Brown Christopher A
Department of Biology, Box 5063, Tennessee Technological University, Cookeville, Tennessee 38505, USA.
Evolution. 2003 Sep;57(9):2184-90. doi: 10.1111/j.0014-3820.2003.tb00397.x.
Life-history traits are expected to exhibit negative phenotypic trade-offs, but often do not. In a seminal paper, van Noordwijk and de Jong (1986) provided an answer to this seeming paradox. According to their model, trade-offs will be more difficult to detect if variation in resource acquisition (or investment) is high relative to variation in resource allocation to the traits under consideration. Despite its influence on subsequent life-history studies, this model has rarely been tested. I use data from 10 species of scorpion (a total of 30 datasets, including multiple populations or years for some species) to test the van Noordwijk-de Jong model as modified to examine the relationship between offspring size and number. For both the overall data and a subset, including only the species Centruroides vittatus, I found that the correlation between offspring size and number within a population was significantly negatively correlated with the ratio of allocation variance to investment variance. That is, strong trade-offs were found when the investment variance was low relative to the allocation variance. These results were robust to the particular measure of offspring size and to whether offspring data were adjusted for female size variation. My results therefore provide strong evidence in support of the van Noordwijk and de Jong model.
生活史特征预计会表现出负向表型权衡，但实际情况往往并非如此。在一篇具有开创性的论文中，范诺德维克和德容（1986年）对这一看似矛盾的现象给出了答案。根据他们的模型，如果资源获取（或投资）的变化相对于所考虑性状的资源分配变化较大，那么权衡就更难被检测到。尽管该模型对后续的生活史研究产生了影响，但很少有人对其进行检验。我使用了10种蝎子的数据（总共30个数据集，其中一些物种包括多个种群或多年的数据）来检验经过修改的范诺德维克 - 德容模型，以研究后代大小和数量之间的关系。对于总体数据和一个子集（仅包括条纹正钳蝎物种），我发现种群内后代大小和数量之间的相关性与分配方差与投资方差的比率显著负相关。也就是说，当投资方差相对于分配方差较低时，会发现强烈的权衡。这些结果对于后代大小的特定测量方法以及后代数据是否针对雌性大小变化进行调整都是稳健的。因此，我的结果为支持范诺德维克和德容模型提供了有力证据。
