Infection by a black spot-causing species of Uvulifer and associated opercular alterations in fishes from a high-desert stream in Wyoming

Black spot is a common disease syndrome of freshwater fishes. This study provides information on the rank of density of the black spot agent and opercular bone alterations associated with at least one digenean, Uvulifer sp., infecting native and non-native catostomids and cyprinids of the Upper Colorado River Basin. We evaluated the density rank of pigmented metacercariae and associated alterations in the operculum of the bluehead sucker Catostomus discobolus, flannelmouth sucker C. latipinnis, white sucker C. commersoni, catostomid hybrids, roundtail chub Gila robusta, and creek chub Semotilus atromaculatus, sampled from Muddy Creek, Wyoming, USA in 2003 or 2004. All fish species contained individuals that exhibited gross signs of the black spot agent. Bluehead and flannelmouth suckers had 100% prevalence of infection. Although the other suckers and chubs contained encysted metacercariae in at least one individual, the presence of pigmented metacercariae was not apparent (i.e. based on gross observations) in many individuals. Catostomids had higher densities of metacercariae than cyprinids, as shown by frequency distributions of density ranks. Opercular holes (i.e. holes that completely penetrated the opercle and were in direct association with the pigment associated metacercariae) and pockets (depressions on the external surface of the opercle associated with metacercariae) were abundant among catostomids but rare among cyprinids.     

Pockets of resistance: Response of arid‐land fish communities to climate,hydrology, and wildfire

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Do non‐native fish as prey favour the conservation of the threatened indigenous Eurasian otter?

1. Biological invasions are considered a major threat to biodiversity. Most research has focused on the distribution, biology and impacts of non‐native species on native fauna and flora. However, few studies have explored their role as prey for native predators of conservation concern. 2. To assess the incidence and intensity of predation by the Eurasian otter Lutra lutra on established non‐native fish species, data were collated from the published literature. To be selected, studies had to cover at least 1 year, analyse more than 100 spraints and report the study period and percentage relative frequency (%RF) of all prey fish species. 3. To permit reliable, time‐related comparisons with %RF of non‐native fishes in otter diet, we also reviewed available information about both the distribution of non‐native fishes and history of their introductions to European countries, revealing a decrease with longitude in the number of naturalised non‐native fishes taken (ranging between 5 and 34) and their percentage in each fish assemblage. 4. Our selective criteria were met by 30 dietary studies from 44 study areas in 15 European countries during 1970–2010. The extent to which otters rely on non‐native fishes was almost negligible (mean %RF = 4.8), with the number of non‐native fishes preyed upon by otters decreasing with both latitude and longitude. 5. The %RF of non‐native fish in the diet increased slightly with time, with otters preying significantly more on non‐native fish in study areas where alterations of the fish assemblage had been highlighted in the reference papers. No relationship was found between otter diet breadth and the occurrence of non‐native fishes in their diet. 6. The current role of non‐native species in otter diet suggests that effective otter conservation management plans should focus on the maintenance and/or enhancement of native fish assemblages.     

Long‐term dynamics of bird diversity in forest and suburb: decay,turnover or homogenization?

