African animals-Lemurs

Sunday Primate: The Rise and Fall of the Lemurs

Approximately one hundered and sixty million years ago Madagascar separated from the African continent. The resulting ecological isolation caused the evolution of a number of unique plants and animals found nowhere else in the world. Lemurs, a prosimina primate of the suborder Strepsirrhini are notable characters among these isolationist species, for they provide some insight into the history of primate as a whole. However, in examining Lemurs, the mistake is often made that they are somehow a more primitive species. This is completely untrue for they have had long enough to evolve as the rest of us. It’s just that their evolutionary story took a different path.

Needless to say, lemur evolutionary history is a somewhat contentious issue. Originally it was believed that lemurs and other Strepsirrhine primates evolved from adapiforms sometime during the Eocene (56 – 34 may), or perhaps even earlier in the Paleocene (65 – 56 mya). However, adapiforms are missing the characteristic toothcomb which almost all strepsirrhines possess. Now it is more widely accepted that lemurs descended from loris-like primates. This view is additionally supported by comparative studies of the cytochrome b gene. Molecular phylogenetic studies have further shown that adapiforms gave rise to early strepsirrhines, which then diverged into the proto-lemur group and the lorisforms. Both genetic tests and fossil evidence suggest this divergence happened roughly 50 mya years ago.

All of this means lemurs weren’t native to Madagascar at the time of its separation. However, they arrived there roughly 40 million years ago, and perhaps this works as the best dividing line in deciding where to draw the cladistic boundaries of lemurdom. How exactly the lemurs arrived is another contentious issue, some suggest land bridges whereas others have argued for the always popular vegetative rafts.

Upon arriving on Madagascar lemurs diversified and divergence into a number of behavorial and morphologically distinct primates. At the extreme ends of this differential morphology, are the Mouse lemur (1.1 oz) and the now extinct Archaeoindris fontoynonti (440 lb). As the island was devoid of ungulates, squirrels, and woodpeckers, among other animals, these ecological niches were filled by lemurs. Different forms of lemurs evolved side by side in what is referred to as sympatric speciation. Sympatric speciation stands in contrast to allopatric speciation, where geographical isolation is the leading cause of divergence. Quite the contrary, lemurs were not separated by mountains or rivers, but by the ecological niches they chose to exploit.

Approximately two thousand years ago, another species of primate found their way to Madagascar. These primates, known as Homo sapiens, began the process of adapting the environment to their own agricultural and industrial needs. This lead to the extinction of a number of lemur species and drastically reduced their habitat. Whereas previous to this invasion lemurs could be found across the entire island they now occupy less than 10% of Madagascar, an area of roughly 60,000 km squared. Nearly all species of lemur are now listed by the International Union for Conservation of Nature as being in danger of extinction. Continued deforestation, hunting, and sale in the exotic pet trade are the three most commonly cited problems facing lemurs in the twenty-first century. It looks like the odds are highly stacked against lemurs making it to the twenty-second century. It's likely we'll see a greater number of species of this once highly diverse suborder going extinct within our lifetim