Unformatted text preview: Lecture 3. ES 100 Lecture Ecological genetics, Ecological Speciation, Accidents of history history Logistics AGAIN: Logistics Gauchospace site will be up and running later Gauchospace today. You will receive a welcome email and then can enter it. Post a picture if you have one so we can associate name with face. so SECTIONS: please try to avoid changing SECTIONS: sections. You will not be listed in the proper gauchospace group and will be harder to contact for section messages. for ALSO Thursday and Friday at 12 sections are ALSO now PACKED. The following seniors still need to give me section prefs for add codes: codes: Andrew Lanes Anand Shivaprasad Recap. Lecture 2 Recap. Scientific method Examples of how to test hypotheses Evolution Overview Define evolution, fitness, natural selection Describe key elements of evolution by natural Describe selection selection Importance of genetic variation to evolution & Importance ecology ecology Define ‘ecotype’ Today: Today:
I. II. III.
a. b. Finish ‘ecotypic variation’. Speciation overview. Accidents of history
Individual traits Species distributions Coast Interior Shorter stature Perennial Thicker leaves Mildew Mildew resistant resistant Taller, faster Taller, growing growing Annual Lvs thin, more Lvs vibrant green Mildew Mildew susceptible susceptible Ecotypes…. Ecotypes…. How do you know differences are genetic? How do you know the differences are How adaptations to different environments ? adaptations Ultimate goal=identify if differences between populations are ‘adaptive’ between DEFINE ADAPTATION…..
•Trait that increases your fitness in a given environment. •If you did not have that trait, you would have lower fitness in that environment. 1. Genetics: Poppies: Horticultural evidence suggests the ecotypes are genetically distinct but they can interbreed 2. Differences adaptive ? Interior form grown at coast = highly susceptible to mildew but does mildew reduce fitness ??? Coastal form in interior = inferior competitor. Would it be able to persist there ? NOT DIFFINTIVE YET Adaptive stories are fun but Adaptive difficult to test Invite you to think about ecological differences among sites Good test involves: Good Common gardens and /or Reciprocal transplants Mainland bush poppy Santa Cruz Island bush poppy Mainland bush poppy Santa Cruz Island bush poppy Narrow leaves Smaller leaves Shorter stature Shorter shrubs shrubs Large, wide Large, leaves leaves Plants almost Plants tree-like in stature stature Why ?? Hypotheses: Hypotheses: Differences are environmentally induced, not Differences genetic genetic Biotic selective pressures different on island Biotic (fewer herbivores, pathogens etc) (fewer Physical environment more harsh on mainland Physical (smaller leaves adapted to harsher environment) (smaller Accident of history (original island colonist had Accident bigger leaves so all decendents have bigger leaves.) leaves.) Possible experiments: Possible Establish common gardens (mainland and Establish on island). Grow both forms. on Subject forms to environmental stress, Subject herbivores, pathogens… herbivores, Establish measures of performance Compare between populations grown at Compare ‘home’ vs away and between ecotypes. ‘home’ Many plant studies on ecotypic variation using reciprocal transplanting or common gardens transplanting
ANIMALS FORM ECOTYPES TOO BUT ecological importance harder to test SC Island Mainland Text example of sea anemones… Text
•Transplanted three colonies from each site to all other sites •Measured proportion of adults brooding young after time •Green island forms do best everywhere! •Strickland Bay forms do worst WHY ? Why do we care about ecotypic differences in natural populations? differences Restoration: use best adapted genotypes Conservation rare spp: ensure appropriate Conservation genetic structure of population you are protecting. protecting. Ethnobotany: preserve indigenous genetic Ethnobotany: diversity diversity Insure survival of species if disease wipes Insure out some populations Ecological genetics questions: Ecological What role does genetic variation play in What population extinction? How do population size and genetic variation How relate ? How does genetic variation influence role that a How species plays in a community? species How will populations/species change with How climate change? climate How does human harvesting of wild populations How influence genetics? influence II. Speciation: When are genetic differences strong enough to result in speciation? in Pepper moths in England, pre & post industrial revolution Selective force = pollution (reviewed in your text, chapter 2) NOT SPECIATION Members of a species can breed in nature and produce fertile offspring For speciation to occur there must be a For barrier between populations to prevent interbreeding OR selection must be very strong strong Interbreeding = gene flow Interbreeding Speciation only possible Speciation without gene flow without unless selection is extremely strong unless Barriers to interbreeding….. Barriers Numerous species or subspecies on Channel Islands on
