README.txt from Multiple lines and levels of evidence for avian zoochory promoting fish colonization of artificial lakes

Understanding how obligate freshwater organisms colonize seemingly isolated ecosystems has long fascinated ecologists. While recent investigations reveal that fish eggs can survive the digestive tract of birds and successfully hatch once deposited, evidence for avian zoochory <i>in natura</i> is still lacking. Here, we used a multiple lines and levels of evidence approach to demonstrate plausible bird-mediated colonization of lakes by the European perch (<i>Perca fluviatilis</i>). We studied a set of newly-formed artificial lakes that the public is either prohibited to access because of gravel extraction or allowed to access (mainly for angling). The motivating observation is that a large proportion of prohibited-access lakes (&gt;80%) were colonized by European perch even though stocking by anglers and managers never occurred. Three supplementary lines of evidence supported avian zoochory. First, European perch spawning occurs when waterfowl abundance is very high. Second, European perch lays sticky eggs at shallow depths where they can be eaten by waterfowls or attached to their bodies. Third, genetic analyses suggested that European perch actually migrate among lakes, and that distances moved matches with daily flight range of foraging waterfowls. Together, multiple lines of evidence point to avian zoochory as a pathway for fish colonizing remote or newly-formed freshwater ecosystems.

专性淡水生物如何定植于看似孤立的生态系统，长久以来一直是生态学家们关注的核心议题。尽管近期研究证实，鱼卵可在鸟类消化道内存活并在被排出体外后成功孵化，但目前仍缺乏鸟类动物传播（avian zoochory）在自然状态下的直接证据。
本研究采用多维度、多层级证据研究范式，证实了欧洲河鲈（*Perca fluviatilis*）通过鸟类介导实现湖泊定植的可行性。我们选取了一批新形成的人工湖泊作为研究对象，这些湖泊因砾石开采活动对公众实施封闭管理，或对外开放（主要用于休闲垂钓）。一项关键观测结果显示：在未开展过垂钓者及管理人员人工放流的封闭管理湖泊中，超过80%的水体已被欧洲河鲈成功定植。
后续三项补充证据进一步支撑了鸟类动物传播假说：其一，欧洲河鲈的产卵期与水禽种群数量峰值时段高度重合；其二，欧洲河鲈会在浅水区产出黏性卵，这些卵既可被水禽吞食，也可附着于水禽体表；其三，遗传分析表明，欧洲河鲈确实会在不同湖泊间发生迁移，且其迁移距离与觅食水禽的每日飞行范围高度匹配。
综上，多项独立证据共同指向：鸟类动物传播是鱼类定植偏远或新形成淡水生态系统的关键途径。