Ecology I

1. Ecology I

2. What is it? • Haeckel (1866) • Study of relationship of animals to their environment • Now expanded to all organisms • Vague; what is really studied?

3. Basic Observations • Many species on Earth • Est. 1.9 million named and described • Est. 12.5 million out there • Each has unique, limited geographic distribution • Abundance of each species varies in space and time • Not all species occur together • Species occur in limited sets, or communities

4. General Definitions • Scientific natural history • Nat.history: the study of nature and natural phenomena • not quite appropriate; includes topics periplacial to ecology ( astronomy) • Structure and function of nature • The “working of nature • Seems to imply homeostasis

5. General Definitions cont. • Gaia hypothesis: • Earth’s total ecosystem operates as one giant living organism • Also not quite proper

6. Formal Definition • Ecology is the scientific study of the interactions that determine the distribution, abundance, and co-occurrence of organisms • Interactions occur between organisms and their environments • Environment includes other organisms, including conspecifics • Focuses on organisms, not environments • Also deals with who occurs with whom, and why

7. Relationship to other biological sciences • Ecology complex, synthetic • Close ties to many natural sciences • Evolution • Behavior • Genetics • physiology

8. History • See “selected events in the history of Ecology” handout

9. Goals • Description • Indigo bunting yearly cycle • Identification of proximate causes • Causal cue of bunting fall migration • Stephen Emlen experiment • Identification of ultimate causes • Evolutionary reason for migration • Prediction • Population response to global warming • Application • Steps to prevent extinction under global warming

10. Stephen Emlen Experiment • Captured 2 groups of Indigos and got them used to cages • Controlled photo period • Mimicked spring for one group • Bird exhibited Zuguuthue (migratory behavior) to North • Mimicked fall for other • Bird exhibited migratory behavior to south

11. Levels of Study • Primarily pops and communities • Population • Group of conspecifics • Community • Set of pops of different species co-occurring • Also look at individuals, ecosystems, and the biosphere

12. Ecological systems are hierarchical • Biosphere • Thin shell of Earth capable of supporting life • Ecosystem • Set of communities and their abiotic surroundings • Communities • Populations • Individuals/ramets

13. Scientific Method In Ecology • Observations of nature • Indigo migrate at certain times and directions • Hypothesis • Proposed photo period controls migration • Prediction • Changing photo period will cause birds to exhibit migratory restlessness in approp. directions • Test • Support/reject hypothesis • If support, can go back to test • Further tested directionality • If reject, go back to new hypothesis

14. Approaches • Experimental • Keep as many variables as possible the same • Manipulate one variable, chart response • One variable • Treatment group Requires both a control and treatment group

15. Modeling (simulation) • Establish a qual or quantitative “image” of the basics of complex systems • Used when trying to understand a system too complex to begin to think of an experimental hypothesis

16. Modeling cont. • Exponential growth example • Mathematically establish birth/death rate per individual • Multiply times # individuals @ time and make prediction about pop growth • dN/dt = rN • Run model or simulation • Determine if prediction is a pattern seen in nature

17. Comparative • Take advantage of similar natural circumstances that differ in some one or few attributes • E.g., island and island size • Communities have differences in species diversity • Due to size of area? • Example: boat day @ pymatuning

18. Environments, Populations, and Natural Selection

19. Environment? • Surroundings in general • Ex. Thermal environment • Proximate factors that affect location of an individual • Physiological tolerances (like temp) • Emphasis: survival • Proximate factors that affect the life cycle of an individual • Emphasis: reproduction • Proximate factors that affect relative performance of individual • Emphasis:differential survival, and reproduction: agents for natural selection

20. Populations • Composition • conspecifics • Location • At a particular place and time • Functional nature • Reproductive: individual capable of interbreeding • Ecologically: individuals that interact ecologically (like competition)

