University of Michigan Biological Station

Biology 442 - Biology of Insects

Lecture Notes - Phylogeny and Diversity

1. Systematics - what is it?
   1. Process of identification, classification, naming and showing relationships of organisms - insects mostly in the first 3 stages.
   2. What are major taxonomic categories?
   3. Deciding on groups - How do we define a taxonomic category?
      1. Types of reconstruction.
         1. Phenetics. - objectivity and overall similarity
         2. Cladistics. - branching
         3. Phylogenetics. - uses best of several methods
      2. Term definition.
         1. Branching (speciation).
         2. Distance/divergence.
         3. Monophyletic, Polyphyletic, Paraphyletic.
         4. (Syn)apomorphy, (Sym)pleisomorphy.
         5. Homology, Analogy. E.g. where do wings come from?
         6. Homoplasy - reversal, convergence, parallelism. E.g. raptorial front legs of Mantids and mantisflies
2. Phylogeny.
   1. Origin of Arthropods.
      1. Characters of Arthropods.
         1. Segmented body (usually 2 or 3).
         2. Paired, segmented appendages.
         3. Bilateral symmetry.
         4. Chitinous exoskeleton.
         5. Tubular alimentary canal.
         6. Open circulatory system.
         7. Brain w/ paired, ventral nerve cords.
         8. Striated skeletal muscle.
         9. Excretory tubes.
         10. Respiration by gills, tracheae, spiracles.
         11. Separate sexes.
      2. Closely related phyla.
         1. Annelida - worms.
            1. No segmented appendages.
            2. No chitinous exoskeleton.
            3. No tracheal system.
            4. Closed circulatory system.
            5. Skeletal muscles not striated.
            6. Excretion by nephridia.
         2. Onychophora - Peripatus - only S. Hemisphere.
            1. Body segments indistinct.
            2. Segmented antennae only.
            3. Chitinous exoskeleton.
            4. Tracheal system.
            5. Open circulatory system.
            6. Skeletal muscles not striated.
            7. Excretion by nephridia.
   2. Origin of Insects. 4 main groups of Arthropods (see handouts).
      1. Trilobita - extinct.
      2. Chelicerata - horseshoe crabs, scorpions, spiders, mites, ticks, daddy long legs, pseudoscorpions.
      3. Crustacea - copepods, ostracods, barnacles, amphipods, isopods, lobsters, crayfish, crabs, shrimps.
      4. Atelocerata or Uniramia (unbranched appendages) - millipedes, centipedes, paurapods, symphylans, insects.
   3. Phylogeny of insect orders (see handouts).
      1. Extinct orders.
      2. Time scale of branching events.
      3. Major branching events.
      4. Major inovations during evolution.
         1. internal mouthparts/external mouthparts
         2. wingless/winged - origin of wings
         3. flexion of wings
         4. complete development - addition of pupa and internal development of wings
3. Diversity.
   1. Numbers of species in different places (table from book).
   2. Areas of greatest diversity.
      1. Tropical areas.
      2. Lower altitude (topography).
      3. Peninsular lows.
      4. Mid-successional sites.
   3. Reasons for diversity.
      1. Global reasons.
         1. Time.
         2. Spatial heterogeneity (macro - within and between habitat; micro - plant species, foliage height).
         3. Stability of habitat (seasonality).
         4. Size of habitat.
      2. Local reasons.
         1. Competition.
         2. Predation.
   4. Measurement of species diversity.
      1. Species richness = # of spp.
      2. Heterogeneity - includes # of individuals of each species.
      3. Shannon-Wiener index (best when total # of species is known and have large sample).
      4. Simpson's index (gives little weight to rare spp. and more to common - ranges from 0 to 1 - 1/s).

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