Paleontology!University of Wisconsin – Madison Andrew A. Zaffos May 4, 2016

The past is the key to the future

Final research proposal n  A PDF on GitHub

n  A PDF on GitHub

n  A PDF on GitHub

n  A PDF on GitHub

n  A PDF on GitHub

n  A PDF on GitHub

n  A PDF on GitHub

n  A PDF on GitHub

n  A PDF on GitHub

n  A PDF on GitHub

n  Make sure you are within the character limit for each section.

Observations about biodiveristy n  Modern Biodiversity

n  There are anywhere from 4-40 million extant species n  The tropics hold the highest concentration of biodiversity n  Biodiversity is generally concentrated in a few hotspot regions

n  Ancient Biodiversity n  Incredibly difficult for us to estimate n  The highest concentration of biodiversity migrates with latitude through time n  Biodiversity is also generally concentrated in a few hotspot regions, but

paleontologists remain skeptical that these are real and do not represent sampling biases. n  2001: Pliocene fossils from the Isthmus of Panama constitute about 18% of

total known Pliocene diversity, despite the fact that this area is less that 1/10th of a percent of the total amount of Pliocene deposition world wide.

n  Counter Argument – Both sides of the isthmus of Panama are biodiversity hotspots today.

An aside about hidden biodiversity

The sixth mass extinction? n  Mass Extinction

n  When >75% of species go extinct in a geologically short interval (1-3 million years).

n  This has both a rate component and a magnitude component

n  Humans are causing a sixth mass extinction n  Co-Opting Resources n  Habitat Fragmentation n  Introducing non-native species n  Spreading pathogens n  Direct killings (e.g., hunting, road kill) n  Changing global climate

What are some problems? n  Incompatible Species Concepts

n  Taxospecies – The ‘cause I say so method n  Morphospecies – Based on the morphology of species n  Reprospecies – Populations that can interbreed n  Ecospecies – Ecologically similar species

n  Stated Problem n  Most fossils use a morphospecies concept n  Most modern organisms use a reprospecies concept

n  The Truth n  Most fossil and modern modern species use a mixed bag of concepts,

usually taxospecies.

n  Easy Solution n  Just use genus for both the modern and the fossil record is the only way to

move forward.

What are some problems? n  Different geographic sampling

n  Most fossils come from temperate regions, particularly northern latitudes (North America, Europe, and South China)

n  Most fossils come from marine, fluvial, or lacustrine environments, because we need water to transport sediments to bury fossils.

n  The Truth n  Most modern species/genera for which we have good range and

abundance data are also species/genera for which we have good range and abundance data in the fossil record.

n  The Solution n  Be smart about what species you are analyzing

n  Be consistent about taxonomic group n  Be consistent about compared environment n  Be consistent about compared region

What are some problems? n  Measuring Fossil extinction

n  Signor-Lipps Effect n  Holland Effect

n  Measuring Modern extinction n  Too Conservative? – Doesn’t accurately account for functionally extinct

species. n  Too Liberal? – Overestimates extinction by conflating rare with extinct.

n  The Solution n  Use conservative estimates for both the modern and fossil record. n  Confidence intervals!

What are some problems? n  Assessing extinction rates

An aside about extrapolation

What can the fossil record tell us? n  Human-centric mechanisms

n  Spreading Pathogens n  Direct Killings (e.g., hunting, road kill)

n  Habitat Fragmentation n  Understudied at small-scales (regions, landscapes) in the fossil record n  May lead to vicariance/dispersal and allopatric speciation at broader

spatiotemporal scales.

n  Introducing non-native species n  We know that modern invasions can greatly disturb communities, but

extinction is rarer and harder to prove.

n  Changing global climate (Environmental forcing) n  We know this one does have an effect! n  Co-evolutionary effects?

What can the fossil record tell us? n  Asteroids

n  Volcanoes

n  Glacial/Interglacial

n  Anoxia/Euxinia

n  Acidification

n  Turbidity

n  Eustasy

n  Radiation from space

A sidebar about invasion

A sidebar about invasion

A sidebar about invasion

What can the fossil record tell us? n  Alternating mass and background selectivity regimes

n  Background extinction n  Taxa with small geographic ranges and low abundances are the most

likely to go extinct.

n  Mass extinction n  There is no advantage to having a large geographic range size or

abundance.

n  Inference n  If we see rapid reductions in geographic range size or abundance then

that may imply we are in a mass extinction selectivity regime.

n  The problem n  Are these large reductions in geographic range size or abundance

significant over geologic timescales?

View to the future n  Standardize rate comparisons to adjust for rate measurements over

widely disparate timescales

n  Standardize magnitude comparisons by using the same species concepts for modern and fossil organisms

n  Standardize taxonomic and geographic comparisons by using modern and fossil taxa that have equal fossilization potential

n  Assess the extinction risk of modern taxa such as bivalves and gastropods that are extremely common in the fossil record, but are at present poorly assessed.

n  Further explore the relationship between extinction selectivity and extinction intensity.

n  Develop and test models that posit general conditions required for mas extinction, and how those compare with the current state of the earth

Most of things have to do time-resolution n  Time-averaging means that many of the implicit assumptions of

modern extinction theory are very hard (or cannot be) verified or rejected using the fossil record.

The way forward n  If we want to directly compare the fossil record and modern

organisms

n  Keep geographic region and environment constant

n  Keep the taxonomic group constant

n  Study “time-poor” sediments and environments n  Time-rich sediments like condensed/flooding surfaces n  Time-poor surfaces where burial is sudden

Selectivity, magnitude, and models n  Many mass extinctions ARE selective, but in different ways.

n  End Permian extinction n  Geographic range size was not advantageous n  Abundant organisms were actually slightly more likely to survive n  It was selective against organisms with calcite shells and high

metabolisms. n  End-Triassic

n  Hit amphibians and reptiles much harder then fully terrestrial organisms that could adapt to arid environments.

n  If we are concerned that humans are causing the sixth mass extinction, then we want to model what selectivity patterns best match human-centric extinction mechanisms.

An example n  A human-induced mass extinction via habitat fragmentation?

n  Wide ranging, but low population density organisms should be at risk n  Top Predators – Cheetahs n  Migratory Animals – Bison, Geese n  Weedy Plants and Algaes

n  An affinity for urban vs. rural environments n  Can use urban-rural ecological gradients to find communities that have an urban “niche” vs. rural “niche”.

Thing to keep in mind n  The fossil record cannot give us the kind of information, (e.g.,

decadal scale population dynamics) that ecologists want for extinction analysis. n  Taxonomic considerations, Time Resolution, Spatial Resolution

n  Furthermore, most ancient mass extinctions are not only unlike today, they are unlike each other in many ways.

n  What paleobiology can contribute to extinction theory and analysis is the way of thinking and the analytical approach. n  Caution!!