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

2021 ◽  
Author(s):  
◽  
Shane Wallace Geange
Keyword(s):  
Habitat Complexity ◽  
Field Experiments ◽  
Survival Rates ◽  
Niche Overlap ◽  
Reef Fishes ◽  
Competitive Interactions ◽  
Candidate Species ◽  
Thalassoma Hardwicke ◽  
Complex Habitat ◽  
Timing Of Arrival

<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>

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

2021 ◽  
Author(s):  
◽  
Shane Wallace Geange
Keyword(s):  
Habitat Complexity ◽  
Field Experiments ◽  
Survival Rates ◽  
Niche Overlap ◽  
Reef Fishes ◽  
Competitive Interactions ◽  
Candidate Species ◽  
Thalassoma Hardwicke ◽  
Complex Habitat ◽  
Timing Of Arrival

<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>

Experimental Analysis of Microhabitat Selection by Juvenile Steelhead (Oncorhynchus mykiss) and Coho Salmon (O. kisutch) in a British Columbia Stream

1993 ◽  
Vol 50 (6) ◽  
pp. 1198-1207 ◽  
Author(s):  
Kurt D. Fausch
Keyword(s):  
British Columbia ◽  
Oncorhynchus Mykiss ◽  
Habitat Complexity ◽  
Field Experiments ◽  
Coho Salmon ◽  
Early Summer ◽  
Microhabitat Selection ◽  
Salmon River ◽  
Identical Construction ◽  
Stream Salmonids

Replicate experiments were conducted in the Salmon River, British Columbia, during early summer 1990 to test the relative importance of velocity refuge, visual isolation, and overhead cover to microhabitat selection by steelhead (Oncorhynchus mykiss) parr and age-0 coho salmon (O. kisutch). Four types of artificial Plexiglas structures, the first three of identical construction, had different portions painted to provide increasing habitat complexity: velocity refuge alone, velocity refuge with visual isolation, all three features combined, and overhead cover alone. Steelhead parr selected structures with overhead cover alone or all three features significantly more often than those without overhead cover. Steelhead also selected structures adjacent to the swiftest velocities available and closest to other natural overhead cover, which accounted for most differences in use of the same structure in different locations. In contrast, few age-0 coho salmon used any structures. Those that did selected the three types of structures with velocity refuge about equally, but significantly more often than those with overhead cover alone, regardless of their location. Field experiments such as this hold promise for elucidating mechanisms of habitat selection by stream salmonids.

An increase in habitat complexity reduces aggression and monopolization of food by zebra fish (Danio rerio)

1998 ◽  
Vol 76 (4) ◽  
pp. 770-772 ◽  
Author(s):  
Seán P Basquill ◽  
James WA Grant
Keyword(s):  
Danio Rerio ◽  
Coefficient Of Variation ◽  
Habitat Complexity ◽  
Structural Complexity ◽  
Zebra Fish ◽  
Resource Monopolization ◽  
Dominant Fish ◽  
The Relationship ◽  
Complex Habitat

We tested the predictions that an increase in the structural complexity of a habitat causes both a decrease in aggression and the monopolization of resources. Groups of three zebra fish (Danio rerio) were allowed to compete for food in a complex habitat with simulated vegetation and in a simple habitat with no vegetation. As predicted, both the levels of aggression by the dominant fish (P = 0.050) and the coefficient of variation of the amount of food eaten within a group (P = 0.020), a measure of food monopolization, were lower in the complex habitat than in the simple one. Fish that chased competitors more frequently ate more food in both habitats, but the relationship was stronger in the simple than in the complex habitat. Our results suggest that aggression is less useful as a mode of competition in habitats with greater structural complexity. Manipulating the structural complexity of the habitat may be a practical way of controlling the intensity of aggression and resource monopolization in groups of animals.

