Phylogenomic reconstruction illuminates the evolutionary history of freshwater to marine transition in the subfamily Haloveliinae ( Hemiptera: Heteroptera: Veliidae )

One of the most dominant concepts in invasion ecology is the stage-based invasion model, consisting of transport, introduction, establishment and spread. Many species fail at one of the stages, with propagule pressure (i.e. number of introduced individuals) identified as a principal factor affecting establishment success. Population characteristics such as phenotypic plasticity and beneficial life history traits may facilitate successful transition of species through different stages of the process; however, studies on the latter are not so common and most of those studies focus on terrestrial taxa. In this study, we hypothesized seven life history traits that may be beneficial for invasion success of aquatic species, and determined those traits for established non-indigenous species (NIS) in the North and Baltic Seas (i.e. marine environment) and Great Lakes-St. Lawrence River regions (i.e. freshwater environment). This is the first study that examined certain life history traits of all NIS established in particular regions, as well as compared those traits between marine and freshwater habitats. Our study determined some differences in life history traits between NIS in the marine and freshwater habitats. Those differences were connected to different taxonomic groups that were dominant NIS in these two types of habitats. Furthermore, species originating from different donor regions had also different life history traits. The majority of NIS in both regions were r-strategists. There was a significantly higher number of NIS that were able to reproduce both asexually and sexually and to produce dormant stages in the freshwater than in marine habitat. Finally, as r-strategy, asexual reproduction and dormancy were dominant traits of NIS in the freshwater habitat, freshwater ecosystems may be under greater invasion risk than marine ones, as those traits reduce both demographic and environmental stochasticity during the invasion process.

Over the last two decades, there has been increasing public and political recognition of society's dependency upon natural habitat complexity and ecological processes to sustain provision of crucial ecosystem services, ranging from supplying potable water through to climate regulation. How has the ecosystem‐services perspective been integrated into strategies for aquatic habitat conservation? Literature on conservation of diverse freshwater and marine habitats was reviewed to assess the extent to which past and current strategies specifically targeted ecosystem services, and considered ecosystem functions, potential trade‐offs and social issues when formulating protection measures for conserving aquatic habitats. Surprisingly few published examples exist where comprehensive assessment of ecosystem services supported development of conservation plans. Seldom were aquatic habitat conservation objectives framed in terms of balancing trade‐offs, assessing social values and evaluating suites of ecosystem services under different strategies. Time frames for achieving these objectives were also rarely specified. There was no evidence for fundamental differences between marine and freshwater habitats with respect to their ecosystem services that should be considered when setting targets for their conservation. When an ecosystem‐service perspective is used for setting objectives in aquatic habitat conservation, the following actions are recommended: (1) explicitly listing and evaluating full suites of ecosystem services to be conserved; (2) identifying current and future potential trade‐offs arising from conservation; (3) specifying time frames within which particular strategies might protect or enhance desired services; and (4) predicting how different proposed strategies might affect each ecosystem function, service flow and public benefit. This approach will help ensure that less‐apparent ecosystem services (e.g. regulating, supporting) and their associated ecosystem functions receive adequate recognition and protection in aquatic conservation of freshwater and marine habitats. However, conservation objectives should not focus solely on protecting or enhancing ecosystem services but complement current strategies targeting biodiversity and other conservation goals. Copyright © 2016 John Wiley & Sons, Ltd.

Migratory shorebirds show strong dichotomies in habitat choice during both the breeding and nonbreeding season. Whereas High Arctic breeding species are restricted to coastal marine and saline habitats during the nonbreeding season, more southerly breeding species tend to use freshwater habitats away from coasts. It has been proposed that this co‐variation in habitat use is a consequence of a single axis of adaptation to pathogens and parasites, which are hypothesized to be relatively scarce in High Arctic, marine, and saline habitats and relatively common at lower latitudes and in freshwater habitats. Here we examine this contrast by comparing the prevalence of avian malaria infections in shorebirds occupying different habitats. We used a PCR‐based assay on 1319 individuals from 31 shorebird species sampled in the Arctic, in temperate Europe and in inland and marine habitats in West Africa. Infections mainly occurred in tropical wetlands, with the shorebirds in freshwater inland habitats having significantly higher prevalence of malaria than birds in marine coastal habitats. Infections were not found in birds migrating through Europe even though conspecifics did show infections in tropical Africa. Adults should resist infection better than juveniles, but showed higher malaria prevalence, suggesting that infection probability increases with cumulative exposure. We argue that exposure to vectors is the main factor explaining the habitat‐related differences in malaria prevalence.

