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Chap.23 Chap.24 Chap.25 Chap.26 Terrestrial Ecosystems Aquatic Ecosystems Coastal and Wetland Ecosystems Large-scale Patterns of Biological Diversity Smith & Smith (2015) Elements of ecology. 9th. Ed. Pearson. Part Seven Ecological Biogeography 生態 生物地理學 鄭先祐 (Ayo) 教授 生態科學與技術學系 國立臺南大學 環境與生態學院 Chap.26 生物多樣性的大尺度樣式 Large-Scale Patterns of Biological Diversity Smith & Smith (2012) Elements of ecology. 8th. Ed. Pearson. 鄭先祐 (Ayo) 教授 生態科學與技術學系 國立臺南大學 環境與生態學院 Although covering only 6 percent of the land surface, tropical rain forests contain over 50 percent of all known terrestrial species. 3 Chapter 26 Large-Scale Patterns of Biological Diversity Nearly 1.4 millions species have been identified and named, though more are discovered each year E.O. Wilson (Harvard University) suggested that closer to 10 million species exist. Over evolutionary time, new species evolve while existing species become extinct. Environmental conditions have influenced species evolution and the resulting biological diversity in various geographic regions around the world. 4 5 6 26.1 Earth's Biological Diversity Has Changed through Geologic Time Long-term evolutionary changes have occurred over geologic time. The number of species has been increasing for the past 600 million years. 7 Fig. 26.3 Estimated species richness of fossilized invertebrates over geologic time. 8 26.1 Earth's Biological Diversity Has Changed through Geologic Time Though the number of terrestrial vascular plants has continuously increased for the past 400 million years, the dominant groups have shifted dramatically Psilopsids (松葉蕨類) Pteridophytes (蕨類) Gymnosperms (裸子植物) Angiosperms (被子植物) 9 Fig 26.4 Pattern of expansion and reduction of major terrestrial plant groups during 400 million years of plant evolution. 10 26.2 Past Extinctions Have Been Clustered in Time The pattern of increasing diversity through geologic time has been accompanied by several extinction events. Permian (225 mya) 90 percent of shallow-water marine invertebrates disappeared. Cretaceous (65 mya) Dinosaurs and many other species went extinct. Caused by asteroid impact which altered climate, oceanic circulation, and increase in volcanic and other tectonic activity. 11 26.2 Past Extinctions Have Been Clustered in Time Pleistocene (10,000 years ago) Ice-Age mammals went extinct (e.g., woolly mammoth, giant sloth) Caused by receding of ice sheets and/or hunting by humans Modern extinctions 75 percent of extinction since 1600 due to human activity (e.g., habitat destruction, introduction of species) 12 Fig. 26.5 The geologic timescale and mass extinctions in the history of life. The fossil record profiles mass extinctions during geological times. The most recent mass extinction occurred during the Cretaceous, which wiped out more than half of all species, including the dinosaurs. 13 26.3 Regional and Global Patterns of Species Diversity Vary Geographically There are distinct patterns for species richness. Globally, species diversity declines as you move northward and southward from the equator. Several hypotheses offered for the pattern of species diversity and latitude Community age Spatial heterogeneity of the environment Stability of the climate over time Ecosystem productivity 14 Fig. 26.6 Geographic variation in the distribution of (a) trees in North America. Contour lines connect points with about the dame number of species. 15 Fig. 26.6 Geographic variation in the distribution of (a) mammals in North America. Contour lines connect points with about the dame number of species. 16 Fig. 26.6 Geographic variation in the distribution of (a) birds in North America. Contour lines connect points with about the dame number of species. 17 Fig. 26.7 North American latitudinal gradients in species richness for (a) trees based on cells of 2.5 x2.5 latitude/longitude. Species richness per cell is based on range maps for individual species. 18 Fig. 26.7 North American latitudinal gradients in species richness for (a) mammals based on cells of 2.5 x2.5 latitude/longitude. Species richness per cell is based on range maps for individual species. 19 Fig. 26.7 North American latitudinal gradients in species richness for (a) birds based on cells of 2.5 x2.5 latitude/longitude. Species richness per cell is based on range maps for individual species. 20 26.4 Species Richness in Terrestrial Ecosystems Correlates with Climate and Productivity D.J. Currie and V. Paquin (University of Ottawa, Canada) found that even though species richness is correlated with climatic factors, it correlates most strongly with estimates of actual evapotranspiration (AET) AET is the flux of water from the terrestrial surface to the atmosphere through evaporation and transpiration AET is positively correlated with net primary productivity Environmental conditions favorable for photosynthesis and plant growth may give rise to increased plant diversity over evolutionary time 21 Fig. 26.8 Relationship between annual measure of actual evapotranspiration (AET) and tree species richness for North America. 