Category: Advanced Systematics

Phylogenetic trees DNA sequences from chloroplast, mitochondrial, and nuclear genes infer evolutionary relationships. Angiosperm phylogeny has been revolutionized by multi-gene and genomic datasets. Tree building methods Maximum likelihood — models of sequence evolution. Bayesian inference — posterior probability of clades. Coalescent methods — population-level histories. APG system Angiosperm Phylogeny Group classification updates family placements based…

Cladistic principles Groups must be monophyletic — include common ancestor and all descendants. Paraphyletic groups (excluding some descendants) are rejected in modern systematics. Homoplasy vs synapomorphy Synapomorphies are shared derived characters supporting clades. Homoplasy is similarity from convergence or reversal — confuses classification if not analyzed carefully. Practical impact Field guides and floras update names…

Barcode regions Standard regions include chloroplast rbcL, matK, and nuclear ITS for many plant groups. No single barcode works for all species equally. Applications Identify morphologically similar species Detect mislabeled commercial plant products Environmental DNA (eDNA) from soil or water samples Limitations Hybridization, incomplete lineage sorting, and low variation in some genera require multi-locus or…

Herbarium value Pressed specimens with locality data are permanent vouchers for research, taxonomy, and education. Millions of specimens document biodiversity through time. Collection protocol Collect flowers, fruits, and representative leaves Record GPS, habitat, associated species, collector Press between newspaper in plant press with ventilation Mount on archival paper with glue; label with acid-free ink Digital…

Rules for naming The ICN governs scientific names of plants, algae, and fungi. Names must be Latin or latinized, published validly, and tied to a type specimen. Key concepts Type specimen — physical reference for the name Synonym — older names replaced by correct name Author citation — who validly published the name Why it…

Compact floral description Floral formulas summarize symmetry, sex, fusion, and ovary position. Diagrams show organ arrangement in cross-section view. Reading examples Pea family formula: K(5) C5 A(9)+1 G1 — fused sepals, five petals, diadelphous stamens, single carpel. Diagnostic value Floral traits remain essential where DNA is unavailable and for field identification keys in floras.