Record low run sizes of Chum salmon (Oncorhynchus keta) were observed in western Alaska from 2020 to 2022 following marine heat waves (extreme events) that occurred in their early marine and winter ocean habitats. Climate warming impacts on Arctic-Yukon-Kuskokwim (AYK) Chum salmon ecology in freshwater and marine habitats is a shared concern among Alaskan communities. The life history of AYK Chum salmon includes a short period within freshwater habitats, where adults spawn during fall months, eggs hatch during early spring the following year, and smolts leave freshwater and enter the marine environment during late spring and early summer (Urawa et al. 2018). During their first summer at sea, they are found feeding and growing within the shelf regions of the northern and southern Bering Sea as well as the Chukchi Sea. During late fall and winter, they migrate offshore where they overwinter in the Gulf of Alaska (GOA) and eastern North Pacific Ocean (NPO; Myers et al. 2007). They continue their migratory pattern of wintering in the GOA and eastern NPO and summering in the Bering Sea and western GOA for one or more years before migrating back to their natal rivers during spring to begin the cycle again (Fig. 1).

The feeding ecology and distribution of the Common Kingfisher Alcedo atthis has been extensively studied during the breeding season in European freshwater habitats, but there is much less known about the ecology of this species in marine and brackish habitats. This study aims to (1) document the presence of Common Kingfishers in marine habitats of Galicia (NW Spain), based on a database of bird sightings collected in mainland Galicia (2004–2020) and on the Cíes Islands (Coast of Galicia; 2008–2019), and (2) study their diet in marine habitats, analyzing 17 pellets collected during autumn and winter in a coastal salt lagoon on the Cíes Islands. During autumn and winter, the number of observations of the species in mainland Galicia were higher in marine habitats than in freshwater habitats (χ21 = 10.88, P < 0.001). Moreover, Common Kingfishers visit the Cíes Islands mostly during autumn and winter (98.6% of observations). Both datasets show that marine habitats are very important for wintering birds. In the coastal lagoon on the Cíes Islands, the Common Prawn Palaemon serratus was the most frequent prey (41.7%), accounting for the highest percentage of the total biomass (68%); much more than the second most frequent prey, gobies (Gobiidae; 35.5%). This finding is exceptional in Europe, since only a few studies report shrimp as a prey item for Common Kingfishers, probably due to the lack of data from marine habitats during winter.

The Eocene–Oligocene sea‐level fall has been viewed as a primary driver of biological succession. We used Anisogammaridae living in both marine and freshwater habitats to test the hypothesis that Eocene–Oligocene sea‐level fall can explain the marine–freshwater habitat shift in the Far East. We obtained three mitochondrial and two nuclear fragments for 138 samples representing 31 species, covering marine and freshwater habitats from latitudes 24 to 50°N. The phylogenetic analyses revealed that freshwater Anisogammaridae is monophyletic. Divergence‐time estimation and ancestral range reconstruction indicate that the family originated from a marine habitat in the North Pacific region during the Eocene and separated between marine and freshwater lineages at 38 Ma. The freshwater lineage diversified at 27 Ma, and further diverged into lotic and lentic clades. Our results suggest that the Eocene–Oligocene sea‐level fall provided an opportunity for marine‐derived Anisogammaridae to shift to new freshwater habitats. The freshwater anisogammarids dispersed from north to south, resulting in the restriction of current marine species restricted to the latitudes 35–50°N and the range of freshwater species in latitudes 24–40°N. Deep divergences within the freshwater lineage were related to the separation of lotic and lentic environments and the opening of the Japan Sea.

Strategies for optimizing fitness in a dilute, competitive, and changing environment are thought to underlie cell size evolution in phytoplankton. Support for cell size as an adaptive trait comes from observed shifts in cell size distributions in response to environmental cues at geologic time scales and across environmental gradients. Physicochemical differences between marine and freshwater environments are thought to drive diatom cell size evolution in opposite directions, with larger sizes conferring benefits in marine habitats and small sizes in freshwater habitats. We tested this hypothesis in one lineage of diatoms, the Thalassiosirales, which spans marine and freshwater habitats, has a well‐supported phylogeny, and whose members are relatively homogenous with respect to cell shape, growth habit, and habitat preference. A comparison of adaptive models for cell size evolution supports the hypothesis for different cell size optima between marine and freshwater habitats. The data are best explained by a model with separate selective regimes for marine and freshwater lineages. However, a scenario of stabilizing selection towards a single global cell size optimum irrespective of habitat cannot be completely discounted. Understanding of the processes that shape cell size evolution in phytoplankton would benefit from models that incorporate phylogeny, intrinsic properties of species (e.g., cell shape, colony formation, and motility), and more specific habitat characterization, as well as genetic and genomic properties of different phytoplankton groups.

