Ship traffic connects Antarctica's fragile coasts to worldwide ecosystems.

Antarctica, an isolated and long considered pristine wilderness, is becoming increasingly exposed to the negative effects of ship-borne human activity, and especially the introduction of invasive species. Here, we provide a comprehensive quantitative analysis of ship movements into Antarctic waters and a spatially explicit assessment of introduction risk for nonnative marine species in all Antarctic waters. We show that vessels traverse Antarctica's isolating natural barriers, connecting it directly via an extensive network of ship activity to all global regions, especially South Atlantic and European ports. Ship visits are more than seven times higher to the Antarctic Peninsula (especially east of Anvers Island) and the South Shetland Islands than elsewhere around Antarctica, together accounting for 88% of visits to Southern Ocean ecoregions. Contrary to expectations, we show that while the five recognized "Antarctic Gateway cities" are important last ports of call, especially for research and tourism vessels, an additional 53 ports had vessels directly departing to Antarctica from 2014 to 2018. We identify ports outside Antarctica where biosecurity interventions could be most effectively implemented and the most vulnerable Antarctic locations where monitoring programs for high-risk invaders should be established.

Host and parasite identity interact in scale-dependent fashion to determine parasite community structure.

Understanding the ecological assembly of parasite communities is critical to characterise how changing host and environmental landscapes will alter infection dynamics and outcomes. However, studies frequently assume that (a) closely related parasite species or those with identical life-history strategies are functionally equivalent, and (b) the same factors will drive infection dynamics for a single parasite across multiple host species, oversimplifying community assembly patterns. Here, we challenge these two assumptions using a naturally occurring host-parasite system, with the mussel Anodonta anatina infected by the digenean trematode Echinoparyphium recurvatum, and the snail Viviparus viviparus infected by both E. recurvatum and Echinostoma sp. By analysing the impact of temporal parasite dispersal, host species and size, and the impact of coinfection (moving from broader environmental factors to within-host dynamics), we show that neither assumption holds true, but at different ecological scales. The assumption that closely related parasites can be functionally grouped is challenged when considering dispersal to the host (i.e. larger scales), while the assumption that the same factors will drive infection dynamics for a single parasite across multiple host species is challenged when considering within-host interspecific competition (i.e. smaller scales). Our results demonstrate that host identity, parasite identity and ecological scale require simultaneous consideration in studies of parasite community composition and transmission.

Freshwater mussel conservation: A global horizon scan of emerging threats and opportunities.

We identified 14 emerging and poorly understood threats and opportunities for addressing the global conservation of freshwater mussels over the next decade. A panel of 17 researchers and stakeholders from six continents submitted a total of 56 topics that were ranked and prioritized using a consensus-building Delphi technique. Our 14 priority topics fell into five broad themes (autecology, population dynamics, global stressors, global diversity, and ecosystem services) and included understanding diets throughout mussel life history; identifying the drivers of population declines; defining metrics for quantifying mussel health; assessing the role of predators, parasites, and disease; informed guidance on the risks and opportunities for captive breeding and translocations; the loss of mussel-fish co-evolutionary relationships; assessing the effects of increasing surface water changes; understanding the effects of sand and aggregate mining; understanding the effects of drug pollution and other emerging contaminants such as nanomaterials; appreciating the threats and opportunities arising from river restoration; conserving understudied hotspots by building local capacity through the principles of decolonization; identifying appropriate taxonomic units for conservation; improved quantification of the ecosystem services provided by mussels; and understanding how many mussels are enough to provide these services. Solutions for addressing the topics ranged from ecological studies to technological advances and socio-political engagement. Prioritization of our topics can help to drive a proactive approach to the conservation of this declining group which provides a multitude of important ecosystem services.

Declines in freshwater mussel density, size and productivity in the River Thames over the past half century.

