Mon Tues Wed Thurs Fri Week of Nov

Mon. Tues. Wed. Thurs. Fri. Week of Nov. 10 Week of Nov. 17 River ecology lab – dress for weather Week of Nov. 24 No lab – Thanksgiving Lab Exam (bring calc. ) No lecture Week of Exam 3 Dec. 1 Independent project presentations 1

Ecology does not roll over into Genetics Last chance to take Genetics. 2

Sp. interactions – 17 18 (through fig. 18. 7), 19 20 (only covering p. 391) Community ecology – 21 22 3

Structure of course Environmental variability Organisms Ecosystems Populations Species interactions Communities Applied Ecological Issues 4

Mutualistic interactions + A B + 5

Different types of mutualisms 1. Those involving energy, nutrients, and/or water (Trophic mutualisms) Examples? 2. Those involving defense (Defensive mutualisms) Examples? 3. Those involving dispersal (Dispersive mutualisms) Examples? 6

Lichens 7

Obligate mutualism – species are so dependent on each other that they cannot live without each other 8

Acacia trees and acacia ants 9

Trees without ants Trees with ants 10 % of shoots with herbivores on them

Acacia height (cm) 120 60 0 May 25 June 16 Aug. 03 11

Which are more general? seed dispersal or pollination mutualisms 12

Figure 20. 16 13

Structure of course Environmental variability Organisms Ecosystems Populations Species interactions Communities Applied Ecological Issues 14

Communities What is a community? How are communities described? How are species organized within a community? How do communities change over time? 15

Community: an association of populations of different species living in a particular area Community ecology: focus is understanding the diversity and relative abundance of species in the community 16

Questions asked by community ecologists What determines the number of species in a community? How does disturbance affect community structure? Does adding new species change the way a community functions? 17

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Figure 21. 6 a Ecotone- zone of transition between 2 distinct communities 19

Figure 21. 9 boundaries less distinct 20

Communities What is a community? How are communities described? How are species organized within a community? How do communities change over time and space? 21

How are communities described? number of species = species richness evenness = # individuals/species diversity = richness and evenness relative abundance 22

Figure 21. 18 many rare few dominant Relative abundance 23

5 species high evenness 5 species lower evenness 24

Diversity = combination of richness and evenness - contribution of species weighted by relative abundance 25

5 species high evenness Which has higher diversity? 5 species lower evenness 26

What determines diversity of a community? 27

What determines diversity of a community? 1. diversity is related to area 2. diversity is related to variability Lots of other theories that attempt to explain controls on diversity 28

Figure 21. 20 one of the most common patterns in ecology 29

What determines diversity of a community? 1. diversity is related to area 2. diversity is related to variability Lots of other theories that attempt to explain controls on diversity 30

Figure 23. 5 31

Hard to separate variability and area - typically larger areas have more habitat variability Lesser Antilles – island size and habitat diversity vary independently - two kinds of islands - tall volcanic – diverse habitats - low raised seabed – 1 habitat - both kinds of islands come in all sizes 32

Figure 21. 21 33

Communities What is a community? How are communities decribed? How are species organized within a community? How do communities change over time? 34

How are species organized within a community? 35

Suppose there are 3 species in a community, species A, B, and C. When you remove species A from the community, species C goes extinct. What can you conclude about the relationship between species? a. b. c. d. Species A is a predator of species B. Species A is a prey of species C. Species B is a competitor of species C. All of these are possible. 36

Figure 21. 12 37

Connectedness web Starfish Snail Chitons Limpets Mussels Barnacles 38

Energy web Starfish Snail Chitons Limpets Mussels Barnacles 39

Functional/interaction web Starfish Snail Chitons Limpets Mussels Barnacles 40