Chapter 16: Species Abundance and Diversity (PDF)

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McGraw-Hill Education's Chapter 16 explores species abundance and diversity, environmental complexity, and disturbance. The chapter covers concepts such as the lognormal distribution, species richness, and examines how environmental factors influence species diversity.

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Chapter 16 Species Abundance and Diversity © 2019 McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. ...

Chapter 16 Species Abundance and Diversity © 2019 McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Outline Concept 16.1 Most species are moderately abundant; few are very abundant or extremely rare. Concept 16.2 A combination of the number of species and their relative abundance defines species diversity. Concept 16.3 Species diversity is higher in complex environments. Concept 16.4 Intermediate levels of disturbance promote higher diversity. © 2019 McGraw-Hill Education. Introduction Community – association of interacting species inhabiting some defined area. Community structure includes attributes such as number of species, relative species abundance, and species diversity. Guild – group of organisms that all make their living in a similar way. E.g. seed eating animals in the desert. Life-form – combination of structure and growth dynamics of a plant; similar to guild. © 2019 McGraw-Hill Education. 16.1 Species Abundance There are regularities in the relative abundance of species in communities that hold regardless of the ecosystem. A few are very abundant, a few are very rare, most are moderately abundant. Preston studied relative abundance and developed concept of distribution of commonness and rarity. © 2019 McGraw-Hill Education. The Lognormal Distribution Preston graphed abundance of species in collections as frequency distributions. Each interval is twice the preceding one, plotted on a log2 scale. These lognormal distributions have a bell- shaped curve. In most lognormal distributions, only portion of bell-shaped curve is apparent. Sample size has large effect. Significant effort needed to capture rare species. © 2019 McGraw-Hill Education. Sample Size and the Lognormal Distribution Copyright © McGraw-Hill Education. Permission required for reproduction or display. Access the long description slide. © 2019 McGraw-Hill Education. 16.2 Species Diversity Two factors define species diversity: Species richness. Number of species in the community. Species evenness. Relative abundance of species. © 2019 McGraw-Hill Education. Tide Pool A Tide Pool B 8 Species Richness The number of different Species Tide pool A has 4 species Tide pool B has 2 species Tide pool A has greater species richness than Tide pool B 9 Species Diversity Community 1 Community 2 10 11 12 13 A Quantitative Index of Species Diversity Shannon Wiener Index: s H = − pi log e pi ' i=l H’ = value of SW diversity index. Pi = proportion of the ith species. Logepi = natural logarithm of pi. s = number of species in community. © 2019 McGraw-Hill Education. Rank-Abundance Curves Can also portray relative abundance and species diversity within a community by plotting relative abundance of species against their rank in abundance. Produces a rank-abundance curve. Greater species evenness indicated by a lower slope, less evenness indicated by a steeper slope. © 2019 McGraw-Hill Education. Caddisfly Rank-Abundance Curves Copyright © McGraw-Hill Education. Permission required for reproduction or display. Access the long description slide. © 2019 McGraw-Hill Education. 16.3 Environmental Complexity In general, species diversity increases with environmental complexity or heterogeneity. Forest Complexity and Bird Species Diversity. MacArthur found warbler diversity increased as vegetation stature increased. Measured complexity as foliage height. Many studies have shown positive relationship between environmental complexity and species diversity. © 2019 McGraw-Hill Education. Foliage Height and Bird Diversity Copyright © McGraw-Hill Education. Permission required for reproduction or display. Access the long description slide. © 2019 McGraw-Hill Education. Niches, Heterogeneity and Diversity of Algae and Plants Hutchinson described “paradox of the plankton”. Phytoplankton communities live in relatively simple environments. Compete for the same nutrients. Yet many species coexist without competitive exclusion. Terrestrial plants present similar paradox. Environmental complexity may account for significant portion of the diversity. © 2019 McGraw-Hill Education. The Niches of Algae and Terrestrial Plants Algal niches appear to be defined by their nutrient requirements. Tilman found coexistence of freshwater diatoms depended upon ratio of silicate and phosphate. Diatoms vary in phosphorus uptake rate Ratio of silicate: phosphate varies across lake; diatom dominance also varies Variation in availability of limiting nutrients contributes to environmental complexity. © 2019 McGraw-Hill Education. Complexity in Plant Environments Lebo et al. studied spatial variation in nutrient