**4. Discussion**

The study of the biodiversity talitrid populations in six types of wetlands revealed differences between these types.

The different prospections carried out in wetlands showed globally that the most important species richness was observed in lagoons. Moreover, no individual was collected in hill lakes and dams. Among lagoons studied, the bank of Bizerte lagoon was the most diverse one with eight species. This result was confirmed by several diversity indices performed in the present study.

Our hypothesis concerning the existence of a north/south diversity gradient was confirmed only for wadis. Furthermore, we did not reveal any significant difference concerning the vulnerability of lentic wetlands compared to the lotic type. Concerning Oniscidean group collected from the banks of Tunisian wetlands where many species were found in sympatry with amphipods, a positive correlation between species richness and altitudinal gradient has been highlighted [43]. The same authors showed that species richness differs significantly depending on wetland types or bioclimatic zones.

A total of 2420 amphipods belonging to different species were determined in all prospected wetlands; more than half of the specimens were collected in lagoons (*N* = 1340) with a mean density of 241.5 ind.m−2 observed in the bank of the Bizerte lagoon; *Orchestia mediterranea* showed the most important density in this lagoon. In sebkhas and wadis, the highest densities were recorded, respectively, in sebkha Gargour and El Korsi where *Orchestia mediterranea* and *Platorchestia platensis* were characterized by the highest density, respectively. Studying *Talitrus saltator* and *Britorchestia brito* populations in Zouara beach, Charfi-Cheikhrouha et al. [26] determined a mean density equal to 262.94 ± 85 ind.m−2. These authors showed that the density increased in autumn and winter and reached a maximum in March for *Talitrus saltator*; while for *Britorchestia brito*, this density increased from the middle of March and peaked in October. In Algeria, in the bay of Bou Ismail, *Orchestia montagui* and *Deshayesorchestia deshayesii* reached more than 45,000 ind.m−2 [44]. In the Bou Regreg estuary, *Orchestia mediterranea* showed densities ranging from 3380 (February) to 7000 ind.m−2 (August) [45]. Studying the spatio-temporal distribution of amphipods in different wetlands in Tunisia, Jelassi [46] highlighted that the most important densities were observed during spring.

The diversity of the different talitrid species was related to the presence of different parameters. This relation depends on the wetland type; for example, in lagoons, the sandhopper *Talitrus saltator* was correlated with climatic (temperature, humidity) as well as edaphic factors (organic matter, granulometry, heavy metals of soil) whereas in sebkhas and wadis, this species was correlated only with edaphic factors. These results were also observed for other species. In this context, several studies have investigated the role of environmental factors and have revealed the influence of some factors rather than others. Jelassi et al. [31] have shown that talitrid abundance in the bank of Bizerte lagoon was closely related to air temperature. Bouslama et al. [47] showed that temperature was the important factor influencing the zonation whose augmentation induces the displacement or the migration of *Talitrus saltator* population from the top to the bottom of the beach. This result was similar to that found by Fallaci et al. [48], who indicated that mean zonation of this species was influenced by temperature during its activity period. Other authors such as Colombini et al. [49] confirmed the importance of sediment parameters in the selection of specific distribution area especially for young individuals.

*Talitrus saltator*, abundant species in El Korsi and the estuary of Lebna wadi, as well as *Orchestia stephenseni* and *Deshayesorchestia deshayesii* were positively correlated with temperature and humidity. In the third axis, *Orchestia cavimana* and *Platorchestia platensis* were found positively correlated with organic matter and negatively with lithium and tin content.

