有挑战性的孵化条件的结果恶劣的环境。