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.

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Recent Study May have Implications for Invasion-Related Concepts in Evolutionary Theory

18 03 2010
This image is by Bruce Marlin and is courtesy of Wikimedia Commons.  It is licensed under the Creative Commons Attribution-Share Alike 2.5 Generic license.

Harmonia axyridis, also known as the Lady Bug and the Harlequin Ladybird

A recent article in PLoS One hypothesis a “bridgehead” effect in certain, highly successful, invasive species that allow them to use one invasion as a staging ground to mount additional invasions.  Following is the original abstract for the article, along with a link to the entire piece:

Abstract

Recent studies of the routes of worldwide introductions of alien organisms suggest that many widespread invasions could have stemmed not from the native range, but from a particularly successful invasive population, which serves as the source of colonists for remote new territories. We call here this phenomenon the invasive bridgehead effect. Evaluating the likelihood of such a scenario is heuristically challenging. We solved this problem by using approximate Bayesian computation methods to quantitatively compare complex invasion scenarios based on the analysis of population genetics (microsatellite variation) and historical (first observation dates) data. We applied this approach to the Harlequin ladybird Harmonia axyridis (HA), a coccinellid native to Asia that was repeatedly introduced as a biocontrol agent without becoming established for decades. We show that the recent burst of worldwide invasions of HA followed a bridgehead scenario, in which an invasive population in eastern North America acted as the source of the colonists that invaded the European, South American and African continents, with some admixture with a biocontrol strain in Europe. This demonstration of a mechanism of invasion via a bridgehead has important implications both for invasion theory (i.e., a single evolutionary shift in the bridgehead population versus multiple changes in case of introduced populations becoming invasive independently) and for ongoing efforts to manage invasions by alien organisms (i.e., heightened vigilance against invasive bridgeheads).

Read the entire article by following this link:
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0009743