Reproductive isolation and morphological divergence between cryptic lineages of the copepod Acartia tonsa in Chesapeake Bay
Reproductive isolation and morphological divergence between cryptic lineages of the copepod Acartia tonsa in Chesapeake Bay
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DOI：
10.3354/meps12569
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发表时间：
2018-06
影响因子：
2.5
通讯作者：
L. Plough;C. Fitzgerald;A. Plummer;J. Pierson
中科院分区：
文献类型：
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作者：
L. Plough;C. Fitzgerald;A. Plummer;J. Pierson
分子生物学技术的最新进展揭示了许多海洋浮游动物类群中的神秘物种。然而，隐性分化的模式和驱动因素是复杂的，很少有研究通过杂交来检查谱系之间的生殖状态。在这项研究中，我们进行了对内和之间的两个深刻分歧（隐性）谱系（命名为'新鲜' [F]和'盐' [S]）的河口桡足类Acartia tonsa从上切萨皮克湾，美国，检查产卵和孵化率。我们还研究了形态学（前体长度）和化学组成的2个谱系的差异。杂交试验表明，不同杂交类型的卵产量没有差异，但系间杂交的孵化率显著较低（F×S的平均孵化率为0.02，F×F和S×S的平均孵化率分别为0.46和0.52）。谱系间杂交几乎完全缺乏无节幼体生产，这表明生殖隔离很强，这支持了以前的分子数据。谱系之间在大小（F谱系短13 - 14%）和化学组成（F谱系每个桡足类的碳含量少70%）上的显著差异可能表明生殖的前合子障碍（例如形态或配子不相容）。总体而言，基于交叉，莫尔学和化学数据报告，并综合以前的生物学数据的F和S谱系，我们认为，这些神秘的谱系很可能是单独的，生殖隔离的物种。进一步研究了A.对环境变化的响应以及它们作为猎物的质量差异对于理解切萨皮克湾等河口环境中的营养动态具有重要意义。
Recent advances in molecular technologies have revealed cryptic species across many marine zooplankton taxa. However, the patterns and drivers of cryptic divergence are complex, and few studies have examined reproductive status among lineages through crosses. In this study, we performed pair crosses within and between 2 deeply divergent (cryptic) lineages (named ‘fresh’ [F] and ‘salt’ [S]) of the estuarine copepod Acartia tonsa from upper Chesapeake Bay, USA, to examine egg production and hatching rate. We also examined differences in morphology (prosome length) and chemical composition of the 2 lineages. Crossing experiments revealed that egg production did not differ among cross types but hatching rate was significantly lower for the between-lineage crosses (mean hatching rate of 0.02 for F×S vs. 0.46 and 0.52 for F×F and S×S, respectively). The nearly complete lack of nauplii production for between-lineage crosses suggests strong reproductive isolation, which supports previous molecular data. Significant differences between the lineages in size (F lineage is 13−14% shorter) and chemical com position (F lineages have 70% less carbon per copepod) may indicate pre-zygotic barriers to reproduction (e.g. morphological or gametic incompatibility). Overall, based on the crossing, mor phological, and chemical data reported here, and synthesizing previous biological data on the F and S lineages, we suggest that these cryptic lineages are likely to be separate, reproductively isolated species. Further work examining how divergent lineages of A. tonsa respond to environmental change and how they differ in their quality as prey items will be important for understanding trophic dynamics in estuarine environments like Chesapeake Bay.