Morphological and genetic differentiation of Eremina desertorum (Gastropoda, Pulmonata, Helicidae) in Egypt

Abstract

2016). Morphological and genetic differentiation of Eremina desertorum (Gastropoda, Pulmonata, Helicidae) in Egypt. -Zoologica Scripta, 45, 48-61.To understand the processes that result in morphological and genetic diversity, we studied the differentiation of the land snails Eremina d. desertorum and Eremina desertorum irregularis in the deserts of northern Egypt. These two taxa are differentiated with regard to shell size and shape and are separated by a narrow hybrid zone west of Alexandria. The lack of differences in the genitalia and the lack of reciprocal monophyly of the mitochondrial haplotypes of E. d. desertorum and E. desertorum irregularis support their classification as subspecies rather than distinct species. Low genetic distances indicate that the differentiation is probably less than half a million years old. The genetic data indicate a population expansion in agreement with other evidence that the Nile region in northern Egypt was more humid well into historical times than today. Shell size and shape are correlated with a climatic gradient from cooler and more humid conditions along the Mediterranean coast to arid and hot conditions in the interior. The decrease of body size with decreasing precipitation and increasing temperature might be explained by limited time for food intake in the more arid regions. The shape differences between the taxa are partly an indirect consequence of selection for body size, but are also directly affected by selection for reduction of aperture size.

Morphological and Anatomical Characteristics of the Two Taxa Eremina desertorum desertorum (Forskål, 1775) and Eremina desertorum irregularis (Férussac, 1821) (Gastropoda: Helicidae) of the Northern Deserts of Egypt

“…The mitochondrial haplotypes of the two taxa, which are different local subspecies, support their classification as subspecies rather than distinct species regardless to the size and shape of their shells (Ali et al, 2016). The authors mentioned as well that the genitalia of some specimens of six populations of E. d. desertorum and other specimens of 14 populations of E. d. irregularis were analyzed according to some measurements genital organs and according to this analysis shows that a rudimentary flagellum was found in 16.1% of the studied E. d. desertorum individuals and in 5.5% of the studied E. desertorum irregularis individuals.…”

“…8 and 9) The genital system is similar to this one had been described before of Eremina desertorum desertorum. There is a lack of differences in the genitalia in the two species E. d. desertorum and E. d. irregularis, which small difference but that strong distinguish between them and the genital variation had been described in Ali et al 2016. The authors mentioned that the genitalia of 141 (more than 100) individuals from six populations of E. d. desertorum and 14 populations of E. d. irregularis were analyzed according to some measurements to some organs such as the length of the penis, the distal epiphallus, the proximal epiphallus, the vagina distal of the insertion of mucus glands, the vagina proximal of the insertion of the mucus glands, the dart sac and the oviduct.…”

“…The shell is usually smaller and more depressed comparing to E. desertorum irregularis (Biggs, 1959;Ali et al, 2016).…”

“…These two taxa are considered different local subspecies with regard to the shell size and shape in addition to the mitochondrial haplotypes that support their classification as subspecies rather than distinct species (Ali et al, 2016).…”

Genetic analysis of Cryptozona siamensis (Stylommatophora, Ariophantidae) populations in Thailand using the mitochondrial 16S rRNA and COI sequences

“…In the last few years, DNA sequencing data has been used to study and clarify the evolution of morphological characteristics of ambiguous organisms [ 15 – 18 ] while genetic studies of land snails using DNA sequence data could be valuable for their identification [ 19 – 21 ]. The most commonly used genes for genetic analysis in land snails are the mitochondrial cytochrome c oxidase subunit I (COI) and 16S rRNA genes [ 20 , 22 – 24 ].…”