Great  use  of  Discussion  Board  to  sort  out  course  difficul3es!  

This  week  the  even  numbered  groups  will  have  their  labs!      But  the  odd  numbered  groups  need  to  hand  in  their  assignment  via  Blackboard!    

Model  organisms  in  Ecology  and  Evolu3on  

Drosophila  melanogaster  (fruit  fly)   Arabidopsis  thaliana  (Mouse-­‐ear  cress)  

Week  3:  Introduc3on  to  interac3ons:  lecture  outline  

v  Defini3ons:  interspecific/intraspecific    

v  Posi3ve  (+)  and  nega3ve  (-­‐)  interac3ons  

v  Compe33ve  exclusion  

v  Ecological  niche:  fundamental  and  realized  

v  Preda3on  

v  An3predator  adapta3ons  including  cryp3c  coloura3on,  aposema3c  coloura3on  and  mimicry  

v  Herbivory  

Contrast  inter-­‐  and  intraspecific  interac3ons  

Tip:  How  to  remember  the  difference:  Think  ‘interna3onal’  means  more  than  one  na3on…so  ‘interspecific  interac3ons  means  interac3ons  between  two  or  more  species  

Interspecific  (Burmese  python  with  White-­‐tailed  deer  prey)  Intraspecific  (figh3ng  Am.  Robins)  

Characterizing  interac3ons  (examples)  

•  Preda3on:  +/-­‐  Means  +  effect  on  survival  and  reproduc3on  of  predator,  -­‐  effect  on  survival  and  reproduc3on  on  prey.  

•  Mutualism:  +/+.  Posi3ve  for  both  species  that  interact  (or  individuals  within  a  species)  

•  Reminder  (survival  +  reproduc3on  =  fitness)  

 

Compe33on:  Interspecific  (-­‐/-­‐)  •  Two  forms:  interference  and  exploita:ve  •  Interference  compe33on  is  direct  physical  compe33on  for  resources  between  individuals.  

•  Exploita3ve  compe33on  is  indirect,  when  one  species  reduces  resources  for  the  other  (e.g.,  shared  resources)  

Compe33ve  Exclusion  

•  Gause  (1934)  first  proposed  this  concept:  

Gause’s  results  suggest  that:    

α1,2    =  α2,1  =  1      

OR  

α1,2    ≠  α2,1  ≠  1    

?      

Compe33ve  Exclusion  Principle  

Two  species  compe3ng  for  the  same  limi3ng  resources  cannot  coexist  permanently  in  the  

same  place.    

(even  a  slight  reproduc3ve  advantage  through  more  efficient  feeding,  

reproduc3on,  etc.  will  eventually  lead  to  local  elimina3on  of  the  inferior  compe3tor)  

Prac3cally:  

•  Because  species  have  their  own  ecological  niche,  it  is  rare  to  see  compe33ve  exclusion  in  the  wild  (at  least  between  two  co-­‐exis3ng  na3ve  species)  AND  the  only  way  really  to  test  it  is  through  a  removal  experiment.  

 

What  IS  a  niche?  

•  “n-­‐dimensional  hyperspace”  (Hutchinson  1957)  

Black  Fly  Larvae  

Basically…where  an  organism  lives…  

Figure 54.3

Chthamalus Balanus

EXPERIMENT

Balanus realized niche

Chthamalus realized niche

High tide

Low tide

High tide

Chthamalus fundamental niche

Low tide Ocean

RESULTS

Ocean

Connell  1961  

Aker  removal  of  Balanus.      

Figure 54.2 A. distichus perches on fence posts and other sunny surfaces.

A. insolitus usually perches on shady branches.

A. ricordii

A. aliniger A. insolitus

A. distichus A. christophei

A. cybotes A. etheridgei

Classic  example  of  niche  par33oning  In  Dominican  Republic  Anolis  lizards    Diet  (or  one  dimension  of  their  niche)  is  broadly  similar  (e.g.,  insects  and  other  arthropods)!    

