Wednesday, June 29, 2016

The demise of a stonefly

Much remains unknown about the genetic status and population connectivity of high-elevation and high-latitude freshwater invertebrates, which often persist near snow and ice masses that are disappearing due to climate change.

The four members of the stonefly genus Lednia are only known from high-elevation regions of western North America, e.g. Lednia tumana  is endemic to the Waterton-Glacier International Peace Park region of Montana, Alberta, and British Columbia. These species are adapted colder water temperatures as they occur in meltwater streams below glaciers, permanent snowfields, and alpine springs. Global climate change is expected to have dramatic effects on the structure and function of freshwater and the rise of ambient temperature has been correlated with increases in stream temperatures. Here we might have a good example of what might happen to a species that is adapted to colder temperatures. The region in where Lednia tumana is found used to be home to about 150 glaciers (around 1850), 125 of those have disappeared, and if we can believe the latest predictions based on current warming trends it will take less than 15 years for the remaining 25 to vanish as well. This will reduce the amount of suitable habitat for this stonefly by over 80% .

A group of US researchers now explored population genetic structure of this species over the last decade by using DNA barcodes and cytb sequence data. They collected nymphs and adults in 2010 and supplemented with those with older samples collected in 1997, 1998, and 2005. The results were quite sobering: The dominant haplotype was common in both time periods, while the second-most-common haplotype was found only in historic samples, having been lost in the interim. The 2010 populations also showed reduced gene and nucleotide diversity and increased genetic isolation. Our results imply small effective sizes, increased fragmentation, limited gene flow, and loss of genetic variation among contemporary L. tumana populations, which can lead to reduced adaptive capacity and increased extinction risk. This study reinforces concerns that ongoing glacier loss threatens the persistence of L. tumana, and provides baseline data and analysis of how future environmental change could impact populations of similar organisms.

Today all the newspapers and outlets are talking about Adélie penguins and the fact that habitat loss caused from warmer water and loss of sea ice could bring a 60% population decline of this penguin species by 2099. A new study shows that warming in Antarctica, once beneficial to the penguins, has reached a tipping point and is causing the sharp decline. However, as per usual nobody is talking about something as uninteresting as a stonefly and the fact that it is perhaps already too late to reverse the developments that will eventually lead to its extinction. 

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