Impact of the non-native locariid fish <i>Pterygoplichthys pardalis</i> in native fish community on a seasonal tropical floodplain in Mexico

The present study reports the seasonal dynamics of the fish community structure in the presence of a non-native fish (<i>Pterygoplichthys pardalis</i>) in tropical waterbodies of southern Mexico. The studied floodplain existed in both connected pools and disconnected pools “to the Palizada river”. Local fish fauna showed consistent assemblages across seasons, but among the 17 local fish species recorded, the non-native species <i>P</i>. <i>pardalis</i> showed the highest percentage of contribution to the fish community (ca. 20%). Conversely, the frequency of occurrence and density of the non-native species showed variation in relation to the type of waterbody and seasonality; its density was approximately four times higher in disconnected pools than in connected pools in the rainy season and its predominant size class in both pool types was 21-30 cm in standard length. Interestingly, the diversity of the native species was negatively related to the density of the non-native species, indicating that the presence of <i>P. pardalis</i> can be a factor involved in the decline of native fish diversity in these local communities. Currently, the possible impacts of the presence of <i>P. pardalis</i> on local fish diversity at the regional scale are unknown, but our results suggest that hydrological dynamics regulate the establishment of the non-native species in this region. However, future studies are needed to provide insights into the actual scenario of <i>P</i>. <i>pardalis</i> distribution in Yucatan Peninsula and the possible impacts on the native fish fauna in southern Mexico.本研究报道了墨西哥南部热带水域中，外来鱼类豹纹翼甲鲶（*Pterygoplichthys pardalis*）存在下的鱼类群落结构季节动态。本研究涉及的泛洪平原包含与帕利萨达河相连的连通水塘，以及与之隔离的孤立水塘两类生境。调查记录的17种本地鱼类中，其群落组成在各季节间保持相对稳定；但该外来鱼种豹纹翼甲鲶对鱼类群落的贡献占比最高，约为20%。与之相对的是，该外来鱼种的出现频率与种群密度随水体类型与季节变化呈现显著差异：雨季时孤立水塘中的种群密度约为连通水塘的4倍；两类水塘中该鱼种的优势体长组均为标准长21-30厘米。值得关注的是，本地鱼类多样性与该外来鱼种的种群密度呈显著负相关，表明豹纹翼甲鲶的入侵可能是导致这些本地群落鱼类多样性下降的影响因素之一。目前，该外来鱼种在区域尺度上对本地鱼类多样性的潜在影响尚未明确，但本研究结果显示，水文动态调控了该区域外来鱼种的定植过程。然而，未来仍需开展相关研究，以明确尤卡坦半岛地区豹纹翼甲鲶的实际分布格局，以及其对墨西哥南部本地鱼类区系的潜在影响。