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opencc-zeroDec 2014View details →

Data from: Local inter-species introgression is the main cause of extreme levels of intra-specific differentiation in mussels

Structured populations, and replicated zones of contact between species, are an ideal opportunity to study regions of the genome with unusual levels of differentiation; and these can illuminate the genomic architecture of species isolation, and the spread of adaptive alleles across species ranges. Here, we investigated the effects of gene flow on divergence and adaptation in the Mytilus complex of species, including replicated parental populations in quite distant geographical locations. We used target enrichment sequencing of 1269 contigs of a few Kb each, including some genes of known function, to infer gene genealogies at a small chromosomal scale. We show that geography is an important determinant of the genome-wide patterns of introgression in Mytilus, and that gene flow between different species, with contiguous ranges, explained up to half of the intra-specific outliers. This suggests that local introgression is both widespread and tends to affect larger chromosomal regions than purely intraspecific processes. We argue that this situation might be common, and this implies that genome scans should always consider the possibility of introgression from sister species, unsampled differentiated backgrounds, or even extinct relatives, e.g. Neanderthals in humans. The hypothesis that reticulate evolution over long periods of time contributes widely to adaptation, and to the spatial and genomic reorganisation of genetic backgrounds, needs to be more widely considered in order to make better sense of genome scans.

opencc-zeroDec 2019View details →

Comparative genomics reveals divergent thermal selection in warm- and cold-tolerant marine mussels

Investigating the history of natural selection among closely related species can elucidate how genomes diverge in response to disparate environmental pressures. Molecular evolutionary approaches can be integrated with knowledge of gene functions to examine how evolutionary divergence may affect ecologically-relevant traits such as temperature tolerance and species distribution limits. Here, we integrate transcriptome-wide analyses of molecular evolution with knowledge from physiological studies to develop hypotheses regarding the functional classes of genes under positive selection in one of the world's most widespread invasive species, the warm-tolerant marine mussel Mytilus galloprovincialis. Based on existing physiological information, we test the hypothesis that genomic functions previously linked to divergent temperature adaptation at the whole-organism level show accelerated molecular divergence between warm-adapted M. galloprovincialis and cold-adapted congeners. Combined results from codon model tests and analyses of polymorphism and divergence reveal that divergent selection has affected genomic functions previously associated with species-specific expression responses to heat stress, namely oxidative stress defense and cytoskeletal stabilisation. Examining specific loci implicated in thermal tolerance among Mytilus species (based on interspecific biochemical or expression patterns), we find close functional similarities between known thermotolerance candidate genes under positive selection and positively selected loci under predicted genomic functions (those associated with divergent expression responses). Taken together, our findings suggest a contribution of temperature-dependent selection in the molecular divergence between warm- and cold-adapted Mytilus species that is largely consistent with results from physiological studies. More broadly, this study provides an example of how independent experimental evidence from ecophysiological investigations can inform evolutionary hypotheses about molecular adaptation in closely related non-model species.

opencc-zeroDec 2014View details →

Data from: Ocean acidification and temperature increase impacts mussel shell shape and thickness: problematic for protection?

Ocean acidification threatens organisms that produce calcium carbonate shells by potentially generating an under-saturated carbonate environment. Resultant reduced calcification and growth, and subsequent dissolution of exoskeletons, would raise concerns over the ability of the shell to provide protection for the marine organism under ocean acidification and increased temperatures. We examined the impact of combined ocean acidification and temperature increase on shell formation of the economically important edible mussel Mytilus edulis. Shell growth and thickness along with a shell thickness index and shape analysis were determined. The ability of M. edulis to produce a functional protective shell after 9 months of experimental culture under ocean acidification and increasing temperatures (380, 550, 750, 1000 μatm pCO2, and 750, 1000 μatm pCO2 + 2°C) was assessed. Mussel shells grown under ocean acidification conditions displayed significant reductions in shell aragonite thickness, shell thickness index, and changes to shell shape (750, 1000 μatm pCO2) compared to those shells grown under ambient conditions (380 μatm pCO2). Ocean acidification resulted in rounder, flatter mussel shells with thinner aragonite layers likely to be more vulnerable to fracture under changing environments and predation. The changes in shape presented here could present a compensatory mechanism to enhance protection against predators and changing environments under ocean acidification when mussels are unable to grow thicker shells. Here, we present the first assessment of mussel shell shape to determine implications for functional protection under ocean acidification.

