Peter Wilf's research
Fossil plants tell the
evolutionary story of our green planet and reveal its landscapes from deep time
to present. They are also extremely sensitive indicators of past climates, plant-insect
interactions, biodiversity, and the effects of
major environmental disturbances. These data provide deep-time analogs
that uniquely illuminate modern
ecosystems and their possible responses to anthropogenic change. The time period I mostly study is the latest
Cretaceous through middle Eocene, 67-45 million years ago (Ma), an interval
characterized by global disturbances that are
closely spaced in geologic time. These include latest Cretaceous warming
and cooling (68-66 Ma), the end-Cretaceous mass extinction (66 Ma) and ensuing
recovery during the Paleocene (66-56 Ma), and both abrupt and long-term warming
across the Paleocene-Eocene boundary (56 Ma). I
enjoy collaborations with numerous colleagues around the world and a terrific lab group, with whom I
do extensive field work, concentrated currently in Patagonia, Argentina and
increasingly in SE Asia. Many of my collaborators are listed and cross-linked
in the coauthor section of my Google Scholar page,
and our research papers are also listed here.
Here are a few
highlights of current projects.
Origins of Southeast Asian Rainforests from
Paleobotany and Machine Learning
This is a new (2019-2024) cutting-edge NSF project, in collaboration with
Dr. Thomas Serre’s Brown University machine learning lab and Dr. Maria Gandolfo’s
paleobotany lab at Cornell, along with collaborators at MEF
in Argentina (continuing the Patagonia project discussed below) and in several
other countries including China, India, Australia, Indonesia, and Brunei. This tremendously exciting, emerging
project aims to develop the powerful tools of machine learning to identify
fossil leaves and thus to shed a powerful new light on the evolution of SE Asia’s
extremely biodiverse and threatened rainforests.
Coverage of our
milestone 2016 PNAS
paper included this story in Wired
and this interview
on Radio NZ This Way Up with Richard
Scott. Penn State produced a short video about the work and
this press
release.
(from the NSF award description here,
current award DEB-1556666, 2016-2020. This project has been funded by NSF since
2004.)
The fossil record of
life on land through time predominantly comes from the Northern Hemisphere.
However, the outstandingly rich, relatively little-known fossil beds of
Patagonia, southern Argentina, provide an unrivaled opportunity to learn
whether life responded differently to mass extinction, plate tectonics, and
past climate change on the other side of the world. This project intensively
samples and analyzes fossil plants and animals from Patagonia through about 20
million years, from just before the end-Cretaceous dinosaur extinction (66
million years ago), through the early recovery period and the Eocene warming
interval. Through groundbreaking field discoveries and state-of-the-art lab
techniques, this research aims to transform understanding of the origins of the
Southern Hemispheres flora and environments, the role of Patagonia, and the
legacy of surviving living fossils now located in vulnerable rainforest areas
as far away as Southeast Asia. The team plans
to generate the most complete terrestrial
record and curated fossil-plant collection
for the Southern Hemisphere through a critical interval of Earth history. The
work will produce a new, globally significant reference point for studying mass
extinction, recovery, and response to climate change from a fossilized living
laboratory, with direct importance for conservation and ecosystem management
today.
The project uses field paleontology and stratigraphy at a series of exceptional
Patagonian fossil localities, dating from the latest Cretaceous to middle
Eocene, to elevate understanding of Patagonia's uniquely informative fossil
floras. Most of the fossil sites are located
in the La Colonia, Lefipán, Salamanca, Peñas Coloradas, and Huitrera formations
of Chubut and neighboring provinces. The research focuses on five, broadly
related questions targeting significant gaps in knowledge. (1) Was Patagonia a
refuge from the end-Cretaceous mass extinction? (2) What are the composition,
diversity, and biogeographic affinities of the earliest Paleocene floras and
insect faunas? (3) Do the Eocene floras and faunas contain lineages that now
survive in South America, Asia, and Africa, as well as Australasia? (4) Do the
Eocene floras document the earliest phases of South American isolation by
showing a loss of Gondwanan taxa and an increase in New World taxa through
time? (5) How much geologic time does the prolific early Eocene site at Laguna
del Hunco represent, and what processes formed these unique deposits that
preserved one of the most diverse fossil biotas in the world?
