Introduction to the special issue—Developmental plasticity in reptiles: Physiological mechanisms and ecological consequences

Warner, Daniel A.; Du, Wei‐Guo; Georges, Arthur

doi:10.1002/jez.2199

Cited by 26 publications

(20 citation statements)

References 109 publications

(138 reference statements)

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“…One of the most dynamic sources of physiological phenotypic plasticity is environmental temperature early in development, and predicting persistent physiological consequences for organisms across taxa is an area of significant current research interest (Kim et al, 2017; Noble et al, 2018; Ruthsatz et al, 2018; Warner et al, 2018). We explored this central idea in comparative physiology using P. hypochondriaca , an amphibian that experiences a broad range of temperatures throughout its life history.…”

Section: Discussionmentioning

confidence: 99%

Immediate and Persistent Effects of Temperature on Oxygen Consumption and Thermal Tolerance in Embryos and Larvae of the Baja California Chorus Frog, Pseudacris hypochondriaca

et al. 2019

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The developmental environment has significant immediate effects on phenotypes, but it may also persistently or permanently shape phenotypes across life history. This study examined how developmental temperature influenced embryonic and larval phenotypes of Baja California chorus frog ( Pseudacris hypochondriaca ), an abundant amphibian in southern California and northern Baja California. We collected egg clutches from native ponds in northern San Diego County within 24 h of fertilization, and clutches were separated and distributed between constant temperatures of 10, 15, 20, and 25°C for incubation. Oxygen consumption rate ( O 2 ), developmental stage, and embryo and yolk masses were measured throughout development. Time to 50% hatch, survival at 50% hatch, and hatch duration were determined. Development rate was strongly affected by temperature, with warmer temperatures reducing time to hatch and hatch duration. Survival to hatch was high across all temperatures, >90%. Mass-specific O 2 of embryos either remained constant or increased throughout development, and by hatching energy demand was significantly increased at higher temperatures. There were limited temperature effects on growth, with embryo and yolk dry mass similar between temperatures throughout embryonic development. To examine long-term effects of embryonic temperature, we reared hatchlings from each temperature until onset of larval feeding. Once feeding, larvae were acclimated to 20 or 25°C (>2 weeks). Following acclimation to 20 or 25°C, we measured larval mass-specific O 2 and critical thermal maximum (CTMax) at a common developmental stage (Gosner stages 32–36, “hindlimb toe differentiation”). Embryonic temperature had persistent effects on larval O 2 and CTMax, with warmer temperatures generally resulting in similar or higher O 2 and CTMax. This partially supported a “warmer is better” effect of embryonic incubation temperature. These results suggest that in a thermally robust amphibian species, temperature may program the phenotype during early development to construct traits in thermal tolerance and energy use that may persist. Overall, P. hypochondriaca displays a thermally robust phenotype, and it is possible that amphibians that possess a wider range of phenotypic plasticity will be relatively more successful mitigating effects of climate change.

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Section: Discussionmentioning

confidence: 99%

Immediate and Persistent Effects of Temperature on Oxygen Consumption and Thermal Tolerance in Embryos and Larvae of the Baja California Chorus Frog, Pseudacris hypochondriaca

et al. 2019

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“…In summary, despite much attention given to phenotypic plasticity in the responses of reptiles to temperature (see reviews in 68 , 69 ), natural selection in response to hydric conditions is less understood. Yet precipitation, and thus hydric conditions, may be a better predictor of variation in natural selection across populations of terrestrial animals 70 .…”

Section: Discussionmentioning

confidence: 99%

Plasticity in nest site choice behavior in response to hydric conditions in a reptile

