Evolution of Photoperiodic Time Measurement in the Pitcher- Plant Mosquito, Wyeomyia smithii

猪笼草蚊子 Wyeomyia smithii 光周期时间测量的演变

• 批准号: 9814438
• 负责人: William Bradshaw
• 金额: $ 36万
• 依托单位: University of Oregon Eugene
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-06-15 至 2004-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9814438&HistoricalAwards=false
• 关键词: Evolution; Photoperiodic; Time; Measurement; Pitcher

A wide variety of plants and animals use the length of day to synchronize theirdevelopment and reproduction with the warm days of summer and to synchronize their entry intohibernation in advance of the cold days of winter. At more northern latitudes, winter arrivesearlier when days are longer than at more southern latitudes. Consequently, northern organismsrespond to longer daylengths to switch from active development to hibernation in anticipation ofthe forthcoming winter. Many temperate plants and animals, including some of the mostproblematic agricultural pests in the United States, originated from more tropical latitudes ormigrated north after the last ice age. This migration required evolving the appropriate responsesto daylength before the immigrants could thrive in their new northern habitats. Thus, evolvedresponses to daylength to cue the seasonal programming of development, reproduction, andhibernation represent one of the most pervasive and important adaptations of temperateorganisms. The question then remains as to how they do it. What is the physiological basis for themeasuring of daylength within and between geographically distant populations? Are thephysiological processes that underlie genetic variation for day-length measuring withinpopulations the same processes that change over geographic distances; i.e., does understandinggenetic variation in the physiological clock within populations permit us to predict how thesepopulations might evolve in the future? The PIs have pursued these questions in temperatepopulations of a formerly tropical mosquito. The PIs have found that the internal biological clock(circadian rhythm) plays a role in the day-length measuring process in southern populations; but,the expression of the circadian clock declines with increasing latitudes so that northernpopulations measure day length with essentially a physiological hourglass. Yet, when unrelatedpopulations are crossed, their offspring show a reversion to the southern or ancestral switchingdaylength. This grant will help the PIs to determine whether reversion to the ancestral daylength also brings out the ancestral expression of the circadian clock. In addition to contributing to our understanding of the genetic and physiological basis foradaptive evolution of biological time measurement, results of this study have implications forphysiological adaptation to changing environments in general. If vestigial physiologicalcapabilities reside covertly within populations, physiological adaptation to environmental changemay proceed far more rapidly than would be predicted from present-day, overt genetic variationfor that trait in a population. If these covert capabilities are relics from ancestral genes lyinglatent in extant populations, then response to selection may proceed faster towards ancestral thantowards new capabilities. Hence, predicting the rate of evolution in response to environmentalchange such as global warming may depend critically upon understanding the historical role ofmasked or covert genes in physiological adaptation.

各种各样的植物和动物利用白天的长度与夏季温暖的日子同步发育和繁殖，并在冬季寒冷的日子之前同步进入冬眠。在更北纬的地方，冬天来得更早，白天也比更南纬的地方更长。因此，北方生物对较长的白天长度做出反应，以从活跃发育转向冬眠，以应对即将到来的冬天。许多温带植物和动物，包括美国一些最严重的农业害虫，起源于更热带的纬度地区，或者在上一个冰河时代之后向北迁移。这种迁徙需要进化出对白昼长度的适当反应，才能在新的北方栖息地茁壮成长。因此，进化对白昼长度的反应，以提示发育、繁殖和冬眠的季节性程序，代表了温带生物最普遍和最重要的适应之一。接下来的问题是他们是如何做到的。在地理上相距遥远的种群内部和种群之间测量白昼长度的生理基础是什么？在种群内昼夜长度测量的遗传变异背后的生理过程是否与地理距离变化的过程相同？也就是说，了解种群内生理时钟的遗传变异是否允许我们预测这些种群未来可能如何进化？pi在一种原热带蚊子的温度种群中研究了这些问题。pi发现，内部生物钟（昼夜节律）在南方人群的日长测量过程中起作用；但是，昼夜节律时钟的表达随着纬度的增加而下降，因此北方人口基本上用生理沙漏来测量一天的长度。然而，当不相关的种群进行杂交时，它们的后代表现出向南方或祖先切换白天长度的回归。这笔拨款将帮助pi确定恢复到祖先的日长是否也会带来生物钟的祖先表达。除了有助于我们理解生物时间测量适应性进化的遗传和生理基础外，本研究的结果还对生物适应不断变化的环境具有重要意义。如果退化的生理能力隐藏在种群中，那么对环境变化的生理适应可能会比从当前种群中该特征的显性遗传变异所预测的要快得多。如果这些隐蔽的能力是祖先基因的遗迹，潜伏在现存种群中，那么对选择的反应可能会更快地向祖先的能力发展，而不是向新能力发展。因此，预测响应环境变化（如全球变暖）的进化速度可能主要取决于对生理适应中隐藏或隐蔽基因的历史作用的理解。