Gene flow rise with habitat fragmentation in the bog fritillary butterfly (Lepidoptera: Nymphalidae)

Abstract

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.

Loss of genetic diversity through spontaneous colonization in the bog fritillary butterfly, Proclossiana eunomia (Lepidoptera: Nymphalidae) in the Czech Republic

“…Barascud et al, 1999), the Šumava populations exhibit a very significant isolation by distance effect, as observed for many resident butterfly species (Nève, 2009). Moreover, the Šumava populations harbour a higher genetic diversity than the intensively studied P. eunomia populations in the Ardennes region, and the same holds true for P. eunomia populations in other European mountain ranges such as the Asturias, Pyrenees, and Stara Planina (Descimon et al, 2001;Nève et al, 2008).…”

“…Succession is slow in mountain wet meadows, and includes temporarily blocked stages -the tussocky habitats with high cover of Polygonum bistorta. In terms of population genetics, it can be expected that as individuals continue to disperse between established populations, an equilibrium between drift and migration will be attained, with the effect of isolation by distance caused by multiple founding effects gradually disappearing, as observed in other regions (Nève et al, 2008). Hastings & Botsford (2006) show that return flights contribute to long-term metapopulation persistence, leading thus to an equilibrium situation.…”

“…PGM is monomorphic regionally (whereas it is polymorphic in all other populations studied in Europe; Nève et al, 2008), PGI, GOT and AK showed two alleles each, and 6PGD three. Other populations of P. eunomia have also been investigated, notably from the Ardennes, Morvan, Pyrenees, and Asturias mountains (Nève et al, 2008), and a single population from the Stara Planina (Bulgaria). In addition to the mentioned loci, all these populations were also tested for polymorphism in the G6PDH, HBDH, AAT (2nd loci), and GPDH (which all proved monomorphic in the Czech sample).…”

“…Proclossiana eunomia is a Holarctic species, distributed from Europe through northern Asia to Alaska, Canada and Rocky Mountains states of USA (Tuzov & Bozano, 2006;Nève et al, 2008). It is the only species of the genus Proclossiana Reuss, 1921, sometimes considered as a subgenus of Boloria Moore, (1900), together with its sister genus Clossiana Reuss, 1920(Simonsen, 2005.…”

“…Within this relict range, it is threatened by habitat loss or mismanagement (Schtickzelle et al, 2007). Extensive studies of its demographic and genetic population structure, carried out in Belgium, Finland and France (Schtickzelle et al, 2006), revealed a high rate of movement among local colonies and hence a low genetic differentiation within landscapes (Nève et al, 2008). An extreme case was the study carried out in Morvan, France, where the species was introduced in 1970 and 1974 (Descimon, 1976) into a previously unoccupied region.…”