Plant diversity in different bioclimatic zones in Tunisia

An improved trend vegetation analysis for non-stationary NDVI time series based on wavelet transform

The aim of this paper is to improve trend analysis for non-stationary Normalized Difference Vegetation Index (NDVI) time series (TS) over different areas in Tunisia based on the wavelet transform (WT) multi-resolution analysis (MRA-WT), statistical test, and meteorological data. The MRA-WT was applied in order to decompose the TS into different components. However, the most challenge for TS analysis using MRA-WT laid in the selection of two optimum parameters: the level of decomposition and mother wavelet (MW). In this work, both factors were investigated. Firstly, the level of decomposition was calculated for 18 different MWs, and secondly the energy to Shannon entropy ratio criterion was investigated to choose the most suitable MW. The Mann-Kendall test (MK) and Sen's slope were applied to the last approximation component in order to analyze long-term vegetation changes. Finally, the influence of meteorological data for trend was analyzed. The results were first computed for different sites in Tunisia using MODIS NDVI TS from 2001 to 2017. The obtained results proved the importance of MW selection. Level 5 was considered for the TS as the best level of decomposition for long-term vegetation changes. The Daubechies and Symlets MWs (db9 and sym4) showed the highest energy to entropy ratio for three selected vegetation canopies. A combination of the two MW was proposed to derive a trend vegetation analysis at image level. A degradation in the forest area and a few increases in cropland and vegetation area were presented.

Increasing aridity shapes beta diversity and the network dynamics of the belowground fungal microbiome associated with Opuntia ficus-indica

AIMS

The effects of aridity on soil and water-use efficient (WUE) crop species are relatively well known. However, the understanding of its impacts on the dynamics of below-ground microorganisms associated with plant roots is less well understood.

METHODS

To investigate the influence of increasing aridity on the dynamics of the fungal communities, samples from the root endosphere and rhizosphere associated with the prickly pear cactus trees (Opuntia ficus-indica) growing along the aridity gradient were collected and the internal transcribed spacer (ITS) were sequenced. The diversity and network analyses of fungal taxa were determined along with standard measurements of soil parameters.

RESULTS

We found that (i) the fungal community exhibited similar alpha diversity and shared a set of core taxa within the rhizosphere and endosphere, but there was significant beta diversity differences; (ii) the relative abundance of major phyla was higher in the rhizosphere than in the endosphere; (iii) arbuscular endomycorrhizal colonization was highest in the humid climate and decreased under lower-arid, and was negatively correlated with increased concentration of Ca²⁺ in the soil; (iv) increased aridity correlated with increased connectivity of the soil microbial-root fungal networks in the arid soils, producing a highly cohesive network in the upper-arid area; and (v) distinct fungal hubs sculpt the fungal microbiome network structure in the rhizosphere and endosphere within each bioclimatic zone.

CONCLUSIONS

Our findings highlight the importance of gradient analysis-based correlation network as a powerful approach to understand changes in the diversity, the dynamics, and the structure of fungal communities associated with the rhizosphere-endosphere interaction and led to the identification of microbes at each bioclimatic zone that are potentially involved in promoting the survival, protection, and growth of Opuntia trees. The variability of fungal hubs composition depending on plant compartment and bioclimatic zone will give key implications for the application of rhizospheric fungi and endophytes as microbial inoculants in agriculture, as well as in the conservation and restoration of cacti plants in arid and semi-arid lands against the backdrop of climate change. Overall, this study will enhance our understanding of the microbiomes'dynamic of CAM plants in nature.

Phenology and phylogeny of Hyalomma spp. ticks infesting one-humped camels (Camelus dromedarius) in the Tunisian Saharan bioclimatic zone