A pioneering, quantitative study published in Journal of Animal Ecology in 1966 on freshwater mussel populations in the River Thames, UK, continues to be cited extensively as evidence of the major contribution that mussels make to benthic biomass and ecosystem functioning in global river ecosystems. Ecological alteration, as well as declines in freshwater mussel populations elsewhere, suggest that changes to mussel populations in the River Thames are likely to have occurred over the half century since this study. We resurveyed the site reported in Negus (1966) and quantified the changes in mussel population density, species composition, growth patterns and productivity. We found large declines in population density for all unionid species. The duck mussel Anodonta anatina decreased to 1.1% of 1964 density. The painter's mussel Unio pictorum fell to 3.2% of 1964 density. The swollen river mussel Unio tumidus showed statistically nonsignificant declines. In contrast to 1964, in 2020 we found no living specimens of the depressed river mussel Pseudanodonta complanata (classified as Vulnerable by the IUCN Red List) but found new records of the invasive, nonnative zebra mussel Dreissena polymorpha and Asian clam Corbicula fluminea. Additionally, we found strong decreases in size-at-age for all species, which now grow to 65-90% of maximum lengths in 1964. As a result of reduced density and size, estimated annual biomass production fell to 7.5% of 1964 levels. Since mussels can be important to ecosystem functioning, providing key regulating and provisioning services, the declines we found imply substantial degradation of freshwater ecosystem services in the River Thames, one of the UK's largest rivers. Our study also highlights the importance to conservationists and ecologists of updating and validating assumptions and data about wild populations, which in the present era of anthropogenic ecosystem alteration are undergoing significant and rapid changes. Regular population surveys of key species are essential to maintain an accurate picture of ecosystem health and to guide management.

Factors at multiple scales drive parasite community structure.

Understanding how ecological communities are assembled remains a key goal of ecosystem ecology. Because communities are hierarchical, factors acting at multiple scales can contribute to patterns of community structure. Parasites provide a natural system to explore this idea, as they exist as discrete communities within host individuals, which are themselves part of a community and metacommunity. We aimed to understand the relative contribution of multi-scale drivers in parasite community assembly and assess how patterns at one level may mask those occurring at another. Specifically, we wanted to disentangle patterns caused by passive sampling from those determined by ecological drivers, and how these vary with scale. We applied a Markov Random Fields model and assessed measures of ß-diversity and nestedness for 420 replicate parasite infracommunities (parasite assemblages in host individuals) across two freshwater mussel host species, three sites and two time periods, comparing our results to simulations from four different ecologically relevant null models. We showed that ß-diversity between sites (explaining 25% of variation in parasite distribution) and host species (41%) is greater than expected, and ß-diversity between individual hosts is smaller than expected, even after accounting for parasite prevalence and characteristics of host individuals. Furthermore, parasite communities were significantly less nested than expected once parasite prevalence and host characteristics were both accounted for, but more nested than expected otherwise, suggesting a degree of modularity at the within-host level that is masked if underlying host and parasite characteristics are not taken into account. The Markov Random Fields model provided evidence for possible competitive within-host parasite interactions, providing a mechanism for the observed infracommunity modularity. An integrative approach that examines factors at multiple scales is necessary to understand the composition of ecological communities. Furthermore, patterns at one level can alter the interpretation of ecologically important drivers at another if variation at higher scales is not accounted for.

A roadmap for the conservation of freshwater mussels in Europe.

Europe has a long history of human pressure on freshwater ecosystems. As pressure continues to grow and new threats emerge, there is an urgent need for conservation of freshwater biodiversity and its ecosystem services. However, whilst some taxonomic groups, mainly vertebrates, have received a disproportionate amount of attention and funds, other groups remain largely off the public and scientific radar. Freshwater mussels (Bivalvia, Unionida) are an alarming example of this conservation bias and here we point out six conceptual areas that need immediate and long-term attention: knowledge, threats, socioeconomics, conservation, governance and education. The proposed roadmap aims to advance research, policy and education by identifying the most pressing priorities for the short- and long-term conservation of freshwater mussels across Europe.

Mussel parasite richness and risk of extinction.

Parasite conservation is important for the maintenance of ecosystem diversity and function. Conserving parasites relies first on understanding parasite biodiversity and second on estimating the extinction risk to that biodiversity. Although steps have been taken independently in both these areas, previous studies have overwhelmingly focused on helminths in vertebrate hosts over broad scales, providing low resolution and excluding a large proportion of possible host and parasite diversity. We estimated both total obligate parasite richness and parasite extinction risk in freshwater mussels (Unionidae and Margaritiferidae) from Europe and the United States to provide a case study for considering parasite conservation in a severely understudied system. We used currently reported host-parasite relationships to extrapolate parasite diversity to all possible mussel hosts and then used the threat levels of those hosts to estimate the extinction risk for both described and undescribed parasites. An estimated 67% of parasite richness in freshwater mussels is undescribed and over 80% of the most host-specific groups (digenean trematodes and ciliates) are undescribed. We estimated that 21% of this total parasite fauna is at immediate risk of extinction, corresponding to 60 unique species, many of which will likely go extinct before being described. Given the important roles parasites play in community structure and function and the strong ecosystem engineering capacities of freshwater mussels, such extinctions are likely to severely affect freshwater ecosystems. Our detailed study of mussel parasites provides compelling evidence for the hidden conservation threat to parasites through extinction cascades and shows parasites are deserving of immediate attention.

