WE ARE YELLOWKNIFE

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WE ARE- YELLOWKNIFE

• CHRISTOS
• DAN
• JENNIFER
• MASSA
• TJA

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YELLOW KNIFE PRESENTS

• COEVOLUTION AND COMPETITION

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Key Terms of Stickleback Paper

• 1.  Littoral Zone- the region of the shore of a
  lake or sea or ocean .
• 2.  ANOVA- Analysis of  Variance-an important
  tool to understand the statistical differences
  between the averages or the "means" of two
  different populations.  In an ANOVA analysis,
  the relationship between measurements of the mean
  and the variance or "random error" of each group
  provides the information needed to determine if
  the difference between the two is significant.
• 3.  Thermocline- a large body of water that
  sharply separates regions differing in
  temperature, makes the temperature gradient
  across the layer abrupt.
• 4. Protuberance- something that protrudes, bulge,
  knob or swelling.
• 5. Adaptive Radiation - Diversification of a
  species or single ancestral type into several
  forms that are each adaptively specialized to a
  specific environmental niche.
• 6.  Gill Rakers- used to sieve small
  particles(food).

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Natural History of Sticklebacks

• Canadian coast
• 13,000 years ago
• Sticklebacks invaded lades from the sea after the
  last glaciation
• Occasionally 2 forms in lakes, presumably from
  different invasions (Benthics and Limnetics)
• Open water and bottom form

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Predictions by the author

• Feeding traits
• Fitness trade-offs
• Feeding efficiency

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Methods

• 36 enclosures (18 with each habitat)
• Littoral zone Diets dominated by insect larvae
• Open water Planktonic prey
• Diet proportions are equal within each habitat
• Selected smaller sized fish to ensure that
  substantial growth was possible
• Fished weighed before release and after they were
  recaptured (Table 1)
• Length measurement taken before and after

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Results

• Feeding performance was predicted from growth
  rates
• Used growth rates to determine fitness
• In both years Benthics performed better in the
  littoral zone and Limnetics performed better in
  the open water - Figure 3
• Hybrids have an intermediate phenotype and have a
  decreased performance - due to competition
• Growth rate declined when each fish was in each
  others habitat

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Conclusion(s)

• Interspecific competition s causing coevolution
  in Sticklebacks!
• Morphology ? Feeding Performance ? Fitness (via
  growth rate)

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• Populations occurring alone in lakes are
  intermediate between Limnetics and Benthics in
  morphology and habitat
• When Limnetics and Benthics co-exist the two
  species differ in size and shape
• Morphological differences are associated with
  trade-offs in efficiencies of food exploitation
  between habitats
• Morphological divergence represents character
  displacement, which should reduce interspecific
  competition
• The selection for efficient use of alternative
  food resources is the cause of adaptive radiation
  in Sticklebacks

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What should you know about COMPETITION and
COEVOLUTION?
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• Coevolution leads to an enhancement of the
  differences between competing species so as to
  bring about a partitioning of the resources and a
  consequent reduction of competition.
• The removal of interspecific competitors leads to
  an expansion of the variety of resources used by
  the remaining species.

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QUESTION

• What role does divergent selection pressures
  play in speciation?

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Question 2

• Figure 3 shows trade-offs. Should the hybrid be
  on the line representing intermediate forms? Why
  or why not?

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Now Onto the Crossbills and Lodgepole Pines!!!!

• Christos
• Dan
• Massa

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Key Terms of Crossbill Paper

• 1. Divergent Selection- natural selection pushing
  a trait in different directions, such as two
  populations of birds- one increasing bill size
  and the other decreasing bill size.,2.
  Directional Selection- natural selection pushing
  a trait of a population in one direction, such as
  increasing bill size.3. Antagonistic Selection-
  when two pressures are working in opposite
  directions on a single trait.4. Multifarious-
  having great diversity or variety.5. Middens- a
  depositing site.6. Serotinous Cones- cones that
  require heat to open and release seeds.7.
  Physiognomy- aspect and character of an inanimate
  or abstract entity.
• 8. Coevolution Hot Spots- refers to areas where
  squirrels are absent, therefore Crossbills
  coevolve with Lodepole Pines.

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Natural History

• Red Squirrels
• ( Tamiasciurus hudsonicus

• Solitary and active during the day
• Harvest cones and cache them in middens
• Foraging for food takes place primarily in early
  morning and late afternoon

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Red crossbills (Loxia curvirostra)

• Breed when food is abundant
• Can be nomadic depending on the food
  availability
• Show much geographic variation in body size,
  bill size and shape but not in color
• Direct relation between their morphology,
  ecology and their food resources.

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Lodgepole Pine(Pinus contorta var. latifolia)

• Found mainly in western Canada and the
  northwestern United States
• Short needles in bundles of two
• Between 20 to 80 feet tall
• Mature cones are 3/4 to 2 inches long, hard,
  dense, and are attached very firmly to the stem.
  Can remain closed for years.
• Most cones are serotinous which need heat or
  direct sunlight to open.

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Squirrels and Pines

• Tamiasciurus as a Preemptive Competitor
• Tamiasciurus as Selective Agents on Cone
  Structure
• Geographic Variation in Lodgepole Pinecone
  Structure

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Crossbills and Pines

• Cone Evolution in Response to Crossbills
• Coevolution Leads to Divergent Selection on
  Crossbills
• Geographic Mosaic
• Thompsons Three-part Coevolutionary Hypothesis

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Question

• Is there COEVOLUTION between the squirrels and
  pines?

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With both papers in perspective

• Did the authors adequately show that competition
  was present and the reason for coevolution? If
  so, what did they do to show this? If not, what
  more do we need?

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Crossbills and Sticklebacks

• What makes the systems described in the papers
  good to look at?

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References

• Benkman, C. W. 1993. Adaptation to single
  resources and the evolution of crossbill (Loxia)
  diversity. Ecological monographs. 63305-325.
• Benkman, C. W., and R. E. Miller. 1996.
  Morphological evolution in response to
  fluctuating selection. Evolution. 502499-2504.
• Schluter, D. 1995. Adaptive radiation in
  sticklebacks trade-offs in feeding performance
  and growth. Ecology. 7682-90