Fungal competition

1995 ◽  
Vol 73 (S1) ◽  
pp. 1259-1264 ◽  
Author(s):  
C. A. Shearer
Keyword(s):  
Community Structure ◽  
Field Experiments ◽  
Field Studies ◽  
Fungal Species ◽  
Competitive Interactions ◽  
Fungal Communities ◽  
Laboratory Studies ◽  
Experimental Field ◽  
Antifungal Antibiotics ◽  
Fungal Competition

Competition among fungal species isolated from a variety of habitats and substrates has been demonstrated frequently with laboratory studies. In some competitive interactions in culture, production of antifungal antibiotics by antagonistic fungi has been reported. Less well known is the extent to which competitive interactions occur in fungal communities in nature, the importance of competition in determining fungal community structure, and whether antifungal antibiotics are important in such interactions. Most field studies of fungal communities have been descriptive. Although such studies provide evidence of pattern in community structure, they do not demonstrate the occurrence of competition. Recent experimental field studies, in which the proportions of interacting fungal species were manipulated, provide more compelling evidence that interspecific competition does occur in nature. Knowledge about the extent of fungal competition in nature and its role in structuring fungal communities would be greatly improved if more of the following kinds of studies were undertaken: (i) experimental field studies involving manipulations of fungal species in a variety of habitats, (ii) comparative field and laboratory studies of the same fungal species, (iii) experimental field studies involving more than two fungal species, (iv) experimental and comparative studies throughout a range of environmental conditions, and (v) field experiments using both antibiotic- and nonantibiotic-producing fungal strains and (or) species. Key words: fungi, competition, community structure, antibiotics.

scholarly journals Conserving amphibians in the face of land development: integrating field experiments as a planning tool

2017 ◽  
Author(s):  
Alexander J. Felson
Keyword(s):  
Density Dependence ◽  
Habitat Quality ◽  
Field Experiments ◽  
Planning Process ◽  
Survival Rates ◽  
Land Development ◽  
Rana Sylvatica ◽  
Amphibian Conservation ◽  
Egg Mass ◽  
Habitat Variation

AbstractRegulations designed to guide development practices inadequately reflect ecological understanding and fall short of preserving viable habitats. Environmental consultants use rapid assessments and monitoring on individual ponds to rank pond habitat quality, relying on coarse proxies, including vegetative indicators, soil characteristics, hydroperiod, and breeding evidence in obligate species. Planners incorporate these rankings to inform the layout of neighborhoods, roadways, infrastructure and housing. However, important drivers of amphibian survival and fecundity—including metapopulation dynamics, habitat connectivity, watershed health, terrestrial density dependence, and environmental gradients—are often poorly measured and regulated. Given that development proceeds regardless, what options exists improve land development practices?Integrating experimentation into the planning process can inform land development and improve amphibian conservation. Working as part of the design team we employed an adaptive approach called designed experiment to inform development practices. We manipulated Ambystoma opacum larvae within enclosures to test the effects of inter-pond conditions (versus intra-pond density dependence) on the survival and fecundity of conspecifics, Rana sylvatica and Ambystoma maculatum. While the A. maculatum populations were decimated with only 1.5 % survival. For A. opacum and R. sylvatica results indicate habitat variation between ponds accounted for 63.7% and 50.3% of the variance in survival rates of larvae, respectively, and are not predicted by the presence and abundance of egg masses, while density effects accounted for 3.5% and 2.8% of the variation in survival. The results suggest that ponds ranked as high value based on egg mass counts may actually function as habitat sinks. This study illustrates the potential value of assessment approaches that emphasize habitat quality across pond clusters to guide mitigation, conservation, regulations, and to establish sites and funding for ecological research.

The tillering pattern in barley varieties: I. Production, survival and contribution to yield by component tillers

1969 ◽  
Vol 72 (3) ◽  
pp. 405-422 ◽  
Author(s):  
R. Q. Cannell
Keyword(s):  
Grain Yield ◽  
Nitrogen Fertilizer ◽  
Field Experiments ◽  
Survival Rates ◽  
Higher Order ◽  
Main Stem ◽  
True Leaf ◽  
New Varieties ◽  
The Difference ◽  
Variety Means

SUMMARYTwo field experiments have been conducted to investigate the pattern of tillering, ear emergence and survival of the component tillers of three barley varieties, representing old and new varieties. The varieties were grown under contrasting nitrogen fertilizer levels and plant spacings. The results reported are for the variety means and variety x nitrogen and variety x spacing interactions. After the main stem (M) the most frequently occurring tiller was the tiller appearing in the axil of the first true leaf (T2), followed by the coleoptile node tiller (T1) and the tiller in the axil of the second true leaf (T3). The T1 tiller occurred most frequently in the newest variety, Deba Abed, and least in the oldest one, Spratt Archer. Survival rates of the shoots were highest in M, followed by T2, T1 and T3. Higher-order tillers occurred relatively infrequently and had low survival rates. M contributed the largest percentage of the grain yield, followed by T2, T1 and T3. The 13% grain yield advantage of Deba Abed over Spratt Archer was mainly accounted for by the difference in production by the T1 tiller. The results are discussed in. relation to the only other known paper on component tillers in barley.

