Ecology Meets Agriculture

This weekend, on our way back from the Galeta Marine Lab, we took a side trip across the Gatun Locks to a polyculture farm where they grow plantains and rice, as well as corn. What's special about this farm is their understanding of the life histories of plantains and rice and how they use it to minimize their pesticide use while increasing crop yield.

 

Ships waiting to leave the canal for the Caribbean

Walking to the plantation

Step 1: In the dry season, plant plantains.

Ready for planting

Step 2: Wait until the plantains are about a foot tall, then burn the field! Although this may sound crazy, the fire won’t damage the seeds under the ground, and when the plantains grow back they will have significantly less pathogens.

Step 3: Wait a bit, then plant the rice.

This staggering allows the plantains, which would naturally be outcompeted by rice, to grow large enough that they aren’t outcompeted. As well, the plantain leaves provide a shade canopy over the rice plants during the short dry spell around May [veranico?] which would cause considerable damage to unshaded rice plants. The biodiversity in the polyculture, especially since it is bordered by and occasionally interspersed with natural forest, also helps to reduce pathogen loads of each crop.

Thus, by simply understanding the life histories, yield is increased without harmful chemicals.

In the plantation learning its secrets

The view from the cornfield

Additionally: by rotating crops, and including legumes and other nitrogen fixers between rotations, the soil retains nutrients with minimal chemical fertilizers (such as in monoculture).

Harvested rice

The rice produced is primarily for the owner and workers, and sold to community members; but a proportion (~30%) is sold in a market. The rice seed gathered each year is also used primarily by the farm for the following year, but often sold to friends and other community members.

And in the nearby town of Achiote (where we stopped for lunch), we took the time to visit a coffee museum and try out the traditional method of processing coffee beans!

Coffee tree

Removing the husks

 

 

Coffee beans drying

Are eco-evolutionary dynamics stronger in the tropics?

This post is copied from my regular blog: http://ecoevoevoeco.blogspot.com/

Biodiversity is higher in the tropics. Terrestrial productivity is higher in the tropics. The pace of life is faster in the tropics. Mountain passes are higher in the tropics. The tropics are just bigger, faster, and stronger. So what about eco-evolutionary dynamics? Are they stronger in the tropics? A recent trip to Panama provided the motivation to speculate on this possibility.

Coati

Early in the trip, I visited the famous research site of Barro Colorado Island (BCI), where I was able – with my family – to see howler monkeys and all sorts of other wonders. Back at the town of Gamboa a few days later, I was called on to give a lecture to the “tropical boot camp” class that included graduate students from the McGill-STRI NEO program, the STRI-Indiana IGERT program, and Arizona State University. I decided to give my boiler-plate talk outlining a conceptual framework for eco-evolutionary dynamics because I figured most of the students would be ecologists and it would perhaps be worthwhile to encourage them to include an evolutionary perspective into their ecological thinking. 

A leaf cutter ant in the clutches of an ant lion (zoom in for a better view of the lion).

During the lecture, I set up several key questions facing the study of eco-evolutionary dynamics, one being the importance of evolution (e.g., changes in phenotypic traits) relative to other non-evolutionary ecological forces (e.g., precipitation, temperature, flooding) in shaping ecological dynamics at the population, community, and ecosystem levels. The standard work addressing this question at the population level is that comparing the effects of phenotypic traits (e.g., body mass) on the population growth rate of ungulates in Canada and Scotland in comparison to climate variables (e.g., rainfall, Pacific Decadal Oscillation). Remarkably, effects of the two causal forces (evolution versus ecology) are roughly the same in each study population, suggesting that phenotypic change is incredibly important to ecological dynamics. Halfway through explaining all of this, it began to strike me as silly to use an example from a temperature vertebrate while lecturing in a building situated on the borders of a verdant tropical rainforest. Why not use a tropical example – even if just for hypothetical illustration. 

Lounging capybaras

For some reason, my mind hit on howler monkeys. What effect, I posed as an example, would evolutionary changes in the phenotypes of howler monkeys have on the productivity or diversity of the BCI forest relative to the amount of rainfall. I had no idea of the answer, of course, which got me to wondering. Would eco-evolutionary dynamics be stronger or weaker in the tropics? It seems like an opportune time for some speculation. 

