Comparative ecology of geometrid moths: in search of contrasts between a temperate and a tropical forest
Date
2019-09-19
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Abstract
Putukate mitmekesisus on erakordselt suur, kuid me teame nende kohta vähe. Töö peamiseks eesmärgiks oli uurida ja võrrelda parasvöötme (Eesti) ja troopika (Uganda) metsaökosüsteemist pärit vaksiklaste (Geometridae) elukäike. Ööliblikate hulka kuuluvaid vaksiklasi on umbes 24000 kirjeldatud liiki, nende ökoloogiat ja kujunemist tuntakse pigem vähe, eriti troopikas. Andmeid koguti ligi 250 liigi kohta ning uuritud liikidele koostati originaalandmetel põhinev fülogeneesipuu. Andmeanalüüsis kasutati liikidevahelist sugulust arvesse võtvaid meetodeid.
Troopikas uuriti 15 sagedase puuliigi sobivust vastkoorunud röövikute toiduks. Sarnaselt parasvöötmega leidus ka troopikas vaksikuliike, kes toitusid samaaegselt mitmest sugukonnast pärit taimeliikidest. Parasvöötme vaksikuliikide põhjal näidati, et munemiseelne ooteaeg vangistuses on pikem nendel liikidel, kelle järglased toituvad väiksemast arvust taimedest. Kuna troopiliste liikide toidutaimed ei ole enamasti teada, siis kasutati munemiseelset ooteaega, et uurida, kas ja millisel määral erineb kasutatav toidutaimede arv parasvöötmes ja troopikas. Leiti, et ooteajad on mõlemas piirkonnas sarnased. Tulemused lubavad arvata, toiduks kasutatav taimede arv on mõlemas piirkonnas sarnane.
Leiti, et troopilised liigid on raskemad. Massierinevused tulenevad rindmikute suurematest massidest, mis omakorda viitab paremale lennuvõimele. Lisaks leiti veel, troopilised liigid munevad väiksemaid mune kui parasvöötme liigid, mistõttu on ilmselt ka vastkoorunud röövikud troopikas väiksemad.
Parasvöötme ja troopika vaksikuliikide valmikute keskmised eluead on sarnased. Tulemused näitasid, et suuremad liigid elavad kauem kui väiksemad liigid. Troopikas on palju valmikutoitu (puuviljad ja õienektar), kuid tulusigimine, st paljunemisstrateegia, mille puhul on paljunemisedukus sõltuv valmikuelu jooksul hangitud ressurssidest, ei olnud troopikas rohkem levinud kui parasvöötmes.
Töö tulemuste põhjal võib järeldada, et toidutaimekasutus, eluiga ja paljunemisstrateegia on troopika ja parasvöötme uuritud piirkonna vaksiklastel pigem sarnased. Maailm, mida liigid kogevad, ja tegurid, mis kujundavad nende elukäiku, ei pruugi parasvöötmes ja troopikas olla nii erinevad, nagu enamasti arvatakse.
Insects are extremely diverse and we still know relatively little about them. The major aim of this thesis was to compare lives of moth species from the family Geometridae from a temperate and a tropical forest ecosystem. Worldwide there are approximately 24 000 described geometrid species, but we do not know much about the tropical species. For about 250 temperate and tropical region geometrid species, data on host-plant specificity, longevity and breeding strategy were collected. A phylogeny was derived for these species and the collected data compared in phylogenetically informed analyses. The suitability of 15 common tree species as food for freshly hatched caterpillars was tested in host-plant acceptance trials and the larval diet breadth of tropical and temperate species was compared. There were broadly polyphagous species in both regions. For temperate species it was shown that oviposition latency (i.e. pre-oviposition waiting time of a female) in captivity was longer for those geometrid species that have a narrower larval diet breadth. This result provided the possibility to use oviposition latency as an indirect measure of host specificity for the tropical region, where the host plants are not known. When oviposition latency was compared between temperate and tropical regions the waiting times were found to be similar. These results suggest that host-plant specificity is similar in both regions. Tropical species were found to be heavier than temperate ones; the difference is probably caused by the large wings and flying muscles of tropical species, which increase mobility in dense and diverse tropical vegetation. Compared to temperate females, tropical females lay smaller eggs. Therefore, it is also possible, that freshly hatched larvae are smaller in the tropical region. Adult lifespans of wild-caught individuals were found to be similar for both regions. Larger species were shown to have longer lifespans. Opposite to the predictions, the stable supply of adult food in the tropics (fruit and nectar) did not increase adult lifespans. Neither was income breeding strategy (i.e. breeding strategy depending on adult-derived resources) found to be more prevalent in the tropics than in temperate habitats. The results of this thesis suggest that host-plant specificity, longevity and breeding strategy are similar for the studied temperate and tropical moths. Quite opposite to expectations, the world the moths experience and the factors that shape their life histories may not be so different for the tropical and temperate zones after all.
Insects are extremely diverse and we still know relatively little about them. The major aim of this thesis was to compare lives of moth species from the family Geometridae from a temperate and a tropical forest ecosystem. Worldwide there are approximately 24 000 described geometrid species, but we do not know much about the tropical species. For about 250 temperate and tropical region geometrid species, data on host-plant specificity, longevity and breeding strategy were collected. A phylogeny was derived for these species and the collected data compared in phylogenetically informed analyses. The suitability of 15 common tree species as food for freshly hatched caterpillars was tested in host-plant acceptance trials and the larval diet breadth of tropical and temperate species was compared. There were broadly polyphagous species in both regions. For temperate species it was shown that oviposition latency (i.e. pre-oviposition waiting time of a female) in captivity was longer for those geometrid species that have a narrower larval diet breadth. This result provided the possibility to use oviposition latency as an indirect measure of host specificity for the tropical region, where the host plants are not known. When oviposition latency was compared between temperate and tropical regions the waiting times were found to be similar. These results suggest that host-plant specificity is similar in both regions. Tropical species were found to be heavier than temperate ones; the difference is probably caused by the large wings and flying muscles of tropical species, which increase mobility in dense and diverse tropical vegetation. Compared to temperate females, tropical females lay smaller eggs. Therefore, it is also possible, that freshly hatched larvae are smaller in the tropical region. Adult lifespans of wild-caught individuals were found to be similar for both regions. Larger species were shown to have longer lifespans. Opposite to the predictions, the stable supply of adult food in the tropics (fruit and nectar) did not increase adult lifespans. Neither was income breeding strategy (i.e. breeding strategy depending on adult-derived resources) found to be more prevalent in the tropics than in temperate habitats. The results of this thesis suggest that host-plant specificity, longevity and breeding strategy are similar for the studied temperate and tropical moths. Quite opposite to expectations, the world the moths experience and the factors that shape their life histories may not be so different for the tropical and temperate zones after all.
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Väitekirja elektrooniline versioon ei sisalda publikatsioone
Keywords
vaksiklased, loomaökoloogia, metsaökosüsteemid, parasvöötmed, troopika, võrdlevuuringud