Aim Urbanization and deforestation are important drivers of biodiversity change. However, long‐term changes in faunal communities within urbanizing regions are poorly understood. We investigated how well observed community changes in both space and time agree with expectations based on current paradigms in urban ecology. Location Greater Brisbane region, Australia. Methods We compared bird assemblages in two time‐periods 15 years apart, at multiple sites in remnant forest and residential suburbs across an urbanizing landscape. Differences in assemblage composition, species abundances and functional groupings were assessed within and between habitats. Results Compared with forest, suburbs in both time‐periods had over twice the total bird abundance, a different species composition, greater between‐site community similarity, a greater proportion of non‐native species and greater dominance by large‐bodied species. These differences corresponded with changes in sites whose habitat was converted from forest to suburb. Between time‐periods, abundances of 58% of suburban species changed significantly compared with those of 11% in forest. Increaser species outnumbered decreasers in suburbs, with the reverse in forest. Abundance of small‐bodied birds decreased 70% in suburbs and 20% in forest. Broad‐spectrum competitors and nest predators were common among suburban increasers. Among invasive species, the number of increasers was counterbalanced by decreasers. Both site‐scale species richness and between‐site community similarity increased to a small extent in both habitats. Main conclusions Species composition and ecological function of suburban bird communities were very dynamic. Suburban assemblages were neither a subset of forest species nor an increasingly non‐native compilation. Communities in large forest patches were comparatively stable. The notion of habitat‐specific species turnover better characterizes the nature of most changes than either species decline or homogenization, even though both of these were evident. There is considerable scope for careful urban planning, focused on both among‐ and within‐habitat variety, to sustain bird diversity in urbanizing landscapes.     

The distribution and habitat associations of non‐native plant species in urban riparian habitats

Questions: 1. What are the distribution and habitat associations of non‐native (neophyte) species in riparian zones? 2. Are there significant differences, in terms of plant species diversity, composition, habitat condition and species attributes, between plant communities where non‐natives are present or abundant and those where non‐natives are absent or infrequent? 3. Are the observed differences generic to non‐natives or do individual non‐native species differ in their vegetation associations? Location: West Midlands Conurbation (WMC), UK. Methods: 56 sites were located randomly on four rivers across the WMC. Ten 2 m × 2 m quadrats were placed within 15 m of the river to sample vegetation within the floodplain at each site. All vascular plants were recorded along with site information such as surrounding land use and habitat types. Results: Non‐native species were found in many vegetation types and on all rivers in the WMC. There were higher numbers of non‐natives on more degraded, human‐modified rivers. More non‐native species were found in woodland, scrub and tall herb habitats than in grasslands. We distinguish two types of communities with non‐natives. In communities colonized following disturbance, in comparison to quadrats containing no non‐native species, those with non‐natives had higher species diversity and more forbs, annuals and shortlived monocarpic perennials. Native species in quadrats containing non‐natives were characteristic of conditions of higher fertility and pH, had a larger specific leaf area and were less stress tolerant or competitive. In later successional communities dominated by particular non‐natives, native diversity declined with increasing cover of non‐natives. Associated native species were characteristic of low light conditions. Conclusions: Communities containing non‐natives can be associated with particular types of native species. Extrinsic factors (disturbance, eutrophication) affected both native and non‐native species. In disturbed riparian habitats the key determinant of diversity is dominance by competitive invasive species regardless of their native or non‐native origin.     

The effects of development,vegetation‐type conversion,and fire on low‐elevation Southern California spider assemblages

California sage scrub (CSS), a native ecosystem type of low‐elevation areas of Southern California, is increasingly threatened by urban development, altered fire regimes, and vegetation‐type conversion to non‐native grasslands. Using pitfall traps, we examined how suburbanization, type conversion, and fire influence ground‐dwelling spider assemblages in eastern Los Angeles County, CA, by surveying spiders in three habitats (CSS, non‐native grasslands, and suburban areas) before and after a fire that occurred in a small portion of our study site. Spider assemblages in the suburban habitat differed from those in CSS and non‐native grassland habitats, but CSS and grassland assemblages did not significantly differ. This suggests that the urban development, but not vegetation‐type conversion to non‐native grasslands, has significant effects on ground‐dwelling spider assemblages. Fire had no observable effect on assemblages. Because ground‐dwelling spiders were not impacted by fire and type conversion, increased fire frequencies, which often result in the establishment of non‐native grasses, may not deleteriously influence this animal group, a differing pattern from other taxonomic groups. However, the rapid urban development occurring in low‐elevation areas of Southern California means that species requiring non‐suburban sites for their survival (15 species, 24.1%) may be threatened and require conservation assessment.     

