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Ecology and conservation of the moth Dysauxes ancilla

Betzholtz, Per-Eric LU (2004)
Abstract (Swedish)
Popular Abstract in Swedish

Ekologin hos lavdagsvärmaren (Dysauxes ancilla) studerades inom den enda svenska populationen vid Beijershamn på Öland. Populationen utgör en isolerad förekomst på nordgränsen av artens utbredningsområde, som huvudsakligen är mellan- och sydosteuropeiskt. Arten är rödlistad som akut hotad. Resultaten visar att lavdagsvärmaren för närvarande endast förekommer inom ett 4 ha stort område, med en populationsstorlek på 1000-2000 exemplar. Habitatet utgörs av torrängar med låg vegetation, med inslag av enstaka samlingar av ek- och enbuskar. Torrängarna gränsar mot mer sammanhängande lövskog, vilken domineras av ek. Delar av torrängarna ligger på en strandvall från Littorinaperioden, vilken sluttar mot... (More)
Popular Abstract in Swedish

Ekologin hos lavdagsvärmaren (Dysauxes ancilla) studerades inom den enda svenska populationen vid Beijershamn på Öland. Populationen utgör en isolerad förekomst på nordgränsen av artens utbredningsområde, som huvudsakligen är mellan- och sydosteuropeiskt. Arten är rödlistad som akut hotad. Resultaten visar att lavdagsvärmaren för närvarande endast förekommer inom ett 4 ha stort område, med en populationsstorlek på 1000-2000 exemplar. Habitatet utgörs av torrängar med låg vegetation, med inslag av enstaka samlingar av ek- och enbuskar. Torrängarna gränsar mot mer sammanhängande lövskog, vilken domineras av ek. Delar av torrängarna ligger på en strandvall från Littorinaperioden, vilken sluttar mot sydväst. Äldre fynd av lavdagsvärmaren från Beijershamnsområdet visar på en större utbredning några decennier tillbaka. Utbredningen har sedan dess minskat till den idag enda kvarvarande populationen. Flygbilder antyder att detta orsakats genom igenväxning av lämpliga habitat. Eftersom området bara betats sparsamt av häst, har igenväxningen främst orsakats av naturlig succession. Äggläggande honor och larver förekommer längs sydligt orienterade kantzoner, och på den sydvästsluttande strandvallen, där det finns rikligt med födoväxter för larvarna samt rikligt med ekförna. Detta tyder dels på ett starkt värmebehov, men också på ett fuktighetsbehov hos ägg och larver vilket kan uppnås i ekförnan. Larverna är polyfaga, och resultaten antyder att fördelar avseende överlevnad och tillväxt kan uppnås genom att olika födoväxter blandas under näringssöket. Larverna är även mer skyddade från predatorer och parasitioder när de befinner sig i ekförnan. De vuxna fjärilarna är stationära, och alla rörelser har skett inom habitatet. Medelförflyttningen hos hanar är 43 m, hos honor 9 m, och den längsta förflyttningen var 144 m. Fjärilarna visade en beteendemässig motvilja mot att flyga ut över angränsande avvikande miljöer; kraftigt betad ängsmark respektive tätare skog. Bevarandeåtgärderna bör inriktas på att hålla kvar habitatet i nuvarande utseende och hindra en igenväxning. Detta kan uppnås genom bete, eller manuella röjningar, med lämpliga intervall. Inga andra lämpliga habitat finns för närvarande i omgivningarna. Detta innebär att det kvarvarande habitatets gränser kan skötas så att risken för att fjärilar lämnar habitatet minimeras. En restaurering av områden där fjärilen förekom tidigare, vilka ligger inom spridningsavstånd för den kvarvarande populationen, bör endast övervägas om spridningskorridorer, där inga fjärilar lämnar korridoren till omgivningarna, kan skapas. Om restaureringsåtgärder planeras är den kvarvarande populationen väl lämpad för en expansion inom området, eftersom den genetiska statusen är god. (Less)
Abstract
The ecology of the moth Dysauxes ancilla was studied in the only Swedish breeding area at Beijershamn, situated on the Baltic island of Öland. The population is a northern outpost, separated from the species´ continous distribution area in middle- and southeast Europe. There is a general opinion that there has been a reduction of the species distribution during the last decades, but no studies have been performed. The species is red-listed as critically endangered. The results showed that the population is currently restricted to an area of 4 ha, with an estimated population size at 1000-2000 individuals. The habitat consists of dry meadows with a short grass community and stands of Quercus robur and Juniperus communis. Earlier findings of... (More)
The ecology of the moth Dysauxes ancilla was studied in the only Swedish breeding area at Beijershamn, situated on the Baltic island of Öland. The population is a northern outpost, separated from the species´ continous distribution area in middle- and southeast Europe. There is a general opinion that there has been a reduction of the species distribution during the last decades, but no studies have been performed. The species is red-listed as critically endangered. The results showed that the population is currently restricted to an area of 4 ha, with an estimated population size at 1000-2000 individuals. The habitat consists of dry meadows with a short grass community and stands of Quercus robur and Juniperus communis. Earlier findings of the moth in the area suggest a larger former distribution, which has now contracted to the single extant population because of overgrowth of all other suitable habitat areas. The area where D. ancilla occurred was never grazed regularly, except for a sparse grazing by horses. The decline was therefore mainly caused by natural successsion of the formerly more open landscape. Within the habitat ovipositing females and larvae are restricted to edge zones facing south and to an ancient shore line facing southwest. The dependence of these microhabitats are ascribed to two factors. First, being on the northern edge of the species´ distribution the need for warm microclimatic conditions is strong. Second, larvae occur where there are