The Importance of the Human Footprint in Shaping the Global Distribution of Terrestrial, Freshwater and Marine Invaders

Human activities such as transport, trade and tourism are likely to influence the spatial distribution of non-native species and yet, Species Distribution Models (SDMs) that aim to predict the future broad scale distribution of invaders often rely on environmental (e.g. climatic) information only. This study investigates if and to what extent do human activities that directly or indirectly influence nature (hereafter the human footprint) affect the global distribution of invasive species in terrestrial, freshwater and marine ecosystems. We selected 72 species including terrestrial plants, terrestrial animals, freshwater and marine invasive species of concern in a focus area located in NW Europe (encompassing Great Britain, France, The Netherlands and Belgium). Species Distribution Models were calibrated with the global occurrence of species and a set of high-resolution (9×9 km) environmental (e.g. topography, climate, geology) layers and human footprint proxies (e.g. the human influence index, population density, road proximity). Our analyses suggest that the global occurrence of a wide range of invaders is primarily limited by climate. Temperature tolerance was the most important factor and explained on average 42% of species distribution. Nevertheless, factors related to the human footprint explained a substantial amount (23% on average) of species distributions. When global models were projected into the focus area, spatial predictions integrating the human footprint featured the highest cumulative risk scores close to transport networks (proxy for invasion pathways) and in habitats with a high human influence index (proxy for propagule pressure). We conclude that human related information–currently available in the form of easily accessible maps and databases—should be routinely implemented into predictive frameworks to inform upon policies to prevent and manage invasions. Otherwise we might be seriously underestimating the species and areas under highest risk of future invasions.The first author would like to thank the constructive comments and advice on the manuscript made by Drs Montserrat Vilà, Juan Pedro González-Varo and Pablo González-Moreno.Peer reviewe

High rates of biodeposition and N-excretion indicate strong functional effects of mussels (Bivalvia: Unionida) in certain anthropogenic tropical freshwater habitats

The functional roles of freshwater mussels (Unionida) in tropical systems are poorly understood. We quantified the effects of mussel filtration, excretion and deposition in three anthropogenic tropical systems, i.e. a man-made lake, abandoned mining pool and rice paddy channel. Sinanodonta cf. woodiana (non-native) was present at all three sites, whilst Pilsbryoconcha compressa (native) was present in the channel only. Clearance rates, biodeposition rates and effects on suspended algal pigment and dissolved nutrient concentrations were quantified in controlled, replicated experiments in laboratory tanks with water from original habitats. Clearance rates were generally low and did not explain the high biodeposition rates observed. A considerable proportion of the natural diet of these populations may therefore consist of material that was not available in tanks, i.e. benthic or deposited algae. Deposition rates in lake and channel populations exceeded published rates from temperate and Mediterranean habitats, presumably due to prevalence of non-palatable material and/or higher metabolic rates in tropical systems. The presence of S. cf. woodiana but not P. compressa led to a strong increase in total ammonia nitrogen concentrations and N:P ratios, exceeding estimations from other systems. This study suggests that freshwater mussels play different functional roles in anthropogenic tropical habitats than in temperate systems

Revisiting the North American freshwater mussel genus Quadrula sensu lato (Bivalvia Unionidae): phylogeny, taxonomy and species delineation

© 2019 Royal Swedish Academy of Sciences Freshwater mussels (Bivalvia, Unionidae) have suffered strong declines over the last century. High morphological plasticity of Unionidae causes disturbances in their systematics and taxonomy, hampering conservation efforts. Species that have historically been placed under the North American genus Quadrula have suffered from numerous taxonomic and species delineation problems since its inception. Four genera are presently recognized within Quadrula sensu lato, that is, Cyclonaias, Quadrula, Theliderma and Tritogonia, but their phylogenetic basis remains incompletely tested. In the present study, we reconstructed several two-marker (mtDNA cytochrome c oxidase subunit I—COI and NADH dehydrogenase subunit 1—ND1) phylogenies with newly collected specimens and all previously available sequences covering most species within this group. We then delineated the species within the group using an integrative approach with the application of molecular statistical methods, morphometric (Fourier Shape) analyses and geographic distribution data. Four clades corresponding to these genera were consistently recovered in all phylogenies. To validate the generic status of these clades, molecular analyses were complemented with morphological, anatomical and ecological data compiled from the literature. Several revisions are here proposed to the current systematics and taxonomy of these genera, including the synonymization of Cyclonaias asperata under Cyclonaias kieneriana; the inclusion of Quadrula apiculata and Quadrula rumphiana under Quadrula quadrula; the placement of Quadrula nobilis under Tritogonia; and finally the separation of the Mobile River basin populations of Theliderma metanevra as a new species, that is, Theliderma johnsoni n. sp. The conservation implications of the proposed changes are then discussed

