Why do we still know so little about common species?

South Florida is a wild place for lizards. And at the moment, as the region’s most abundant native lizard, life sucks for the American green anole Anolis carolinensis.

In the recent past a wealth of invasions have occurred from exotic Caribbean Anolis leading to the establishment of up to 10 non-native species around the Miami area, annually creeping further outwards towards the Everglades. The effect of congenerics on American green anoles has been well studied; the presence of an ecologically similar competitor – such as the now widespread Cuban brown anole Anolis sagrei (Fig. 2) – has forced them higher up into the trees and off the ground.

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Fig 1. Range of the American green anole Anolis carolinensis in south-eastern United States. Different colours represent genetically distinct populations – from Campbell-Staton et. al. 2012.

However, the majority of these studies have been conducted in spatially explicit areas, that is to say on experimental islands. These have merits in themselves; it allows control of many assumptions which may skew your observations. For example, in continuous space one may expect species A to simply move away from species B if spatially out-competed, however islands offer the advantage of forced interactions meaning resource partitioning and habitat shifts may be more easily observed.

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Figure 2. An adult male Cuban brown anole Anolis sagrei (Photo: J Stroud)

Isolated from all other Anolis since the pre-Pleistocene, the American green anole has had it pretty easy so far. They range from the southernmost tip of the USA, Key West, north to Tennessee, and west to mid-Texas (Fig 1). However the rapid range expansion of introduced species, pioneered by the previously mentioned Cuban brown anole, has caused the anecdotal decline of green anoles in the urban and suburban areas in south Florida. Whether this population decline is true, or a shift to arboreality has affected detection rates is unclear. What is clear is that the invasion by the exotic Anolis do not seem to be limited by habitat factors – yet.

Deep in the sawgrass plains of the Everglades the green anole still persists, for the time being at least, in allopatry. It’s ecology there is almost a complete mystery. Despite extensive research on the ecosystem, we know next to nothing about this species’ ecology here. Throughout the rest of its range a wealth of literature exists, however for populations in the Everglades we are still unclear on fundamental aspects of their ecology; habitat choice, diet, reproductive biology, sleeping sites or daily/seasonal activity patterns – all axes along which competitors may cause disruption.

And this is something that always puzzles me in ecological research – often we try to run before we can walk. Natural history is the basis of much of ecology, however in the present world of big science and meta-everything, this can often get overlooked.

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Figure 3. For example, nectivory in American green anoles Anolis carolinensis is a relatively undocumented and still unstudied feeding behaviour whose implications are not well understood (photo: James Duquesnel, courtesy of: S. Koptur)

The potential ecological impacts of exotic anoles on the native green anole in the Everglades are unknown, and as it stands any hypothesis would be theoretical at best. However as scientists, we must remember that some of the greatest theories have arisen from natural observations. Where would evolution be without Darwin’s twitching?

Not only does the invasion expansion of Caribbean anoles present a native species conservation issue, but the potential for a large increase in terrestrial insectivores seems a topic of interest that should merit some thought for a wide range of ecologists. The Cuban brown anole is already present at every car park along the Everglades road to Flamingo, likely transported unwittingly via humans. How long we have before they begin to disperse may just be a question of time.

I encourage all of us that have the privilege to spend time outdoors in south Florida to collect as many field notes and natural history data as possible. In this world of change, the global scale effects of climatic events and warming remain unresolved, much like the more regionalised effects of human management. The importance of these data are clear, but often overlooked; they describe reality. So I return to my original question – with such a rich history of research in the Everglades why do we still know so little about the regions most charismatic lizard?

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Sea level rise and the dangers of living in coastal cities

The new Intergovernmental Panel on Climate Change’s (IPCC) 5th assessment report has upgraded their predictive models to increase the reliability and confidence of future climate change scenarios. As a temporary resident of Miami, which is largely at or just above sea level, I was particularly interested in the new sea level rise projections. The IPCC is now 95% confident that sea levels will rise somewhere between 0.25 to 1 meter (~1 to 3 feet) by the year 2100. This may not sound like a lot but if we consider that many of the world’s largest cities are located at or below sea level then the repercussions of even a 1 ft increase in sea level rise can be devastating.

Projections of global mean sea level rise over the 21st century relative to 1986–2005 from the combination of the CMIP5 ensemble with process-based models, for RCP2.6 and RCP8.5. The assessed likely range is shown as a shaded band. The assessed likely ranges for the mean over the period 2081–2100 for all RCP scenarios are given as coloured vertical bars, with the corresponding median value given as a horizontal line. For further technical details see the Technical Summary Supplementary Material

Projections of global mean sea level rise over the 21st century relative to 1986–2005 from
the combination of the CMIP5 ensemble with process-based models, for RCP2.6 and RCP8.5. The assessed likely range is shown as a shaded band. The assessed likely ranges for the mean over the period 2081–2100 for all RCP scenarios are given as coloured vertical bars, with the corresponding median value given as a horizontal line. For further technical details see the Technical Summary Supplementary Material

According to the Organization for Economic Co-operation and Development’s 2007 report on coastal flooding, Miami ranks as the number 9 city worldwide in terms of population exposed to coastal flooding, but Miami is the number one ranked city in the US, followed by New York. For Miami alone it is expected that almost 4.8 million people will be affected by coastal flooding by 2070, but this number is a drop in the bucket when we consider that the top 8 cities on this list, all outside of the US, project having a combined population of 71+ million people affected by coastal flooding related to sea level rise.

