Intrinsic and extrinsic drivers of spatio-temporal dynamics in Lepidoptera, and their implications for forecasting for better management strategies.

Gomez, Irene and Wilson, Kenneth and Bush, Alex (2025) Intrinsic and extrinsic drivers of spatio-temporal dynamics in Lepidoptera, and their implications for forecasting for better management strategies. PhD thesis, Lancaster University.

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Abstract

Mobility is inherent to all organisms and serves as a mechanism for finding resources, mates, or better environmental conditions. Winged insects, in particular Lepidoptera, tend to have higher mobility than other insects partly due to their morphology, and their diversity. However, there are many factors (intraspecific, interspecific, and abiotic) that can affect their ability to disperse or migrate and determine their spatio-temporal movement patterns. Identifying these factors and patterns can help improve prediction and forecasting, especially because climate change, habitat fragmentation and anthropogenic dispersal can alter the distribution and dispersal of these species. In the second chapter of this thesis, intraspecific factors of highly mobile lepidoptera are explored, and findings confirm there are morphological differences between not only sedentary and highly mobile species, but also between species with different mobility behaviours like dispersal and migration, all linked to phylogeny. In chapters 3, 4, and 5, the African armyworm (AAW), a highly mobile maize pest, is used as a case study to explore how different abiotic factors influence its mobility and determine its spatio-temporal dynamics in Tanzania, in order to refine outbreak prediction and management strategies. Findings confirm a non-linear relationship between AAW migratory behaviour, and rainfall and wind, and also distinguish differences during the seasonal patterns (Chapter 3). Long-term trends indicate that the decline in AAW outbreaks in recent decades is related to periods of droughts and a decline of yearly precipitation in Tanzania, which could potentially shift the geographic range of the species (Chapter 4). Finally, in Chapter 5, local (Kenya and Tanzania) and global potential environmental suitability models are projected, suggesting areas where the AAW could persist if ever they were introduced there. Additionally, I present three potential future environmental suitability scenarios that are projected for Kenya and Tanzania, which could serve as models for setting preventive measures in areas of concern.