La conservación de parásitos es importante para el mantenimiento de la diversidad y funcionamiento de los ecosistemas. La conservación de parásitos depende en primera instancia del entendimiento de la biodiversidad de parásitos y, en segunda, de la estimación del riesgo de extinción de esa biodiversidad. Mientras que se han tomado medidas en ambas áreas, estudios previos se han enfocado abrumadoramente en helmintos de hospederos vertebrados, proporcionando baja resolución y excluyendo a una amplia proporción de una probable diversidad de hospederos y parásitos. Estimamos tanto la riqueza de parásitos obligados como el riesgo de extinción de mejillones de agua dulce (Unionidae y Margaritiferidae) de Europa y Estados Unidos para proporcionar un caso de estudio para considerar la conservación de parásitos en un sistema severamente poco estudiado. Utilizamos las relaciones hospedero-parásito registradas hasta la fecha para extrapolar la diversidad de parásitos a todas las especies posibles de mejillones hospederos y luego utilizamos los niveles de amenaza de aquellos hospederos para estimar el riesgo de extinción tanto para parásitos descritos y no descritos. Alrededor de 67% de la riqueza de parásitos de mejillones de agua dulce no esta descrito, así como mas de 80% de los grupos específicos de hospederos (trematodos digeneos y ciliados) tampoco están descritos. Estimamos que 21% del total de esta fauna de parásitos está en riesgo inminente de extinción, correspondiendo a 60 especies únicas, muchas de las cuales probablemente se extinguirán antes de ser descritas. Dado la importancia del papel que desempeñan los parásitos en la estructura y función de la comunidad y las notables capacidades de los mejillones de agua dulce para la ingeniería del ecosistema, es muy probable que tales extinciones afecten severamente a los ecosistemas dulceacuícolas. Nuestro estudio detallado de los parásitos de mejillones proporciona evidencia convincente de la amenaza oculta para los parásitos mediante cascadas de extinción y muestra que los parásitos son merecedores de atención inmediata.

Global impacts of invasive species on the tipping points of shallow lakes.

There is growing acknowledgement that human-induced change can push ecosystems beyond tipping points, resulting in the dramatic and sudden loss of vital ecosystem services. Invasive non-native species (INNS) are spreading rapidly due to anthropogenic activities and climate change and can drive changes to ecosystem functioning by altering abiotic conditions and restructuring native communities. Shallow lake ecosystems are especially vulnerable to perturbation from INNS as they can exist in two alternative stable states: either clear water with an abundance of vegetation or turbid, unvegetated and dominated by phytoplankton. Through a global meta-analysis of studies observing the effects of INNS on recipient lake ecosystems, we found that certain INNS drive significant changes in the abundance of key taxa and conditions that govern the balance of alternative equilibria in shallow lakes. Invasive fish and crustaceans demonstrated effects likely to lead to early ecosystem collapse to a turbid state and delay ecosystem recovery. Invasive molluscs presented opposite effects, which may delay ecosystem collapse and encourage ecosystem recovery. Our results demonstrate that INNS could significantly alter the tipping points of ecosystem collapse and recovery, and that not all invasive species may initiate system collapse. Our results provide guidance for managers of invaded shallow lake ecosystems, which provide diverse services including sanitation, potable water supply, industrial cooling, aquaculture and recreational resources. Moreover, our approach could be applied to identify key potential drivers of change in other crucial ecosystems which demonstrate alternative equilibria, such as coral reefs and kelp forests.

Global Diversification Dynamics Since the Jurassic: Low Dispersal and Habitat-Dependent Evolution Explain Hotspots of Diversity and Shell Disparity in River Snails (Viviparidae).

