HEXAPODS SUBPHYLUM HEXAPODA 2 WHY SO MANY SPECIES

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HEXAPODS(SUB-PHYLUM HEXAPODA)2) WHY SO MANY
SPECIES?
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WHY SO MANY ENDOPTERYGOTES?
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ENDOPTERYGOTES COMPLETE METAMORPHOSIS HAVE
LARVAE PUPA
larvae
eggs

MOTH
pupa
adult
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FIVE OUT OF MANY ANSWERS
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INSECTS ARE SUCCESSFULBECAUSE
(1) THEY ARE SMALL High surface area volume
ratio Experience world as fine-grained
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HIGH SURFACE AREA VOLUME RATIO

• Can jump from heights that would kill (e.g.)
  mammals

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HIGH SURFACE AREA VOLUME RATIO

• Can jump from heights that would kill mammals
• Can can jump to heights many times their body
  length

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HIGH SURFACE AREA VOLUME RATIO

• Can jump from heights that would kill mammals
• Can can jump to heights many times their body
  length
• Can carry many times their body weight

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HIGH SURFACE AREA VOLUME RATIO

• DRAWBACKS
• Rapid heat exchange

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HIGH SURFACE AREA VOLUME RATIO

• DRAWBACKS
• Rapid heat exchange
• Potentially devastating water loss in dry
  habitats

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EXPERIENCE WORLDAS FINE-GRAINED
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SMALL SIZE
ONE PROBLEM VULNERABLE TO WIDER RANGEOF
MORTALITY FACTORS e.g. more predators than larger
species
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SMALL SIZE
CENTRAL PROBLEM INSECTS ARE NOT UNUSUALLYSMALL
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INSECTS ARE SUCCESSFULBECAUSE
(2) HAVE PROTECTIVE CUTICLE
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INSECTS ARE SUCCESSFULBECAUSE
(3) HAVE BLOOD-BRAIN BARRIER
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INSECTS ARE SUCCESSFULBECAUSE
(4) CAN FLY
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INSECTS ARE SUCCESSFULBECAUSE
(4) CAN FLY
STRIKING THAT ONLY PTERYGOTES - MOST CAN FLY
ARE SPECIES-RICH
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FLIGHT
CANNOT BE SOLE REASON BIRDS BATS ARE NOT AS
SPECIES-RICH
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INSECTS ARE SUCCESSFULBECAUSE
(5) REPRODUCE FAST
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INSECTS ARE SUCCESSFULBECAUSE
(5) REPRODUCE FAST Many rear 50 young per
month
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INSECTS ARE SUCCESSFULBECAUSE
(5) REPRODUCE FAST Many rear 50 young per
month After 18 months their descendents
2.9 x 1025
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HIGH REPRODUCTIVE RATE
CENTRAL PROBLEM EXPECTED OF r-SELECTED SPECIES
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Peter Mayhew (2007) Perhaps McGavin is
taking wrong perspective.Is it long
evolutionary history of insects combined with low
extinction rates?
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WHY SO MANY ENDOPTERYGOTES?
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IS PUPATION A KEY INVENTION?
 

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Allows larvae adults to completely avoid
competition Species can occupy two niches
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WHY ARE THREE ORDERSSO SPECIES-RICH?
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Beetles (Coleoptera) All over armour?
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Beetles (Coleoptera) All over armour? Moths
(Lepidoptera) Caterpillar herbivory?
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Beetles (Coleoptera) All over armour? Moths
(Lepidoptera) Caterpillar herbivory? Adult
nectarivory?
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Beetles (Coleoptera) All over armour? Moths
(Lepidoptera) Caterpillar herbivory? Adult
nectarivory? Bees etc. (Hymenoptera) Nectarivory?
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Beetles (Coleoptera) All over armour? Moths
(Lepidoptera) Caterpillar herbivory? Adult
nectarivory? Bees etc. (Hymenoptera) Nectarivory?
Sawfly larva herbivory?
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Beetles (Coleoptera) All over armour? Moths
(Lepidoptera) Caterpillar herbivory? Adult
nectarivory? Bees etc. (Hymenoptera) Nectarivory?
Sawfly larva herbivory? Parasitoids?
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ABOUT 10 OF ANIMALS ARE PARASITOID WASPS