title: Oviposition behaviour in the UK newt species, Triturus (Lissotriton) vulgaris, T.(L.) helveticus and T. cristatus effects of substrate and body size
Creators: name: M. Norris, Karen
Publisher: name: University of Liverpool Repository
Year: 2023

description: This thesis describes a series of studies designed to examine Triturus oviposition behaviour using a detailed approach. Specifically, two main lines of investigation were examined; the impact of egg-laying substrate material and of female body size. Triturus oviposition is a complex and unusual behaviour in which eggs are wrapped individually in the submerged leaves of aquatic plants. However, despite the apparently sequential and selective nature of this process, its likely significant cost to females and its implications for reproductive success, detailed behavioural information is lacking. A series of observational studies were set up to address this existing gap in knowledge. First, and fundamental to all subsequent comparisons, a detailed quantifiable ethogram of oviposition behaviour was developed. This revealed that deposition occurs as part of a repeated sequence of distinct behavioural elements common to all three UK newt species. From the ethogram, a series of oviposition measures were derived to facilitate all subsequent behavioural comparisons. In the first main investigative thread, the effects of substrate on oviposition were examined by comparing the behaviour of T. vulgaris females given a typical host substrate, Apium nodiflorum, with the behaviour of those given one of two more unusual substrates, Crassula helmsii or polythene strips (selected for their likely physical and chemical diversity). Key elements of the behavioural sequence, egg deposition rates and measures related to embryonic development were found to differ significantly between the substrates. On presenting the same materials to females of T. helveticus and T. cristatus, marked differences were also clearly identified. Moreover, whilst certain components clearly varied in response to different substrates, others appeared to follow a more fixed behaviour pattern. The impact of female body size on oviposition, the second main line of investigation, was initially considered by comparing the behaviour patterns generated by the three newt species in the substrate-focused experiments. These comparisons showed that there were inconsistencies in certain aspects of the process across all three species. Thus, whilst differences between overtly differently sized newts could possibly be accounted for by body size variation, it was not clear whether the subtle size disparity between T. vulgaris and T. helveticus explained the differences between these two species. A more explicit assessment of female body size examined the oviposition behaviour of the two small-bodied newts further. Correlation analyses revealed that body size impacted differently on certain elements of the process within each newt species. A more novel size-matched approach showed that small differences in body size, although these may have accounted for some of the variation, did not explain all of it. A possible underlying mechanism based on morphological differences between the species was proposed. The work in this thesis shows that both substrate material and female body size impact on the egg-laying process. It highlights the importance of collecting oviposition behaviour detail in a systematic way across a group of closely related species and clearly contributes to the existing Triturus oviposition literature. Moreover, the findings, aside from their intrinsic scientific value, have potentially wider-reaching implications for the ecology and phylogeny of these species, as well as possible conservation applications.