Biological Connectivity and Complexity

Biology is more than just science. While an analytical perspective is important in any scientific field, biology is unique in its interconnectivity. For example, the human body is a symphony of chemical reactions that build complex processes such as metabolism, respiration, and circulation; each one is useless without the other. In the same way, the immense biodiversity of a tropical rainforest is interconnected in a web of complex relationships that ebb and flow in a way that turns a single shift in one organism into a cascade of changes in the entire ecosystem.

 

 

My first true introduction to the beauty and complexity of a tropical rainforest was during our guided nature hike on our first full day at La Selva. The three hour hike, while taxing from the heat and humidity, absolutely flew by. With a guide well-versed in tropical ecology, I saw more than I even thought possible. What I found most striking was our guide’s deep understanding of our environment and how he used it to identify animals. When walking through the forest, it’s important to use all of your senses to spot wildlife. For example, you can listen for calls of birds and frogs and follow the sound, smell the musk of a monkey in a nearby tree, or identify the type of trees three-toed sloths spend most of their time in. By the end of the hike, I was much more in tune with the forest around me, and also had a better understanding of the creatures that live at La Selva and how they interact.

From there, I’ve gained insight into a plethora of biological processes across many species. From night hikes to bird hikes and even during data collection, I’ve learned about the inner workings of this tropical ecosystem. Below, I’ve outlined a few of the processes I find most fascinating.

Camouflage

Take a look at the picture below, and tell me what you see…

Just a tree, right? At first, I couldn’t even remember why I took this picture. But as my finger hovered over the delete button, I spotted it: this is an image of a young iguana sunning itself in a tree. There are plenty more images in my camera roll exactly like this, because the animals of the tropical rain forest are masters of camouflage. They use a variety of tactics to blend in to the environments that they spend the most time in. Iguanas are arboreal animals, their coloring blends in perfectly to trees. However, they do change color for a month during mating season to attract mates. Their bright orange colors, while useful for reproduction, put them at greater risk of predation. It’s an ever-evolving balance between reproduction and survival in the wild.

Parasitism

On our bird hike, we learned about oropendola birds. Beautiful in coloring and call, these large birds are one of my favorites. However, Jake was convinced they’re stupid. When questioned, he explained that our guide said the birds are often victims of bird parasitism, in which another bird such as the cow bird or cuckoo bird lays their own egg in an oropendola nest. He wondered how they could possibly not notice another egg in their nest, and our guide explained that most of the oropendola’s energy is invested in protecting the nest, not investigating its contents.

With these parasite birds, it’s common for the invading baby to reduce the survival rate of the other babies. Strategies range from pushing other babies out of the nest to outcompeting them for food. Either way, the strategy is effective enough to fool the oropendola, a species which I personally find to be highly intelligent.

Reproductive Strategies

Reproduction is one of the most fascinating topics to study in the tropical rainforest setting, as species often face dilemmas between survival efficiency and reproductive appeal. For example, male birds are often colorful to draw female attention for mating, while the females are more muted to ensure their survival and ability to care for offspring. Therefore, the male birds that are most sexually appealing are also the most at-risk for predation.

Another interesting reproductive strategy is the variety of approaches that plants take. Seedlings often cannot survive in close proximity to the mature parent plant, so they must be scattered in order to increase their odds. Some use wind to disperse their seeds, others use water, and yet others rely on animals to do the work, as plants are sedentary by nature. The animal strategy is common for fruiting trees, which expend energy creating fruit for primates and birds to eat. These organisms often travel long distances before defecating, ensuring a higher chance for reproductive success. The wind strategy is a more common strategy, as plants can produce smaller seeds and therefore expend less energy. Regardless of the reproductive strategy employed by a plant, it all seems much simpler than the complex mating rituals employed by humans.

Throughout my time at La Selva, I’ve noticed an overarching emphasis on the fauna over the flora. ‘Charismatic megafauna’ such as primates, sloths, and peccaries catch the attention of the majority while birds, insects, serpents, and amphibians hold the attention of a few, but often plant biodiversity is the most overlooked. For instance, I’m the only student in our group that chose a plant to do my species presentation over. And while they’re often portrayed as a passive member of the tropical rainforest just waiting to be eaten or used for wildlife needs, plants actually have complex relationships with each other and the fauna around them. For example, they erect defense mechanisms to protect against being consumed, compete with other plants for resources, and even develop mutualistic relationships. The latter is the topic of my research, in which Laurel and I are asking “How does microclimate affect the abundance and biodiversity of epiphytes?”

If you’re thinking “Hang on, what are you talking about?”…

epiphyte –  a plant that grows on another plant and has roots that never touch the ground (ex. vines aren’t an epiphyte, because they eventually connect to the forest floor)

bromeliad – a type of epiphyte that has a shape which allows it to catch water and debris (a member of the pineapple family)

In this study, we’re taking a series of climate measurements throughout the forest to gauge the microclimate, or weather patterns immediately surrounding, trees. We plan to compare this data with the percent coverage of both total epiphytes and bromeliads found on a cohort of around 50 trees. The hope is to find a connection between the biodiversity of epiphytes and the environments they’re found in. This should help us understand how climate change may reduce biodiversity of epiphytes and therefore biodiversity of the forest ecosystem as whole as the planet warms. We hypothesize that, as bromeliads in particular thrive in hotter and wetter climates, that they may be more competitive as the climate warms and push out other epiphyte species, taking a dominant place in the forest.

Just as my understanding of tropical nature has grown, so has my understanding of those around me. It’s incredible what just a few days of 24/7 contact with a group of 12 strangers can do. Just 5.5 days into this trip, we’ve forged relationships that make it feel as though we’ve known each other for much longer. Every day is filled with laughter and comradery as our shared experiences in an unfamiliar place bring us closer. While the course load and research requirements can often be taxing, leaving little room for downtime (and sometimes even sleep), we find the time to have fun and even celebrate birthdays! Spending time with a group of such amazing people makes me ever-so excited for what’s to come.