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Running title: Coral identity underpins reef complexity
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Title: Coral identity underpins reef complexity on Caribbean reefs
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Lorenzo Alvarez-Filip1,2,*, Nicholas K. Dulvy2, Isabelle M. Côté2, Andrew R. Watkinson3
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and Jennifer A. Gill1
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Centre for Ecology, Evolution, and Conservation, School of Biological Sciences, University
of East Anglia, Norwich NR4 7TJ, United Kingdom
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Earth to Ocean Research Group, Department of Biological Sciences, Simon Fraser
University, Burnaby BC, V5A 1S6 Canada
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School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, United
Kingdom.
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* Correspondence should be sent to: Lorenzo Alvarez-Filip, Department of Biological
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Sciences, Simon Fraser University. 8888 University Drive, Burnaby, British Columbia, V5A
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1S6, Canada. Email address: [email protected]
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Abstract
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The architectural complexity of ecosystems can greatly influence their capacity to support
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biodiversity and deliver ecosystem services. Understanding the components underlying this
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complexity can aid the development of effective strategies for ecosystem conservation.
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Caribbean coral reefs support and protect millions of livelihoods, but recent anthropogenic
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change is shifting communities towards reefs dominated by stress-resistant coral species,
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which are often less architecturally complex. With the regionwide decline in reef fish
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abundance it is becoming increasingly important to understand changes in coral reef
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community structure and function. We quantify the influence of coral composition, diversity
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and morpho-functional traits on the architectural complexity of reefs across 91 sites at
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Cozumel, Mexico. Although reef architectural complexity increases with coral cover and
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species richness, it is highest on sites that are low in taxonomic evenness and dominated by
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morpho-functionally important reef-building coral genera, particularly Montastraea. Sites
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with similar coral community composition also tend to occur on reefs with very similar
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architectural complexity, suggesting that reef structure tends to be determined by the same
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key species across sites. Our findings provide support for prioritising and protecting
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particular reef types, particularly those dominated by key reef-building corals, in order to
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enhance reef complexity.
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Keywords: biodiversity, dominance, functional groups, habitat complexity, landscape
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ecology
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INTRODUCTION
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The architectural complexity of ecosystems often underpins the biodiversity and
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ecosystem services that they support. Architectural complexity is very often defined or
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provided by foundation taxa (e.g. trees, oysters, stony corals) that have a disproportionate
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influence on ecosystem structure, function and stability (MacArthur 1984, Bruno and
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Bertness 2001, Ellison et al. 2005). However, within these broad groups of foundation taxa,
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different species can contribute disproportionately to architectural complexity. Species
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identity and dominance have been reported as important determinants of ecosystem functions
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and processes (e.g. terrestrial grassland, soil ecosystems; Tilman et al. 1997, McLaren and
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Turkington 2010), however, studies that directly examine the role of the type, rather than the
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number, of species on habitat facilitation are rare. Understanding the influence of different
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species and taxa on ecosystem structure and function is not only of fundamental ecological
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interest but can underpin the development of effective conservation priorities and actions.
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Coral reefs are among the most rapidly changing and valuable ecosystems in the
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world. It is estimated that nearly 70 per cent of the world’s coral reefs are threatened by
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anthropogenic activities (Wilkinson 2008) and are experiencing unprecedented rates of
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degradation (Veron 2008). In the Caribbean, for instance, the architectural complexity of
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reefs has declined substantially over the past forty years with the loss of ~80% of the most
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complex reefs (Alvarez-Filip et al. 2009a). Because of the importance of reef-building corals
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as foundation species within the diverse reef ecosystem, patterns of degradation and
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ecological resilience on coral reefs are typically measured through changes in overall coral
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cover (e.g. Gardner et al. 2003, Bruno and Selig 2007, Mumby et al. 2007). However,
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changes in coral cover often do not capture the changes in reef architectural complexity
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(Alvarez-Filip et al. in press) that can underpin a suite of important ecosystem services such
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as the dissipation of wave energy, nutrient recycling and the abundance, diversity and trophic
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structure of coral reef fishes (Szmant 1997, Lugo-Fernandez et al. 1998, Sheppard et al. 2005,
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Wilson et al. 2007; 2010).