What happens when 71 million or even 4 million people are displaced by sea level rise? Rolling Stone provides one possible scenario in this recently published article that simulates what might happen in Miami. The article paints a grim picture for South Florida but I imagine situations will be much worse in less economically developed countries such as India, Bangladesh, and Thailand. The social unrest and economic losses due to even modest increases in sea level are staggering. If we consider only the top 20 cities worldwide (Miami is #1) in terms of assets exposed to coastal flooding, we are looking at a $3 trillion global loss by 2070. This was about 5% of global GDP in 2005.

Millions of displaced Bangkok residents went without food or clean water for weeks after devastating floods swept through the city in 2011. Photo courtesy of washingtonpost.com

Millions of displaced Bangkok residents went without food or clean water for weeks after devastating floods swept through the city in 2011. Photo courtesy of washingtonpost.com

These projections do not even begin to tell the story of how our ecosystems and the services those systems provide to humans will be changed. Coastal wetlands, which protect us from large storm surges will be submerged and likely lost because they cannot migrate inshore due to human development. Coral reefs, which depend on light for growth and serve as nurseries for several economically important fish species, will be further submerged, receiving less light and degrading over time. At coastal cities, salt water is already intruding into freshwater aquifers, contaminating our drinking water and this trend will only get worse with further rises in sea level.

No matter how you put it sea level is rising and the negative aspects of sea level rise are downright frightening. My advise, buy property in Colorado.

A cool but scary webpage let’s you play around with different sea level scenarios for cities in the US. I encourage you to go to this webpage and see how your city or favorite beach vacation spot fares against rising sea levels. However, results should be interpreted with caution as population estimates are based only on the city population itself and ignores the greater metropolitan area, which means actual number of people impacted by sea level are much greater than displayed on the webpage.

 

 

 

Q&A with some authors of “Hyperdominance in the Amazonian Tree Flora”

A new article has just been published in Science entitled “Hyperdominance in the Amazonian Tree Flora” by Hans ter Steege and an army of 100+ authors (including yours truly). Rather than summarizing the article, I am going to share responses by me and two other coauthors (Miles Silman and Paul Fine) to a couple of questions asked of us by a journalist (Deborah Osae-Oppong of the Chicago Field Museum) writing up a press release about the article.

1. In your opinion, what is the most remarkable find in this study?

Ken Feeley: One of the most remarkable and important outcomes of this study is the revelation of how little we actually know about the Amazon, and by extension, other tropical forests worldwide. This study is attempting to answer incredibly basic questions: How many trees are there in the Amazon? How many species of tree are there? What are the most common tree species? How many rare species are there? To even attempt to answer these questions the authors had to work for many years to gather immense amounts of data from across huge expanses of remote and biologically uncharted territories. Even with this unprecedented data set in hand, we are really only able to take what amount to very educated guesses at most of these questions. We now have an idea of how many tree species are in the Amazon and how many of them are common or rare, but we still know next to nothing about those species.

Miles Silman: The most remarkable findings of this study are two-fold, really. And it is that Amazonian forests are spectacularly diverse and monotonous at the same time. There may be up to 16,000 species of trees in the Amazon, yet half of the individual trees one encounters comes from just over 1% of those species.

Paul Fine: For decades, the conventional wisdom was that in Neotropical rainforests it was difficult to find two individuals of the same species in the same forest. The new study shows that this is not the case for the few hundred dominant species but only for the thousands or rarer species.

2. What are the implications of the finding that the so-called “hyper-dominant” species account for half of all the trees in the Amazon?

Ken Feeley: Another hugely important finding of the study is that most of the individual trees in the Amazon actually come from just a relatively small number of hyper-dominant species. As such, it may actually be plausible that we can one day gain a reasonable understanding of how the Amazon works and perhaps more importantly how it will or will not work in the future. This is because we can now focus our research efforts on the hyper-dominant species; once we learn their ecology we will have at least half the pieces needed to put together the puzzle that is the Amazon.

Miles Silman: What it means is that (to a first approximation) half of the ecosystem services that we get from trees comes from just over a percent of the species. At first blush one would think it would make it easier to understand things like carbon cycling in Amazonian forests, and ecosystem responses to global change. I see a danger in focusing too much on the hyperdominants, though. Forests are more than collections of trees. Around 90% of the tree species in Amazonia are obligately tied to animals for pollination and seed dispersal. And, conversely, these animals are tied to the trees. Are the hyper-dominants alone enough to support the vast animal biodiversity of the Amazon, and to keep the ecosystem functioning? Or are the other 98% of tree species, even the very rare species, playing important roles in the web of interactions in the world’s most diverse forest, without which the whole system collapses?

