Supplementary Material for Quantitative and qualitative statistical analyses of the shell and the genital traits of the doorsnail genus Montenegrina O. Boettger, 1877 (Gastropoda: Clausiliidae)

The importance of genital morphology for alpha- and supraspecific taxonomy of pulmonate land snails has been known since the 19th century. Despite that, the genital anatomy of the family Clausiliidae has been considered of low discriminatory importance at the species level, although it has great potential for discriminating genera. No statistical analyses of fundamental aspects of genital morphology of clausiliids, such as measurements, size ranges, mean values, standard deviation, and trait categorization, are yet found in the literature. Moreover, no data on statistical correlations among the various morphological parts (genitalia and shell) have been reported to date. In the present study we investigate the clausiliid genus Montenegrina as a model for such morphometric analyses. Measurements show a high degree of variability and large overlaps among the Montenegrina taxa. Correlation tests show positive correlations among some shell chracters, while correlations among genital characters prove to be generally weaker. Additionally, we compare quantitative (morphometric measurements) and qualitative (categorization of traits) data with principal component analyses (PCA) to test if genitalia and shell morphological features correspond to the phylogeny based on published previously mitochondrial DNA sequences. The morphometric analyses of shell and genital characters show that, although specimens of the same taxon mostly cluster together, many clades overlap in the PCA scatter plots and/or form intermingled clusters in the neighbour-joining (NJ) trees. Finally, we ask if the taxa studied show character displacement. Among the 4 syntopic pairs of taxa that exist in the genus Montenegrina, 3 show a morphological Euclidean distance well above the average for the genus, although the discriminant power is notably weak. Assumptions on how ecological factors should result in differences of shell and/or genital morphology—thus, ecological character displacement (ECD)—remain speculative. Our findings are compatible with both the assumption of reproductive character displacement (RCD) as well as the non-adaptive radiation hypothesis raised by earlier work on this group. 

This repository contains the Supplementary Material for this article.