Taxonomy Species Concepts, & Biological Diversity EEOB September 2004

Hierarchical Indicators of Biodiversity Genetics – (population) Population – Species Community- Ecosystem Landscape – * Each with: Composition, Structure, & Function (M&C Fig. E4A)

Population Community Landscape Levels of Biological Diversity Genetic Demographic From Temple 1991, drawing by T. Sayre

Genetic (population) Composition Allelic diversity Presence/absence of rare alleles Structure Heterozygosity & genetic structure Phenotypic polymorphism Function Inbreeding & outbreeding rate

POPULATION-SPECIES (demographics) Composition Absolute and relative abundance, density, Structure Sex ratio, age distribution Distribution Function Natality, Mortality, Immigration, Emigration Population growth and fluctuation Behavioral patterns and processes

COMMUNITY-ECOSYSTEM Composition Species richness Species diversity (evenness, e.g.,Shannon-Weiner Index) Gilds & associations Structure horizontal & vertical foliage profiles Range of ages and seral stages Function Frequency & intensity of disturbances Flow of energy and Cycling of nutrients

LANDSCAPE Composition Variety and distribution of Communities Structure Patch size frequency distribution Edge zone: interior zone ratio Function Rates of nutrient & energy, and biological transfer between different communities

SYSTEMATICS and TAXONOMY Systematics: study of phenotypic variation within & between taxa to reveal phylogenetic relationships Taxonomy: Naming & ranking of taxa with a goal of stable, universal nomenclature and a system for information storage & retrieval. Several schools but phylogenetics (cladistics) is most widely practiced and accepted Taxon: a group of organisms recognized as a formal unit in a hierarchial system of classification

Central Position of Species in Biodiversity Importance compared to taxa in higher categories, i.e., genus, family, or class Species are real and distinct (?). Real because they are functional units in nature. Distinct because of common gene pool and limit gene flow between species Species are also real because many can be recognized by both laymen professional biologists Typological vs. populational views of species

Species: Concepts & Definitions Biological species concept (traditional) Reproductive isolation of sexually reproducing species Practical and widely used (basis for nearly all alpha taxonomy) Problems & limitations? Cladistic Species Concept The smallest cluster of organisms diagnosable by a synapomorphy P opular among systemitists Less so among alpha taxonomists Provides valid basis for sup-specific taxa (~ subspecies)

Cladogram of Chordates Hickman et al Fig.15.3 (2003) - See also, M&C Fig.3.3 Synapomorphies

Wilson 1992 – Diversity of Life

Patterns in Biodiversity Taxonomic Diveristy (richness of higher taxa) Species richness of higher taxa i.e., number species per taxon Richness of taxa over geological time Patterns of local species richness Global patterns in species richness

Hickman et al. 2003

Patterns in Biodiversity Taxonomic Diversity (richness of higher taxa) Species richness of higher taxa i.e., number species per taxon Richness of taxa over geological time Patterns of local species richness: Point richness = number in single spot (sample plot) α = total number in a small, homogeneous area β = rate of change/ turnover across a landscape

Estimates of number of species on Earth Based on the rate at which new species are being discovered per taxon. Projection of a “regression line” based on body size and species richness Terry Erwin’s projection from tropical rainforest beetle species richness

Estimating number of species from rate of new discoveries

Estimates of number of species on Earth Based on the rate at which new species are discovered per taxon. Projection of a “regression line” based on body size and species richness Terry Erwin’s projection from tropical rainforest beetle species richness Dr. Terry Erwin, Entomologist, Smithsonian Institution

* Calculations based on 70 tree species/ha, which projects to about 30 million arthropods worldwide Erwin, TL Tropical forests: Their richness in Coleoptera and other arthropod species. Coleopt. Bull. 36: / 70 species x 41,389 =

Patterns in Biodiversity Taxonomic Diversity (richness of higher taxa) Species richness of higher taxa i.e., number species per taxon Richness of taxa over geological time Patterns of local species richness Global patterns in species richness

Patterns in Alpha richness: Why are there so many species in the tropics? High Primary Productivity Habitat size (island biogeography) Habitat complexity (heterogeneity)