Reptile and Amphibian communities

Community ecology is the study of the interactions among groups of species coexisting within a region
1. Helps explain observed patterns of distribution
2. Traditionally focused on current interactions
3. Acknowledges the influence of evolutionary history
4. Patterns of distribution & association at a global scale
  1. Indentifying, describing and explaining
    1. general patterns that underlie the structure of communities
5. Patterns of distribution & association at a regional scale ; Anolis lizards
  1. 400 spp
  2. Greater and Lesser Antilles
    1. Not a product of island size
    2. Lesser; Max. 2 spp/island
  3. Greater Antillean Anolis; ecomorphs
    1. Crown-giant
      1. Anolis cuvieri
        Jamaica
      2. Anolis equestris
        Cuba
      3. Green, high canopy perch, massive head, often casqued
      4. >100mm
    2. Twig-drawf
      1. Anolis valencienni
        Jamaica
      2. Anolis occultus
        Puerto Rico
      3. Grey, outer canopy/vines perch, long head, short body & legs
      4. <50mm
    3. Trunk-crown
      1. >70mm
      2. Green, canopy/trunk perch, long body short legs
      3. Anolis grahami
        Jamaica
      4. Anolis allisoni
        Cuba
    4. Trunk
      1. <50mm
      2. Varied colour, central trunk perch, short head & body
        Hispaniola & Cuba
    5. Trunk-ground
      1. >60mm
      2. Brown, lower trunk perch, large head, short stocky body
      3. Anolis cybotes
        Hispaniola
    6. Grass bush
      1. <50mm
      2. White stripe, grass/bush perch, long head & tail, slender body
      3. Anolis alutaceus
        Cuba
    7. Anolis oddities
      1. Not all fit into ecomorphs
      2. Cuban false Chameleon
      3. Cuban stream anole
    8. Niche separation on 3 axes
      1. Perch axis
      2. Size axis
      3. Climate axis
    9. A. sagrei
      1. Cuba
      2. Sympatric with 12 other spp
        Results in NARROWING of resource use
        If species removed; broadening of resuouce use
        ECOLOGICAL RELEASE
  4. Lesser Antilles
    1. Body size difference between spp on single island
      1. HUCTHINSON'S RULE
    2. Bosy size of solitary spp is intermediate
    3. Separated also on perch height or microclimate axis
      1. Perch height = bimaculatus grp
      2. Microclimate = roquet grp
    4. St. Martin island
      1. Only L.S. where small and medium- sized spp coexist
        Smaller
        A. pogus
        Unusally patchy and restricted range
        common in mesic areas
        Experimental manipulation shows negative effect of A. pogus on A. gingivinus
        Medium
        A. gingivinus
      2. St Eustatius
        A. schwartzi
        A. bimaculatus
        Size and perch height difference exists
        No effects were seen of either spp on the other
        Competition for food is more intense for ecologically similar than dissimilar spp
SIgnificance of herps in communities
1. High ASSIMILATION
  1. High CONVERSION
2. Small body size
  1. Many with adult mass 10x small than smallest bird/mammales
  2. Allowing niche occupation
3. HOMEOTHERMS
  1. Assimilation hish, low production to consumption ratio
4. POILKILOTHERMS
  1. Assimilation equal to production
Causal mechanisms
1. Competition
  1. Exploitive/interference
  2. Niche separation/resource partitioning
  3. E.g desert lizards in different contients
    1. Aus; Moloch horridus
    2. S. Africa; Armadillo girdled lizard
    3. USA; Horned toad
2. Ecomorphs
  1. A group of several species with the same structural habitat/niche, similar in morphology but not necessarily phyletically
3. Habitat complexity
  1. Increased oppotunity for niche separation
  2. Patchiness also important
  3. Kopjes
    1. Protection
      1. Grass fires
      2. More water in the ground around them
    2. Pancake tortoise
      1. Malacochersus tonieri
      2. Isolated colonies
    3. Mwanza flat-headed lizard
      1. Agama mwanzae
      2. Basking
4. Predation (Parasitism)
  1. Can influence competition, behaviour & life history
  2. Avoidance of parasitism is genetic
    1. Malaria
      1. A. pogus, A. gingivinus
        More resistant
        Less resistant
        Only co-exist when A. gingivinus is malaria infected
  3. Co-evolution between parasite and host affects outcome
5. Physiological tolerances
  1. May change ONTOGENETICALLY, seasonally, with reproductive status
  2. Puerto Rican anoles
    1. 2 related, similar trunk-ground spp
      1. Differ in microclimate axis
      2. Hurricane Hugo
        1989
      3. A. cristatellus
        Limited by own lower heat tolerance
      4. A, gundlachi
        retreated to lower, shadier perch
6. Historical
  1. Biogeography
  2. Climatic history
    1. Pleistocene glatiation
  3. Phylogenetic effects
  4. Evolutionary constraints
    1. Unequal probability of trait gain and loss
  5. Neutral models
7. Environmental stochasticity/predictability
  1. E.g larval anuran assemblages
  2. Predation susceptability & competitive ability changes with growth
    1. Resources change rapidly and easily manipulated
Summary
1. Different communities doffer in the importance of various structuring forces
2. A the community level, manipulative experiments need to
  1. Involve large number of spp
  2. extend over several generations
  3. Cover large spatial areas relative to the range of the studied animals
  4. Herps suit these requirments very well & this accounts for their influence in community ecology

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Reptile and Amphibian communities

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