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April 5th

by: Sierra

April 5th Biol 28600


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Notes from April 5th
Introduction to Ecology and Evolution
Joshua Springer
Class Notes
Ecology, evolution, Biology
25 ?




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This 52 page Class Notes was uploaded by Sierra on Friday April 8, 2016. The Class Notes belongs to Biol 28600 at Purdue University taught by Joshua Springer in Spring 2016. Since its upload, it has received 9 views. For similar materials see Introduction to Ecology and Evolution in Biology at Purdue University.


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Date Created: 04/08/16
Announcements:  Scantron sheets from Exam 2 available during TA office hours for the next week ONLY (Today, tomorrow, and next Monday)  Exam 3 is next Thursday and is online through the Pearson system rd  3 and Final homework assignment is now online and will help you study for the next exam  I will get to your emails later today For this lecture only read 392—417! © 2015 Pearson Education, Inc. iClicker  Predator populations usually lag in size and mimic what occurs in prey population sizes. This statement is:  A) True  B) False iClicker  True predators do not necessarily kill their prey immediately and may feed off of it for a long time before the kill. This statement is:  A) True  B) False Somewhere in: Parc Nationale de la Vanoise, France © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc. A bit of MATH today  Important for quantifying communities  Understanding diversity  Communicate results to other ecologists  Restoration  Wildlife management  Evolutionary implications  Over long time periods Community Structure  Species in a community have many different types of interactions  competition  predation  mutualism  Specific attributes of a community include  species number and relative abundance  physical structure  usually defined by plant growth forms  interactions among species  EVOLUTION! Biological Structure of Community Defined by Species Composition  individuals of each species in a community can be counted or estimated  A more meaningful measure is relative abundance, the proportion of each species relative to the total number of individuals of all species living in the community pi= n/i  p i proportion of individuals of species i  n i number of individuals of species i  N = total number of individuals of all species Table 16.1 © 2015 Pearson Education, Inc. Biological Structure of Community Defined by Species Composition  two features help us define community structure  species richness (S) – the number of species in the community  species evenness – how equally individuals are distributed among the species Species Diversity Is Defined by Species Richness and Evenness  Simpson’s diversity index refers to three closely related indices that consider both species number and relative abundance  Simpson’s index (D) – probability that two randomly selected individuals from the community will belong to the same species D = p 2 i  pi= proportion of total individuals in community represented by species i (relative abundance)  Value ranges between 0 and 1 Species Diversity Is Defined by Species Richness and Evenness  Because this range of values seems to be counterintuitive  D = 1 with no diversity (with one species, the probability that both selected will be the same is one)  D approaches zero with higher diversity  Simpson’s index of diversity = 1  D  The value increases with species diversity  This index represents the probability that two individuals randomly drawn from a community will belong to differences species Species Diversity Is Defined by Species Richness and Evenness  The Shannon index (or Shannon-Weiner index) is a widely used index of diversity that also considers species richness and evenness  This index is symbolized by H and is computed: H = (p)(inp) i  p = proportion of the total individuals in the i community represented by species i  ln = natural logarithm  minimum value = 0 (one species present)  maximum value = ln S (all species in equal numbers) Species Diversity Is Defined by Species Richness and Evenness  This maximum value, H max = S can be used to calculate an index of species evenness EH= H/H max  The values range from 0 to 1 (complete evenness with all species equally abundant) Dominance Can Be Defined by a Number of Criteria  Abundance alone is not always a sufficient measure of dominance  In a forest  There may be more small understory trees  But the fewer large tress have most of the biomass  In a deciduous forest in Virginia  relative abundance – 60% of the trees are red maple and dogwood  relative biomass – 60% of the biomass is in white oaks, which account for 9% of the relative