OUR Ecological Footprint - 4 1. 2. 3. 4. Buy efficient furnace; double combustion - gets at 97% of energy in natural gas

Chapter 17: Coevolution and Mutualism Yucca and yucca moth

Objectives Types of pairwise interactions Coevolution Strict (one-on-one) vs. diffuse Gene-for-gene concept Evidence for Mutualism Types Specificity Constraints against strict

Pairwise interspecific interactions ***Which is: +/-, +/0, +/+, -/-, -/0 ? Mutualism Facilitation (Commensalism) +/0 Amensalism -/0 Herbivory Predation Parasitism Disease Competition Amenalism: huge tree and seedling competing for resources; seedling makes infinitesmal dent into tree’s resources. Really very asymmetrical competition. Commensalism: epiphytes on trees; remoras (sharpsuckers) have sucker on dorsal fin; attadh to shark or rays 1) saves energy due to limited swimming 2) gathers food ccraps when host is feeding Parasite: consumes part of blood or tissues of host, usually without killing the host. Pathogen: parasitic organism that causes a disease in its host.

Fluidity of interspecific relationships: Can evolve from one type to another. Switch + and - signs of interaction, e.g. +/+ to +/-.

Symbiosis: an intimate and often obligatory association of two species, usually involving coevolution. May be parasitic or mutualistic. Lichen = algae + fungus

***Define ‘coevolution’: Interacting species evolve in response to each other (how many species?) Traits of each species affect fitness of individuals of other species. Traits have variation and a genetic basis. May be mutualistic or antagonistic relationship.

Strict coevolution: narrow sense One species stimulates evolution in one other species and vice versa. Limited to a pair of species May be rare and limited to very strong interactions Diffuse coevolution: broad sense Species simultaneously respond to an array of complex interactions with many other species.

Batesian mimicry: “a sheep in wolf’s clothing” shows 1/2 of coevolution equation; selection by predator on prey C53.7 When disturbed the hawkmoth larva resembles a snake. 9

Batesian mimicry: palatable species mimic unpalatable models. wasp- unpalatable (model) ***Which is more common: model or mimic? What must predator do to make system work? Mantid + moth palatable (mimic) Figure 4 10

Mullerian mimicry Both have stingers that release toxins. Figure 5 C53.8 Both have stingers that release toxins. Cross-mimicry presumably benefits both species because predators learn more quickly to avoid any prey with these distinctive markings. Both have stingers that release toxins. 11

Mullerian mimicry: unpalatable species resemble each other Mullerian mimicry: unpalatable species resemble each other. Each species is both model and mimic. Get benefit of warning from two species. 12

Mullerian mimics: unpalatable organisms share pattern of warning coloration. 13

Gene - for - gene concept: ‘evolutionary arms race’ E.g. plant - pathogen interaction Based on: single gene conferring resistance vs. single gene for virulence Back and forth: change in gene, then selection: favor plant, then pathogen, then plant, then pathogen… Race escalates with addition of each new trait.

Describe the coevolutionary ‘arms race’ between rabbits and myxoma virus. Include these concepts: Genes for resistance Genes for virulence Pre-adaptation Time Introduce virus Coevolution

Explain the pattern in terms of: changes in frequency of virulence and resistance genes

What evidence is used to infer coevolutionary relationships? Closely related groups of herbivores feed on closely related host plants. Suggests a long evolutionary history of interaction.

Coevolution between chemical defenses of plants and their herbivores; uses phylogenetic relationships to build an inferential argument. Chemicals go from being widespread in all plants (precursor to lignin) to being highly specialized and only in few familieis and few genera Surveys of herbivorous insects: Found on AFC plants tended to be extreme diet specialists, most being found on no more than 3 genera Specialists abundnat compared with few generalists found on AFC plants and compared with all herbivores found either on LFC platns or on umbellifers lacking FCs. Although LFCs and especially AFCs are extremely effective deterrents to most herb. Insects, some genera that have evolved to tolerate these chemicals have become successful specialists. Storng casee for coevoltuion Taxonomimc distribution: plants with LFcs subset of those containing umbelliferone, and that AFCs are even smaller subset of those contianing LFCs. (same pattern of evolutionary sequence of plant defenses processing toward AFCs Insects that specialize on plants contiaing LFCs belong to groups that characteristiaclly feed on lants continaing umbellerione, and those that specialize on plants with AFCs have close relatives that feed on plants containing LFCs. Patterns of taxonomic distrtibuion are consistent with coevolution within the system. Insects most specialized

Experimental Evidence: Question: Do ants and treehoppers have a mutualistic relationship? Treehoppers - herbivores Spiders - predators of ‘hoppers

***Develop an “if…then…that addresses this question. Hypothesis:  Prediction: Experimental Design?? What is independent? dependent variable?

What is major conclusion?? Mutualism or not? Figure 1

Mutualism: two species specialized to perform a complementary (positive) function for each other. 1) Mutualism: trophic Partners specialized in complementary ways to obtain limiting energy and nutrients ***Examples? Need pix of lichen; bacteria in cow rumen

Legumes and N-fixing Rhizobium plant gives bacteria shelter bacteria gives plant usable N Figure 2

Endomycorrhizae in root cells of orchid fungus absorbs nutrients, e.g. P for plant plant gives carbos, vitamins, amino acids to fungus SS17.18 endomycorrhizae Figure 3

Cleaners of parasites and diseased tissue 2) Mutualism: defensive Species receive food or shelter in return for defending against natural enemies. Cleaners of parasites and diseased tissue Moray eel: gets parasties removed Shrimp = ectoparasite (and diseased tissue) cleaner; gets food Other cleaners are fish; if remove cleaner fish increase in parasitism and disease. Figure 4

Ant-plant defense mutualism: Acacia and Pseudomyrmex ants K14.5 Acacia Figure 5

***What is evidence that Acacia benefits from presence of ants?

***Predict a possible evolutionary response when a plant, but not the ant, invades an island. On the mainland they are mutualists. What is the assumption?

3) Mutualism: dispersive Animal vectors move plant pollen and seeds (gene flow) in return for food rewards.

Pollination syndromes provide circumstantial evidence of at least diffuse coevolution.

Orchid and male euglossine bee Some plant-pollinator interactions are highly specific (obligate mutualism). Orchid and male euglossine bee SS17.23

Seed dispersal (no or diffuse mutualism) C30.16

Plant-seed disperser mutualism SS17.26 cedar waxwing - mountain ash?

Ant-plant mutualism: elaisomes R25.6 elaisomes

Constraints on evolution of strict mutualisms Species diversity diffuses selection from any one species. Succession, disturbance, and flux in species’ ranges change selection over time and space. Complex genetics promotes uneven rates of evolution among mutualists; one of pair has more potential to respond than other.

Another obligate strict mutualism of a plant-pollinator/seed predator. Yucca and its moth Figure 8

Some adaptations were present before the establishment of the mutualism (preadaptations) and occur in close relatives that are not mutualists.

Exam question: Acacia trees have a mutualistic relationship with ants Exam question: Acacia trees have a mutualistic relationship with ants. 1. Develop an “if…then…” relating to the benefit of the mutualism to the plant. 2. Does the existence of the mutually beneficial traits in this mutualism confirm this relationship as an example of coevolution? Explain, including what is the best evidence of coevolution. 3. Not all species of acacia form a mutualism with ants. In a setting where herbivore pressure is low, why might the mutualism not have arisen? 4. In some areas where herbivore pressure is high, the mutualism with ants has not arisen. Predict two alternative anti-herbivore defenses these acacias may be using.