Effects of mussels on nutrient cycling and bioseston in two contrasting tropical freshwater habitats

Freshwater mussels (Unionida) can strongly affect nutrient cycling in temperate ecosystems but data from the tropics is lacking. We quantified the effects of mussel filtration, excretion and biodeposition on nutrient and photosynthetic pigment concentrations in a tropical eutrophic lake and mesotrophic river, featuring one non-native and two native species, respectively. Changes in nutrient and pigment concentrations were measured over a 3h-period to assess effects on (1) the water column in field enclosures, and (2) water column and benthos combined in controlled laboratory experiments. In field enclosures in both systems, mussel density and biomass were significantly correlated with the magnitude of reduction in sestonic pigment concentrations. In laboratory experiments, presence of mussels led to reduced PO4 and increased TAN concentrations in both systems, lower combined sestonic and deposited pigment concentrations in the river but increases of the same in the lake. We conclude that excretion by mussels probably accelerated bioseston growth in both systems due to N-35 fertilisation, an effect that may be particularly common in tropical freshwaters, which are frequently N-limited. However, whilst river mussels reduced bioseston concentrations through rapid filtration, higher rates of N-excretion and/or deposition of undigested bioseston by lake mussels apparently resulted in a net-increase of pigment concentrations

Towards the conservation of Borneo’s freshwater mussels: rediscovery of the endemic Ctenodesma borneensis and first record of the non-native Sinanodonta lauta

The freshwater mussel fauna of Borneo is highly endemic, with at least 11 species being unique to that island. Most of these species have not been recorded for at least 50 years owing to a lack of sampling effort and large-scale habitat destruction and degradation. Surveys conducted in 2016 across much of Malaysian Borneo failed to locate four out of five native species historically recorded in the study area. The present study aimed to determine the diversity and distribution of freshwater mussels of Brunei and adjacent Limbang Division, Malaysia. In 2018, we conducted interviews with locals, recorded environmental data and surveyed mussels at 43 sites, and conducted interviews at a further 38 sites. Only one population of native mussels, i.e. Ctenodesma borneensis, was found in a small tributary of the Limbang River situated in a patch of intact rainforest, representing the first record of this Bornean endemic genus since 1962. In addition, Sinanodonta lauta was found in a pond in Lawas district, representing the first record of this species outside its native East Asian distribution. Our data suggest that C. borneensis can sustain populations in relatively undisturbed habitats and is likely to have suffered population losses across northern Borneo. The first molecular phylogenetic analysis (COI + 28S) including an endemic Bornean freshwater mussel genus revealed that Ctenodesma is phylogenetically divergent from all other previously sampled lineages, rendering it a particularly valuable conservation target

Phylogeny of European Anodontini (Bivalvia: Unionidae) with a redescription of Anodonta exulcerata

Freshwater bivalves are highly threatened and globally declining due to multiple anthropogenic impacts, making them important conservation targets. Because conservation policies and actions generally occur at the species level, accurate species identification and delimitation is critical. A recent phylogenetic study of Italian mussel populations revalidated an Anodonta species bringing the number of known European Anodontini from three to four species. The current study contributes to the clarification of the taxonomy and systematics of European Anodontini, using a combination of molecular, morphological and anatomical data, and constructs phylogenies based on complete mitogenomes. A redescription of A. exulcerata and a comparative analysis of morphological and anatomical characters with respect to the other two species of Anodonta present in the area are provided. No reliable diagnostic character has emerged from comparative analysis of the morphometric characters of 109 specimens from 16 sites across the Italian peninsula. In fact, the discriminant analysis resulted in a greater probability of correct assignment to the site of origin than to the species. This confirms the difficulties of an uncritical application of visual characters for the delimitation of species, especially for Anodontinae.This research was developed under ConBiomics: the missing approach for the conservation of freshwater bivalves project Nº NORTE-01-0145-FEDER-030286, cofinanced by COMPETE 2020, Portugal 2020 and the European Union through the ERDF - European Regional Development Fund and by FCT - Fundação para a Ciência e a Tecnologia, through national funds (UID/Multi/04423/2019). FCT also supported Manuel Lopes-Lima (SFRH/BD/115728/2016).info:eu-repo/semantics/publishedVersio

Integrated taxonomy reveals new threatened freshwater mussels (Bivalvia: Hyriidae: Westralunio ) from southwestern Australia