In this study, we report the results of a survey of Hyalomma ticks infesting one-humped camels in southern Tunisia. Examinations were conducted every second or third month on 406 camels in Tataouine district from April 2018 to October 2019. A total of 1902 ticks belonging to the genus Hyalomma were collected. The ticks were identified as adult H. impeltatum (41.1%; n = 782), H. dromedarii (32.9%; n = 626), H. excavatum (25.9%; n = 493), and H. marginatum for a single specimen. Although the camels were infested by ticks throughout the year, the highest overall infestation prevalence was observed in April 2018 (p < 0.01). The overall infestation intensity varied between 2.7 and 7.4 ticks/animal. There were no statistically significant differences in tick infestation prevalence based on age categories of the camels, and the overall infestation prevalence was between 82.7% and 97.4%. Female camels were significantly more infested with ticks (88.3%) than males (65.5%) (p < 0.01). The infestation prevalence of camels varied significantly according to the region where sampling took place (p < 0.01), but no correlations were found with abiotic factors. The preferred attachment sites for adult Hyalomma ticks were the sternum (38.3%; n = 729/1902), around the anus (36.2%; n = 689/1902), udder (18.4%; n = 350/1902), and inner thigh (6.9%; n = 132/1902). Morphological classification of ticks was corroborated by sequencing the cytochrome c oxidase I (Cox1) and 16S rDNA genes, and these sequences were also used to infer phylogenetic relationships. A single H. dromedarii seemed to be a natural hybrid with H. rufipes. More attention should be devoted by the veterinary services to the infestation of camels by ticks.

New Isoflavones with Antioxidant Activity Isolated from Cornulaca monacantha

In the course of phytochemical and chemotaxonomical investigations of Cornulaca monacantha (Amaranthaceae), two new isoflavones, 3-(2-hydroxyphenyl)-5,7-dimethoxy-6-(methoxymethyl)-4H-1-benzopyran-4-one (1) and 7-hydroxy-3-(4-hydroxyphenyl)-5-methoxy-6-(methoxymethyl)-4H-1-benzopyran-4-one (2) were isolated from the fresh aerial parts of C. monacantha among with three known compounds named vanillic acid (3), N-cis-feruloyltyramine (4) and N-trans-feruloyltyramine (5). Their structures were elucidated by means of spectroscopic methods including one- and two-dimensional NMR and HR-ESI-MS techniques. The isolated compounds exhibited interesting antioxidant activity determined by DPPH, ABTS and TAC tests.

Water Is Needed to Exist: Habitat Preferences of Tiger Beetles (Coleoptera: Cicindelidae) in a Desert Country

Simple Summary

Many species of tiger beetles are habitat specialists, which make them useful as bioindicators of the status and changes in the quality of the environment. Their diversity and community structure in particular habitats can point to the stability of habitat. We studied six different macro and microhabitat factors that influence the habitat preferences of four Cicindelidae species occurring in different Tunisian desert areas. This is the one of only a few such studies in Africa. The results clearly show high habitat specialization of most studied taxa, as well as importance of water reservoirs in species distribution in the Sahara Desert.

Abstract

Tiger beetles are a group of predatory insects occurring mainly in diverse sandy areas, with particular species often characterised by narrow habitat preferences, which makes them both very important bioindicators for determining patterns of biodiversity and a flagship group for nature conservation. However, the precise roles of particular habitat parameters in the distribution of these beetles in desert areas are almost unknown. Habitat preferences for four tiger beetles species were analysed in Tunisia. Fifty samples from a major part of the country were collected, for which climate data, macrohabitat types. and soil parameters (soil humidity, salinity, pH, and structure) were studied. Here we show that most studied Cicindelidae were characterised by unique habitat preferences and did not co-occur with other ones, including two taxa found as habitat specialists, occurring in only one type of macrohabitat. Two other species were noted as more eurythopic and occupied 2–3 macrohabitat types, with Lophyra flexuosa as the most ubiquitous species not related to the measured parameters. The presence of a source of water (understood as a part of the habitat type, such as river banks and oases, or high soil humidity) was found as the most important factor in the distribution of the studied tiger beetle species. The present study is the first one focused on habitat preferences and habitat specialization of Cicindelidae fauna of Maghreb, and one of only a few in Africa.

Pearl millet populations characterized by Fusarium prevalence, morphological traits, phenolic content, and antioxidant potential

BACKGROUND

Pearl millet (Pennisetum glaucum L.) has become increasingly attractive due to its health benefits. It is grown as food for human consumption and fodder for livestock in Africa and Asia. This study focused on five pearl millet populations from different agro-ecological zones from Tunisia, and on characterization by morphological traits, total phenolic and flavonoid content, antioxidant activity, and occurrence of Fusarium.