both a high abundance of food plants and well developed layers of Q. robur. The latter gives enough of humidity for the pre-imaginal stages, but larvae are also concealed from predators and parasitoids in this substrate. Further larvae are polyphagous, and my results suggest performance advantages from food-mixing and posssibly also from food-switching. Adults of D. ancilla are sedentary and all movements occurred within the breeding area. Mean distance between two successive captures was 43 m (males) and 9 m (females), and the longest single move was 144 m. Further the moths showed a behavioural reluctance to enter adjacent areas of other habitat types, e.g. heavily grazed meadows or dense vegetation. Conservation efforts should focus on managing the continuity of the current breeding area. This can be achieved by grazing, or by manually clearings, at suitable intervals. There are currently no other suitable breeding habitats in the surroundings. This means that the borders of the remaining breeding area should be managed to minimize losses of adult moths to the surrounding. A restoration of former breeding areas, suffiently close to the extant population to achieve connectivity, should only be considered if it is possible to create corridors in a way that prevent the moths from leaving a corridor to the surroundings. If a restoration plan is considered the extant population is a good basis for an expansion in the area since there is no genetic deterioration. (Less)
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author
opponent
  • Prof Mikkola, Kauri, University of Helsinki
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Animal ecology, Djurekologi, marc-recapture, population viability, fluctuating asymmetry, genetic status, larval feeding, movements, endangered species, conservation, outpost population, Lepidoptera, Dysauxes ancilla
pages
92 pages
publisher
Per-Eric Betzholtz, Dept of Biology and Environmental Sciences, University of Kalmar, SE-39182 Kalmar, Sweden.,
defense location
Högtidssalen, Helgonav. 3, Lund
defense date
2004-02-20 10:15
ISBN
91-85076-08-3
language
English
LU publication?
yes
id
f1b22d7a-4e1d-4a49-9c41-7dea27e16a0e (old id 466610)
date added to LUP
2007-09-04 12:53:07
date last changed
2016-09-19 08:45:08
@phdthesis{f1b22d7a-4e1d-4a49-9c41-7dea27e16a0e,
  abstract     = {The ecology of the moth Dysauxes ancilla was studied in the only Swedish breeding area at Beijershamn, situated on the Baltic island of Öland. The population is a northern outpost, separated from the species´ continous distribution area in middle- and southeast Europe. There is a general opinion that there has been a reduction of the species distribution during the last decades, but no studies have been performed. The species is red-listed as critically endangered. The results showed that the population is currently restricted to an area of 4 ha, with an estimated population size at 1000-2000 individuals. The habitat consists of dry meadows with a short grass community and stands of Quercus robur and Juniperus communis. Earlier findings of the moth in the area suggest a larger former distribution, which has now contracted to the single extant population because of overgrowth of all other suitable habitat areas. The area where D. ancilla occurred was never grazed regularly, except for a sparse grazing by horses. The decline was therefore mainly caused by natural successsion of the formerly more open landscape. Within the habitat ovipositing females and larvae are restricted to edge zones facing south and to an ancient shore line facing southwest. The dependence of these microhabitats are ascribed to two factors. First, being on the northern edge of the species´ distribution the need for warm microclimatic conditions is strong. Second, larvae occur where there are both a high abundance of food plants and well developed layers of Q. robur. The latter gives enough of humidity for the pre-imaginal stages, but larvae are also concealed from predators and parasitoids in this substrate. Further larvae are polyphagous, and my results suggest performance advantages from food-mixing and posssibly also from food-switching. Adults of D. ancilla are sedentary and all movements occurred within the breeding area. Mean distance between two successive captures was 43 m (males) and 9 m (females), and the longest single move was 144 m. Further the moths showed a behavioural reluctance to enter adjacent areas of other habitat types, e.g. heavily grazed meadows or dense vegetation. Conservation efforts should focus on managing the continuity of the current breeding area. This can be achieved by grazing, or by manually clearings, at suitable intervals. There are currently no other suitable breeding habitats in the surroundings. This means that the borders of the remaining breeding area should be managed to minimize losses of adult moths to the surrounding. A restoration of former breeding areas, suffiently close to the extant population to achieve connectivity, should only be considered if it is possible to create corridors in a way that prevent the moths from leaving a corridor to the surroundings. If a restoration plan is considered the extant population is a good basis for an expansion in the area since there is no genetic deterioration.},
  author       = {Betzholtz, Per-Eric},
  isbn         = {91-85076-08-3},
  keyword      = {Animal ecology,Djurekologi,marc-recapture,population viability,fluctuating asymmetry,genetic status,larval feeding,movements,endangered species,conservation,outpost population,Lepidoptera,Dysauxes ancilla},
  language     = {eng},
  pages        = {92},
  publisher    = {Per-Eric Betzholtz, Dept of Biology and Environmental Sciences, University of Kalmar, SE-39182 Kalmar, Sweden.,},
  school       = {Lund University},
  title        = {Ecology and conservation of the moth Dysauxes ancilla},
  year         = {2004},
}