BUT…rejec3on  of  hypothesis  that  compe33on  explains  distribu3on  is  

difficult!  The    ‘Ghost  of  Compe::on  Past’  may  have  sorted  out  of  differences  in  evolu:onary  :me  to  AVOID  compe::on.    

Preda3on  (+/-­‐)  

Some  features  of  preda3on  Predators  have  acute  senses  that  enable  them  to  find  and  iden3fy  prey.  Ambush  predators  are  disguised,  pursuit  predators  fast  and  agile.                    Prey  have  similarly  acute  senses  and  special  adapta3ons  to  help  them  avoid  being  eaten.                  Through  natural  selec3on,  there  is  an  ‘arms  race’  between  predators  and  prey.                

Some  other  terms  some3mes  used  to  categorize  preda3on:  

Par3al  preda3on:  E.g.,  A  bird  lays  14  eggs,  only  9  are  eaten.      Micro-­‐preda3on:  E.g.,  A  very  small  organism  (predator)  eats  part  of  a  bigger  organism  (prey)   Sea  

squirts  

4.3  mm  

Osman  et  al.  1992.  

Whereas  preda:on  accounts  for  MOST  of  the  mortality  in  vertebrates  (e.g,  frogs,  birds,  rep3les,  mammals)  

   And  natural  selec3on  favours  those  

who  survive  (and  subsequently  reproduce!)    There  are  many  an:-­‐predator  adapta:ons.  

(a) Cryptic coloration (b) Aposematic coloration

Canyon tree frog Poison dart frog

(c) Batesian mimicry: A harmless species mimics a harmful one. (d) Müllerian mimicry: Two unpalatable species mimic each other.

Hawkmoth larva Cuckoo bee

Yellow jacket

Green parrot snake

Categoriza3on  of  some  an3-­‐predator  adapta3ons  (defensive  colora3ons):  

Includes  ‘mechanical’  and  ‘chemical’  defenses  Figure 54.5

Mimicry  is  also  used  by  some  predators  

Alligator  Snapping  Turtle  (Macrochelys  temminckii)  

Figure 54.6  

Herbivory  (+/-­‐):  the  term  used  when  an  organism  eats  part  or  all  of  a  plant  or  alga.    

West Indies manatee (Trichechus manatus)  

Specific  bill  adapta3ons  to  herbivory  

Canada  Geese    (Branta  canadensis),  with  a  more  ‘delicate’  bill,  graze  like  cows:            

Snow  Goose  (Chen  caerulescens),  with  their  more  robust  bill,    graze  and  grub    (pull  shoots  right  out  of  ground)  

Consequences  for  overpopula3on  of  each  differ  

Snow  Goose  damage  

Canada  Goose  damage:  not  as  severe  

Other  adapta3ons  for  herbivory  

•  Special  sensory  organs,  specialized  diges3ve  systems  and  teeth.    

“An3-­‐herbivory”  adapta3ons  

•  Include  secondary  compounds/metabolites:  broad  name  for  chemicals  that  protect  plants  against  herbivory  (among  other  poten3al  func3ons)  

Structural  protec3on:  Without  herbivores:  Galapagos  Opun3a  (Prickly  Pear  cactus):  shrubby,  bigger  fruits,  fewer  soker  spines  

With  land  iguanas  and  Galapagos  tortoises  

Tall  Opun3a  ‘forest’  

Varying  defini3ons  of  ‘symbiosis’  

•  Either  includes  +/-­‐  or  only  includes  mutualism  which  is  +/+!  

•  Your  textbook  uses  broader  defini3on(+/-­‐  and  +/+)  to  include  any  rela3onship  between  2    or  >  2  species  where  they  live  in  direct  and  in:mate  contact  with  each  other.    

Parasi3sm  •  Check  out  Youtube  video:  search  for  ‘Bot  fly:  Watch  the  one  with  >  8  million  views!  

