PERIODICAL CICADA PROBLEM .2. EVOLUTION
PERIODICAL CICADA PROBLEM .2. EVOLUTION
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DOI：
10.1111/j.1558-5646.1966.tb03381.x
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发表时间：
1966-01-01
期刊：
影响因子：
3.3
通讯作者：
DYBAS, HS
中科院分区：
文献类型：
--
作者：
LLOYD, M;DYBAS, HS
任何一个科学家都知道，判断一个理论的标准不应该是它的合理性或缺乏合理性，而应该是它能在多大程度上预见新的发现。因此，我们总结的最重要的事情是寻找新的东西。我们需要更多地了解非周期性蝉的发育时期。从纯粹的人口统计学角度来看，生育前期过长应该是一个严重的不利因素;在其他条件相同的情况下，应该坚决反对生育前期过长。根据表2中的数据，我们必须假设蝉的长发育期特征具有一些相反的优势。作为一个假设，我们在表3中提出了一个反优势与响亮的歌曲，大尺寸，和强制性缓慢喂养。这个想法可以通过发现一种生命周期短的大型蝉来推翻，只要它的进食习惯是一般蝉的典型特征。安德森和肖里目前对芦笋根上的阿帕奇二齿象的研究（见前面的脚注）可能正好提供了所需的反证。随着近乎完美的周期性的到来，规则发生了很大的变化。由于已经有一个很长的生命周期，地面上的捕食者变得吃饱了，地下的捕食者被剥夺了食物，每一个周期性的出现（劳埃德和戴巴斯，1966年）。猎物现在可以进化出有勇无谋的捕食行为，特别是当旧的行为模式可能与人口密度极大提高时的繁殖需求不相容时。最严厉的选择性惩罚现在是针对那些未能随多数沿着出现的个体;在这种情况下，将选择延长或缩短生命周期。然而，在两个具有同样完美周期的竞争种群之间，较短的生命周期仍然具有优势。因此，我们预计，13年的育雏现在应该取代17年的，只要它们的范围是连续的，例如，XIX和XXIII取代了Ozarks的IV。图7A-B和6 G）。这一想法显然可以通过对未来突发事件和历史记录的详细测绘来检验。在向周期性进化的过程中，发育期的表型变异将获得以前从未有过的适应不良的意义。未成熟的周期性幼虫在大小上是可变的，这一事实（图1）一定意味着这些物种具有某种特殊的生理机制（即，除了非常一致的增长率之外的其他东西），这确保了13年或17年后的种群会一起出现--例如，某种类似于“计数”滞育的机制。阐明这种生理机制本身就是一个值得研究的目标。生态学理论预测，在任何非周期性的植物中都不会发现这种机制，因为没有周期性就没有选择优势。因此，我们需要了解一些关于非周期性蝉的发育期的变异性以及平均持续时间。回顾生理计时机制和周期性完善之前的进化阶段，我们可以想象，为了防止早期的周期性自行雅阁，强选择是必要的。当然，其强度取决于发育期的变异性有多大（图2）。我们还可以想象，在“原周期性”蝉和它们的捕食者之间发生的种群相互作用，是人们现在不希望看到的。如果知了在地面上出现几天...
As any scientist knows, a theory must not be judged by its plausibility or lack of it, but by how well it can anticipate new discoveries. The most important things for us to summarize, therefore, are the new things to look for. We need to know a great deal more about the developmental periods of non-periodical cicadas. On purely demographic grounds, a long pre-reproductive period should be a severe disadvantage; other things being equal, it should be strongly selected against. In view of the data in Table 2, one must postulate some counter-advantages for the long developmental periods characteristic of cicadas. As one hypothesis, we suggest in Table 3 a counter-advantage connected with loud song, large size, and obligately slow feeding. This idea could be exploded by finding a large cicada with a short life cycle, provided its feeding habits are typical of cicadas in general. The current work of Anderson and Shorey with Diceroprocta apache on asparagus roots (see earlier footnote) may provide exactly the disproof that is needed. With the advent of nearly-perfect periodicity, the rules are considerably changed. Given that there already is a long life cycle, the above-ground predators become satiated, and the below-ground ones deprived of food, by every periodical emergence (Lloyd and Dybas, 1966). The prey can now evolve predator-foolhardy behavior, especially as old behavior patterns may be incompatible with the demands of reproduction at enormously elevated population densities. The most severe selective penalties are now levied against those individuals that fail to emerge along with the majority; either a lengthening or shortening of the life cycle would be selected against under these circumstances. As between two competing cicada populations with equally perfect periodicities, however, the shorter life cycle should still have an advantage. Thus, we anticipate that 13-year broods should now be displacing 17-year ones wherever their ranges are contiguous, as, for example, XIX and XXIII supplanting IV in the Ozarks (cf. Figs. 7A-B and 6G). This idea can obviously be tested by detailed mapping of future emergences and historical records. In the course of evolution towards periodicity, phenotypic variability in the developmental period would acquire a maladaptive significance that it could never have had before. The fact that immature periodical cicada nymphs are as variable in size as they are (Fig. 1) must mean that these species have some special physiological mechanism (i.e., something other than a very uniform growth rate) which insures that the nymphs will emerge together after 13 or 17 years-some mechanism like "counting" diapauses, for example. The elucidation of this physiological mechanism is a worthwhile research objective in its own right. The ecological theory predicts that no such mechanism will be found in any non-periodical cicada, because it would have no selective advantage without the periodicity. We need, therefore, to know something about the variability, as well as the mean duration, of developmental periods in non-periodical cicadas. Looking back to an evolutionary stage before the physiological timing mechanism and the periodicity were perfected, we can imagine that strong selection would have been necessary in order to prevent the incipient periodicity from disappearing of its own accord. How strong would depend, of course, on how great was the variability in the developmental period (Fig. 2). We can also imagine population interactions taking place between "protoperiodical" cicadas and their predators that one would not expect to see taking place now. If cicadas were to appear above ground for several …