Systematics Study of pattern and processes associated with biological diversity and diversification Taxonomy – study of classification (hierarchy, naming  Diversity) Phylogenetics – study of evolutionary relationships between species and groups (Diversification)

Species Concept Biological species concept – definition All species concepts have limitations Classification is a human construct Importance of defining a species

Phylogenetics Homologies

Phylogenetics Convergence

Phylogenetics Apomorphy – derived trait Pleisomorphy – primitive trait

Subspecies Populations – coat color of subspecies match local substrate

Evolution Macroevolution – lineages of species and major groups, changes in diversity Microevolution – changes in species, short and longer term; contemporary species Not segregated; difference in scale

Macroevolution Evolution does not proceed at a uniform rate Bradytelic – lineages changing at slower rates than typical Tachytelitic – faster rates than typical Horotelic - typical

Punctuated Equilibrium Proposed abrupt changes in lineages following long periods of stasis Mass extinctions  adaptive radiation Does not contradict natural selection; still a key process in punctuated equilibrium Gradualism also occurs

Gradualism

Macroevolution Rapid Radiation not always with mass extinctions Cambrian Explosion Mass extinctions may not be random Species selection (large sp. end Cretacrous

Mechanisms of Evolution Mutation Genetic drift Gene flow Natural selection

Adaptation and Range Expansion Range of a species includes range of populations Populations on edge of range may adapt to a limiting condition Some species may not have capacity to adapt morphologically, physiologically, or behaviorally peripheral conditions

Adaptation and Gene Flow Gene flow changes allele frequencies of populations Can, however, homogenize gene pool through exchanges between populations Restricts further adaptation to local conditions Other limitations to adaptation limit range expansion (not all species have wide ranges)

Distribution of karyotypes of Palestine mole rat (Nannospalax ehrenbergei) Lack of overlap  reduced gene flow

Geographic Variation Geographic isolation facilitates genetic drift and natural selection Impedes gene flow Genetic drift – isolation of small populations Founder effect

Divergence of monarch flycatcher Founder effect – colonizers of islands created gene pool for each

Allopatric Speciation Speciation resulting from geographic isolation Broader definition applying environmental and physical barriers Dispersal barriers in heterogeneous environment Geographic isolation after dispersing to another habitat (e.g., island to island)

Allopatric Speciation: Vicariance All in Family Ranidae Endemic Mad.

Sympatric Speciation and Adaptive Radiation

Extinction Changing of the guard (dominance in given niches) Cephalopod molluscs  teleost fishes Dinosaurs & reptiles  birds and mammals Species are eliminated or supplanted in their lineages

Extinction Probability of extinction independent of evolutionary age Is related to taxonomic and ecological status Small, herbivorous mammals lower extinction rates than large carnivores Same true for marine invertebrates Ties back to point about more niches for small organisms?

Extinction of Species Primary causal mechanisms for extinction Reduction of population sizes Habitat changes

What pushes numbers of a species down to the point where it is pushed to extinction?

Fossil Record and Mass Extinctions Many events, many hypotheses Pleistocene – megafauna of N. and S. Amer. 8,000 – 15,000 yr ago Once thought to be climate change from recession of glaciers More evidence that human colonization was a major contributor

Fossil Record and Mass Extinctions Permian-Triassic 250 mya 96% of marine species lost Causal Agent? –Climate change but how –Glaciation –Global warming –Massive volcanic activity –Continental drift

Seabed in P-T before and after mass extinction > 100 Species4 - 5 Species

Species Selection What leads to species surviving and radiating after extinctions? Appear to be key traits Remaining species in range also a factor

Expansion of mammals after K-T extinction (65 mya) Filled niches left behind by dinosaurs and reptiles pushed to extinction

Placental Mammals Found globally in fossil record Few extant species in N. & S. America Australian marsupials Why? Adaptive radiation in absence of dominant reptiles Later natural and human intro of placentals

Dispersal Advantage

Replacement