Abstract Between 1980 and 2012, successive arrivals by three alien ecosystem engineers on a rocky shore community at Marcus Island on the west coast of South Africa led to substantial changes in species composition and diversity. An ecosystem analysis of this open intertidal system was developed using Ecopath with Ecosim to determine the impacts of these aliens and the services they provide on the native community. A baseline Ecopath model of the community in 2015 was generated using values of biomass, production/biomass, consumption/biomass and the dietary composition of 30 functional groups. Ecosim, a time-dynamic modelling routine, was then used to simulate the changes in biomass of native species. A 1980 model (pre-invasion) was constructed and 22 simulations were run up to 2015 by systematically adding (1) biomass time series for non-native species; (2) relative biomass time series for native species; (3) mediation functions that mimicked biomass impacts due to changes in substrate, shelter and feeding grounds created by the alien ecosystem engineers; and (4) the effects of wave action as a source of mortality. Positive or negative influences of these ecological processes on diversity and the final biomasses of all groups in 2015 were assessed. Trophic impacts by the alien species affected diversity and biomass at the end of all simulations, but the addition of shelter or a combination of all three ecosystem services provided by ecosystem engineers (shelter, substrate and feeding grounds) resulted in 2015 model ecosystems that most closely matched the diversity and individual group biomasses empirically measured on Marcus Island in 2015. Wave action had only a minor impact. Marcus Island's rocky shore community was therefore driven mainly by the fixed input of alien species biomass and made more realistic by the incorporation of their ecosystem services. However, structural complexity and zonation, explored in a follow-up paper invoking spatial modelling, need to be represented for a more complete realisation of the ecosystem.

中文翻译：

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模拟外星生态系统工程师对岩石海岸岛屿的营养和结构影响的变化

摘要 1980 年至 2012 年间，三位外来生态系统工程师连续抵达南非西海岸马库斯岛的岩石海岸群落，导致物种组成和多样性发生重大变化。使用 Ecopath 和 Ecosim 对这个开放的潮间带系统进行了生态系统分析，以确定这些外星人及其提供的服务对本地社区的影响。2015 年社区的基线生态路径模型是使用生物量、生产/生物量、消费/生物量和 30 个功能组的饮食组成的值生成的。然后使用时间动态建模程序 Ecosim 来模拟本地物种生物量的变化。通过系统地添加 (1) 非本地物种的生物量时间序列，构建了 1980 年模型（入侵前）并运行了 22 次模拟，直至 2015 年；(2) 本地物种的相对生物量时间序列；(3) 由于外来生态系统工程师创造的基质、庇护所和觅食地的变化，模拟生物量影响的中介功能；(4) 波浪作用作为死亡源的影响。评估了这些生态过程对 2015 年所有群体的多样性和最终生物量的正面或负面影响。外来物种的营养影响在所有模拟结束时都会影响多样性和生物量，但增加庇护所或生态系统工程师提供的所有三种生态系统服务（庇护所、底物和觅食地）导致 2015 年模型生态系统与 2015 年在马库斯岛凭经验测量的多样性和个体群体生物量最匹配。波浪作用只有很小的影响。因此，马库斯岛的岩石海岸群落主要由外来物种生物量的固定输入驱动，并通过纳入其生态系统服务而变得更加现实。然而，在后续论文中探讨的结构复杂性和分区需要空间建模，以更完整地实现生态系统。因此，岩岸群落主要由外来物种生物量的固定输入驱动，并通过纳入其生态系统服务而变得更加现实。然而，在后续论文中探讨的结构复杂性和分区需要空间建模，以更完整地实现生态系统。因此，岩岸群落主要由外来物种生物量的固定输入驱动，并通过纳入其生态系统服务而变得更加现实。然而，在后续论文中探讨的结构复杂性和分区需要空间建模，以更完整地实现生态系统。