Department of Forest Science, Graduate School of Agriculture , Hokkaido University , N9 W9 Sapporo, Hokkaido 060-8589, Japan.
R Soc Open Sci. 2015 Jul 8;2(7):150033. doi: 10.1098/rsos.150033. eCollection 2015 Jul.
Understanding how human-altered landscapes affect population connectivity is valuable for conservation planning. Natural connectivity among wetlands, which is maintained by floods, is disappearing owing to farmland expansion. Using genetic data, we assessed historical changes in the population connectivity of the ninespine stickleback within a human-altered wetland system. We predicted that: (i) the contemporary gene flow maintained by the artificial watercourse network may be restricted to a smaller spatial scale compared with the gene flow preceding alteration, and (ii) the contemporary gene flow is dominated by the downstream direction owing to the construction of low-head barriers. We evaluated the potential source population in both timescales. Seventeen studied populations were grouped into four genetically different clusters, and we estimated the migration rates among these clusters. Contemporary migration was restricted to between neighbouring clusters, although a directional change was not detected. Furthermore, we consistently found the same potential source cluster, from past to present, characterized by large amounts of remnant habitats connected by artificial watercourses. These findings highlight that: (i) artificial connectivity can sustain the short-distance connectivity of the ninespine stickleback, which contributes to maintaining the potential source populations; however, (ii) population connectivity throughout the landscape has been prevented by agricultural developments.
了解人类改变的景观如何影响种群连通性对于保护规划很有价值。由于耕地扩张，湿地之间由洪水维持的自然连通性正在消失。本研究使用遗传数据评估了九刺鱼在人类改变的湿地系统中种群连通性的历史变化。我们预测：(i)与改变前相比，由人工水道网络维持的当代基因流可能受到限制，空间尺度较小；(ii)由于低水头障碍物的建造，当代基因流主要是下游方向的。我们在两个时间尺度上评估了潜在的源种群。17 个研究种群被分为四个在遗传上不同的聚类，我们估计了这些聚类之间的迁移率。当代的迁移仅限于相邻的聚类之间，尽管没有检测到方向性变化。此外，我们一直发现相同的潜在源聚类，从过去到现在，其特征是大量由人工水道连接的残余栖息地。这些发现表明：(i)人工连通性可以维持九刺鱼的短距离连通性，有助于维持潜在的源种群；然而，(ii)农业发展阻止了整个景观的种群连通性。