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There is considerable potential for taxon identity and the composition of reef-building
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corals to influence the architectural complexity of reefs, because hard scleractinian corals are
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a taxonomically and morphologically diverse group (Veron and Stafford-Smith 2002, Dullo
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2005). While qualitative differences in the relative contribution of different coral species to
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reef complexity are readily apparent, the contribution of coral identity and community
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composition to architectural complexity has yet to be quantified at the larger reef scales.
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Quantifying the relative contribution of different coral species to the architectural complexity
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of the reefscape is therefore particularly important in order to understand the trajectory of
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coral reefs under changing environmental conditions.
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Disturbances commonly favour a few species that are able to competitively dominate
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the landscape (Tilman & Lehman 2001; Seabloom et al. 2003). Although the Caribbean
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underwent rapid losses of the structurally important Acroporid corals in the late-1970s, many
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reefs remained dominated by healthy populations of the other major-reef building coral
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Montastraea (e.g. McClanahan et al. 1998), suggesting that reef complexity could be
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maintained to some degree in reefs across the region. Since then, the spread of several
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recently emerged diseases, combined with recent bleaching events and other biotic
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disturbances, are now fostering high rates of mortality of Montastraea and other coral species
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previously thought to be more resistant to disturbance (Weil 2004; Bruckner & Bruckner
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2006). Throughout the Caribbean, the loss of these main reef-building coral species
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(Acropora and Montastraea) has been accompanied by an increase in the relative abundance
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(often leading to eventual dominance) of stress-tolerant, early-colonizing corals that form
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smaller and less-architecturally complex colonies such as Porites and Agaricia (Lirman and
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Manzello 2009, Jackson 2001, Aronson et al. 2002, Green et al. 2008). This shift towards
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weedy coral species may constrain reefs into a state of lower potential architectural
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complexity (Steneck et al. 2009), even if overall coral cover remains stable.
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Here we explore the contribution of coral community composition to reef
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architectural complexity across a broad range of sites in Cozumel, Mexico. First, we quantify
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whether sites with similar coral community composition also tend to be similar in terms of
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architectural complexity. Second, we test whether greater coral species diversity is related to
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greater architectural complexity. Finally, we explore how the taxonomic and functional
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attributes of coral dominance influence the relationship between coral cover and architectural
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complexity.
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MATERIALS AND METHODS
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Study area
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Cozumel is a continental island 18 km off the north-eastern coast of the Mexican
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Peninsula of Yucatan. The island is surrounded by coral reefs. The most developed
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formations are in the western shelf, where three terraces can be found between 5 m below sea
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level and the shelf edge (~20 m). Unlike many other Caribbean reefs where reefs originally
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comprised Acroporid species, in Cozumel the reefs close to the shore have been built mainly
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by Montastraea (Muckelbauer 1990). The south-western coast of Cozumel has been under
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official protection since 1980 (figure 1, Alvarez-Filip et al. 2009b) and, while visitation and
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tourist activities are permitted, fishing is banned on the western coast of the marine reserve.
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Field surveys
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In total, 91 sites along the south-west coast of Cozumel, all separated by at least 200
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m (figure 1), were surveyed between October 2007 and February 2008. At each site, one 30
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m transect was haphazardly located on the top of the reef crest (between 10 and 15 m depth)
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and parallel to the coast. Reef attributes such as coral cover or reef architecture were not used
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to determine the position of transects. To evaluate coral abundance, we used the point
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intercept method to record the occurrence of corals every 25 cm along each transect (120
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counts per transect). This method is widely used in the Caribbean and elsewhere to describe
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reef benthic composition, and it has been shown to provide comparable information to
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measuring benthic composition along the entire length of transects (Hill and Wilkinson
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2004). All corals were identified in the field at species level according to Veron and Stafford-
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Smith 2002.