Habitat formation prevails over predation in influencing fouling communities

Coastal human‐made structures, such as marinas and harbors, are expanding worldwide. Species assemblages described from these artificial habitats are novel relative to natural reefs, particularly in terms of the abundance of nonindigenous species (NIS). Although these fouling assemblages are clearly distinctive, the ecosystem functioning and species interactions taking place there are little understood. For instance, large predators may influence the fouling community development either directly (feeding on sessile fauna) or indirectly (feeding on small predators associated with these assemblages). In addition, by providing refuges, habitat complexity may modify the outcome of species interactions and the extent of biotic resistance (e.g., by increasing the abundance of niche‐specific competitors and predators of NIS). Using experimental settlement panels deployed in the field for 2.5 months, we tested the influence of predation (i.e., caging experiment), artificial structural complexity (i.e., mimics of turf‐forming species), and their interactions (i.e., refuge effects) on the development of sessile and mobile fauna in two marinas. In addition, we tested the role of biotic complexity—arising from the habitat‐forming species that grew on the panels during the trial—on the richness and abundance of mobile fauna. The effect of predation and artificial habitat complexity was negligible, regardless of assemblage status (i.e., native, cryptogenic, and nonindigenous). Conversely, habitat‐forming species and associated epibionts, responsible for biotic complexity, had a significant effect on mobile invertebrates (richness, abundance, and community structure). In particular, the richness and abundance of mobile NIS were positively affected by biotic complexity, with site‐dependent relationships. Altogether, our results indicate that biotic complexity prevails over artificial habitat complexity in determining the distribution of mobile species under low predation pressure. Facilitation of native and non‐native species thus seems to act upon diversity and community development: This process deserves further consideration in models of biotic resistance to invasion in urban marine habitats.     

Marine dock pilings foster diverse,native cryptobenthic fish assemblages across bioregions

Anthropogenic habitats are increasingly prevalent in coastal marine environments. Previous research on sessile epifauna suggests that artificial habitats act as a refuge for nonindigenous species, which results in highly homogenous communities across locations. However, vertebrate assemblages that live in association with artificial habitats are poorly understood. Here, we quantify the biodiversity of small, cryptic (henceforth “cryptobenthic”) fishes from marine dock pilings across six locations over 35° of latitude from Maine to Panama. We also compare assemblages from dock pilings to natural habitats in the two southernmost locations (Panama and Belize). Our results suggest that the biodiversity patterns of cryptobenthic fishes from dock pilings follow a Latitudinal Diversity Gradient (LDG), with average local and regional diversity declining sharply with increasing latitude. Furthermore, a strong correlation between community composition and spatial distance suggests distinct regional assemblages of cryptobenthic fishes. Cryptobenthic fish assemblages from dock pilings in Belize and Panama were less diverse and had lower densities than nearby reef habitats. However, dock pilings harbored almost exclusively native species, including two species of conservation concern absent from nearby natural habitats. Our results suggest that, in contrast to sessile epifaunal assemblages on artificial substrates, artificial marine habitats can harbor diverse, regionally characteristic assemblages of vertebrates that follow macroecological patterns that are well documented for natural habitats. We therefore posit that, although dock pilings cannot function as a replacement for natural habitats, dock pilings may provide cost‐effective means to preserve native vertebrate biodiversity, and provide a habitat that can be relatively easily monitored to track the status and trends of fish biodiversity in highly urbanized coastal marine environments.     

