The Rise of C4 Plants

By Kevin McFadden

Imagine a happy place where you’re laying out in the Caribbean sunshine on a beach with a mojito in hand. You jump into the crystal clear blue bathwater of the sea, then you lay down in your chair under an umbrella and doze off thinking about delicate and beautiful New England winters… you wake up and look over at a little saltbush that hasn’t been consuming delicious beverages, cooling off in the sea or taken cover under an umbrella to take a nap. In fact, this poor plant hasn’t moved an inch. First off, let’s hold the phone here. The truth is, this plant is loving life and it took over 3 billion years of evolution for it to become so happy! Saltbush is one of many plants who has adapted to warm, sunny, and dry conditions.

Long ago, when atmospheric carbon dioxide levels were high and oxygen levels were low, an enzyme called Rubisco started being made in plants which is an important driver in the Calvin cycle, without which food can not be made. Continue reading

Dendrochronology: the trees tell stories too

By Erin Hayes-Pontius

To add to the seemingly never-ending list of proxies paleoecologists use to study the past, here’s another one: trees. If you have been following this blog for a little while, you probably read about what pollen can tell us, but using the trees themselves, rather than their pollen, can tell an entirely different story. Studying the pollen that accumulates in lake sediments has the distinct advantage of providing a record that is as old as the lake itself, which can sometimes be up to millions of years old. However, because of how long it takes lake sediments to accumulate, we cannot always be very confident of the date a particular layer of sediment represents. In contrast, trees generally provide a much shorter record than pollen, but because of their annual rings, give us an annual record to work with.

treecore

A device used to extract thin cores from trees (Wikimedia Commons: Beentree 2006).

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Extinction through time; were humans a factor in the past, too?

By Gloria Lima

It’s known that humans have played a large role in the extinction of many organisms. But does this mean we are the only cause? How is it possible for us to tell if we are the only factor or if we simply play a large role in the whole ordeal? Paleoecology offers clues, starting with which organisms went extinct, and which survived. We can look to paleontological data for patterns, like the body size of extinct species, or how those species interacted with their habitats.  By comparing fossil and modern animals, it is then possible to see how the organisms in the past interacted with their environments, by looking at the ecology of their surviving relatives.

picture one

Image courtesy of Smithsonian Magazine.

Much of what we know about extinction comes from carbon dating the remains of extinct animals. An example is seen in the article “Patterns of generic extinction in the fossil record.” The authors looked at many fossils from a wide range of genera to see if there was a common pattern in extinction among the organisms. If there was a trend, it’s then possible to see whether the environment played a large role in the extinction, compared to the biology of the organisms. If so, this could mean that the climate caused a change in the environment before the organisms were able to adapt to it. Continue reading

Small but Mighty: Insects as Proxies

By Wayne Heideman

Insects have been on the Earth for a long time and their presence can affect their surrounding environment. It is important to look at insects in the past as they can provide us with insight on how they can act in the present and in the future. In a paleoecological sense, insects can be studied in a number of ways. One way is to look at plant-insect interactions through plant fossils (herbivory) and peatlands (habitat). Another technique is through amber and observing the insect in a snapshot of time. Lastly, sediment cores in lakes can capture insect presence, notably Chironomidae (non-biting midges) larvae and Coleoptera (beetles). All three are viable means of observing past insect use but they all have their strengths and weaknesses which should be assessed before using a specific method.

A picture of three different types of insect damage on plants. A) Shows a frass trail as well as an oviposition site marked by the arrow. B) Shows a high degree of herbivory, only leaving fine veins and C) shows areas of leaf case shelter sites. From Wilf 2008.

A picture of three different types of insect damage on plants. A) Shows a frass trail as well as an oviposition site marked by the arrow. B) Shows a high degree of herbivory, only leaving fine veins and C) shows areas of leaf case shelter sites. From Wilf 2008.

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Through the looking glass: how diatoms can reconstruct wind

By Kelsey

Few object are more beautiful than the minute siliceous cases of the diatomaceae: were these created that they might be examined and admired under the high powers of the microscope? ~ Charles Darwin

As Darwin remarks, diatoms are beautiful.  They have unique, intricate cell walls that help in their identification, because in addition to their beauty, they can tell a lot about past environmental conditions.  My research uses diatoms as a proxy (a preserved item that acts as a ‘natural archive,’ capable of telling us something about climate in the past) to explore past environmental conditions in lakes.  Diatoms are a type of single celled organisms called algae.  These organisms are found in many wet environments including soils, but I focus on diatoms in lakes.

Figure 1: Images of various species of diatoms. Image from Wikimedia Commons.

Figure 1: Images of various species of diatoms. Image from Wikimedia Commons.