Paul Fine: For me, it suggests exciting new research programs to uncover why the “hyper-dominant” species are so common? To what extent does biogeographical history play a role? Do hyperdominants have some set of successful traits? Defenses against natural enemies?

3. Can you explain, in your own words, the phenomenon of “dark biodiversity”, and the consequences that has for future endeavors into Amazonia?

Ken Feeley: While thanks to this study we now know that the Amazon is dominated by a relatively few super common species, we also now know that there are thousands of extremely rare species hiding out there. Indeed it is these rare species that actually account for most of the biodiversity that the Amazon is so famous for. By their very nature, by the very fact that they are rare, these thousands of species present what may be an intractable problem for ecologists and conservation biologists. Rare species are hard to find, they are hard to recognize, and they offer very small sample sizes making it extremely difficult to ever shed a light on this “dark biodiversity” and learn learn about how rare species work and how they may (or may not) be threatened by climate change, deforestation or any of the other myriad of anthropogenic threats that loom over the Amazon. If we ever hope to understand and protect rare species, and hence the full diversity of the tropical rainforest, we are going to need a lot more than just a 1000+ tree plots

Miles Silman: One of the things that this study really drives home is biodiversity’s dark matter. 99.9% of the individual trees out there hold just a third of the species diversity. A full two-thirds of the tree species in the Amazon are rarer than needles in a haystack, representing just over a tenth of a percent of the total individuals. It is akin to the situation in physics, where we know there is a lot of matter in the universe that we can’t see, and we know it is important, but it is devilishly hard to detect. So, we’re in the situation where we know there is immense biodiversity out there and that we might never be able to detect it. This raises all sorts of questions: Can species really exist at that low a density? What are the limits to small populations? Are the rare species on the way out? Or are they up-and-coming new species? And, as conservationists, do we even try to detect biodiversity’s dark matter?

Paul Fine: We desperately need more investment into the systematics and taxonomy of tropical trees. Most of these rare species are unidentified morphospecies — and these species likely hold the key to understanding the history of Neotropical tree biodiversity and helping to predict how this diversity may change under global climate change.

Forest fragmentation leads to rapid species extinctions

A recent study, lead authored by Luke Gibson from David Bickford’s lab at the National University of Singapore, has documented the dramatic decline in small mammal diversity as a result of human-mediated habitat fragmentation. The Khao Sok national park, in southern Thailand, has created an island matrix of limestone karst peaks (see below) as a result of flooding from the construction of the Ratchaprapha dam.

543713_10150848904474021_574689551_nPhoto: JStroud (2011)

The rate of global tropical forest felling and fragmentation continues to increase, and a key question in conservation science is how rapidly do species disappear from forest fragments. If we are able to evaluate this then it may be possible to create a time plan for mitigation, i.e. re-connection of habitat, to minimise extinctions.

Using a classical island biogeographic model on islands of various sizes, Gibson et. al. estimate that, on average, half of all species in each fragment were lost after ~13.9 years. They comment that these extinctions were probably expedited by an invasive rat species; the implications for which provide important contributions to other studies of invasion ecology.

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Gibson et. al. 2013

These results are particularly relevant to other fragmented forest landscapes and suggest that small fragments are potentially even more vulnerable to biodiversity loss than previously thought.

An Undergraduate’s Perspective

I would like to begin this blog post with a quick introduction about myself:  My name is Christine Pardo and I am a senior attending Florida International University in Miami, Florida. As an undergraduate pursuing a career in the fields of ecology and conservation, I have made it a goal of mine to have a myriad of experiences under my belt before I cross that threshold event into the “real world” otherwise known as graduation. In the summer of 2012 I spent three months as a volunteer with Dr. Kenneth Feeley and his graduate student Evan Rehm working in the Andean cloudforests of Manu National Park in southern Peru. This past summer, I participated in Harvard Forest’s Summer Research Program in Ecology supported through the National Science Foundation’s Research Experience for Undergraduates fellowship.

As a contributor to upwithclimate, I am going to blog a series of insights I have gained from those past experiences and more. I hope to accomplish two main goals from my series of blog posts. First, I want to actually bring to light the undergraduate perspective on a variety of topics related to pursuing a career in ecological research. Second and most importantly, I hope that my posts will serve as advice to anyone like myself who has decided during their undergraduate years to take the plunge into this truly amazing field.

My next few posts will highlight my most recent experience at Harvard Forest. I look forward with anticipation to begin this blogging project!

-Christine (cpard008@fiu.edu)

Collecting soil samples from Prospect Hill at Harvard Forest.

Collecting soil samples from Prospect Hill at Harvard Forest.