Are Local Filters Blind to Provenance? Ant Seed Predation Suppresses Exotic Plants More than Natives

The question of whether species’ origins influence invasion outcomes has been a point of substantial debate in invasion ecology. Theoretically, colonization outcomes can be predicted based on how species’ traits interact with community filters, a process presumably blind to species’ origins. Yet, exotic plant introductions commonly result in monospecific plant densities not commonly seen in native assemblages, suggesting that exotic species may respond to community filters differently than natives. Here, we tested whether exotic and native species differed in their responses to a local community filter by examining how ant seed predation affected recruitment of eighteen native and exotic plant species in central Argentina. Ant seed predation proved to be an important local filter that strongly suppressed plant recruitment, but ants suppressed exotic recruitment far more than natives (89% of exotic species vs. 22% of natives). Seed size predicted ant impacts on recruitment independent of origins, with ant preference for smaller seeds resulting in smaller seeded plant species being heavily suppressed. The disproportionate effects of provenance arose because exotics had generally smaller seeds than natives. Exotics also exhibited greater emergence and earlier peak emergence than natives in the absence of ants. However, when ants had access to seeds, these potential advantages of exotics were negated due to the filtering bias against exotics. The differences in traits we observed between exotics and natives suggest that higher-order introduction filters or regional processes preselected for certain exotic traits that then interacted with the local seed predation filter. Our results suggest that the interactions between local filters and species traits can predict invasion outcomes, but understanding the role of provenance will require quantifying filtering processes at multiple hierarchical scales and evaluating interactions between filters.     

Limited contribution of predation by zooplanktivorous cyprinids to 0+ fish mortality

Predation by zooplanktivorous cyprinids was hypothesized as substantially contributing to larval fish mortality. To test this assumption, potential predators were sampled by electric fishing at sites and times of high fish larvae densities in the lower Oder River, Germany, in 2002 and 2003. At ten sites with high prey fish densities, all fishes ≥1+ and 0+ pike – all considered potentially predating on fish larvae – were captured, anaesthetised, and fixed. In the laboratory, 982 guts, respectively, stomachs were dissected and checked for fish larvae and larvae remains. Predation on 0+ fish was detected in the primary piscivorous fishes Esox lucius L. and Aspius aspius (L.), and facultative piscivorous Perca fluviatilis L., whilst none of the other nine species examined consumed fish. These findings implicate that predation by planktivorous cyprinids did not explain the typically strong decline in larval fish densities in the first weeks after hatching.     

Habitat functionality for the ecosystem service of pest control: reproduction and feeding sites of pests and natural enemies

• 1 Landscape management for enhanced natural pest control requires knowledge of the ecological function of the habitats present in the landscape mosaic. However, little is known about which habitat types in agricultural landscapes function as reproduction habitats for arthropod pests and predators during different times of the year.
• 2 We studied the arthropod assemblage on six crops and on the seven most abundant native plant species in two landscapes over 1 year in Australia. Densities of immature and adult stages of pests and their predators were assessed using beat sheet sampling.
• 3 The native plants supported a significantly different arthropod assemblage than crops. Native plants had higher predator densities than crops over the course of the year, whereas crops supported higher pest densities than the native plants in two out of four seasonal sampling periods. Crops had higher densities of immature stages of pests than native plants in three of four seasonal sampling periods, implying that crops are more strongly associated with pest reproduction than native plants. Densities of immature predators, excluding spiders, were not different between native plants and crops. Spiders were, however, generally abundant and densities were higher on native plants than on crops but, because some species disperse when immature, there is less certainty in identifying their reproduction habitat.
• 4 Because the predator to pest ratio on native plant species showed little variation, and spatial variation in arthropod assemblages was limited, the predator support function of native vegetation may be a general phenomenon. Incentives that maintain and restore native remnant vegetation can increase the predator to pest ratio at the landscape scale, which could enhance pest suppression in crops.