abundance Table 16.2 © 2015 Pearson Education, Inc. Keystone Species Influence Community Structure Disproportionately to Their Numbers  Keystone species function in a unique and significant way within a community  Their effect is much greater and disproportionate to their numerical abundance  The role of a keystone species may be to  create or modify habitats  influence interactions among other species  The removal of a keystone species can lead to  changes in community structure  loss of biodiversity Keystone Species Influence Community Structure Disproportionately to Their Numbers  The coral Oculina arbuscula (lives off the coast of eastern North America) is a keystone species  Only coral in the region with a structurally complex, branching shape  Creates habitat for 300 species of invertebrates that live among its branches  Many species complete much of their life cycle within the coral Keystone Species Influence Community Structure Disproportionately to Their Numbers  Keystone herbivores can modify the community through their feeding activities  African elephants in savannas of southern Africa  feed mainly on woody plants (browse)  are destructive feeders, often uprooting, breaking an destroying the shrubs they eat  This reduction of tree and shrub density favors growth and reproduction of grasses  This community change benefits grazing herbivores, but not the elephants Figure 16.4a (a) © 2015 Pearson Education, Inc. Keystone Species Influence Community Structure Disproportionately to Their Numbers  Predators can be keystone species in communities  Sea otters are a keystone predator in kelp bed communities of the Pacific Northwest  Kelp beds are habitat for many species  Sea urchins feed on kelp  sea otters feed on sea urchins  killer whales feed on sea otters  Sea otter populations have declined as a result of killer whale predation – keystone predator removed  Sea urchin population has increased, and it has overgrazed the kelp, reducing habitat for other species Figure 16.7 Marsh hawk Links = arrows Upland plover Coyote Basal species = usually autotrophs Weasel Garter snake Clay-colored sparrow Meadow frog Badger Spider Pocket gopher Cutworm Prairie Crow vole Ground squirrel Grasshopper Grassland © 2015 Pearson Education, Inc. Figure 16.8 Which species is an omnivore? Top predator P C C Intermediate species 1 2 Intermediate species H1 H2 H 3 A A Basal species 1 2 Food Webs Describe Species Interactions  Intermediate species – either herbivores (H) or carnivores (C) that feed on other species and are the prey of other species (may also be omnivores)  Top predators (P) – feed on intermediate and sometimes basal species (if omnivores) but are not preyed upon themselves Food Webs Describe Species Interactions  Study of a Caribbean marine food web  total of 3313 trophic interactions among 249 species  Food web could be divided into five compartments based on  differences in body size  range of prey sizes selected  use of shore versus off-shore habitats  associated predators Figure 16.11 (a) (b) © 2015 Pearson Education, Inc. Section 16.5 Food Webs Describe Species Interactions  Any two species in a food web are linked by a single arrow (from prey to predator)  Community dynamics do not only involve direct species interactions  A predator may reduce competition between two prey species by keeping the population size of both species below the carrying capacity for each  These indirect effects must be included in an analysis of community structure Communities Have a Characteristic Physical Structure  Every terrestrial community has vertical structure  Stratification of vertical layers that are often distinct  Plant growth form largely determines this structure  size, branching, leaves  This vertical structure influences and is influenced by the vertical gradient of light Figure 16.12a Temperate Forest System (Idealized) Canopy The Understory Ground cover (herbs and ferns) Forest floor (dead organic matter) (a) © 2015 Pearson Education, Inc. Figure 16.12b Savanna(h) Forest System or ‘Oak Openings’ in North America Tree layer Grass layer Soil surface (dead organic matter) (b) © 2015 Pearson Education, Inc. Figure 16.13 90 Bird Vertical Distribution in 75 a Forest in Tennessee 60 Birds found ) ft here during 45 the breeding Height ( season— during 30 migration everything is a free-for-all 15 0 Ovenbird -yed vireo -yed vireo Wood thrush Pine wabilled cuckoo Carolina wren Tufted titmouse Red - Hooded Kentucky warblerumbreasted nuthatchl-ray gnatcatcher -ellied woodpecker YelBlue Red White © 2015 Pearson Education, Inc. Zonation Is Spatial Change in Community Structure  Zonation is the change in physical and biological structures of communities as seen when moving across the landscape  From the base to the summit of the Siskiyou Mountains at the