Genetic Diversity in Tunisian Ceratonia siliqua L. (Caesalpinioideae) Natural Populations |
| |
Authors: | Afif Makrem Ben Fadhel Najeh Khoudja Mohamed Laarbi Boussaïd Mohamed |
| |
Institution: | (1) National Institute of Applied Science and Technology, Department of Biology, Laboratory of Plant Biotechnology, Centre Urbain Nord, BP. 676, 1080 Tunis Cedex, Tunisia;(2) National Institute of Research in Agricultural Engineering, Water and Forests, BP. 10, 2080 Ariana, Tunisia |
| |
Abstract: | The last two centuries witnessed the human-caused fragmentation of Tunisian Ceratonia siliqua L. (Caesalpinoideae) populations which were often represented by scattered individuals. Seventeen populations growing in
four bioclimatic zones: sub-humid, upper semi-arid, mean semi-arid and lower semi-arid zones, were sampled for allozyme diversity
to assess their genetic diversity and structuration using eight isozymes revealed by starch gel electrophoresis. The species
showed high diversity within populations. The average number of alleles per polymorphic locus was 1.98, the percentage of
polymorphic loci was 83.4% and the mean observed heterozygosity (Ho) and expected heterozygosity (He) under Hardy–Weinberg
equilibrium were respectively 0.247 and 0.316. A substantial level of inbreeding within populations induced by Wahlund effect,
was observed (FIS = 0.231). High diversity resulted from the great number of genotypes in the ancestral population before fragmentation, favoured
by the outbreeding of the species. High differentiation and low gene flow were detected among populations (FST = 0.200) and among pairs of ecological zones (0.113< FST <0.198). However, the differentiation coefficient of the four zones was low (FST = 0.085) and similar to the average FST for forest trees. Population structuration depends on geographic distance between sites rather than bioclimate, indicating
that structuration has occurred slowly and that climatic conditions have had little effect. Nei's genetic distances (D) between populations were low and ranged from 0.004 to 0.201. Mean D value for all population was 0.087. The UPGMA clustering established for all populations through Nei's genetic distances
did not clearly show that, for the majority of populations, grouping had resulted from ecological factors or geographic location.
The substantial differentiation and the high genetic similarities between populations indicate that populations have been
recently isolated as a result of anthropic pressure. In-situ conservation strategies must first focus on populations with a high level of genetic diversity and rare alleles. Appropriate
conservation action should take account of bioclimatic zones. Ex-situ preservation should be based on a maximum number of individuals collected within populations in each ecological group and
their propagation in different bioclimates by means of cuttings. |
| |
Keywords: | Carob Ceratonia siliqua Conservation Ecological group Genetic structure Isolation by distance Isozyme polymorphism |
本文献已被 SpringerLink 等数据库收录! |
|