Quaternary history and contemporary patterns in a currently expanding species

Abstract

Background: Quaternary climatic oscillations had dramatic effects on species evolution. In northern latitudes, populations had to survive the coldest periods in refugial areas and recurrently colonized northern regions during interglacials. Such a history usually results in a loss of genetic diversity. Populations that did not experience glaciations, in contrast, probably maintained most of their ancestral genetic diversity. These characteristics dramatically affected the present-day distribution of genetic diversity and may influence the ability of species to cope with the current global changes. We conducted a range-wide study of mitochondrial genetic diversity in the pine processionary moth (Thaumetopoea pityocampa/T. wilkinsoni complex, Notodontidae), a forest pest occurring around the Mediterranean Basin and in southern Europe. This species is responding to the current climate change by rapid natural range expansion and can also be accidentally transported by humans. Our aim was to assess if Quaternary climatic oscillations had a different effect across the species' range and to determine if genetic footprints of contemporary processes can be identified in areas of recent introduction.

Genetic diversity of Thaumetopoea pityocampa in Greece: the role of Quaternary changes in Aegean Sea

“…This underlines the possibility of certain Aegean islands being influenced by populations from the Turkish mainland rather than the Greek, especially the islands and mainland areas were connected during the last glacial drop in sea level [44]. Thaumetopoea pityocampa's glacial refuges have been identified as Italy, the Iberian Peninsula and the Balkans [5]. Greece may also have served as such a refuge, although there is no strong geographical barrier to limit gene flow within this region like the Alps in Italy or the Pyrenees in the Iberian Peninsula.…”

“…However, since the Aegean Sea between the island of Lesvos and the mainland of Turkey shows a depth of only 0-100 m, changes in sea level during the Pleistocene may have facilitated genetic exchange [44]. A previous study [5] found both main haplotypes in Lesvos and in the neighboring area of Bayramic, Cannakale, in Turkey. This underlines the possibility of certain Aegean islands being influenced by populations from the Turkish mainland rather than the Greek, especially the islands and mainland areas were connected during the last glacial drop in sea level [44].…”

“…than the ones found in the present study it is most likely that the large-scale divergences referring to species and larger areas took place a few million years ago and smaller, more regional/small-scale divergences have been continuing into more recent times. This also explains the comparably small number of 15 haplotypes found in 15 populations whereas studies carried out on larger areas in general find a higher number of haplotypes [2,5,24].…”

“…In Greece, the moth can be found almost everywhere except parts of Central Greece and some islands of the Aegean Sea due to improper weather conditions or geographical isolation [3,4]. However, exceptions lie in the southern parts of the country, for example on the island of Crete, where only the sister species Thaumetopoea wilkinsoni can be found [5]. As a defoliating insect the winter pine processionary is considered one of the major forest pests in this region [6].…”

Distribution of two pine processionary moth species inTurkey evidences a contact zone

“…Yet, no sample from northwestern Turkey was included in this work. Kerdelhué et al (2009) were the first to mention that the ranges of the two species could intersect in Turkey. Due to insufficient sampling in northwestern Turkey, and the use of a single mitochondrial marker, the possibility of a contact zone between T. pityocampa and T. wilkinsoni was still questionable.…”