Introduction

• each population will adapt differently and will eventually diverge genetically (evolve) from other populations

  • if divergence continues, speciation would occur (rare outcome)

• the rate of gene flow is a function of the closeness of the populations and the dispersal tendency of the species

Classification

Species

• Today distinguishes by differences in:

  • body function

  • biochemistry

  • behaviour

  • genetic makeup

• Classical Biological Concept Definition:

  • genetically distinctive populations of individuals isolated reproductively from all other populations

Alternative species concepts

• 27-30 concepts

• Ecological species

  • defined in terms of its ecological niche

• Morphological species

  • defined by morphology (structure)

• Genealogical species

  • defined as a set of organisms with a common and unique genetic history as shown by molecular patterns

Subspecies

• Def 1:

  • Taxonomic subdivision of a species

• Def 2:

  • A population of a particular region genetically distinguishable from other populations and capable of interbreeding with them

• Def 3:

  • A grouping of organisms that differ from other members of their species by color, size, or various morphological features

Cline

• A gradual and continual change in a character by a series of populations or throughout the range of a species

• Usually along a geographic or environmental gradient

  • Individuals at the two extremes differ

• Clinal Variation

  • 

• Clinal Variation in plastral markings of painted turtles

  • Western forms -- intricate

    • 

  • Hybrid -- intermediate

    • 

  • Midwestern/Midland -- single

    • 

• “Ring species”

  • Individuals that don’t interbreed but all stem from one population

    • 

    • Lungless salamander (Ensatina eschscholtzi)

Morphological Variation

• Latitudinal changes within a species

  • Changes in body weight; Bergman’s rule

    • Animals have a tendency to be larger in polar regions, medium in temperate climates, and smallest in tropical ones

    • DOES NOT ALWAYS APPLY TO REPTILES & AMPHIBIANS

  • Changes in body color

Biogeography

• 3 major factors influence geographic distributions of amphibians & reptiles

  1. Climate

     1. Amphibians have 3 factors in regards to climate

        1. Temperature

        2. Rainfall

        3. Periodicity

  2. Availability & access to resources

  3. Dispersal abilities

     1. Small fossorial amphibians & reptiles have poorer dispersal abilities

     2. Large aquatic animals tend to be better dispersers

Movements

Daily Movements

• Feeding

• Thermoregulation

• Predator avoidance

Seasonal Movements

• Generally more extensive but still generally considered to be <0.5 km

• Breeding

  • Amphibians generally go towards water

  • Reptiles generally go towards land

• Hibernation

  • Snakes searching for hibernacula to escape the cold

• Habitat Utilization

  • Largely associated with change in food availability or habitat quality

Dispersal

• Movement outward from home area; often implies colonization

• Important for maintaining gene flow in a population

• Infers some genetic exchange (if those dispersing individuals successfully reproduce)

• Undirected movement to locations unknown by the dispersing animals

• Costs & benefits

  • Benefits

    • May reduce intra-specific competition

    • Likely to come into contact with different individuals unrelated to you (minimizes inbreeding)

  • Costs

    • Resources could be lacking

    • Increased predation risk

Orientation & Navigation

• Piloting

  • Simplest form; ability to recognize landmarks

  • Possessed by all reptiles & amphibians

• Compass orientation

  • Sense of direction

  • Independent of local cues (i.e. basking/perching sites)

• True navigation

  • Ability to orient & move toward a location; an internal map

• Others

  • Visual orientation (polarized light)

  • Pineal organ (salamanders)

  • Parietal eye (dictates photoperiod)

  • Olfaction

  • Celestial (stars & celestial bodies)

Orientation in baby Loggerhead Turtles (Chelonia mydas)

• Visual cues

  • Uses stars & moon to help hatchlings find ocean

• Wave Orientation

  • Takes them out into the ocean

• Magnetic Orientation

Home Range

• 

• 

• Home range varies between the sexes

  • larger in males, smaller in females

  • male home range size 2x amount of female and is increasing

• Defense (Territoriality)

  • Usually very expensive, but where a required resource is insufficient for all individuals, defense may have evolutionary advantage

  • Types

    1. Territorial defense

       1. Relatively rare

       2. Mark territory with pheromones

       3. Accomplished through direct combat

    2. Site defense

       1. More common

       2. Defense of point resource

       3. Basking sites, food, nesting