     

Spatial and temporal variation in assemblage structure of fish larvae in mediterranean–type streams: contrasts between native and non-native species

Larval fish ecology remains poorly understood in freshwater ecosystems. This study analysed the larval ecology of native and non-native fishes in a mediterranean-type watershed in Southern Iberian Peninsula. Assemblage structure of fish larvae was quantified at four distinct rivers sites, every 2 weeks between March and October 2004, and analysed against 16 variables reflecting river flow, temperature and habitat context. There was considerable spatial variation in taxonomic richness and abundance of larval assemblages, with either native or non-native fishes dominating in different sites. There was also a clear temporal separation between native and non-native fishes, with native cyprinids generally peaking earlier in the year than non-native fishes. Temporal fluctuations in larval assemblages across sites were mostly associated with variations in water temperature and transparency, but flow was an important factor shaping local assemblage structure. Larvae of native fishes appeared to found most suitable conditions in naturally flowing sites early in spring, when flow is high and water temperature stills low. These results suggest that preservation of natural flow peaks and adequate thermal contexts may be crucial for conservation of native fish fauna in mediterranean-type streams.     

Subtle top‐down control of a freshwater meiofaunal assemblage by juvenile fish

1. Top‐down control of prey assemblages by fish predators has been clearly demonstrated in lakes (for zooplankton prey) and rivers (for macroinvertebrate prey). Fish predation can have a significant impact on the body size of prey assemblages; often large‐bodied prey are reduced in abundance, and indirect facilitation of small‐bodied prey occurs potentially initiating a trophic cascade. 2. Benthic communities in aquatic ecosystems also include a numerous and functionally important meiofaunal‐sized component, but in freshwaters the impact of fish predation on meiofaunal assemblages is unknown. We used a laboratory microcosm study to explore the impact of juvenile fish predation on the abundance and size structure of a riverine meiofaunal assemblage. 3. The presence of fish in our microcosms had no significant effect on overall meiofaunal (temporary and permanent) abundance. However, for the Copepoda, we found the first evidence of top‐down control of freshwater meiofaunal assemblages; in microcosms with juvenile fish, the abundance of large‐bodied Copepoda was significantly reduced, whereas small‐bodied Copepoda were significantly more abundant suggesting indirect facilitation. 4. We conclude that predation by juvenile fish can alter the structure of freshwater meiofaunal assemblages, although we do not yet know whether these relatively subtle changes are overwhelmed by large‐scale events such as flow disturbances.     

Local and landscape correlates of non‐native species invasion in restored wetlands

Vulnerability of natural communities to invasion by non‐native plants has been linked to factors such as recent disturbance and high resource availability, suggesting that recently restored habitats may be especially invasible. Because non‐native plants can interfere with restoration goals, monitoring programs should anticipate which sites are most susceptible to invasion and which species are likely to become problematic at a site. Restored sites of larger area and those with high rates of propagule input should have higher species richness of both natives and non‐natives, leading to a positive correlation between the two. However, in restored wetlands, urbanization, riparian landscape settings, and nitrogen enrichment likely favor non‐native relative to native species. We sampled 28 restored wetlands in Illinois, USA, modeled the responses of native richness, non‐native richness and non‐native cover to local and landscape predictors with linear regression, and modeled the presence/absence of 21 non‐native species with logistic regressions. Unexpectedly, native and non‐native richness were uncorrelated, suggesting different responses to environmental factors. Native richness declined with increasing available soil nitrogen and urbanization in the surrounding landscape. Non‐native richness, the richness of non‐natives relative to natives, and the likelihood of invasion by several individual invasive species decreased with increasing distance from the city of Chicago, likely in response to decreasing non‐native propagule pressure. Total cover of non‐natives, however, as well as cover by non‐native Phalaris arundinacea, increased with nitrogen availability. Our results indicate that although non‐native richness was better predicted by factors related to propagule pressure, non‐native species dominance was more closely related to local abiotic factors. Non‐native richness in restoration sites may be beyond the control of restoration practitioners, and furthermore, may be of limited relevance for conservation goals. In contrast, limiting the relative dominance of non‐natives should be a restoration priority and may be achievable through management of nutrient availability.     

