A river runs through it — and keeps the Amazon’s bird species diverse

first_imgA new genetic analysis shows that rivers in northeast South America rarely give rise to new bird species, but are important in maintaining existing biodiversity.Researchers found that 86 pairs of the more than 400 endemic bird species in the Rio Negro basin have range boundaries that meet but never overlap, many of them coinciding with either the Rio Negro or the Rio Branco.Amazonian rivers, they conclude, can play two distinct roles in species evolution: their formation may separate populations and create new species directly, and their presence can prevent hybridization or competition between related species that evolved independently and meet at the river.Understanding how the size of a barrier influences its ability to isolate populations genetically will have major implications for how conservationists try to mitigate the effects of habitat fragmentation caused by human activities. Amazonian rivers don’t often drive the creation of new species, but do help maintain distinct populations, according to a study published in the journal Science Advances last month.Amazonian rivers create stark barriers through the landscape and form the edges of many species’ range. But a large-scale genetic analysis in the Rio Negro basin suggests that while rivers have not played a direct role in giving rise to most new bird species, they may be crucial to maintaining them.The Guiana Shield is a region of the South American tectonic plate that includes Guyana, Suriname, French Guiana, Venezuela and parts of Colombia and Brazil, which together harbor high levels of biodiversity, including over 250 endemic bird species. Of these, 86 pairs have range boundaries that meet but never overlap, many of them coinciding with one of two rivers: the Rio Negro and the Rio Branco.Using the most comprehensive genetic and geographical database compiled for any Amazonian river basin to date, Luciano Naka and Robb Brumfield, both from Louisiana State University in Baton Rouge, Louisiana, determined that the majority of pairs were unlikely to have speciated as a direct result of the formation of the two rivers. Most species evolved before the rivers formed, and did not show the pattern of evolutionary relationships expected of species separated suddenly by a physical barrier. But once formed, rivers act as significant barriers that isolate species, a finding that may also apply to man-made barriers such as roads.The caica parrot (Pyrilia caica), one of the more than 400 bird species endemic to the Guiana Shield. Its population is mirrored across the lower Rio Negro and Rio Branco by the closely related orange-cheeked parrot (Pyrilia barrabandi). Image by Luciano N. Naka.“This is a major advance towards understanding the role of rivers as agents of speciation in Amazonia,” says Angelo Capparella, a zoologist at Illinois State University in Normal, Illinois, who was not involved in the study. Previous research has investigated this phenomenon for one or a few species, but large-scale studies have been hampered by a lack of specimens; it took Naka, who is also affiliated with the Federal University of Pernambuco in Recife, Brazil, over a decade to collect the necessary data for birds in the Rio Negro Basin. “The combination of [the] large sample size of paired taxa with the latest in phylogenetic methods … makes for this being a robust study,” says Capparella.For many species of birds, mammals and invertebrates, Amazonian rivers mark the start and end of their range. The pattern is so noticeable, renowned naturalist Alfred Wallace wrote about the phenomenon in his 1852 article, “On the Monkeys of the Amazon”: “the native hunters … always cross over the river when they want to procure particular animals, which are found even on the river’s bank on one side, but never by any chance on the other.”The range of the black nunbird (Monasa atra) ends at the lower Rio Negro. Across the river lives a population of the white-fronted nunbird. The two species shared a common ancestor some 4.5 million years ago. Image by Luciano N. Naka.To understand how this pattern arose, Naka and Brumfield used mitochondrial DNA sequence data from specimens supplied by U.S. and Brazilian ornithological collections to estimate the likely divergence times for 74 pairs of bird species that replace one another along the stretches of the Rio Branco and Rio Negro. They found that the species arose between 240,000 and 8 million years ago. “The ages of each pair span through millions of years,” says Naka, making it very unlikely that a single event could be responsible for separating all pairs.Next, the authors reconstructed the birds’ evolutionary tree to determine patterns of relatedness between pairs. If two species are created by the formation of a river, or other physical barrier, then they would be likely to be each other’s closest relatives, known as “sister taxa.” But this is not the case for birds living in the Guiana Shield. “There are other Amazonian populations that are more closely related to either one of the two taxa studied than its cross-river replacement,” Naka says, indicating that the species probably evolved elsewhere and later met at the river barrier.Further support for this interpretation came from published geomorphological data for the area, which indicates that both rivers are in fact much younger than most of the species included in the study. The Rio Negro formed just 1.2 million years ago, and the Rio Branco is younger still, with evidence that its course changed from northeast to south, reaching its current route through the Guiana Shield just 19,000 years ago, making them far too young to have been the driving factor in the evolution of most bird species pairs.However, 12 taxa pairs that are separated by the upper Rio Negro had diverged around the same time that the river was formed, making it possible that they speciated as a direct result of its formation. “We cannot rule out their common origin,” Naka says.The forests of the Guiana Shield are home to more than 400 endemic bird species. Image by Luciano N. Naka.Amazonian rivers, they conclude, can play two distinct roles in species evolution: their formation may separate populations and create new species directly, and their presence can prevent hybridization or competition between related species that evolved independently and meet at the river.In his 1852 paper, Wallace hypothesized that the width of a river