Doody

McGlashan

Fryer

et al. 2020

Sci Rep

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Natural selection is expected to select for and maintain maternal behaviors associated with choosing a nest site that promotes successful hatching of offspring, especially in animals that do not exhibit parental care such as reptiles. In contrast to temperature effects, we know little about how soil moisture contributes to successful hatching and particularly how it shapes nest site choice behavior in nature. The recent revelation of exceptionally deep nesting in lizards under extreme dry conditions underscored the potential for the hydric environment in shaping the evolution of nest site choice. But if deep nesting is an adaptation to dry conditions, is there a plastic component such that mothers would excavate deeper nests in drier years? We tested this hypothesis by excavating communal warrens of a large, deep-nesting monitor lizard (Varanus panoptes), taking advantage of four wet seasons with contrasting rainfall amounts. We found 75 nests during two excavations, including 45 nests after a 4-year period with larger wet season rainfall and 30 nests after a 4-year period with smaller wet season rainfall. Mothers nested significantly deeper in years associated with drier nesting seasons, a finding best explained as a plastic response to soil moisture, because differences in both the mean and variance in soil temperatures between 1 and 4 m deep are negligible. Our data are novel for reptiles in demonstrating plasticity in maternal behavior in response to hydric conditions during the time of nesting. The absence of evidence for other ground-nesting reptile mothers adjusting nest depth in response to a hydric-depth gradient is likely due to the tradeoff between moisture and temperature with changing depth; most ground-nesting reptile eggs are deposited at depths of ~ 2–25 cm—nesting deeper within or outside of that range of depths to achieve higher soil moisture would also generally create cooler conditions for embryos that need adequate heat for successful development. In contrast, extreme deep nesting in V. panoptes allowed us to disentangle temperature and moisture. Broadly, our data suggest that ground-nesting reptiles can assess soil moisture and respond by adjusting the depth of the nest, but may not, due to the cooling effect of nesting deeper. Our results, within the context of previous work, provide a more complete picture of how mothers can promote hatching success through adjustments in nest site choice behavior.

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“…Although many studies have been conducted to understand the effects of nest microhabitats on the development of reptile eggs, most work has studied factors other than moisture (Warner, Du, & Georges, 2018) and more research is required to understand the context‐dependent effects of nesting behaviour on water uptake by eggs. Although, treatment‐specific patterns of water uptake and body condition did not mirror each other (Figure 3), singly incubated eggs absorbed more water and generated hatchlings with greater body condition compared to eggs incubated in aggregates.…”

Section: Discussionmentioning

confidence: 99%

Communal egg‐laying behaviour and the consequences of egg aggregation in the brown anole (Anolis sagrei)

et al. 2020

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Communal nesting is a behaviour that involves multiple females laying eggs in the same nest or nesting site. This behaviour may be a consequence of a shortage of preferable nest sites (constraint hypothesis) or an adaptation generated by fitness benefits associated with egg aggregation (adaptive hypothesis). Experimental tests of these hypotheses require information about maternal nest site choice and its fitness consequences. To address these, we studied a lizard (brown anole; Anolis sagrei) that produces single‐egg clutches, but often aggregates eggs in nest sites. In a lab study, females were given the option of nesting in (a) soil previously used as nest substrate vs. fresh soil and (b) soil with eggshells vs. without eggshells. We also experimentally examined the effects of egg aggregation by incubating eggs singly, in groups of four, and in groups of nine. We recorded egg surface temperature, water uptake, and hatchling morphology. Females were more likely to nest in pots with used soil and with eggshells than in pots with fresh soil or without eggshells. We observed no effects of egg aggregation on egg survival, egg temperature, or most measures of hatchling morphology. However, singly‐incubated eggs absorbed more water than eggs incubated in the four and nine egg aggregations and this resulted in offspring with greater body condition (i.e. heavier for their length) at hatching. The behavioural experiment demonstrates that females actively choose nest sites that have been used previously (as expected under the adaptive hypothesis), but the egg‐aggregation experiment shows no benefits to offspring based on the variables measured. Thus, results of the behaviour study support the adaptive hypothesis; however, results from our egg‐incubation study do not. Likely, the adaptive and constraint hypotheses are not mutually exclusive, and a diversity of factors influence the evolution of communal nesting behaviour.

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Introduction to the special issue—Developmental plasticity in reptiles: Physiological mechanisms and ecological consequences

Abstract: Scientific interest in developmental plasticity spans many disciplines, and research on reptiles has provided many insights into this field. We highlight these contributions, review the field's history, and introduce the special issue on this topic .

Cited by 26 publications

References 109 publications

Immediate and Persistent Effects of Temperature on Oxygen Consumption and Thermal Tolerance in Embryos and Larvae of the Baja California Chorus Frog, Pseudacris hypochondriaca

Immediate and Persistent Effects of Temperature on Oxygen Consumption and Thermal Tolerance in Embryos and Larvae of the Baja California Chorus Frog, Pseudacris hypochondriaca

Plasticity in nest site choice behavior in response to hydric conditions in a reptile

Communal egg‐laying behaviour and the consequences of egg aggregation in the brown anole (Anolis sagrei)

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