Shell color polymorphism in marine gastropods

Abstract

Marine gastropods are characterized by an incredible variation in shell color. In this review, we aim to introduce researchers to previous studies of shell color polymorphism in this group of animals, trying to provide an overview of the topic and highlighting some potential avenues for future research. For this, we tackle the different aspects of shell color polymorphism in marine gastropods: its biochemical and genetic basis, its patterns of spatial and temporal distribution, as well as its potential evolutionary causes. In particular, we put special emphasis on the evolutionary studies that have been conducted so far to reveal the evolutionary mechanisms responsible for the maintenance of shell color polymorphism in this group of animals, as it constitutes the least addressed aspect in existing literature reviews. Several general conclusions can be drawn from our review: First, natural selection is commonly involved in the maintenance of gastropod color polymorphism; second, although the contribution of neutral forces (gene flow‐genetic drift equilibrium) to shell color polymorphism maintenance do not seem to be particularly important, it has rarely been studied systematically; third, a relationship between shell color polymorphism and mode of larval development (related to dispersal capability) may exist. As for future studies, we suggest that a combination of both classical laboratory crossing experiments and ‐ Omics approaches may yield interesting results on the molecular basis of color polymorphism. We believe that understanding the various causes of shell color polymorphism in marine gastropods is of great importance not only to understand how biodiversity works, but also for protecting such biodiversity, as knowledge of its evolutionary causes may help implement conservation measures in those species or ecosystems that are threatened.

A decade of progress in marine evolutionary biology

“…However, color patterns may arise in diverse evolutionary ways in different taxa and are not necessarily always associated with speciation (e.g., Andrade et al, 2019 ). Gefaell et al ( 2022 ) reviewed shell color polymorphism in marine gastropods, providing a summary of the patterns of color diversity in gastropod species, the underlying biochemical and genetic mechanisms in this trait, and the role of different evolutionary mechanisms in generating and preserving color polymorphism in gastropod taxa. Based on 61 studies, the authors conclude that natural selection is typically involved in the maintenance of shell color polymorphism in marine gastropods, although the roles of drift and gene flow were rarely considered or explicitly tested for in the reviewed articles.…”

“…Herein, these processes are addressed in diverse empirical model systems ranging from diatoms to mollusks and fish (Green et al, 2022 ; Le Moan et al, 2022 ; Sefbom et al, 2022 ; Zhang et al, 2022 ), as well as in silico in two theoretical modeling studies (Eriksson et al, 2022 ; Marshall & Connallon, 2022 ). The link between genotype and phenotype is also the focus of several empirical studies here (Gefaell et al, 2022 ; Stenger et al, 2022 ; Walker et al, 2022 ), as is the seascape genomics of a wide range of taxa (Delaval, Bendall, et al, 2022 ; Delaval, Frost, et al, 2022 ; Fitz et al, 2022 ; Lapègue et al, 2022 ; Matias et al, 2022 ; Palumbi et al, 2022 ; Pampoulie et al, 2022 ), which has important implications for management of marine resources. Finally, the breadth of phylogenetic diversity and evolutionary history in the oceans is the topic of several articles focusing on the larval development of gastropods (Korshunova et al, 2022 ; Sun et al, 2022 ) and the evolution of small RNAs in cnidarians (Li & Hui, 2022 ).…”

“…Perspective/ review pieces include reflections on the development of Marine Evolutionary Biology research as a whole (Johannesson et al, 2022), as well as detailed considerations of marine evo-devo research (Stracke & Hejnol, 2022), on divergence and speciation in the sea (De Jode et al, 2022), and on human-mediated evolution (Touchard et al, 2022). Furthermore, several manuscripts describe how technological improvements have allowed for more in-depth studies of genomic divergence (Pampoulie et al, 2022), the evolution of polymorphic traits (Gefaell et al, 2022), and the genomic mechanisms underlying phenotypic traits (Li & Hui, 2022). One major topic studied within the Marine Evolutionary Biology community is the interplay between genetic and plastic mechanisms in the processes of local adaptation, ecotype formation, and speciation, and how these processes may be impacted by, e.g., sexual selection, individuals' dispersal patterns, or species-specific genomic properties, such as the size and distribution of chromosomal rearrangements (e.g., Faria et al, 2021;Ravinet et al, 2017).…”

Dominant gingers – discovery and inheritance of a new shell polymorphism in the great pond snailLymnaea stagnalis

“…The Gastropoda is one of the most color polymorphic animal groups (e.g., Lee et al 2022; Luttikhuizen and Drent 2008; Liu et al 2009, reviewed in Williams 2017; Gefaell et al 2022). However, except for a few cases like Cepaea , the genetic basis, evolution and ecological meanings of these colors largely remain to be examined.…”

Dominant gingers – Discovery and inheritance of a new shell polymorphism in the great pond snail Lymnaea stagnalis

“…The Gastropoda is one of the most color polymorphic animal groups (e.g., Lee et al., 2022; Liu et al., 2009; Luttikhuizen & Drent, 2008; reviewed in Gefaell et al., 2022; Williams, 2017). However, except for a few cases like Cepaea , the genetic basis, evolution and ecological meanings of these colors largely remain to be examined.…”