Invasive ecosystem engineers change habitat attributes and species abundance, affecting the structure of invaded communities. In the Mar Chiquita coastal lagoon (37° 40′S, 57° 23°W), the invasive reef-building polychaete Ficopomatus enigmaticus (Fauvel, 1823) generates a heterogeneous environment with habitats of variable complexity: the reefs themselves (high complexity), the sediment surrounding the reefs (low complexity), and the substrate from the areas without reefs (intermediate complexity). Our objective was to compare the macrofaunal assemblages along the whole complexity gradient. We hypothesized that individuals' abundance, diversity, species richness, and evenness of the macrofaunal assemblages increase with habitat complexity, since more complex habitats may represent greater availability of suitable spaces. The composition of the species assemblage was compared through monthly field samplings in each of the three habitats. Results showed that individuals' abundance increased with habitat complexity. In addition, amphipods were the most abundant group in the reefs, while ostracods were the most abundant group in the sediment surrounding the reefs and that from reef-free areas. However, community parameters were occasionally similar between the reefs and the sediment from reef-free areas, depending on the month considered. Our study suggests that the invasion of F. enigmaticus changed the macrofaunal assemblages and the individuals' abundances by providing a high complexity substrate, but also, and less predictably, by increasing habitat heterogeneity, highlighting the importance of including both dimensions of habitat structure in the study of invasions by ecosystem engineers.

入侵的生态系统工程师改变了栖息地的属性和物种的丰富度，影响了入侵社区的结构。在Mar Chiquita沿海泻湖（南纬37°40′，西纬57°23°）中，侵入性礁建造多头鱼类Ficopomatus enigmaticus（Fauvel，1823年）产生了一个具有多种多样的栖息地的异质环境：礁石本身（高复杂性），礁石周围的沉积物（低复杂性）以及无礁石区域的底物（中等复杂性）。我们的目的是在整个复杂度梯度上比较大型动物群。我们假设个体的丰富度，多样性，物种丰富度以及大型动物群落的均匀性会随着栖息地复杂性的增加而增加，因为更复杂的栖息地可能代表了更多合适的空间。通过在三个生境中每个月的田间采样比较了物种集合的组成。结果表明，个体的丰度随着栖息地的复杂性而增加。此外，两栖类动物是珊瑚礁中数量最多的一群，而在礁石周围和无礁石地区的沉积物中，兽脚类动物最多。但是，根据所考虑的月份，珊瑚礁和无珊瑚礁地区的沉积物之间的群落参数有时会相似。我们的研究表明，F. enigmaticus通过提供高复杂性的底物改变了大型动物群落和个体的丰度，但通过增加栖息地异质性也难以预测，这突出了在生态系统工程师进行入侵研究中包括栖息地结构两个维度的重要性。