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Reef architectural complexity was quantified using the rugosity index (Risk 1972),
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which was obtained by fitting a fine, three metre chain (0.7 cm link-length) to the reef. While
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laying the chain, care was taken to follow the detailed contour of corals and other reef
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attributes (rock crevices, sponges) by lining up individual branches and fitting the chain
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between coral ramets. To calculate the index, the contoured distance is divided by the linear
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distance between its start and end point. A perfectly flat surface has a rugosity index of one,
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with larger numbers indicating more complex surfaces. Rugosity measures were taken in five
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equally spaced points along the same 30 m transect, which were then averaged to give
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transect-level rugosity.
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Data Analyses
To examine whether transects with similar coral community composition also tended
to have similar architectural complexity, we constructed matrices of site community
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composition and site rugosity for all pairs of sites. The similarity matrix for coral community
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composition was constructed using all coral species and their relative cover in each site, and
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computed using the Bray-Curtis similarity coefficient. The architectural complexity matrix
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was constructed by calculating the relative percentage similarity in rugosity between each
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pair of sites using the following formula:
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% similarity = (│Ri - Rj│/ MD) x 100
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where │Ri - Rj│is the absolute difference between the values of rugosity in sitei and sitej for
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each pair of sites, and MD is the maximum observed difference between all the pairwise
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comparisons. We evaluated whether architectural complexity among sites is a function of
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coral community composition among sites using a Mantel test (Mantel 1967). This test
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measures the correlation between two matrices and assesses the significance of the
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correlation by randomizing one of the matrices and calculating a null distribution of values
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from the randomly generated associations. In this study, the Mantel test was calculated using
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the package Vegan in R (R 2009), with 10,000 random matrix permutations used to assess
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significance levels.
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To test whether greater coral species diversity is related to greater architectural
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complexity, we quantified coral diversity using three univariate dimensions of diversity: coral
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species richness (number of species recorded at each site), evenness in species abundance
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(the Pielou index of percentage areal cover of each species) and taxonomic diversity. For the
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last dimension, we calculated the average taxonomic distinctness (Δ+) and the variation in
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taxonomic distinctness (Λ+) using a widely-used and accepted coral taxonomy (Veron and
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Stafford-Smith 2002). Average taxonomic distinctness measures average evolutionary
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relatedness as the mean path (or branch) length of the local community and the variation in
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taxonomic distinctness is the variance in path (or branch) lengths of the local community
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(Clarke and Warwick 2001). We also calculated richness and evenness of the morpho-
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functional groups. We then used linear regressions to explore the strength and nature of the
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associations between each of these measures of coral diversity and reef architectural
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complexity.
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To explore the influence of species identity and morpho-functional attributes on reef
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structure, we grouped coral species by genus and by morphology. Morpho-functional groups
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were constructed from the maximum size and colony shape of each coral species (table 1).
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Following Reyes-Bonilla (2004), three shape categories (massive or nodular; branching,
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ramose or phaceloid; platy, foliaceous or encrusting) and three size categories (small (<10
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cm); medium (10 to 30 cm); large (>30 cm)) were used. Combining shape and size categories
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resulted in seven different morpho-functional groups (table 1).
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To explore how the taxonomic and functional attributes of coral dominance influence
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the relationship between coral cover and architectural complexity, we compare the slopes of
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these relationships among (a) the three most abundant genera (Agaricia, Porites and
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Montastraea) and (b) the three most abundant morpho-functional groups (figure 2b). The 91
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transects were categorised depending on the single most dominant (highest relative
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abundance on the site) genus and morpho-functional group. Differences between each pair of
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linear models were explored by dividing the difference between both regression coefficients
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by the square root of the sum of the squared standard errors. Assuming normally distributed
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residuals, this estimate follows a t-distribution with n-2 degrees of freedom (Zar 1999).
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RESULTS
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A total of 33 species of reef-building corals were recorded in Cozumel during this study
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(table 1). The dominant genera included Agaricia, Montastraea and Porites (primarily P.
