Silver-bordered fritillary
Boloria selene, known in Europe as the small pearl-bordered fritillary and in North America as the silver-bordered fritillary, is a species of butterfly of the family Nymphalidae. It is found across Europe, Asia and North America, and feeds exclusively on violets in its larval stages. This species prefers wet grassland habitats, where its larval food source, violets, are found. It overwinters in its larval stage, and eggs hatch in the late summer to early autumn. Members of this species are prey for multiple types of birds and other insects.
Due to modern agriculture, most of the grassland habitats that sustain Boloria selene are fragmented or lost all together in favor of farmland. Because of this, the small pearl-bordered fritillary has seen a serious drop in population across Europe, in some places as much as 80%. Factors including limited habitat range, low dispersal rate, and strong food specialization also contribute to population loss. Despite modern conservation efforts, the number of small pearl-bordered fritillaries is still declining. The North American populations appear to be affected in the same way, at least in the continental United States.
Te
TerrestrialTerrestrial animals are animals that live predominantly or entirely on land (e.g., cats, ants, snails), as compared with aquatic animals, which liv...
Ov
OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
S
starts withThe small pearl-bordered fritillary is similar to the pearl-bordered fritillary but has black chevrons on the edge of its wings, a large central black dot on each wing, and white pearls on the underside. Males tend to be smaller than females, with a wingspan of 35 to 41 mm. Females are 38 to 44 mm in length. Though the small pearl-bordered fritillary is similar to the pearl-bordered fritillary it is much brighter in color because the pearl-bordered fritillary emerges from its pupa earlier. Seitz - A. selene Schiff. (= euphrosyne Bgstr., euphrasia Lew., silene Haw.) (67g). Forewing above and beneath very similar to tliat of the preceding. Hindwing beneath with the median band distinct but not broad, the costal spot of the band, the large tooth above the apex of the cell and the one below the cell-end being vividly silvery like the marginal lunules; the broad interspace between the median band and the marginal lunules is leatheryellow and bears below the apex and above the anal angle two large dark cinnamon clouds; obsolescent silvery selenia bands extend from the costal and abdominal margins towards the centre of the wing.
The species is widespread across central and northern Europe, North America, and through Asia to Korea. Specifically, it can be found in places like Germany, the United Kingdom, and Sweden and in the Midwestern United States in places like Iowa and the Dakotas. In the United Kingdom, Boloria selene is widespread across upland and western Britain, but is not found in central, eastern England or Ireland. Its range appears to be stable through much of Europe but declines have been reported in at least nine countries, such as England.
This species is found across Europe and North America in grassland environments where native violets grow. It occurs in damp, grassy habitats, woodland clearings and moorland, but has also been found in dune slacks and coastal cliffs.
This species is well known to migrate short distances during its reproductive stage, but does not appear to make any long distance migrations that cross over unsuitable habitats such as farmland and urban areas.
There appears to be no place (at least in Europe) that is not suffering from at least light population degradation. Many studies in the UK (where population loss is most severe) and several studies from other areas of Europe state that the small pearl-bordered fritillary is rapidly declining in numbers. This is likely from indirect harm due to habitat destruction and fragmentation. Since this species is primarily attached to violet that grows in wild grasslands, modern agricultural practices which have caused most of Europe's grasslands to become fragmented or destroyed for farmland have a severe effect on the butterfly. Without native violets to host their larvae, this species is facing decline across Europe. This species also struggles with breeding across habitat fragments as it must lay eggs exclusively on violets in order to have any viable offspring. However, adults seem to be quite flexible in their movement patterns, with one study stating that only 45% of released Boloria selene specimens were able to be found and recaptured. This indicates that farmland itself appears to more strongly damage reproduction rates instead of general adult survival.
Another study found that this species has another characteristic which makes it vulnerable to extinction: it is not only a dietary specialist, also migrates only small distances. This creates problems for the species, since fragmentation most strongly affects animals that migrate short distances and are unable to cross the gaps made by human habitat destruction. While long distance migratory species are often unaffected and sedentary species are often able to better use the fragments they are in, short distance migrators like the small pearl-bordered fritillary are unable to properly disperse and are hit hardest from environmental damage.
A study in Germany found that over 40 years (1971-2011), populations of adults dropped rapidly in agricultural land, while dropping slightly less severely in native grasslands (although still decreasing by almost 83%). The article stated that fragmented habitat protection does a poor job of securing biodiversity and protecting many species that are in peril, as it does not account for many species that cannot seek extra fragmented breeding sites. Many species, including Boloria selene, fail to find good nesting sites as they cannot pass through the human habitat that divides suitable fragments.
These drastic changes stem from the continued expansion of agriculture over time that continued to damage and degrade the remaining native breeding habitat for Boloria selene. However, the species seems to fare well as adults in a variety of artificial and natural habitats, with the same study showing slightly larger numbers of the species in farmland than in wild habitat in 1971. Another big issue is that Boloria selene struggles with sibling mating, as shown when almost no viable offspring came from sibling mating. This could be detrimental to a population that already has reduced individual genetic diversity, as sibling mating will become more common as fragmentation chips away at short distance migration and gene flow in this species.