opencc-zeroAug 2019View details →

Data from: Twin introductions by independent invader mussel lineages are both associated with recent admixture with a native congener in Australia

Introduced species can impose profound impacts on the evolution of receiving communities with which they interact. If native and introduced taxa remain reproductively semi-isolated, human-mediated secondary contact may promote genetic exchange across newly created hybrid zones, potentially impacting native genetic diversity and invasive species spread. Here, we investigate the contributions of recent divergence histories and ongoing (post-introduction) gene flow between the invasive marine mussel, Mytilus galloprovincialis and a morphologically indistinguishable and taxonomically contentious native Australian taxon, Mytilus planulatus. Using transcriptome-wide markers, we demonstrate that two contemporary M. galloprovincialis introductions into southeastern Australia originate from genetically divergent lineages from its native range in the Mediterranean Sea and Atlantic Europe, where both introductions have led to repeated instances of admixture between introduced and endemic populations. Through increased genome-wide resolution of species relationships, combined with demographic modelling, we validate that mussels sampled in Tasmania are representative of the endemic Australian taxon (M. planulatus), but share strong genetic affinities to M. galloprovincialis. Demographic inferences indicate late-Pleistocene divergence times and historical gene flow between the Tasmanian endemic lineage and northern M. galloprovincialis, suggesting that native and introduced taxa have experienced a period of historical isolation of at least 100,000 years. Our results demonstrate that many genomic loci and sufficient sampling of closely related lineages in both sympatric (e.g., Australian populations) and allopatric (e.g., northern-hemisphere Mytilus taxa) ranges are necessary to accurately (i) interpret patterns of intraspecific differentiation and to (ii) distinguish contemporary invasive introgression from signatures left by recent divergence histories in high dispersal marine species. More broadly, our study fills a significant gap in systematic knowledge of native Australian biodiversity and sheds light on the intrinsic challenges for invasive species research when native and introduced species boundaries are not well-defined.

opencc-zeroDec 2016View details →

Data from: Fluctuating seawater pH/ p CO 2 regimes are more energetically expensive than static pH/ p CO 2 levels in the mussel Mytilus edulis

Ocean acidification (OA) studies typically use stable open-ocean pH or CO2 values. However, species living within dynamic coastal environments can naturally experience wide fluctuations in abiotic factors, suggesting their responses to stable pH conditions may not be reflective of either present or near-future conditions. Here we investigate the physiological responses of the mussel Mytilus edulis to variable seawater pH conditions over short- (6 h) and medium-term (2 weeks) exposures under both current and near-future OA scenarios. Mussel haemolymph pH closely mirrored that of seawater pH over short-term changes of 1 pH unit with acidosis or recovery accordingly, highlighting a limited capacity for acid–base regulation. After 2 weeks, mussels under variable pH conditions had significantly higher metabolic rates, antioxidant enzyme activities and lipid peroxidation than those exposed to static pH under both current and near-future OA scenarios. Static near-future pH conditions induced significant acid–base disturbances and lipid peroxidation compared with the static present-day conditions but did not affect the metabolic rate. These results clearly demonstrate that living in naturally variable environments is energetically more expensive than living in static seawater conditions, which has consequences for how we extrapolate future OA responses in coastal species.

opencc-zeroMar 2024View details →

FIG. 4 in DNA barcoding revealed the presence of the invasive freshwater mussel Sinanodonta aff. woodiana (Lea, 1834) in Afghanistan

FIG. 4. — Median joining network for COI sequences of Sinanodonta aff. woodiana (N = 100; Lineage E (Table 1)). The numbers near branches show the number of mutation sites.

opencc-zeroMar 2024View details →

FIG. 1 in DNA barcoding revealed the presence of the invasive freshwater mussel Sinanodonta aff. woodiana (Lea, 1834) in Afghanistan

FIG. 1. — Map illustrating Amu Darya River position; Point 1 (red circle) indicates sampling site of Sinanodonta aff. woodiana (Lea, 1834) in Amu Darya River in Kunduz Province, Afghanistan.

opencc-zeroJan 2022View details →

Bertalanffy's growth curves of A. anatina duck mussels in 18 Polish lakes with reference to living conditions