21. Populations cont. • Population as conceptual tool • Pops are rarely discrete (clearly spatially bounded) • Defined according to the interests of the investigator • Ex: Cerci’s choice of population of song sparrow. State ornithologist needs to pick a bigger population for conservation efforts • Formal definition: combo of previous page

22. Relationship between distribution and abundance • Density usually drops @ the edge of geographic distribution • As density approaches zero, the limit of distribution is approached • As density increases, distribution becomes more continuous- more “filled in” • Ex. Horned lark map: interbird distance • Distribution and abundance are flip sides of same coin

23. Natural Selection • Differential survival and reproduction resulting from the possession of different inherited forms of a trait • Requirements • Trait variation(often expressed graphically) • Trait heritability • Consistent relationship between trait form and survival/reproduction • If all 3 requirements hold, natural selection will occur • If less than 3, natural selection will not occur

24. Outcomes • Stabilizing: body mass • Narrowing • Mean doesn’t change • Trait variation decrease • No adaptive evolution • Disruptive: humming bird mating fights • Mean shifts • Trait variation decreases • Population has evolved • Adaptive evolution has occurred • Directional: Batesian mimicry (butterflies) • Individual at and around mean trait value are at disadvantage • Mean will be same • Higher variance • Adaptive evolution does occur even tho mean doesn’t change • Biologically, trait variance decreases

25. Important Points • Populations evolve, not individuals • Mutations do not arise in response to what the environment favors • Selection is decidedly non-random (see last requirement of N.S.) • Selection may result in change in trait mean (evolution) or no change in trait mean (no evolution, except for disruptive cases)

26. Examples: see graph handout • Peppered moth (directional) • Galapagos ground finch(directional) • Birth weight in humans (stabilizing) • Snow geese hatching time (stabilizing) • African swallowtail (disruptive) • Clutch size in blue tits (stabilizing) • David Lack • Lay eggs in tree cavities • Want to max dif between benefits and costs

27. External, ecological, and selective environments • External: factors of ones surroundings • Irrespective of whether factors influence an organism’s ecology • Ecological • When survival/reproduction of a given genotype is a function of surroundings • Species specific • Selective • When different genotypes have different finesses in a given environment

28. Conditions and Resources in Relation to Distribution and Abundance

29. Basic Terms • Biotic • Abiotic • Condition • A non-consumable environmental factor • Not ingestible or present in unlimited quantity • Temp/ H2O for aquatic species Resource • Consumable environmental quantity • Present in limited quantity

30. Combos of terms • Abiotic condition • temperature • Abiotic resource • light • Biotic condition • Vegetative structure for predatory birds • Northern Goshawk surprises prey in forest • Biotic resource • Voles captured and ingested by predatory birds

31. Attributes of Resources • Potential affect on survival and reproduction • Part of ecological environment • Factor must have an impact • Must be consumed • Ingested; needed for normal physiology (like food) and reproduction (like nest sites) • Consumption should reduce resource’s availability to other individs. • At the heart of competition • Consumption leaves less for yourself (not always), conspecifics, and everyone else • Ex: Jewel Weed • Sensitive to soil moisture levels

32. Effects on distribution and abundance • Notion of limiting factors • Factors operate @ edge of range to limit spatial dist. • Can also operate within range to restrict local distribution • Conditions and resources can interact to restrict distribution • Other considerations are important • Dispersal • Habitat choice

33. Analysis of Distributions

34. Transplant Experiments • Why doesn’t a species occur everywhere? • To answer: set up a transplant experiment • Establish a control group • Handle individuals identically to treatment group but place them back into native site • Establish a treatment group • Handle identically to control group, but move them to non-native site • Assess results • Did the treatment group survive and reproduce as well as the control group?