California/Oregon border  Dominant tree species changes  There is a decline in species richness  From 17 to 9 species from lower to mid-elevation  Only 3 species at 1920–2140 m  The insects, birds, and small mammals also change Think about driving across the United States on Interstate-80 2,131 miles from Chicago, IL to San Francisco, CA Figure 16.15 Relative abundance (% Total number of individuals) Species Common name 1920–2140 m 1680–1920 m 1370–1680 m Abies nobilis Noble Fir 64.15 40.10 2.41 Tsuga mertensiana Mountain hemlock 35.77 18.97 0.07 Pinus monticola Western white pine 0.08 0.03 Pseudotsuga menziesii Douglas fir 0.16 14.75 Libocedrus decurrens Incense-cedar 0.35 2.44 Abies concolor White fir 39.50 54.32 Pinus lambertiana Sugar pine 0.03 0.98 Corylus rostrata Beaked hazelnut 0.13 2.64 Acer glabrum Rocky Mountain maple 0.73 6.44 Chamaecyparis lawsoniana Lawson cypress 12.55 Taxus brevifolia Pacific yew 1.83 Pinus ponderosa Ponderosa pine 0.10 Acer macrophyllum Oregon maple 0.51 Salix spp. Willow 0.14 Alnus spp. Alder 0.10 Amelanchier florida Florida juneberry 0.10 Sobrum americana American Mountain-ash 0.17 Castanopsis chrysophylla Giant chinkapin 0.44 (a) 1 0.1 0.01 Relative abundance 1370–1680 m 0.001 1920–2140 m 1680–1920 m 0.0001 0 10 20 30 Species rank (b) © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc. A very shortened trip through California—southeastern edge of central Valley west of Yosemite © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc. © 2015 Pearson Education, Inc. Figure 16.16 Spartina patens Juncus gerardi Salt meadow Black grass cordgrass Distichlis Ruppia maritima Spike grass Widgeon grass Myrica cerifera Iva frutescens Spartina Marsh elder Wax myrtle Salicornia alterniflora Glasswort Salt marsh cordgrass Spartina patens Tall Salt meadow Spartina Short Spartina MyprcaayyavrMarsh elderckgrass cordgrass Tallpartina alterniflora alterniflora Tidal Normal Shrub zone Salt meadow creek Pools and salt pans High tide low tide © 2015 Pearson Education, Inc. Figure 16.17 Beach Coquina Ghost crab amphipods clam Mole crab Blue crab Ghost shrimp High tide Sea cucumber Low tide Killifish I Haustorius II Hard-shelled Bristle Silversides clam worm Tiger III Lugworm beetle Flounder Olive snail Sand dollar Heart clam © 2015 Pearson Education, Inc. Defining Boundaries between Communities Is Often Difficult  Adjacent communities are distinguished by observable differences in physical and biological structure  How different do two adjacent communities need to be before they are considered to be separate communities? Defining Boundaries between Communities Is Often Difficult  The example of forest zonation in the Siskiyou Mountains, moving up the mountainside through elevational zones, covers a relatively short distance  In a larger area, differences in community structure increase  Patterns of forest zonation in Great Smoky Mountains National Park  Zonation pattern is complex, including elevation, slope position, and exposure  Communities are named for their dominant tree species Figure 16.19 0 500 1000 km Braun’s Forest Regions Mixed mesophytic Southeastern evergreen Western mesophytic Beech-maple Oak-hickory Maple-basswood Oak-chestnut Hemlock-white pine- Oak-pine northern hardwoods © 2015 Pearson Education, Inc. Quantifying Ecology 16.1 Community Similarity  Sorensen’s coefficient of community (CC)  This index is based on species presence or absence as a measure of the similarity between two areas  Requires a list of species for two sites or sample plots being compared CC = 2c/(s +1s )2  c = number of species common to both sites  s 1 number of species in community 1  s 2 number of species in community 2 Quantifying Ecology:Community Similarity  Comparing the two forest communities in Table 16.1  s 1 24 species  s 2 10 species  c = 9 species CC = (2  9)/(24 + 10) = 18/24 = 0.529  Values ranges for 0 to 1  0 = no species in common  1 = identical species composition in both communities Quantifying Ecology: Community Similarity  The CC does not consider relative abundance of species  The percent similarity (PS) is another index of community similarity that is based on the relative abundance of species within the communities being compared  Data from Table 16.1 include species abundance in each community as a percentage  For the species that are shared between the two communities (nine), add the lowest percentage for each Quantifying Ecology: Community Similarity  Both communities have yellow poplar  Community 1 = 29.7%  Community 2 = 44.5%  Both communities have red maple  Community 1 = 5.4%  Community 2 = 3.6% PS = 29.7 + 4.7 + 4.3 + 0.8 + 3.6 + 2.9 + 0.4 + 0.4 + 0.4 = 47.2  Range from 0 (no species shared) to 1 (identical species and relative abundances)


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