RESULTS

Analysis of variance revealed highly significant differences between populations for the quantitative traits. The highest grain weights occurred in the pearl millet cultivated in Zaafrana and Gergis of Tunisia. Early flowering and early maturing populations cultivated in the center (Zaafrana, Rejiche) and south (Gergis) of Tunisia tended to have a higher grain yield. The Zaafrana population showed the highest value of green fodder potentiel (number and weight of leaves/cultivar and the weight of tillers and total plant/cultivar) followed by Gergis and Rejiche. The Kelibia population showed the highest total phenolic and flavonoid content. Rejiche exhibited the greatest antioxidant activity. Trans-cinnamic, protocatechuic, and hydroxybenzoic acids were the major phenolic compounds in all the extracts. Three Fusarium species were identified in Tunisian pearl millet populations based on morphologic and molecular characterization. Fusarium graminearum and Fusarium culmorum occurred most frequently. The average incidence of the three Fusarium species was relatively low (<5%) in all populations. The lowest infection rate (0.1%) was recorded in the samples from Zaafrana.

CONCLUSION

Chemometric analysis confirmed the usefulness of the above traits for discrimination of pearl millet populations, where a considerable variation according to geographical origin and bioclimatic conditions was observed. © 2020 Society of Chemical Industry.

Antimicrobial and Light-Enhanced Antimicrobial Activities, Cytotoxicity and Chemical Variability of All Tunisian Eryngium Species

This study was performed on all Eryngium species growing in Tunisia in order to evaluate their intra and interspecies variabilities and to investigate their biological activities. These species are used in traditional medicine, and literature about the phytochemical investigations of most of them is scarce. Antimicrobial and light-enhanced activities were tested against multiresistant microorganisms and extended spectrum beta-lactamase producing bacteria (ESBL). All studied species showed antimicrobial effect with several MIC values lower than 70 μg/ml. Tested Eryngium species have proven to be a promising source of photoactive compounds, while light-enhanced activity offers an alternative for the inactivation of pathogenic microorganisms which is currently subjected to a great interest. This is the first report of this activity in genus Eryngium. A significant improvement of antimicrobial activity with UV irradiation was observed, mainly for E. dichotomum, E. ilicifolium and E. triquetrum. Cytotoxicity, studied for the first time for the most species, was evaluated against cancer (J774) and non-cancer (WI38) human cell lines. Chemical composition of volatile compounds presented in the most active crude extracts (petroleum ether extracts) of the aerial parts was investigated using GC/MS analysis and was submitted to statistical analyses. It revealed their high content of bioactive phytochemicals, particularly oxygenated sesquiterpenes like spathulenol, ledol and α-bisabolol but also hydrocarbon sesquiterpenes such as β-bisabolene and copaene, as well as polyacetylene derivatives such as falcarinol. Statistical analyses permitted to evaluate the interrelations between all Tunisian Eryngium species.

Polyphenolic profile, antibacterial activity and brine shrimp toxicity of leaf extracts from six Tunisian spontaneous species

The aim of this study was to investigate the polyphenolic profile and biological properties of leaves acetonic extracts from six Tunisian spontaneous plants of Marrubium vulgare L., Rhus tripartita (Ucria) D.C., Hernaria fontanesii J. Gay subsp. fontanesii, Ziziphus lotus L., Plantago ovata Forsk., Thymelaea hirsuta (L.) Endl. Bioassay-guided and HPLC-PDA-ESI-MS procedures demonstrated that R. tripartita contained the highest amount of phenolic compounds (1475.1 µg/g), followed by Z. lotus (1087.8 µg/g) and P. ovata (1027.6 µg/g). Interestingly, in R. tripartita myricetin-3-O-galactoside turned out to be the most abundant one. The plant extracts showed antimicrobial efficacy against Listeria monocytogenes, Staphylococcus aureus and S. epidermidis including methicillin resistant strains; no activity was detected against Gram-negative bacteria. R. tripartita revealed the best MIC and MBC values and caused significant decrease of S. aureus biofilm. Both R. tripartita and Z. lotus did not display any toxicity against Artemia salina Leach (LC₅₀ > 1000 μg/mL).

Positive selection and climatic effects on MHC class II gene diversity in hares (Lepus capensis) from a steep ecological gradient

In natural populations, allelic diversity of the major histocompatibility complex (MHC) is commonly interpreted as resulting from positive selection in varying spatiotemporal pathogenic landscapes. Composite pathogenic landscape data are, however, rarely available. We studied the spatial distribution of allelic diversity at two MHC class II loci (DQA, DQB) in hares, Lepus capensis, along a steep ecological gradient in North Africa and tested the role of climatic parameters for the spatial distribution of DQA and DQB proteins. Climatic parameters were considered to reflect to some extent pathogenic landscape variation. We investigated historical and contemporary forces that have shaped the variability at both genes, and tested for differential selective pressure across the ecological gradient by comparing allelic variation at MHC and neutral loci. We found positive selection on both MHC loci and significantly decreasing diversity from North to South Tunisia. Our multinomial linear models revealed significant effects of geographical positions that were correlated with mean annual temperature and precipitation on the occurrence of protein variants, but no effects of co-occurring DQA or DQB proteins, respectively. Diversifying selection, recombination, adaptation to local pathogenic landscapes (supposedly reflected by climate parameters) and neutral demographic processes have shaped the observed MHC diversity and differentiation patterns.

