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Altitudinal Barrier to the Spread of an Invasive Species: Could the Pyrenean Chain Slow the Natural Spread of the Pinewood Nematode?

Haran J, Roques A, Bernard A, Robinet C, Roux G - PLoS ONE (2015)

Bottom Line: Conversely, strong admixture was detected between populations located on both sides of low elevation hills, and especially at the east and west extremities of the mountain range.Simulations also showed that temperature rise due to climate change may significantly reduce the extent of the barrier formed by highest elevations.Our results support the hypothesis that the Pyrenean chain represents a partial barrier to the natural spread of nematode-infested beetles.

View Article: PubMed Central - PubMed

Affiliation: INRA, UR633 Zoologie Forestière, F-45075 Orléans, France; Université d'Orléans, Orléans, France.

ABSTRACT
Mountain ranges may delimit the distribution of native species as well as constitute potential barriers to the spread of invasive species. The invasive pinewood nematode, Bursaphelenchus xylophilus, is a severe forest pest inducing pine wilt disease. It is vectored in Europe by a native long-horned beetle, Monochamus galloprovincialis. This study explored the potential of the Pyrenean chain to slow or prevent the natural spread of nematode-infested beetles from the Iberian Peninsula, where the nematode is established and is expanding its range, towards France and the rest of Europe. An analysis of the genetic structure and migration patterns of the beetle populations throughout the Pyrenean mountain range was combined with a spread model simulating the potential movements of nematode-infested beetles across it. The central part of the Pyrenees, which corresponds to the highest elevation zone, was shown to prevent gene flow between the French and Spanish populations of M. galloprovincialis on each side of the mountains. Conversely, strong admixture was detected between populations located on both sides of low elevation hills, and especially at the east and west extremities of the mountain range. Simulations of the spread of nematode-infested beetles under various thresholds of beetle survival and pine wilt disease expression gave results consistent with the variation in genetic make-up, suggesting that western and eastern hillsides may represent corridors favoring natural spread of the nematode from the Iberian Peninsula to France. Simulations also showed that temperature rise due to climate change may significantly reduce the extent of the barrier formed by highest elevations. Our results support the hypothesis that the Pyrenean chain represents a partial barrier to the natural spread of nematode-infested beetles. These results, which have to be considered together with potential human-assisted long-distance spread of the nematode, highlight priority zones for future pest monitoring and management programs. More generally, such an integrated approach could be used to assess the role of mountain chains in the potential spread of other invasive pests.

No MeSH data available.


Related in: MedlinePlus

Pairwise Fst and likelihood of hybrid populations along the 4 transects (green line).Numbers on the top left of each circle refer to population code (see Fig 1). Values attached to brackets refer to the unbiased estimates of pairwise Fst calculated under ENA correction (NS = non-significant). The red dotted line shows the placement of the highest ridgeline. Values in the circles and their relative size show the percentage of likelihood to belong to the parent population of the opposite of the ridgeline. Populations used as parents to determine likelihood of hybrid populations are represented as black spots.
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pone.0134126.g002: Pairwise Fst and likelihood of hybrid populations along the 4 transects (green line).Numbers on the top left of each circle refer to population code (see Fig 1). Values attached to brackets refer to the unbiased estimates of pairwise Fst calculated under ENA correction (NS = non-significant). The red dotted line shows the placement of the highest ridgeline. Values in the circles and their relative size show the percentage of likelihood to belong to the parent population of the opposite of the ridgeline. Populations used as parents to determine likelihood of hybrid populations are represented as black spots.

Mentions: Pairwise Fst computed under the ENA correction of the 26 populations was higher than 0.05 for 86% of population pairs, but differentiation was significant (p<0.0001) only for 28.8% of pairs (S1 Table). We observed a ratio of significant pairwise differentiation that was higher between populations of the two sides of the mountain range (72.6%) than between populations of the same side (3.4%). The differentiation was generally moderate to low, the mean pairwise Fst over the whole dataset was 0.0657 (SD: 0.0423). Mean pairwise Fst among populations of the same side was 0.0375 (SD: 0.0263), while this distance was 0.0922 (SD: 0.0372) between populations on the two sides. The maximum differentiation (Fst = 0.185) was observed between Castillonroy (Spain) and Garros (France). Along transects, we did not observe significant pairwise Fst between populations of the same side (except between Falces and Beriain, Fig 2). Isolation by distance was significant for the whole dataset (p = 0.009), between populations within the Northern side (p = 0.037) and within the Southern side (p = 0.003).


