Hatching plasticity in a Southeast Asian tree frog mitigates submergence‐induced mortality

Abstract

Environmentally cued hatching has been well‐documented in amphibians in response to a wide range of abiotic and biotic factors. The hatching of terrestrial amphibian eggs in response to flooding may be basal within the group, but amphibian lineages in tropical Asia and sub‐Saharan Africa have not received as much attention as their Neotropical counterparts. We investigated submergence‐induced hatching in Feihyla hansenae, a Rhacophorid tree frog with terrestrial eggs. We quantified natural rates of clutch submergence at our study site in Thailand. Using submergence experiments, we found that embryos are capable of hatching early to escape flooding, and that failure to hatch results in mortality. Among the embryos that were able to hatch early, only the earliest, youngest hatchlings experienced a trade‐off in body size that persisted for 6 days, while later, older hatchlings were not significantly smaller than spontaneous hatchlings under control conditions. By incorporating our natural and experimental data into Monte Carlo methods to simulate and compare survival probabilities with and without hatching plasticity, we found an overall 3.1% increase in submergence survival due to hatching plasticity. Our findings support the idea that flooding‐induced hatching is widespread across amphibians with terrestrial eggs and highlight the importance of researching understudied tropical regions. As climate change is projected to affect rainfall patterns, the ability of embryos to escape abiotic egg‐stage threats may be an indicator of species' ability to flexibly navigate a changing environment.

Hatching plasticity is associated with a more advanced stage at hatching in an Ambystoma with terrestrial eggs

“…Across diverse species, physical stimulation (DiMichele & Taylor, 1981 ; Griem & Martin, 2000 ; Oyarzun & Strathmann, 2011 ; Warkentin, 2005 ), chemical signals such as predator and conspecific cues (Miner et al., 2010 ; Poo & Bickford, 2014 ; Smith & Fortune, 2009 ; Warkentin, 1995 ), and salinity (Allen et al., 2017 ; Haramura, 2016 ) can trigger early hatching. Embryos that can initiate hatching in response to environmental cues may face tradeoffs; while early hatching allows embryos to escape predation, hatchlings may be smaller or less developed (Delia et al., 2019 ; Poo et al., 2023 ), which can be associated with greater larval predation risk and lower larval survival (Delia et al., 2019 ; Gomez‐Mestra et al., 2008 ; McCoy et al., 2011 ; but see Vonesh & Bolker, 2005 ).…”

“…However, they also risk desiccation and predation by terrestrial predators (Delia et al., 2019 ; Poo & Bickford, 2014 ). Furthermore, inundation must be carefully matched with embryonic development, as embryos submerged prematurely may die (Poo et al., 2023 ; Pyburn, 1970 ), but delayed inundation may result in desiccation or starvation (Marco & Blaustein, 1998 ; Touchon et al., 2010 ).…”

“…, and salinity (Allen et al, 2017;Haramura, 2016) can trigger early hatching. Embryos that can initiate hatching in response to environmental cues may face tradeoffs; while early hatching allows embryos to escape predation, hatchlings may be smaller or less developed (Delia et al, 2019;Poo et al, 2023), which can be associated with greater larval predation risk and lower larval survival (Delia et al, 2019;Gomez-Mestra et al, 2008;McCoy et al, 2011; but see Vonesh & Bolker, 2005).…”