The aim of this paper was to determine how the pistachio trees evolve, and the evolving factors that influence pistachio population establishment. For that, we investigated pistachio genetic structure from some regions of Tunisia, by sequencing two noncoding chloroplastic regions (trnL (UAA) and trnL-trnF intergenic spacer). We found strong genetic diversity among groups, with the absence of high differentiation between population pairs. A deep phylogeographical break separated two major clusters: "El-Guetar and "Gafsa/Sidi-Bouzid. This conclusion is proved by the haplotype networks, the phylogenetic trees, and the molecular variance analysis. Different interpretations were proposed to explain this cytoplasm dimorphism, based on the molecular evolution and demographic history analysis: (1) the domestication events, which are very important to understand the variability between the prospective areas, (2) the gene flow between them, a process that occurs both in time and in space through pollen and seeds, and strongly interacts with the local farming systems, (3) the geographical barriers that exist, which limit gene flow transfer and make particular climatic conditions of the El-Guetar oasis. Given that, the genetic diversity study within Tunisian pistachio cultivars is very useful to contribute to the national management effort for the improvement and conservation of pistachio genetic resources. Moreover, in 2017, Tunisia ranked among the top 10 countries in global pistachio production. Thus, studying the diversity of Tunisian pistachio can make an important impact on global production.
The cytochrome oxidase subunit I (COI) gene was amplified and analyzed
for 70 Mediterranean Chondrosia reniformis, collected from eight
localities in Tunisia. Polymorphism results revealed high values of
haplotype diversity (Hd) and very low nucleotide diversity (π). Thus,
these results suggest that our sponge populations of C. reniformis may
have undergone a bottleneck followed by rapid demographic expansion.
This suggestion is strongly confirmed by the results of neutrality tests
and “mismatch distribution”. The important number of haplotypes
between localities and the high genetic differentiation (Fst ranged from
0.590 to 0.788) of the current C. reniformis populations could be
maintained by the limited gene flow Nm (0.10 - 0.18). Both haplotype
Network and the biogeographic analysis showed a structured distribution
according to the geographic origin. C. reniformis populations are
subdivided into two major clades: Western and Eastern Mediterranean.
This pattern seems to be associated with the well-known discontinuous
biogeographic area: the Siculo-Tunisian Strait, which separates two
water bodies circulating with different hydrological, physical, and
chemical characteristics. The short dispersal of pelagic larvae of C.
reniformis and the marine bio-geographic barrier created high
differentiation among populations. Additionally, it is noteworthy to
mention that the “Mahres / Kerkennah” group diverged from Eastern
groups in a single sub-clade. This result was expected, the region
Mahres / Kerkennah, presented a particular marine environment.
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