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GCE III - Key Finding in 2018

    The importance of foundation species in marshes

    Foundation species (FS) play important roles in many ecological systems, enhancing biodiversity, stability and multi-functionality. FS are generally habitat-formers such as trees and corals. In many cases FS facilitate the presence of secondary foundation species, which are habitat formers in their own right and may further modify the ecosystem. In southeastern salt marshes, Spartina alterniflora is the primary foundation species and the ribbed mussel, Geukensia demissa, acts as a secondary foundation species. The Angelini lab conducted a 6-month field experiment in which they added standard densities of mussels to evaluate whether patch configuration mediates their ecological effects. As reported in Crotty et al. (2018), they found that over 67% of response variables increased with clustering of mussels, responses that were driven by changes in patch characteristics (area-perimeter ratio, perimeter, and patch size). Thus, mussel configuration - by controlling the relative distribution of multidimensional patch interior and edge niche space - critically modulates this foundation species' effects on ecosystem structure, stability and function. In a separate study, Thomsen et al. (2018) conducted a meta-analysis of secondary FS to evaluate their effects on habitat-associated organisms (i.e. inhabitants). They found that secondary FS significantly enhanced the abundance and richness of inhabitants compared to primary FS alone. Finally, Borst et al. (2018) analyzed data from 58 food webs from seven terrestrial, freshwater and coastal systems and found that foundation species consistently enhanced food web complexity across the entire trophic network as compared to bare areas (Fig. 1). They suggest that the structure and stability of food webs often depends critically on non-trophic facilitation by foundation species. We helped organize a workshop on FS at the all-scientists meeting, and are helping to facilitate a cross-site comparison of FS across the LTER network.


    Fig. 1 (left) (A) Seven ecosystems were included in the study. (B) In each case, food webs were constructed for both bare and foundation species-dominated areas. (C) Nodes (i.e. species) were randomly removed until the species number matched the species number of the bare food webs. (right) The presence of foundation species consistently changed food web properties (mean SE) across ecosystems, including (A) species richness, (B) link density, and (C) connectance. The random removal of nodes created networks that corresponded well with the properties of real bare food webs. From Borst et al. 2018.


This material is based upon work supported by the National Science Foundation under grants OCE-9982133, OCE-0620959, OCE-1237140 and OCE-1832178. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.