Portulaca umbraticola (Portulacaceae), new to the succulent flora of North Africa and an updated key to Tunisian species and forms of the genus

The aquatic biodiversity of springs and groundwater systems of North Africa remains largely unexplored. In an earlier field survey of Tunisian springs, a new gastropod genus, Bullaregia, was discovered as a phylogenetically independent lineage of uncertain position within the family Hydrobiidae. Here, we provide taxonomic and phylogenetic assignments for three newly collected populations of hydrobiids from springs in northern Tunisia based on morphological, anatomical and genetic (mtCOI and 18S) data. Among these and specimens of Bullaregia, major differences were observed in male and female genitalia as well as in mtCOI sequences (divergence 8.0–9.1%). Based on these findings, we describe two new genera and three new species: Belgrandiellopsis chorfensis gen. et sp. nov., Belgrandiellopsis secunda gen. et sp. nov. and Biserta putealis gen. et sp. nov. In all our phylogenetic analyses, these three new species were well resolved as a monophyletic group together with Bullaregia tunisiensis. Unexpectedly, this clade emerged as sister to the European valvatiform genera Corbellaria and Kerkia and not to the recently discovered clade of groundwater, conchologically similar, species living in Bulgaria (Balkan Peninsula). These Tunisian species are each locally endemic and form part of a newly discovered clade which in future systematic studies could eventually be identified as a distinct hydrobiid subfamily.

The species richness of the aquatic (non-marine) gastropod family Hydrobiidae Stimpson, 1865 reaches its peak in the European region partly because other areas, such as North Africa, remain to be extensively surveyed. Most of the hydrobiid species described in North Africa have been ascribed to the subfamilies Pseudamnicolinae, Hydrobiinae and the genus Mercuria. Little is known about the presence of other hydrobiid subfamilies. This study examines several specimens of gastropods collected from two springs in Tunisia. Based on a comprehensive literature review and rigorous anatomical and molecular comparisons with known species from North Africa, Europe and Asia Minor of similar morphology, we here describe a new genus, Bullaregia gen. nov., and new species Bullaregia tunisiensis gen. et sp. nov. Although the shell shape of this Tunisian species resembles that of European hydrobiid genera such as Belgrandiella, it differs in other anatomical structures (i.e., penis with a glandular strap-like lobe, and two seminal receptacles, SR1 pedunculate, SR2 sessile and less developed). Using maximum likelihood and Bayesian approaches, phylogenetic relationships inferred from mtCOI sequences point to an independent evolutionary lineage for this new taxon outside Belgrandiella and other known hydrobiid subfamilies.

Polygonum is the largest genus of Polygonaceae and 5 species are reported in Tunisia. In order to characterized flower, seed, and fruit development in Polygonum, flower and fruit of Polygonium equisetiforme (var. graecum and peyerinhoffi), P. aviculare and P. maritimum, collected from Tunisia, were examined. Flowers are composed of five oblong tepals. P. equisetiforme and P. aviculare have whitish-pink distylous flowers with dimorphism of style, filament and anther height, pollen diameter and stigma size. In contrast, P. maritimum shows white homostylous flowers. The floral vasculature showed that the tepals are inserted in one whorl and their traces arise independently in 3+2 manner. The eight stamens are arranged in a 5+3 manner and the staminal bundles arise independently in the two whorls. The epidermis and endothecium cells width were higher in P. maritimum and the lowest endothecium width was observed in P. aviculare. Polygonum aviculare and P. equisetiforme showed circular pollen with shallow colpi and trilobite pollen shape with deep colpi, while P. maritimum rarely showed shallow colpi. The ovule is anatropous with basal placentation in P. equisetiforme and P. aviculare and apical placentation in P. maritimum. The young seed coat was formed by an endotesta with thick-walled cells, a mesotesta and exotesta with thin-walled cells and a tegmen composed of radially elongated cells. The fruits of the studied species are trigonous with ovate-lanceolate shape. In P. aviculare, the exocarp is thicker compared to the two other species, in P. equisetiforme, the mature exocarp consists of smaller rectangular cells with narrow cavities, and in P. maritimum showed a thinner exocarpIn conclusion, P. equisetiforme and P. aviculare are a typically distylous species from the morphological point of view and we discussed the significance of heterostyly in Polygonaceae. From this first morpho-anatomical study of Polygonum species in North Africa, we can conclude mainly that there is no significant difference between P. equisetiforme var. graecum and var. peyerinhoffi supporting a taxonomic grouping of these two varieties.

Enzyme electrophoresis on horizontal starch gel was carried out on 356 barbel individuals. The sampling comprised 278 individuals of the species Barbus callensis from 10 rivers in Tunisia. The other individuals belonged to reference species (outgroups) from France and Morocco. An ecological study was also carried out on Tunisian rivers. The results show a clear differentiation of the two samples from northwestern Tunisia, which was only partly correlated with ecological characteristics of the rivers they inhabit. There is no genetic cline, but rather a discontinuity between populations in the northwestern‐most watershed and all the other Tunisian populations. This differentiation probably has a paleohistoric origin not only related to adaptation to ecological conditions but also to difficulties in colonizing the watersheds. The results do not indicate clearly a colonization direction for the genus Barbus in North Africa. Analysis of the Algerian populations would appear to be indispensable. Lastly, in contrast with the usual taxonomy, Morocco and Tunisia are populated by two closely related species, but B. callensis should remain the name of the Tunisian species, which was the first to be described in the small El Kebir basin, a river that flows from Tunisia to Algeria.