The Viviparidae, commonly known as River Snails, is a dominant group of freshwater snails with a nearly worldwide distribution that reaches its highest taxonomic and morphological diversity in Southeast Asia. The rich fossil record is indicative of a probable Middle Jurassic origin on the Laurasian supercontinent where the group started to diversify during the Cretaceous. However, it remains uncertain when and how the biodiversity hotspot in Southeast Asia was formed. Here, we used a comprehensive genetic data set containing both mitochondrial and nuclear markers and comprising species representing 24 out of 28 genera from throughout the range of the family. To reconstruct the spatiotemporal evolution of viviparids on a global scale, we reconstructed a fossil-calibrated phylogeny. We further assessed the roles of cladogenetic and anagenetic events in range evolution. Finally, we reconstructed the evolution of shell features by estimating ancestral character states to assess whether the appearance of sculptured shell morphologies was driven by major habitat shifts. The molecular phylogeny supports the monophyly of the three subfamilies, the Bellamyinae, Lioplacinae, and Viviparinae, but challenges the currently accepted genus-level classification in several cases. The almost global distribution of River Snails has been influenced both by comparatively ancient vicariance and more recent founder events. In Southeast Asia, Miocene dispersal was a main factor in shaping the modern species distributions. A recurrent theme across different viviparid taxa is that many species living in lentic waters exhibit sculptured shells, whereas only one strongly sculptured species is known from lotic environments. We show that such shell sculpture is habitat-dependent and indeed evolved several times independently in lentic River Snails. Considerably high transition rates between shell types in lentic habitats probably caused the co-occurrence of morphologically distinct shell types in several lakes. In contrast, directional evolution toward smooth shells in lotic habitats, as identified in the present analyses, explains why sculptured shells are rarely found in these habitats. However, the specific factors that promoted changes in shell morphology require further work. [biogeographical analyses; fossil-calibrated phylogeny; fossil-constrained analyses; Southeast Asia; stochastic character mapping.].

Abundance data applied to a novel model invertebrate host shed new light on parasite community assembly in nature.

Understanding how environmental drivers influence the assembly of parasite communities, in addition to how parasites may interact at an infracommunity level, are fundamental requirements for the study of parasite ecology. Knowledge of how parasite communities are assembled will help to predict the risk of parasitism for hosts, and model how parasite communities may change under variable conditions. However, studies frequently rely on presence-absence data and examine multiple host species or sites, metrics which may be too coarse to characterise nuanced within-host patterns. We utilised a novel host system, the freshwater mussel Anodonta anatina, to investigate the drivers of community structure and explore parasite interactions. In addition, we aimed to highlight consistencies and inconsistencies between PA and abundance data. Our analysis incorporated 14 parasite taxa and 720 replicate infracommunities. Using Redundancy Analysis, a joint species distribution model and a Markov random field approach, we modelled the impact of both host-level and environment-level characteristics on parasite structure, as well as parasite-parasite correlations after accounting for all other factors. This approach was repeated for both the presence and abundance of all parasites. We demonstrated that the regional species pool, individual host characteristics (mussel length and gravidity) and predicted parasite-parasite interactions are all important but to varying degrees across parasite species, suggesting that applying generalities to parasite community construction is too simplistic. Furthermore, we showed that PA data fail to capture important density-dependent effects of parasite load for parasites with high abundance, and in general performs poorly for high-intensity parasites. Host and parasite traits, as well as broader environmental factors, all contribute to parasite community structure, emphasising that an integrated approach is required to study community assembly. However, care must be taken with the data used to infer patterns, as presence-absence data may lead to incorrect ecological inference.

Using osmotic shock to control invasive aquatic species.

Coastal estuaries are especially vulnerable to the arrival and establishment of invasive aquatic species (IAS) as they are often the receiving locations of ship-based introductions. Rapid response tools, such as mechanical or chemical treatments to capture, remove, and contain of IAS, are needed to prevent subsequent spread into adjacent marine and freshwater systems. Abrupt salinity change, created when infrastructure in estuaries situated at the proximity of river mouths is operated, offers a novel, low-cost and environmentally friendly method for potentially controlling IAS. We investigated the use of osmotic shock to control the invasive brackish water clam Rangia cuneata that is quickly spreading through Europe. Clams were exposed in the laboratory to eight salinity concentrations ranging from 0.5 to 32.0‰ and monitored for 60 days. Saline shock, but not freshwater shock, could control R. cuneata. Salinities >26‰ killed 95% R. cuneata in two weeks. All specimens exposed to full strength seawater (32‰) were killed within 30 days. At lower salinities, clams collected from the most freshwater locality (1.2‰) showed lower mortality than clams from the most saline site (3.1‰). Furthermore, even modest increases in salinity during spawning periods of R. cuneata may prevent recruitment. Given the vulnerability of coastal estuaries to introduction of IAS, saline flushing presents a novel and effective management tool for many species.

