Disentangling the links between habitat complexity and biodiversity in a kelp‐dominated subantarctic community

Abstract

Habitat complexity is one of the most important factors modulating species diversity. This feature comprises several interrelated attributes, such as number, size, and spatial arrangement of complexity‐forming elements. However, the separate and joint effects of these attributes on diversity and community structure are still not well understood. Here, we assess the relationships between several structural‐complexity attributes of the subantarctic kelp Lessonia flavicans and species richness, total abundance, and structure of kelp‐associated macrobenthic communities. We predicted that longer thalli and larger holdfasts favor greater species richness and total abundance of invertebrate organisms. To test the prediction, an observational sampling program was established in two sites of the Strait of Magellan. Uni‐ and multivariate analyses revealed both positive and negative effects of kelp structural‐complexity attributes on diversity. Holdfast diameter and maximum frond length, followed by thallus wet weight, had the strongest positive fits to species richness and total abundance; the number of stipes, on the other hand, was negatively associated with both response variables. Longer fronds were associated with greater abundances of spirorbid polychaetes. Larger holdfasts supported larger abundances of Nereididae and Terebelidae polychaetes and the limpet Nacella mytilina. Contrarily, kelps with longer fronds and more stipes supported fewer amphipods. In this way, we demonstrate that different dimensions of habitat complexity can have contrasting effects on diversity and community structure, highlighting the fundamental role of multiple dimensions of kelp habitat complexity for local biodiversity.

Macroalgal features and their influence on associated biodiversity: implications for conservation and restoration

“…Consistent with this, seaweed's fractal dimensions have been also shown to have an influence on invertebrate abundance and taxon richness (Mancuso et al, 2023a) regardless of host identity (Veiga et al, 2014). However, some studies have also found mixed results, with strong positive correlations between community structure and algal complexity features such as holdfast diameter and frond length, and negative correlations with features such as the number of stipes (Velasco-Charpentier et al, 2021).…”

“…While those increases range widely from weak to very strong, and the influence of non-native seaweeds or other factors add an additional level of complexity (e.g., Veiga et al, 2016;Lutz et al, 2019;Ndhlovu et al, 2021;Lenzo et al, 2023), seaweeds generally improve rather than hinder associated communities. The most consistent promoter of faunal diversity seems to be the complexity of identifiable features within a seaweed itself (e.g., branching or holdfast morphology; Hacker and Steneck, 1990;Hauser et al, 2006;Lutz et al, 2019: Velasco-Charpentier et al, 2021 or the complexity achieved by the presence of several individuals or species coming together into a discernable habitat (Best et al, 2014;Tano et al, 2016). Algal structural complexitybiodiversity relationships have also been examined using fractal dimensions, and the outcome of several key studies have provided added support to these relationships (e.g., Mancuso et al, 2023b).…”

“…This overview made also evident a potential geographic gap: most of the studies examined were conducted in warm, low-mid latitudes, such as southern U.S.A., the Mediterranean coasts or Australia (Hacker and Steneck, 1990;Russo, 1990;Taylor and Cole, 1994;Lutz et al, 2019;Shelamoff et al, 2020), although a representative number of studies from high (including polar) latitudes have been also considered (e.g., Lippert et al, 2001;Nuñez-Pons et al, 2012;Velasco-Charpentier et al, 2021). Often, the diverse complement of seaweeds found in low-mid latitude regions support rich associated communities, making the influence of features such as physical complexity potentially more evident.…”

Peruvian nudibranchs (Mollusca, Gastropoda, Heterobranchia): an updated literature review-based list of species

“…Abundant in the Magellanic Province, in the Southeast Pacific ( Aldea et al 2011 ; Velasco‐Charpentier et al 2021 ) and with records in the South Atlantic ( Eliot 1907 ; Odhner 1926 , 1944 ), Pacific Ocean ( Marcus 1959 ; Meyers-Muñoz et al 2009 ; Schrödl 1996a , 2003 ), and Indian Ocean ( Odhner 1944 ).…”