Abstract
Animals that reproduce in temporary aquatic systems expose their offspring to a heightened risk of desiccation, as they must race to complete development and escape before water levels recede. Adults must therefore synchronise reproduction with the changing availability of water, yet the conditions they experience to trigger such an event may not relate to those offspring face throughout development, potentially leading to clutch failure. The sandpaper frog (Lechriodus fletcheri) breeds in ephemeral pools that dry within days to weeks after rainfall has ceased. We examined whether spawning frequency and offspring survival differed across two consecutive breeding seasons based on (1) rainfall at the moment of oviposition and throughout offspring development, and (2) pool volume, given their combined effect on hydroperiod. Reproduction was triggered by rainfall, with more spawn laid during periods of greater rainfall and in larger pools. While pool size was a predictor of offspring survival, rainfall during oviposition was not. Rather, follow-up rain events were required to prevent pools drying prior to metamorphosis, with rainfall evenness during development the strongest predictor of reproductive success. High clutch failure rates recorded in both seasons suggest that adults do not have the capability to predict rainfall frequency post-oviposition. We thus conclude that unpredictable rainfall leading to premature desiccation of spawning sites is the primary source of pre-metamorphic mortality for this species. Understanding the influence of rainfall predictability on offspring survival could be critical in predicting the effects of altered hydroperiod regimes due to climate change for species that exploit temporary waters.
Highlights
Many animals reproduce in temporary aquatic habitats, such as ephemeral pools and streams that only become available in the landscape periodically and often for short periods of time (Heyer et al 1975; Wilbur 1980; Williams 2006; Colburn et al 2008; Furness et al 2015)
Offspring survival was modelled from the day offspring were oviposited in spawns (t0) to the day of failure up until 25 days, after which tadpoles were classified as surviving to metamorphosis and recorded as censored data as we considered escape from pools possible after metamorphosis had occurred
Offspring survival was low in both breeding seasons, with only a third of L. fletcheri spawns giving rise to offspring that reached metamorphosis even when considering the most rapid rate of tadpole development, with total clutch mortality occurring in 100% of spawns laid in several rain events
Summary
Many animals reproduce in temporary aquatic habitats, such as ephemeral pools and streams that only become available in the landscape periodically and often for short periods of time (Heyer et al 1975; Wilbur 1980; Williams 2006; Colburn et al 2008; Furness et al 2015). This can confer an offspring survival advantage by reducing exposure to predators. Conservation Biology Research Group, School of Environmental and Life Sciences, University of Newcastle, University Drive, Callaghan, NSW 2308, Australia The conditions that are triggers for reproduction may not necessarily correlate with the conditions offspring are subsequently exposed to throughout development
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