• How new bird species arise

    From ScienceDaily@1:317/3 to All on Thu Mar 10 21:30:42 2022
    How new bird species arise

    Date:
    March 10, 2022
    Source:
    University of Copenhagen - Faculty of Science
    Summary:
    Much of a centuries-old debate over where and how new bird species
    form has now been resolved. Researchers have provided evidence
    that birds in mountainous areas -- where the vast majority of the
    planet's species live -- have left lowland habitats for higher and
    higher mountain elevations throughout their evolution. Millions
    of years of climatic fluctuations have contributed to pushing bird
    species upslope -- as is probably happening now.



    FULL STORY ==========================================================================
    Much of a centuries-old debate over where and how new bird species form
    has now been resolved. Researchers at the University of Copenhagen have provided evidence that birds in mountainous areas -- where the vast
    majority of the planet's species live -- have left lowland habitats for
    higher and higher mountain elevations throughout their evolution. Millions
    of years of climatic fluctuations have contributed to pushing bird
    species upslope -- as is probably happening now.


    ==========================================================================
    One of the fundamental questions in biology, and a centuries-old
    academic debate, is: How do new species form? And, how do species end
    up on mountaintops several kilometers high? Indeed, 85% of the world's vertebrates -- birds included -- live in mountainous areas where lowland habitats isolate animal species and populations from one another.

    "The discussion about how mountain bird species arise has been ongoing
    among scientific researchers for many years. Some say -- "Obviously,
    birds can just fly from one mountain to another," while others say --
    "Well, actually they don't." Scientists have been arguing about this since Darwin and Wallace. But until now, no one had the scientific evidence," explains associate professor Knud Andreas Jo/nsson of the Natural History Museum of Denmark at the University of Copenhagen.

    He and a number of fellow researchers from the University of Copenhagen
    are now in possession of evidence that can settle the age-old feud --
    or at least the part of it concerning the enormous island region around Indonesia and Australia. The evidence comes as the result of collecting
    entire genomes from various bird populations on the world's largest
    tropical island -- mountainous New Guinea.

    Genomic analyses have established that bird species emerge in the lowlands
    and then move higher and higher into mountainous areas over millions of
    years - - probably both due to competition and climate change -- before eventually going extinct. For this reason, mountain peaks, like islands,
    are often referred to as evolutionary dead ends. The results have been published in Nature Communications.

    The closer to the top, the greater the genetic variation By sequencing
    DNA from birds of the same species, but living on two separate mountains, researchers were able to investigate how genetically different these populations are from each other.



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    "We can see that the higher up in the mountains birds live, the greater
    the differences between populations of the same species. Some of the populations are so different, that one could make the case that they
    are distinct species.Conversely, there are greater similarities among
    lowland populations.

    This tells us that the spread of new species must have taken place from
    lowland habitats upwards," explains Knud Andreas Jo/nsson, the study's
    lead author.

    Because the researchers are also familiar with the generation time
    of these birds, they have been able to measure that the movement of
    species from lowlands to mountaintops has occurred gradually, over a
    couple million years.

    Knud Andreas Jo/nsson points out that the study does not necessarily
    suggest an upslope pattern of colonization globally. Therefore, it is
    important to investigate the processes behind species formation within
    specific zoogeographical regions.

    Climate fluctuations pushed birds higher up the mountain The study
    also shows that climate fluctuations, especially over the past two
    million years -- known as Pleistocene climate oscillations -- caused
    dramatic fluctuations in the size of the populations. At times, climate fluctuations probably contributed to the upslope evolution.



    ==========================================================================
    "As it gets warmer, montane forests and birds are pushed further upslope,
    to where there is less and less habitat and to where they are more
    likely to become extinct. As a result, one sees large fluctuations in population sizes.

    As it got warmer, populations shrank, and the poorer a population's
    chances became for further colonization," explains Knud Andreas Jo/nsson.

