Cladistics

History of Life Eras Boundaries between units in the Geologic Time Scale are marked by dramatic biotic change A figure from Ch. 26… 4500 Origin of Earth

5 Kingdom classification system in use through the late 1900s

5 Kingdom classification system in use through the late 1900s gave way to Woese’s 3 Domains

5 Kingdom classification system in use through the late 1900s gave way to Woese’s 3 Domains and multiple Kingdoms

“Did King Philip Come Over For Gumbo Sunday?” Fig. 25.8 “Did King Philip Come Over For Gumbo Sunday?” Taxon (taxa) = the named taxonomic unit(s) at any level in this taxonomic hierarchy Each taxonomic level is more inclusive or comprehensive than the previous one (moving from species toward domains). Panthera = genus pardus = specific epithet that refers to one species in the genus Panthera

Macroevolution & Phylogeny Phylogenetic tree – hypothesized genealogy traced back to the last common ancestor (i.e., the most recent) through hierarchical, dichotomous branching Note that this is a highly pruned tree! Cladistics – the principles that guide the production of phylogenetic trees, a.k.a., cladograms

Macroevolution & Phylogeny Phylogenetic tree, phylogeny, or cladogram Node – branch point, speciation event Note that this is a highly pruned tree!

Macroevolution & Phylogeny Phylogenetic tree, phylogeny, or cladogram Note that this is a highly pruned tree! Lineage or clade – an entire branch

Macroevolution & Phylogeny Phylogenetic tree, phylogeny, or cladogram Note that this is a highly pruned tree! Lineage or clade – an entire branch

Macroevolution & Phylogeny Phylogenetic tree, phylogeny, or cladogram Note that this is a highly pruned tree! Lineage or clade – an entire branch

Macroevolution & Phylogeny Phylogenetic tree, phylogeny, or cladogram Note that this is a highly pruned tree! A clade is a monophyletic group, i.e., an ancestral species and all of its descendents

Macroevolution & Phylogeny Phylogenetic tree, phylogeny, or cladogram Note that this is a highly pruned tree! A clade is a monophyletic group, i.e., an ancestral species and all of its descendents

Macroevolution & Phylogeny Phylogenetic tree, phylogeny, or cladogram Note that this is a highly pruned tree! A clade is a monophyletic group, i.e., an ancestral species and all of its descendents

Macroevolution & Phylogeny Phylogenetic tree, phylogeny, or cladogram Note that this is a highly pruned tree! A paraphyletic group consists of an ancestor and some of its descendents

Macroevolution & Phylogeny Phylogenetic tree, phylogeny, or cladogram Note that this is a highly pruned tree! A polyphyletic group lacks the common ancestor of species in the group

Macroevolution & Phylogeny Note that this is a highly pruned tree! Fig. 25.9 Taxonomic groups often reflect true clades…

Macroevolution & Phylogeny However, tension sometimes exists between taxonomic tradition and cladistic hypotheses… Note that phylogenetic trees can be oriented any which way.

Macroevolution & Phylogeny E.g., If the Class Reptilia is to be monophyletic, birds must be included!

Macroevolution & Phylogeny How are phylogenetic trees constructed?

Cladistic Analysis Fossils provide morphological data for extinct species, whereas comparisons of multiple types of traits – including molecular – do so for extant species

Ingroup = the group whose relationships we are trying to resolve Cladistic Analysis Ingroup vs. Outgroup Ingroup = the group whose relationships we are trying to resolve Fig. 25.11

Cladistic Analysis Ingroup vs. Outgroup Outgroup = a species (or group) known to have an older most recent common ancestor with the ingroup than the ingroup’s most recent common ancestor Fig. 25.11

Cladistic Analysis Ingroup vs. Outgroup An outgroup helps identify shared ancestral and shared derived characters (unique to a clade) Fig. 25.11

Parsimony & Occam’s Razor Cladistic Analysis Parsimony & Occam’s Razor The most parsimonious tree is the one that requires the fewest evolutionary events (appearance of shared derived characters) Fig. 25.11

Parsimony & Occam’s Razor Cladistic Analysis Parsimony & Occam’s Razor On this most parsimonious cladogram, each key character originated (evolved) once Fig. 25.11

Cladistic Analysis An example… See Fig. 25.15 for another example Outgroup Ingroup See Fig. 25.15 for another example

Cladistic Analysis An example… See Fig. 25.15 for another example Outgroup Ingroup Create potential topologies for the tree See Fig. 25.15 for another example

Cladistic Analysis An example… See Fig. 25.15 for another example Outgroup Ingroup Create potential topologies for the tree The first topology requires 7 changes, the second 9, and the third 8. Map the characters onto the trees Choose the most parsimonious tree See Fig. 25.15 for another example

Macroevolution & Phylogeny Sometimes the most parsimonious arrangement for one character is not the most accurate overall… Bird-mammal clade Lizard-bird clade Fig. 25.16

Macroevolution & Phylogeny Don’t confuse the age of a clade with the age of its component species African Rift Lake Cichlid Alligator Snapping Turtle ~ 200,000 yr ~ 20,000,000 yr Based on the cladogram, which species is likely to be older? Once a clade arises, speciation events can continue to occur within it.

Answer to Cladistics Homework Lungfish Turtle Wolf Lamphrey Human Gorilla Pike Bony Shell Grasping Hand Hair Lung Jaw