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astreoides), and hence corals with large, massive and foliaceous colonies were the most
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abundant morpho-functional groups (figure 2a,b). Both coral cover and reef architectural
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complexity vary greatly across the study area, from flat sites with low coral cover to highly
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complex areas of reef. Average coral cover for the 91 sites was 16% (± 1.32 SE, range: 0 -
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52%) while rugosity averaged 1.49 (± 0.04 SE, range: 1.02 - 2.77).
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Pairs of sites with similar coral community composition tend to also have similar
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levels of architectural complexity (Mantel test, rm = 0.18; p < 0.001).Very high similarity in
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coral community composition (> 70% similarity) only occurred in reefs with similar
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architectural complexity (> 50% similarity in rugosity), regardless of whether the sites were
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similarly complex or similarly flat (figure 3).
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Architectural complexity is positively associated with the number of coral species;
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sites with fewer than five coral species tend to be relatively flat while more diverse sites, with
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between 8 and 13 species, had the greatest complexity (figure 4a). However, the evenness in
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coral cover among coral species declined with increasing coral species richness (r = -0.40; P
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< 0.001), and consequently sites with greater architectural complexity tended to be species-
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rich but dominated by one or few coral species (figure 4b). The flat reefs primarily comprise
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bare rock and/or algae rather than monotypic patches of relatively flat corals (e.g. Millepora
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or Siderastrea), as indicated by the lack of any sites with high coral cover and low rugosity
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(figure 4a). The relationship between taxonomic distinctness among coral species and
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architectural complexity is highly non-linear (R2 = 0.01; P = 0.22), with a small number of
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flat reefs tending to be either particularly distinct or particularly related (figure 3c). The
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variation in taxonomic distinctness was not significantly related to architectural complexity
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(figure 4d). From the morphological and functional perspective, greatest complexity is found
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on reefs with higher morpho-functional diversity (figure 4e), but dominated by relatively few
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morpho-functional types (figure 4f).
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Reefs with greater coral cover tend to have greater architectural complexity but the
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variance in architectural complexity also increases with coral cover (figure 5a). Much of
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variance in architectural complexity at high levels of coral cover is the result of dominance
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by a particular coral genus. Sites dominated by species from the genus Montastraea have
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greater architectural complexity for a given coral cover, followed by Agaricia then Porites
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(figure 5b). On Montastraea-dominated sites, architectural complexity increased more
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rapidly with increasing coral cover than on Porites-dominated sites (T24 = -2.23; P = 0.03).
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However, the slopes of relationships between coral cover and architectural complexity for
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Agaricia and each of the other two genera did not differ significantly (Agaricia vs
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Montastraea: T49 = 1.65, P= 0.10; Agaricia vs Porites: T47 = -1.23, P = 0.22).
The differences in architectural complexity for given levels of coral cover are also
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strongly related to the morpho-functional attributes of the dominant species. Sites dominated
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by massive and large coral species have greater architectural complexity for a given coral
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cover, followed by sites dominated by large platy, foliaceous or encrusting (PL) and then
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medium size massive corals (figure 5c). Architectural complexity on sites dominated by
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massive and large coral species also increased significantly more rapidly with increasing
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coral cover than on reefs dominated by medium size massive corals (T34 = -2.72, P = 0.01).
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However, the slope of the relationship between architectural complexity and coral cover on
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large platy, foliaceous or encrusting -dominated reefs did not differ significantly from the
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other two morphological groups (PL vs ML: T54 = 1.56, P = 0.13; PL vs MM: T30 = -0.81; P =
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0.43).
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DISCUSSION
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Our findings suggest that the type and dominance of foundation species can be just as
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important as their overall abundance in providing architectural complexity to their
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ecosystems. Reef complexity increases with increasing coral cover, but the rate of increase in
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complexity depends on coral community composition and, in particular, the identity of the
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dominant species and their associated morphological and functional traits. The most
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architecturally complex sites are dominated by few coral species (and morpho-functional
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groups) and the identity of these corals largely explains the differences in the architecture of
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these sites. These findings underscore the importance of considering coral species
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composition and shifts in coral dominance on Caribbean reefs in order to understand the
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implications of changes in these ecosystems on the associated biodiversity and ecosystem
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services.
