Finlay Ross, Poole Russell, Coughlan Jamie, Phillips Karl P, Prodöhl Paulo, Cotter Deirdre, McGinnity Philip, Reed Thomas E
School of Biological, Earth and Environmental Sciences University College Cork Cork Ireland.
Marine Institute Furnace Newport Ireland.
Ecol Evol. 2020 Feb 7;10(4):1762-1783. doi: 10.1002/ece3.5937. eCollection 2020 Feb.
The degree of natal philopatry relative to natal dispersal in animal populations has important demographic and genetic consequences and often varies substantially within species. In salmonid fishes, lakes have been shown to have a strong influence on dispersal and gene flow within catchments; for example, populations spawning in inflow streams are often reproductively isolated and genetically distinct from those spawning in relatively distant outflow streams. Less is known, however, regarding the level of philopatry and genetic differentiation occurring at microgeographic scales, for example, where inflow and outflow streams are separated by very small expanses of lake habitat. Here, we investigated the interplay between genetic differentiation and fine-scale spawning movements of brown trout between their lake-feeding habitat and two spawning streams (one inflow, one outflow, separated by <100 m of lake habitat). Most (69.2%) of the lake-tagged trout subsequently detected during the spawning period were recorded in just one of the two streams, consistent with natal fidelity, while the remainder were detected in both streams, creating an opportunity for these individuals to spawn in both natal and non-natal streams. The latter behavior was supported by genetic sibship analysis, which revealed several half-sibling dyads containing one individual that was sampled as a fry in the outflow and another that was sampled as fry in the inflow. Genetic clustering analyses in conjunction with telemetry data suggested that asymmetrical dispersal patterns were occurring, with natal fidelity being more common among individuals originating from the outflow than the inflow stream. This was corroborated by Bayesian analysis of gene flow, which indicated significantly higher rates of gene flow from the inflow into the outflow than vice versa. Collectively, these results reveal how a combination of telemetry and genetics can identify distinct reproductive behaviors and associated asymmetries in natal dispersal that produce subtle, but nonetheless biologically relevant, population structuring at microgeographic scales.
在动物种群中，出生地留居相对于出生地扩散的程度具有重要的人口统计学和遗传学后果，并且在物种内部通常差异很大。在鲑科鱼类中，湖泊已被证明对集水区内的扩散和基因流动有强烈影响；例如，在流入溪流中产卵的种群通常与在相对较远的流出溪流中产卵的种群生殖隔离且基因不同。然而，对于在微观地理尺度上发生的留居水平和遗传分化情况，例如流入和流出溪流被非常小的湖泊栖息地隔开的地方，人们了解较少。在这里，我们研究了褐鳟在其湖泊摄食栖息地和两条产卵溪流（一条流入，一条流出，被<100米的湖泊栖息地隔开）之间的遗传分化和精细尺度产卵运动之间的相互作用。在产卵期期间随后检测到的大多数（69.2%）带有湖泊标记的鳟鱼仅在两条溪流中的一条中被记录到，这与出生地忠诚一致，而其余的在两条溪流中都被检测到，这为这些个体在出生地和非出生地溪流中产卵创造了机会。这种行为得到了遗传同胞关系分析的支持，该分析揭示了几个半同胞对，其中包含一个在流出溪流中作为鱼苗被采样的个体和另一个在流入溪流中作为鱼苗被采样的个体。结合遥测数据的遗传聚类分析表明正在发生不对称扩散模式，与来自流入溪流的个体相比，来自流出溪流的个体中出生地忠诚更为常见。基因流动的贝叶斯分析证实了这一点，该分析表明从流入到流出的基因流动速率明显高于反之亦然。总体而言，这些结果揭示了遥测和遗传学的结合如何能够识别不同的生殖行为以及出生地扩散中相关的不对称性，这些不对称性在微观地理尺度上产生了微妙但仍然具有生物学相关性的种群结构。
