Morphological Variation between Life and Death Gastropod Populations in the Nile Delta: A Pollution-Induced Evolution

Abstract

Wetland ecosystems of the Nile Delta face severe threats due to natural climatic changes and anthropogenic activities. Life and death assemblage comparisons can be implemented as a historical record to detect anthropogenic-induced environmental changes in the past few decades. A geometric morphometric approach was applied to quantify the pollution-induced morphological variation between life and death populations of the gastropod Melanoides tuberculata. The results indicated that life populations differ significantly from the death ones, where the first tend to be much smaller, more globular, and with a depressed aperture and whorl section. In addition, the phenetic diversity of the life populations was also decreased, and the allometric growth was shifted. These morphological changes in the life populations are well-known adaptations for reducing the cost of shell maintenance in polluted water. No distinct morphospace was found between life populations from different habitats, suggesting that habitats have no significant role in the current pollution-induced evolution.