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Generally, species diversity is considered a fundamental feature of ecosystem
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structure and function (Loreau et al. 2001, Hooper et al. 2005) and, in coral reefs, greater
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species diversity might be expected to increase reef complexity simply because of the large
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variety of coral forms and shapes (e.g. Chabanet et al. 1997, Bruno and Bertness 2001).
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However, positive relationships between the number of coral species and architectural
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complexity may in fact be a consequence of the positive relationship between coral cover and
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architectural complexity, as species diversity can also be positively associated with the extent
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of coral cover (this study: r = 0.83, P < 0.001; Bell and Galzin 1984). Moreover, taxonomic
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relatedness indices show that most sites shared a very similar species composition and that
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there is no clear effect of increasing taxonomic composition on reef architectural complexity.
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By contrast, the distribution of species relative abundances (percent cover) clearly shows that
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predominance by one or few species increases the complexity of the reef structure.
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Historically, Caribbean reefs have comprised small numbers of abundant species rather than a
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high diversity of coral species (Johnson et al. 2008), supporting the importance of coral
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dominance in structuring Caribbean reefs. In addition, Caribbean corals have relatively low
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diversity and redundancy in comparison with other regions of the world. For example, there
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are 120 massive coral species in the Great Barrier Reef, Australia while the Caribbean
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harbours fewer than 25 (Bellwood et al. 2004). This lack of functional diversity might explain
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why Caribbean reef architectural complexity relies more on the presence and identity of
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dominant species than on the combined structural attributes of a wider range of species.
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We found that the strength of the positive effect of foundation species in providing
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structure to the habitat largely depends on the identity of the dominant taxa. At the reefscape
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scale, architectural complexity increased faster in sites dominated by large-massive species,
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such as Montastraea, than in sites dominated by short-lived and stress-resistant species.
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Branching corals are a relatively uncommon in Cozumel, for example, branching species of
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the genus Porites (P. porites) occur at much lower relative abundance than the sister massive
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species (P. astreoides; table 1), and the main differences in reef complexity found in this
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study are therefore primarily a consequence of the large and massive nature of Montastraea
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corals. Among Caribbean reef-building corals, Montastraea species play critical roles in reef
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construction and community ecology (Harborne et al. 2008, Harborne 2009). The relative
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abundance of such massive species is declining in the Caribbean (Edmunds and Elahi 2007).
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For example, Cozumel reefs were largely dominated by Montastraea species in the 1980s
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(Muckelbauer 1990) but more recently they have been increasingly dominated by Agaricia
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and Porites (Alvarez-Filip et al. 2009b; figure 2). Cozumel reefs may therefore no longer be
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providing the structural benefits that they were in recent decades. Similar shifts from
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assemblages dominated by physically large and long-lived coral species toward assemblages
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dominated by weedy corals are being recorded throughout the Caribbean (Lirman and
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Manzello 2009, Jackson 2001, Aronson et al. 2002, Green et al. 2008, Steneck et al. 2009),
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highlighting the large-scale consequences that these changes in coral community composition
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may have for the architectural complexity of Caribbean reefs.
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On sites with relatively low coral cover (≤ 20 %), architectural complexity varies
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little, even across sites dominated by different coral species and types (figures 5 b,c),
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probably because dominant species are not abundant enough (high evenness; figure 5a) to
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contribute significantly to the reef framework. Assuming that this also applies elsewhere in
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the Caribbean, our findings may help to explain the rapid structural homogenization towards
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relatively flat reefs reported in recent decades (Alvarez-Filip et al. 2009a). Most Caribbean
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reefs have been near or below 20% coral cover since the early 2000s (Gardner et al. 2003,
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Bruno et al. 2009, Schutte et al. 2010), which may suggest that the abundance of previously
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dominant corals in most reefs is now too low to contribute significantly to reef architectural
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complexity. It is likely that the high frequency of disturbances or chronic mortality that
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Caribbean reefs are facing may prevent some structurally-important species from dominating
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(Hughes and Connell 1999), and these reefs are therefore likely to remain in the current low-
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complexity and high evenness state.
