Putting self‐organization to the test: labyrinthine patterns as optimal solution for persistence

Abstract

Spatial patterns formed through the process of self‐organization are found in nature across a variety of ecosystems. Pattern formation may reduce the costs of competition while maximizing the benefits of group living, and thus promote ecosystem persistence. This leads to the prediction that self‐organizing to obtain locally intermediate densities will be the optimal solution to balance costs and benefits. However, despite much evidence documenting pattern formation in natural ecosystems, there is limited empirical evidence of how these patterns both influence and are influenced by tradeoffs between costs and benefits. Using mussels as a model system, we coupled field observations in mussel‐culture plots with manipulative laboratory experiments to address the following hypotheses: 1) labyrinthine spatial patterns, characteristically found at intermediate to high patch densities, are the most persistent over time; this is because labyrinthine patterns 2) result in adequately heavy patches that can maximize resistance to dislodgement while 3) increasing water turbulence with spacing, which will maximize food delivery processes. In the field, we observed that labyrinthine ‘stripes’ patterns are indeed the most persistent over time, confirming our first hypothesis. Furthermore, with laboratory experiments, we found the ‘stripes’ pattern to be highly resistant to dislodgement, confirming the second hypothesis. Finally, with regards to the third hypothesis, we found positive effects of this pattern on local turbulence. These results suggest that the mechanisms of intraspecific facilitation not only depend on initial organism densities, but may also be influenced by spatial patterning. We hence recommend taking into account spatial patterns to maximize productivity and persistence in shellfish‐cultivation practices and to increase the restoration success of ecosystems with self‐organizing properties.

Pattern and structure of microtopography implies autogenic origins in forested wetlands

“…Therefore, while hydrology exerts clear control on the geometry of hummocks, hummocks may exert reciprocal control on hydrology by amplifying small hydrologic fluxes into large water level variations. Last, black ash hummocks provide unique microsite conditions that support increased vegetation growth and diver-sity (Diamond et al, 2019), aligning with observations in other wetland systems (Bledsoe and Shear, 2000;Peach and Zedler, 2006;Økland et al, 2008). Accordingly, recent wetland restoration efforts have begun to use microtopography as a strategy to promote seedling success and long-term project viability (Larkin et al, 2006;Bannister et al, 2013;Lieffers et al, 2017).…”

“…Microtopography, or the small-scale structured variation (10 −1 -10 0 m) in ground surface height, is common to many ecosystems. Wetland microtopography is particularly well studied, and is found in freshwater marshes (van De Koppel and Crain, 2006), fens (Sullivan et al, 2008), peat bogs (Nungesser, 2003), forested swamps (Bledsoe and Shear, 2000), tidal freshwater swamps (Duberstein et al, 2013), and coastal marshes (Stribling et al, 2007). Wetland microtopography is common enough that researchers in disparate systems collectively refer to local high points as "hummocks" and local low points as "hollows".…”

“…In this way, vegetation may reinforce and maintain its own hummock microtopography (and thus preferred environmental conditions). Growing research across different ecosystems suggests that such reinforcing processes, or feedback loops, may be common between biota and their environment, and may result in characteristic, selforganized patch features (Rietkerk and Van de Koppel, 2008;Bertolini et al, 2019). By quantifying the structure and patterning of these features, we may therefore make processbased inferences about latent feedback mechanisms (Turner, 2005;Quintero and Cohen, 2019).…”

Are all patterns created equal? Cooperation is more likely in spatially simple habitats

“…These substrata were chosen to represent a simple hard substratum where movement is maximised but attachment is limited (bare plastic tank) and a complex hard substratum where attachment is possible and often preferred (mixed cockles and mussels shell material, in pieces > 3cm, Capelle, Leuchter, Wit, Hartog, & Bouma, 2019, Bertolini, Geraldi, Montgomery, & Connor, 2017). Fifty mussels of either small (20.52 ± 0.61mm, mean ± SE ) or large (38.75 ± 0.54mm, mean ± SE) size classes were then added and spread evenly in one of the arenas (chosen at random) to obtain a density of 200 mussels/m 2 , representative of a natural lowmedium density (Bertolini et al, 2019), and were left for two hours to form byssal attachment. At the end of each two hours the total number of aggregated mussels was counted.…”

“…The aggregation into patches can be considered as a form of cooperation (Buss, 1981;Doebeli & Hauert, 2005), forming attachment with neighbouring mussels via production of byssal threads (Pearce & Labarbera, 2009). Attachment should protect mussels from dislodgement and predation (Bertness & Grosholz, 1985;Carrington, Moeser, Thompson, Coutts, & Craig, 2008;Hunt & Scheibling, 2001; de Koppel et al, 2008), and mussels ability to reorganise has consequences for system persistence (Bertolini, Cornelissen, Capelle, Van de Koppel, & Bouma, 2019) and habitat boundary formation at whole systems-scale which may ultimately determine species distribution in terms of its realised niche (Donahue, Desharnais, Robles, & Arriola, 2011). However, not all patterns may be created equal, and some patterns might appear similar while hiding differences in their strength.…”