The quiet life of the Sicilian dwarf elephant, secret of its longevity

The islands are natural laboratories exceptional for the study of evolution. Its characteristics of geographic isolation , which makes it difficult for species to migrate, the limitation of physical space that often prevents the presence of predators – which require large areas of land to hunt – or the limitation of food resources of the island ecosystems, configure some evolutionary patterns common in the fauna that live in them.

One of these phenomena is dwarfism or gigantism. Very often on islands we observe species larger or smaller than their continental counterparts, especially in terms of mammals and dinosaurs.

In the mid-nineteenth century, Charles Darwin and Alfred Wallace were already interested in this phenomenon after their trips to various islands in the world, which was where they obtained evidence which they later used to propose the t theory of evolution .

A peculiar evolutionary pattern

In 1973, building on Foster’s earlier work, evolutionary biologist Leigh Van Valen coined the term ` island rule ´ —often translated as ‘insular law’ or ‘island effect’ – which confirmed the tendency to gigantism or dwarfism of the species that evolved on the islands.

One of the emblematic species of this ‘island effect’ is the Sicilian dwarf elephant , ( Palaeoloxodon falconeri ). It is an extremely small species compared to current elephant species, measuring approximately one meter in height and weighing about 250 kilograms.

This dwarf elephant lived in Sicily during the Pleistocene , between 500,000 and 200,000 years ago and is known from the fossil remains that have been found in different sites of the Island.

Palaeoloxodon falconeri is a descendant of the continental species Palaeoloxodon antiquus , much larger (up to five meters high at the withers and 5 tons of weight).

Now, an article published in Scientific Reports led by research staff from the Institut Català de Paleontologia Miquel Crusafont ( ICP ), a center attached to the Autonomous University of Barcelona ( UAB ), in collaboration with various international research institutions, describes the characteristics of the “vital history” of this species.

This concept refers to the characteristics of the different events that occur during the life cycle of an animal, such as its growth rate, age of sexual maturity or longevity.

The study concludes that the Sicilian dwarf elephant grew very slowly, reached sexual maturity around 15 years and had a long life expectancy of at least 68 years.

“Traditionally it had been considered that this species had a rapid development, reaching early sexual maturity and had a short life,” explains researcher Meike Köhler , who is leading the research. “Our work shows that the life history of this elephant was much slower,” he notes.

Knowing their life cycle through tusks

The research team has analyzed the paleohistology ―the internal structure of fossils― of molars and defenses (what we popularly call ‘fangs’) of this species.

“The different events in the life cycle of an organism are recorded in its bones, such as what happens with the growth rings that we observe in the trunks of trees”, explains Köhler.

The fossils are cut into thin slices of a thickness of approximately 0.1 mm, to analyze under the microscope the lines of growth stops or LAGs (acronym in English for `Lines of Arrested Growth ´) that allow to identify the growth and latency periods of the animal.

In general, small continental species tend to have more accelerated life histories : they grow fast, reproduce early and die young. “But the opposite happens in the islands”, explains the co-author of the research Salvador Moyà .

Unlike what happens on the continents, the change in body size of the species that live on the islands is not associated with a faster life history.

“We have found that the Sicilian dwarf elephant had a much slower life history than its sister taxon Palaeoloxodon antiquus and that the huge African savanna elephant”, says Moyà. “The slow pace of this animal is the key to its longevity. Maybe humans can learn something from them! ”, The researcher jokingly concludes.

Source: SINC

Rights: Creative Commons.