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More complex reefs tend to have greater numbers of individuals, biomass or richness
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of reef-associated fishes and invertebrates (Dulvy et al. 2002, Idjadi and Edmunds 2006,
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Wilson et al. 2007). Consequently, our findings suggest that assemblages with dominant reef-
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building species such as Montastraea spp. would be expected to facilitate more biodiverse
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and functionally-important coral reefs in the Caribbean. Montastraea historically ranked high
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in importance along with Acropora palmata and A. cervicornis in their overall contribution to
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Western Atlantic reef structure. Acroporids have now almost vanished from Caribbean reefs
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and the unique structural role (i.e. large-branching colonies) of these corals is likely no longer
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filled by any other species (Bruckner 2003; Aronson & Precht 2006). In the Caribbean
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therefore it is likely that halting rates of architectural complexity loss will require a major
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emphasis on facilitating the maintenance and endurance of healthy populations of
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Montastraea corals, and promoting the recovery of Acroporids, rather than just focussing
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efforts on restoring the overall abundance of scleractinian corals. This seems to be
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particularly important for those reefs that have relatively high coral cover (> 20%), where the
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presence of healthy populations of these key coral species may considerably increase the reef
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architectural complexity. Important regional differences in the species richness and functional
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composition of reef systems (Bellwood et al. 2004) also highlight the need to explore the
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generality of these findings. Assessing whether similar patterns occur in regions with
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considerably higher diversity of coral forms and functional redundancy, such as in the Indo-
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West Pacific, would enrich our understanding of the role of coral species composition in the
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provision of ecological and ecosystem services.
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Acknowledgements
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This study was carried out with the permission and support of the Parque Nacional Arrecifes
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de Cozumel and the Comisión Nacional de Áreas Naturales Protegidas of México. We thank
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M. Millet-Encalada, R. Hernandez-Landa, A. Brito-Bermudez, and the staff of the PNAC for
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their invaluable help during the surveys. This research was founded by the Mexican
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scholarships from the CONACYT (171864) and SEP to L.A-F. NKD and IMC are supported
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by Discovery grants from the Natural Sciences and Engineering Research Council, Canada
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and JAG is supported by Natural Environment Research Council, UK. Our manuscript was
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significantly improved by insightful comments of two anonymous referees.
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Table 1. Mean cover (± standard error) and morphological information of the coral species
498
recorded in the 91 sites surveyed.
Average
percentage
Colony
Colony
Morphology
shapea
sizeb
groupc
Genus
Species
cover (± SE)
Acropora
A. cervicornis
0.03 (0.03)
B
L
BL
A. palmata
0.16 (0.1)
B
L
BL
M. decactis
0.16 (0.04)
M
M
MM
M. formosa
0.02 (0.01)
B
M
BM
Stephanocoenia
S. intersepta
0.24 (0.05)
M
M
MM
Eusmilia
E. fastigiata
0.39 (0.07)
B
M
BM
Colpophyllia
C. natans
0.06 (0.04)
M
L
ML
Diploria
D. clivosa
0.03 (0.02)
M
L
ML
D. labyrinthiformis 0.05 (0.02)
M
M
MM
D. strigosa
0.07 (0.04)
M
M
MM
M. annularis
1.43 (0.39)
M
L
ML
M. cavernosa
0.97 (0.12)
M
L
ML
M. faveolata
1.68 (0.26)
M
L
ML
M. franksi
0.09 (0.03)
M
M
MM
Favia
F. fragum
0.02 (0.01)
M
S
MS
Dendrogyra
D. cylindrus
0.01 (0.01)
M
L
ML
Dichocoenia
D. stokesii
0.04 (0.02)
M
M
MM
Meandrina
M. meandrites
0.13 (0.04)
M
M
MM
Isophyllastrea
I. rigida
0.02 (0.01)
M
M
MM
Mycetophyllia
M. lamarckiana
0.15 (0.04)
P
M
PM
Madracis
Montastraea
21
Agaricia
Siderastrea
Porites
Millepora
A. agaricites
4.56 (0.41)
P
L
PL
A. humilis
0.03 (0.02)
M
L
ML
A. lamarcki
0.02 (0.01)
P
L
PL
A. tenuifolia
0.43 (0.13)
P
L
PL
S. radians
0.02 (0.01)
M
S
MS
S. siderea
1.45 (0.16)
M
L
ML
P. astreoides
2.45 (0.3)
M
M
MM
P. colonensis
0.03 (0.02)
P
M
PM
P. divaricata
0.02 (0.01)
B
L
BL
P. furcata
0.10 (0.04)
B
L
BL
P. porites
0.82 (0.13)
B
L
BL
M. alcicornis
0.27 (0.06)
B
M
BM
M. complanta
0.06 (0.02)
P
L
PL
499
500
501
502
503
a
M = massive or nodular; B = branching, ramose or phaceloid; P = platy, foliaceous or
encrusting.