Effects of land‐use changes on ecosystem services: decrease in ant predation in human‐dominated landscapes in central Brazil

Anthropogenic disturbances often affect the abundance and diversity of ants (Hymenoptera: Formicidae) but relatively few studies have explored the implications of such changes on the ecosystem services mediated by these insects. Here, we evaluated how the transformation of Cerrado savanna habitats into crop plantations affects the abundance, diversity, and the predatory activity of ants. A survey of the ant faunas foraging above‐ and belowground was performed in six crop and six non‐crop (i.e., native vegetation) sites. Above‐ and belowground rates of ant predation were estimated at these same sites using mealworms, Tenebrio molitor L. (Coleoptera: Tenebrionidae), as baits, simulating crop herbivores. Belowground predation rates were significantly greater in the non‐crop sites, despite the lack of difference in overall abundance and species richness of ants foraging belowground between the crop vs. non‐crop sites. In contrast, we did not detect any significant difference in aboveground predation rates between crop vs. non‐crop sites even though there were significantly more species of ants foraging aboveground in the non‐crop sites. Army ants (subfamily Dorylinae) were the main predatory species belowground, and their abundance was significantly greater in non‐crop sites. In contrast, the main predators aboveground were omnivore ants of the genera Pheidole and Solenopsis, which had similar abundances in the crop and non‐crop sites. Overall, our results indicate that transformation of native Cerrado habitats into crop plantations reduces the abundance of some important predatory species, notably those that forage belowground, and this may negatively affect the potential for ants to provide pest control services in agroecosystems.     

Not all non‐natives are equally unequal: reductions in herbivore β‐diversity depend on phylogenetic similarity to native plant community

Effects of host plant α‐ and β‐diversity often confound studies of herbivore β‐diversity, hindering our ability to predict the full impact of non‐native plants on herbivores. Here, while controlling host plant diversity, we examined variation in herbivore communities between native and non‐native plants, focusing on how plant relatedness and spatial scale alter the result. We found lower absolute magnitudes of β‐diversity among tree species and among sites on non‐natives in all comparisons. However, lower relative β‐diversity only occurred for immature herbivores on phylogenetically distinct non‐natives vs. natives. Locally in that comparison, non‐native gardens had lower host specificity; while among sites, the herbivores supported were a redundant subset of species on natives. Therefore, when phylogenetically distinct non‐natives replace native plants, the community of immature herbivores is likely to be homogenised across landscapes. Differences in communities on closely related non‐natives were subtler, but displayed community shifts and increased generalisation on non‐natives within certain feeding guilds.     

Diurnal dynamics of the microbial loop in peatlands: structure, function and relationship to environmental parameters

Globally, introductions of alien species are increasingly common, with invasive predators potentially having detrimental effects via predation on native species. However, native prey may avoid predation by adopting new behaviors. To determine whether invasive fish populations consume endemic shrimp in invaded Hawaiian anchialine habitats or if adopted patterns of diel migration prevents predation as previously hypothesized, a total of 183 invasive poeciliids (158 Gambusia affinis and 25 Poecilia reticulata) were collected for gut content analyses from four anchialine sites during wet and dry seasons on the islands of Hawai‘i and Maui. Predation on shrimp was not detected in habitats where they retreat exclusively into the underlying aquifer diurnally and only emerge nocturnally. However, low levels of predation were detected (7/65 fishes, only by Gambusia affinis) at Waianapanapa Cave, Maui, where shrimp retreat into both the aquifer and a cave during the day. Thus, adopted behavioral responses to invasive fishes generally, though not universally, prevent predation on endemic Hawaiian anchialine shrimps. However, non-consumptive effects resulting from behavioral modification of shrimps may have appreciable impacts on the Hawaiian anchialine ecosystem and warrant further study.     