AimTo assess how climate change may decouple the ecosystems used by a migratory fish, and how decoupling influences priorities for stream restoration.LocationAustralia.MethodsWe modelled changes in habitat suitability under climate change in both riverine and marine habitats for a threatened diadromous species, the Australian Grayling Prototroctes maraena, using niche models. The loss of riverine habitats for Grayling was compared with or without considering the impact of climate change on adjacent marine habitats. We also asked whether considering marine climate change changed the locations where removing dams had the greatest benefit for Grayling conservation.ResultsClimate change is expected to cause local extinction in both marine and river habitats regardless of whether dams are retained or removed at the trailing edge of the Grayling's range (north‐eastern). Decoupling of habitats was most apparent in the eastern and south‐eastern portion of the Grayling's range, where ocean warming may cause a decline in the suitability of marine habitats for larvae, while many freshwater habitats retained suitable habitat for adults. Removing dams to restore connectivity between ocean and freshwater habitats was predicted to have the greatest benefit for Grayling in southern portions of their range. Under climate change, the priorities for barrier removal gradually shift towards dams at higher elevation because of increasing suitability of freshwater habitats at higher elevations.Main conclusionsOur study highlights the importance of assessing climate range shifts in multiple ecosystems for migratory species and can help inform priorities for stream restoration under a changing climate.

Wood is a major carbon input into aquatic ecosystems and is thought to decay slowly, yet surprisingly little terrestrial carbon accumulates in marine sediments. A better mechanistic understanding of how habitat conditions and decomposer communities influence wood decay processes along the river-estuary-ocean continuum can address this seeming paradox. We measured mass loss, wood element, and polymer concentrations, quantified invertebrate-induced decay, and sequenced fungal communities associated with replicate sections of Guazuma branch wood submerged in freshwater, estuarine, and near-shore marine habitats and placed on the soil surface in nearby terrestrial habitats in three watersheds in the tropical eastern Pacific. Over 15months, we found that wood decayed at similar rates in estuarine, marine, and terrestrial sites, reflecting the combined activity of invertebrate and microbial decomposers. In contrast, in the absence of shipworms (Teredinidae), which accounted for ~40% of wood mass loss in the estuarine habitats, decay proceeded more slowly in freshwater. Over the experiment, wood element chemistry diverged among freshwater, estuarine, and marine habitats, due to differences in both nutrient losses (e.g., potassium and phosphorus) and gains (e.g., calcium and aluminum) through decay. Similarly, we observed changes in wood polymer content, with the highest losses of cellulose, hemicellulose, and lignin moieties in the marine habitat. Aquatic fungal communities were strongly dominated by ascomycetes (88-99% of taxa), compared to terrestrial communities (55% ascomycetes). Large differences in fungal diversity were also observed across habitats with threefold higher richness in terrestrial than freshwater habitats and twofold higher diversity in freshwater than estuarine/marine habitats. Divergent decay trajectories across habitats were associated with widespread order-level differences in fungal composition, with distinct communities found in freshwater, estuarine and marine habitats. However, few individual taxa that were significantly associated with mass loss were broadly distributed, suggesting a high level of functional redundancy. The rapid processing of wood entering tropical rivers by microbes and invertebrates, comparable to that on land, indicates that estuaries and coastal oceans are hotspots not just for the processing of particulate and dissolved organic carbon, but also for woody debris and for the breakdown of lignin, the most recalcitrant polymer in plant tissue.

The diversity of species inhabiting freshwater relative to marine habitats is striking, given that freshwater habitats encompass <1% of Earth's water. The most commonly proposed explanation for this pattern is that freshwater habitats are more fragmented than marine habitats, allowing more opportunities for allopatric speciation and thus increased diversification rates in freshwater. However, speciation may be generally faster in sympatry than in allopatry, as illustrated by lacustrine radiations such as African cichlids. Such differences between rivers and lakes may be important to consider when comparing diversification broadly among freshwater and marine groups. Here I compared diversification rates of teleost fishes in marine, riverine and lacustrine habitats. I found that lakes had faster speciation and net diversification rates than other aquatic habitats. However, most freshwater diversity arose in rivers. Surprisingly, riverine and marine habitats had similar rates of net diversification on average. Biogeographic models suggest that lacustrine habitats are evolutionarily unstable, explaining the dearth of lacustrine species in spite of their rapid diversification. Collectively, these results suggest that strong diversification rate differences are unlikely to explain the freshwater paradox. Instead, this pattern may be attributable to the comparable amount of time spent in riverine and marine habitats over the 200-million-year history of teleosts.

