MSGID: 1:317/3 6274a47c   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Only 10 vaquita porpoises survive, but species may not be doomed,   
   scientists say    
    If they can escape death in poachers' nets, the endangered marine mammal   
   is well poised to rebound despite inbreeding    
      
     Date:   
         May 5, 2022   
     Source:   
         University of California - Los Angeles   
     Summary:   
         The world's smallest marine mammal -- the critically endangered   
         vaquita porpoise, which lives only in Mexico's Sea of Cortez --   
         is believed to have only 10 living members, if that, of the   
         species. The vaquita is widely thought to be on the verge of   
         extinction, but a new scientific analysis by a team of biologists   
         concludes the species remains relatively healthy and can survive --   
         if the illegal use of 'gillnet' fishing ceases promptly.   
      
      
      
   FULL STORY   
   ==========================================================================   
   The vaquita porpoise, the world's smallest marine mammal, is on the   
   brink of extinction, with 10 or fewer still living in Mexico's Gulf   
   of California, their sole habitat. But a genetic analysis by a team of   
   UCLA biologists and colleagues has found that the critically endangered   
   species remains relatively healthy and can potentially survive -- if   
   illegal "gillnet" fishing ceases promptly.   
      
      
   ==========================================================================   
   "Interestingly, we found the vaquita is not doomed by genetic factors,   
   like harmful mutations, that tend to affect many other species whose   
   gene pool has diminished to a similar point," said Christopher Kyriazis,   
   a UCLA doctoral student in ecology and evolutionary biology and a co-lead   
   author of the research. "Outlawed fishing remains their biggest threat."   
   The small porpoises, which range from 4 to 5 feet in length, often become   
   entangled and die in the large mesh gillnets used by poachers hunting   
   the totoaba, an endangered fish highly valued in some countries for   
   its perceived medicinal properties. While Mexico has outlawed totoaba   
   fishing and made the use of these nets in the vaquitas' habitat illegal,   
   many say the bans are not always enforced.   
      
   The researchers analyzed the genomes of 20 vaquitas that lived between   
   1985 and 2017 and conducted computational simulations to predict the   
   species' extinction risk over the next 50 years. They concluded that   
   if gillnet fishing ends immediately, the vaquita has a very high chance   
   of recovery, even with inbreeding. If, however, the practice continues,   
   even moderately, the prospects of recovery are less optimistic.   
      
   The research is published May 6 in the journal Science.   
      
   "Relative to other species, the vaquita has a higher chance of   
   rebounding from an extreme population crash without suffering severe   
   genetic consequences from inbreeding," said co-lead author Jacqueline   
   Robinson, a postdoctoral scholar at UC San Francisco who earned her   
   doctorate in biology at UCLA. "Genetic diversity in vaquitas is not so   
   low that it constitutes a threat to their health and persistence. It   
   simply reflects their natural rarity."  Genetic diversity is a measure   
   of the differences that exist across the genome among individuals in   
   a population. Large populations tend to have many differences, while   
   naturally smaller or decimated ones have fewer, resulting in individuals   
   that are more genetically similar. That similarity can often result in   
   a greater incidence of harmful mutations that endanger the population   
   since individuals are more likely to inherit the same muted gene from   
   both parents, said senior author Kirk Lohmueller, UCLA associate professor   
   of ecology and evolutionary biology and of human genetics.   
      
      
      
   ==========================================================================   
   "A prevailing view in conservation biology and population genetics is that   
   small populations can accumulate deleterious mutations," Lohmueller said.   
      
   "However, our finding that the vaquita likely has fewer strongly   
   deleterious mutations hiding in the population means that they are   
   better poised to survive future inbreeding, which bodes well for their   
   overall recovery."  So what protects the vaquitas from the genetic perils   
   of inbreeding? Much of it has to do with the fact that they have always   
   been a small population in a very small habitat in the northern tip of   
   the gulf, the researchers said. While their historic numbers are unknown,   
   the first comprehensive survey in 1997 counted roughly 570 porpoises --   
   a number that has declined steadily over the last 25 years but which   
   was not large to begin with.   
      
   "They're essentially the marine equivalent of an island species," said   
   Robinson, who noted that the species has survived for tens of thousands of   
   years with low genetic diversity. "The vaquitas' naturally low abundance   
   has allowed them to gradually purge highly deleterious recessive gene   
   variants that might negatively affect their health under inbreeding."   
   In fact, Robinson said, of the 12 marine mammal species -- including   
   vaquitas - - the researchers genetically analyzed, vaquitas had the   
   lowest number of potentially harmful mutations.   
      
   While the interplay among small population size, inbreeding and harmful   
   genetic variations is complex, the approach used by the team in this   
   study can help shed light on these dynamics.   
      
      
      
   ==========================================================================   
   "With genomic datasets, we now have the ability to address this   
   complexity," Robinson said. "Species can vary in their levels of harmful   
   genetic variation, and they will not all be affected exactly the same way   
   by reduced population size or inbreeding. There are now many examples   
   of species recovering from extreme declines."  "We hope our analysis   
   is useful not only in demonstrating the potential for the vaquita to   
   recover," Kyriazis said, "but also in highlighting a novel genomics-   
   based simulation approach for endangered species."  Encouragingly,   
   the surviving vaquitas in the northern Gulf of California are actively   
   reproducing and appear healthy. But poachers' gillnets continue to pose   
   an existential threat to the species, and unless further measures are   
   taken to protect the porpoises, there is a distinct possibility they may   
   go extinct. The loss would be a great tragedy, said the study's senior   
   author, UCLA's Robert Wayne.   
      
   "The vaquita is symbolic of the unique diversity found in the Gulf   
   of California, which was described by John Steinbeck in his wonderful   
   1951 book 'The Log From the Sea of Cortez,'" said Wayne, a distinguished   
   professor of ecology and evolutionary biology and a Howard Hughes Medical   
   institute professor. "It represents a unique evolutionary lineage -- there   
   is no similar species anywhere in the world -- and its loss would rob the   
   ecosystem of an important predator adapted to this unique ecosystem."   
   Funding sources for the research included the National Institutes of   
   Health, the National Oceanic and Atmospheric Administration (NOAA)   
   and the Mexican National Council for Science and Technology.   
      
   Co-authors included Phillip Morin of the NOAA's Southwest Fisheries   
   Science Center; vaquita researchers Barbara Taylor of the NOAA and   
   Lorenzo Rojas- Bracho; Sergio Nigenda Morales of the Advanced Genomics   
   Unit in Irapuato, Guanajuato, part of Mexico's National Laboratory of   
   Genomics for Biodiversity; and Annabel Beichman of the University of   
   Washington. Morales and Beichman earned their doctorates at UCLA studying   
   under Wayne and Lohmueller.   
      
      
   ==========================================================================   
   Story Source: Materials provided by   
   University_of_California_-_Los_Angeles. Original written by Stuart   
   Wolpert. Note: Content may be edited for style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Jacqueline A. Robinson, Christopher C. Kyriazis, Sergio F. Nigenda-   
         Morales, Annabel C. Beichman, Lorenzo Rojas-Bracho, Kelly   
         M. Robertson, Michael C. Fontaine, Robert K. Wayne, Kirk   
         E. Lohmueller, Barbara L.   
      
         Taylor, Phillip A. Morin. The critically endangered vaquita is not   
         doomed to extinction by inbreeding depression. Science, 2022; 376   
         (6593): 635 DOI: 10.1126/science.abm1742   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2022/05/220505143218.htm   
      
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