Oceanographic coupling across three trophic levels shapes source–sink dynamics in marine metacommunities

A central goal of metapopulation ecology is to determine which subpopulations have the greatest value to the larger metapopulation. That is, where are the ‘sources’ that are most essential to persistence? This question is especially relevant to benthic marine systems, where dispersal and recruitment are greatly affected by oceanographic processes. In a single‐species context, theoretical models typically identify ‘hotspots’ with high recruitment, especially high self‐recruitment, as having the highest value. However, the oceanographic forces affecting larval delivery of a given species may also influence the recruitment of that species’ predators, prey, and competitors.We present evidence from the Virgin Islands and Bahamas that oceanographic forces produce spatial coupling between the recruitment of planktivorous fishes, the recruitment of their predators, and the productivity of their zooplankton prey. We examined the consequences of this type of multi‐trophic coupling using a simple analytical population model and a multispecies numerical simulation model with parameter values based on the Virgin Islands system. In both analyses, strong coupling caused planktivores at the highest recruitment sites to experience higher mortality (a consequence of higher predator densities) but faster growth and higher fecundity (a consequence of higher zooplankton densities) than planktivores at low recruitment sites. As such, the relative strength of oceanographic coupling between the three trophic levels strongly determined whether a particular reef acted as a source or sink. In the simulation model, density‐dependent competition for zooplankton limited overall metapopulation biomass more severely than predation, so oceanographic coupling between planktivore larval supply and zooplankton productivity had a stronger effect on the metapopulation value of a patch. We argue that the potential for such tri‐trophic coupling should be incorporated into future metacommunity models and has considerable implications for the design and evaluation of marine reserves.     

Habitat Restoration as a Means of Controlling Non-Native Fish in a Mojave Desert Oasis

Non‐native fish generally cause native fish decline, and once non‐natives are established, control or elimination is usually problematic. Because non‐native fish colonization has been greatest in anthropogenically altered habitats, restoring habitat similar to predisturbance conditions may offer a viable means of non‐native fish control. In this investigation we identified habitats favoring native over non‐native fish in a Mojave Desert oasis (Ash Meadows) and used this information to restore one of its major warm water spring systems (Kings Pool Spring). Prior to restoration, native fishes predominated in warm water (25–32°C) stream and spring‐pool habitat, whereas non‐natives predominated in cool water (≤23°C) spring‐pool and marsh/slack water habitat. Native Amargosa pupfish (Cyprinodon nevadensis) and Ash Meadows speckled dace (Rhinichthys osculus nevadensis) inhabited significantly faster mean water column velocities (MWCV) and greater total depth (TD) than non‐native Sailfin molly (Poecilia latipinna) and Mosquitofish (Gambusia affinis) in warm water stream habitat, and Ash Meadows speckled dace inhabited significantly faster water than non‐natives in cool water stream habitat. Modification of the outflow of Kings Pool Spring from marsh to warm water stream, with MWCV, TD, and temperature favoring native fish, changed the fish composition from predominantly non‐native Sailfin molly and Mosquitofish to predominantly Ash Meadows pupfish. This result supports the hypothesis that restoring spring systems to a semblance of predisturbance conditions would promote recolonization of native fishes and deter non‐native fish invasion and proliferation.     

Predation drives recurrent convergence of an interspecies mutualism

Mutualisms are important ecological interactions that underpin much of the world's biodiversity. Predation risk has been shown to regulate mutualism dynamics in species‐specific case studies; however, we lack studies which investigate whether predation can also explain broader patterns of mutualism evolution. We report that fish‐anemone mutualisms have evolved on at least 55 occasions across 16 fish families over the past 60 million years and that adult body size is associated with the ontogenetic stage of anemone mutualisms: larger‐bodied species partner with anemones as juveniles, while smaller‐bodied species partner with anemones throughout their lives. Field and laboratory studies show that predators target smaller prey, that smaller fishes associate more with anemones, and that these relationships confer protection to small fishes. Our results indicate that predation is likely driving the recurrent convergent evolution of fish‐anemone mutualisms and suggest that similar ecological processes may have selected convergence in interspecies interactions in other animal clades.