35. Transplant: Yes • Non native site is suitable for occurrence of species • Dispersal limitation or: • Limitation by habitat selection

36. Transplant: No • Non native site is not suitable • Limitation by biotic factors • Limitation by abiotic factors

37. Physiological Tolerances • Shelford’s Law of Tolerance • Distribution controlled by environmental factor far which the organism has the narrowest range of physiological adaptability • Distribution is controlled by factor species is most sensitive to, or has lethal limits for • Complications • Several factors may interact to set distributional limits • Acclimation can alter ranges of tolerance • E.g., arctic charr • Raised at 0 C, can withstand up to 0-20C • Raised at 5 C, max and min higher

38. Detecting Local Adaptation • Result of natural selection favoring traits that are advantageous under particular conditions • Ex. Plants spread slowly, changing slightly at each new site • E.g. toxic mine soils and grasses • Both did not do well in opposite environments • Toxic grass expended too much energy and were outcompeted • Norm. grass didn’t survive toxic soil • Can be detected using a reciprocal transplant exp.

39. Reciprocal Transplant Experiment • Plants from sites A and B switch • Survival and reproduction is compared to control groups • Control group should do better

40. Sequential Analysis for Reasons for Species Absence • See AoD outline

41. Dispersal, Behavior, and Biotic Interactions • Dispersal: the transport of organisms • Examples: • Gypsy moth • California Sea Otter • Shiny cowbird

42. Dispersal, Scale, and Gene Flow • Touch-me-not example (Impatiens capensis) • Dispersal distance • 2 types flower • Chasmogamous: seed pods explode and go far • Cleistogamous: seeds drop directly below plant Selective environments • Predict local adaptation • Depends on size of dispersal: too much gene flow won’t allow adaptation • Exhibits local adaptation on 10 cm scale

43. Colonization and Extinction • Dispersal ability • Taxon cycles of island forms • Stage 1: expansion • Stage 2: local adaptation and local extinction • Ex: House wren • In a group of island it is present except for 2 islands • Started exhibiting differences on different islands • The 2 islands are for away from one another • Local extinction: birds used to live on that island (fossils) Stage 3: widespread extinction ex) Adelaide’s Warbler • occurs on two islands and are very different between 2 islands • New biotic threat becoming extinct due to shiny cowbirds brood parasitism • Colonization of cowbird leads to warbler extinction

44. Habitat selection • Behavioral “choice” of whether or not to live in certain places • Ex: anopheles mosquitos • Palm warblers: bog, scrub, deciduous canopies • Habitat selection as an evolved response • Caused by natural selection in past

45. Biotic interactions that limit distributions • Predation • Example: common mussel • LougchIne • Rocky intertidal (glued to rock) • Very abundant on open coast and of small body size • Rare in Lough Ine, large body size • In the Lough they occur on steep slopes away from crabs and in fresh water aren’t • Transplant 1: • Treatment mussels gone within 48 hrs Transplant II w/enclosure • treatment group did well

46. Mussels • Wave action lighter in Lough • Filter feeders • Feeding efficiency lower on open coast • Body size different

47. Example: Desmognathus salamanders • N. Dusky Salamander and Mt. Dusky Salamander • Nelson Hairston, Sr. • Live in ravines • Mt. Dusky only on ravine slopes • N. Dusky on stream and stream bank • Competitors? • Nope. N. Dusky eats Mt. Dusky and thereby restricts it to suboptimal habitat • Both normally prefer stream/bank

48. Disease and Parasites • Ex. Chestnut blight (fungus) • Native to Eurasia • Introduced in late 1800’s and started to affect American Chestnut • Provided lots of food (nuts) • Used to be in 10s of millions on E. coast • Within 40-50 yrs all except a few were dead • Inadvertent unfortunate transplant experiment

49. Rabbits and Myxoma Virus in Australia • Rabbits not native to Australia • Bred very well there when introduced…as usual • Became a problem • Introduced myxoma virus to lower pop. • Biological control of pest

50. Competition • Example: Allelopathy and black walnut • Allelopathy • Black walnut puts hydroxy juglene into seed husks • Leeched into soil • Hydrolysis—juglone (plant toxin)—black walnut immune • Interference competition