Université de Lyon, Lyon, France.
PLoS Negl Trop Dis. 2010 May 25;4(5):e691. doi: 10.1371/journal.pntd.0000691.
The developmental time of vector insects is important in population dynamics, evolutionary biology, epidemiology and in their responses to global climatic change. In the triatomines (Triatominae, Reduviidae), vectors of Chagas disease, evolutionary ecology concepts, which may allow for a better understanding of their biology, have not been applied. Despite delay in the molting in some individuals observed in triatomines, no effort was made to explain this variability.
We applied four methods: (1) an e-mail survey sent to 30 researchers with experience in triatomines, (2) a statistical description of the developmental time of eleven triatomine species, (3) a relationship between development time pattern and climatic inter-annual variability, (4) a mathematical optimization model of evolution of developmental delay (diapause).
85.6% of responses informed on prolonged developmental times in 5(th) instar nymphs, with 20 species identified with remarkable developmental delays. The developmental time analysis showed some degree of bi-modal pattern of the development time of the 5(th) instars in nine out of eleven species but no trend between development time pattern and climatic inter-annual variability was observed. Our optimization model predicts that the developmental delays could be due to an adaptive risk-spreading diapause strategy, only if survival throughout the diapause period and the probability of random occurrence of "bad" environmental conditions are sufficiently high.
CONCLUSIONS/SIGNIFICANCE: Developmental delay may not be a simple non-adaptive phenotypic plasticity in development time, and could be a form of adaptive diapause associated to a physiological mechanism related to the postponement of the initiation of reproduction, as an adaptation to environmental stochasticity through a spreading of risk (bet-hedging) strategy. We identify a series of parameters that can be measured in the field and laboratory to test this hypothesis. The importance of these findings is discussed in terms of global climatic change and epidemiological consequences.
载体昆虫的发育时间在种群动态、进化生物学、流行病学以及它们对全球气候变化的反应中都很重要。在传播恰加斯病的三锥虫（Triatominae，Reduviidae）中，尚未应用进化生态学概念来更好地了解它们的生物学特性。尽管在一些三锥虫个体中观察到蜕皮延迟，但并未对此变异性进行解释。
我们应用了四种方法：（1）向 30 位具有三锥虫经验的研究人员发送电子邮件调查；（2）对 11 种三锥虫物种的发育时间进行统计描述；（3）发育时间模式与气候年际变异性之间的关系；（4）发育延迟（滞育）进化的数学优化模型。
85.6%的回复者报告称，5 龄若虫的发育时间延长，有 20 个物种表现出明显的发育延迟。发育时间分析显示，在 11 个物种中的 9 个物种中，5 龄的发育时间具有一定程度的双峰模式，但未观察到发育时间模式与气候年际变异性之间的趋势。我们的优化模型预测，如果滞育期内的存活率以及“恶劣”环境条件随机发生的概率足够高，则发育延迟可能是一种适应性风险分散的滞育策略。
结论/意义：发育延迟可能不是发育时间的简单非适应性表型可塑性，而是一种与与推迟繁殖开始有关的生理机制相关的适应性滞育形式，是通过风险分散（风险对冲）策略适应环境随机性的一种形式。我们确定了一系列可以在现场和实验室中测量的参数，以检验这一假设。从全球气候变化和流行病学后果的角度讨论了这些发现的重要性。