The European Red List of Habitats provides an overview of the risk of collapse (degree of endangerment) of marine, terrestrial and freshwater habitats in the European Union (EU28) and adjacent regions (EU28+), based on a consistent set of categories and criteria, and detailed data and expert knowledge from involved countries1. A total of 257 benthic marine habitat types were assessed. In total, 19% (EU28) and 18% (EU28+) of the evaluated habitats were assessed as threatened in categories Critically Endangered, Endangered and Vulnerable. An additional 12% were Near Threatened in the EU28 and 11% in the EU28+. These figures are approximately doubled if Data Deficient habitats are excluded. The percentage of threatened habitat types differs across the regional seas. The highest proportion of threatened habitats in the EU28 was found in the Mediterranean Sea (32%), followed by the North-East Atlantic (23%), the Black Sea (13%) and then the Baltic Sea (8%). There was a similar pattern in the EU28+. The most frequently cited pressures and threats were similar across the four regional seas: pollution (eutrophication), biological resource use other than agriculture or forestry (mainly fishing but also aquaculture), natural system modifications (e.g. dredging and sea defence works), urbanisation and climate change. Even for habitats where the assessment outcome was Data Deficient, the Red List assessment process has resulted in the compilation of a substantial body of useful information to support the conservation of marine habitats.

The diet of otters was studied in closely associated freshwater, brackish and marine habitats, from spraints collected on the Portuguese south‐west coast over an 18‐month period. In areas where marine prey was the only available resource, diet was dominated by blennies, wrasses and gobies, but other prey was taken in areas near coastal lagoons, marshes and estuaries. Eels and amphibians were considered the typical prey of freshwater habitats, and grey mullet the typical prey of brackish water habitats. If the inland habitats near the coast were large enough, otters preferred to forage there rather than in the sea. In one area where otters alternatively used marine and inland habitats, the former were used most extensively in autumn and winter, and the latter in spring and summer. It is suggested that otters prefer to forage inland rather than in the sea.

Kånneby, T., Todaro, M. A., Jondelius, U. (2012). Phylogeny of Chaetonotidae and other Paucitubulatina (Gastrotricha: Chaetonotida) and the colonization of aquatic ecosystems. —Zoologica Scripta, 42, 88–105.Chaetonotidae is the largest family within Gastrotricha with almost 400 nominal species represented in both freshwater and marine habitats. The group is probably non‐monophyletic and suffers from a troubled taxonomy. Current classification is to a great extent based on shape and distribution of cuticular structures, characters that are highly variable. We present the most densely sampled molecular study so far where 17 of the 31 genera belonging to Chaetonotida are represented. Bayesian and maximum likelihood approaches based on 18S rDNA, 28S rDNA and COI mtDNA are used to reconstruct relationships within Chaetonotidae. The use of cuticular structures for supra‐specific classification within the group is evaluated and the question of dispersal between marine and freshwater habitats is addressed. Moreover, the subgeneric classification of Chaetonotus is tested in a phylogenetic context. Our results show high support for a clade containing Dasydytidae nested within Chaetonotidae. Within this clade, only three genera are monophyletic following current classification. Genera containing both marine and freshwater species never form monophyletic clades and group with other species according to habitat. Marine members of Aspidiophorus appear to be the sister group of all other Chaetonotidae and Dasydytidae, indicating a marine origin of the clade. Halichaetonotus and marine Heterolepidoderma form a monophyletic group in a sister group relationship to freshwater species, pointing towards a secondary invasion of marine environments of these taxa. Our study highlights the problems of current classification based on cuticular structures, characters that show homoplasy for deeper relationships.

Fatty acid composition of brain and body phospholipids of the anadromous salmon, Oncorhynchus nerka, From fresh-water and marine habitat

Diadromy, broadly defined here as the regular movement between freshwater and marine habitats at some time during their lives, characterizes numerous fish and invertebrate taxa. Explanations for the evolution of diadromy have focused on ecological requirements of individual taxa, rarely reflecting a comparative, phylogenetic component. When incorporated into phylogenetic studies, center of origin hypotheses have been used to infer dispersal routes. The occurrence and distribution of diadromy throughout fish (aquatic non-tetrapod vertebrate) phylogeny are used here to interpret the evolution of this life history pattern and demonstrate the relationship between life history and ecology in cladistic biogeography. Cladistic biogeography has been mischaracterized as rejecting ecology. On the contrary, cladistic biogeography has been explicit in interpreting ecology or life history patterns within the broader framework of phylogenetic patterns. Today, in inferred ancient life history patterns, such as diadromy, we see remnants of previously broader distribution patterns, such as antitropicality or bipolarity, that spanned both marine and freshwater habitats. Biogeographic regions that span ocean basins and incorporate ocean margins better explain the relationship among diadromy, its evolution, and its distribution than do biogeographic regions centered on continents.