1. Post-maturation growth leading to indeterminate growth patterns is widespread in nature. However, its adaptive value is unclear. Life history theory suggests this allocation strategy may be favoured by temporal pulses in the intensity of mortality and/or the capacity to produce new tissues. 2. Addressing the origin of indeterminate growth and the variability of growth patterns, we studied the growth of duck mussels, Anodonta anatina, a pan-European unionid, in 18 Polish lakes. For each population the sex, size and age of collected mussels were measured to estimate Bertalanffy's growth curve parameters. We integrated information on A. anatina mortality rates, lake trophy, biofouling by zebra mussels, Dreissena polymorpha, and the prevalence of parasitic trematode larvae to identify selective conditions in lakes. 3. We found two sources of mortality in A. anatina populations, pertaining to adverse effects of zebra mussel biofouling and trophy state on mussel survival. Additionally, populations with heavier biofouling presented a smaller abundance of parasites, indicative of a relationship between filtering intensity and contraction of water-borne trematode larvae by filtering A. anatina. 4. Consistently for each sex, populations with a greater trophy-related mortality were characterized in A. anatina by a smaller asymptotic size Lmax, indicative of a life history response to mortality risk involving early maturation at a smaller body size. In all populations, females featured higher mortality and larger asymptotic size vs. males. 5. Our findings support a theoretical view that adaptive responses to selection involve adjustments in the lifetime resource allocation patterns. These adjustments should be considered drivers of the origin of indeterminate growth strategy in species taking parental care by offspring brooding in body cavities.

opencc-zeroAug 2022View details →

Declining freshwater mussel diversity in the middle and lower reaches of the Xin River Basin: Threat and Conservation

Freshwater mussels provide important functions and services for aquatic ecosystems, but populations of many species have been extirpated. Information on biodiversity plays an important role in the conservation and management of freshwater mussels. The Xin River Basin is a biodiversity hotspot for freshwater mussels in China, with more than 43 species known, but populations of which are decreasing. Here, we quantify the diversity of freshwater mussels in the middle and lower reaches of the Xin River Basin and study the correlation of habitat characteristics and freshwater mussel diversity. Compared to the historical period, the number of species, density and biomass of freshwater mussels decreased 33%, 83% and 82% in the current period, respectively. 52% of recorded species were empty shells, and 14 native freshwater mussels were not found in the study area. Four species are currently listed as vulnerable species using IUCN criteria and their global status. The assemblage structure of freshwater mussels exhibits significant spatial differences, and there was a correlation with substrate and physicochemical parameters. The main tributary of the Xin River with higher freshwater mussel diversity should be established as one large protected area because the nestedness component was the main pattern of beta diversity. These results indicated freshwater mussel diversity was declining rapidly, which can help focus conservation effort for freshwater mussel biodiversity.

Figure 4 from: Ng PKL, Meyer C (2016) A new species of pea crab of the genus Serenotheres Ahyong & Ng, 2005 (Crustacea, Brachyura, Pinnotheridae) from the date mussel Leiosolenus Carpenter, 1857 (Mollusca, Bivalvia, Mytilidae, Lithophaginae) from the Solomon Islands. ZooKeys 623: 31-41. https://doi.org/10.3897/zookeys.623.10272

Figure 4 - Serenotheres janus sp. n., holotype ♀ (8.9 × 7.9 mm) (USNM). A angled view of cephalothorax B lateral view of cephalothorax C posterior part of dorsal lamellum of carapace and abdominal somites 1–3 D abdominal somites 5, 6 and telson.

Figure 3 from: Ng PKL, Meyer C (2016) A new species of pea crab of the genus Serenotheres Ahyong & Ng, 2005 (Crustacea, Brachyura, Pinnotheridae) from the date mussel Leiosolenus Carpenter, 1857 (Mollusca, Bivalvia, Mytilidae, Lithophaginae) from the Solomon Islands. ZooKeys 623: 31-41. https://doi.org/10.3897/zookeys.623.10272

Figure 3 - Serenotheres janus sp. n., holotype ♀ (8.9 × 7.9 mm) (USNM). Frontal views of cephalothorax.

Figure 2 from: Ng PKL, Meyer C (2016) A new species of pea crab of the genus Serenotheres Ahyong & Ng, 2005 (Crustacea, Brachyura, Pinnotheridae) from the date mussel Leiosolenus Carpenter, 1857 (Mollusca, Bivalvia, Mytilidae, Lithophaginae) from the Solomon Islands. ZooKeys 623: 31-41. https://doi.org/10.3897/zookeys.623.10272

Figure 2 - Serenotheres janus sp. n., holotype ♀ (8.9 × 7.9 mm) (USNM). Dorsal views of cephalothorax.