Asymmetrical intra-guild predation and niche differentiation in two pit-building antlions

2019 ◽  
Vol 66 (1-2) ◽  
pp. 82-90 ◽  
Author(s):  
Ofer Ovadia ◽  
Inon Scharf ◽  
Erez David Barkae ◽  
Tanya Levi ◽  
Yehonatan Alcalay
Keyword(s):  
Sandy Soil ◽  
Survival Rates ◽  
Loess Soil ◽  
Niche Differentiation ◽  
The Other ◽  
Competitive Interactions ◽  
Size Difference ◽  
Additive Effects ◽  
Growth And Survival ◽  
Direct Competition

Abstract Co-occurring species often compete with each other directly and indirectly. Intra-guild predation (IGP) is an extreme manifestation of direct competition, which involves the attack, killing and eating of potential competitors. We studied the competitive interactions between two pit-building antlion species that co-occur in the Israeli desert: Myrmeleon hyalinus residing in the more productive sandy soil, and Cueta lineosa solely inhabiting poorer loess soils. To understand the mechanisms driving C. lineosa away from the more productive habitat, we explored the factors triggering IGP of one antlion species on the other. We tested whether IGP is affected by soil type, depth and temperature. IGP was asymmetrical with M. hyalinus preying on C. lineosa, and it intensified as the size difference favoring the former increased. Interactive rather than additive effects governed IGP, which was lowest in sandy soil combined with low temperature, and highest in shallow loess soil. C. lineosa possesses a smaller head and thorax relative to its abdomen compared to M. hyalinus, providing a possible explanation for the advantage of M. hyalinus in direct competition. We then focused on the weaker competitor, C. lineosa, examining how it copes with competition induced by M. hyalinus. Both the growth and survival rates of C. lineosa declined in the presence of M. hyalinus. The asymmetrical IGP C. lineosa experiences from M. hyalinus combined with its competitive inferiority may explain why it is mostly found in poor habitats, while its intra-guild competitor is abundant in the more productive habitats.

Effects of reproductive interference on the competitive displacement between two invasive whiteflies

2014 ◽  
Vol 104 (3) ◽  
pp. 334-346 ◽  
Author(s):  
Di-Bing Sun ◽  
Jie Li ◽  
Yin-Quan Liu ◽  
David W. Crowder ◽  
Shu-Sheng Liu
Keyword(s):  
Niche Overlap ◽  
Simulation Modelling ◽  
Competitive Interactions ◽  
Reproductive Interference ◽  
Laboratory Population ◽  
Competitive Displacement ◽  
Female Progeny ◽  
Reduced Frequency ◽  
Exclusion Experiments ◽  
Major Factors

AbstractReproductive interference is one of the major factors mediating species exclusion among insects. The cryptic species Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED) of the whitefly Bemisia tabaci complex have invaded many parts of the world and often exhibit niche overlap and reproductive interference. However, contrasting patterns of competitive displacement between the two invaders have been observed between regions such as those in USA and China. Understanding the roles of reproductive interference in competitive interactions between populations of the two species in different regions will help unravel other factors related to their invasion. We integrated laboratory population experiments, behavioural observations and simulation modelling to investigate the role of reproductive interference on species exclusion between MEAM1 and MED in China. In mixed cohorts of the two species MEAM1 always excluded MED in a few generations when the initial proportion of MEAM1 was ⩾0.25. Even when the initial proportion of MEAM1 was only 0.10, however, MEAM1 still had a higher probability of excluding MED than that for MED to exclude MEAM1. Importantly, we show that as MEAM1 increased in relative abundance, MED populations became increasingly male-biased. Detailed behavioural observations confirmed that MEAM1 showed a stronger reproductive interference than MED, leading to reduced frequency of copulation and female progeny production in MED. Using simulation modelling, we linked our behavioural observations with exclusion experiments to show that interspecific asymmetric reproductive interference predicts the rate of species exclusion of MED by MEAM1. These findings not only reveal the importance of reproductive interference in the competitive interactions between the two invasive whiteflies as well as the detailed behavioural mechanisms, but also provide a valuable framework against which the effects of other factors mediating species exclusion can be explored.

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