b
S = small (<10 cm); M = medium (10 to 30 cm); L = large (>30cm).
c
Morphological group is the combination of shape and size.
22
504
Figure legends
505
506
Figure 1. Map of Cozumel Island and (inset) the location within the Caribbean Sea. The
507
continuous line delimits the polygon of the Marine Protected Area (Parque Nacional
508
Arrecifes de Cozumel) and the bold dotted line represents the area surveyed in this study.
509
510
511
Figure 2. Mean percent cover (± standard error) of hard corals on Cozumel reefs, grouped by
512
(a) genus and (b) morphology (see table 1 for definitions of morpho-functional groups). For
513
(b) the total number of species included in each morpho-functional group is given in
514
parentheses.
515
516
Figure 3. Similarities in coral community composition (Bray-Curtis similarity coefficient)
517
and reef architecture (% similarity in rugosity indices) for 4095 different pairs of sites from
518
91 sites in Cozumel. Circle colour indicates pairs of sites which both have rugosity values >
519
1.5 (black), both < 1.5 (grey) or one from each category (white).
520
521
522
Figure 4. The relationships between reef architectural complexity on 91 sites in Cozumel and
523
(A) total number of coral species (y = 1.06 + 0.08x; R2 = 0.34; P < 0.001); (B) Pielou index
524
of coral species evenness (y = 3.99 - 2.79 x; R2 = 0.30; P < 0.001); (C) average taxonomic
525
distinctness of coral species; (D) variation in taxonomic distinctness of coral species; (E) total
526
number of coral morpho-functional groups (y = 0.79 + 0.19x; R2 = 0.33; p < 0.001); and (F)
527
Pielou index of morpho-functional groups evenness (y = 4.08 – 2.90x; R2 = 0.32; p < 0.001).
528
23
529
Figure 5. The relationship between coral cover and architectural complexity indices across 91
530
sites in Cozumel (R2 = 0.61; slope = 0.024; P < 0.001) for (A) sites dominated by
531
Montastraea (black), Agaricia (dark grey), Porites (pale grey) or no dominant species
532
(white), and the linear regression and 95% confidence intervals for sites dominated by the
533
three most common (B) coral genera: Montastraea (y = 1.02 + 0.04x; R2 = 0.61; P < 0.001);
534
Agaricia (y = 1.12 + 0.02x; R2 = 0.55; P < 0.001) and Porites (y = 1.05 + 0.02x; R2 = 0.84; P
535
< 0.001) and (C) morphological groups: ML (y = 1.05 + 0.03x; R2 = 0.62; P < 0.001); PL (y =
536
1.16 + 0.02x; R2 = 0.50; P < 0.001) and MM (y = 1.02 + 0.02x; R2 = 0.93; P < 0.001). See
537
table 1 for details of morphological groups. In (A) increasing point size represents increasing
538
evenness (Pielou index) of coral community composition.
539
540
24
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Figure 1
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543
544
545
546
547
25
548
Figure 2
549
550
551
552
553
26
554
Figure 3
555
556
557
558
559
560
27
561
Figure 4
562
563
564
28
565
Figure 5
566
567
29