An Evaluation of Prior Residency and Habitat Effects on the Persistence of Settling Reef Fishes

<p>Both habitat complexity and competitive interactions can shape patterns of distribution and abundance of species. I evaluated the separate and joint effects of competitive interactions and habitat complexity on the survival of young fishes (Family Labridae) on coral reefs. First, I developed (in Chapter 2) a quantitative approach to evaluate potential resource (i.e., niche) overlap among groups of co-occurring species. Using appropriate transformations and probability models, I show that different types of data (e.g., categorical, continuous, count or binary data, as well as electivity scores) give rise to a standard measure of niche overlap, with the overlap statistic between two species defined as the overlapping area between the distributions for each species. Measurements derived from different types of data can be combined into a single multivariate analysis of niche overlap by averaging over multiple axes. I then describe null model permutation tests that differentiate between species occupying similar and different niches within my unified indices. I then implemented this approach (in Chapter 3) to evaluate potential habitat overlap among eight species of wrasse (Gomphosus varius, Halichoeres hortulanus, H. trimaculatus, Pseudocheilinus hexataenia, Scarus sordidus, Stethojulis bandanensis, Thalassoma hardwicke and T. quinquevittatum), and used these results to inform my subsequent field experiments. In a field assay, I identified the presence of T. quinquevittatum as having the greatest negative effect on survival of transplanted T. hardwicke from a suite of three candidate species which were most similar in habitat use to T. hardwicke (the other two candidate species were G. varius and P. hexataenia). In a subsequent field experiment, I tested how competition with T. quinquevittatum and structural refuge interact to influence the postsettlement survival of T. hardwicke. Competition with T. quinquevittatum and structural refuge both altered the survival of T. hardwicke, although their effects were not interactive, indicating that structural complexity did not mitigate the negative effects of competition. Survival of T. hardwicke was 2.3 times greater in treatments without T. quinquevittatum relative to those with T. quinquevittatum, and 2.8 times greater in treatments with structural refuge relative to treatments without structural refuge. Thalassoma hardwicke and T. quinquevittatum often enter reef communities asynchronously, resulting in competitive pressures faced by earlyarriving individuals that potentially differ from those experienced by late-arriving individuals. In a series of field experiments, I investigated whether the strength of intra-cohort competitive interactions between recent T. hardwicke and T. quinquevittatum settlers were dependent upon the sequence and temporal separation of their arrival into communities. Survival rates for both species were greatest in the absence of competitors, but when competitors were present, survival rates were maximized when competitors arrived simultaneously. Survival rates declined as each species entered the community progressively later than its competitor. Further, reversals in the sequence of arrival reversed competitive outcomes. Results provide empirical evidence for competitive lotteries in the maintenance of species diversity in demographically open marine systems, while also highlighting the importance of temporal variation in the direction and magnitude of interaction strengths. To further our understanding of how timing of arrival influences interaction strengths, I tested whether increasing the availability of complex habitat attenuates or enhances timing-of-arrival effects. Results from this field experiment indicated that aggression by early-arriving individuals towards late-arriving individuals increased as arrival times diverged. When aggression was weak, subordinate individuals were not displaced from complex habitat. Experimental increases in the availability of complex habitat resulted in increased survival of subordinates, presumably by disrupting predation pressure. However, when aggression was intense, competitive subordinates were displaced from complex habitat (regardless of the amount of complex habitat available), and this likely increased their exposure to predators. Overall, the experimental and observational components of this thesis emphasise heterogeneity in competitive environments experienced by recently settled reef fishes. These results highlight the important role that priority effects and habitat complexity play in determining the persistence of reef fish settlers, and illustrate how ecological contexts can add considerable variation to realised interaction strengths.</p>

An Evaluation of Prior Residency and Habitat Effects on the Persistence of Settling Reef Fishes

