Phenotypic plasticity leads to incongruence between morphology-based taxonomy and genetic differentiation in western Palaearctic tortoises (Testudo graeca complex; Testudines, Testudinidae)
Authors: Fritz Uwe , Hundsdörfer Anna , Široký Pavel , Auer Markus , Kami Hajigholi , Lehmann Jan , Mazanaeva Lyudmila , Türkozan Oğuz , Wink Michael 
Published: February 2007

Abstract
Tortoises of the Testudo graeca complex inhabit a patchy range that covers
part of three continents (Africa, Europe, Asia). It extends approximately
6500 km in an east-west direction from eastern Iran to the Moroccan Atlantic
coast and about 1600 km in a north-south direction from the Danube Delta to
the Libyan Cyrenaica Peninsula. Recent years have seen a rapid increase of
recognized taxa. Based on morphological investigations, it was suggested
that this group consists of as many as 20 distinct species and is
paraphyletic with respect to T. kleinmanni sensu lato and T. marginata.
Based on samples from representative localities of the entire range, we
sequenced the mitochondrial cytochrome b gene and conducted nuclear genomic
fingerprinting with ISSR PCR. The T. graeca complex is monophyletic and
sister to a taxon consisting of T. kleinmanni sensu lato and T. marginata.
The T. graeca complex comprises six well-supported mtDNA clades (A-F).
Highest diversity is found in the Caucasian Region, where four clades occur
in close neighbourhood. This suggests, in agreement with the fossil record,
the Caucasian Region as a radiation centre. Clade A corresponds to
haplotypes from the East Caucasus. It is the sister group of another clade
(B) from North Africa and western Mediterranean islands. Clade C includes
haplotypes from western Asia Minor, the southeastern Balkans and the western
and central Caucasus Region. Its sister group is a fourth, widely
distributed clade (D) from southern and eastern Asia Minor and the Levantine
Region (Near East). Two further clades are distributed in Iran (E,
northwestern and central Iran; F, eastern Iran). Distinctness of these six
clades and sister group relationships of (A + B) and (C + D) are
well-supported; however, the phylogeny of the resulting four clades (A + B),
(C + D), E and F is poorly resolved. While in a previous study (Fritz et
al., 2005a) all traditionally recognized Testudo species were highly
distinct using mtDNA sequences and ISSR fingerprints, we detected within the
T. graeca complex no nuclear genomic differentiation paralleling mtDNA
clades. We conclude that all studied populations of the T. graeca complex
are conspecific under the Biological Species Concept. There is major
incongruence between mtDNA clades and morphologically defined taxa.
Morphologically well-defined taxa, like T. g. armeniaca or T. g. floweri,
nest within clades comprising also geographically neighbouring, but
morphologically distinctive populations of other taxa (clade A: T. g.
armeniaca, T. g. ibera, T. g. pallasi ; clade D: T. g. anamurensis, T. g.
antakyensis, T. g. floweri, T. g. ibera, T. g. terrestris), while sequences
of morphologically similar tortoises of the same subspecies (T. g. ibera
sensu stricto or T. g. ibera sensu lato) scatter over two or three
genetically distinct clades (A, C or A, C, D, respectively). This implies
that pronounced morphological plasticity, resulting in phenotypes shaped by
environmental pressure, masks genetic differentiation. To achieve a more
realistic taxonomic arrangement reflecting mtDNA clades, we propose reducing
the number of T. graeca subspecies considerably and regard in the eastern
part of the range five subspecies as valid (T. g. armeniaca, T. g. buxtoni,
T. g. ibera, T. g. terrestris, T. g. zarudnyi). As not all North African
taxa were included in the present study, we refrain from synonymizing North
African taxa with T. g. graeca (mtDNA clade B) that represents a further
valid subspecies.