Strontium Isotopes Support Small Home Ranges for Extinct Lemurs
Strontium Isotopes Support Small Home Ranges for Extinct Lemurs
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DOI：
10.3389/fevo.2019.00490
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发表时间：
2019-12-20
影响因子：
3
通讯作者：
Godfrey, Laurie Rohde
中科院分区：
文献类型：
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作者：
Crowley, Brooke Erin;Godfrey, Laurie Rohde
在哺乳动物中，包括类人灵长类动物，影响活动性的主要因素是体型（体型较大的物种比体型较小的物种活动性更强）、饮食（食果动物和营养性杂食动物比食叶动物活动性更大）和习性（陆地类群比树栖类群有更大的活动范围）。如果狐猴形目也存在类似的因素，我们预计体型较大（特别是食果）的已灭绝狐猴比体型较小（特别是食叶）的现存物种更具活动性。然而，多种证据（例如雷齐乌斯周期低、半规管尺寸小、相对大脑尺寸小）表明已灭绝的狐猴相对不活跃。如果是这样，它们的活动范围可能相对较小，也许与现存体型较小的狐猴相当。我们使用锶同位素 (Sr-87/Sr-86)（其空间变化主要随地质变化而变化）来比较八个狐猴属的活动性：Eulemur、狐猴、Lepilemur 和 Propithecus（现存），以及 Archaeolemur、Megaladapis、Pachylemur 和 Palaeopropithecus（已灭绝）。亚化石来自两个地点：Ankilitelo/Mikoboka（石灰岩高原上的一系列污水坑）和 Ampasambazimba（下面是各种火成岩和变质岩的湿地）。在这两个地点中，我们预计更多的移动类群会表现出更多变化的 Sr-87/Sr-86，反映了跨地质多样性的更大运动。我们发现这两个地点的 Sr-87/Sr-86 中位数或灭绝狐猴与现存狐猴之间的方差没有差异（所有比较中，Wilcoxon 和 Bartlett p > 0.05）。属之间存在明显但不显着的差异（Kruskal-Wallis 和 Bartlett p > 0.05）。 Ampasambazimba 的同位素变异性大于 Ankilitelo/Mikoboka 的同位素变异性，反映了底层地质的差异。一只来自 Ankilitelo/Mikoboka 的古猿和一只来自 Ampasambazimba 的 Eulemur 的 Sr-87/Sr-86 含量异常升高。这两个个体都可能被掠食性鸟类放置在各自的地点。这些结果证明了 Sr-87/Sr-86 对于测试与现已灭绝物种行为相关的假设的价值。锶同位素支持已灭绝狐猴的低流动性，并表明狐猴作为一个整体与类人猿不同，其基础代谢率相对较低，活动水平较低。这些特征减少了能量消耗，可能是为了应对马达加斯加的恶劣环境而开发的。然而，较小的活动范围也使狐猴更容易灭绝。
Among mammals, including anthropoid primates, the primary factors that affect mobility are body size (larger-bodied species move more than smaller ones), diet (frugivores and trophic omnivores are more mobile than folivores), and habit (terrestrial taxa have larger home ranges than arboreal ones). If similar factors hold for Lemuriformes, we would expect large-bodied (particularly frugivorous) extinct lemurs to have been more mobile than smaller-bodied (particularly folivorous) extant species. Yet multiple lines of evidence (e.g., low Retzius Periodicities, small semicircular canal size, small relative brain size) suggest that extinct lemurs were relatively inactive. If so, they may have had relatively small home ranges, perhaps on par with smaller-bodied extant lemurs. We used strontium isotopes (Sr-87/Sr-86), which vary spatially primarily as a function of geology, to compare mobility for eight lemur genera: Eulemur, Lemur, Lepilemur, and Propithecus (extant), and Archaeolemur, Megaladapis, Pachylemur, and Palaeopropithecus (extinct). Subfossils came from two sites: Ankilitelo/Mikoboka, a series of sinkholes in a limestone plateau, and Ampasambazimba, a wetland underlain by a variety of igneous and metamorphic rocks. Within either site, we expected more mobile taxa to exhibit more variable Sr-87/Sr-86, reflecting larger movement across a diversity of geologies. We found no differences in median Sr-87/Sr-86 or variance between extinct and extant lemurs at either site (Wilcoxon and Bartlett p > 0.05 for all comparisons). There were apparent but insignificant differences among genera (Kruskal-Wallis and Bartlett p > 0.05). Isotopic variability was greater at Ampasambazimba than at Ankilitelo/Mikoboka, reflecting differences in the underlying geology. One Palaeopropithecus from Ankilitelo/Mikoboka and one Eulemur from Ampasambazimba had unusually elevated Sr-87/Sr-86. Both of these individuals could have been deposited at their respective sites by a predatory bird. These results demonstrate the value of Sr-87/Sr-86 for testing hypotheses related to the behavior of now-extinct species. Strontium isotopes support low mobility for extinct lemurs, and suggest that Lemuriformes as a whole differ from anthropoids in having relatively depressed basal metabolic rates and reduced activity levels. These traits reduce energetic expenditure, and likely developed in response to Madagascar's harsh environments. However, small home ranges also make lemurs more vulnerable to extinction.