Thomsen Mads S, Hildebrand Thomas, South Paul M, Foster Travis, Siciliano Alfonso, Oldach Eliza, Schiel David R
Marine Ecology Group School of Biological Sciences University of Canterbury Christchurch New Zealand; School of Plant Biology & UWA Oceans Institute University of Western Australia Crawley WA Australia.
Marine Ecology Group School of Biological Sciences University of Canterbury Christchurch New Zealand.
Ecol Evol. 2016 Oct 21;6(22):8291-8303. doi: 10.1002/ece3.2499. eCollection 2016 Nov.
Many studies have documented habitat cascades where two co-occurring habitat-forming species control biodiversity. However, more than two habitat-formers could theoretically co-occur. We here documented a sixth-level habitat cascade from the Avon-Heathcote Estuary, New Zealand, by correlating counts of attached inhabitants to the size and accumulated biomass of their biogenic hosts. These data revealed predictable sequences of habitat-formation (=attachment space). First, the bivalve provided habitat for green seaweeds () that provided habitat for trochid snails in a typical estuarine habitat cascade. However, the trochids also provided habitat for the nonnative bryozoan that provided habitat for the red seaweed that provided habitat for more trochids, thereby resetting the sequence of the habitat cascade, theoretically in perpetuity. is here the basal habitat-former that controls this "long" cascade. The strength of facilitation increased with seaweed frond size, accumulated seaweed biomass, accumulated shell biomass but less with shell size. We also found that attached to all habitat-formers, trochids attached to and and and predominately attached to trochids. These "affinities" for different habitat-forming species probably reflect species-specific traits of juveniles and adults. Finally, manipulative experiments confirmed that the amount of seaweed and trochids was important and consistent regulators of the habitat cascade in different estuarine environments. We also interpreted this cascade as a habitat-formation network that describes the likelihood of an inhabitant being found attached to a specific habitat-former. We conclude that the strength of the cascade increased with the amount of higher-order habitat-formers, with differences in form and function between higher and lower-order habitat-formers, and with the affinity of inhabitants for higher-order habitat-formers. We suggest that long habitat cascades are common where species traits allow for physical attachment to other species, such as in marine benthic systems and old forest.
许多研究记录了栖息地级联效应，即两种共生的栖息地形成物种控制着生物多样性。然而，理论上可能会有两种以上的栖息地形成物种同时出现。我们在此记录了新西兰埃文 - 希思科特河口的六级栖息地级联效应，方法是将附着生物的数量与其生物源宿主的大小和累积生物量相关联。这些数据揭示了可预测的栖息地形成序列（=附着空间）。首先，双壳贝类为绿藻提供了栖息地，而绿藻又在典型的河口栖息地级联效应中为蝾螺提供了栖息地。然而，蝾螺也为非本地苔藓虫提供了栖息地，苔藓虫又为红藻提供了栖息地，红藻进而为更多的蝾螺提供了栖息地，从而从理论上永久性地重置了栖息地级联效应的序列。在此，双壳贝类是控制这种“长”级联效应的基础栖息地形成者。促进作用的强度随着海藻叶状体大小、累积海藻生物量、累积贝壳生物量的增加而增加，但随着贝壳大小的增加而减弱。我们还发现，[物种名称1]附着于所有栖息地形成者，蝾螺附着于[物种名称1]和[物种名称2]，而[物种名称3]和[物种名称4]主要附着于蝾螺。对不同栖息地形成物种的这些“亲和力”可能反映了幼体和成体的物种特异性特征。最后，操纵实验证实，海藻和蝾螺的数量是不同河口环境中栖息地级联效应的重要且一致的调节因素。我们还将这种级联效应解释为一个栖息地形成网络，该网络描述了一个生物附着于特定栖息地形成者的可能性。我们得出结论，级联效应的强度随着高阶栖息地形成者数量的增加、高阶和低阶栖息地形成者在形式和功能上的差异以及生物对高阶栖息地形成者的亲和力而增加。我们认为，在物种特征允许物理附着于其他物种的地方，如海洋底栖系统和老龄森林中，长栖息地级联效应很常见。
