George Morgan Davis was a preeminent American malacologist of the latter twentieth century. Seated in Henry Pilsbry's chair at the Academy of Natural Sciences in Philadelphia, his keen eye for morphological detail, matched only by his extraordinary ability to transmit rigorous scientific observation onto the journal page in word, data table, numerical analysis, and delicately stippled anatomical illustration, exceeded even that of his predecessor Henry Pilsbry. From a firm foundation in the classical school of descriptive biology, Davis became the first American malacologist to apply molecular techniques to address systematic questions in the phylum Mollusca, pioneering immunological, protein electrophoretic, and sequencing technologies throughout his long career. The influence that he wielded to shape and mold our discipline during his 40-year editorship of this journal was exceeded only by Henry Pilsbry's 70-year editorship of The Nautilus. Here we review Davis' distinguished career, his 200 publications, the 46 taxa that he named, and the 11 taxa named in his honor.
Davisassiminea, a new genus of the Assimineidae, is proposed for Rissoa (Cingula) capensis G. B. Sowerby III, 1892 from tidal flats of southeastern South Africa. The new genus is unique for the family in the morphology of the radula and reproductive system, and the absence of distinct omniphoric grooves. A congeneric species, Assiminea globulus Connolly, 1939, was also examined anatomically. Our molecular phylogenetic analysis using two mitochondrial genes and one nuclear gene confirms that these taxa are members of the subfamily Assimineinae. Based on molecular and radular evidence, Microsetia durbanensis Tomlin, 1916 is also a member of the new genus. Uniquely for assimineids, these species live on seagrass in marine habitats.
The genus Potamolithus Pilsbry, 1896 represents a group of freshwater gastropods endemic to southern South America, with 48 described species, and constitutes the sole representative of the family Tateidae in the region. Historically, the taxonomy of the genus was based on shell morphology; however, subsequent studies incorporating anatomical and molecular data have highlighted the limitations in species identification based solely on shell features. Since 2010, the team at the Museo de La Plata has conducted comprehensive studies in the malacological province of the Uruguay River, a region with high molluscan diversity and significant relevance for aquatic biodiversity conservation in Argentina. In this context, Potamolithus davisi n. sp. is described through the analysis of morphological and anatomical characters, as well as mitochondrial COI gene sequencing. The results highlight the need for integrative taxonomic approaches and underscore the importance of the Uruguay River as a key refuge for regional malacological biodiversity. This study contributes to the systematic knowledge and conservation of Potamolithus in South American freshwater ecosystems.
Partulidae, a Pacific Island tree snail family of extreme conservation concern, has been the subject of multiple taxonomic revisions in recent years. In addition to numerous changes at the species level, one new genus ( (Sphendone Slapcinsky & Kraus, 2016) has been proposed and two preexisting taxa ( (Rennellia Clench, 1941 and Palaopartula Pilsbry, 1909) have been elevated to genus level, with all three genera based primarily on qualitative appraisals of traditional morphological (shell and soft parts) characters. The limited phylogenetic analyses inclusive of these three genera provide poor-to-ambivalent support for their respective phylogenetic distinctiveness, in part due to the paucity of available genetic markers, but also due to rooting issues caused by a lack of Partulidae sister lineages. We aimed to address both deficiencies by performing double digested Restriction Associated DNA (ddRADseq) phylogenomic analyses that incorporated putative Partulidae sister lineages in addition to type species of the three new, and three pre-existing ( (Partula Ferussac, 1821; Samoana Pilsbry, 1909; and Eua Pilsbry & C. M. Cooke, 1934), Partulidae genera, along with representative congeners spanning their respective ranges. Among the six pupilloidean outgroup families investigated, our results tentatively placed Valloniidae and Gastrocoptidae as sisters to Partulidae and recovered three robust ingroup clades: ( (Eua ( (Samoana (Samoana, Partula)). Rennellia was firmly nested within the Partula clade (sister to Marianas species) and a paraphyletic Palaopartula/Sphendone n. gen. within the Samoana clade [sister to the Marianas species Samoana fragilis (Ferussac, 1821)]. Because reciprocal monophyly is widely accepted as a minimum prerequisite of generic status, these data compelled us to return to the traditional three-genus model for Partulidae. That redesignation was strongly corroborated by molecular clock divergence time estimates and by the presence of phylogenetic gaps, but less so by crown group definitions or the uniqueness of adaptive zones. It significantly expanded our conception of the genus Samoana in terms of its evolutionary history, species composition and ecological diversity. Our phylogenomic results also provided new insights into the enigmatic biogeography of this family, locating the origins of all three genera within neighboring archipelagos and identifying for the first time a sister species to the fabled Society Islands Partula radiation.
The Hydrobiinae is a monophyletic taxon with similar to 16 recognized species. They are distributed throughout the eastern and western North Atlantic and adjacent seas, with a disjunct occurrence along the South African coast. Although some species and genera are widely distributed, others are endemic. The reasons for these contrasting biogeographic patterns are largely unknown, as is the historical biogeography of most hydrobiine taxa. Therefore, the overall objective of this study is to unravel the biogeographic relationships of the subfamily Hydrobiinae. Specifically, a multilocus phylogenetic reconstruction and a species-level ancestral range estimation were performed. In addition, the South African genus Davishydrobia Wilke, gen. nov., was described. The multilocus phylogenetic analyses revealed eight distinct clades at the genus and 16 putative clades at the species level within the subfamily Hydrobiinae. Estimates of the ancestral range suggest that the (Proto-)Mediterranean region is the most likely area of origin of the Hydrobiinae. From there, members of the subfamily presumably colonized coastal areas of the eastern and western North Atlantic, the Arctic Ocean, and South Africa, as well as continental parts of central Asia.