The principal Argentine institution in this project
is the Museo Egidio Feruglio in
Trelew, directed by Co-PI Dr. N. Rubén Cúneo. Our Cornell collaborators, led by
Dr. Maria Gandolfo, have posted a very nice web page about the Patagonia project here.
The project has a Google
Scholar page here.
We are fast approaching 130 peer-reviewed papers under NSF support since 2004,
including several in Science, Nature, and PNAS.
Here are some of many news stories,
interviews, and commentaries about our work in Patagonia regarding:
The
first Fagaceae
(Beech family) fossils from the Southern Hemisphere | First fossil fruit and
oldest fossils of the nightshade family, fossil
tomatillos | Fossils that challenge molecular
dating | Exceptional diversity
in Eocene floras | The connections between SE
Asian orangutans and Patagonian fossils | The first fossil
kauri trees (Agathis) ever found
in South America | Patagonia’s petrified
forests | Fate of Patagonian
insects at the time of the dinosaur extinction | Eocene insect diversity
| First Papuacedrus,
a living New Guinea conifer genus, ever found in South America.
Evolution of
plant-insect associations
A long-term, cross-cutting research focus with Dr. Conrad
Labandeira, Smithsonian Institution, and many students and colleagues,
including the Ph.D. and subsequent work of Dr. Ellen
Currano, now Associate Professor at Univ. Wyoming, and Dr. Michael
Donovan, now of Cleveland Museum of Natural History.
Terrestrial plants and insects today account for the majority of the Earth's
biodiversity, and almost half of insect species are herbivores. Today's ongoing
global warming and habitat loss will impact insect life cycles, distribution,
and diversity. A key development in my
research program was recognition of the breakthroughs in knowledge available
from the abundant, diverse, and well-preserved insect-feeding damage found on
fossil leaves. Dr. Conrad Labandeira and I
examined the responses of insect herbivores to Paleocene-Eocene warming, from a
time interval when body fossils of insects are lacking, and we discovered a
marked increase in insect feeding that matched predictions based on modern observations. Subsequent work on the
K-Pg fossil leaves from North Dakota provided the first evidence for a mass
extinction of insects at the K-Pg as well as evidence for the Late Cretaceous
origin of a diverse insect group (hispine
beetles). Our work on the Laguna del Hunco flora from Patagonia shows a much
greater diversity of insect feeding than in contemporaneous, comparable floras
from North America, revealing another important, previously unknown component
of high diversity in Eocene South America. We have also used tropical canopy
access cranes in Panama to quantify modern herbivory and thus calibrate
fossil herbivory, with former student Dr. Mónica Carvalho (now at STRI,
Panama), entomologist colleagues at STRI, and several other paleontologists.
Here are some of many news stories,
interviews, and commentaries about our work on insect damage through time,
regarding:
Increased insect feeding
during the Paleocene-Eocene thermal maximum and early Eocene
climatic optimum | Insect extinction and recovery across the K-Pg boundary in
the Great
Plains and Patagonia
| Discovery of 66 million-year-old feeding marks of
hispine beetle larvae on fossil gingers
| Canopy
crane work in Panama
Other projects
Precolonial leaf mats from southeastern
Pennsylvania and their value for landscape reconstruction and stream restoration- with Drs. Robert Walter and Dorothy Merritts,
Franklin and Marshall College. This work provides the first landscape
reconstructions based on leaf fossils for the pre-colonial Pennsylvania Piedmont. It was the topic of two MS theses and
subsequent journal articles in PLoS
One and Palaeontologia
Electronica by Sara Elliott and Christy Grettenberger. There were several
news articles on this work (including here
and here).
