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Characterizing ecosystem-level consequences of biological invasions: The role of ecosystem engineers
Abstract
Invasions by exotic species represent both threats to ecosystems as well as opportunities to learn more about them. Among the invaders that will have the largest impacts are those that directly modify ecosystems and thus have cascading effects for resident biota. Exotics can affect ecosystems by altering system-level flows, availability, or quality of nutrients, food, and physical resources (e.g. living space, water, heat or light). The invader-mediated control of physical resources, typically achieved through the modification of habitats, has received limited attention in invasion biology. This reflects a general trend in ecology, and only recently has the concept of ecosystem engineering been developed to account for the role of species that shape habitats. Plants and animals in terrestrial and aquatic systems can both create and destroy structure. When introduced into ecosystems, these exotic engineers cause physical state changes with effects that ramify throughout the system. Although the consequences of these modifications are varied and complex, insight gained from general ecological principles offers an opportunity to predict what invaders will do upon their integration into systems. Examples from the literature suggest that introduced ecosystem engineers that increase habitat complexity or heterogeneity tend to cause abundances and/or species richness to rise, while those that decrease complexity tend to have the reverse effect. In assessing such patterns, however, it is critical to also consider spatial scales and the life habits of resident organisms. In addition to providing predictive power, recognition of engineering as a major means by which invasive species affect ecosystems provides a unifying theme for invasion biology and offers a chance to consider more fully the general role of species in ecosystems.
... This means that we can expect a strong positive effect of the engineer on richness at the landscape scale when the quality or quantity of engineered patches support species that could not survive otherwise. In a literature review, Crooks (2002) suggests that the heterogeneity-niches relationship can be used to predict the impact of exotic engineers: if they increase habitat complexity or heterogeneity they tend to cause abundances and/or species richness to rise (e.g. Davoult et al., 2017), while those that decrease complexity tend to have the reverse effect. ...
... Similarly, our review suggests that species richness and network complexity can stay largely unchanged, be increased or reduced when exotic engineers arrive in a new habitat. Again, this depends on the impact by the exotic engineer either increasing or decreasing habitat heterogeneity or nutrient availability (Crooks, 2002). For example, the algae Didymosphenia geminate reaches large densities when settles as invasive species. ...
Ecosystem engineering is a ubiquitous process where species influence the physical environment and thereby structure ecological communities. However, there has been little effort to synthesize or predict how ecosystem engineering may impact the structure and stability of interaction networks.
To assess current scientific understanding of ecosystem engineering impacts via habitat forming, habitat modification and bioturbation on interaction networks/food webs, we reviewed the literature covering marine, freshwater and terrestrial food webs, plant‐pollinator networks and theory.
We provide a conceptual framework and identify three major pathways of engineering impact on networks through changes in resource availability and energy flow, habitat heterogeneity and environmental filtering. These three processes often work in concert and most studies report that engineering increases species richness. This is particularly marked for engineers that increase habitat heterogeneity and thereby the number of available niches.
The response of network structure to ecosystem engineering varies, however some patterns emerge from this review. Engineered habitat heterogeneity leads to a higher number of links between species in the networks and increases link density. Connectance can be negatively or positively affected by ecosystem engineer impact, depending on the engineering pathway and the engineer impact of species richness.
We discuss how ecosystem engineers can stabilize or destabilize communities through the changes in niche space, diversity, network structure and the dependency on the engineering impact. Theory and empirical evidence need to inform each other to better integrate ecosystem engineering and ecological networks. A mechanistic understanding how ecosystem engineering traits shape interactions networks and their stability will be important to predict species extinctions and can provide crucial information for conservation and ecosystem restoration.
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... Nevertheless, in coastal ecosystems of Hawai'i, mangroves have resulted in a range of adverse ecological and economic consequences: Mangroves tend to thrive in holotypic ecotones, which leads to their proliferation in estuarine environments, where their root systems can impede the flushing and circulation of fishponds [4,23,24]. Further, areas vegetated with mangroves have high sedimentation rates changing sandy habitats into muddy anoxic sediments as a result of bacterial decomposition of mangrove leaf detritus [23,25,26]. Drawdown of nitrogen and phosphate in areas with mangroves can lead to a decline of dissolved oxygen that can inhibit primary production rates in fishponds [25]. ...