    On average, bird species survive a few million years before dying
    out. The smaller the population, the more vulnerable a species is and
    the greater its risk of extinction. As the researcher points out: "Our
    analyses demonstrate that the species living on mountain peaks are 5-10
    million years old. So, the oldest and most specialized species live at elevations of 3-4 kilometers, and in small numbers. Climate fluctuations
    can accelerate the process, so that ancient species will go extinct
    faster. This will probably be a consequence of modern-day global warming
    as well." Mountain birds are at greatest risk Great swaths of lowland
    forest have disappeared in the New Guinea-Indonesia region. Consequently,
    there has been a considerable focus on the loss of the many lowland
    species living there. But according to the researcher, the new results
    could serve to help prioritize the conservation of highland birds.

    "There is no doubt that highland bird species are the ones most vulnerable
    to global warming. Given that it has taken millions of years for their populations to build and their great genetic variation on individual
    mountain peaks, perhaps something more should be done to preserve them. It isn't just a global goal to preserve species, but to preserve genetic diversity," concludes Knud Andreas Jo/nsson.

    Occasionally, the improbable occurs Although species colonization
    generally occurs from lowland towards highland habitats, there is also a regular, but limited amount of genetic exchange between mountaintops. This happens when a few individuals per generation manage to travel from one mountain range to another and propagate. While some might think that this shouldn't be too surprising for a winged creature, Knud Andreas Jo/nsson
    finds it astonishing: "One of the species that occasionally makes the more
    than 100-kilometer long trip across mountains is the blue-capped ifrit
    (Ifrita kowaldi), a stationary forest songbird. Without the new data,
    I'd say, 'I just don't believe it!' In the past, we have used satellite transmitters to track similar forest birds in New Guinea and seen that
    they tend not to disperse at all. But occasionally, the improbable occurs,
    if there is enough time and enough individuals within a population,"
    concludes Knud Andreas Jo/nsson.

    About the study
    * A disproportionately large number of Earth's animal species are
    concentrated in mountainous areas. While mountains account for
    roughly a quarter of Earth's surface, 85% of all bird, amphibian
    and mammal species of live in mountainous areas.

    * New Guinea is home to more than 4,600 species of vertebrates,
    including
    700+ bird species. Along with Australia, it belongs to the
    exceptionally unique zoogeographic region of Oceania.

    * The birds studied belong to the group known as songbirds, or 'order
    Passeriformes', which make up nearly half of all bird species
    worldwide.

    Songbirds emerged in Australia/New Guinea roughly 30-40 million
    years ago.

    * The research was conducted by Jose' Marti'n Pujolar, Andrew
    Hart Reeve,
    Jonathan D. Kennedy, Petter Zahl Marki, Thorfinn S. Korneliussen
    and Knud Andreas Jo/nsson from the University of Copenhagen; Mozes
    P. K. Blom and Martin Irestedt from the Natural History Museum,
    Sweden; Benjamin G.

    Freeman of the University of British Columbia, Canada; Katerina
    Sam of the University of South Bohemia, Czech Republic; Ethan
    Linck of the University of New Mexico, U.S.; Tri Haryoko of the
    National Research and Innovation Agency (BRIN), Indonesia; Bulisa
    Iova of the Papua New Guinea National Museum and Art Gallery,
    Papua New Guinea; Bonny Koane, Gibson Maiah and Luda Paul from
    The New Guinea Binatang Research Centre, Papua New Guinea.

    * The research is funded by the Villum Foundation.


    ========================================================================== Story Source: Materials provided by University_of_Copenhagen_-_Faculty_of_Science. Note: Content may be
    edited for style and length.


    ========================================================================== Related Multimedia:
    * Birds_and_New_Guinea ========================================================================== Journal Reference:
    1. Jose' Marti'n Pujolar, Mozes P. K. Blom, Andrew Hart Reeve,
    Jonathan D.

    Kennedy, Petter Zahl Marki, Thorfinn S. Korneliussen, Benjamin G.

    Freeman, Katerina Sam, Ethan Linck, Tri Haryoko, Bulisa Iova,
    Bonny Koane, Gibson Maiah, Luda Paul, Martin Irestedt, Knud
    Andreas Jo/nsson.

    The formation of avian montane diversity across barriers and along
    elevational gradients. Nature Communications, 2022; 13 (1) DOI:
    10.1038/ s41467-021-27858-5 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/03/220310095944.htm

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