Biogeography--study of the distributions of organisms on the earth Biota—the flora and fauna of a region

Objectives of Biogeography Classifying geographic regions based on their biotas Reconstructing the historical development of biotas, including their origin, spread, and diversification Explaining differences in numbers and types of species among geographic regions

Objectives of Biogeography Explaining geographic variation in characteristics of individuals and populations of closely related species

Zoogeography—the distributions of animal species However, phytogeography and zoogeography are closely linked

Zoogeography synthesizes data from Phytogeography Ecology Evolutionary Biology Paleontology Geology Geography

Two of many different specialized areas in biogeography include: Historical biogeography Ecological biogeography

Two important issues Change—earth is dynamic Scale

The scientific process Identification of patterns Development of explanations or hypotheses for these patterns Development of predictions from the hypotheses. Testing of predictions with data

Assumption of uniformitarianism or actualism

Darwin’s observations Fossils Vicariant species Galapagos species

The Origin of Species published in 1859

Biological evolution is simply changes in gene frequencies within populations over time. A population is a group of organisms of the same species found together at one place at one point in time.

Biologists assume changes in gene frequencies are linked to changes in the frequencies of morphological, physiological, and behavioral characteristics of individuals.

Natural selection is one mechanism of evolution

Necessary and sufficient conditions for natural selection: Variability of traits among individuals Heritability of these traits Differential reproductive success associated with these traits

Keep in mind: Traits which increase reproductive success, rather than survivorship, are more likely to increase in frequency in future generations Individuals and their traits are acted upon by natural selection, not species

Other agent of evolution: Genetic drift

Speciation Phyletic speciation (anagenesis) True speciation (cladogenesis)

Allopatric speciation Geographic isolation Population divergence Why do populations diverge? Natural selection Genetic drift

Biological species—a group of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups

Ethological differences Mechanical differences Post zygotic: Isolating mechanisms (evolved through natural selection or genetic drift) Prezygotic: Habitat differences Temporal differences Ethological differences Mechanical differences Post zygotic: Poor quality offspring

Problems with bsc Semi-species Allochronic species Allopatric species Ring species Asexual species Hybridization

Phylogenetic species concept (PSC)--a species is the smallest aggregation of populations diagnosable by a unique combination of characters and that share a common ancestor. Reproductive compatibility is not a criterion for deciding whether individuals belong to the same species or not.

Problems with the PSC Leads to too many species Ignores important biological information such as reproductive compatibility Species can be diagnosed on the basis of trivial characters Too much emphasis on morphology

Evolution is an ongoing process Any two individual organisms are somewhere between very distantly related and very closely related The evolution of new species takes place over time so any group of organisms may be somewhere along the line from being either full conspecifics, or members of fully separate species