Does Incubation Temperature Fluctuation Influence Hatchling Phenotypes in Reptiles? A Test Using Parthenogenetic Geckos

Abstract

Many lineages of parthenogenetic organisms have persisted through significant environmental change despite the constraints imposed by their fixed genotype and limited evolutionary potential. The ability of parthenogens to occur sympatrically with sexual relatives may in part be due to phenotypic plasticity in their responses to their environment, especially with respect to incubation temperature--a maternally selected trait. Here we measured the incubation temperatures selected by two lineages of triploid parthenogenic geckos in the Heteronotia binoei complex by allowing them to deposit clutches along a thermal gradient. The average nest temperature selected was 28.4 degrees C, with no significant differences between parthenogenic races or individual clones. To investigate the effect of nest-temperature variability on physiological and morphological traits, we incubated eggs from different races at one of four incubation regimes (32 degrees +/- 0 degrees, +/- 3 degrees , +/- 5 degrees , or +/- 9 degrees C). Embryos incubated at constant 32 degrees C developed faster than embryos reared under increasing extremes of diel temperature fluctuation (+/- 3 degrees , +/- 5 degrees C), and incubation at 32 degrees +/- 9 degrees C was unsuccessful. Incubation regime had no effect on the body size, preferred substrate temperature, or mass-specific .V(O2) of hatchlings. However, parthenogenic race had a significant effect on egg mass, tail length, snout-to-vent length, total length, and .V(O2) . We conclude that developmental traits are strongly influenced by clonal genotypes in this parthenogenic complex but are well buffered against fluctuations in incubation temperature.

Incubation temperature induced phenotypic plasticity in oviparous reptiles: Where to next?

“…However, there is no general relationship between the amplitude of temperature fluctuation and hatchling phenotype, the effects if present, are species specific (see below). Yet other studies have found no effect of changing fluctuating temperature regimes on hatchling phenotype (e.g., Andrewartha et al., ; Demuth, ; Du & Shine, ; Du et al., ). Hence, there is wide variation in the influence, or not, that incubation temperature has on reptile hatchlings.…”

Does Thermal Variability Experienced at the Egg Stage Influence Life History Traits across Life Cycle Stages in a Small Invertebrate?

“…A number of studies have explored the effects of egg temperatures on life history performances in vertebrate ectotherms [5] and these studies have shown that egg temperature impacts egg traits [6] and also post-hatching traits [7]. On the other hand, invertebrates are different from vertebrate ectotherms by exhibiting a modularity of life cycles that may assist in dealing with environmental variability by possible insulation of later stages from disturbances during embryogenesis [8].…”

The Lesser Known Challenge of Climate Change: Thermal Variance and Sex-Reversal in Vertebrates with Temperature-Dependent Sex Determination

“…However, larger variation resulting from a compensatory nesting response in C. picta might expose the shallower eggs to lethally- or suboptimaly-high temperatures, as occurred in our study and in other species (e.g. [48]). …”