Lauren Graniero, student at Texas A&M and STRI short term Fellow, just published another paper that helps us make sense of the significance of stable isotope ratios in skeletal material. Continue reading →
We thank Erkens and Hoorn for their constructive comments. Like us, they believe that collaboration between biologists, geologists and paleontologists focusing on data and analyses is required to unravel the history of the Isthmus of Panama. We agree with Erkens and Hoorn that the Continue reading →
Caribbean coral reefs have transformed into algal-dominated habitats over recent decades, but the mechanisms of change are unresolved due to a lack of quantitative ecological data before large-scale human impacts. To understand the role of reduced herbivory in recent coral declines, we produce a high-resolution 3,000 year record of reef Continue reading →
The formation of the Isthmus of Panama stands as one of the greatest natural events of the Cenozoic, driving profound biotic transformations on land and in the oceans. Some recent studies suggest that the Isthmus formed many millions of years earlier than the widely recognized age of approximately 3 million years ago (Ma), a result that if true would revolutionize our understanding of environmental, ecological, and evolutionary change across the Americas. To bring clarity to the question of when the Isthmus of Panama formed, we provide an exhaustive review and reanalysis of geological, paleontological, and molecular records. These independent lines of evidence converge upon a cohesive narrative of gradually emerging land and constricting seaways, with formation of the Isthmus of Panama sensu stricto around 2.8 Ma. The evidence used to support an older isthmus is inconclusive, and we caution against the uncritical acceptance of an isthmus before the Pliocene.
Panama has a rich and unique natural history, filled with stories of change and heaps of fascinating diversity. To keep you focused on the important, we present a few of our own ‘Panama Papers’ to download and read for yourself Continue reading →
Our book, A History of Life in 100 Fossils, has just been published in French and German. As predicted, the French one looks better than any of the others, but the German version is bound to last a lifetime.
Project 1 (one position). Interoceanic differences in energy flow. Position open now, send CV and cover letter to email@example.com.
Project 2 (two positions). The ecological, life history and environmental differences between Holocene and modern Caribbean coral reef fish assemblages using fossil otoliths. To apply follow directions on the flyer.
Four years ago Panamanian student Dioselina Vigil discovered a fossil in rocks near the small town of Piña. It turned out to be more than a bunch of bones. After careful preparation under the careful guidance of Smithsonian marine mammal paleobiologist Nicholas Pyenson and his team, the amazing fossil skull, replete with most of its teeth, was revealed to be a new genus of ‘river’ dolphin which we named Isthminia panamensis.
Isthminia, now an extinct lineage, is the closest relative of the Amazon river dolphins but was found in rocks that were deposited in open ocean just 6 million years ago. In this context the evolution of the river dolphins’ ecological shift from the sea to river becomes just a little clearer.
We are extremely proud that all aspects of the study are open-access. 3D models are available from the Smithsonian’s X 3D site for anyone to download, print and study. The paper itself is published in the open-access journal PeerJ. We even made all reviews available to read in this increasingly popular model for publication and divulgation. A 3D print of the specimen is on display at the Panama’s Biomuseo, and I even have a 3D print of the fossil in my lab.
Get the article here, play around with the 3D models and print out your own Isthminia panamensis
From colleague and friend Paul Harnik’s Paleolab Blog: “How does environmental change shape the relationships between ecological traits and extinction risk? The fossil record is an invaluable resource for answering such questions. In a paper now available early online in the journal Global Change Biology, my collaborators and I show that over the last 500 million years global environmental and geochemical changes have had remarkably little effect on the relationship between geographic range size and extinction risk among marine mollusks. In other words, clams and snails with small geographic ranges have been at elevated risk of extinction throughout their evolutionary history regardless of broad-scale environmental conditions. In contrast, we found that mollusks that live in (rather than on) sediments on the seafloor tended to be at lower risk during times of warmer climate.”
Felix Rodriguez and I just published a compendium of papers in Spanish for students and non-scientists in Latin America. The book is called “Historia natural del Istmo de Panama” and features a suite of papers covering different topics from the geology of the Isthmus to the future of fishing along both coasts of Panama. The book will be on sale across the Isthmus. Let me know if you wish to purchase a copy.