Mesozoic mitogenome rearrangements and freshwater mussel (Bivalvia: Unionoidea) macroevolution.

Using a new fossil-calibrated mitogenome-based approach, we identified macroevolutionary shifts in mitochondrial gene order among the freshwater mussels (Unionoidea). We show that the early Mesozoic divergence of the two Unionoidea clades, Margaritiferidae and Unionidae, was accompanied by a synchronous split in the gene arrangement in the female mitogenome (i.e., gene orders MF1 and UF1). Our results suggest that this macroevolutionary jump was completed within a relatively short time interval (95% HPD 201-226 Ma) that coincided with the Triassic-Jurassic mass extinction. Both gene orders have persisted within these clades for ~200 Ma. The monophyly of the so-called "problematic" Gonideinae taxa was supported by all the inferred phylogenies in this study using, for the first time, the M- and F-type mitogenomes either singly or combined. Within Gonideinae, two additional splits in the gene order (UF1 to UF2, UF2 to UF3) occurred in the Mesozoic and have persisted for ~150 and ~100 Ma, respectively. Finally, the mitogenomic results suggest ancient connections between freshwater basins of East Asia and Europe near the Cretaceous-Paleogene boundary, probably via a continuous paleo-river system or along the Tethys coastal line, which are well supported by at least three independent but almost synchronous divergence events.

An efficient photograph-based quantitative method for assessing castrating trematode parasites in bivalve molluscs.

Parasitic castration of bivalves by trematodes is common, and may significantly reduce the reproductive capacity of ecologically important species. Understanding the intensity of infection is desirable, as it can indicate the time that has passed since infection, and influence the host's physiological and reproductive response. In addition, it is useful to know the developmental stage of the trematode, to understand trematode population trends and reproductive success. However, most existing methods (e.g. visually estimating the degree of infection) to assess intensity are approximate only and not reproducible. Here, we present a method to accurately quantify the percentage of bivalve gonad filled with digenean trematode tissue, based on small squashes of gonad tissue rapidly photographed under light microscopy. A maximum of 15 photographs is required to determine the percentage of the whole gonad occupied by trematodes with a minimum of 90% confidence, with smaller mussels requiring fewer. In addition, the stage of trematode infection can be assessed because full sporocysts, spent sporocysts and free cercariae are clearly distinguishable. Although variation exists in the distribution of trematodes in gonad tissue, and thus in the estimate of percentage of the gonad filled with trematodes, this method represents a marked improvement on current coarse assessments of infection which typically focus on binary presence/absence measures. This technique can be used to facilitate a more sophisticated understanding of host-parasite interactions in bivalves, and can inform the conservation and reproductive biology of environmentally crucial species.

Antarctica: The final frontier for marine biological invasions.

Antarctica is experiencing significant ecological and environmental change, which may facilitate the establishment of non-native marine species. Non-native marine species will interact with other anthropogenic stressors affecting Antarctic ecosystems, such as climate change (warming, ocean acidification) and pollution, with irreversible ramifications for biodiversity and ecosystem services. We review current knowledge of non-native marine species in the Antarctic region, the physical and physiological factors that resist establishment of non-native marine species, changes to resistance under climate change, the role of legislation in limiting marine introductions, and the effect of increasing human activity on vectors and pathways of introduction. Evidence of non-native marine species is limited: just four marine non-native and one cryptogenic species that were likely introduced anthropogenically have been reported freely living in Antarctic or sub-Antarctic waters, but no established populations have been reported; an additional six species have been observed in pathways to Antarctica that are potentially at risk of becoming invasive. We present estimates of the intensity of ship activity across fishing, tourism and research sectors: there may be approximately 180 vessels and 500+ voyages in Antarctic waters annually. However, these estimates are necessarily speculative because relevant data are scarce. To facilitate well-informed policy and management, we make recommendations for future research into the likelihood of marine biological invasions in the Antarctic region.

