Interpopulational and seasonal variation in the chemical signals of the lizardGallotia galloti

Abstract

Communicative traits are strikingly diverse and may vary among populations of the same species. Within a population, these traits may also display seasonal variation. Chemical signals play a key role in the communication of many taxa. However, we still know far too little about chemical communication in some vertebrate groups. In lizards, only a few studies have examined interpopulational variation in the composition of chemical cues and signals and only one study has explored the seasonal effects. Here we sampled three subspecies of the Tenerife lizards (Gallotia galloti) and analyze the lipophilic fraction of their femoral gland secretions to characterize the potential interpopulational variation in the chemical signals. In addition, we assessed whether composition of these secretions differed between the reproductive and the non-reproductive season. We analyzed variations in both the overall chemical profile and the abundance of the two main compounds (cholesterol and vitamin E). Our results show interpopulational and seasonal differences in G. gallotia chemical profiles. These findings are in accordance with the high interpopulational variability of compounds observed in lizard chemical signals and show that their composition is not only shaped by selective factors linked to reproductive season.

Seasonal and interpopulational phenotypic variation in morphology and sexual signals of Podarcis liolepis lizards

“…The seasonal differences found in this work are in line with the scarce scientific literature on seasonal variation in chemical signals of lizards [55, 61]. Specifically, we found that the most abundant compounds, squalene and cholesterol, showed higher levels in the non-reproductive season in both populations.…”

“…Specifically, we found that the most abundant compounds, squalene and cholesterol, showed higher levels in the non-reproductive season in both populations. An increase in cholesterol levels in the non-reproductive season was also found in Gallotia galloti lizards [61]. Cholesterol has been proposed as a protector of other compounds with potential pheromone activity, lacking a signaling function [96].…”

“…In the context of communication optimization, chemical signals used for scent marking should ensure efficiency by appropriately tuning to environmental factors such as local humidity and temperature that affect their volatility and, therefore, their persistence and transmission through the environment [ 53 – 54 ]. However, their seasonal [ 55 ] and intraspecific variability have been rarely explored in lizards [ 56 – 61 ]. Besides chemical signals, many lizards have also evolved colourful sexually dimorphic ornaments that are used in intraspecific relationships [ 62 ].…”

Morph-specific protein patterns in the femoral gland secretions of a colour polymorphic lizard

“…This weakness can be explained considering that samples for the lipid study came from three distinct populations (no information are available about the site × morph frequency in the sample) over a period of two months (April to May). As both population and season can affect the composition and amount of the lipid fraction 67,90,92,117–121 , potentially in a morph-specific way 43,44,122 , an unbalanced sampling of morphs by period and population could have biased results. On the opposite, the observed differences in the protein pattern cannot be imputed to population, timing, or to sampling bias, since all sampled lizards came from the same site, were collected on the same day, at the peak of the breeding season 43,86 , and the pooled secretions were obtained by balancing the contribution of each donor (see Material and Methods).…”

The Macroecology of Chemical Communication in Lizards: Do Climatic Factors Drive the Evolution of Signalling Glands?

“…Although studies of animal communication have primarily focused on the role that visual (trait displays) and acoustic (sounds in specific frequencies and patterns) signals play in shaping interactions, the role of chemical communication has gained an increasingly more central role in understanding the evolution of social and sexual dynamics within populations (Alberts 1992 ; Schwenk 1995 ; Martin and Lopez 2000 ; Kratochvil and Frynta 2002 ; Ibáñez et al 2017 ; MacGregor et al 2017 ). The evolution of traits responsible for chemical communication has been suggested to be driven by selection arising from competition over mates (sexual selection), and from ecological pressures that affect signal efficiency (Alberts 1992 ; Escobar et al 2001 ; Baeckens et al 2017b ; García-Roa et al 2017c ). As a result, the hypothesis that variation in the number of signalling glands is shaped by geographic gradients of climatic factors that affect the efficiency of the signal delivery, thus resulting in macroecological patterns of variation in chemical phenotypes, has been suggested (Escobar et al 2003 ).…”