Deposition of larvae by Salamandra salamandra: Managing risks of desiccation and competition

Salamandra salamandra is a locally endangered Urodela species that uses temporary pools in northern Israel as habitats for its larval stage. Early larviposition in temporary pools results in larval competitive superiority and reduced vulnerability to cannibalism with later cohorts, but also in increased risk of pool desiccation between sporadic rains at the beginning of the rainy season. A state-dependent model was constructed based on stochastic dynamic programming considering physiological state (offspring complement), hydrologic environment and larval growth and survival. According to this model, females are predicted to spread their young spatially and temporally to manage competition and desiccation risks. Additionally females are predicted to adjust the number of young deposited in each pool according to quality cues perceived from it. This study assessed both temporal and spatial distribution of larvae in the field by surveying a breeding site containing 27 pools of different sizes and hydroperiods. Both removal and mark-recapture methods were used to estimate larval abundance and new larviposition events following rain events for each pool. Molecular DNA analysis is being used for estimation of spatial and temporal distribution of siblings. Our field observations support the model predictions.  Both spatial and temporal distribution of larvae was detected in the site. Larger pools with longer hydroperiods had more larviposition, while smaller pools had few larvae or none. Further genetic analysis of siblings, as well as measurements of survival to, size at, and time to metamorphosis in different pools, currently being conducted, will allow more specific assessment of larviposition distribution patterns in relation to habitat quality.