Isotope sclerochronology of Mercenaria mercenaria, M. Campechiensis, And their natural hybrid form: Does genotype matter?
Isotope sclerochronology of Mercenaria mercenaria, M. Campechiensis, And their natural hybrid form: Does genotype matter?
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Mercenaria Mercenaria、M. Campechiensis 及其自然杂交形式的同位素硬化年代学：基因型重要吗？
DOI：
10.2110/palo.2007.p07-056r
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发表时间：
2008
期刊：
影响因子：
3.5
通讯作者：
K. Walker
中科院分区：
文献类型：
--
作者：
D. Surge;G. M. Kelly;W. S. Arnold;Stephen P. Geiger;A. E. Goewert;K. Walker
摘要北方和南方硬壳层的同位素变化被用于古生态学、古气候学和考古学的研究。然而，目前还不清楚是否存在物种特有的同位素差异。在佛罗里达沿海水域发现了三种基因类型--南美耳藻、野油菜及其自然杂交型，从形态上很难确定基因类型的差异。当使用考古贝壳作为古气候档案时，这个问题可能会有问题，因为无法对这种标本进行遗传分析。它们在佛罗里达沿海水域的共同出现提供了一个独特的机会，可以研究现代个体的所有三种基因类型是否记录了作为氧和稳定碳同位素比率变化而保存的相同环境信息。用等位酶电泳法对从松岛海峡同一地点同时采集的49只活体进行了基因分型。为了控制个体发育效应，从每种基因型中选择3只幼虫进行同位素分析。从氧同位素比值推断的生长增量形成的时间显示出类似的总体模式，其中暗(缓慢生长)增量形成于中晚春，而光(快速生长)增量形成于晚秋。混合模型方差分析的结果表明，虽然Kolmogorov-Smirnov拟合度检验检测到南方红豆杉与南方红豆杉、南方红豆杉与杂交贝的δ~(13)C值之间存在系统差异，但氧和碳同位素比值的物种相关差异不显著。因此，任何基因型或其组合都适合于使用氧同位素比率重建环境和气候。然而，碳同位素比率作为环境指标的效用仍然值得怀疑。
Abstract Isotopic variation in northern and southern hard clam (quahog) shells is used in studies including paleoecology, paleoclimatology, and archaeology. It is unknown, however, whether species-specific isotopic differences exist. Three genotypes—Mercenaria mercenaria, M. campechiensis, and their natural hybrid form—are found in coastal Florida waters and differentiation of genotypes can be difficult to determine morphologically. This issue may be problematic when using archaeological shells as paleoclimate archives, because genetic analysis cannot be done on such specimens. Their co-occurrence in coastal Florida waters provides a unique opportunity to study whether all three genotypes of modern individuals record the same environmental information preserved as variation in oxygen and stable carbon isotope ratios. A random sample of 49 individuals collected alive at the same time and from the same locality in Pine Island Sound were classified to genotype using allozyme electrophoresis. Three juveniles from each genotype were selected for isotopic analysis to control for ontogenetic effects. Timing of growth increment formation inferred from oxygen isotope ratios reveals similar overall patterns wherein dark (slow growth) increments formed in mid- to late spring and light (fast growth) increments formed in late fall. Results of the mixed model ANOVA (analysis of variance) indicate that no significant species-related differences exist in the variation of oxygen and carbon isotope ratios, although the Kolmogorov-Smirnov goodness-of-fit test detected a systematic difference among δ13C values of M. mercenaria and M. campechiensis comparison and M. mercenaria and the hybrid shell comparison. Any genotype or combination thereof is, thus, suitable for environmental and climate reconstruction using oxygen isotope ratios. The utility of carbon isotope ratios as an environmental proxy, however, remains questionable.