Hydric conditions during incubation influence phenotypes of neonatal reptiles in the field

Abstract

Abstract1. Phenotypic variation is strongly impacted by environmental conditions experienced during development. Substantial laboratory research has shown that reptiles with flexible-shelled eggs are particularly sensitive to hydric conditions, yet research on nests in the wild is sparse. 2. In this 2-year field experiment, we explore the influence of hydric conditions during incubation on phenotypic traits of hatchling painted turtles (Chrysemys picta). Using a split-clutch design, we created two artificial nests adjacent to each maternally selected nest site. Half the eggs incubated in a nest that received regular supplemental watering, while the control nest was exposed to natural precipitation only. 3. Our results suggest that the influence of the hydric environment on developing reptilian embryos is context dependent. Supplemental water applied to nests in a drier than normal season elicited the expected biotic responses, based on laboratory experiments. However, when the soil surrounding C. picta eggs was already highly moist, the additional water from supplemental application effectively stunted embryonic development. 4. Our experiment confirms that hydric conditions of the soil during incubation in the wild can substantially influence phenotypic variation of reptiles with flexible-shelled eggs. Additionally, our experiment highlights the importance of complex interactions in the field that are often unexplored in laboratory experiments, reiterating the importance of validating laboratory work with field experiments. 1. Phenotypic variation is strongly impacted by environmental conditions experienced during development. Substantial laboratory research has shown that reptiles with flexible-shelled eggs are particularly sensitive to hydric conditions, yet research on nests in the wild is sparse. 2. In this 2-year field experiment, we explore the influence of hydric conditions during incubation on phenotypic traits of hatchling painted turtles (Chrysemys picta). Using a split-clutch design, we created two artificial nests adjacent to each maternally selected nest site. Half the eggs incubated in a nest that received regular supplemental watering, while the control nest was exposed to natural precipitation only. 3. Our results suggest that the influence of the hydric environment on developing reptilian embryos is context dependent. Supplemental water applied to nests in a drier than normal season elicited the expected biotic responses, based on laboratory experiments. However, when the soil surrounding C. picta eggs was already highly moist, the additional water from supplemental application effectively stunted embryonic development. 4. Our experiment confirms that hydric conditions of the soil during incubation in the wild can substantially influence phenotypic variation of reptiles with flexible-shelled eggs. Additionally, our experiment highlights the importance of complex interactions in the field that are often unexplored in laboratory experiments, reiterating the importance of validating laboratory work...

Geographic variation in thermal sensitivity of early life traits in a widespread reptile

“…However, this phenotypic variation was not explained by our macroclimatic proxy, unlike in many systems where latitudinally linked climatic conditions accord with patterns of certain traits observed in nature (Bradshaw & Holzapfel, ; Coyne & Beecham, ; David & Bocquet, ). Instead, environmental aspects that better reflect microclimates experienced in nests may drive variation in phenotypic reaction norms among locations in our system, including precipitation/hydric conditions (Bodensteiner et al, ), nest‐shade cover (Janzen, ), and/or regional weather patterns (e.g., thermal variation; Vasseur et al, ).…”

“…We split eggs from a clutch across treatments to account for potential maternal effects. Incubation temperature and substrate water potential (−150 kPa) remained constant throughout development, with water added weekly to the vermiculite to maintain moist hydric conditions, which are important for proper development (Bodensteiner, Mitchell, Strickland, & Janzen, ; Gutzke & Packard, ). We incubated eggs in REVCO BOD50 environmental chambers, rotated egg boxes twice weekly to minimize impacts of within‐chamber thermal gradients, and monitored temperatures with a Thermochron iButton contained within an empty egg box in the center of each chamber (±0.2°C) (e.g., St. Juliana, ).…”

Hydrological and thermal properties of moss and lichen species on rock barrens: Implications for turtle nesting habitat

“…Although soil density sampled under Polytrichum and Cladonia was comparable (Figure b), the presence of dense Cladonia at the surface (Figure a) could provide additional protection against turtle egg desiccation during periods of drought. Cladonia could provide an important advantage because turtle eggs have been found to have a greater hatching rate when incubated in moist soils (Packard, Packard, Miller, & Boardman, ) and hatchling size is positively correlated with soil wetness (Packard, ; Packard et al, ), although oversaturation can decrease hatching success (Bodensteiner, Mitchell, Strickland, & Janzen, ). Furthermore, as a result of moisture retention characteristics (Figure ) and high porosity (Figure a), the moss/lichen overlying soil can serve as an insulator, where low thermal diffusivity (Figure b) can regulate temperature fluctuations despite the shallow nature of this habitat (Lindo & Gonzalez, ; Turetsky, ).…”

Quantifying the effects of embryonic phenotypic plasticity on adult phenotypes in reptiles: A review of current knowledge and major gaps

“…Oviparous reptiles also display considerable variation in eggshell structure (Packard, Packard, & Boardman, 1982), which is important for how reptile eggs exchange water with the environment. In species with flexible-shelled eggs, the hydric conditions of the incubation substrate can substantially influence offspring phenotypes in ways that impact survival (Alberts, Perry, Lemm, & Phillips, 1997;Bodensteiner, Mitchell, Strickland, & Janzen, 2015;Brown & Shine, 2018;Janzen, 1993;Packard, Packard, Miller, & Boardman, 1987).…”