Clearly  NOT  +/+!!  

Common  endoparasites:  

Spiny-­‐headed  worms  

Roundworms  

Tapeworms  

Figure 54.7

(a) Acacia tree and ants (genus Pseudomyrmex)

(b) Area cleared by ants at the base of an acacia tree

Classic  example  of  mutualism:    Ants  are  aggressive  and  s3nging.  Ants  feed  on  nectar  produced  by  the  tree  and  on  swellings  at  3ps  of  leaflets.    Trees  benefit  because  ants  asack  anything  that  touches  tree,  remove  fungal  spores,  small  herbivores  and  debris.    

“plant-­‐ants”  

“ant-­‐plants”  

Assumed  mutualism:  nice  adap3ve  story  

Photo  by  Gavin  Emmons  

The magnitude and direction of change in mean total tick load (±SE) for Control and experimental oxen for each replicated experiment (Mann-Whitney test throughout).

Weeks P Behavioral Ecology 2000;11:154-160

International Society for Behavioral Ecology

The mean number (±SE) of individual wounds per animal in all three treatments.

Weeks P Behavioral Ecology 2000;11:154-160 International Society for Behavioral Ecology

The mean changes (±SE) in earwax scores for control and experimental for each treatment (Mann-Whitney test throughout).

International Society for Behavioral Ecology

So  how  would  the  interac3on  between  oxpecker  and  casle  be  

categorized?  

Commensalism:  +/0:  When  the  water  buffalo  move  they  scare  up  insects  which  are  then  discovered  and  eaten  by  the  casle  egrets.  No  cost  to  waterbuffalo.    

Figure 54.8  

Figure 54.9

(a) Salt marsh with Juncus (foreground) (b) With Juncus Without Juncus

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Facilita3on  (+/+)  or  (0/+)  

Black  rush  (Juncus  gerardi)    facilitates  in  at  least  three  ways:  (1)  makes  the  soil  more  hospitable  for  other  species  (2)  helps  prevent  salt  buildup  by  shading  soil  surface,  reducing  evapora3on,  (3)  prevents  soil  from  becoming  oxygen  depleted  as  it  transports  oxygen  to  its  belowground  3ssues.  

Pollina3on  studies  oken  include  studies  of  facilita:on  and  are  

important!  •  Are  pollinators  limi3ng?  •  We  know  that  pollinators  are  cri3cal  for  food  crops  but  can  natural  pollinators  augment  the  role  of  honey  bees?    

Experimental  silviculture  (=logging)  experiment  Algonquin  Park  

Purpose  was  to  promote  growth  of  shade  intolerant  trees.  Unexpected    response  was  increase  in  wild  raspberry!  

Facilita3on  of  pollina3on  in  logging  gaps  in  Algonquin  Park:  Is  it  occurring?  

Increased  bee  buzzing  around  abundant  raspberries  MAY  increase  the  local  pollinator  popula3on  which  will  then  inadvertently  help  the  pollina:on  of  other  woodland  plants.  

Clintonia  borealis  

Claytonia  virginica  

Measuring  biodiversity!  

•  Various  measures:  

•  The  simplest  (AND  most  understandable)  is  ‘species  richness’  

•  How?  Count  the  species  (at  least  those  that  you  can  iden3fy!)  

Figure 54.10

Community 1 A: 25% B: 25% C: 25% D: 25%

Community 2 A: 80% B: 5% C: 5% D: 10%

A B C D

‘Species  richness’  alone  does  not  take  into  account  varying  abundances  of  species’  

There  are  a  variety  of  measures  that  weight  different  species  differently  

1. Rela3ve  abundance:        

   

Very  typical  pasern:  many  rare,  few  common  species  

Species  diversity  measures:  most  common  

2.  Shannon-­‐Weiner  diversity  index  (H  or  H’)      

H  =  -­‐(pA*ln  pA  +  pB*ln  pB  +  pC*ln  pC  +……..)    Where  A,  B,  C  …  are  the  species  in  the  community,  p  is  the  rela3ve  abundance  of  each  species  and  ln  is  the  natural  logarithm.        

