Insect Phylogeny and Evolution

Determining Phylogenetic Relationships No engine, two wheels Gas engine, two wheels Gas engine, four wheels, no box on back Diesel engine, four wheels, solid box on back Gas engine, four wheels, glassed box on back No engine, one wheel Gas engine, four wheels, solid box on back

Determining Phylogenetic Relationships bicycle unicycle motorcycle SUV sedan van truck No engine, two wheels Gas engine, two wheels glass solid Gas engine, four wheels, no box on back Box No box Diesel engine, four wheels, solid box on back 4 wheels 2 wheels 2 wheels 1 wheel Gas engine, four wheels, glassed box on back Gas Diesel No engine, one wheel No engine Engine Gas engine, four wheels, solid box on back Some ancestral vehicle (??)

Determining Phylogenetic Relationships motorcycle bicycle unicycle SUV sedan van truck Species - 7 glass solid Genus - 6 Family - 5 Box No box Order - 4 Phylum - 2 4 wheels 2 wheels 2 wheels 1 wheel Gas Diesel No engine Engine Some ancestral vehicle (??)

A little bit about taxonomy, classification and phylogeny Systematics - study of the diversity and relationships of organisms both now and in the past. Taxonomy - classification, naming and description of taxa. Phylogeny - The evolutionary development and history of a species or higher taxonomic grouping of organisms.

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

Methods of establishing phylogenies Evolutionary systematics Phenetics Cladistics Phenetics (numerical taxonomy) - based on taking lots of measurements on organisms & then using computer algorithms to assign relationships among them Robert R. Sokal Problems - ignored ancestral vs. derived characteristics C.D. Michener

Methods of establishing phylogenies Evolutionary systematics Phenetics Cladistics Cladistics - classifies species of organisms into hierarchical monophyletic groups (clades) - based on shared derived characteristics (or characters) e.g. Character #1 - present in species A, B, C Willi Hennig Character #2 - present in species A, B, but not C  Have 2 groups - A + B and C

Methods of establishing phylogenies Evolutionary systematics Phenetics Cladistics Some definitions 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. 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

Methods of establishing phylogenies Evolutionary systematics Phenetics Cladistics 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

PARTIAL CLASSIFICATION OF DIPTERA MONOPHYLETIC PARAPHYLETIC POLYPHYLETIC

Phylogeny of the Arthropoda Onychophora Annelid-like ancestor Tardigrada Marellomorpha † Arachnidomorpha(≈Chelicerata) Crustaceomorpha Next slide Arthropoda Atelocerata These taxa are all subphyla of Arthropoda

† † † † † Phylogeny of the Mandibulata Chelicerates (spiders, scorpions, mites etc.) † = terrestrial origin † † Crustacea Chilopoda Symphyla Pauropoda Mandibulata Diplopoda † Atelocerata (possess trachea) † Entognatha Hexapoda Insecta

Non-Hexapod Mandibulates Chilopoda - centipedes Symphla Pauropoda Diplopoda- millipedes

Summary of features of non-hexapod mandibulates Size # of pairs of legs # of segments # m.p.’s Chilopoda 0.5 - 30 cm 15 - 177 15 - 177 3 pr Symphyla < 1.0 cm 14 14 3 pr Pauropoda 0.05 - 0.2 cm 9-10 12 2 pr Diplopoda < 5 cm < 200 <200 2 pr

Relationships among Hexapoda Collembola Entognatha Protura Diplura Hexapoda Archaeognatha Insecta Thysanura Pterygota

Hexapoda Insecta Pterygota Neoptera Holometabola Apterygotes 500 400 300 200 100 0 Silurian Devonian Carboniferous Permian Triassic Jurassic Cretaceous Entognatha Archaeognatha Hexapoda Zygentoma Ephemeroptera Insecta Odonata Plecoptera Embiodea Pterygota Zoraptera Dermaptera Grylloblattodea ? Mantophasmatodea Orthoptera Phasmatodea Blattaria Isoptera Mantodea Neoptera Psocoptera Phthiraptera Thysanoptera Hemiptera Coleoptera Rhaphidioptera Megaloptera Neuroptera Hymenoptera Holometabola Mecoptera Siphonaptera Diptera Apterygotes Strepsiptera Trichoptera Paleoptera Lepidoptera Hemimetabolous Holometabolous

Vascular plants Seed plants 500 400 300 200 100 0 Silurian Devonian Carboniferous Permian Triassic Jurassic cretaceous Entognatha Archaeognatha Zygentoma Ephemeroptera Insecta Odonata Plecoptera Embiodea Pterygota Zoraptera Dermaptera Grylloblattodea ? Mantophasmatodea Orthoptera Phasmatodea Blattaria Isoptera Mantodea Neoptera Psocoptera Phthiraptera Thysanoptera Hemiptera Coleoptera Rhaphidioptera Megaloptera Neuroptera Hymenoptera Holometabola Mecoptera Siphonaptera Diptera Strepsiptera Trichoptera Lepidoptera Vascular plants Seed plants

1 2 3 4 Steps in arthropod evolution Common ancestor - legless annelid - undifferentiated body 2 Paired bilateral appendages - development of somites, antennal segments, and simple eyes (like Onychophora) 3 4 3. Early arthropod - better developed eyes and jointed legs Reduction in appendages - cephalization -modification of first appendages into mouthparts - development of three tagmata

What about the Onychophora (“velvet worms” )? Annelid Arthropod Characteristics Characteristics -worm-like body -segmented legs (during embryogenesis) Peripatus -paired nephridia -open circulatory system - hemocoel - trachea - oral appendages

Evolution of the Insects (Carpenter - 1953) Four stages in insect evolution 4. Development of metamorphosis 3. Development of wing flexion mechanisms 2. Development of wings 1. Appearance of primitive wingless insects