A Framework for Understanding Marine Cosmopolitanism in the Anthropocene

Abstract

Recent years have witnessed growing appreciation for the ways in which human-mediated species introductions have reshaped marine biogeography. Despite this we have yet to grapple fully with the scale and impact of anthropogenic dispersal in both creating and determining contemporary distributions of marine taxa. In particular, the past several decades of research on marine biological invasions have revealed that broad geographic distributions of coastal marine organisms—historically referred to simply as “cosmopolitanism”—may belie complex interplay of both natural and anthropogenic processes. Here we describe a framework for understanding contemporary cosmopolitanism, informed by a synthesis of the marine bioinvasion literature. Our framework defines several novel categories in an attempt to provide a unified terminology for discussing cosmopolitan distributions in the world’s oceans. We reserve the term eucosmopolitan to refer to those species for which data exist to support a true, natural, and prehistorically global (or extremely broad) distribution. While in the past this has been the default assumption for species observed to exhibit contemporary cosmopolitan distributions, we argue that given recent advances in marine invasion science this assignment should require positive evidence. In contrast, neocosmopolitan describes those species that have demonstrably achieved extensive geographic ranges only through historical anthropogenic dispersal, often facilitated over centuries of human maritime traffic. We discuss the history and human geography underpinning these neocosmopolitan distributions, and illustrate the extent to which these factors may have altered natural biogeographic patterns. We define the category pseudocosmopolitan to encompass taxa for which a broad distribution is determined (typically after molecular investigation) to reflect multiple, sometimes regionally endemic, lineages with uncertain taxonomic status; such species may remain cosmopolitan only so long as taxonomic uncertainty persists, after which they may splinter into multiple geographically restricted species. We discuss the methods employed to identify such species and to resolve both their taxonomic status and their biogeographic histories. We argue that recognizing these different types of cosmopolitanism, and the important role that invasion science has played in understanding them, is critically important for the future study of both historical and modern marine biogeography, ecology, and biodiversity.

Unravelling the origin and introduction pattern of the tropical species Paracaprella pusilla Mayer, 1890 (Crustacea, Amphipoda, Caprellidae) in temperate European waters: first molecular insights from a spatial and temporal perspective

“…S2B). Therefore, our findings support the assumption that anthropogenic dispersal is responsible for the broad geographic distribution of P. pusilla and confirms that this is a neocosmopolitan species (see Darling and Carlton 2018).…”

“…Nevertheless, other NIS are actually widely distributed (no cryptic species); examples include the caprellids Caprella mutica and Caprella scaura sensu stricto (Ashton et al 2008;Cabezas et al 2014). Morphological evidence supports the conspecificity of populations of P. pusilla (Ros et al 2014), but molecular evidence is still needed to confirm P. pusilla as a neocosmopolitan species (introduced species that have achieved a widespread distribution through anthropogenic dispersal; sensu Darling and Carlton 2018).…”

Scientific collaboration for early detection of invaders results in a significant update on estimated range: lessons from Stenothoe georgiana Bynum & Fox 1977

“…An early and rapid exchange of information amongst several amphipod experts aided other researchers working with NIS in fouling communities to detect the new invader in other Mediterranean regions (Ferrario et al, 2017(Ferrario et al, , 2018Ulman et al, 2017Ulman et al, , 2019Servello et al, 2019). As a further advancement of the above-mentioned collaboration, we present here an updated worldwide distribution of the species, including new records, along with a discussion about invasion dynamics and S. georgiana's new status as a neo-cosmopolitan species (sensu Darling & Carlton, 2018). Using this case study, we highlight the need for scientific cooperation to properly address early detections and better manage invasive species.…”

Ancient globetrotters—connectivity and putative native ranges of two cosmopolitan biofouling amphipods

“…Many coastal benthic species that occur in anthropogenic habitats, especially those associated with the hulls of wooden ships (i.e., fouling and boring), had probably been distributed across the oceans by human shipping activities centuries before their geographic distributions were scientifically documented for the first time. As a consequence, modern geographic distributions of some marine species show cosmopolitan occurrences (e.g., Conlan, 1990;Thiel & Gutow, 2005), classified as "neocosmopolitan" (sensu Darling & Carlton, 2018). There is much speculation as to the likely former native ranges of coastal benthic species, with many still not reliably assigned native or introduced status in parts of their global range (Geller, Darling & Carlton, 2010).…”

“…There is much speculation as to the likely former native ranges of coastal benthic species, with many still not reliably assigned native or introduced status in parts of their global range (Geller, Darling & Carlton, 2010). In parallel, there is mounting evidence from modern taxonomy and molecular research studies which increasingly cast doubt on the existence of marine benthic "eucosmopolitan" species (sensu Darling & Carlton, 2018;Havermans, 2016).…”