The living legacy of Gondwanan rainforest
history and its conservation in Australasia and Southeast
Asia- with Dr. Robert
Kooyman, Macquarie University, and many others. This work explores the living analog
side of the Patagonian Floras and SE Asia projects and has involved several
field trips in rainforests of subtropical Australia, Tropical Australia, and
Mt. Kinabalu in Malaysian Borneo. Several papers
have been published, on paleo-neo floristic connections across Gondwana
(Kooyman et al. 2014, Am. J. Bot); site-specific living analog comparisons of
Australian rainforests and our flagship Patagonian fossil site Laguna del Hunco
(Lisa Merkhofer MS thesis and subsequent 2015 paper in Am. J. Bot.); fossil Agathis in Patagonia, including its
living analogs in Malaysia (Wilf et al. 2014, Am. J. Bot); the ecology of leaf
teeth in Australia (Royer et al. 2009, Am. J. Bot.), and a review paper on the
origins of SE Asian rainforests (Kooyman et al., 2019). This research
thread emerged from my 2005-2010
participation with Dr. Kooyman and others in the ARC-NZ Research Network for
Vegetation Function, directed by Dr. Mark Westoby, Macquarie University.
Cenozoic paleobotany of Borneo and Sumatra- Cenozoic plant fossils from these extremely
biodiverse and threatened regions have barely been
studied since the 1800s. I
participated in a 2014 field trip to West Sumatra and South Kalimantan led by
Dr. Gregg Gunnell, Duke University, and colleagues at Bandung Institute of
Technology, wherein we discovered and collected several new Eocene and
Oligocene plant-fossil localities. In
2015, doctoral student Michael Donovan and I
traveled to Brunei and, in collaboration with colleagues at Universiti Brunei
Darussalam, discovered and collected the first plant-fossil sites ever found in
that country (Miocene-Pliocene). Work is in progress and feeds into the new
Origins of SE Asian Rainforests project listed above.
What about leaf physiognomy and climate?
Correlations of leaf
shape and climate and their applications to paleoclimate reconstruction were a significant component of my early work with many colleagues. Several of
our papers demonstrated that considerably less labor-intensive, univariate
methods (i.e., leaf-margin analysis), while not problem-free, would generate
paleotemperature and paleoprecipitation estimates at least as reliable as
multivariate approaches (i.e., CLAMP). I
applied these methods to several Cretaceous through Eocene fossil floras to
investigate climate changes during critical time intervals. I also developed an alternative multivariate
method, digital leaf physiognomy, that introduced computerized measurements to
improve reproducibility. This approach came out of a productive collaboration
with University of Michigan (Peter Huff) and Penn State (Dave Janesko)
undergraduate researchers and Penn State then-postdoc Dr. Dana Royer (now
Professor, Wesleyan University).
In 2010, this line of
research forever changed when then-postdoc Dr. Stefan Little demonstrated the
significant influence of evolutionary history (“phylogenetic signal”) on
leaf-climate correlations in this
PloS One paper. Leaf-climate correlations can still be used to evaluate climate
change in a relative sense, but they are influenced both by the environment and
by history. The core challenge now is the great difficulty of disentangling
these effects quantitatively, especially in fossil floras where very few species
can be placed phylogenetically.
Ultimately, the “taxon-free-leaf” approach to paleoclimate reconstruction is
much more limited than was long thought. As a result, I have become more interested in paleoenvironmental reconstructions
that make better use of combining systematic, biogeographic, floristic,
anatomical, and/or geological data from fossil floras, and in using traits that
are less influenced by evolutionary history. The Patagonia Paleofloras project
has become a showcase of this sort of approach. For example, Lisa Merkhofer et al. (Am. J. Bot., 2015) did a detailed
investigation of how genera found as
fossils at Eocene Laguna del Hunco (Argentina) are
distributed today among a network of hundreds of Australian rainforest
plots, and how the leaf sizes of the same genera compare between ancient and
modern. To estimate leaf size, Merkhofer et al. were the first to use on
fossils the Sack et al. (2012, Nature
Comm.) secondary vein-scaling method, which seems to be largely free of
phylogenetic effects and represents the state of the art for leaf-size
reconstruction in fossil floras.
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