Hichem Ben Slimen

Biochemical genetic relationships among Tunisian hares (Lepus sp.), South African cape hares (L. capensis), and European brown hares (L. europaeus).

Tunisian hares (n = 45), currently assigned to Lepus capensis, were assayed for allelic variation at 40 allozyme loci, and allele frequencies at 32 loci were directly compared with earlier data of South African cape hares (L. capensis, n = 9) and European brown hares (L. europaeus, n = 244) to reveal genetic relationships among them. European mountain hares (L. timidus, n = 200) were used for outgroup comparison. In the Tunisian hares 27.5% of the loci were polymorphic with 2–4 alleles. Among all alleles at polymorphic loci, 15.1% occurred exclusively in Tunisian hares, 5.7% exclusively in cape hares, and 7.5% exclusively in brown hares at low frequencies. Not a single locus showed alternately fixed alleles between the samples of the L. capensis/L. europaeus complex. Levels of absolute and relative genetic differentiation among the samples of the L. capensis/ L. europaeus complex were low, relative to pairwise comparisons involving mountain hares. Diverse cluster analyses and multidimensional scaling of various pairwise genetic distance matrices concordantly grouped Tunisian hares with brown hares, and South African cape hares clustered only slightly farther apart, whereas mountain hares were distinctly separate. These results suggest regionally distinct phylogenetic units within an overall cohesive gene pool in the L. capensis/ L. europaeus complex, supporting Petters view that all North African hares belong to L. capensis except for one local population of savanna hares, and that cape hares and brown hares are conspecific.

Sex-specific selection for MHC variability in Alpine chamois

BackgroundIn mammals, males typically have shorter lives than females. This difference is thought to be due to behavioural traits which enhance competitive abilities, and hence male reproductive success, but impair survival. Furthermore, in many species males usually show higher parasite burden than females. Consequently, the intensity of selection for genetic factors which reduce susceptibility to pathogens may differ between sexes. High variability at the major histocompatibility complex (MHC) genes is believed to be advantageous for detecting and combating the range of infectious agents present in the environment. Increased heterozygosity at these immune genes is expected to be important for individual longevity. However, whether males in natural populations benefit more from MHC heterozygosity than females has rarely been investigated. We investigated this question in a long-term study of free-living Alpine chamois (Rupicapra rupicapra), a polygynous mountain ungulate.ResultsHere we show that male chamois survive significantly (P = 0.022) longer if heterozygous at the MHC class II DRB locus, whereas females do not. Improved survival of males was not a result of heterozygote advantage per se, as background heterozygosity (estimated across twelve microsatellite loci) did not change significantly with age. Furthermore, reproductively active males depleted their body fat reserves earlier than females leading to significantly impaired survival rates in this sex (P < 0.008). This sex-difference was even more pronounced in areas affected by scabies, a severe parasitosis, as reproductively active males were less likely to survive than females. However, we did not find evidence for a survival advantage associated with specific MHC alleles in areas affected by scabies.ConclusionsIncreased MHC class II DRB heterozygosity with age in males, suggests that MHC heterozygous males survive longer than homozygotes. Reproductively active males appear to be less likely to survive than females most likely because of the energetic challenge of the winter rut, accompanied by earlier depletion of their body fat stores, and a generally higher parasite burden. This scenario renders the MHC-mediated immune response more important for males than for females, which implies a relatively stronger selection pressure on MHC genes in males than in females.

A rapid diagnostic technique of Bactrocera cucurbitae and Bactrocera zonata (Diptera: Tephritidae) for quarantine application

Backround The melon fruit fly Bactrocera cucurbitae and the peach fruit fly Bactrocera zonata are serious pests, native to Asia, that have recently invaded Egypt. In Tunisia, no report of these species has yet been made, but pest risk data suggest that both Bactrocera species are likely to establish in other countries of the Mediterranean region. Results A quick method, based on a PCR-RFLP of the mitochondrial COI gene, has been developed to enhance species identification for quarantine purposes. The restriction enzymes DdeI and XmnI were used to digest COI PCR products, enabling a rapid diagnosis of B. cucurbitae and B. zonata and their distinction from Tunisias most devastating fruit pest, Ceratitis capitata. Conclusion The simplicity and relatively low cost of this molecular approach will replace the need to rear immature stages through to adults for identification and will facilitate rapid quarantine decisions providing greater plant protection.