Developing a list of invasive alien species likely to threaten biodiversity and ecosystems in the European Union.

The European Union (EU) has recently published its first list of invasive alien species (IAS) of EU concern to which current legislation must apply. The list comprises species known to pose great threats to biodiversity and needs to be maintained and updated. Horizon scanning is seen as critical to identify the most threatening potential IAS that do not yet occur in Europe to be subsequently risk assessed for future listing. Accordingly, we present a systematic consensus horizon scanning procedure to derive a ranked list of potential IAS likely to arrive, establish, spread and have an impact on biodiversity in the region over the next decade. The approach is unique in the continental scale examined, the breadth of taxonomic groups and environments considered, and the methods and data sources used. International experts were brought together to address five broad thematic groups of potential IAS. For each thematic group the experts first independently assembled lists of potential IAS not yet established in the EU but potentially threatening biodiversity if introduced. Experts were asked to score the species within their thematic group for their separate likelihoods of i) arrival, ii) establishment, iii) spread, and iv) magnitude of the potential negative impact on biodiversity within the EU. Experts then convened for a 2-day workshop applying consensus methods to compile a ranked list of potential IAS. From an initial working list of 329 species, a list of 66 species not yet established in the EU that were considered to be very high (8 species), high (40 species) or medium (18 species) risk species was derived. Here, we present these species highlighting the potential negative impacts and the most likely biogeographic regions to be affected by these potential IAS.

Microencapsulated diets to improve growth and survivorship in juvenile European flat oysters (Ostrea edulis).

Sustainable expansion of aquaculture is critical to global food security, and bivalve shellfish aquaculture represents a sustainable method to provide people with affordable nutritious food. Oysters represent 54% of the global bivalve market by value, with propagation of juveniles within hatcheries critical to allow the industry to grow. Growth and survival of juvenile oysters in hatchery systems is constrained by suboptimal feed. The live algal feed currently used is expensive, of variable quality, contamination prone, and the high level of skill and equipment required limits where hatcheries can be located. We demonstrate how a novel microencapsulated diet can increase the growth and survivorship of Ostrea edulis (European flat oyster) juveniles in both the laboratory and hatchery setting. The microcapsules are easily produced in large quantities, stable for long term storage, and can be customised to have exceptionally high levels of nutrients key for oyster growth. O. edulis larvae fed a combined diet of microcapsules and algae for 8 days had a 46% greater increase in maximum size, 171% greater increase in minimum size, and 5% higher survival than larvae fed algae alone. O. edulis spat of 4 mm fed the combined diet for 7 weeks also had significantly greater survivorship (16% greater in hatchery, 58% greater in laboratory) and growth comparable (hatchery) or better (laboratory experiments) than algae alone. Further tailoring of the nutritional composition of microcapsules to specific bivalve species or growth stages could allow microcapsules to replace a greater proportion of or even completely replace algal diets. There is potential for these diets to revolutionise bivalve shellfish farming globally.

Expansion and systematics redefinition of the most threatened freshwater mussel family, the Margaritiferidae.

Two Unionida (freshwater mussel) families are present in the Northern Hemisphere; the Margaritiferidae, representing the most threatened of unionid families, and the Unionidae, which include several genera of unresolved taxonomic placement. The recent reassignment of the poorly studied Lamprotula rochechouartii from the Unionidae to the Margaritiferidae motivated a new search for other potential species of margaritiferids from members of Gibbosula and Lamprotula. Based on molecular and morphological analyses conducted on newly collected specimens from Vietnam, we here assign Gibbosula crassa to the Margaritiferidae. Additionally, we reanalyzed all diagnostic characteristics of the Margaritiferidae and examined museum specimens of Lamprotula and Gibbosula. As a result, two additional species are also moved to the Margaritiferidae, i.e. Gibbosula confragosa and Gibbosula polysticta. We performed a robust five marker phylogeny with all available margaritiferid species and discuss the taxonomy within the family. The present phylogeny reveals the division of Margaritiferidae into four ancient clades with distinct morphological, biogeographical and ecological characteristics that justify the division of the Margaritiferidae into two subfamilies (Gibbosulinae and Margaritiferinae) and four genera (Gibbosula, Cumberlandia, Margaritifera, and Pseudunio). The systematics of the Margaritiferidae family is re-defined as well as their distribution, potential origin and main biogeographic patterns.