Millipede delight

Several properties might increase the strength of eco-evolutionary dynamics. (1) Faster rates of phenotypic change. Perhaps the tropics have faster rates owing to the more rapid pace of life, or perhaps not given their more stable environment. (2) When the species causing the ecological effects have large effects as individuals, such as in the case of keystone species. Perhaps the tropics have more of these (elephants!), or perhaps not given that many more species are present and so the effect of any single species (besides elephants) might be weaker. (3) When the species causing the ecological effects are very numerous (bacteria, viruses, and some insects and plants). The tropics likely have more such organisms given the overall greater productivity, or perhaps not given that so many species are present the effects of any one species – however numerous – might be swamped by all the other numerous species. (4) When feedbacks between ecology and evolution are stronger, such as when trait changes causes an ecological change that promotes (through selection) further changes in that trait. Perhaps the tropics have more feedbacks of this sort because the environment is not reset each year by winter and because  so many cool mutualisms are present, or perhaps not because the system can be reset by dry and wet seasons and because mutualisms in temperate regions might have stronger effects given the relative paucity of other species. So would we expect eco-evolutionary dynamics to be stronger or weaker in the tropics than in temperature regions given that effects seem to point in both directions in each case? 

Yummy dung

I suggest that evolutionary dynamics on the part of single species (i.e., effects of the evolution of a focal species on aggregate ecological variables) might be weaker in the tropics – simply because the countless other species dilute the effects of any one species. However, I also suggest that eco-evolutionary dynamics in aggregate (i.e., across all species) will be stronger in the tropics – because there are so many other species and interactions, because they have been for around longer, and because the environment is somewhat more stable. I also suggest that eco-evolutionary dynamics associated with phenotypic CHANGE might weaker in the tropics given that organisms have had more time to stabilize their adaptations and so might be less subject to contemporary phenotypic change. However, I also suggest that eco-evolutionary dynamics based on phenotypic STABILITY might be stronger in the tropics. By this I mean that the very stability seen in (some) tropical ecosystems is likely the result of continual ongoing evolutionary change. That is, so many interacting species are present that extinction and extirpation would be common were it not for constant, ongoing eco-evolutionary dynamics that maintain and improve adaptations and thereby stabilize population sizes. 

Spooning is universal

 Of course, this is all speculation provided in fun and on the fly but how can one not be motivated to think about the uniqueness of the tropics when watching your children feed leaf cutter ants to ant lions, go all warm and fuzzy over a howler monkey mom and baby spooning, marvel at a massive tarantula, try to get close to a capybara, watch dung beetles fight over a prime piece of monkey stink, sneak up on a group of foraging coatis, chase a praying mantis around and around a tree, and try to find toads that look like leaves.

Toads all over the place

Praying mantis

A very big tarantula at our door asking to come in.

Industrious wasps

More nature photos from the Panama trip are here: http://www.flickr.com/photos/andrew_hendry/sets/72157632543426268/

Deforestation & Its Social Impacts

by Divya Sharma

Much of what we have been learning about in this course is related to the collaboration between tropical field biology and genomics. Once we got to the Galeta Marine Lab, however, we were given a new topic of discussion: the interaction between social and ecological issues and, specifically, the role of deforestation.

Our first talk was given to us by Wayne Sousa, who spoke to us about the threats facing mangrove forests. These are forests that dominate low energy shorelines in the tropics and low latitude subtropics, in areas of high salinity. Mangrove forests are important ecosystems, in that they provide a habitat for many non-marine species, some of which are endangered, as well as a nursery habitat for edible fish and crustaceans. They protect against wind, flooding and storm surges. They moderate air temperature, stabilise shorelines and reduce erosion. They store carbon, and they trap terrestrial sediments and pollutants, thereby protecting coral reefs. They are also important economically, used for timber, charcoal and fisheries in Panama.

And yet, despite all these ecosystem services that they provide, mangrove forests are in decline worldwide. It is estimated that over 50% of the original global cover of mangroves has been lost, due to coastal development, clear-cutting, shrimp farming, mining, pollution and sea level rise. In Galeta, a large swath of mangrove forest was cleared to make way for a ship container yard, which was never even used. The subsequent negative effects of deforestation on drainage led to part of the surrounding forest being destroyed as well. One of the most obvious effects of mangrove habitat loss is the flooding of roads after rains in Galeta.

