Imperfect Imitation is (Sometimes) the Best Form of Flattery

21 03 2012

A letter published March 21 in the online edition of the journal Nature indicates that there are evolutionary reasons why some animals that mimic other more aggressive or dangerous species do so rather imperfectly.

The study conducted by a team of Canadian researchers indicated that, at least in hoverfly populations, predators impose less selection if the mimic is smaller.  Thus, small mimic species need to have less fidelity with the species they are mimicking than do larger ones.  The team concludes that the most likely reason for this is that the mimics are less profitable prey species and are not apt to be pursued as strongly as are larger species.  So, less fidelity will do.

The team was also able to show little or no correlation of mimicry to several other theories that had been posited over the years as explanations for the imperfections.  Among these, they were able to show that human ratings of mimetic fidelity are positively correlated with both morphometric measures and avian rankings of the mimicry, indicating that variation in mimetic fidelity is not just an illusion based on human perception.

See here for the complete paper.





Like Mice Off a Not So Sinking Ship

19 03 2012
House_mouse_Mus_musculus

The humble house mouse (Mus musculus), traveling the globe with man. Image is courtesy of Wikimedia Commons and is in the public domain.

An international team of researchers led by scientists at the University of York in the United Kingdom have used mitochondrial DNA to show that the timeline of house mice migration across the upper north Atlantic through Scotland and the Scottish Islands, to Iceland, Greenland, and Newfoundland closely matches that of the Viking invasion.

The Vikings, who fought, raided, and explored their way across the north Atlantic from the late eighth to the mid-tenth centuries were the scourge of most of Europe at that time, raiding, killing, and pillaging large swaths of the continent, not just the areas above, but also parts of England, Wales, the Isle of Man, and Ireland.  They established the first cities in Ireland.  They founded the duchy of Normandy, in France, and they even established a kingdom in Sicily in the Mediterranean Sea.

It seems that where they went, their house mice (scientific name Mus musculus) went with them, at least on the northern part of their journey.

According to a press release (see here) the research team, made up of members from the UK, US, Iceland, Denmark, and Sweden, used techniques designed to characterize genetic similarity, and thereby infer the relatedness of one population, or one individual, with another, in order to determine a mouse colonisation timeline.

They obtained modern samples of house mic DNA and compared them to ancient samples dating mostly from the 10th to 12th centuries.  Samples were collected from nine sites in Iceland, Narsaq in Greenland, and four sites near the Viking archaeological site, L’Anse aux Meadows, in Newfoundland.  Ancient samples came from the Eastern and Western settlements in Greenland and four archaeological sites in Iceland.

When analyzed, the samples showed that house mice traveled with the Vikings to Iceland in the early 10th century , either from Norway or the northern part of the British Isles.  From Iceland the mice continued their journey on Viking ships to settlements in Greenland.  However, while descendants of these stowaways can still be found in Iceland, the early colonizers in Greenland have become extinct and their role has been filled by Danish house mice (same species) brought much later by a second wave of European human immigrants.

Of significance is the fact that no evidence of house mice was found in the Viking settlement in Newfoundland, nor was there any evidence of ancestral Viking house mice DNA in modern house mice there.  So, it seems that if the mice made if as far as Newfoundland, they became extinct before they could contribute to the modern house mice lineage on the island.

Replica of a Viking Long Ship

Replica of a Viking long ship. Photograph by archiwum własne wikingów, Jarmeryk, from Wikimedia Commons.





Scientists Discover Link Between Malaria and Red Tides

1 06 2010

A team of scientists has discovered the common ancestor of two creatures that cause the world a considerable amount of trouble and suffering, the malaria parasite and the organism that causes red tides.  The missing link, the thing that connected the two, turned out to be little brown balls called Chromera.

The team, consisting of scientists from the University of British Columbia in Canada and the University of South Bohemia, in the Czech Republic, published their findings in the online early edition of the Proceedings of the National Academy of Sciences (PNAS), an American publication.

Chromera is a symbiont found inside corals. While it has a compartment (called a plastid) used to perform photosynthesis like the dinoflalgellate algae that causes red tide (as well as photosynthesis in plants), Chromera is closely related to apicomplexan parasites, which include malaria.  This discovery, first published in the journal Nature in 2008, gave researchers the idea that the algae and the parasites might be related and that the Chromera was the connection.

The scientists sequenced the genome of Chromera and were able to show for the first time, how the two are connected evolutionarily.

In recent interviews, the scientists said that they hope the knowledge gained by their research will not only advance basic scientific knowledge, but will also open the way for treatments for diseases such as malaria.

The original PNAS article is available here.