Phylogenetic comparative studies of body size in insects and arachnids: from predictions to applications
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Ajakirja pealkiri
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Kehasuurus on üks olulisemaid loomade tunnuseid. Kehasuurus määrab, kuidas loom saab liikuda ja millised on ta vastasmõjud keskkonnaga, sageli sõltub kehasuurusest ka paljunemisedukus. Ometi on paljude lülijalgsete puhul kehasuurust raske vahetult mõõta. Üks võimalus lihtsustada kehasuuruse määramist on kasutada allomeetrilisi võrrandeid, mis seovad kehasuurust hõlpsasti vaadeldavate kehaosade mõõtmetega. Sellise lähenemise abil saab hinnata kehasuurust ka vanade, halvasti või ainult osaliselt säilinud isendite ning isegi fossiilide puhul. Oma doktoritöös arendasin allomeetrilisi mudeleid kehasuuruse prognoosimiseks vaksiklaste (Geometridae) ja skorpionide sugukonna Buthidae jaoks. Fülogeneesipõhiseid meetodeid paljusid liike hõlmavatel andmestikel rakendades tuvastasin, millised lihtsasti määratavad mõõdud prognoosivad kehasuurust kõige paremini. Järgnevalt kasutasin vastavaid võrrandeid ökoloogiliste ja evolutsiooniliste küsimuste uurimiseks. Vaksiklastel oli tiibade siruulatus parim üksik kuivmassi ennustaja, kuid mudelid olid siiski täpsemad, kui neisse kaasati ka tagakeha laius. Kehasuuruse prognoose võrdlev-fülogeneetilistesse analüüsidesse kaasates selgus, et suuremad vaksikuliigid kalduvad talvituma röövikuna ja nende röövikutel on keskmisest laiem toitumisspekter. Skorpionide puhul prognoosis “saba” viienda lüli pikkus kõige täpsemini kogu keha pikkust, samas kui telsoni (lüli, mis kannab astelt) pikkus oli parim seljakilbi pikkuse ennustaja. Mudelid toimisid sõltumata soost ja neid saab rakendada ka väljaspool uuritud sugukonda. Samuti selgus, et skorpionide seas on emasloomad üldiselt suuremad, kuid isastel on sageli suhteliselt suuremad sigimisega seotud struktuurid. Doktoritöö näitab, et fülogeneesile tuginevad allomeetrilised mudelid on igati sobivad vahendid selgrootute kehasuuruse hindamiseks. Need avavad ukse uurimaks ökoloogilisi ja evolutsioonilisi küsimusi rühmades, kus kehasuuruse otsene mõõtmine on sageli ebapraktiline või suisa võimatu.
Body size is one of the most important traits in animals, influencing how they move, reproduce, and interact with their environment. Yet, for many arthropods like insects and arachnids, body size can be difficult to measure directly, especially when dealing with hundreds of individuals, or when the specimens are damaged. One way to facilitate the measuring is to use allometry, which defines the mathematical relationships that link body size to simpler measurements of body parts, such as wingspan in a flying insect or the size of a body segment in an arachnid. With this approach, scientists can reliably estimate body size from specimens that are old, poorly preserved or incomplete, and even from fossils. In my doctoral research, I developed and tested allometric models to predict body size in two diverse groups: geometrid moths and buthid scorpions. By combining phylogenetic methods with large datasets, I identified which measurements best predict body size and then applied these predictions to study ecological and evolutionary aspects in each group. For moths, maximum wingspan was the best predictor of dry body mass, and models were more accurate when combined with measurements of abdomen width. Based on body size predictions, I found that larger moths generally overwinter as larvae and have broader diets. In scorpions, the length of the fifth “tail” segment predicted total length most effectively, while telson length (the segment that carries the sting) best predicted carapace length. These models worked across sexes and even beyond the studied family. I also found that in Neotropical buthids, females tend to be larger, but males often have proportionally bigger structures linked to reproduction. This work shows that phylogenetically informed allometric models are powerful tools for estimating body size in invertebrates. They open the door to studying ecological and evolutionary aspects in groups where direct measurements are often impractical or even impossible.
Body size is one of the most important traits in animals, influencing how they move, reproduce, and interact with their environment. Yet, for many arthropods like insects and arachnids, body size can be difficult to measure directly, especially when dealing with hundreds of individuals, or when the specimens are damaged. One way to facilitate the measuring is to use allometry, which defines the mathematical relationships that link body size to simpler measurements of body parts, such as wingspan in a flying insect or the size of a body segment in an arachnid. With this approach, scientists can reliably estimate body size from specimens that are old, poorly preserved or incomplete, and even from fossils. In my doctoral research, I developed and tested allometric models to predict body size in two diverse groups: geometrid moths and buthid scorpions. By combining phylogenetic methods with large datasets, I identified which measurements best predict body size and then applied these predictions to study ecological and evolutionary aspects in each group. For moths, maximum wingspan was the best predictor of dry body mass, and models were more accurate when combined with measurements of abdomen width. Based on body size predictions, I found that larger moths generally overwinter as larvae and have broader diets. In scorpions, the length of the fifth “tail” segment predicted total length most effectively, while telson length (the segment that carries the sting) best predicted carapace length. These models worked across sexes and even beyond the studied family. I also found that in Neotropical buthids, females tend to be larger, but males often have proportionally bigger structures linked to reproduction. This work shows that phylogenetically informed allometric models are powerful tools for estimating body size in invertebrates. They open the door to studying ecological and evolutionary aspects in groups where direct measurements are often impractical or even impossible.
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