Figure 6 from: Ng PKL, Meyer C (2016) A new species of pea crab of the genus Serenotheres Ahyong & Ng, 2005 (Crustacea, Brachyura, Pinnotheridae) from the date mussel Leiosolenus Carpenter, 1857 (Mollusca, Bivalvia, Mytilidae, Lithophaginae) from the Solomon Islands. ZooKeys 623: 31-41. https://doi.org/10.3897/zookeys.623.10272

Figure 6 - Serenotheres janus sp. n., holotype ♀ (8.9 × 7.9 mm) (USNM). A outer view of right chela B dorsal view of carpus of right cheliped C–F right P2–P5, respectively. All structures denuded. Scales = 1.0 mm.

Figure 1 from: Ng PKL, Meyer C (2016) A new species of pea crab of the genus Serenotheres Ahyong & Ng, 2005 (Crustacea, Brachyura, Pinnotheridae) from the date mussel Leiosolenus Carpenter, 1857 (Mollusca, Bivalvia, Mytilidae, Lithophaginae) from the Solomon Islands. ZooKeys 623: 31-41. https://doi.org/10.3897/zookeys.623.10272

Figure 1 - Colour in life. Serenotheres janus sp. n., holotype ♀ (8.9 × 7.9 mm) (USNM). A in situ in host date mussel, Leiosolenus obesus B dorsal view C ventral view. Photographs courtesy of Zachariah Kobrinsky and David Liittschwager.

Figure 5 from: Ng PKL, Meyer C (2016) A new species of pea crab of the genus Serenotheres Ahyong & Ng, 2005 (Crustacea, Brachyura, Pinnotheridae) from the date mussel Leiosolenus Carpenter, 1857 (Mollusca, Bivalvia, Mytilidae, Lithophaginae) from the Solomon Islands. ZooKeys 623: 31-41. https://doi.org/10.3897/zookeys.623.10272

Figure 5 - Serenotheres janus sp. n., holotype ♀ (8.9 × 7.9 mm) (USNM). A overall carapace dorsal lamellum B frontal view of cephalothorax (left side denuded) C outer view of right MXP3 and exopod (denuded) D inner view of right MXP3 (denuded) E abdominal somites 4–6 and telson (pits and eroded areas not drawn, left side denuded). Scales: A, B, E = 1.0 mm; C, D = 0.5 mm.

opencc-by-4.0Dec 2018View details →

Figure 1 in Environmental DNA as a tool to help inform zebra mussel, Dreissena polymorpha, management in inland lakes

Figure 1. Sampling locations on Lake Le Homme Dieu (A) and Maple Lake (B) near Alexandria, Minnesota. All locations marked indicate where samples were collected. Pink and white pins indicate the locations where samples were collected in October 2014; We were only able to sample at the locations indicated with pink pins in March 2015 due to the depth of the ice.

opencc-by-4.0Apr 2018View details →

Figure 6 in Populations of Microcondylaea bonellii (Férussac 1827), Unionidae - an european freshwater mussel at rapid decline - and Unio mancus in Istria, Croatia

Figure 6. Adult Microcondylaea bonellii from Butoniga (1.10.2011), note the arboriform siphonal papillae typical for this species.

opencc-by-4.0Apr 2019View details →

Figure 9 in A taxonomic revision of fossil freshwater pearl mussels (Bivalvia: Unionoida: Margaritiferidae) from Pliocene and Pleistocene deposits of Southeastern Europe

Figure 9. Mantle attachment scars on the inner side of subfossil shell of Pseudunio flabellatiformis comb. rev. from the Sucleia outcrop, paleo-Dniester River valley, Middle Pleistocene, Moldova (RMBH, voucher no. Sc5). Scale bar = 10 mm. Photo: Artem A. Lyubas.

opencc-by-4.0Apr 2019View details →

Figure 1 in A taxonomic revision of fossil freshwater pearl mussels (Bivalvia: Unionoida: Margaritiferidae) from Pliocene and Pleistocene deposits of Southeastern Europe

Figure 1. Stratigraphic profile of the Sucleia outcrop, paleo-Dniester River valley, Middle Pleistocene, Moldova. The thickness of outcrop in the studied area is 4.6 m. Layers: (1) 0 -40 cm – light-yellow sand with small pebbles; 2) 40-290 cm – light-brown gravel with gray sand and Pseudunio shells; 3) 290-370 cm – coarse pebble with sand and numerous Pseudunio shells; 4) 370-460 cm – pebble with light-brown sand and Pseudunio shells. Photo: Teodor F. Obada.