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Foundation species traits that structure communities are rarely experimentally examined; thus, a predictive understanding of their functions lags behind patterns of observed species associations. Red mangrove Rhizophora mangle roots form complex living habitats that support diverse epibiont communities, making them a model system for testing links between variation in foundation species traits and associated biodiversity. Here, we compared epibiont community composition between living and non-living mangrove roots, as well as root mimics, to test how foundation species traits affect community structure. We also quantified the community structure of associated mobile invertebrates to examine their relationship with secondary foundation species (e.g. sponges, bivalves) that grow on the roots. After 14 mo of colonization and succession, substrate composition (i.e. mangrove, wood, PVC) had significant effects on community composition, richness, and abundance of sessile epibionts and mobile invertebrates. Non-living mangrove roots were 5 times more likely to deteriorate, and consequently had the lowest epibiont richness and abundance. We found strong positive relationships between mobile invertebrate richness and the abundance, measured as biomass, and richness of sponges and bivalves, suggesting that variation among roots in secondary foundation species play an important role in mediating mobile invertebrate community composition. This study highlights the functional role of habitat structure and how rapidly that function can be lost without biogenic maintenance. Our results indicate the importance of facilitation cascades in fostering diverse mobile invertebrate communities and highlight both advantages and limitations in using artificial structures in restoration programs.
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Functional redundancy buffers mobile invertebrates against the loss of foundation species on rocky shores
Foundation species are vital to the maintenance of biodiversity and ecosystem functioning in many systems. On rocky shores, rockweeds (large brown algae in the Order Fucales) have the potential to provide habitat and ameliorate stress for mobile invertebrates. To determine the relative role of 2 rockweeds ( Silvetia compressa and Pelvetiopsis spp.) as foundation species at sites along a latitudinal gradient, we conducted observational surveys and then initiated a 12 mo removal experiment. We found that richness and abundance of mobile invertebrates declined over time when rockweeds were removed, but only at the southernmost site. In contrast, at our other sites, there was no change in the richness and abundance of mobile invertebrates following rockweed removal. At the southern site, rockweeds played an important role in maintaining mobile invertebrate diversity. At our central and northern sites, rockweeds were less important in maintaining the diversity of mobile invertebrates. At these sites, alternative species, including bladed and branching taxa in the genera Mastocarpus , Mazzaella , Corallina , and Endocladia , co-occur with rockweeds and can buffer the system against their loss. However, these alternative foundation species are rare to absent at the southern site, potentially due to greater physical stress. The loss of rockweed foundation species, which are declining at our southern site, can have cascading effects by causing local co-extinctions of associated species. This study highlights the importance of foundation species, especially in areas where their functional redundancy is low, and how the loss of foundation species can alter diversity, leading to potential changes in ecosystem functioning.
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- Award ID(s):
- 1736891
- PAR ID:
- 10310082
- Date Published:
- Journal Name:
- Marine Ecology Progress Series
- Volume:
- 673
- ISSN:
- 0171-8630
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3354/meps13795
