Our first several days were spent on Barro Colorado Island and focused on the incredible diversity of tropical flora. For example, a recent paper estimated that the number of tropical tree species alone may be as many as 53,000 (Ferry Slik et al. 2015). Temperate forests have far fewer species, despite in many situations having more land area available. In many places in the tropics, closely related species can be found living in close proximity to one another. This creates an evolutionary paradox. Since closely related species are likely to have similar ecological requirements and thus occupy similar niches, we would expect one species to outcompete the other and become the exclusive member of the local community. Since this is not what happens, there must be a mechanism (or mechanisms) by which these species are able to coexist. Exploitation of alternative chemical space, leading to differential resistance to herbivores, is an attractive hypothesis that could explain this paradox and promote diversification of tropical plant species, and studies are underway to test it.
View from BCI.
Our time on Barro Colorado also introduced us to diversity of vertebrate species including primates and birds. Hiking through the forest in search of birds and capuchin monkeys gave me an appreciation for the difficulty of studying tropical animals. To start with, the animals can be hard to spot in the low light and thick tangles of vegetation that can occur in the understory. Additionally, they are rarely near the trail where it would be easiest to observe them. Trekking through the vegetation of Barro Colorado was quite difficult for me in the dry season, which would seem to be the easiest time. Tracking animals in the wet season, or in more densely vegetated forests, must be exponentially harder, and truly gives you an appreciation for the dedication and passion of the people who study them. Talking with researchers on our hikes has also helped me to understand how little is actually known about tropical organisms and some the many unique scientific challenges and opportunities that tropical ecosystems represent.
Vegetation of BCI and a resident agouti.
I was also struck by how important it can be to recognize that our approach to a problem is filtered through both our scientific knowledge and our cultural background. A large amount of the early scientific literature was written by authors from a North American or European background, and, from reading this literature and living in American society, we may be in the habit of seeing North American ecology as the baseline, and tropical ecology as the exception. But, as Christine Rhiel pointed out in reference to investigating the mechanisms underlying differential clutch size between temperate band tropical birds, approaching a problem with a temperate=normal mindset can make certain questions more difficult to answer. I will try to keep this in mind as we continue in the course.
The turnip-tailed gecko (Thecadactylus rapicauda) was a common sight on the buildings of BCI.
Ferry Slik, J.W. 2015. An estimate of the number of tropical tree species. Proceedings of the National Academy of Sciences of the United States of America. 112(24):7472–7477.