would determine the extent to which species differed on either side. Naka says their results show some tentative support for this hypothesis. “The Rio Negro is a good example showing how the lower and very wide reaches of the river is a barrier for about 80 pairs of avian taxa, and the upper and much narrower reaches only bound the distribution of about 20 pairs,” he says. However, the Rio Branco bucks this trend: it is just 2 kilometers (1.2 miles) wide but acts as a barrier to 40 pairs of birds and several species of primates.Understanding how the size of a barrier influences its ability to isolate populations genetically will have major implications for how conservationists try to mitigate the effects of habitat fragmentation caused by human activities. “Features such as major roads … could be fragmenting bird populations to the point that it will either unleash a new wave of speciation or, more likely, force populations into remnant habitat that is too small for long-term persistence,” Capparella says.This type of study can underpin conservation approaches known as Conserving Nature’s Stage (CNS) that take into account the physical factors that generate and maintain biodiversity when designing nature reserves that will offer a habitat environment in the long term.Banner image of the Rio Branco by Thiago Orsi Laranjeiras.Citation: L. N. Naka, R. T. Brumfield, The dual role of Amazonian rivers in the generation and maintenance of avian diversity. Sci. Adv. 4, eaar8575 (2018). Article published by hayat Amazon Biodiversity, Amazon Conservation, Birds, Evolution, Genetics center_img Popular in the CommunitySponsoredSponsoredOrangutan found tortured and decapitated prompts Indonesia probeEMGIES17 Jan, 2018We will never know the full extent of what this poor Orangutan went through before he died, the same must be done to this evil perpetrator(s) they don’t deserve the air that they breathe this has truly upset me and I wonder for the future for these wonderful creatures. So called ‘Mankind’ has a lot to answer for we are the only ones ruining this world I prefer animals to humans any day of the week.What makes community ecotourism succeed? In Madagascar, location, location, locationScissors1dOther countries should also learn and try to incorporateWhy you should care about the current wave of mass extinctions (commentary)Processor1 DecAfter all, there is no infinite anything in the whole galaxy!Infinite stupidity, right here on earth.The wildlife trade threatens people and animals alike (commentary)Anchor3dUnfortunately I feel The Chinese have no compassion for any living animal. They are a cruel country that as we knowneatbeverything that moves and do not humanily kill these poor animals and insects. They have no health and safety on their markets and they then contract these diseases. Maybe its karma maybe they should look at the way they live and stop using animals for all there so called remedies. DisgustingConservationists welcome China’s wildlife trade banThobolo27 JanChina has consistently been the worlds worst, “ Face of Evil “ in regards our planets flora and fauna survival. In some ways, this is nature trying to fight back. This ban is great, but the rest of the world just cannot allow it to be temporary, because history has demonstrated that once this coronavirus passes, they will in all likelihood, simply revert to been the planets worst Ecco Terrorists. Let’s simply not allow this to happen! How and why they have been able to degrade this planets iconic species, rape the planets rivers, oceans and forests, with apparent impunity, is just mind boggling! Please no more.Probing rural poachers in Africa: Why do they poach?Carrot3dOne day I feel like animals will be more scarce, and I agree with one of my friends, they said that poaching will take over the world, but I also hope notUpset about Amazon fires last year? Focus on deforestation this year (commentary)Bullhorn4dLies and more leisSponsoredSponsoredCoke is again the biggest culprit behind plastic waste in the PhilippinesGrapes7 NovOnce again the article blames companies for the actions of individuals. It is individuals that buy these products, it is individuals that dispose of them improperly. If we want to change it, we have to change, not just create bad guys to blame.Brazilian response to Bolsonaro policies and Amazon fires growsCar4 SepThank you for this excellent report. I feel overwhelmed by the ecocidal intent of the Bolsonaro government in the name of ‘developing’ their ‘God-given’ resources.U.S. allocates first of $30M in grants for forest conservation in SumatraPlanet4dcarrot hella thick ;)Melting Arctic sea ice may be altering winds, weather at equator: studyleftylarry30 JanThe Arctic sea ice seems to be recovering this winter as per the last 10-12 years, good news.Malaysia has the world’s highest deforestation rate, reveals Google forest mapBone27 Sep, 2018Who you’re trying to fool with selective data revelation?You can’t hide the truth if you show historical deforestation for all countries, especially in Europe from 1800s to this day. WorldBank has a good wholesome data on this.Mass tree planting along India’s Cauvery River has scientists worriedSurendra Nekkanti23 JanHi Mongabay. Good effort trying to be objective in this article. I would like to give a constructive feedback which could help in clearing things up.1. It is mentioned that planting trees in village common lands will have negative affects socially and ecologically. There is no need to even have to agree or disagree with it, because, you also mentioned the fact that Cauvery Calling aims to plant trees only in the private lands of the farmers. So, plantation in the common lands doesn’t come into the picture.2.I don’t see that the ecologists are totally against this project, but just they they have some concerns, mainly in terms of what species of trees will be planted. And because there was no direct communication between the ecologists and Isha Foundation, it was not possible for them to address the concerns. As you seem to have spoken with an Isha spokesperson, if you could connect the concerned parties, it would be great, because I see that the ecologists are genuinely interested in making sure things are done the right way.May we all come together and make things happen.Rare Amazon bush dogs caught on camera in BoliviaCarrot1 Feba very good iniciative to be fallowed by the ranchers all overSponsoredlast_img

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