wp-plugin-hostgator domain was triggered too early. This is usually an indicator for some code in the plugin or theme running too early. Translations should be loaded at the init action or later. Please see Debugging in WordPress for more information. (This message was added in version 6.7.0.) in /home4/scienrds/scienceandnerds/wp-includes/functions.php on line 6114ol-scrapes domain was triggered too early. This is usually an indicator for some code in the plugin or theme running too early. Translations should be loaded at the init action or later. Please see Debugging in WordPress for more information. (This message was added in version 6.7.0.) in /home4/scienrds/scienceandnerds/wp-includes/functions.php on line 6114Source:https:\/\/www.quantamagazine.org\/how-pools-of-genetic-diversity-affect-a-species-fate-20230425\/#comments<\/a><\/br> In March 2018 at the Ol Pejeta Conservancy in Kenya, surrounded by his devoted keepers, Sudan the northern white rhino breathed his last. He wasn\u2019t the only remaining northern white rhino because three females in protective captivity survived him. But Sudan\u2019s death ended any hope of those females breeding naturally and rendered the northern white rhino effectively extinct. The moment made headlines, and the world lamented the high-profile extinction.<\/p>\n But it wasn\u2019t a true species extinction event. Northern white rhinos are just a distinct subset, or subspecies, of white rhino. More than 10,000 white rhinos are still left in the southern subspecies. White rhinos as a species aren\u2019t even endangered.<\/p>\n Nevertheless, ever since Sudan\u2019s death, Cynthia Steiner<\/a>, an associate director in conservation genetics for the San Diego Zoo Wildlife Alliance, and her colleagues have gone to great lengths to try to reboot the northern subspecies. They\u2019re working to turn stem cells collected from the remaining females into embryos for in vitro fertilization<\/a>. They want more northern white rhinos, and mixing in genes from southern white rhino males just won\u2019t do.<\/p>\n \u201cBefore, people would say, we need to save the species,\u201d Steiner explained. \u201cBut that\u2019s not enough if you think about it. When you talk about species, you\u2019re not considering the whole evolutionary potential of all the different groups that make up that species. That\u2019s why the new notion is: We really want to save the genetic structure of the species, these different populations \u2014 subspecies \u2014 that have unique characteristics at the genomic level.\u201d<\/p>\n In recent years, biologists have developed a deeper understanding of how the relationship between genetic diversity and population structure can influence the fate of a species. They\u2019ve long understood how geography and ecological variations often partition species into subspecies or other small distinct populations of individuals who are more closely related to one another than to outsiders. Now, with the help of better tools and techniques for studying the genomes of creatures in the wild, researchers are discovering the full extent of how much the genetic dynamics within and among those populations can affect how resiliently a species can evolve and adapt to changing conditions over time. Those distinct populations can sometimes act as refuges or reservoirs for uncommon genes, and they can become the salvation of a species if new threats suddenly make those genes more valuable. On the other hand, if the smaller populations become too isolated, they can die out and make chunks of a species\u2019 genetic diversity vanish forever.<\/p>\n It\u2019s an important insight into how species naturally adapt and evolve. Luckily for the many species of rhinos, whales, panthers, amphibians and other endangered organisms around the world, this richer understanding of genetic diversity and population dynamics can also help conservation practitioners make better choices about how to save imperiled animals.<\/p>\n But the choices involved sometimes mean probing more deeply into a crucial question: When we try to save a species, what exactly are we trying to save?<\/p>\n Biologists typically use \u201cspecies\u201d as a label for \u201creproductively isolated\u201d populations of organisms that generally breed among themselves and not with outsiders. In effect, a species is a breeding pool that holds all the variant forms (or alleles) of genes that one might find in a type of organism. The species concept is a linchpin of modern biology and evolutionary theory, although it has been intensely criticized for failing to capture the reality of how some organisms actually behave and breed.<\/p>\n Yet although species are pools of genes, those pools are not evenly mixed. Subgroups of lineages within them may tend to breed with one another more often, and they may develop sets of distinctive traits. Naturalists sometimes recognize such groups as subspecies. But even without a subspecies label, there can be populations of individuals within a species (or even within a subspecies) that have a recognizable identity over time.<\/p>\n The U.S. Endangered Species Act<\/a> of 1973 was ahead of its time on this: It has always allowed the listing of \u201cany distinct population segment,\u201d not just fully distinct species. A quarter of U.S.-listed endangered \u201cspecies\u201d are actually subspecies, including well-known examples like Florida panthers, northern spotted owls and Mexican gray wolves.<\/p>\n The idea is to consider not just the current survival of a species but its potential evolutionary ability to adapt when faced with environmental changes or emerging diseases in the future. The source of this resilience is its genetic diversity. If a new pest or disease strikes a genetically diverse population, any individuals that happen to be naturally resistant can survive it and reproduce. If all the individuals are genetically alike and lack resistance, the population will die out.<\/p>\n This is currently happening in North American forests, where tens of millions of ash trees are succumbing to a beetle, the emerald ash borer. Some individual ash trees, however, are genetically resistant to the beetles, and they are the last hope for the species.<\/p>\n Population structure bears on genetic diversity because sometimes rare variants of genes are only able to survive by getting\u00a0sequestered in subpopulations<\/a>\u00a0more conducive to their survival. Moreover, researchers have discovered that the importance of genetic diversity goes beyond a population\u2019s specific inventory of genetic traits.\u00a0Recent studies<\/a>\u00a0have helped to confirm\u00a0a proposal<\/a>\u00a0by\u00a0Michael Lynch<\/a>, an evolutionary biologist at Arizona State University, that the efficiency of natural selection depends on the \u201ceffective population size,\u201d which describes the amount of genetic diversity; this dictates how quickly or slowly species (and populations within them) may evolve, which in turn affects how well species may adapt or whether they will splinter into new species.<\/p>\n That\u2019s why conservationists didn\u2019t simply release the last lonely northern white rhino females into the southern population and call it a day, and why Steiner\u2019s group has been trying to create northern white rhino embryos. Keeping both the northern and southern subspecies in existence separately will better preserve the adaptive potential of the white rhino species as a whole by preserving the unique characteristics and the full genetic diversity of each.<\/p>\n When a species or population gets too small, it can lose more than its adaptive potential for surviving future threats. It can lose its ability to sustain itself, as was seen in a study of killer whales<\/a>, or orcas, that was published in March in Nature Ecology & Evolution<\/em>.<\/p>\n<\/div>\n <\/br><\/br><\/br><\/p>\n
\nHow Pools of Genetic Diversity Affect a Species\u2019 Fate<\/br>
\n2023-04-26 21:58:27<\/br><\/p>\nNot Just Species<\/strong><\/h2>\n
An Inbreeding Bottleneck<\/strong><\/h2>\n