Size-frequency distributions along a latitudinal gradient in Middle Permian fusulinoideans.
Size-frequency distributions along a latitudinal gradient in Middle Permian fusulinoideans.
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中二叠世 Fusulinoideans 沿纬度梯度的尺寸频率分布
DOI：
10.1371/journal.pone.0038603
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发表时间：
2012
期刊：
影响因子：
3.7
通讯作者：
Payne JL
中科院分区：
文献类型：
--
作者：
Zhang Y;Payne JL
生物物种内部和物种之间体型的地理梯度通常被用来确定对生物体型长期进化的控制。然而，这些梯度在进化时间中的持久性仍然很大程度上是未知的，因为古代生物大小的生物地理变化记录很少。中二叠纪有孔虫是研究生物大小地理梯度的时间持久性的理想选择，因为在这一时期（约2.75 - 2.6亿年前），它们在广泛的古纬度范围内种类繁多，数量丰富。为了探讨有孔虫的大小与区域环境的关系，我们测定了三个不同古纬带的中二叠世毛虫纲化石的大小。我们恢复了以下结果：角质鞘镰刀菌比非角质鞘镰刀菌大得多；来自赤道带的Fusulinoideans通常比来自南北过渡带的Fusulinoideans大；赤道地区单一物种内的新石尾虫标本通常大于两个过渡带内的标本；在北过渡带，非核鞘的镰刀纲、Staffellidae和Schubertellidae的体型较小。与伯格曼的规则相反，毛丝虫纲有孔虫与大多数其他海洋分类的不同之处在于，它们在靠近赤道的地方表现出更大的体型。经向季节性、水温、养分有效性和碳酸盐饱和度的变化都可能有利于或使赤道地区的规模更大。大气氧浓度的时间变化已被证明可以解释石炭纪和二叠纪期间毛藻纲大小的时间变化，但氧气供应似乎不太可能解释毛藻纲大小的生物地理变化，因为海水中的溶解氧浓度通常会因海水温度下降而在远离赤道的地方增加。因此，我们的研究结果强调了这样一个事实，即生物大小的空间梯度并不总是由控制同一分支内时间趋势的相同因素控制。
Geographic gradients in body size within and among living species are commonly used to identify controls on the long-term evolution of organism size. However, the persistence of these gradients over evolutionary time remains largely unknown because ancient biogeographic variation in organism size is poorly documented. Middle Permian fusulinoidean foraminifera are ideal for investigating the temporal persistence of geographic gradients in organism size because they were diverse and abundant along a broad range of paleo-latitudes during this interval (∼275–260 million years ago). In this study, we determined the sizes of Middle Permian fusulinoidean fossils from three different paleo-latitudinal zones in order to examine the relationship between the size of foraminifers and regional environment. We recovered the following results: keriothecal fusulinoideans are substantially larger than nonkeriothecal fusulinoideans; fusulinoideans from the equatorial zone are typically larger than those from the north and south transitional zones; neoschwagerinid specimens within a single species are generally larger in the equatorial zone than those in both transitional zones; and the nonkeriothecal fusulinoideans Staffellidae and Schubertellidae have smaller size in the north transitional zone. Fusulinoidean foraminifers differ from most other marine taxa in exhibiting larger sizes closer to the equator, contrary to Bergmann's rule. Meridional variation in seasonality, water temperature, nutrient availability, and carbonate saturation level are all likely to have favored or enabled larger sizes in equatorial regions. Temporal variation in atmospheric oxygen concentrations have been shown to account for temporal variation in fusulinoidean size during Carboniferous and Permian time, but oxygen availability appears unlikely to explain biogeographic variation in fusulinoidean sizes, because dissolved oxygen concentrations in seawater typically increase away from the equator due to declining seawater temperatures. Consequently, our findings highlight the fact that spatial gradients in organism size are not always controlled by the same factors that govern temporal trends within the same clade.
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