Phenology and growth plasticity in a short-lived chameleon under climatic variation

Understanding species' responses to climate change is crucial for the mitigation of its effects. Few studies, however, have examined how climate change impacts timing in reptile life cycles, or how it may interact with other life history traits. Here, we explore associations between climatic variation, reptile phenology, and juvenile growth. We used the chameleon species Furcifer labordi as a biological model given its unusual annual life history: embryonic diapause during austral winter is followed by synchronous hatching and an extremely short adult lifespan. We sampled chameleons (n = 674) and climate data across three field seasons between 2013-2018 in Kirindy Forest (CNFEREF), western Madagascar. Evidence of temperature and precipitation shifts have already been reported for this region. We show climate-dependent variation in the timing of hatching: it always occurred after the first rains and its onset varied by up to 32 days among years (equivalent to 12-17% of the total length of non-embryonic lifespan). Moreover, delayed rainy season onset resulted in a shortening of the period between the first rains and first hatching. Significant differences in hatching time and temperature also resulted in variation in juvenile growth, specifically faster post-hatching growth in the late-hatching cohort. Therefore, climatic variation was associated with phenological and juvenile growth plasticity in the life cycle of F. labordi. Implications for conservation are worrying, as complete populations could be lost if a single cohort of this annual species cannot effectively respond to increasing climatic fluctuation.