Altitudinal Barrier to the Spread of an Invasive Species: Could the Pyrenean Chain Slow the Natural Spread of the Pinewood Nematode?

Haran J, Roques A, Bernard A, Robinet C, Roux G - PLoS ONE (2015)

Pairwise Fst and likelihood of hybrid populations along the 4 transects (green line).Numbers on the top left of each circle refer to population code (see Fig 1). Values attached to brackets refer to the unbiased estimates of pairwise Fst calculated under ENA correction (NS = non-significant). The red dotted line shows the placement of the highest ridgeline. Values in the circles and their relative size show the percentage of likelihood to belong to the parent population of the opposite of the ridgeline. Populations used as parents to determine likelihood of hybrid populations are represented as black spots.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4519352&req=5

pone.0134126.g002: Pairwise Fst and likelihood of hybrid populations along the 4 transects (green line).Numbers on the top left of each circle refer to population code (see Fig 1). Values attached to brackets refer to the unbiased estimates of pairwise Fst calculated under ENA correction (NS = non-significant). The red dotted line shows the placement of the highest ridgeline. Values in the circles and their relative size show the percentage of likelihood to belong to the parent population of the opposite of the ridgeline. Populations used as parents to determine likelihood of hybrid populations are represented as black spots.
Mentions: Pairwise Fst computed under the ENA correction of the 26 populations was higher than 0.05 for 86% of population pairs, but differentiation was significant (p<0.0001) only for 28.8% of pairs (S1 Table). We observed a ratio of significant pairwise differentiation that was higher between populations of the two sides of the mountain range (72.6%) than between populations of the same side (3.4%). The differentiation was generally moderate to low, the mean pairwise Fst over the whole dataset was 0.0657 (SD: 0.0423). Mean pairwise Fst among populations of the same side was 0.0375 (SD: 0.0263), while this distance was 0.0922 (SD: 0.0372) between populations on the two sides. The maximum differentiation (Fst = 0.185) was observed between Castillonroy (Spain) and Garros (France). Along transects, we did not observe significant pairwise Fst between populations of the same side (except between Falces and Beriain, Fig 2). Isolation by distance was significant for the whole dataset (p = 0.009), between populations within the Northern side (p = 0.037) and within the Southern side (p = 0.003).

Bottom Line: Conversely, strong admixture was detected between populations located on both sides of low elevation hills, and especially at the east and west extremities of the mountain range.Simulations also showed that temperature rise due to climate change may significantly reduce the extent of the barrier formed by highest elevations.Our results support the hypothesis that the Pyrenean chain represents a partial barrier to the natural spread of nematode-infested beetles.

View Article: PubMed Central - PubMed

Affiliation: INRA, UR633 Zoologie Forestière, F-45075 Orléans, France; Université d'Orléans, Orléans, France.

ABSTRACT
Mountain ranges may delimit the distribution of native species as well as constitute potential barriers to the spread of invasive species. The invasive pinewood nematode, Bursaphelenchus xylophilus, is a severe forest pest inducing pine wilt disease. It is vectored in Europe by a native long-horned beetle, Monochamus galloprovincialis. This study explored the potential of the Pyrenean chain to slow or prevent the natural spread of nematode-infested beetles from the Iberian Peninsula, where the nematode is established and is expanding its range, towards France and the rest of Europe. An analysis of the genetic structure and migration patterns of the beetle populations throughout the Pyrenean mountain range was combined with a spread model simulating the potential movements of nematode-infested beetles across it. The central part of the Pyrenees, which corresponds to the highest elevation zone, was shown to prevent gene flow between the French and Spanish populations of M. galloprovincialis on each side of the mountains. Conversely, strong admixture was detected between populations located on both sides of low elevation hills, and especially at the east and west extremities of the mountain range. Simulations of the spread of nematode-infested beetles under various thresholds of beetle survival and pine wilt disease expression gave results consistent with the variation in genetic make-up, suggesting that western and eastern hillsides may represent corridors favoring natural spread of the nematode from the Iberian Peninsula to France. Simulations also showed that temperature rise due to climate change may significantly reduce the extent of the barrier formed by highest elevations. Our results support the hypothesis that the Pyrenean chain represents a partial barrier to the natural spread of nematode-infested beetles. These results, which have to be considered together with potential human-assisted long-distance spread of the nematode, highlight priority zones for future pest monitoring and management programs. More generally, such an integrated approach could be used to assess the role of mountain chains in the potential spread of other invasive pests.

No MeSH data available.


Related in: MedlinePlus