The evolution of egg clustering in butterflies: A test of the egg desiccation hypothesis
The evolution of egg clustering in butterflies: A test of the egg desiccation hypothesis
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DOI：
10.1023/a:1006504725592
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发表时间：
1998-07-01
影响因子：
1.9
通讯作者：
Faeth, SH
中科院分区：
文献类型：
--
作者：
Clark, BR;Faeth, SH
许多昆虫的雌性将卵聚集在一起。鳞翅目物种的卵聚集通常会导致幼虫聚集，这些幼虫的颜色通常比单独物种的幼虫更明显，而且明显令人厌恶或难吃。虽然聚集在幼虫生存和生长方面的成本和效益已有充分记录，但卵聚集的进化生态学长期以来一直存在争议，且仍未得到解决。我们测试了由 Stamp (1980) 首先提出的鸡蛋干燥假说，据我们所知，该假说从未经过实验检验。卵干燥假说认为，卵聚集本身就是适应性的（即通过干燥降低卵死亡率）（即增加雌性的适应性）。我们用蛱蝶 Chlosyne lacinia 测试了这一假说，这是一种在其向日葵寄主植物 Helianthus annuus 上进行卵聚集的物种。我们首先记录了这只蝴蝶的批量大小的自然变化。然后，我们通过实验测试了在受控湿度水平下不同批量大小和产蛋安排的孵化成功率。孵化成功与相对湿度呈正相关。较大群体、较多层数的蛋比较小的单层蛋批次的孵化成功率更高，特别是在相对湿度较低的情况下。我们的结果表明，不仅鸡蛋的数量，而且排列（即分层和密度）都可以通过保护鸡蛋免于干燥来提高批次存活率。然而，尽管密集、多层簇的孵化成功率有所提高，但我们发现 C. lacinia 自然种群的分层和密度存在很大差异。这种差异可能是通过对卵子存活率的权衡来维持的，例如在密集的簇中，兄弟姐妹对卵子的同类相食行为增加。然而，防止卵干燥为鳞翅目昆虫和可能的其他昆虫中卵聚集的起源和维持提供了另一种解释。蛱蝶科的卵沉积模式支持了这一假设，因为大多数北美物种将卵紧密地聚集在一起，而热带地区的大多数物种则单独产卵或以松散的单层产卵。
Females of many insect species cluster their eggs. Egg clustering by lepidopteran species usually results in aggregation of larvae that are more often conspicuously coloured and apparently distasteful or unpalatable than larvae of solitary species. While the costs and benefits of aggregation in terms of larval survival and growth are well documented, the evolutionary ecology of egg clustering has been long debated and is still unresolved. We tested the egg desiccation hypothesis, first proposed by Stamp (1980), which to our knowledge has never been examined experimentally. The egg desiccation hypothesis proposes that egg clustering is adaptive per se (i.e. increases fitness of females) by reducing egg mortality via desiccation.We tested this hypothesis for the Nymphalid butterfly, Chlosyne lacinia, an egg-clustering species on its sunflower host plant, Helianthus annuus. We first documented natural Variation in batch size for this butterfly. We then tested experimentally hatch success of varying batch sizes and egg-layering arrangements under controlled humidity levels. Hatch success was positively related to relative humidity. Eggs in larger groups with greater number of layers had greater hatch success than smaller, monolayered egg batches, especially when relative humidity was low. Our results indicate that, not only number of eggs, but also the arrangement (i.e. layering and density), increase batch survival by protecting eggs from desiccation. However, despite increased hatch success in dense, multilayered clusters, we found wide variation in layering and density in natural populations of C. lacinia. This variation is probably maintained by trade-offs in egg survival, such as increased cannibalism of eggs by siblings, in dense clusters. Nevertheless, protection from egg desiccation provides an alternative explanation for the origin and maintenance of egg clustering in lepidopterans and possibly other insects. The pattern of egg deposition in the Nymphalidae supports this hypothesis, since most North American species cluster their eggs tightly,whereas most species in tropical regions lay eggs singly or in loose monolayers.