Multidimensional niche differentiation might increase the stability of coexistence by reducing overall niche overlap which might have implications on the dynamics of biological invasions. The oligohaline Baltic Seais inhabited by three native and one invasive corophiid amphipod species. These filter feeding crustaceans differ in their substrate preferences and salinity optima which could potentially allow their robust coexistence. However, recent theory predicts that competing species must diverge across all non-substitutable resources (e.g., food and space). We have measured the filter mesh size in the four species (i.e., the distance between bristles on the filtering setae), revealing considerable differences among the three natives (Apocorophium lacustre, Corophium multisetosum and C. volutator), whereas the invasive Chelicorophium curvispinum showed strong overlap with A. lacustre. Theory suggests that the four species cannot coexist robustly due to their overlap in food particle size irrespective of differences in their salinity optima and substrate preferences which is in accordance with observations of local extinctions of A. lacustre. Nevertheless, the stability ensuing from the multidimensional niche differentiation might delay competitive exclusion; i.e., the spatial separation by salinity and substrate types might decrease the intensity of competition for food. Our data for co-occurring populations indicate that A. lacustre might be able to decrease its filter mesh size overlap with C. curvispinum by character displacement and its broader salinity tolerance also might help the native species to persist in the region. However, the niche shift of the species might increase its overlap with C. multisetosum.

多维生态位分化可能会通过减少整体生态位重叠而增加共存的稳定性，这可能会对生物入侵的动力学产生影响。寡盐波罗的海（Baltic Seais）栖息着三种原生和一种侵入性拟螺旋体两栖纲动物。这些滤食性甲壳类动物的底物偏好和最佳盐度有所不同，这可能潜在地使其稳健地共存。但是，最近的理论预测，竞争物种必须在所有不可替代的资源（例如食物和空间）之间扩散。我们已经测量了这四个物种的滤网尺寸（即，刚毛刚毛之间的距离），揭示了三个原生动物（Apocorophium lacustre，Corophium multisetosum）之间的显着差异。和C. volutator），而侵入性Chelicorophium curvispinum与A. lacustre显示出强烈的重叠。理论表明，这四个物种由于其食物粒度的重叠而无法稳健地共存，而与盐度最佳值和底物偏好的差异无关，这与对A. lacustre的局部灭绝的观察一致。然而，多维生态位分化所带来的稳定性可能会延迟竞争排斥。即，盐度和底物类型的空间分隔可能会降低食物竞争的强度。我们针对共生种群的数据表明，A。lacustre也许可以通过字符移位来减少其与弯孢梭菌重叠的滤网尺寸，并且其更宽的耐盐性还可以帮助本地物种在该地区生存。但是，该物种的生态位转移可能会增加其与多角梭菌的重叠。