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Butterfly Diversity and Dispersal in Fragmented Grasslands

Öckinger, Erik LU (2006)
Abstract (Swedish)
Popular Abstract in Swedish

Under de senaste decennierna har utbredningen och förekomsten i av många arter av fåglar, växter och insekter knutna till jordbrukslandskap på olika håll i Europa minskat på grund av jordbrukets rationalisering och intensifiering. För att motverka dessa negativa trender måste man ha kännedom om den relativa betydelsen av lokala och regionala ekologiska processer för populationers fortlevnad och mönster i artrikedom.



Jag har studerat effekten av landskapets sammansättning på den lokala artrikedomen och individtätheten av dagfjärilar, och i ett fal också av humlor, Jag har också studerat effekten av landskapets sammansättning på dagfjärilars spridning och ... (More)
Popular Abstract in Swedish

Under de senaste decennierna har utbredningen och förekomsten i av många arter av fåglar, växter och insekter knutna till jordbrukslandskap på olika håll i Europa minskat på grund av jordbrukets rationalisering och intensifiering. För att motverka dessa negativa trender måste man ha kännedom om den relativa betydelsen av lokala och regionala ekologiska processer för populationers fortlevnad och mönster i artrikedom.



Jag har studerat effekten av landskapets sammansättning på den lokala artrikedomen och individtätheten av dagfjärilar, och i ett fal också av humlor, Jag har också studerat effekten av landskapets sammansättning på dagfjärilars spridning och rörelsemönster.



I svhandlingens första studie visade jag att artrikedomen av dagfjärilar i Sydsverige hade minskat signifikant under de senaste 20 åren, och att dessa förändringar kunde relateras till lokala habitatförändringar snarare än till landskapsförändringar. En stor omsättning av arter även på lokaler där antalet arter var konstant indikerade dock att metapopulationsprocesser kan vara betydelsefulla i detta sammanhang.



I den andra studien jämförde jag artrikedom av dagfjärilar i likartade naturbetesmarker, men som var belägna i kontrasterande landskap. En hög andel naturbetesmark på landskapsnivån ledde till högre artrikedom i den enskilda betesmarken. I avhandlingens tredje studie fann jag att betydelsen av landskapets sammansättning var beroende av arternas rörlighet, där effekten var störst på ?halvrörliga? arter.



Genom att undersöka artrikedom och populationstätheter av dagfjärilar och humlor i jordbrukslandskapet på olika avstånd från närmaste naturbetesmark, och genom att använda fångst-återfångstteknik för att undersöka fjärilars rörelsemönster, fann jag att naturbetesmarker kan fungera som populationskällor i intensivt brukade jordbrukslandskap. Detta innebär att artrikedomen och populationstätheterna är högre i landskap där det finns naturbetesmarker.



Så kallade ekologiska korridorer har föreslagits som ett sätt att öka spridningen mellan lokal populationer, och därmed öka populationernas överlevnadschanser. Jag fann inget stöd för detta när jag studerade spridningsmönster hos tre arter av dagfjärilar som är knutna till gräsmarker. Däremot tydde resultaten på att fjärilar kan ?diffundera? längs korridorer över kortare avstånd.



Mina resultat visar tydligt att populationsprocesser som äger rum på en landskapsskala är viktiga för populationers livskraft och för artrikedom. De visar också att de är olika landskapsekologiska processer som kan ha betydelse, vilket innebär att både noggranna studier och klart formulerade mål behövs för att kunna föreslå åtgärder för att hindra minskningen av den biologiska mångfalden. (Less)
Abstract
During the last decades, the distribution and abundance of many European species of birds, plants and insects in agricultural landscapes have declined due to agricultural intensification. To be able to mitigate these declines, it is essential to know the relative importance on local and regional ecological processes on population persistence and patterns of species richness.



I have studied the effect of landscape composition on local species richness, abundance and dispersal patterns of butterflies, and in one of the papers also on bumblebees.



In the first study, I showed that the species richness of butterflies in southern Sweden had declined significantly during the last decades, and that the... (More)
During the last decades, the distribution and abundance of many European species of birds, plants and insects in agricultural landscapes have declined due to agricultural intensification. To be able to mitigate these declines, it is essential to know the relative importance on local and regional ecological processes on population persistence and patterns of species richness.



I have studied the effect of landscape composition on local species richness, abundance and dispersal patterns of butterflies, and in one of the papers also on bumblebees.