Figure 54.10

Community 1 A: 25% B: 25% C: 25% D: 25%

Community 2 A: 80% B: 5% C: 5% D: 10%

A B C D

Example  forests:  which  do  you  think  is  more  diverse?  

Sample  calcula3ons  of  H  

Forest  1  (with  equal  propor3ons  of  all  4  species  of  tree):      H  =  -­‐4  (0.25  *  ln  0.25)  =    1.39        Forest  2  (with  unequal  propor3ons  of  all  4  species  of  tree)    H  =  [0.8*  ln  0.8  +  2  (0.05*  ln  0.05)  +  0.1  *  ln  0.1]  =  0.71  

Therefore,  Forest  1  is  more  diverse.  

H  =  -­‐(pA*ln  pA  +  pB*ln  pB  +  pC*ln  pC  +……..)  

What  does  H  mean?  

Higher  numbers  mean  habitats  with  MORE  SPECIES  and  MORE  EVEN  DISTRIBUTION  of  species  (because  rare  species  do  not  contribute  much  to  the  func3oning  of  the  ecosystem)      (comes  from  informa3on  theory;  early  computer  science).    

Figure 54.11

Soil pH 8 7 6 5 4 3

2.2

2.4

2.6

2.8

3.0

3.2

3.4

9

Shan

non

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(H)

3.6

Microbial  diversity  of  soils  in  North  and  South  America  as  determined  by  RFLP’s  of  RNA:      What  is  main  determinant  of  species  diversity  in  microbial  communi3es?  Does  it  increase  linearly?  

What  else  affects  biodiversity?  

•  Energy  •  Water  •  Disturbance  •  Invasive  species  •  Preda3on  •  Succession  •  Biogeographic  factors  (the  stuff  of  Biogeography!)  

Energy  (+)  can  limit  the  number  of  species  and  the  food  chain  length  

Experiment:  Added  and  subtracted  leaf  liser  to  tree  hole  communi3es  in  communi3es    

Spiny-­‐tailed  skink  

More  moisture  (+)  on  slope  means  more  invertebrates  

From:Seagle  and  Sturtevant  2005,  Ecology    

Chose  dry  (up  slope)  and  wet  (down  slope)  sites  and  measured  soil  moisture  and  invertebrates.  

Rela3ve  soil  moisture  

Disturbance  (+)    

Invasive  species  (-­‐)  

•  Take  a  picture  of  the  campus  buckthorn  area.    

Predation (+) EXPERIMENT

RESULTS

With Pisaster (control)

Without Pisaster (experimental)

Year ’73 ’72 ’71 ’70 ’69 ’68 ’67 ’66 ’65 ’64 1963

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Inter3dal  sites  in  Washington  state  (Paine  1974)  

Fireweed stage

Alaska

1760

Glacier Bay

1860

1907 1941

Dryas stage

Alder stage

1 2

3

0 5 10 15 Kilometers

Ecological Succession (= effect of time): Defined as the sequence of community and ecosystem changes after a disturbance. Usually older stages have FEWER species.    

Area (hectares; log scale)

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0.1 1 10 100 103 104 105 106 107 108 109 1010 1

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Figure 54.26 Biogeography  (Variable  effects  on  biodiversity:  one  factor  is  area  of  habitat)  

Does  biodiversity  maser?    Humans  have  a  homogenizing  influence  on  biodiversity?  

Uncommon Native woodland songbirds

Does  biodiversity  maser?  

•  Diverse  communi3es  are  more  stable  AND  more  produc3ve!  (Much  more  on  that  in  BIOL  2260H  and  BIOL  3380H)  

Guest  Ecologists  NEXT  WEEK!  

TUESDAY!  

THURSDAY!