Our second talk was given by Nicole Gottdenker, who spoke about how deforestation impacts the ecology of Chagas disease. This illness is transmitted by blood-sucking bugs, and is a major cause of heart disease in Latin America. In her presentation, she explained how 83% of the Earth’s surface is under direct human influence, the ecological consequences of which are habitat fragmentation, pollution, changes in biogeochemical cycles, and more. In Panama, there have been high rates of deforestation in the past 40 years, in order to clear land for agriculture. About 73% of deforested land is due to pasture extension, which is often then converted into peri-urban developments and coconut plantations. Chagas disease has been described as a disease of poverty, because its transmission is facilitated by substandard housing. Bugs enter in through cracks, screenless windows, thatched roofs and adobe walls. It is believed that human encroachment on the forest has increased risk of transmission. Specifically, the Palma Real (royal palm) is key to the transmission of Chagas disease; it is found in areas of high human activity, as it is often left standing when the surrounding forest is removed, possibly because it is hard to cut and because its leaves are used for thatching. The crown of the Palma Real houses an entire insect community as well as birds, mammals and reptiles. The kissing bug is one such insect that transmits the disease to mammals and then to humans. Nicole’s team found that their hypothesis was correct: there is increased vector infection in fragmented forest landscapes.

So here we saw two examples of the social effects of deforestation: a loss of major ecosystem services, including a buffer against climate change and protection from flooding; and increased infection of Chagas disease. From these cases, as well as from others, it is clear that ecological and social issues are intertwined in complex ways. One cannot consider one issue without the other. Deforestation cannot be limited solely through the use of scientific arguments, but must involve an acknowledgement of social, economic and political issues. Interdisciplinary studies and collaboration between different fields are clearly necessary for the cooperation of locals and for concrete changes to occur.

Path through a mangrove forest in Galeta

Mangrove forest on the Caribbean coast

A palm tree where mangroves once stood

Visit to Galeta (Jan. 11- Jan. 12)

Last week we visited the Galeta Point Marine Lab and Education Center located in the province of Colón near the Atlantic entrance to the Panama Canal.  Galeta Point was initially intended to defend the Northern entrance to the Canal during World War II.  The laboratories were established in 1964 and the site has since been used for diverse research projects.  The coral reefs and mangroves surrounding Galeta offer opportunities to develop a wide range of projects.

On Friday we attended lectures by Drs. Wayne Sousa and Nicole Gottdenker.  Wayne Sousa focuses his research on the mechanisms that structure mangrove communities, and has developed his projects in Galeta for more than two decades.  At the moment he is examining the roles of herbivores, seed predators, and seed dispersal on the structure of mangrove forests.  Dr. Sousa has also focused a great deal of his work on the protection of Galeta’s mangrove forests in the face of development from adjacent ports.  Gross negligence and lack of foresight by local politicians and developers have resulted in the loss of several hectares of mangrove forests in Colón.  This reduction in mangrove cover caused by poor urban planning has resulted in flooding and erosion which threaten the lives of the inhabitants of Colón.  This problem is so severe in many areas that during recent storms dozens of houses collapsed as sinkholes formed bellow their foundations.

Nicole Gottdenker spoke about her research on Chagas disease.  Nicole has focused her work on the effects of deforestation on the prevalence of the Trypanosoma cruzi, the parasite that causes the disease.  Dr. Gottdenker’s results showed that prevalence of the parasite in the transmission vector, Rhodnius pallescens, was highest in deforested areas such as pastures.

The proximity of Galeta to the Panama Canal also make it an ideal location to study the role of the waterway in biological invasions.  Mark Torchin, my adviser, has devoted a large part of his research on this topic in particular.  A few examples include studying the survival of fouling organisms during transits, and examining how variations in biotic interactions between the Pacific and Caribbean coasts of Panama affect the establishment of non-native species.

Just Another Day in Gamboa

Although at first glance Gamboa, a small town in the middle of the canal zone with little in the way of entertainment, you don’t need to go far to find some uniquely stunning sights.

I can’t think of a better way to greet the morning than at the top of the Gamboa Rainforest Resort’s Observation Tower: 

The Tower

Getting there is half the fun. As you ascend the hill towards the tower, looking down isn’t a good idea – you may find yourself thinking of the stairs of Cirith Ungol.

Stairs leading to the tower

But it’s worth it. From the top of the tower all of Gamboa is at your fingertips, as Panamax and other  ships sail by on their 8-hour transit from the Pacific to Atlantic through one of the world’s greatest feats of engineering.

A ship passing Gamboa on the Panama Canal

And since Gamboa is located at the mouth of the Chagres River you can also gaze up the river and watch as the people of an indigenous Embera village go about their day. However, my favorite part of the tower is the opportunity to see some amazing wildlife:

 The Chagres River at sunrise (Credit: Erin Welsh, U of I)

Red-lored parrot (Amazona autumnalis) (Credit: Erin Welsh)

 

Keel-billed toucan (Ramphastos sulfuratus) (Credit: Erin Welsh)

As we continue through our course, not only are we meeting STRI staff scientists, but we are getting to know many influential STRI associates with an increasingly diverse range of topics. We started our academic day with talks from Jeff Brawn, a professor at the University of Illinois (one of the universities participating in the course), who has been studying the bird populations on Pipeline Road, an internationally recognized birding location, for over 25 years. His long-term study of the birds has established an incredible study site – where so much of the avian community dynamics have been studied within a structured grid network that we can begin to answer complex questions that would be impossible in a less understood community. So naturally we took the opportunity to take the class to the field, where we encountered a suite of animals including birds, mammals and insects in the evening hours.