Mitochondrial and nuclear DNA reveals reticulate evolution in hares (Lepus spp., Lagomorpha, Mammalia) from Ethiopia

For hares (Lepus spp., Leporidae, Lagomorpha, Mammalia) from Ethiopia no conclusive molecular phylogenetic data are available. To provide a first molecular phylogenetic model for the Abyssinian Hare (Lepus habessinicus), the Ethiopian Hare (L. fagani), and the Ethiopian Highland Hare (L. starcki) and their evolutionary relationships to hares from Africa, Eurasia, and North America, we phylogenetically analysed mitochondrial ATPase subunit 6 (ATP6; n = 153 / 416bp) and nuclear transferrin (TF; n = 155 / 434bp) sequences of phenotypically determined individuals. For the hares from Ethiopia, genotype composition at twelve microsatellite loci (n = 107) was used to explore both interspecific gene pool separation and levels of current hybridization, as has been observed in some other Lepus species. For phylogenetic analyses ATP6 and TF sequences of Lepus species from South and North Africa (L. capensis, L. saxatilis), the Anatolian peninsula and Europe (L. europaeus, L. timidus) were also produced and additional TF sequences of 18 Lepus species retrieved from GenBank were included as well. Median joining networks, neighbour joining, maximum likelihood analyses, as well as Bayesian inference resulted in similar models of evolution of the three species from Ethiopia for the ATP6 and TF sequences, respectively. The Ethiopian species are, however, not monophyletic, with signatures of contemporary uni- and bidirectional mitochondrial introgression and/ or shared ancestral polymorphism. Lepus habessinicus carries mtDNA distinct from South African L. capensis and North African L. capensis sensu lato; that finding is not in line with earlier suggestions of its conspecificity with L. capensis. Lepus starcki has mtDNA distinct from L. capensis and L. europaeus, which is not in line with earlier suggestions to include it either in L. capensis or L. europaeus. Lepus fagani shares mitochondrial haplotypes with the other two species from Ethiopia, despite its distinct phenotypic and microsatellite differences; moreover, it is not represented by a species-specific mitochondrial haplogroup, suggesting considerable mitochondrial capture by the other species from Ethiopia or species from other parts of Africa. Both mitochondrial and nuclear sequences indicate close phylogenetic relationships among all three Lepus species from Ethiopia, with L. fagani being surprisingly tightly connected to L. habessinicus. TF sequences suggest close evolutionary relationships between the three Ethiopian species and Cape hares from South and North Africa; they further suggest that hares from Ethiopia hold a position ancestral to many Eurasian and North American species.

Genetic diversity of the toll-like receptor 2 (TLR2) in hare (Lepus capensis) populations from Tunisia

Toll-like receptors (TLRs) are a major group of proteins that recognize molecular components of infectious agents, known as pathogen associated molecular patterns (PAMPs). The structure of these genes is similar and characterized by the presence of an ectodomain, a signal transmembrane segment and a highly conserved cytoplasmic domain. The latter domain is homologous to the human interleukin-1 receptor (IL1R) and human IL-18 receptor (IL-18R) and designated TIR domain. The latter domain of the TLR genes was suggested to be very conservative and its evolution is driven by purifying selection. Variability and evolution of the TIR sequences of TLR2 gene were studied in three hare populations from Tunisia with different ecological characteristics (NT-North Tunisia with Mediterranean, CT-Central Tunisia with semi-arid, and ST-South Tunisia with arid climate). Sequencing of a 372bp fragment of TIR2 revealed 25 alleles among 110 hares. Twenty variable nucleotide positions were detected, of which 7 were non-synonymous. The highest variability was observed in CT, with 16 polymorphic positions. In ST, only 4 polymorphic nucleotide positions were detected with all diversity values lower than those recorded for the other two populations. By using several approaches, no positive selection was detected. However, evidence of purifying selection was found at two positions. The logistic models of the most common TIR2 protein variant that we run to examine whether its occurrence was affected by climatic variation independent of the geographic sample location suggested only a longitudinal effect. Finally, the mapping of the non-synonymous mutations to the inferred tertiary protein structure showed that they were all localized in the different loop regions. Among all non-synonymous substitutions, three were suggested to be deleterious as evidenced by PROVEAN analysis. The observed patterns of variability characterized by low genetic diversity in ST might suggest that the TIR region was more affected, than other markers, by genetic drift or/and that these patterns were shaped by different selective pressures under different ecological conditions. Notably, this low diversity was not detected by other (putatively neutral) microsatellite markers analysed in the course of other studies. But low diversity was also found for two MHC class II adaptive immune genes. As expected from functionally important regions, the evolution of the TIR2 domain is mainly driven by purifying selection. However, the occurrence of deleterious non-synonymous substitutions might highlight the flexible evolution of the TIR genes and/or their interactions with other proteins.