(=island endemics (=island endemics e.g. bush poppy) Finch speciation Finch speciation Galapogos Islands Ecotypes become different species when they can no longer interbreed and produce successful offspring and Barrier could be Barrier Physical (mountains, water, inhospitable Physical terraine) Temporal (differences in timing of breeding) Physiological (chemical, morphological) Behavioral or mate recognition How can environment drive speciation ? speciation Example from California with no Example physical/geographic barrier physical/geographic Plants on and off serpentine soils Plants on and off serpentine soils California state rock =Serpentinite Serpentine soil = derived from serpentinite. High in heavy metals (nickel, lead, arsenic, etc) + abnormally high in magnesium Seeds arrive from surrounding area onto serpentine serpentine -most do not survive to turn into adult plants -most -serpentine soil = strong selective force -serpentine Serpentine Eventually appropriate genotype emerges v Mimulus guttatus Widespread (common monkeyflower) Mimulus nudatus Serpentine endemic (serpentine monkeyflower) M. guttatus is the “parent” of M. nudatus. M. M. Mimulus guttatus widespread Mimulus nudatus Serpentine endemic M. nudatus tolerates higher Ni and Mg and lower Ca than M. guttatus. (divergence for adaptive characteristics) (divergence It also flowers earlier than M. guttatus, and attracts sweat bees rather than bumblebees. ( = reproductive timing & pollinator barriers) reproductive How do we know they are different species ? species Look different (not enough) Cannot produce fertile offspring ! How did speciation occur ? How Speciation Model: First step in the origin of M. nudatus is Mg and Ni tolerance. Pollen still likely being interchanged. Strong selection by soil for metal tolerant mutants. Further strong selection on serpentine favored adaptations to drought and low nutrients, including earlier flowering time (due to lack of resources). Attraction of different pollinators may have resulted from separation of flowering time. This eventually led to the mating isolation & fixation of genes for intersterility (M. nudatus pollen not fertile on M. guttatus and vice versa). Importance to conservation? Importance Habitats with unique soils or strong Habitats selective pressures are active sites of evolution, endemism, often high diversity evolution, Should be included in conservation planning. California is full of isolating mechanisms & unique habitats mechanisms Mountain ranges with deep valleys in Mountain between between Waterways Islands Serpentine & other unique soils Strong climate gradients Isolating mechanisms…. Isolating Explain high diversity and large number of Explain endemics. >5,100 species of plants; >5,100 2,300=endemics Must understand factors that contribute to Must diversity and uniqueness and include them in regional planning. them Speciation take home: Speciation Define species Describe role of isolating mechanisms, Describe barriers and importance of gene flow barriers III. Accidents of history III. Explanations for current morphologies or Explanations physiologies OR for patterns of species distributions must include an understanding of history. Evolutionary ecology Evolutionary How does an organisms physiology or How morphology allow it to persist in environment? (How is a particular trait beneficial?) Who would disperse these fruits ? Who
Large hard fruits Accumulate under trees in tropics Evolved in response to now extinct animals Current form =leftover adapation from past
Fruit gomphotheres ate. D. Jansen & P. Martin. Chorisia speciosa, native to Brazil and Argentina
Why these heavy spines ?
Adaptation to extinct animal ? No pressure yet to lose the trait where it is not needed ? Trait loss may take many thousands of yrs. Santa Lucia fir (Abies bracteata) Occurs only in small part of Occurs California (NOWHERE ELSE) California What is strange shape an adaptation to ? Hypothesis: Shedding of SNOW ? Did it evolve in a more Did snowy environment ? What explains its restricted distribution ? -maybe needs cooler microsites? -maybe -cannot tolerate fire Maybe it evolved under very different climate & fire conditions to Maybe what we see today ? Today it just lives in refugia from fire where it what isn’t too hot ? Don’t assume that all traits are Don’t ‘adaptations’ ‘adaptations’
TO BE AN ADAPATION….. TO Trait must be heritable Must confer a fitness advantage Selective environment must be clear Trait should have appeared historically Trait when selective force became common when ACCIDENTS OF HISTORY ACCIDENTS PART 2. Geographic distributions of species Geographic Biogeography…. Biogeography…. Study of geographic distribution of species To understand distribution should know: Physiological limits of species Biotic interactions that limit distribution Dispersal potential of species Vicariance: historical factors that could Vicariance: influence current patterns Distribution of flightless birds cannot be explained without history explained
-Widely distributed -Related to one another BUT FLIGHTLESS -So they could not have dispersed to different continents (Townsend et al) Continental drift essential to understand pattern Townsend et al. Africa & So. Am. pull apart Tasman sea opens between Australia and NZ Lesson Lesson Don’t assume individual traits and species Don’t distributions are perfect match to environment environment Historical accident (e.g. extinctions), past Historical climates, vicariance can play role in current patterns ...
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