Aims

Rising sea-level following the Last Glacial Maximum lead to fragmentation of coastal limpet populations between islands of the Archipelago of Madeira. This fragmentation is reinforced by recent heavy exploitation reducing effective population size on Madeira Island. We use the limpet P. aspera to understand how the role of processes at different time scales (i.e. changes in the sea level and overexploitation) can influence the genetic composition of an extant species, relating these processes to reproductive phenology and seasonal shifts in ocean currents.

Location

Madeira Island, Porto Santo and Desertas (Archipelago of Madeira, NE Atlantic Ocean).

Taxon

The limpet Patella aspera.

Methods

Twelve microsatellite genetic markers were used. A power analysis was used to evaluate the power of the microsatellite markers to detect a signal of population differentiation. Long-term past migrations were assessed using a Bayesian Markov Montecarlo approach in the software MIGRATE-n to estimate mutation-scaled migration rates (M = m/μ; m, probability of a lineage immigrating per generation; μ, mutation rate). Two scenarios were evaluated using an Approximate Bayesian Computation (ABC) in the software DIYABC 2.1 (i) Scenario 1: considered a population scenario from a reduced Ne at time t₃ to a higher Ne at time t₂; and (ii) Scenario 2 considering a reduction of Ne from a time t₃ to a time t₂.

Results

Colonization of the archipelago by Portuguese settlers six centuries ago probably led to an important decrease in the genetic diversity of the species (N_e). Contemporary gene flow strongly support a pattern of high asymmetric connectivity explained by the reproductive phenology of the species and spatio-temporal seasonal changes in the ocean currents. Spatio-temporal reconstructions using Bayesian methods, including coalescent and Approximate Bayesian Computation (ABC) approaches, suggest changes in the migration patterns from highly symmetric to highly asymmetric connectivity with subtle population differentiation as consequence of post-glacial maximum sea level rise during the Holocene.

Main conclusions

Our results suggest that anthropogenic activity could have had serious effects on the genetic diversity of heavily exploited littoral species since the end of the Pleistocene, probably accelerating in recent years.

中文翻译：

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更新世扩张、人为压力和洋流：解开 1798 年马德拉群岛 Patella aspera Röding 过去和持续进化的历史

宗旨

末次盛冰期后海平面上升导致马德拉群岛岛屿之间沿海帽贝种群的分裂。最近的大量开采减少了马德拉岛上的有效人口规模，从而加剧了这种分裂。我们使用帽贝P. aspera来了解不同时间尺度的过程（即海平面变化和过度开发）如何影响现存物种的遗传组成，将这些过程与繁殖物候学和洋流的季节性变化联系起来.

地点

马德拉岛、圣港和德瑟塔斯（马德拉群岛，大西洋东北部）。

分类单元

帽贝髌骨叶树。

方法

使用了十二个微卫星遗传标记。使用功效分析来评估微卫星标记检测群体分化信号的功效。使用软件 MIGRATE-n 中的贝叶斯马尔可夫蒙特卡洛方法评估过去的长期迁移，以估计突变缩放迁移率（M  =  m / μ；m，每代谱系迁移的概率；μ，突变率）。使用软件 DIYABC 2.1 (i) 场景 1 中的近似贝叶斯计算 (ABC) 评估两种场景：考虑从t ₃时刻的N e减少到t ₂时刻的更高N e的人口场景; (ii) 情景 2 考虑将N e 从时间 t _{3 减少}到时间 t ₂。

结果

六个世纪前葡萄牙定居者对该群岛的殖民活动可能导致该物种的遗传多样性显着下降（N _e）。当代基因流强烈支持高度不对称连通性的模式，该模式由物种的繁殖物候和洋流的时空季节性变化来解释。使用贝叶斯方法进行的时空重建，包括合并和近似贝叶斯计算 (ABC) 方法，表明迁移模式从高度对称到高度不对称连接的变化，以及由于全新世冰河后最大海平面上升而导致的微妙的人口分化。

主要结论

我们的研究结果表明，自更新世末期以来，人为活动可能对严重开发的沿海物种的遗传多样性产生严重影响，并且可能在最近几年加速。