AFLP analysis shows high incongruence between genetic differentiation and morphology-based taxonomy in a widely distributed tortoise

Abstract

Morphology has traditionally been used to diagnose the taxa of various taxonomic ranks. However, there is growing evidence that morphology is not always able to reveal cryptic taxa, and that pronounced morphological variation could reflect phenotypic plasticity rather than evolutionary divergence. Spur‐thighed tortoises (the Testudo graeca complex), distributed in the western Palaearctic region, are characterized by high morphological variability and complicated taxonomy, which are under debate. Previous molecular studies using mainly mitochondrial DNA (mtDNA) sequences have revealed incongruence between genetic differentiation and morphology‐based taxonomy, suggesting that morphological variability is the result of phenotypic plasticity and stabilizing selection, which masks the true genealogies. In the present study, we used a range‐wide sampling and nuclear Amplified fragment length polymorphism (AFLP) markers to investigate genetic differentiation within the T. graeca complex. We found that spur‐thighed tortoises are differentiated into four geographically well‐defined AFLP groups: Balkans–Middle Eastern, western Mediterranean, Caucasian and central‐eastern Iranian. Compared with the distribution of mtDNA lineages, the groups are largely concordant, although the AFLP markers are less sensitive and distinguish fewer groups than do mtDNA sequences. The AFLP groups show an allopatric or parapatric distribution. The AFLP differentiation conflicts with the previously proposed morphology‐based taxonomy of the complex, suggesting that local adaptation to different environmental conditions may have led to the great extent of morphological variation within the same lineages. We propose a re‐evaluation of the taxa that were confirmed genetically using a thorough morphological analysis corrected for phenotypic plasticity. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ●●, ●●–●●.

Gene flow among deeply divergent mtDNA lineages of Testudo graeca (Linnaeus, 1758) in Transcaucasia

“…Root length shortened by 80%. On the right, the correlation of mtDNA clades with AFLP groups (Mikulicek et al, 2013) and microsatellite clusters {K = 3, this study) is shown. Note that mtDNA clades A and E represent one and the same AFLP cluster, although they are not sister groups.…”

“…Merging colours for microsatellite data symbolize admixed individuals. The letter C in the Caucasian AFLP group indicates the occurrence of a mitochondrial haplotype of clade C in a tortoise from Katekh, Azerbaijan, belonging to the Caucasian AFLP group (Mikulicek et al, 2013(Mikulicek et al, ). al., 2007.…”

“…In a follow-up study, Mikulicek et al (2013) re-examined the differentiation within the T. graeca complex using more sensitive AFLP fingerprints and found four well-differentiated AFLP groups. Two of these groups, the western Mediterranean AFLP group and the centraleastern Iranian AFLP group (Mikulicek et al, 2013), correspond to the completely or largely allopatric mitochondrial lineages from the western Mediterranean (mtDNA clade B) and eastern Iran (mtDNA clade F; fig.…”

Turtles and Tortoises of the World During the Rise and Global Spread of Humanity: First Checklist and Review of Extinct Pleistocene and Holocene Chelonians.

“…comm.). The taxon occurred in the geographic region now occupied by T. g. armeniaca (including its junior synonym, T. g. pallasi), as determined genetically Mashkaryan et al 2013;Mikulíček et al 2013), and may be ancestral to that or one of the other subspecies in the general Caucasus region, T. g. ibera or T. g. buxtoni. (Gmira 1993;Gmira et al 2013).…”

Color and pattern variation of the Balkan whip snake,Hierophis gemonensis (Laurenti, 1768)

“…This suggests, surprisingly, how often the evolution of genotype does not correspond to the evolution of phenotype. On the other hand, some species are phenotypically very variable but genetically more uniform (e.g., Testudo graeca: Fritz et al 2007;Mikulíček et al 2013; Natrix natrix: Kindler et al, 2013). However, different colorations in similar species can also reflect deep speciation processes (e.g., Dasypeltis: Trape et al, 2012).…”