In the first study, I showed that the species richness of butterflies in southern Sweden had declined significantly during the last decades, and that the observed declines could be related to changes in local habitat quality rather that to landscape composition. However, a larger turnover of species also in sites where species richness was constant indicated that metapopulation dynamics might be important.



In the second study, I studied butterfly species richness in similar grasslands situated in contrasting landscapes. A high proportion of semi-natural grassland at the landscape scale increased species richness at the local scale. In the third study, I found that the effect of landscape composition on species richness was dependent on the mobility of the species, with intermediately mobile species most strongly affected.



By studying species richness and population densities at different distances from semi-natural grasslands and using mark-recapture techniques to study butterfly movements, I found that in intensively farmed agricultural landscapes, semi-natural grassland can act as population sources, contributing to higher species richness and population densities in their surroundings.



So called ecological corridors have been suggested to increase dispersal between local populations. I found no evidence of this when studying the dispersal of three grassland butterflies, but there was some evidence of a diffusion of butterflies over shorter distances along the corridors.



In conclusion, my results clearly show that population processes at the landscape scale are important for population persistence and species richness. However, they also show that different landscape ecological processes may be important, which implies that both thorough studies and explicit objectives are needed in order to be able to suggest measures to counteract biodiversity loss. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Roland, Jens, University of Alberta, Edmonton, Canada
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Naturvetenskap, Djurekologi, Animal ecology, Ekologi, Ecology, Lepidoptera, Landscape ecology, Insects, Species richness, Fragmentation, Mobility, Natural science, Source-sink dynamics, Metapopulations
pages
138 pages
publisher
Department of Ecology, Lund University
defense location
Ecology Building, Sölvegatan 37, Lund
defense date
2006-11-17 09:00
ISBN
91-7105-242-9
language
English
LU publication?
yes
id
8f314609-dfff-4bb9-8b32-92890c36d4f3 (old id 547454)
date added to LUP
2007-09-06 10:56:04
date last changed
2016-09-19 08:45:14
@misc{8f314609-dfff-4bb9-8b32-92890c36d4f3,
  abstract     = {During the last decades, the distribution and abundance of many European species of birds, plants and insects in agricultural landscapes have declined due to agricultural intensification. To be able to mitigate these declines, it is essential to know the relative importance on local and regional ecological processes on population persistence and patterns of species richness.<br/><br>
<br/><br>
I have studied the effect of landscape composition on local species richness, abundance and dispersal patterns of butterflies, and in one of the papers also on bumblebees.<br/><br>
<br/><br>
In the first study, I showed that the species richness of butterflies in southern Sweden had declined significantly during the last decades, and that the observed declines could be related to changes in local habitat quality rather that to landscape composition. However, a larger turnover of species also in sites where species richness was constant indicated that metapopulation dynamics might be important.<br/><br>
<br/><br>
In the second study, I studied butterfly species richness in similar grasslands situated in contrasting landscapes. A high proportion of semi-natural grassland at the landscape scale increased species richness at the local scale. In the third study, I found that the effect of landscape composition on species richness was dependent on the mobility of the species, with intermediately mobile species most strongly affected.<br/><br>
<br/><br>
By studying species richness and population densities at different distances from semi-natural grasslands and using mark-recapture techniques to study butterfly movements, I found that in intensively farmed agricultural landscapes, semi-natural grassland can act as population sources, contributing to higher species richness and population densities in their surroundings.<br/><br>
<br/><br>
So called ecological corridors have been suggested to increase dispersal between local populations. I found no evidence of this when studying the dispersal of three grassland butterflies, but there was some evidence of a diffusion of butterflies over shorter distances along the corridors.<br/><br>
<br/><br>
In conclusion, my results clearly show that population processes at the landscape scale are important for population persistence and species richness. However, they also show that different landscape ecological processes may be important, which implies that both thorough studies and explicit objectives are needed in order to be able to suggest measures to counteract biodiversity loss.},
  author       = {Öckinger, Erik},
  isbn         = {91-7105-242-9},
  keyword      = {Naturvetenskap,Djurekologi,Animal ecology,Ekologi,Ecology,Lepidoptera,Landscape ecology,Insects,Species richness,Fragmentation,Mobility,Natural science,Source-sink dynamics,Metapopulations},
  language     = {eng},
  pages        = {138},
  publisher    = {ARRAY(0xa171978)},
  title        = {Butterfly Diversity and Dispersal in Fragmented Grasslands},
  year         = {2006},
}