Diatoms are unique from other types of algae because they have siliceous or glass-like cell walls, and therefore are well preserved in lake sediments.  This makes them good proxies of past climates.  Additionally, diatom species, like other algae have a variety of environmental preferences.  These preferences can range from mixed or stable water conditions, to high nutrient or light levels and provide the basis for climate inferences. Continue reading

The Hyper-Disease Hypothesis: Did Humans Bring About Doomsday for the Megafauna of the Pleistocene?

By Erika Lyon

It is a concern that we are entering Earth’s 6th mass extinction.  Mass extinctions occur when a large number of species die off in a short amount of time relative to background extinction rates (to read more about extinctions, click here).   Some of the major questions being asked include what are the mechanisms behind extinction events and could humans possibly cause a mass extinction?  One of the more recent extinctions in geologic time that may provide some insight into these questions is the Pleistocene megafaunal extinction that occurred in North America.  Three hypotheses have been made on the cause of the Pleistocene extinction, which include: 1) vegetation and climate change, 2) over-hunting by humans, and 3) the introduction of disease brought into North America by humans, the last of which is known as the hyper-disease hypothesis (MacPhee and Marx 1997; Lyons et al. 2004).  Continue reading

Tree migrations: a matter of scale

By Benjamin Seliger

In everyday life, trees may appear as stationary, permanent fixtures of the landscape, but in reality they are far from it. I will argue that all trees are constantly migrating, and summarize the means by which they do so in this post.

When I tell people I study tree migration, I often get funny looks. After all, how can an organism that cannot even move migrate? The answer to this, like many other phenomena in ecology, is time. Every year, mature trees release thousands of seeds in all directions, and when one of those seeds grows into an adult in a place where others of its own kind were not growing before, the species is migrating. Note that this perspective of migration is not limited to the cyclical movement of animals with the seasons, but rather an adjustment of a species’ range to preferred conditions as climate changes. I will refer to the latter as a range migration and the former as a seasonal migration. The two definitions are really explaining the same process at different scales; seasonal migration being the movement of individuals within their lifespan, and range migration as the movement of populations over the course of multiple generations. The end result for either definition is all the members of a species living in a different place than they did previously due to a change in environmental conditions. Continue reading

What proxies can tell us about drought

By Kelsey

We are all familiar with the images.  The barren landscape.  Brown, dead vegetation spanning as far as the eye can see.  Lakes and rivers shrinking in size, their relict banks cracked and dry.

These dryspells or droughts can last from days to years and they occur when a region receives below average precipitation.  Droughts are generally said to arise from insufficient precipitation amounts over an extended period of time.  This shortage in precipitation occurs typically in one season or more, and results in a water shortage for an environmental region.  The impact of the drought arises from the interaction between the natural events (less precipitation than expected) and the demand on the water supply (both from the environment and humans), which can exacerbate the impacts of the drought. Because of these factors that can influence the magnitude of the drought, they need to be taken into consideration when working to define a drought (National Drought and Mitigation Center). Frequently the definitions can vary from location to location as certain areas are less adapted to low water conditions than others.  But it can also dependent on timing.  For example, in the desert a month without rain doesn’t have the same effect as it would in the rainforest.  However, if the month without rain in the desert came during the period designated as the rainy season, the impacts would be drastically different.

Depending on how long these dryspells last there can be a huge impact on the ecosystem and economies associated with them.  One prime example is the Dust Bowl.  Continue reading

Humans: where we have been and where are we going

By Gloria Lima

When looking at how humans have change throughout the year one may simply think in the past hundred years or maybe even a bit further to medieval times or to ancient Rome and Greece. But nonetheless, humans have been around for longer than that– try around 100,000 years! To understand the idea that human ancestors may have been around longer than today’s humans have though is a bit mind blowing.  To think that we have been on this earth for that long is pretty amazing.  Continue reading

Putting waste to work: Bat guano & packrat middens as sources for ecological proxies

By Griffin Dill

Paleoecology is a discipline deeply rooted in the use of proxies. In order to develop an understanding of past ecosystems and climatic events, paleoecologists utilize a number of biological proxies, including pollen data, plant macrofossils, diatoms, charcoal particles, and isotope geochemistry, to name a few. These proxies provide researchers with quantitative data that can be used to examine a myriad of environmental variables and reconstruct ancient ecological communities. Proxies can be obtained from a variety of sources, but are commonly acquired from lake sediments and peat bog profiles and to a lesser extent marine sediments. As research into the paleoecological record intensifies, additional proxies and previously untapped proxy sources are sought. An often underappreciated source of ecological data is now providing additional information to paleoecologists: animal waste. Continue reading