In the past 24 years, the Southwestern Indian Ocean (SWIO) region has lost about 4% of its mangroves due to unsustainable extraction, land clearance for agriculture and climate change impacts. Since this loss risks fragmenting mangrove fauna, this study analysed 179 D‐loop sequences (329 base pairs) of Barred mudskipper (Periophthalmus argentilineatus) sampled from estuarine mangroves in the SWIO to test two hypotheses: (1) whether Barred mudskipper populations in the region display genetic connectivity along the fragmented mangroves and (2) whether these populations have experienced demographic declines in recent history. The populations showed low and insignificant indices of genetic differentiation (FST = −0.00068, p > 0.05; ΦST = 0.005, p > 0.05), and haplotypes from different localities did not cluster according to their geographical origins. Similarly, Bayesian phylogenetic analysis grouped all SWIO haplotypes into one cluster, suggesting the hypothesis of genetic interconnectedness could not be rejected. Furthermore, the populations showed high haplotype diversity (0.96 ± 0.007) combined with low nucleotide diversity (1.09 ± 0.61%). They also showed significant negative Tajima's D values (−1.71, p < 0.02) and a unimodal mismatch distribution, indicating the hypothesis of demographic expansion post a historical bottleneck could not be rejected. Nevertheless, the Bayesian skyline plot indicated an increase in population size post‐bottleneck, suggesting an ongoing recovery. These findings indicate that, despite varying management approaches in the SWIO, Barred mudskipper populations exhibit genetic exchange that transcends geographical and administrative borders. This implies that their populations should be considered a single stock within the region. These findings underscore the need for coordinated management approaches among the SWIO countries. This is crucial because inconsistencies in conservation measures across borders could disrupt the population's interconnectedness, potentially impacting their genetic integrity and long‐term survival.

中文翻译：

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超越国界：西南印度洋斑弹涂鱼（Periothoughmus argentilineatus）种群之间显着的遗传同质性

在过去 24 年中，由于不可持续的开采、农业土地清理和气候变化的影响，西南印度洋 (SWIO) 地区约 4% 的红树林消失。由于这种损失可能导致红树林动物群支离破碎，本研究分析了斑弹涂鱼的 179 个 D 环序列（329 个碱基对）（阿根廷眼周鱼）从 SWIO 的河口红树林中取样，以检验两个假设：（1）该地区的斑弹涂鱼种群是否沿着支离破碎的红树林表现出遗传连通性；（2）这些种群在近代历史中是否经历了人口数量下降。这些群体表现出较低且不显着的遗传分化指数（F英石= −0.00068,p> 0.05；Φ英石= 0.005,p> 0.05），来自不同地点的单倍型并未根据其地理起源进行聚类。类似地，贝叶斯系统发育分析将所有 SWIO 单倍型分组为一个簇，表明不能拒绝遗传互连性的假设。此外，群体表现出高单倍型多样性（0.96±0.007）和低核苷酸多样性（1.09±0.61％）。他们还表现出显着的负面田岛D值（−1.71，p< 0.02）和单峰错配分布，表明历史瓶颈后人口扩张的假设不能被拒绝。然而，贝叶斯天际线图表明，瓶颈过后人口规模有所增加，表明经济正在持续复苏。这些发现表明，尽管 SWIO 的管理方法不同，弹涂鱼种群仍表现出超越地理和行政边界的基因交换。这意味着它们的种群应被视为该地区内的单一种群。这些发现强调了 SWIO 国家之间采取协调管理方法的必要性。这一点至关重要，因为跨境保护措施的不一致可能会破坏种群的相互联系，从而可能影响其遗传完整性和长期生存。