Leilton W. Luna is a postdoc at the Pennsylvania State University. He is a biologist with a broad interest in how species adapt, diversify, and become extinct. Here, Leilton shares his recent work on birds of the Amazonian floodplains.
Leilton Luna doing research or just having fun bird watching.
Institute. Department of Ecosystem Science and Management, Pennsylvania State University, USA
Academic life stage. Postdoc
Major research themes. Connections between the evolution of Earth and living organisms, ecological drivers of biological diversity, and the application of population genomics to the conservation of endangered species.
Current study system. I am currently studying the birds of the Amazonian floodplains. These river-created environments have a unique diversity of species, in contrast to adjacent habitats, such as upland (terra firme) forests. To me, the coolest thing is to understand how a riverine landscape produces such a wide variety of species. Perhaps one of the keys to understanding this question is to investigate the past, using genomic technologies. Using genomic data, I can explore the relationships between floodplain bird populations and the historical events in the Amazon that possibly made these populations so differentiated today.
Recent JBI paper. Luna, L. W., Ribas, C. C. & Aleixo, A. 2022. Genomic differentiation with gene flow in a widespread Amazonian floodplain-specialist bird species. Journal of Biogeography 49(9): 1670-1682. https://doi.org/10.1111/jbi.14257
Motivation behind this paper. The biogeographic history of floodplains is poorly known in comparison to other Amazonian environments. Therefore, we would like to understand what factors are responsible for generating diversity in Amazonian floodplains. Could it be differences between flooded environment types, such as blackwater igapó versus white-water várzeas forest? Or changes in the riverine landscape caused by past climate changes? Or even an interplay between these factors? To answer these questions, we study the Striped Woodcreeper (Xiphorhynchus obsoletus), the most common and widely distributed bird in the Amazonian floodplains. The tight relationship of this bird to the floodplains could tell us a little bit about the history of the environment, and for this purpose, we analysed its DNA. Another motivator was to underscore the importance of collections and expeditions for biodiversity research. Our study used tissues deposited in genetic resource collections, in museums from Brazil and the USA, which are the result of more than two decades of expeditions into the Amazonian floodplains.
Left: The Striped Woodcreeper (Xiphiorhynchus obsoletus). What can its DNA tell us about the history of the Amazon floodplains? (Credit: João Barros). Right: The igapó flooded forest of the Demini River, a tributary of the Negro River. The watermark on the tree trunk shows the height of the river during the flood (Credit: Thiago Laranjeiras).
Key methodologies. To investigate the structure and connectivity of Striped Woodcreeper populations, we sequenced a small amount of the bird’s genome. Along with genomic data, we used environmental information to test whether genetic differences between populations were associated with steep environmental gradients, specifically between igapó (habitats bordering clear- and black-water rivers) and várzeas forests (associated with white-water rivers). In addition, we tested different evolutionary scenarios based on information from geomorphological changes that occurred in central Amazonia during the Late Pleistocene. Here, the novel approach was to combine environmental and geologic information to gain insights into the drivers of genetic diversity in Amazonian floodplains.
Unexpected challenges. The main challenge was to cover the sampling of the Striped Woodchopper in the huge area of the Amazon basin. Even with tissue bank contributions from several past expeditions into the flooded forests, there were still important gaps. Thus, in August 2017, we undertook a navigation expedition on the Solimões River, in the heart of the Amazon. Spending 30 days on a boat, waking up early in the morning to enter the jungle and search for the Striped Woodcreeper and other floodplain birds, was a thrilling and frightening experience. The apprehension of not getting the samples was a constant companion. However, with the help of an extraordinary team of ornithologists from the National Institute for Amazon Research (INPA) and the Emilio Goeldi Museum (MPEG), we were able to succeed.
The team of ornithologists (also biogeographers) from INPA and Museum Emilio Goeldi navigating between Amazonian riverine islands during an expedition on the Solimões River in August 2017.
Major results. We found that genetic variability in a bird endemic to the Amazonian floodplains is more related to the history of changing riverine connections associated with Late Pleistocene climate change, rather than strong contemporary environmental gradients. Also, by comparing our results with others previously published, we found that the type of habitat a species uses can possibly determine the levels of genetic differentiation between populations. These findings add a new layer of information about the formation of the Amazonian biodiversity, which involves complex interactions between species’ ecological traits and the dynamic history of their environments.
Next steps for this research. The next step is to investigate the genetic diversity of more floodplain birds! This time, the idea is to gather a collection of bird species with different habitat specializations and test whether habitat use determines the structure and levels of genetic differentiation across species. Understanding these interactions is critical for highlighting the uniqueness of Amazonian floodplains, since many of these habitats are intensively destroyed in parts of the Amazon basin by logging and hydroelectric dam construction. These human activities are already affecting the occupancy of floodplain birds, but little is known about the effects on genetic diversity and connectivity at both population and community scales.
If you could study any organism on Earth, what would it be? Rather than an organism, I would like to study an interaction between organisms. I find it fascinating how species that compete for the same resources can adapt and evolve to this competition. Or even how two species find a way to coexist in intimate dependence, “cooperating mutualistically” throughout their evolutionary history. What could be the genetic basis behind the adaptation of such interactions? In this case, I would continue to study birds, which exhibit several interesting interactions with other groups of organisms. Be it hummingbirds selecting their favorited flowers by smell, or birds parasitizing the nest of other birds so that their offspring can survive (even at the expense of their foster siblings).
Anything else to add? As someone born in Amazonia, it is impossible not to be impressed by the number of species – especially bird species. A casual walk on the edge of a forest, or even in city parks, is enough to realize that there is something special about this region. Therefore, having the opportunity to study the Amazonian biodiversity is something rewarding. A lifetime is not enough to understand the evolutionary, ecological, and ecosystem complexity of this green wonderland. But unfortunately, that clock is ticking against this biodiversity, as levels of destruction, habitat conversion, and climate change are driving the Amazon rainforest to its tipping point. But despite this grim prospect, I still see that there is much to be done, both in science and in international conservation policies, to keep this huge forest, the number of species, and the native peoples who live in it standing.
The flooded Amazonian forests differ according to the “color” of the river. Meeting of the waters between the Negro River (igapó black-water) and the Solimões River (várzea white-water) (Credit: Thiago Laranjeiras).