Contribution for the knowledge on microgastropods of the clades Heterobranchia and Mesoneura: taxonomic and macroevolutionary aspects

Abstract

This study aims to contribute to the understanding of micromollusks of the Heterobranchia clade, addressing their biodiversity, taxonomy, and the macroevolutionary aspects of miniaturization. The dissertation is organized into three chapters, each addressing different aspects of the subject. In the first chapter, we conducted an assessment of the time and mode of miniaturization evolution in marine heterobranch molusks, using molecular methods and genetic databases. The reconstruction analysis of the ancestral state reveals that miniaturization originated as a characteristic of the Heterobranchia ancestor during the Middle Devonian, followed by a dynamic evolution of size at the genus and species levels. In the second chapter, we aimed to provide a critical review of the species concepts adopted for basal heterobranch microgastropods, along with the methodologies associated with each concept (phylogenetic and morphological). It was found that predominantly morphological species concepts were adopted (98.06%), with varied operational criteria. Shell morphology was the main factor for 84.55% of species delimitation, while soft part anatomy and external morphology were also employed, individually or in combination. The exclusive association of the phylogenetic species concept with the criterion of monophyly reveals potential impacts on the current state of knowledge regarding the phylogeny and evolution of this group. The third chapter consists of a list of terrestrial and freshwater microgastropod species deposited in the Prof. Maury Pinto de Oliveira collection, donated by the Romanian malacologist Alexandru Grossu. This list results from a collection review, involving data compilation, specimen reconditioning, image acquisition through Scanning Electron Microscopy, and taxonomic updating through cross-verification of species taxonomic assignments. Additionally, an analysis of the representativity of the analyzed species in larger collections worldwide was conducted by researching records of these species in Romania through biological collections databases. This study not only expands our knowledge of micromollusks in the Heterobranchia clade but also emphasizes the importance of multidisciplinary approaches to advance the understanding of the evolution and diversity of these organisms.