The effects of predation risk and habitat history on butterfly communities
Date
2011-11-09
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Abstract
Ökoloogia üks keskseid ülesandeid on kirjeldada ja seletada liigirikkuse varieeruvuse mustreid. Käesolevas doktoritöös uuriti kahe, sageli raskesti hinnatava elupaigaparameetri – kiskluse ning elupaikade hävimise määra – mõju päevaliblikate populatsioonidele ja kooslustele. Vaatamata sellele, et nende faktorite mõju peetakse liigirikkuse mustrite kujunemisel oluliseks, on vähemasti putukate kohta empiirilist infot looduslikes kooslustes minimaalselt. Töös keskenduti päevaliblikate kooslustele Lääne-Eesti loopealsetel. Konkreetsemalt küsiti, kuivõrd mõjutavad kiilid kui kiskjad päevaliblikate liigirikkuse mustreid ning kuivõrd päevaliblikate liigirikkuse tänapäevased mustrid on mõjutatud elupaiga ajaloolisest karakteristikutest. Tulemused näitavad, et nii kisklusrisk kui ka elupaiga ajaloolised parameetrid seletavad olulise osa päevaliblikate koosluste liigirikkuse varieerumisest. Kiilide ruumiliselt ja sesoonselt varieeruv kisklussurve on piisav, et mõjutada mitte ainult päevaliblikate arvukust, vaid ka liigirikkust ning liigilist koosseisu. Nimelt puudusid kõrgema kiilide arvukusega loopealsetelt suurema tõenäosusega need päevaliblikaliigid, kelle lennuaeg kattub kiilide arvukuse tippajaga ning liigirikkus kiilirohketel aladel oli madalam. Seega on kisklus oluline faktor, mida arvestada ka praktilises looduskaitses. Nii ajalooline kui tänapäeva elupaiga pindala seletas olulise osa kitsaste elupaigaspetsialistide liigirikkuse varieerumisest. Samal ajal ei sõltunud generalistde liigirikkus ei tänapäeva ega ajaloolise elupaiga pindalast, mis viitab nende kahe rühma erinevale tundlikkusele elupaiga pindala muutumise suhtes. Käesoleva töö tulemused näitavad, et ainult tänapäevase elupaiga parameetrite teadmisest ei pruugi piisata, hindamaks liigi seisundit dünaamilises tugeva inimmõjuga maastikus.
Revealing major biotic and abiotic gradients along which species are spatially distributed is one of the major goals in ecology. In this thesis butterfly community structure along the gradients of dragonfly predation risk and habitat history was examined. In spite of the growing awareness of the importance of predation risk and habitat past characteristics in different ecosystems, community-level responses along these gradients have rarely been addressed in empirical studies focusing on insects. Current thesis focused on these issues in butterfly communities in seminatural calcareous grasslands (alvars) in Western Estonia. The results show that the variation in predation risk and past habitat characteristics can explain a significant amount of variation in butterfly species composition and richness. Butterfly communities at predator rich sites were biased towards a greater proportion of species flying during off peak dragonfly abundance, and butterfly species richness in dragonfly-rich habitat patches was lower than in dragonfly-poor patches. The gradient of predation risk could thus be an important factor to consider in practical conservation work as well. Both historical and current habitat area explained a significant amount of variation in strict habitat specialist butterflies, whereas species richness of other grassland butterflies was associated neither with past nor current habitat area. These patterns imply differential sensitivity of these two groups to habitat changes. The results of the thesis show that relying on just current habitat characteristics may not be sufficient to assess the status of species diversity in dynamic, human-affected landscapes.
Revealing major biotic and abiotic gradients along which species are spatially distributed is one of the major goals in ecology. In this thesis butterfly community structure along the gradients of dragonfly predation risk and habitat history was examined. In spite of the growing awareness of the importance of predation risk and habitat past characteristics in different ecosystems, community-level responses along these gradients have rarely been addressed in empirical studies focusing on insects. Current thesis focused on these issues in butterfly communities in seminatural calcareous grasslands (alvars) in Western Estonia. The results show that the variation in predation risk and past habitat characteristics can explain a significant amount of variation in butterfly species composition and richness. Butterfly communities at predator rich sites were biased towards a greater proportion of species flying during off peak dragonfly abundance, and butterfly species richness in dragonfly-rich habitat patches was lower than in dragonfly-poor patches. The gradient of predation risk could thus be an important factor to consider in practical conservation work as well. Both historical and current habitat area explained a significant amount of variation in strict habitat specialist butterflies, whereas species richness of other grassland butterflies was associated neither with past nor current habitat area. These patterns imply differential sensitivity of these two groups to habitat changes. The results of the thesis show that relying on just current habitat characteristics may not be sufficient to assess the status of species diversity in dynamic, human-affected landscapes.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone.
Keywords
päevaliblikad, liigirohkus, kiililised, röövloomad, elupaigad, diurnal butterflies, species richness, Odonata, predatory animals, habitats