Selection for background matching drives sympatric speciation in Wall Gecko

Abstract

The Wall Gecko shows heterogeneous colour pattern, which may vary among individuals, depending on the time of day and on the habitat segregation. Nocturnal pale geckos live exclusively on walls. Diurnal dark geckos preferentially live on olive tree trunks, demonstrating an ability to change skin colour that is superior to that of the pale gecko and allows diurnal geckos becoming camouflaged on the diverse substrates occupied during the day. In our study, the nocturnal/pale/wall and diurnal/dark/trunk geckos could be considered the extremes of an ecological cline of morphological variation on which divergent selection may be acting. Combining the effect of balancing selection on nocturnal geckos and disruptive selection between two sympatric populations could lead to speciation. All geckos analysed here belong to the same species, as confirmed by genetic characterization, however diurnal and nocturnal gecko populations seem to be in an early stage of incipient speciation. These two different morphs still combine genes, as revealed by neutral genetic markers, yet they show complete separation according to the analyses of mtDNA coding genes. Experimental results show that diurnal and nocturnal geckos do not swap their niches, likely because the predation pressure causes severe selection for background matching. Genomic analysis of complete mtDNA suggests that nocturnal geckos seem to be under balancing selection perhaps due to the narrow niche in which they live, whereas the daytime population has more opportunity in fitting into the multiple available niches, and they experience positive selection. Here we hypothesize that the ecological segregation that we are witnessing between the nocturnal and diurnal geckos, can lead to a ecological speciation.

Fixation of genetic variation and optimization of gene expression: The speed of evolution in isolated lizard populations undergoing Reverse Island Syndrome

“…A total of 15 mtGenomes (equally distributed on Punta Campanella, Capri island and Scopolo islet) were sequenced. Whole mtDNA extractions (Punta Campanella, N = 5; Capri island, N = 5; Scopolo islet, N = 5) were performed using PureLink HiPure Plasmid DNA Purification Kits (Invitrogen), according to manufacturer’s recommendations, except for using 25 mg of tissue and initial mechanical disruption of samples for 1 h in a Phosphate Buffered Saline [35] Blank extractions without samples were systematically performed to monitor potential cross-contamination.…”

Ecological, behavioral, and phylogenetic influences on the evolution of dorsal color pattern in geckos*

“…; Fulgione et al. ), and camouflage is the primary function of dorsal pigmentation in other squamate groups (Allen et al. ; Marshall et al.…”

Identification and Characterization of a Rhodopsin Kinase Gene in the Suckers of Octopus vulgaris: Looking around Using Arms?

“…This capability could affect the predatory performance of octopuses, allowing them to track down a hidden prey, detecting their presence in dark burrows due to their bioluminescence [ 60 , 61 ]. The diffuse light sensing ability could have a significant role in their ability to change color to camouflage through background matching, guiding the highly specialized chromatic elements in their skin to display complex and rapidly changing color patterns at the peripheral level, without using the central nervous system, speeding up the response to environmental changes, as observed for other species [ 62 , 63 , 64 , 65 , 66 ]. Interestingly, the enlarged suckers found in the same area of the arm did not express a higher level of Ov-GRK1, these suckers, only found in males, probably have other specific roles.…”