Larval deposition behaviour and maternal investment of females reflect differential habitat adaptation in a genetically diverging salamander population

Illuminating the ability of individuals to react to different selective forces caused by environmental differences is crucial to understand population divergence and speciation in the context of habitat adaptation. In a common environment experiment performed under standardised laboratory conditions, we examined whether female fire salamanders (Salamandra salamandra) originating from a recently adaptively diverged population displayed behavioural phenotype differences related to larval deposition behaviour. Females of this species typically deposit their larvae in small first-order streams; however, in our study population, females also use temporary ponds. These two habitat types display major ecological differences that strongly influence larval growth and survival. We observed that females differed in larval deposition behaviour and maternal investment. Pond-type females extended larval deposition over an increased time period and tended to exhibit more deposition events compared with stream-type females. Over successive deposition events, the body condition of larvae deposited by stream-type females decreased faster than that of larvae deposited by pond-type females. These differences in larval deposition behaviour may represent a bet-hedging strategy, given that ponds are more constrained in terms of desiccation and food availability than streams. The lengthened deposition period enabled pond-type females to deposit larger larvae towards the end of the deposition period, compared with stream-type females. Although the studied population only diverged recently, we observed significant behavioural differences between differentially adapted females, demonstrating the importance of behavioural differences in habitat adaptation in the context of speciation processes.