3-toed sloth

 Semiplumbeous hawk (Leucopternis semiplumbeus)

White-faced capuchin (Cebus capucinus)

An enthusiastic talk by Stefan Schnitzer, from the University of Wisconsin, finished off an exciting day of exploration. Through his work at STRI Stefan has completely altered the way we see forests – simply by studying the woody vines, or lianas, found in every tropical rainforest.

Lianas climbing through the understory (Credit: Selina Ruzi, U of I)

On average, lianas represent 25% of the stems and 35% of the species in the forest; and even though they make up only 3% of the ground level area they have a huge effect, by reducing tree species richness, shade-tolerant tree recruitment and overall forest biomass. Lianas are peculiar in the forest, as they show some opposite trends from other woody plants. Due to their clonal reproduction they tend to be positively density dependent (they grow better close together); and their growth decreases as rainfall increases. While lianas seem to be rapidly taking over the forests, it’s not all doom-and-gloom. Lianas provide crucial connectivity between trees and perching area for just about every animal in the forest – from ants to ocelots.

X-Ray Vision: How to See through Trees

by Alex Tran

As a person who studies little obscure electric fish, I sometimes wonder why my fish get so little attention in comparison to the more charismatic and popular study organisms. But I shouldn't complain because that's probably nothing in comparison to what plant-studying folks deal with. To them, biologists probably seem to be ignoring plants and instead being obsessed with animals. Now that must be nowhere near what mycologists feel. An entire kingdom severely underrepresented in the scientific community. You'll find the odd mycologist here and there, and luckily for STRI they found Greg Gilbert.

Greg Gilbert and a fungus axe.

We had the pleasure of having Greg as a lecturer during our stay at BCI. He started off by giving us a primer on fungi, where we learned about things such as heart rot in trees (also butt rot). After an initial infection through the roots of the tree, the fungi can reach the heart of the tree and start a slow digestion process that takes years. With its core eaten away, the tree, hollow and structurally weak, snaps and dies. To answer the remaining mysteries of this process, such as which trees are more susceptible to these infections, or how prevalent fungal pathogens are, or how specific are fungal pathogens to their hosts, we need someone like Greg to come in and show us how to see through trees. 

Step 1. Select tree of choice.

Step 2. Look inside tree. Tadaaa!

Maybe I simplified step 2 a bit. It essentially involves using a hammer, an even fancier digital hammer, twelve flattened thumbtacks and the coolest biggest digital calliper. Unfortunately I don't have any images of it so just imagine giant tweezers with buttons, bluetooth, and independently moving arms. After selecting the tree and measuring its perimeter, we hammered down 12 evenly spaced thumbtacks around the tree. Then, using the calliper, we measured distances between thumbtack pairs. Meanwhile, on an automated computer software, each of these distances was used to construct a digital cross-section of the target tree. Now that we had the overall shape, we used sonic and electric impedance tomography to see inside the tree. 

Hammer.

Twelve thumbtacks placed around the tree.

Let's start with sonic tomography. If a tree is hollow, sonic vibrations require more time to pass through the tree and reach the other side. Using a hammer, this time the fancier digital one, we smacked smacked thumbtacks one by one while the software recorded the exact time it took for the sound of impact to reach each of the other thumbtacks. Knowing the distance between thumbtacks and the time it took for sound to travel, the computer software determines whether the space between the tacks is dense or hollow. This information is compiled and a few moments later, an image of the inside of the trunk is generated. In our tree, evidence of a fungal pathogen infection was manifested as a large hole in the tree's cross-section. 

Fancier hammer.

Owen smacking one of the 12 tacks.

Electrical impedance tomography.

Results of our electrical impedance tomography.

With electric impedance tomography, we are seeing through the tree not by using sound but rather current. Although it may seem like we're trying to blow the tree up, we're calculating the resistance between each tack pairs, which will give us an idea of the water content distribution in the tree. This technique allows us to distinguish cavities from wet diseased wood. The two cutting-edge techniques, often used in conjunction, will allow scientists like Greg Gilbert to understand how fungal pathogens are affecting different forest tree diversity.  

Greg Gilbert analyzing tomographies with students.