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M. Korn et al. • Sister species within Triops cancriformis

Discussion (Ghigi 1921; Longhurst 1955; Alonso 1996). However, our
Identification of haplotype groups results clearly demonstrate that numerous dorsal carina spines
Within Triops cancriformis 17 haplotype groups were identi- may also be found in T. c. simplex (see below), which seems to
fied by characterizing diagnostic sites in the 16S sequences render a morphological separation of both taxa impossible.
[Appendix 1; the haplotype groups ‘Central European’ (Triops The same is also true for reproductive mode. Typical
c. cancriformis) and ‘Northern Spain’ (T. c. simplex) are geneti- T. c. cancriformis are either unisexual or, if males are present,
cally identical, but are listed and treated separately in the they occur only in low numbers, typically not reaching 30%
morphological analyses to quantify phenotypic differences of the population (see References in Scanabissi et al. 2005).
for the assessment of possible taxonomic implications]. The All documented cases of southern bisexual populations with
comparison of the 16S sequence of T. cancriformis from Japan equal sex ratio refer to populations of Spain and northern
included in our analyses (Fig. 4, labelled T.c. AB084514) to Africa (Scanabissi et al. 2005; for more information see also
the one published in Suno-Uchi et al. (1997; this sequence Thiéry 1987 and Machado et al. 1999). However, table 2 and
was not included in our analyses due to the high amount of fig. 4 in the same paper (Scanabissi et al. 2005) indicated
indels in otherwise conserved positions) indicates that the the occurrence of a population with equal sex ratio in the
Adenin in position 25 (Appendix 1) represents a diagnostic Corbières, southern France. We expect this most probably to
site and Japanese specimen appear to represent a separate be a mistake, as Thiéry (1988) only reported one population
haplotype group within T. c. cancriformis. The identified of Triops (T. c. cancriformis) in this region, populating the
16S haplotype groups are corroborated by 12S sequences Opoul temporary pool, from which Knoepffler (1978) reported
(data not shown), which were obtained (or were available in the complete absence of males in a sample of 300 specimens.
GenBank) for a subset of samples. However, the 16S GenBank Thus, we can conclude that typical T. c. cancriformis have never
sequences AY159576 and AY159577 from specimen collected been observed to reach an equal sex ratio [a sample of three
in Oristano, Sardinia, split to two of our 16S haplotype groups males and two females of T. c. cancriformis reported for
(‘Central European’ and ‘Austrian’, respectively). The 12S Favignana Island, Sicily (Cottarelli & Mura 1995) was too
sequences of these specimen clearly show that both specimen small to give an accurate estimate of this population’s sex ratio,
belong to the ‘Central European’ haplotype group and that and it also appears reasonable to speculate that it was actually
the Adenin in position 253 of the 16S sequence AY159577 a sample of T. c. simplex, considering that no T. cancriformis
(Appendix 1; indicative of the ‘Austrian’ haplotype) is a mislead- populations with equal sex ratio have been reported for the
ing concurrence, and possibly erroneous. Nevertheless, for the islands of Sardinia and Sicily or for mainland Italy]. There is
assignment of single T. c. cancriformis specimen to one of our no consensus about the reproductive mode of these populations,
haplotype groups, additional 12S data should be consulted. which are either thought to reproduce by parthenogenesis or
For the single sample from the United Arab Emirates, 12S are regarded as selfing hermaphrodites (reviewed in table 1 in
data confirm its affiliation to the ‘Austrian’ haplotype group. Scanabissi et al. 2005). Recent genetic studies (Cesari et al.
2004) indicate the occurrence of both hermaphroditic and
The Triops cancriformis cancriformis lineage parthenogenetic populations. Parthenogenesis was suggested
Our genetic data show that the specimens from Girona for a unisexual population from Oristano, Italy, while hermaph-
(northern Spain) belong to T. c. cancriformis, and not to roditism was reported for a population with male occurrence
T. c. simplex as stated by Margalef (1951, 1953) and Alonso from the Morava floodplain, Austria (Cesari et al. 2004).
(1985, 1996). Furthermore, they do not form a monophyletic Interestingly, in typical T. c. cancriformis, reproductive modes
subgroup within T. c. cancriformis but are unresolved within do not appear to correlate to haplotype groups, as populations
the clade (Fig. 4A). However, northern Spanish females do with males occur at least in three different haplotype groups
reach similar high values in the number of apodous abdomi- that also form apparently unisexual populations (M.K.
nal segments to females of T. c. simplex, and in this character, pers. obs.).
both differ significantly (P < 0.05, Tukey post-hoc Test) from The cryptic T. c. cancriformis population from Girona
all typical T. c. cancriformis, which show much lower values. (northern Spain) did not show a significant deviation from an
This is the only morphological character investigated that equal sex ratio in 37 of 52 samples where adult specimens
allows separation of all typical T. c. cancriformis from were present, including those made at both early and late
T. c. simplex. Thus the northern Spanish population, which is phases of the inundation events (Boix et al. 2002). Thus, this
morphologically identical to North African T. c. simplex, is population typically has an equal sex ratio. Additionally, single
morphologically clearly separated from typical T. c. cancriformis, females that were raised separately did lay some eggs in
revealing it to be a cryptic lineage of this subspecies. Only the the absence of males, but no larvae hatched (M.K. pers. obs.).
presence of dorsal carina spines in this population could have Therefore, this is a typical gonochoric population. Thus,
suggested its morphological affiliation to T. c. cancriformis the T. c. cancriformis lineage clearly shows high plasticity in

© 2006 The Authors. Journal compilation © 2006 The Norwegian Academy of Science and Letters • Zoologica Scripta, 35, 4, July 2006, pp301–322 313