TOWARDS AN INTEGRATIVE THEORY OF RECRUITMENT IN MARINE BENTHIC ORGANISMS

几十年来，生态学家已经记录了生物的分布和丰度，这些生物归因于死亡率、繁殖力和迁移的变化。对自然界中生物的丰度和分布（它们的“种群动态”）的这种基本了解对于保护和管理被开发物种的种群是至关重要的。人们日益认识到的一个方面是，早期生活史阶段在决定整个生境范围内物种的种群动态方面的重要性。近年来进行的生态生理学调查表明，少年/成年模式在一定程度上可以由早期生活史阶段的环境经验决定。在海洋环境中，考虑环境对早期生命阶段的影响是复杂的，因为对许多生物来说，早期生命阶段（幼虫）所处的环境与成虫不同。在许多海洋无脊椎动物中，包括商业捕捞的物种，如龙虾、螃蟹和扇贝，成虫生活在海床上（它们被称为底栖动物），而幼虫生活在浮游的上层环境中。在这个浮游时期，幼虫可能会离开父母的栖息地。然而，在某些时候，幼虫有必要找到一个合适的栖息地定居，并适应成年底栖生物的生活方式。这种生活史模式意味着成年繁殖和年轻阶段的招募通常是分离的，因此了解这些生物的种群动态特别具有挑战性。在过去的二十年里，生态学家建立了基于幼虫定居率变化和定居后过程的模型来了解海洋底栖无脊椎动物的种群动态。这些模型仅基于生物体的数量（如定居幼虫的数量），而不考虑某些幼虫是否比其他幼虫更好（即它们的质量）。在远洋浮游生物环境中，一系列的环境因素可能影响幼虫的“质量”。在幼虫期经历的次优食物、盐度、温度或亚致死污染暴露可通过对幼虫质量的影响影响幼年期的生存。幼虫质量在多大程度上改变了幼虫定居数量与幼鱼/成鱼丰度之间的关系尚不清楚。本项目利用潮间带藤壶作为模式物种来解决这一问题。该项目将调查苏格兰西海岸高和低海岸生产力地区幼虫质量的自然变化。这一观察方案将确定定居时幼虫质量差异的大小。在进行这些观察的同时，我们将使用实验室饲养的幼虫进行实地实验，以确定幼虫质量的差异如何影响定居者数量与成虫数量的相关模型。通过结合幼虫质量和幼虫数量的考虑，我们期望产生更准确的模型来理解种群动态。面对全球变化，需要一个关于影响海洋生物向成年种群补充的机制的一般理论，以便能够适当地管理自然资源。在被剥削的种群中，招募失败后通常会出现种群崩溃这一事实表明，幼虫过程在种群维持中起着核心作用。然而，对被开发和非开发物种的这一关键幼虫期及其与定居后过程的相互作用的了解仍然有限。拟议的项目是朝着整合两个独立的研究领域以帮助管理海洋种群迈出的重要一步。

For several decades, ecologists have documented the distribution and abundance of organisms that are attributed to variation in mortality, fecundity and migration. Such basic understanding of the abundance and distribution of organisms in nature (their 'population dynamics') is fundamental for conservation and to manage stocks of exploited species. One aspect which is gaining increasing recognition is the importance of early life history stages in determining population dynamics of species in a whole range of habitats. Eco-physiological investigations carried out during recent years have shown that juvenile/adult patterns can in part be determined by environmental experience of early life history stages. In the marine environment consideration of the effects of the environment on early life stages is complicated because for many organisms the early life stages (larvae) occupy a different environment from the adults. In many marine invertebrates including commercially fished species such as lobsters, crabs and scallops the adults live on the sea bed (they are described as benthic) while the larvae live in the planktonic pelagic environment. During this planktonic period larvae may disperse away from the parental habitat. However at some point it is necessary that larvae find a suitable habitat to settle and recruit to the adult benthic lifestyle. This life history pattern means that adult reproduction and the recruitment of young stages is often decoupled and hence understanding the population dynamics of these organisms is especially challenging. Over the past two decades ecologists have built models to understand population dynamics of marine benthic invertebrates based on variations in larval settlement rate in combination with post-settlement processes. These models are based only on the number of organisms (e.g number of settling larvae) without considering whether some larvae are better than others (i.e. their quality). In the pelagic planktonic environment a whole range of environmental factors may affect the 'quality' of larvae. Sub-optimal food, salinity, temperature or sub-lethal pollution exposure, experienced during the larval phase, can affect the survival of juvenile stages through effects on larval quality. The extent to which larval quality modifies the relationship between number of larval settlers and juvenile/adult abundance is not known. The present project addresses this issue using intertidal barnacles as model species. The project will investigate natural variation in larval quality over the west coast of Scotland in areas of high and low coastal productivity. This observational programme will determine the magnitude of differences in larval quality at settlement. In parallel to these observations we will perform field experiments, using larvae reared in the laboratory, to determine how differences in larval quality affect models relating number of settlers to number of adults. By combining larval quality with consideration of larval numbers we expect to produce more accurate models to understand population dynamics. In the face of global change a general theory of mechanisms affecting recruitment of marine organisms to adult populations is required to enable appropriate management of natural resources. The fact that failures of recruitment in exploited populations are usually followed by population breakdowns suggests that larval processes play a central role in population maintenance. However, the understanding of this critical larval phase and its interaction with post settlement process in exploited and non-exploited species is still limited. The proposed project is an important step toward integrating two separate fields of study to aid management of marine populations.