Three years ago Paul Taylor was inPanama scouting for Pleistocene bryozoans along the Burica Peninsula that juts out into the Pacific Ocean at the Panamanian and Costa Rican border. Neil MacGregor had just published the book “A History of the World in 100 objects” and I mentioned Continue reading →
I have been lucky to explore many Caribbean fossil and modern reefs over the last 14 years or so. One of the things that has always struck me was just how BIG the conch were in ancient reefs compared to those of the modern day. Bringing in archeologist Thomas Wake gave us a unique historical perspective Continue reading →
We edited a special edition of the Bulletin of Marine Science entitled “Environmental, ecological, and evolutionary change in seas across the Isthmus of Panama”. This volume evolved from a colloquium Continue reading →
An Isthmus is a narrow land bridge that joins two larger bodies of land. The world’s most famous isthmus, now split by the Panama Canal, connects the continents of North and South America and cuts the once continuous Tropical American seaway into two.
The question ‘When did the Isthmus of Panama form’ has recently been reinvigorated Continue reading →
This paper was written through a collaboration with evolutionary biologist Egbert Leigh who has worked at the Smithsonian Tropical Research Institute in Panama for most of his scientific career and takes inspiration from the plants and Continue reading →
Anyone that has played with coral reef sand has felt the sharp needles of sponge spicules in their hands. Spicules are made by sponges (and other animals too, like some ascidians) and are like glass. In fact they are glass, being made of pure silica, and they are used by sponges as defense from chomping fish or to help keep the sponge rigid. They come in an amazing variety of shapes and sizes, and the sands of coral reefs can be filled with billions of spicules.
Sponges are very important for reefs. They filter huge quantities of water keeping things clear and clean, provide important homes for loads of other animals, and they protect reefs from erosion by binding the reef together. But, as with most of life in the Caribbean, sponge communities have started to deteriorate. Since the 1980’s they have become less abundant and less diverse. Without sponges reefs may just wash away.
We wish to explore the historical changes in Caribbean reef sponge communities. When did sponges decline and why? The coring project of the TMHE will be exploring sponge spicules through the last few thousand years in several Caribbean reefs (see here). However, spicules are strange beasts. Some sponges produce millions of spicules, others hardly any or none at all. Spicule shape is highly variable (see image) but is not tightly phylogenetically constrained. That means that some spicule types occur in unrelated groups. What’s more, some sponges have more than one type of spicule, sometimes three or four.
This all makes it extremely difficult to reconstruct the sponge community from a bunch of spicules. In this paper student Magdalena Lukowiak at the Polish Academy of Sciences who had held a short term fellowship at STRI explores the taphonomy of sponge spicules on a Caribbean reef in Bocas del Toro. The relationships between sponge community and spicules found on the sea floor explored in this paper will help us to resolve changes in sponge communities through our cores.
Upwelling along the Pacific coast of Central America today occurs where the land drops to less than 500m. Low land allows the trade winds to blow across and push surface waters out to open ocean causing strong coastal upwelling.
In this paper we estimate the strength of upwelling in the Plio-Pleistocene Continue reading →
What drives major ecological and evolutionary changes in the seas? To explore this question we documented changes in the abundance of different clams in the Caribbean over the past 11 Myr.
The structure of clam communities shifted dramatically with an increase in the abundance of attached epifaunal bivalves and a decrease in infaunal bivalves. This was driven by the proliferation of coral reefs, ultimately caused by the closure of the Isthmus of Panama.
These data provide a classic case of proximate and ultimate drivers of evolutionary change. Jill Leonard-Pingel was lead author. Pdf forthcoming….
In the coming century, life in the ocean will be confronted with a suite of environmental conditions that have no analog in human history. Will marine species adapt or go extinct?
The last two years I have been involved in a dynamic working group called “Determinants of extinction in ancient and modern seas” led by Paul Harnik, Rowan Lockwood and Seth Finnegan and funded by NESCent. The aim of the working group is to use the history of life as preserved in the fossil record to help make better predictions about where life is heading in the future, especially in view of the looming sixth mass extinction.
We have just published our first paper in Trends in Ecology and Evolution. The study compares the patterns, drivers, and biological correlates of marine extinctions in the fossil, historical, and modern records and evaluates how this information can be used to better predict the impact of current and projected future environmental changes on extinction risk in the sea.
Download the pdf of the paper by clicking on the image.
Records of seawater chemistry help constrain temporal variations in geochemical processes that impact the global carbon cycle and climate through Earth’s history. Here we reconstruct Cenozoic seawater Sr/Ca using fossil Conus and turritellid gastropods.
Our favored seawater Sr/Ca scenarios point to a significant increase in the proportion of aragonite versus calcite deposition in shelf sediments from the Middle Miocene, coincident with the proliferation of coral reefs. We propose that this occurred at least 10 million years after the seawater Mg/Ca threshold was passed, and was instead aided by declining levels of atmospheric carbon dioxide.
