Altitudinally divergent adult phenotypes in Iberian wall lizards are not driven by egg differences or hatchling growth rates

Abstract

The interplay between ecological conditions and life histories has been widely acknowledged in vertebrates, particularly in lizards. Environmental conditions may exert different selective pressures and produce divergent phenotypes even in geographically and genetically close populations. The Iberian wall lizard, constitutes a perfect model organism as it is considered a species complex with a complicated evolutionary history. Here, we focus on two nearby populations in which we examined adult morphology and reproductive investment of wild caught lizards along a 500 m altitudinal gradient with contrasting environmental conditions, where adults show marked morphological differences in spite of being closely related. Also we performed a common garden experiment to examine embryonic and hatchling growth. We focused on reproductive investment per clutch, incubation time, egg size, morphology and growth rate of hatchlings. Results showed clutch size differences between populations that were independent of the larger body size of highland females. However, there were not egg morphological differences between populations, except for egg width, and this difference disappeared after controlling for female body size. Hatchling lizards from both populations did not differ in morphology. Moreover, we did not observe differences between populations nor sexes in hatchling growth. Overall, we provide evidence that the differences in adult body size and clutch size are not driven by size at hatching which is not contributed to by egg size, nor intrinsic hatchling growth rates associated with the environmental conditions experienced in our common garden experiment, suggesting that adult phenotypes are not the result of intrinsic differences between populations.

Dorsal pattern polymorphism in female Iberian wall lizards: differences in morphology, dorsal coloration, immune response, and reproductive investment

“…It is worth noting that the error measurement for size is higher than for the other morphological measurements, reducing the probability of finding significant results. Males from these populations are characterized by deeper heads and longer femora (Ortega et al ., ). Thus, reticulated blotched females, at least with respect to these variables, are more similar to males than striped females.…”

“…clutch size adjusted for female SVL) using the residuals of the regression of log-clutch size on log-female SVL. Hatchling lizards were kept in a climatic chamber under identical environmental conditions than adults (see above) but fed smaller prey (Ortega et al, 2015). Hatchling cages were rotated along shelf rows every 3 days and among shelves each week to control for position effects (Telemeco et al, 2010).…”

Effect of maternal foraging habitat on offspring quality in the loggerhead sea turtle (Caretta caretta)

“…Common garden experiments are frequently conducted to verify whether a polymorphism is shaped by intrinsic factors such as genetics (e.g., Ortega, López, & Martín, 2015). For example, progeny of four sympatric morphs of the Icelandic Arctic char (Salvelinus alpinus) were reared in a common environment but grew differently and matured at different ages, confirming a genetic basis to their life history variations (Skúlason et al, 1996).…”

Environmental drivers of growth rates in Guadarrama wall lizards: a reciprocal transplant experiment

“…Specifically, we hypothesized that if environmental differences were responsible for growth rate differences of juveniles, then the source population would not determine growth rates and, hence, we would find the same phenotypes in the same environment. Conversely, and considering that previous research showed an absence of intrinsic differences (Ortega et al, 2015), if phenotypic divergence between populations is maintained across different environments, maternal effects could be responsible for different juvenile growth rates due to differential allocation of resources to the eggs. We also measured food availability in both populations to test the hypothesis that productivity (i.e.…”

“…We selected these two populations because they differ in adult body size, morphology, coloration and chemical sexual signals, in spite of being genetically closely related (Martín & López, 2006;Gabirot, López & Martín, 2012. Results from a common garden experiment provided evidence that the divergent adult body sizes of these two populations of P. g. guadarramae lizards are not driven by size at hatching nor intrinsic post-hatching growth rates (Ortega, López & Martín, 2015). The work presented here constitutes the next step and aims to determine which factors drive phenotypic plasticity along elevational gradients in this system.…”