Modern taxonomy Building family trees Tom Hartman www.tuatara9.co.uk Classification has moved away from the simple grouping of organisms according to their similarities (phenetics) and has become the study of patterns of diversity within an evolutionary context (systematics). This has lead to the idea of a tree of relationships. Animal kingdom Module 1 11119 2 Knowing a lot about lots of creatures. 2. phylogenetic reconstruction which attempts to identify shared, derived characters (synapomorphies). 3 4 TAXA Lancelet (outgroup) Lamprey Tuna Salamander Turtle Hair 0 0 0 0 0 1 Amniotic (shelled) egg 0 0 0 0 1 1 Four walking legs 0 0 0 1 1 1 Hinged jaws 0 0 1 1 1 1 Vertebral column (backbone) 0 1 1 1 1 1 (a) Character table. A 0 indicates that a character is absent; a 1 indicates that a character is present. Salamander Turtle Hair Tuna Amniotic egg Lamprey Four walking legs Hinged jaws 5 Lancelet (outgroup) Vertebral column (b) Cladogram. Analyzing the distribution of these derived characters can provide insight into vertebrate phylogeny. 6 1
Synapomorphy 2. phylogenetic reconstruction which attempts to identify shared, derived characters (synapomorphies). 7 Shared derived characters. a character or trait that is shared by two or more taxonomic groups and is derived through evolution from a common ancestral form i.e. It is a feature that is present in two taxa AND their most recent common ancestor. This works with homologous traits, but distinguishing the analogous ones is the trick. A derived homology. A shared trait that is developed separately would be homoplasy (e.g. wings in bats and pterosaurs). The best synapomorphies characterise a group. 8 Shared characters Shared characters Four egg laying vertebrates Four tetrapods One scaly Two feathery (and scaly) One hairy 9 Three have complex skull architecture One has a simpler skull architecture Three have no teeth 10 Shared characters Some characters are widely distributed Live bearing Three have four chambered hearts Three have a high metabolism Three show parental care One produces milk from mammary glands 11 12 2
2. phylogenetic reconstruction which attempts to identify shared, derived characters (synapomorphies). 3. A classification that organises the data into a series of interconnected ranks. In the past groups were defined by shared characters such as scales, fur or feathers; now they are defined by common ancestry. Domestic cat 13 Common ancestor 14 Ordering relationships Wolf Fox Domestic cat A. gecko B. crocodile reptiles C. robin bird Common ancestor 15 Three diapsids 16 Diapsid Shared derived characters A. Gecko - B. Robin - C. Crocodile - Amniotes. Diapsid. Many shared skeletal features = archosaur. Gecko Bird Crocodile Clade 1 17 Clade 2 18 3
gecko bird crocodile gecko crocodile bird 19 20 Another graphical representation gecko crocodile bird Two branches Branching points Strictly, Reptile should be used for all non-mammalian, hard shelled egg producing tetrapods (and derived ones). Thus it has to include the birds i.e. to include all the branches that are derived from the common ancestor. We use reptiles informally for scaly animals that do not have feathers or fur, etc. Can this go too far? Q. What sort of an animal was the common ancestor of the reptiles (including birds) and the mammals? A. It was a reptile (some people get round it by calling them stem-amniotes)! 21 22 How would you arrange these? Add another branch Monitor lizard Gharial Tyrannosaur Bird 23 24 4
What about extinct species? Dave the fuzzy raptor. Sinornithosaurus Very obvious dinosaur features. Covered in integumentary appendages that look like feathers. Microraptor gui Another raptor, but with flight feathers... more than most. 25 26 Add another branch Monitor lizard Crocodile Tyrannosaur Raptors Bird 27 28 The tree of life. According to Tom Cavalier-Smith Rhizaria Neomura Archaebacteria Unikonts Amoebozoa Opisthokonts (animalia, fungi choanozoa) Plants Alveolates Eukaryota Eubacteria Bikonts Rhizaria Chromoalveolates Excavata Opisthokonts Excavates Plantae 29 30 5
Within the opisthokonts choanoflagellates animals microsporidians fungi You are here 31 32 The twig of the tree that is the animals Animals Animals All other animals Sponges Choanoflagellates Choanoflagellates Fungi Fungi 33 34 Animals All other animals (bilateralia) Radiata Sponges Choanoflagellates Fungi What, then, is an animal? Old definitions. Five kingdoms. Three domains. Working out relationships. Exclusion and inclusion. The impact of molecular data. 35 36 6
End of lecture 37 7