The high diversity found in tropical marine ecosystems and the logistical difficulty and expense of sampling these regions, results in an ecosystem where a great deal remains to be discovered. Therefore, our ecological understanding of these ecosystems and knowledge about the efficacy of conservation efforts remain largely limited to a few taxa or small, well-studied regions. To overcome this problem, biological or environmental surrogates are regularly used but rarely assessed for their efficacy. This thesis explores the efficacy of biological and environmental surrogates for both ecological and conservation purposes.
In this thesis I question whether a broad range of taxonomic groups have similar distributions or respond to the environment in a similar way, and whether our understanding of tropical marine ecosystems may be biased when only few taxonomic groups are used to develop our ecological understanding. I also question whether conservation plans designed using environmental surrogates are effective and provide some guidelines about different approaches that can be used to optimise conservation outcomes. In Chapter 1 I define the different types of surrogates and provide an overview of the theories that support the use of biological and environmental surrogates. I also summarise what has been investigated to date and determine the main gaps in knowledge that require further investigation. These are the issues that are then addressed in the subsequent chapters.
In Chapter 2 I address the question of whether biological surrogates are effective when assessing species assemblage patterns. I show that assemblage patterns are more similar across taxonomic groups when taxa are grouped at a higher taxonomic resolution and at fewer numbers of assemblages, but that excluding rare species made very little difference to the effectiveness of the surrogate. Overall, taxonomic groups displayed very different assemblage patterns and no group was a good surrogate for any other. The other metrics that are widely used to describe patterns and changes in biodiversity are species richness and abundance.
Therefore in Chapter 3 I describe the similarities and differences in the patterns and predictors of species richness and abundance across taxonomic groups. I found that while there were some similarities in the predictors of these patterns, the overall patterns were different and predictor importance varied across taxonomic groups, again cautioning against using subsets of taxa as surrogates to predict and assess general patterns of richness and abundance. Environmental surrogates are another type of surrogate for biodiversity and are often used for conservation purposes. Chapter 4 explores the use of environmental domains as surrogates for biological data when designing marine reserves. I demonstrate that species representation is lower in reserves when environmental domains are used compared to scenarios when domains are biologically informed. This proven need for biological data to be incorporated into conservation planning led to the design of a set of guidelines for the use of different methodological approaches to represent biodiversity in conservation planning for a range of objectives. These guidelines are outlined in Chapter 5. Finally, in Chapter 6 I evaluate the contribution that this thesis has made in evaluating the utility of surrogates for ecology and conservation. I synthesise the findings of this research and then discuss the numerous caveats and potential areas for further investigation.
Overall, my thesis demonstrates that biological and environmental surrogates are not generally effective in highly biodiverse tropical marine inter-reef ecosystems. I show that the collection of biological data from a range of taxonomic groups is essential to representing biodiversity and that the inclusion of only a select group of taxa will significantly bias ecological understanding of these systems. I also demonstrate that the use of environmental surrogates to construct reserves does not produce reserves that are as effective as those informed by at least some biological information. To assist the implementation of my research, I provide guidelines on the best way to incorporate biological data in conservation planning for a range of objectives. This thesis provides clear evidence that to study general ecology in tropical marine ecosystems, a range of taxonomic groups must be incorporated. Furthermore, this thesis provides guidelines necessary to ensure that biodiversity representation is optimised in reserve design and assist in the progression of conservation efforts.