<p>Both habitat complexity and competitive interactions can shape patterns of distribution and abundance of species. I evaluated the separate and joint effects of competitive interactions and habitat complexity on the survival of young fishes (Family Labridae) on coral reefs. First, I developed (in Chapter 2) a quantitative approach to evaluate potential resource (i.e., niche) overlap among groups of co-occurring species. Using appropriate transformations and probability models, I show that different types of data (e.g., categorical, continuous, count or binary data, as well as electivity scores) give rise to a standard measure of niche overlap, with the overlap statistic between two species defined as the overlapping area between the distributions for each species. Measurements derived from different types of data can be combined into a single multivariate analysis of niche overlap by averaging over multiple axes. I then describe null model permutation tests that differentiate between species occupying similar and different niches within my unified indices. I then implemented this approach (in Chapter 3) to evaluate potential habitat overlap among eight species of wrasse (Gomphosus varius, Halichoeres hortulanus, H. trimaculatus, Pseudocheilinus hexataenia, Scarus sordidus, Stethojulis bandanensis, Thalassoma hardwicke and T. quinquevittatum), and used these results to inform my subsequent field experiments. In a field assay, I identified the presence of T. quinquevittatum as having the greatest negative effect on survival of transplanted T. hardwicke from a suite of three candidate species which were most similar in habitat use to T. hardwicke (the other two candidate species were G. varius and P. hexataenia). In a subsequent field experiment, I tested how competition with T. quinquevittatum and structural refuge interact to influence the postsettlement survival of T. hardwicke. Competition with T. quinquevittatum and structural refuge both altered the survival of T. hardwicke, although their effects were not interactive, indicating that structural complexity did not mitigate the negative effects of competition. Survival of T. hardwicke was 2.3 times greater in treatments without T. quinquevittatum relative to those with T. quinquevittatum, and 2.8 times greater in treatments with structural refuge relative to treatments without structural refuge. Thalassoma hardwicke and T. quinquevittatum often enter reef communities asynchronously, resulting in competitive pressures faced by earlyarriving individuals that potentially differ from those experienced by late-arriving individuals. In a series of field experiments, I investigated whether the strength of intra-cohort competitive interactions between recent T. hardwicke and T. quinquevittatum settlers were dependent upon the sequence and temporal separation of their arrival into communities. Survival rates for both species were greatest in the absence of competitors, but when competitors were present, survival rates were maximized when competitors arrived simultaneously. Survival rates declined as each species entered the community progressively later than its competitor. Further, reversals in the sequence of arrival reversed competitive outcomes. Results provide empirical evidence for competitive lotteries in the maintenance of species diversity in demographically open marine systems, while also highlighting the importance of temporal variation in the direction and magnitude of interaction strengths. To further our understanding of how timing of arrival influences interaction strengths, I tested whether increasing the availability of complex habitat attenuates or enhances timing-of-arrival effects. Results from this field experiment indicated that aggression by early-arriving individuals towards late-arriving individuals increased as arrival times diverged. When aggression was weak, subordinate individuals were not displaced from complex habitat. Experimental increases in the availability of complex habitat resulted in increased survival of subordinates, presumably by disrupting predation pressure. However, when aggression was intense, competitive subordinates were displaced from complex habitat (regardless of the amount of complex habitat available), and this likely increased their exposure to predators. Overall, the experimental and observational components of this thesis emphasise heterogeneity in competitive environments experienced by recently settled reef fishes. These results highlight the important role that priority effects and habitat complexity play in determining the persistence of reef fish settlers, and illustrate how ecological contexts can add considerable variation to realised interaction strengths.</p>

Orangutan information broadcast via consonant-like and vowel-like calls breaches mathematical models of linguistic evolution

The origin of language is one of the most significant evolutionary milestones of life on Earth, but one of the most persevering scientific unknowns. Two decades ago, game theorists and mathematicians predicted that the first words and grammar emerged as a response to transmission errors and information loss in language's precursor system, however, empirical proof is lacking. Here, we assessed information loss in proto-consonants and proto-vowels in human pre-linguistic ancestors as proxied by orangutan consonant-like and vowel-like calls that compose syllable-like combinations. We played back and re-recorded calls at increasing distances across a structurally complex habitat (i.e. adverse to sound transmission). Consonant-like and vowel-like calls degraded acoustically over distance, but no information loss was detected regarding three distinct classes of information ( viz. individual ID, context and population ID). Our results refute prevailing mathematical predictions and herald a turning point in language evolution theory and heuristics. Namely, explaining how the vocal–verbal continuum was crossed in the hominid family will benefit from future mathematical and computational models that, in order to enjoy empirical validity and superior explanatory power, will be informed by great ape behaviour and repertoire.