Pdf of the paper available by clicking on these images of cone shells…
Fossils and genes are the two principal ways to study evolution, but they are rarely studied together. This project allowed us to make the first integration of fossil and molecular records of cupuladriid bryozoans Continue reading →
Rising ocean temperatures and ocean acidity may deliver a deadly one-two punch to the world’s corals. Holger Anlauf placed coral larvae and young corals under four controlled culture conditions: (1) increased temperatures (2) increased acidity (3) combination of Continue reading →
As a PhD student I devised and developed a completely new technique for investigating paleoseasonality. Reconstructions of paleoenvironments often fail to understand the importance of the mean annual range of temperature (MART) in both oceanographic and biological contexts. The new technique, called the ‘zooid size approach’ makes use of the temperature-size rule in colonial bryozoans to estimate MART. The temperature-size rule is a universal phenomenon that states that body size decreases as temperature increases.
At the time, our understanding of the temperature-size rule was rudimentary and it was necessary to develop hypotheses on the mechanisms behind the rule and then test them under controlled culture and natural experiments, before finally applying the approach to fossil bryozoans to estimate MART’s in ancient seas.
The original paper published in 2000 presenting the technique can be downloaded here.
Now 10 years later with my ex-Phd supervisor Beth Okamura we review the approach along with the growing body of work that has since been published on the theme. We consider the general issue of why body size varies with temperature, explore the limitations of the approach and highlight its advantages relative to other proxies for palaeotemperature inferences.
Download the pdf of this new paper by clicking on the image.
Even genetically identical animals can look very different if they grow and live in different environments. Think ‘you are what you eat’. I make use of this phenomenon to try to reveal changes in environments in the deep past by first understanding what drives change in morphology in the animals in question and then measuring that morphology in fossils through time.
I applied this paradigm to one of the most studied and certainly most discussed events in the history of life on earth. The K-T (Cretaceous-Tertiary) boundary, 65 million years ago and the demise of the non-avian Dinosaurs and a suite of other animals and plants in the seas and on land. I made detailed measures of morphology in a number of fossil bryozoans in a beautiful K-T section of chalk in Denmark.
Rapid and repeated changes in morphology suggest that there were a suite of environmental changes in the last few thousand years just before the K-T boundary.
Although we dont explore the causes of the extinctions, or the ‘smoking gun’, these results are important for a full understanding of the complex changes associated with major extinctions observed to occur around the world. Click on the image for the pdf.
Evolutionary success was determined by mode of reproduction in cupuladriid bryozoans: Closure of the Panama Isthmus 3 million years ago led to a rapid reduction in primary productivity across the Caribbean. In response, cupuladriid bryozoans underwent a major transition, with evolutionary winners and losers dictated by how much sex they were having. Click on the image to download the pdf.
Hotspots of high species diversity are a prominent feature of modern global biodiversity patterns. Fossil and molecular evidence is starting to reveal the history of these hotspots. There have been at least three marine biodiversity hotspots during the past 50 million years. They have moved across almost half the globe, with their timing and locations coinciding with major tectonic events. The birth and death of successive hotspots highlights the link between environmental change and biodiversity patterns. The antiquity of the taxa in the modern Indo-Australian Archipelago hotspot emphasizes the role of pre-Pleistocene events in shaping modern diversity patterns. Click on the image for the pdf of the paper.
Since the late Mesozoic, several bryozoan groups have occupied unstable soft-sediment habitats by adopting a free-living and motile mode of life. Today, the free-living bryozoans often dominate epibenthic faunal communities in these expansive habitats, yet their biology and ecology remain poorly understood. This study examines their unique mode of life by exploring the relationship between form and function in the free-living Cupuladriidae of tropical America. Click on the image for the pdf of the paper.
Most people think Panama has two seas – the Caribbean and the Pacific. In fact it has three and they are each very distinct. This paper presents detailed hydrological measurements from the two seas along the Pacific coast of Panama: the Gulf of Panama and the Gulf of Chiriqui, and characterizes the environmental differences between them. Click on the image for the pdf of the paper.
We discovered a two million year lag in Caribbean extinction after the environmental and ecological events responsible. This finding challenges the conventional wisdom that evolutionary cause and effect should necessarily coincide. Click on the image for the pdf of the paper.
A full understanding of any climate requires an appreciation of the amount of seasonal variation in temperature. This is important not only for present-day climatology but also for investigation of ancient environments. In this paper I present a novel approach to reveal how seasonal an ancient sea was by measuring the amount of variation in zooid size within colonies of fossil cheilostome bryozoans.