and particulate concentrations in Pyramid Lake. Not a uniform solution across lake. Phytoplankton growing conditions vary. Robertson et al. studied nitrogen and moisture variation in abandoned field. Considerable patchiness across field. Spatial variability affects plant community structure. © 2019 McGraw-Hill Education. Soil and Topographic Heterogeneity and the Diversity of Tropical Forest Trees Jordan studied relationship of vegetation and soils in Amazon forest. Found forest diversity organized in 2 ways: Large number of species live within most tropical forest communities. Large number of plant communities in a given area, each with a distinctive species composition. Variation in soil influences number of communities. © 2019 McGraw-Hill Education. Variation in Vegetation Copyright © McGraw-Hill Education. Permission required for reproduction or display. Access the long description slide. © 2019 McGraw-Hill Education. Nutrient Enrichment Can Reduce Environmental Complexity Repeatedly observed negative relationship between nutrient availability and algal and plant species diversity. As nutrients increase, diversity of plants and algae declines. Increasing nutrient availability reduces number of limiting nutrients. Light becomes single limiting resource. Species most effective at competing for light becomes dominant. © 2019 McGraw-Hill Education. Nitrogen Enrichment and Ectomycorrhizal Fungus Diversity Areas of high atmospheric nitrogen deposition have declines in fungal diversity. May reflect shifts from aboveground fruiting bodies to belowground growth. Study in Alaska found decline in ectomycorrhizal fungal taxa along a soil nitrogen gradient, which corresponded to a decline in soil pH. Environment complexity can account for a portion of plant species diversity. © 2019 McGraw-Hill Education. Soil Nitrogen and Ectomycorrhizal Fungi Copyright © McGraw-Hill Education. Permission required for reproduction or display. Access the long description slide. © 2019 McGraw-Hill Education. 16.4 Disturbance and Diversity Intermediate levels of disturbance promote higher diversity. State of equilibrium – when environmental conditions remain relatively stable. Equilibrium maintained by opposing forces. Most environments are subject to various forms of disturbance. © 2019 McGraw-Hill Education. The Nature and Sources of Disturbance Disturbance difficult to define; varies with organisms and environments. Must be mindful of spatial and temporal scale. Many potential sources of disturbance. Abiotic forces (fire, hurricanes, floods, etc.). Biotic factors (disease, predation, etc.). Human-caused disturbance. © 2019 McGraw-Hill Education. Intermediate Disturbance Hypothesis Connell – disturbance is prevalent feature significantly influencing community diversity. Proposed high diversity is result of constantly changing conditions. Intermediate disturbance hypothesis. High and low disturbance reduce diversity. Frequent, intense disturbance. Infrequent, low intensity disturbance. At intermediate levels, enough time between disturbances allows wide variety of species to colonize, but no competitive exclusion. © 2019 McGraw-Hill Education. Disturbance and Diversity in the Intertidal Zone Sousa studied effects of disturbance on diversity of algae and invertebrates growing on boulders in the intertidal zone. Predicted level of disturbance depends on boulder size (larger boulders require more force to move). Found boulders supporting greatest diversity of species were those subject to intermediate levels of disturbance. © 2019 McGraw-Hill Education. Disturbance of Intertidal Boulders Copyright © McGraw-Hill Education. Permission required for reproduction or display. Access the long description slide. © 2019 McGraw-Hill Education. Disturbance and Diversity in Temperate Grasslands Whicker and Detling – prairie dogs are source of disturbance on N. A. prairies. Build extensive burrow systems. Remove vegetation around burrows, opening areas to plant colonization. Pest control programs reduced prairie dog populations 98%. Eliminated dynamic influences on plant communities, though burrowing gophers still influence plant communities. © 2019 McGraw-Hill Education. Applications: Disturbance by Humans Effects of human-caused disturbance are everywhere. Deforestation, pollution, etc. High levels of disturbance lead to declines in diversity. Thousands of species threatened with extinction. © 2019 McGraw-Hill Education. Urban Diversity In developed countries, 80% of people live in cities. Urban biota is diverse. Urbanization can reduce bird species richness and evenness, but in some landscapes substantial levels of diversity exist. Bird species richness peaks with intermediate land use intensity. © 2019 McGraw-Hill Education. Changes in Bird Communities Copyright © McGraw-Hill Education. Permission required for reproduction or display. Access the long description slide. © 2019 McGraw-Hill Education. Review Introduction. Species Abundance. Species Diversity. Environmental Complexity. Disturbance and Diversity. © 2019 McGraw-Hill Education.

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