【摘要】 基于大量不同生长阶段的标本,本文绘制华南湘中蒋家桥剖面C1-0和佘田桥剖面S-Y-4两个样品共10种小型腕足动物的种群结构和生存曲线,结果显示,C1-0动物群内没有一种腕足类的大小-频率分布呈典型的正常钟型分布模式,仅Thomasaria?baii,Thomasaria?liangi,Xiangia liaoi,Cyrtinaella?houi及Gypidula xui的直方图有些类似钟型分布,而Qidongia tani,Athyris supervittata及Levipugnax?liui的直方图则呈明显的右斜型***分布。各种群生存曲线表现为不同程度的下凹型,这可能与它们生活在泥质软基底的环境有关。Thomasaria?baii为浅凹型,Levipugnax?liui,Xiangia liaoi,Gypidula xui,Qidongia tani及Cyrtinaella?houi为中凹型,Athyris supervittata及Thomasaria?liangi呈深凹型;依次反映的是更高的幼年期死亡率,之后死亡率持续降低的特点,而上述大小-频率分布和生存曲线型式的差异则可能反映了不同种类对环境条件适应程度的差异,例如不同的壳形可能导致的应对软基底及取食效率的区别。对蒋家桥剖面Iowatrypapseudobodini和佘田桥剖面Hunanotoechia tieni块体采样及手捡采样两种不同方法的结果对比表明,采样方法可以不同程度地影响腕足动物种群的大小-频率分布及生存曲线。为了获得最接近真实情况的生存曲线,工作中应尽量采用两种方法相结合。更多还原

【Abstract】 Survivorship curves and size-frequency distributions of 10 fossil species populations have been depicted based on abundant small-sized brachiopod specimens of various growth stages of two samples(C1-0 of Jiangjiaqiao and S-Y-4 of Shetianqiao sections)from Hunan Province of southern China.None of the size-frequency distributions of the C1-0fauna are of a normal bellshaped distribution pattern;only those of Thomasaria?baii,Thomasaria?liangi,Xiangia liaoi,Cyrtinaella?houi and Gypidula xui somewhat resemble a bell-shaped distribution,whereas Qidongia tani,Athyris supervittata and Levipugnax?liui display a distinct right-skewed pattern.The survivorship curves of various populations are of the concave type of various degrees,which was probably related with their living on the muddy substrate.Survivorship curve of Thomasaria?baii is slightly concave,whereas those of other species are of either moderately concave type,e.g.,Levipugnax?liui,Xiangia liaoi,Gypidula xui,Qidongia tani and Cyrtinaella?houi,or strongly concave type,e.g.,Athyris supervittata and Thomasaria?liangi,suggesting a high mortality rate during the juvenile stage and decreasing mortality rate towards the gerontic stage.The above differences in size-frequency distributions and survivorship curves of various species are probably a result of their adaptational differences to the muddy environments.For example,differences in shell shape might be related with their adaptational differences to both muddy substrate and feeding efficiency. Study of Iowatrypa pseudobodini and Hunanotoechia tieni shows that size-frequency distributions and survivorship curves of brachiopod populations can be affected by sampling methods to various degrees in case of fewer specimens by hand-picking.Bulk sampling is recommended for population analysis,in combination with hand-picking in some cases for more actual survivorship curves.更多还原