the past is the key to the...
Post on 26-Sep-2020
1 Views
Preview:
TRANSCRIPT
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!!
top related