The freshwater mussel Westralunio carteri (Iredale, 1934) has long been considered the sole Westralunio species in Australia, limited to the Southwest and listed as vulnerable on the IUCN Red List and under Australian legislation. Here, we used species delimitation models based on COI mtDNA sequences to confirm existence of three evolutionarily significant units (ESUs) within this taxon and conducted morphometric analyses to investigate whether shell shape differed significantly among these ESUs. “W. carteri” I was found to be significantly larger and more elongated than “W. carteri” II and “W. carteri” II + III combined, but not different from “W. carteri” III alone. We recognise and redescribe “W. carteri” I as Westralunio carteri (Iredale, 1934) from western coastal drainages and describe “W. carteri” II and “W. carteri” III as Westralunio inbisi sp. nov. from southern and lower southwestern drainages. Two subspecies are further delineated: “W. carteri” II is formally described as Westralunio inbisi inbisi subsp. nov. from southern coastal drainages, and “W. carteri” III as Westralunio inbisi meridiemus subsp. nov. from the southwestern corner. Because this study profoundly compresses the range of Westralunio carteri northward and introduces additional southern and southwestern taxa with restricted distributions, new threatened species nominations are necessary

Current and future effects of global change on a hotspot's freshwater diversity

Deforestation, climate change and invasive species constitute three global threats to biodiversity that act synergistically. However, drivers and rates of loss of freshwater biodiversity now and in the future are poorly understood. Here we focus on the potential impacts of global change on freshwater mussels (Order Unionida) in Sundaland (SE Asia), a vulnerable group facing global declines and recognized indicators of overall freshwater biodiversity. We used an ensemble of distribution models to identify habitats potentially suitable for freshwater mussels and their change under a range of climate, deforestation and invasion scenarios. Our data and models revealed that, at present, Sundaland features 47 and 32 Mha of habitat that can be considered environmentally suitable for native and invasive freshwater mussels, respectively. We anticipate that by 2050, the area suitable for palm oil cultivation may expand between 8 and 44 Mha, representing an annual increase of 2–11%. This is expected to result in a 20% decrease in suitable habitat for native mussels, a drop that reaches 30% by 2050 when considering concomitant climate change. In contrast, the habitat potentially suitable for invasive mussels may increase by 44–56% under 2050 future scenarios. Consequently, native mussels may compete for habitat, food resources and fish hosts with invasive mussels across approximately 60% of their suitable range. Our projections can be used to guide future expeditions to monitor the conservation status of freshwater biodiversity, and potentially reveal populations of endemic species on the brink of extinction. Future conservation measures—most importantly the designation of nature reserves—should take into account trends in freshwater biodiversity generally, and particularly species such as freshwater mussels, vital to safeguard fundamental ecosystem services.This study is funded by the Malaysian Ministry of Higher Education (Project FRGS/1/2015/WAB13/UNIM//1). BG was supported by a research fellowship funded by the Spanish Program of R + D + I (JCI2012-11908)

Conservation status assessment and a new method for establishing conservation priorities for freshwater mussels (Bivalvia: Unionida) in the middle and lower reaches of the Yangtze River drainage

1. The freshwater mussel (Unionida) fauna of the Yangtze River is among the most diverse on Earth. In recent decades, human activities have caused habitat degradation in the river, and previous studies estimated that up to 80% of the mussel species in the Yangtze River are Threatened or Near Threatened with extinction. However, a comprehensive and systematic evaluation of the conservation status of this fauna has yet to be completed.2. This study evaluated the conservation status of the 69 recognized freshwater mussel species in the middle and lower reaches of the Yangtze River, using the criteria published by the International Union for Conservation of Nature (IUCN). A new method for prioritizing species for conservation was then developed and applied termed Quantitative Assessment of Species for Conservation Prioritization (QASCP), which prioritizes species according to quantifiable data on their distribution and population status, life history, and recovery importance and potential.3. IUCN assessments showed that 35 (51%) species in the study region are Threatened or Near Threatened (11 Endangered, 20 Vulnerable, 4 Near Threatened). In addition, 16 species (23%) could not be assessed owing to data deficiency. Key threats to the freshwater mussel biodiversity of the Yangtze River include pollution, habitat loss and fragmentation, loss of access to host fish, and overharvesting of mussels and their host fish. The genera Aculamprotula, Gibbosula, Lamprotula, Pseudodon, Ptychorhynchus, and Solenaia were identified as particularly threatened.4. Data availability allowed QASCP assessment of 44 species. Only Solenaia carinata, regionally Endangered under IUCN criteria, achieved the highest QASCP rank, i.e. First Priority. The five species assessed as Second Priority were considered either regionally Endangered (one), Vulnerable (three), or Data Deficient (one) under IUCN criteria. The 23 Third Priority species were assessed as regionally Endangered (two), Vulnerable (15), Near Threatened (two), or Least Concern (four)