Morphological and Behavioural Variation in Ants: Comparing Species, Castes and Individuals

• Main Author: Teixeira, Andreia Filipa Eusébio Vincent
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2015
• Subjects: Biochemistry; DNA methylation; Humidity; Insects; Morphology; Normal distribution; Nutrition; Thorax
• ISBN: 9798384183945

Environment plays a fundamental role in living organisms’ adaptation and selection. Developmental plasticity allows individuals to sense the surrounding environment and produce different phenotypes in response to biotic and abiotic cues. Individuals are exposed to these cues during larval phase and transduce it to shape and size adaptations in the adult. Social insects are a good (non-)model organism to study developmental plasticity since they present dramatic castes differences. The reason behind ants’ ecological success is division of labour and each colony is divided in groups according to specific tasks, like reproduction and colony defence. Morphology appeared early as a caste defining factor, but soon age and physiology were included in the list. Extreme dimorphism between queens and workers demonstrated that morphology and behaviour should not be considered independent traits and species whose worker caste is divided in sub-castes highlighted that more attention should be paid to within caste variation and specializations. Morphology is determined by growth during development and thus regulated by juvenile hormone and ecdysone, which together can reprogram metamorphosis timing. In this work we compare species, castes and individuals morphology and can have an overview of how much variation is found between and within groups. Within worker castes we performed a detailed analysis on morphology and behaviour and found some task division signatures, even in monomorphic castes. Finally we simulated environmental cues by manipulating endogenous hormonal levels and to know if a monomorphic species is able to produce intermediate phenotypes when exposed to the same conditions as dimorphic species. Our morphometric analysis demonstrated that we could find more differences between than within castes, and also allowed us to suggest the existence of more caste-related traits in contrast with other more species-related. Intra-caste analysis suggested the existence of task-specific behavioural groups within monomorphic colonies. Hormonal manipulation results were affected by the nature of compounds used and also by the absence of a specific dosage-response curve for species used. However we could also address some colony specificity in the response to treatments, and differential sensibility to these.