Eunotia Ehrenberg (Eunotiaceae, Bacillariophyta) in a subtropical floodplain: a new species and taxonomic contributions

The Upper Paraná River floodplain is one of the few remaining non-dammed stretches in Brazil. It has a typical fluvial dynamics represented by the flood pulse and a highly complex habitat, which allows the existence and maintenance of a great biodiversity, including diatom species. As it happens in tropical lowland environments, also in this floodplain, the genus Eunotia is one of the most diverse and abundant diatom groups. Therefore, this study addresses morphologic and morphometric details of a new species and the most abundant Eunotia species in sediment cores from two wetland lakes. The morphological characteristics from each species were obtained through microscopy documentation of cell walls, and compared with other related species.

Population estimate of wild rainbow trout in a remote stream of southern California

Recreational fishing for Rainbow Trout (Oncorhynchus mykiss) is important economically in California. We determined the upstream and downstream distribution of Rainbow Trout in a southern California stream, and classified all available habitat within that area as riffle, pool, cascade-pool-complex, and flatwater. Approximately 10% (based on length) of each habitat type was sampled using depletion electrofishing. We estimated Rainbow Trout abundance, both <100 mm and ≥100 mm, by extrapolating average number of fish per m² in each habitat type sampled to the total m² of each habitat type. A total of 854 fish were captured, with the greatest proportion coming from the cascade-pool-complex habitat type, followed by pool, flatwater, and riffle. The population estimate for Rainbow Trout <100 mm was 1,763 fish (95% CI ±442), and for Rainbow Trout ≥100 mm was 5,383 fish (95% CI ±1,688).

Modelling mutual interactions between soil structure and soil biological communities.

&lt;p&gt;Habitat structure is a key factor controlling the structure of ecological communities. For example, complex habitat structure may increase species number, minimise competition and facilitate the retention of nutrients. Alteration and disturbance of habitat structure may thus negatively affect biodiversity. Soil is an extremely complex and highly structured environmental matrix. Soil structure, defined as a distribution of aggregate/pore space of different sizes, can thus be a major control of soil biological communities, which are for example highly structured in their size distribution. Soil organisms, however, also affect and modify soil structure, and for many organisms the soil habitat structure is thus not just a condition to which they have to adapt but, rather, an environmental feature they also affect. In this talk, I discuss all these aspects from a community ecology point of view and with an emphasis on statistical and dynamical models that soil ecologists are trying to develop to describe and predict the mutual interactions between soil structure and biological communities. I will focus on the different rates at which soil structure affects soil organisms and vice versa, to emphasise that the temporal scales at which we have to measure the two parts of this mutual feedback (i.e. soil structure -&gt; biota vs. biota -&gt; soil structure) are very different, and also variable in space and time.&amp;#160;&lt;/p&gt;

Checklist of Benthic Cnidaria in the SW Atlantic Ocean (54ºS–56ºS)

In this study we provide an updated checklist of benthic Cnidaria from SW Atlantic Ocean that comprised the Marine Protected Areas Namuncurá I and II, located at Burdwood bank, and other neighbouring locations. A total of 88 taxa was recorded: 36 hydrozoans and 52 anthozoans from which 32 were octocorals, 10 scleractinian corals, 8 sea anemones and 2 zoanthids. Burdwood bank presented the highest richness considering that 87% of the recorded species inhabit this plateau or its slope. Besides some common species widely distributed in the studied sub-areas, at least 24 species represent new distributional records while few were exclusively recorded at Burdwood bank. The inventory here provided will help to identify key habitat-forming species in a complex habitat where marine animal forests and vulnerable marine ecosystems were previously detected. It will be also a very valuable tool for the management and monitoring of the sub-areas under protection.