1300 species, 2400 genes, 21 museums, and 40 years: the tropical diversity paradox addressed by a multinational team of scientist

Every school kid learns where the hotspots of animal and plant diversity are – like the Amazon rainforest – but this week scientists report that new species actually form there less often than in coldspots. Coldspots aren’t actually cold, but are places like deserts and mountaintops that don’t have a lot of species but do have a lot of opportunity.

This paradox of diversity – that new species form away from tropical diversity hotspots – was reported this week in the journal Science. The multinational team of scientists studied diversity in a major group of tropical birds. They found that cold spots might be extreme with dry, unstable environments but they are also relatively empty, giving new species the elbow room to evolve. 

In contrast, hotspots like the Amazon are the result of the gradual accumulation of species over time. One of the senior authors on the study, Dr. Robb Brumfield, pointed out that this means that conservation efforts to save the rapidly changing tropical landscape need to focus “not only on the species-rich Amazon but also the generators of that diversity, like the wind-swept, cold puna of the Andes Mountains.” 

“This study also demonstrates that even for well-studied groups like birds, genomic data is completely changing our perspective about true levels of species diversity, particularly in tropical areas,” says a co-author of the study Alexandre Aleixo from the Natural History Museum of Finland (LUOMUS), University of Helsinki.

“For about 12% of the species sampled with more than a single individual in our study, intraspecific genomic divergences were greater than those between closely related species, indicating the existence of many “hidden” species yet to be named and formally described”. 

Describing new bird species has been one of the main targets of Aleixo´s Laboratory of Avian Diversity (LADY), which has moved to LUOMUS in 2019. Since 2012, his lab led the description of no less than seven new bird species to science, in addition to publishing studies supporting the recognition of dozens of “hidden” species previously regarded as subspecies. 

“The results of this recent study involving such an incredible number of species, museum specimens, and very significant parts of their genomes, consist on a true `road map´ for finding and describing new species, and we are already working on it!” says Aleixo. 

Local scientists play a key role in recording biodiversity           

This paradox was revealed because of the dozens of natural history museums and museum researchers working for decades in tough conditions on shoestring budgets to document the rapidly disappearing diversity of the tropics. Some of the collections contributing to this paper, including the Goeldi Museum in Brazil, are now facing major budget and staff cuts that jeopardize their roles as key repositories of information and samples from Neotropical environments. The leads on the paper - Dr. Michael Harvey (UT El Paso) and Dr. Gustavo Bravo (Harvard) have themselves spent many months lugging around the quintessential, heavy dewars used to preserve samples up remote streams in Amazonia and into rugged mountain ranges in the Andes. 

Dr. Harvey said “these birds represent an incredible amount of diversity sampled, roughly 1 out of every three species of birds in the American tropics” and Dr. Bravo agreed, “Yes, we were only able to do this because of the hard work of numerous local scientists who have dedicated their lives to studying and preserving this diversity.”  

Notably, these collecting trips and research teams are increasingly led by ornithologists from groups underrepresented in the sciences, including Latinx and women researchers. Many of the researchers involved in the study are from Latin America (Colombia, Brazil, Uruguay, and Venezuela) and recent teams fielded by the renowned Museum of Natural Science at Louisiana State University have been women-led. 

“This paper marks not only a change in our understanding of evolution in the tropics but also in acknowledgement and valuation of the diversity of culture, expertise, and perspective in the field of ornithology” says another senior author on the paper, Dr. Liz Derryberry

Original article:

The evolution of a tropical biodiversity hotspot
Authors: Harvey MG, Bravo GA, Claramunt S, Cuervo AM, Derryberry GE, Battilana J, Seeholzer GF, Shearer McKay J, O’Meara BC, Faircloth BC, Edwards SV, Pérez-Emán J, Moyle RG, Sheldon FH, Aleixo A, Smith BT, Chesser RT, Silveira LF, Cracraft J, Brumfield RT, Derryberry EP. DOI: 10.1126/science.aaz6970