Ivory poaching in Africa gained rapid momentum evolution Fangless elephants live in some areas, but increased protection from poachers helps pachydermata to regain their tusks.
“In Africa elephant“Fangless conditions are extremely rare, but when you look at certain areas, the percentage of fangless conditions is much higher than average,” said Brian Arnold, a biomedical data scientist at Princeton University. I am.
To find out why, Arnold and his co-author, Shane Campbell Staton, a biologist at the University of California, Los Angeles, visited Golongosa National Park in Mozambique. Aerial surveys in the 1970s revealed that about 2,500 elephants lived in the park. Arnold and his colleagues used photographs taken during the survey to estimate that during that time, about 18% of the population lacked both fangs, while 9% lost only one. ..
Aerial surveys were suspended due to the outbreak of the Mozambican Civil War that lasted until 1977 and 1992. When census resumed in 2000, the victims of conflict with the Golongosa elephant population were apparent. More than 50% of the survivors lacked tusks and their traits increased almost three-fold.
Arnold believes that much of the population decline during the war is a direct result of poachers killing elephants. Because both sides relied heavily on ivory trade to fund their war effort. However, elephants migrating from the area may have contributed to the overall decline, he said.
“The fangless elephants had obvious survival benefits,” he said. Fangs are usually important for the survival of elephants because they help dig groundwater sources and remove the bark, which is an important part of the elephant’s diet, from the tree. However, when an elephant is hunted for fangs, this beneficial property is sentenced to death.
When they sifted the data, researchers noticed an interesting pattern: all fangless elephants are female. To understand why, Arnold and his colleagues observed the first generation born of war survivors. For each calf, they recorded whether it had tusks, and then whether its parent had tusks.
On average, they found that 50% of daughters born to fangless mothers were as fangless as she was, but all male calves have fangs. In addition, instead of raising male and female calves about the same frequency, two-thirds of fangless mother calves are female.
According to Arnold, this pattern is gene It causes a fangless condition and is carried on the X chromosome. That is, it is an X-chain dominant trait.A female elephant like a human has two Xs Chromosomes.. Therefore, if one of these X chromosomes has a mutated fangless gene and the other X chromosome has a normal gene, the female calf will not be able to develop fangs. However, to survive, the other X chromosome must carry the normal version of the gene. That way, the mutant can be counteracted to some extent. In this case, one mutant gene is sufficient to prevent fang development, but otherwise the elephant is reasonably healthy.
The probability that a mother’s daughter will not have a fang is essentially a coin toss, as the mother has a 50-50 chance of passing either a normal gene or a mutated gene to her offspring. Things are a little dangerous for her son. Using a mutated gene to inherit the X chromosome is a death sentence because the male embryo obtains only one X chromosome from the mother and matches the Y chromosome obtained from the father. Since the Y chromosome does not have the same gene as X, it never has the backup gene that is needed to counteract the fangless gene. And having only a mutated gene is always fatal. Therefore, half of the male embryos (the ones that inherit the fangless X) die before birth, explaining the biased sex ratio of the offspring of the fangless mother.
Researchers have identified two potential genes that can cause fanglessness, AMELX and MEP1a. One of these genes, AMELX, is involved in mammalian tooth development. In humans, this gene plays a role in the development of lateral incisors, which are ivory-evolved teeth. And, interestingly, this gene is also associated with the development of X-linked dominant syndrome, which is fatal to men in humans. This means that for a human male, it is almost the same as for a male elephant. Men who inherit the mutated version on one X chromosome have no backup.
“Theoretically, as fangless women become more common, the chances of giving birth decrease,” Arnold said, saying that fangless women convey a fatal syndrome to half of their male offspring. Said.
“There is something bright about this story,” Arnold said. “Since 1994, elephant populations have increased in Mozambique.” At the same time, tusks-free conditions are declining, probably due to the fact that tusks-free mothers have fewer births. This suggests that the elephants in Golongosa National Park are on track to return to their former fang glory.
Originally published in Live Science.
After poaching rampant ivory, some African elephants lost their tusks — why?
Source link After poaching rampant ivory, some African elephants lost their tusks — why?