Fine's Lab:

"Growing up, I was really into birds," says IB professor and tropical biologist Paul Fine. "I got pretty good at being able to identify most of the birds where I was from, in Michigan." But that changed when Fine, as a Berkeley undergrad, went to Costa Rica and was introduced to the birds and the biodiversity of the tropics.
"I found it to be just mind blowing," he says. He recognized some of the birds he'd seen in Michigan, because they were migrants, spending their winter in Central America. But there were dozens of bird species that were new to him. "I was curious from that moment on why were there so many different kinds of living things." That curiosity drives Fine's research today, which focuses on the evolution and maintenance of biodiversity. But he doesn't study birds anymore. Looking around the forests, Fine realized that there were "so many kinds of birds because there were so many different foods they were eating. It really comes down to the plants."

Fine studies habitat specialization in the Amazonian rainforests of Peru, where patches of nutrient-poor white sand are like islands in an ocean of dark, nutrient-rich clay soil. Walking through the forest, it is very easy to see the delineation between the two soil types thanks, in part, to ground-dwelling cicadas, which Fine calls "my soil samplers." They burrow into the soil and make cones that stick out above the leaf litter. In the clay forests, says Fine, there are "nice little perfect cylindrical chimneys sticking out of the ground." But in the white sand areas, the cicadas' cones are smaller, "they're just these little sand lumps."

The two habitats are also home to entirely different species of trees. Most of the species that live in the white sand patches are endemics--they grow in the white sand habitat and nowhere else. The clay soils host other species of trees, most of which do not grow on white sands. Because species composition differs with habitat, Fine thought this system would be perfect for studying the evolution of habitat specialization.

Fine wondered whether white sand specialization arose once or multiple times. This question is important to evolutionary biologists: if white sand specialization evolved multiple times, then habitat preference plays an important role in speciation and diversification. And, says Fine, multiple separate speciation events are "multiple replicates of the same evolutionary processes."

Fine focused on one lineage of plants, the Burseraceae. This group includes frankincense and myrrh and is known for its production of terpenes, which give burning incense its characteristic smell. There are almost 50 species from the Burseraceae family in the northern Peruvian Amazon. Some species in this family live in white sand, and other species live in clay soil.

If the species that live in white sand are each other's closest relatives, then white sand specialization evolved only once, after which the lineage diversified. This means the factors that influenced their diversification were probably not related to soil type heterogeneity. But if the white sand specialists are not very closely related, then the specialization evolved multiple times, as multiple species independently colonized white sand habitats. If this were the case, soil type played an important and active role in diversification.

Fine collected samples from the trees and used their DNA sequences to create a phylogeny -- an evolutionary tree that shows how the species are related. The Burseraceae phylogeny showed that white sand specialization has indeed evolved multiple times, suggesting that the heterogeneous soil types in the region are directly involved in the diversification process.

Next, Fine wanted to know how white sand specialists differ from their relatives living on clay soils. White sand specialists tend to grow more slowly, because nutrients are in short supply. They are also more heavily defended against herbivores; "if they lose a bit of leaf material, it is really hard to replace, since they're growing in low nutrient soil," says Fine.

To see how soil type affects the growth of both white sand and clay soil species, Fine did a reciprocal transplant experiment. He moved seedlings from white sand to clay soil, and vice versa. To determine the effect of herbivores, like insects and grazing mammals, he put half of the seedlings in cages with nylon netting so they wouldn't be eaten. Fine found that when herbivores were excluded, clay soil species grew faster than white sand species on both soil types. But when the seedlings were subject to herbivores, the white sand specialists grew best in white sand, and the clay soil species grew best in clay soil. So soil type isn't the only thing that drives the evolution of these species; herbivory also plays a role.

Fine wants to learn more about the traits that differ between white sand specialists and clay soil specialists. He plans to do more reciprocal transplants, over wider areas of the Amazon, and plans to add a third habitat type, the flooded forests. That will mean doing experiments that are logistically and physically challenging. Moving trees around the Amazon is hard work. Fine and his team dig up the seedlings and pack their roots, still enmeshed in dirt, into plastic bags. They put the seedlings in plastic tubs and carry these heavy tubs to a river—the Amazon has few roads, so you can't back a truck up to Fine's field sites and just load up the seedlings. They transport the seedlings the same way that people in the region move about: by boat, along the Amazon's many rivers.

Despite the logistical difficulties, Fine loves working in the Amazon. "Field work is why I'm a biologist," he says. He stresses the importance of seeing organisms in their natural environment and being able to identify the different species, as a necessary first step in ecological research. Fine is actively involved in a conservation project to protect a small reserve, Allpahuayo-Mishana National Reserve, located just 25 km outside of the Peruvian city of Iquitos. His organization raises money to fund the salaries of four permanent park guards; even though it is a national reserve, it has no budget for park guard salaries. Without guards, says Fine, people illegally fish in the park's rivers, harvest palm trees, and start farming within the park's boundaries.

The park is "a world treasure, home to endemic bird species found nowhere else in the world," says Fine. "It is also the only place in the city of Iquitos, which has 400,000 or 500,000 people, where people can easily get to, walk around in a rainforest, and see plants and animals." Fine believes it is critical to conserve the natural environment and its biodiversity; "for future generations, it's going to be a source of curiosity and amazement and wonder."


In Spring 2009, Fine will teach Ecosystems of California, IB 157. The course will focus on plants, says Fine, "because I see plants as fundamental units of a community." Students will learn to identify the plants of California, and will understand the biotic and abiotic factors that influence plant distributions.




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