Phylogeny and Systematics

Phylogeny Evolutionary history of a species of a group of related species Information used to construct phylogenies includes: – Fossil record – Molecular comparison (DNA, RNA, proteins) – Breeding behavior/embryological development – Biogeography – Morphology

Systematics The study of biological diversity in an evolutionary context Encompasses taxonomy, goal is to trace phylogeny Modern phylogenetic systematics = classification based on evolutionary history

Cladogram Phylogenetic diagram based on cladistics – Cladistics = form of taxonomy based on shared characteristics not found in ancestral group – Clade = evolutionary branch in cladogram; consists of ancestral species and all descendants

Clade A clade consists of ancestral species & all descendants – Grouping of species is known as monophyletic if it meets this standard – Circle the monophyletic group that includes organisms E and H:

Clade A clade consists of ancestral species & all descendants – Grouping of species is known as monophyletic if it meets this standard – Circle the monophyletic group that includes organisms E and H:

Non-monophyletic groups:

Constructing a cladogram: #1: Sort homology from analogy Homology: – Similar structure and shared ancestry – The greater # of homologous parts the more closely related Analogy: – Different structure; similar function (wings of birds vs. butterflies vs. bats) – Come to resemble each other because experience similar environmental pressures

#2: Identify shared derived characters Shared primitive characters Not limited to group being studied Example: backbone & mammals (backbones not limited to mammals) Shared derived characters Evolutionary novelty unique to clade Example: hair is unique to mammals

#3: Outgroup comparison Outgroup = species closely related to species being studied Ingroup = species being studies – Identify characteristics to be studied – Create data matrix comparing characteristics – Construct cladogram

Example

Example from molecular data