Insect Phylogeny and Evolution. Determining Phylogenetic Relationships No engine, two wheels No engine, one wheel Gas engine, two wheels Diesel engine,

Insect Phylogeny and Evolution

Determining Phylogenetic Relationships

No engine, two wheels

No engine, one wheel

Gas engine, two wheels

Diesel engine, four wheels, solid box on back

Gas engine, four wheels, glassed box on back

Gas engine, four wheels, no box on back

Gas engine, four wheels, solid box on back

Determining Phylogenetic Relationships

No engine, two wheels

No engine, one wheel

Gas engine, two wheels

Diesel engine, four wheels, solid box on back

Gas engine, four wheels, glassed box on back

Gas engine, four wheels, no box on back

No engine Engine

Gas Diesel

4 wheels 2 wheels

Box No box

1 wheel2 wheels

Gas engine, four wheels, solid box on back

glass solid

bicy

cle

unic

ycle

SUV

van

sedan

mot

orcy

cletr

uck

Some ancestral vehicle (??)

Determining Phylogenetic Relationships

No engine Engine

Gas Diesel

4 wheels 2 wheels

Box No box

1 wheel2 wheels

glass solid

bicy

cle

unic

ycle

SUV

van

sedan

mot

orcy

cletr

uck

Some ancestral vehicle (??)

Species - 7

Genus - 6

Family - 5

Order - 4

Phylum - 2

A little bit about taxonomy, classification and phylogeny

Systematics - study of the diversity and relationships of organisms both now and in the past.

Phylogeny - The evolutionary development and history of a species or higher taxonomic grouping of organisms.

Taxonomy - classification, naming and description of taxa.

Methods of establishing phylogenies

Evolutionary systematics - use several fixed levels of a hierarchy, such as kingdom, phylum, class, order, and family.

Evolutionary systematicsPheneticsCladistics

Methods of establishing phylogenies

Phenetics (numerical taxonomy)

Evolutionary systematicsPheneticsCladistics

Robert R. Sokal

C.D. Michener

- based on taking lots of measurements on organisms & then using computer algorithms to assign relationships among them

Problems - ignored ancestral vs. derived characteristics

Methods of establishing phylogenies Evolutionary systematicsPheneticsCladistics

Cladistics - classifies species of organisms into hierarchical monophyletic groups (clades) - based on shared

derived characteristics (or characters)

Willi Hennige.g. Character #1 - present in species A, B, C

Character #2 - present in species A, B, but not C

Have 2 groups - A + B and C

Methods of establishing phylogenies Evolutionary systematicsPheneticsCladistics

Cladograms

Methods of establishing phylogenies Evolutionary systematicsPheneticsCladistics

EntognathaArchaeognatha

Zygentoma EphemeropteraOdonataPlecopteraEmbiodea ZorapteraDermapteraGrylloblattodea Mantophasmatodea

?

OrthopteraPhasmatodeaBlattariaIsoptera Mantodea Psocoptera PhthirapteraThysanopteraHemiptera

Coleoptera Rhaphidioptera MegalopteraNeuroptera HymenopteraMecoptera Siphonaptera Diptera StrepsipteraTrichoptera Lepidoptera

Methods of establishing phylogenies Evolutionary systematicsPheneticsCladistics

Some definitions

Apomorphy - derived state is a characteristic believed to arisen in a recent common ancestor or a recently evolved feature that appears only in a group of closely related species. The elytra of that all beetles have serve to separate them from all insects

Plesiomorphy -or ancestral character that is present at the base of the tree. For example, the presence of six legs (shared by all insects) can be hypothesized to have existed in some common insect ancestor.

Methods of establishing phylogenies Evolutionary systematicsPheneticsCladistics

Some more definitions

Monophyletic groups - contain ancestor and all descendant species

Paraphyletic groups - contain ancestor and some but not all descendant species

Polyphyletic groups - contain taxa from two or more different monophyletic groups

MONOPHYLETIC

PARTIAL CLASSIFICATION OF DIPTERA

PARAPHYLETIC

POLYPHYLETIC

Phylogeny of the Arthropoda

Onychophora

Tardigrada

Arachnidomorpha(≈Chelicerata)

Crustaceomorpha

Atelocerata

Marellomorpha †

These taxa are all subphyla of Arthropoda

Next slide

Annelid-like

ancestor

Arthropoda

Phylogeny of the Mandibulata

Crustacea

Chilopoda

Symphyla

Pauropoda

Diplopoda

Entognatha

Insecta

†

††

††

= terrestrial origin

Chelicerates (spiders, scorpions, mites etc.)

Mandibulata

Hexapoda

Atelocerata(possess trachea)

Non-Hexapod Mandibulates

Symphla Chilopoda - centipedes

Diplopoda- millipedes Pauropoda

Summary of features of non-hexapod mandibulates

Chilopoda 0.5 - 30 cm 15 - 177 15 - 177 3 pr

Pauropoda 0.05 - 0.2 cm 9-10 12 2 pr

Diplopoda < 5 cm < 200 <200 2 pr

Size # of pairs of legs # of segments # m.p.’s

Symphyla < 1.0 cm 14 14 3 pr

Hexapoda

Protura

Diplura

Collembola

Insecta

Archaeognatha

Thysanura

Pterygota

Entognatha

Relationships among Hexapoda

500 400 300 200 100 0

EntognathaArchaeognatha

Zygentoma EphemeropteraOdonataPlecopteraEmbiodea ZorapteraDermapteraGrylloblattodea Mantophasmatodea?

OrthopteraPhasmatodeaBlattariaIsoptera Mantodea Psocoptera PhthirapteraThysanopteraHemiptera

Coleoptera Rhaphidioptera MegalopteraNeuroptera HymenopteraMecoptera Siphonaptera Diptera StrepsipteraTrichoptera Lepidoptera

Silurian Devonian Carboniferous Permian Triassic Jurassic Cretaceous

Holometabola

Neoptera

Insecta

Pterygota

Apterygotes

Paleoptera

Hemimetabolous

Holometabolous

Hexapoda

500 400 300 200 100 0

EntognathaArchaeognatha

Zygentoma EphemeropteraOdonataPlecopteraEmbiodea ZorapteraDermapteraGrylloblattodea Mantophasmatodea?

OrthopteraPhasmatodeaBlattariaIsoptera Mantodea Psocoptera PhthirapteraThysanopteraHemiptera

Coleoptera Rhaphidioptera MegalopteraNeuroptera HymenopteraMecoptera Siphonaptera Diptera StrepsipteraTrichoptera Lepidoptera

Silurian Devonian Carboniferous Permian Triassic Jurassic cretaceous

Vascular plants Seed plants

Holometabola

Neoptera

Insecta

Pterygota

Steps in arthropod evolution

1. Common ancestor - legless annelid- undifferentiated body

1

2. Paired bilateral appendages- development of somites, antennal

segments, and simple eyes (like Onychophora)

3. Early arthropod - better developed eyes and jointed legs

2

4

3

4. Reduction in appendages- cephalization-modification of first appendages

into mouthparts- development of three tagmata

What about the Onychophora (“velvet worms” )?

Annelid ArthropodCharacteristics Characteristics

Peripatus

-worm-like body -segmented legs(during embryogenesis)

-paired nephridia -open circulatory system

- hemocoel- trachea- oral appendages

Evolution of the Insects

1. Appearance of primitive wingless insects2. Development of wings

3. Development of wing flexion mechanisms

4. Development of metamorphosis

(Carpenter - 1953)Four stages in insect evolution