Topics Need for systematics Applications of systematics Linnaeus plus Darwin Approaches in systematics Principles of cladistics

Systematics - Study of diversity and evolutionary Ch. 23 – Understanding Diversity: Systematics pp. 474-475. Systematics - Study of diversity and evolutionary connections of organisms Eukaryotes ~ 9 - 100 mill spp. - Only ~1.9 mill spp. described Quality of life - depends on tightly interwoven www of life Human dependence - Composition of atmosphere - Fresh and sea water - critical food sources - Pharmaceuticals - >40% - living systems (many from rain forests) Many cultures directly depend on biodiversity of nature Biodiversity - currently challenged by human impact at a multitude of levels - unpredictable disasters

classifying organisms Systematics Ch. 23 – Understanding Diversity: Systematics p. 475-478. Taxonomy Taxonomy - Science of naming, describing and classifying organisms Systematics Systematics - Study of biodiversity with the objective of determining evolutionary relationships of organisms (phylogenetic analysis)

Why Systematics ? A universally accepted name to every organism Ch. 23 – Understanding Diversity: Systematics pp. 474-480. Why Systematics ? A universally accepted name to every organism Grouping - Aid to memory Understand evolution Stronger interpretation of experimental results

Carolus Linnaeus, 1758 Two main features of Linnaean Taxonomy Ch. 23 – Understanding Diversity: Systematics pp. 474-476. Carolus Linnaeus, 1758 Two main features of Linnaean Taxonomy - Binomial Nomenclature - Grouping into taxonomic categories

Binomial Nomenclature Ch. 23 – Understanding Diversity: Systematics p. 474-476. Binomial Nomenclature Generic name - Genus Specific epithet - Species Writing scientific names

Grouping into Taxonomic Categories Ch. 23 – Understanding Diversity: Systematics p. 476. Grouping into Taxonomic Categories Plantae Terrestrial, multicellular, photosynthetic organisms KINGDOM PHYLUM CLASS ORDER FAMILY GENUS SPECIES Anthophyta Vascular plants with flowers, fruits, and seeds Monocotyledones Monocots: Flowering plants with one seed leaf (cotyledon) and flower parts in threes Commelinales Monocots with reduced flower parts, elongated leaves, and dry 1-seeded fruits Poaceae Grasses with hollow stems; fruit is a grain; and abundant endosperm in seed Zea Tall annual grass with separate female and male flowers Zea mays Only one species in genus—corn Domain Eukarya on top Picture in 7th Ed.

Domain Eukarya on top Ch. 23 – Understanding Diversity: Systematics p. 477. KINGDOM PHYLUM CLASS ORDER FAMILY GENUS SPECIES Felis catus Felis Felidae Carnivora Mammalia Chordata Animalia Domain Eukarya on top

Clade-based PhyloCode rather than Linnaean hierarchical classification Ch. 23 – Understanding Diversity: Systematics pp. 479-481. Clade-based PhyloCode rather than Linnaean hierarchical classification

Systematists Reconstruct Phylogeny Ch. 23 – Understanding Diversity: Systematics p. 481-484. Systematists Reconstruct Phylogeny Systematics tries to reconstruct evolutionary relationships (phylogenies) Homologous structures - important in establishing such relationships Use homologous characters - structural, behavioral, physiological, developmental, molecular - not just morphological Convergent evolution and reversed structures - reveal homoplasy - not always easy to distinguish from homology

Ch. 23 – Understanding Diversity: Systematics p. 484-485.

Relationships among or within taxa Ch. 23 – Understanding Diversity: Systematics p. 484-486. Relationships among or within taxa Ideally, a taxon - evolutionary relationships Monophyletic taxon - Ancestor and all of its decendents - a natural grouping - clade Paraphyletic taxon - Common ancestor and some, but not all, of its descendents - reflects many/complex lines of evolutionary processes Polyphyletic taxon - Several evolutionary lines - does not necessarily include the most recent common ancestor to all compared types – descendants from many ancestors To be avoided/further analyzed. Do not represent natural associations

Tree-like Diagrams (Phylogenetic Trees) Source: Biology of Plants. Raven, Evert and Eichhorn. 1999

Shared Characters in Systematics Ch. 23 – Understanding Diversity: Systematics pp. 483-485. Shared Characters in Systematics Shared ancestral characters - traits in a common ancestor that persist in all descendants (plesiomorphic characters) Shared derived characters - first appeared in more recent common ancestor(s) and found in the descendants of that ancestor only (synapomorphic characters) A synapomorphic character in a more inclusive taxon becomes a plesiomorphic character in a narrower taxon

Different approaches to construct phylogenetic trees Ch. 23 – Understanding Diversity: Systematics p. 486-487. Different approaches to construct phylogenetic trees Phenetics – Neumerical taxonomy - use phenotypic and other similarities - shared characteristics (derived + ancestral) – use molecular similarities too – test statistical significance of similarities Cladistics – Phylogenetic systematics - analyses shared derived characteristics to determine evol. relationships – use common ancestry and homologous characters Evolutionary Systematics (Classical/traditional Evol. Syst.) – Use phenotypic similarity + shared ancestral and derived characters – recognizes (allows) paraphyletic taxa

Cladistics - Phylogenetic Systematics Ch. 23 – Understanding Diversity: Systematics pp. 486-489. Cladistics - Phylogenetic Systematics Focuses on common ancestry/branching sequence, not evolutionary divergence/phenotypic similarity Constructs cladograms using common ancestor (based on shared derived characters determined through outgroups), parsimony analysis (grouping organisms based on minimum number of character changes during evolution - simplest explanation - best) and maximum likelihood Outgroup is missing shared derived character(s) of ingroup

Ch. 23 – Understanding Diversity: Systematics pp. 487-489. Outgroup Analysis Characters and their states – states can be more than two

Ch. 23 – Understanding Diversity: Systematics pp. 487-489.

Ch. 23 – Understanding Diversity: Systematics p. 488-492.

Evolutionary Systematics Vs. Cladistics Ch. 23 – Understanding Diversity: Systematics p. 487. Evolutionary Systematics Vs. Cladistics

More monophyletic groups Minimum number of changes in characters Ch. 23 – Understanding Diversity: Systematics p. 490-491. More monophyletic groups Minimum number of changes in characters - more accurate construction of the phylogeny Use of modern molecular techniques - Molecular Systematics - Character changes are changes on DNA - mutations Use of computational Power