Conservation priorities for endangered coastal North African Pennisetum glaucum L. landrace populations as inferred from phylogenetic considerations and population structure analysis

The increasing anthropologic pressure and the modernization of agriculture have led to a forsaking of pearl millet traditional cultivars, inducing a progressive loss of the genetic variability encompassed in this locally adapted germplasm. Imperatively, national efforts based on robust data gleaned from genetic surveys have to be undertaken in order to set up suitable conservation priorities. In this study, in addition to the assessment of the genetic diversity and population structure among and within a set of seven pearl millet landrace populations from coastal North Africa, demographic and phylogenetic data, conservation priority scores were calculated according to Vane-Wright et al. (1991). To date, genetic diversity of pearl millet in North Africa is still poorly documented. The present survey reports for the first time the use of highly informative nSSR markers (PIC = 0.74) on Pennisetum glaucum landraces representative of the Mediterranean coastline of North Africa. A high level of genetic diversity was obtained within the investigated landraces (H_e = 0.80) at the population level. F_ST, AFC-3D, and Bayesian clustering underlined significant differentiation and an apparent genetic structure, according to geographical origin. Phylogenetic considerations integrated with demographic and genetic information enabled conclusive inferences of highly prioritized populations for conservation. Populations Haouaria, Hammem Laghzez, Mahdia, and Medenine, representatives of the main pearl millet growing areas in Tunisia and cultivated in the North African littoral, should be strongly recommended for an ex situ conservation program. Dynamic on-farm conservation method is also required as it allows the local landraces to evolve in different environments, while maintaining their adaptation potentials.

Chemical composition and antioxidant activity of the volatile fraction extracted from air-dried fruits of Tunisian Eryngium maritimum L. ecotypes

BACKGROUND

Eryngium maritimum L., also known as 'sea holly', is a typical dune plant species belonging to the Apiaceae family and commonly used in Tunisia for therapeutic purposes in folk medicine. In the present study, the chemical composition and antioxidant activity of the volatile fraction extracted from air-dried fruits of five Tunisian E. maritimum ecotypes were determined.

RESULTS

The total volatile amount ranged from 0.31% to 0.93% (w d.w.^-1 ). Sixty-six volatile components were identified by means of GC-MS and accounted for 77.05-86.65% of the total extracted volatile oil. The majority of the identified metabolites were hydrocarbon sesquiterpenes and oxygenated sesquiterpenes, amounting on average to 46.69% and 30.01% of total volatiles, respectively. The principal individual components were germacrene D (13.62-31.71%), 15-hydroxy-α-muurolene (12.04-18.58%), and germacrene B (6.77-15.04%). Significant differences were noticed among E. maritimum populations. The volatile profile of E. maritimum fruits was consistently different from those of the aerial parts and roots of plants of the same species reported in previous investigations. Average radical scavenging capacity of the volatile fraction, as determined by DPPH and ABTS tests, was twice higher than that of the Trolox control.

CONCLUSION

This study characterised for the first time the fruits of E. maritimum for the composition and radical-scavenging capacity of their volatile fraction. The growth location confirmed as a pivotal factor in influencing the volatile profile of the fruits. © 2017 Society of Chemical Industry.

A review of Tunisian medicinal plants with anticancer activity

Cancer is a major public health problem in the world. The use of the medicinal plants in cancer prevention and management is frequent in Africa, especially in Tunisia, and it is transmitted from generation to generation within cultures. Many previous studies showed that a wide range of Tunisian medicinal plants exerted cytotoxic and anticancer activity. A comprehensive review was conducted to collect information from scientific journal articles, including indigenous knowledge researches, about Tunisian medicinal plants used for the prevention and management of cancer. The aim of this review article is to provide the reader with information concerning the importance of Tunisian medicinal plants in the prevention and management of cancer and to open the door for the health professionals and scientists working in the field of pharmacology and therapeutics to produce new drug formulations to treat different types of cancer.