The Corsican swallowtail butterfly, Papilw hospiton, is endemic to Corsica and SarcJnia (France and I s y ) and i n c b e d in th6iist ofgdangered species by the Washin on Convention. It is spread all over Corsica in scattered populations linked to diverse habitats. A stu y y eqzyme electro&oresis showed t h z the genetic diversity of the species is of the same z d e r of magnitude =that of P a p l i y h a o n from continental France and Corsja. The differentiation between populations is rather low, which is consistent with the high F & t y of the adults. Natural h y b e t i o n between I! h p b n and I! mnhaon is frequent, and laboratory crosses show that the hybrids are not sterile. However, developmental perturbations impair the m i t y of further hybrid progenies. Although limited introqession between the two species is likely to take place, e n p e electrophoresis and P%LFLP a n d m of mitochon2al DNA show that their gene pools remain distinct'%enetic assimilafion by I! machaon therefore does not seem to be + i T + a threat for I! hospiton.
Populations of Proclossiana eunomia (Lepidoptera, Nymphalidae) occur in middle Europe in patchy habitats of hay meadows along valleys or peat bogs. Samples of P. eunomia populations from the Ardennes region (northern France and southern Belgium) were analysed by allozyme electrophoresis. Patches isolated by more than 2 km of mature forests proved genetically distinct from their neighbouring populations. Mantel tests and regression analysis showed that the degree of genetic differentiation between the 26 studied populations is related to the geographical distances between them. Autocorrelation analysis (Moran's I ) showed that allele frequencies are positively correlated for populations up to 13 km apart and that the genetic neighbourhood of individuals is in the range of 0.9 km, which is in accordance with movement studies in this species conducted in the same area. Analysis using Wright's F-statistics revealed that the highest differentiation occurs between populations of the same subregion, whereas the whole Ardennes region is not genetically partitioned into subregions. This is probably because the connectivity of the network of suitable habitats has significantly weakened only since the 1950s, and thus subregional differentiation has not yet occurred.
BackgroundThe main components of the spatial genetic structure of the populations are neighbourhood size and isolation by distance. These may be inferred from the allele frequencies across a series of populations within a region. Here, the spatial population structure of Proclossiana eunomia was investigated in two mountainous areas of southern Europe (Asturias, Spain and Pyrenees, France) and in two areas of intermediate elevation (Morvan, France and Ardennes, Belgium).ResultsA total of eight polymorphic loci were scored by allozyme electrophoresis, revealing a higher polymorphism in the populations of southern Europe than in those of central Europe.Isolation by distance effect was much stronger in the two mountain ranges (Pyrenees and Asturias) than in the two areas of lower elevation (Ardennes and Morvan). By contrast, the neighbourhood size estimates were smaller in the Ardennes and in the Morvan than in the two high mountain areas, indicating more common movements between neighbouring patches in the mountains than in plains.ConclusionShort and long dispersal events are two phenomena with distinct consequences in the population genetics of natural populations. The differences in level of population differentiation within each the four regions may be explained by change in dispersal in lowland recently fragmented landscapes: on average, butterflies disperse to a shorter distance but the few ones which disperse long distance do so more efficiently. Habitat fragmentation has evolutionary consequences exceeding by far the selection of dispersal related traits: the balance between local specialisation and gene flow would be perturbed, which would modify the extent to which populations are adapted to heterogeneous environments.
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