**Figure 2.** Canonical correspondence analysis (CCA) performed on the abiotic parameters. Om: *Orchestia montagui*, Og: *Orchestia gammarellus*, Omed: *Orchestia mediterranea*, Os: *Orchestia stephenseni*, Oc: *Orchestia cavimana*, Pp: *Platorchestia platensis*, Ts: *Talitrus saltator*, Dd: *Deshayesorchestia deshayesii*, Hsol: soil humidiy, Tsol: soil temperature, Gra: granulometry, V: vanadium, Cr: chromium, Mn: manganese, Co: cobalt, Ni: nickel, Cu: copper, Zn: zinc, As: arsenic, Cd: cadmium, Sn:

**Bizerte**

**Korsi**

**Estuary O. Lebna**

**Tinja**

**As**

**Pp**

**V Cr**

**Cd**

**Pb**

**Oc**

**Co Ni Cu Zn**

**El Bcherliya**

**Ouafi**

**Fared**

**North of Tunis**

**South of Tunis**

**Face El Boughaz Sidi Ali Mekki**

**Maâmoura**

**Mn**

**Tsol Hsol**

**OM**

**Ghar El Melh** 

**Ts**

**Rb Sr**

**Sn Tl**

**Li**

**-0,8 0 0,8**

**Axis F1 (71.43 %)**

**Os**

**Dd**

**(Axes F1 & F2 : 91.65 %)**

**Bhiret El Biben**

**Og**

**KhnissLakaarit**

**Om**

**Gargou Moknine r**

tin, Tl: thallium, Pb: lead, Li: lithium, Rb: rubidium and Sr: strontium.

**Omed**

The study of the biodiversity talitrid populations in six types of wetlands revealed differences

The different prospections carried out in wetlands showed globally that the most important species richness was observed in lagoons. Moreover, no individual was collected in hill lakes and dams. Among lagoons studied, the bank of Bizerte lagoon was the most diverse one with eight species. This result was confirmed by several diversity indices performed in the present study. Our hypothesis concerning the existence of a north/south diversity gradient was confirmed only for wadis. Furthermore, we did not reveal any significant difference concerning the vulnerability of lentic wetlands compared to the lotic type. Concerning Oniscidean group collected from

**4. Discussion**

**-1,3**

**-0,5**

**Axis F2 (20.23 %)**

**0,3**

112 Selected Studies in Biodiversity

between these types.

Our results showed that the two species *Orchestia cavimana* and *Platorchestia platensis* were correlated with organic matter. Jelassi et al. [32] highlighted that air and soil temperature were the best predictors for *O. stephenseni* abundance that negatively corresponded with the proportion of fine sand fraction and organic matter content of the soil. *O. montagui* and *O. cavimana* abundances corresponded positively with air humidity and the soil lithium and rubidium contents, but negatively with the soil tin content and the proportion of the silt and clay fraction. *D. deshayesii* and *P. platensis* did not exhibit any clear correspondence with station characteristics.

According to Williams [50], the relationship between population movements and trophic preferences does not seem to be a major parameter in the structuring of zonation despite the important mobility of the sandhopper *Talitrus saltator*, which would induce a greater choice of nutrient sources. Studying the biodiversity of amphipods in some coastal lagoons in Tunisia, Jelassi et al. [33] showed that the most important species richness observed in the bank of Bizerte lagoon would be related to the presence of important vegetation in spring as well as the *Cymodocea nodosa* leaf litter and a high percentage of organic matter.

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Attention was also given to biodiversity and biogeography for Oniscidean communities living in sympatry with amphipods in different wetland types prospected in the present study. Khemaissia et al. [43] showed that *Porcellio lamellatus, Tylos europaeus, Armadilloniscus ellipticus, Armadillo officinalis, Porcellio sexfasciatus* and *Chaetophiloscia elongata*, abundant species in the banks of lagoons, were associated with sodium content, pH and temperature of soil. However, other species such as *Armadillidium pelagicum, Armadillidium sulcatum, Armadillidium vulgare, Armadillidium boukornini, Armadillidium tunisiense* and *Porcellio dominici* were abundant around dams and hill reservoirs and were positively associated with elevation. The distribution of *Leptotrichus panzerii* and *Armadillidium granulatum*, in the sebkhas, was correlated with calcium content and humidity of soil.

Through these results, we did not reveal any significant difference regarding the vulnerability of lentic type wetlands compared to the lotic type wetlands. In order to test this hypothesis, the number of this last wetland type (lotic type) should be multiplied.