22 26.4 Species Richness in Terrestrial Ecosystems Correlates with Climate and Productivity Currie also found a positive correlation between potential evapotranspiration (PET) and regional patterns of mammal and bird species richness across North America PET is correlated with temperature, solar radiation, precipitation, humidity, and so forth Currie reported a positive correlation between vertebrate diversity and plant species diversity This may be related to the positive relationship between primary and secondary productivity 23 Fig. 26.8 Relationship between annual measure of actual evapotranspiration (AET) and (a) mammals species richness for North America. 24 Fig. 26.8 Relationship between annual measure of actual evapotranspiration (AET) and (b) birds species richness for North America. 25 26.4 Species Richness in Terrestrial Ecosystems Correlates with Climate and Productivity Animal diversity is linked to plant diversity because plants: Are a potential food source for animals Provide suitable habitat for animals (e.g., structural diversity within plant communities) Environmental heterogeneity also gives rise to increased plant species diversity Mountainous regions generally support more species than consistent terrain of flatlands In North America, a general increase in diversity on an east–west gradient relates to an increase in environmental heterogeneity (diversity) 26 26.4 Species Richness in Terrestrial Ecosystems Correlates with Climate and Productivity Mountainous regions support greater species diversity but there is a general pattern of decreasing species richness with increasing elevation. Mechanism for this decrease may be similar to those involved with increasing latitude (e.g., temperature, AET) The pattern of species richness and elevation may be confounded High-altitude communities occupy a smaller spatial area and tend to be more isolated. 27 Fig. 26.10 Relationship between species richness and altitude for (a) birds species in New Guinea. 28 Fig. 26.10 Relationship between species richness and altitude for (b) mammal species in Himalayas. 29 Fig. 26.10 Relationship between species richness and altitude for (c) vascular plants in New Guinea. 30 26.5 In Marine Environments, There Is an Inverse Relationship between Productivity and Diversity Globally, species diversity declines as you move northward and southward from the equator A correlation between species richness and productivity is not as apparent in the marine environment The primary productivity of the oceans increases from the equator to the poles 31 介形蟲亞綱動物 十腳類動物 磷蝦 Fig. 26.11 Latitudinal gradient of species richness (a) four groups of pelagic (遠洋) organisms caught at six stations along 20o W (longitude) in the Northeast Atlantic Ocean. 32 等足類 腹足類 雙殼類 Fig 26.11 (b) Three groups of benthic organisms in the North Atlantic. 33 26.5 In Marine Environments, There Is an Inverse Relationship between Productivity and Diversity The correlation of latitude and productivity in marine environments is opposite the pattern observed for terrestrial environments Except in areas of upwelling Seasonality, rather than total annual productivity, may influence the local patterns of diversity for pelagic and benthic species Primary productivity in the ocean is influenced by seasonal dynamics of the thermocline and vertical transport of nutrients 34 26.5 In Marine Environments, There Is an Inverse Relationship between Productivity and Diversity The permanent presence of a thermocline in the tropical ocean waters results in a low but continuous patter of primary productivity throughout the year. Low diversity in the oceans at high latitudes may be a result of the Quaternary period of glaciation that covered much of the polar oceans 35 26.6 Species Diversity Is a Function of Processes Operating at Many Scales Local (alpha) diversity is the species diversity of individual communities Quantifying local diversity is problematic It is difficult to define community boundaries The relationship between diversity and area makes it difficult to compare patterns of species diversity between communities/ecosystems that differ in size Local patterns of diversity change over time during succession. 36 26.6 Species Diversity Is a Function of Processes Operating at Many Scales Regional (gamma) diversity is the total species diversity across all communities within a geographic area A comparison of broad-scale patterns can be confounded by time (e.g., seasonal changes that affect water temperature, migration patterns) 37 Quantifying Ecology 26.1 Quantifying Biodiversity: Comparing Species Richness Using Rarefaction Curves The estimate of species richness will vary with sample size As more samples are taken, more species will be recorded An accumulation curve records the total number of species revealed during the survey, as additional sample units are added to the pool of all previously observed/collected samples The point at which the curve reaches an asymptote defines the optimal sample size 38 Quantifying Ecology 26.1 Quantifying Biodiversity: Comparing Species Richness Using Rarefaction Curves For a meaningful comparison of the species richness derived from different surveys, we must obtain values for the same sample size for each survey A rarefaction(稀釋) curve is produced by repeatedly resampling the total pool of samples (N) at random, plotting the average number of species represented by 1, 2, …, N samples A statistical expectation of the corresponding accumulation curve over different reorderings of the samples 39 40 41 Chap.26 Large-scale Patterns of Biological Diversity Ayo NUTN website: http://myweb.nutn.edu.tw/~hycheng/