Thursday, February 13, 2014

Fossilized goat droppings

The Balearic Islands represent an archipelago of Spain in the western Mediterranean Sea, near the eastern coast of the Iberian Peninsula. The four largest islands are Mallorca, Menorca, Ibiza and Formentera. All of them are among the most famous vacation destinations in Europe.

Humans colonized the Balearic Islands about 4000-5000 years ago. Their arrival had a profound impact on the fauna of the major islands Mallorca and Menorca. Diverse datings indicate that three native and endemic terrestrial mammals of Majorca disappeared shortly after the arrival of humans. The Majorcan giant dormouse (Hypnomys morphaeus) with a body length of up to 30 cm and the giant shrew (Nesiotites hidalgo) seem to represent cases of insular gigantism which is a phenomenon in which the size of animals isolated on an island increases dramatically in comparison to their mainland relatives. A compelling explanation for this phenomenon is that it represents an evolutionary trend that results from the removal of constraints on the size of small animals related to predation and/or competition. 

The third mammal species  that disappeared about 4000 years ago was the Balearic Islands mountain goat (Myotragus balearicus), also known as the Balearic Islands cave goat, a species of the subfamily Caprinae which lived on the islands of Mallorca and Menorca. Several hypotheses have been proposed to explain the extinction of Myotragus balearicus but apparently none of them was fully accepted simply because of a lack of data. A new study sheds some more light on the fate of the goat that was actually more related to sheep than to goats:

For the present study ancient DNA analysis (Sanger sequencing, Roche-454, Ion Torrent), and pollen and macrofossil analyses were performed on preserved coprolites from Myotragus balearicus, providing information on its diet and paleo-environment.

The results of the study (and yes they used plant DNA Barcoding markers on the fossilized poop) are quite intriguing and it seems that more than one factor was likely involved in the extinction of the species. Hypotheses relating the extinction of Myotragus balearicus directly to the arrival of humans on the islands might need a bit of adjustment.

The information retrieved shows that Myotragus balearicus was heavily dependent on the Balearic box species Buxus balearica during at least part of the year, and that it was most probably a browser. Hindcast ecological niche modelling of B. balearica shows that local distribution of this plant species was affected by climate changes. This suggests that the extinction of Myotragus balearicus can be related to the decline and regional extinction of a plant species that formed a major component of its diet. The vegetation change is thought to be caused by increased aridity occurring throughout the Mediterranean. 

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