Galapagos and California Sea Lion Speciation

 

        Galapagos Sea lions are currently an endangered species native to the Galapagos islands. Galapagos sea lions are a member of the pinniped family and face threats such as plastic populations, habitat loss and change, and human activity. When it comes to the conservation of marine mammals, their genetic information is crucial to better understand their ecology and how to protect their populations. In 2007 researchers dove into the genetic composition of Galapagos Sea lions and California Sea Lions to determine if the two were distinct species. Through the analysis of mitochondrial DNA and phylogenetic reconstruction, they determined that the common ancestor of Galapagos Sea Lions and California Sea Lions existed 2.3 ± 0.5 mya. Additionally, they discovered that gene diversity is 14% lower in Galapagos Sea Lion populations.

         The reduced genetic diversity in Galapagos Sea Lions has large implications when it comes to species conservation. When the article was published the species was listed as threatened and as of 2023, the population is listed as endangered. For the population to be able to recover sustainably, the reduced genetic diversity should be taken into consideration. To properly conserve the population in the future, any breeding efforts should be carefully orchestrated to ensure the best genetic diversity possible. 

Pesticide Runoff is affecting Aquatic Mammals due to Lost Genes

Today’s Marine mammals have all evolved from terrestrial mammals that trekked back into aquatic environments and created adaptations to thrive in these new environments. One of the genes they lost in adapting to aquatic life was an enzyme that would aid in defending against pesticides. With this discovery of a missing gene in marine mammals make the issues of pesticide runoff in oceans an even more important issue in our environment. The gene responsible for this defense was labeled as PON1 which was identified to defend against organophosphates, the pesticides used in agriculture. Most marine mammals have pieced together similar enzymes to replicate the results of the PON1 gene with some exceptions being walruses, fur seals, and spotted seals, all of which would be the most vulnerable to organophosphates. Now why did these marine mammals adapt to lose this gene that their terrestrial ancestors once had? The leading theory is that due to the fact that marine mammals take in large amounts of oxygen for deep dives, they evolved to remove oxygen carrying molecules. Molecules such as PON1, that otherwise would be harmful under the pressure of deep dives. (Zimmer, 2018)

These pesticide runoffs have also started to affect coastal avian species as well as the marine mammals. There have been a rise of unidentified diseases and conditions related to issues with the organisms endocrine systems. With an organisms endocrine system being exposed to its surroundings, many believe that these pesticide runoffs are to blame for the unusual mutations and reactions of these organisms. (Tanabe, 2009)

Even though there isn't evidence that directly links the runoff to these mutations and diseases in coastal organisms such as mammals and avians, the consensus of these researchers are that the pesticides have a part to play in this ecological issue. It is impossible to know exactly where runoff from agriculture will wind up but it is a guarantee that it will reach the oceans at once point. This means that we have to be conscious of the volume of pesticides we use on our plants as well as the possible reactions that organisms in the oceans and waterways will have to these chemicals. Although there aren’t direct links to the issues marine mammals are facing, i suspect that in the coming years more information will be discovered on the effects of such pesticides on marine mammals and other ocean going species.

References

Tanabe, S. (2002, 09). Contamination and toxic effects of persistent endocrine disruptors in marine mammals and birds. Marine Pollution Bulletin, 45(1-12), 69-77. doi:10.1016/s0025-326x(02)00175-3

Zimmer, C. (2018, August 09). Marine Mammals Have Lost a Gene That Now They May Desperately Need. Retrieved from https://www.nytimes.com/2018/08/09/science/marine-mammals-pesticides.html

Using Genetics to Define Sub-populations of Killer Whales

Population boundaries are often difficult to define for marine mammals but are critical to conservationists and scientists who study natural populations. In the North Pacific Ocean, there are two distinct groups of killer whale (Orcinus orca), one that only eats other marine mammals, such as sea otter and seals, (“transient”) and another that only eats fish species (“residents”). For decades marine mammal scientists have been doing surveys of these populations to map their geographical range but not much is known about the gene flow between the two populations that exhibit very different eating habits. The National Oceanographic and Atmospheric Administration (NOAA) recently funded a study for genetic testing of these populations to better understand the similarity and relatedness coded in the whales’ DNA.

From 2001 and 2010, 462 skin biopsy samples were taken from both residents and transients from the northern Gulf of Alaska to the Sea of Okhotsk. Scientists used both mitochondrial DNA and nuclear microsatellites to analyze the samples. One would think that in the vast open ocean with no true boundaries that gene flow would be common between killer whale populations. However, this study showed that is not the case in the north Pacific Ocean. Data revealed significant levels of population genetic subdivision within the two predominant ecotypes. The fish eating residents are now classified as a single population that ranges from southeast Alaska through the Aleutian Islands and Bering Sea. The marine mammal eating transients showed two genetically distinct stocks that have a slightly overlapping range that begins in the Bering Sea and spreads down to the Prince William Sound. This study helped further map the geographical range and understand the dynamics of the unique populations of killer whales in the northern North Pacific so that NOAA can better manage their habitat. 

Killer whales are cool 

Fatter is Better for Marine Mammals

     For land mammals, we typically see weight gain as a negative thing; it slows us down, it makes us use more energy to get to the same place, and its not too attractive. However, it is found that in northern elephant seals (mirounga angustirostris), the opposite is true.

     Plumping up for the elephant seals is how they remain a better swimmer, and more buoyant. Diving down takes the mammals a considerable amount of energy, but the more buoyant they are, the easier it is for them to come up. This makes it easy for them to dive down deep and can travel far away from their breeding grounds, nearly 4000 km away. A fully plumped female takes half as many strokes per meter and have a much easier time ascending after a dive, another study has shown.
     I think this was interesting how marine mammals differ so much from land mammals even though they are both mammals. Thinned out marine mammals can't swim far, can't hunt deep down, and are overall less able to survive, which is the polar opposite of how weight gain would be detrimental to a human.

Arctic: Sea ice no barrier to bowhead whales mating, study suggests

There has been a significant amount of talk over the past several years regarding global warming and the melting of arctic pack ice. Bowhead whales of the Pacific and the Arctic were thought to be separated by the pack ice. When scientists looked at the genetics of each population, it was shown that they were closely related. Scientists were concerned that the loss of pack ice may have lessened the diversity among bowhead whale populations. In order to determine if this were true, the genetics of ancient bowhead whales was compared to the genetics of modern bowhead whales. It was found that ancient bowhead whales also showed the same relatedness. In fact, it seems that they may all be part of the same family. Researchers theorize that whaling may have made a large enough impact on bowhead whale populations to limit the gene pool.



It is unfortunate that whaling could have made such a significant impact on bowhead whales. What is worse is that some native villages in Alaska are still allowed to hunt for them. Subsistence is completely understandable, however, when it comes to situations like these and endangered species, rules and regulations need to be more strict. Furthermore, it is inevitable that this article will fuel those who believe global warming to be a farse, and may use it as evidence to prove that melting pack ice may not be as terrible as some believe it to be.