... At Nuʻupia Ponds Wildlife Management Area, mangroves have been documented to overgrow mudflats, causing heavy sedimentation and inhibiting flux as well as threatening the physical integrity and function of fishpond walls and channels [11]. Thus, removal of non-native mangroves (Rhizophora mangle) has been part of 26 management plans in the past [11,24]. Pickleweed (Batis maritima) is an introduced colonizer of mudflats and fishponds forming a monotypic salt marsh vegetation diminishing habitat for native seabirds [11,27]. ...
Nuʻupia Ponds, a traditional Hawaiian fishpond system, are located at Marine Corps Base Hawaii (MCBH) and part of the Nuʻupia Ponds Wildlife Management Area, a wetland refuge for native, endangered, and protected birds and Hawaiian green sea turtles, as well as many native fish species. Currently, there is uncertainty regarding the ecological status and condition of the fishponds following prior modification of wetland habitats in and around the ponds. This study examines circulation dynamics and characterizes water exchange, pond volume, and residence time across the full tidal spectrum at Nuʻupia fishponds. Our results indicate a general west to east gradient in current flow; with higher flushing rates and lower residence times of fishponds in the western ponds of the Nu’upia system compared to the eastern ponds. We further found low flushing rates at several sites causing limited water exchange with Kāne’ohe Bay, as well as within Nu’upia Pond system. Sufficient water circulation plays a fundamental role in maintaining a healthy balance of fishpond flora and fauna and preserve ecosystem health. The results from this study provide a baseline of current physical water circulation dynamics and implications for ecosystem health, as well as inform science-based conservation and management strategies moving forward.
... The impacts of biological invasions can be extensive and often detrimental to native ecosystems (Pyšek et al. 2020). Invasive species can disrupt food webs (Wainright et al. 2021), alter habitats (Crooks 2002;Guy-Haim et al. 2018), displace native species (Catford et al. 2018), cause biodiversity loss (Pyšek et al. 2020), alter ecosystem functioning (Haubrock et al. 2021), and lead to significant social and economic impacts (Simberloff et al. 2013;Diagne et al. 2020). Invasive species can also out-compete native species for resources (Catford et al. 2018;Ferreira-Rodríguez et al. 2018), leading to a decline in diversity (Mollot et al. 2017; Williams-Subiza and Epele 2021) that can affect the entire ecosystem and affect various taxonomic groups that are directly or indirectly linked to them (Crooks 2002;Guy-Haim et al. 2018;Goedknegt et al. 2020;Vivó-Pons et al. 2020). ...
... Invasive species can disrupt food webs (Wainright et al. 2021), alter habitats (Crooks 2002;Guy-Haim et al. 2018), displace native species (Catford et al. 2018), cause biodiversity loss (Pyšek et al. 2020), alter ecosystem functioning (Haubrock et al. 2021), and lead to significant social and economic impacts (Simberloff et al. 2013;Diagne et al. 2020). Invasive species can also out-compete native species for resources (Catford et al. 2018;Ferreira-Rodríguez et al. 2018), leading to a decline in diversity (Mollot et al. 2017; Williams-Subiza and Epele 2021) that can affect the entire ecosystem and affect various taxonomic groups that are directly or indirectly linked to them (Crooks 2002;Guy-Haim et al. 2018;Goedknegt et al. 2020;Vivó-Pons et al. 2020). Additionally, climate change is likely to exacerbate the impacts of biological invasions (Rahel and Olden 2008;Diez et al. 2012;Bellard et al. 2013), as rising temperatures and changes in precipitation regimes create new opportunities for the establishment of non-native species in new areas (Stachowicz et al. 2002;McKnight et al. 2021;Souza et al. 2022b). ...
As the effects of climate change continue to intensify, non-native species are becoming more prevalent in estuarine ecosystems. This has implications for the taxonomic and functional diversity of fish communities. Historically, biodiversity has been a synonym of taxonomic diversity, however this approach often fails to provide accurate insights on ecosystem functioning and resilience. To better understand how climate change is impacting fishes and their traits’ composition, a long-term dataset from Minho Estuary (NW Iberian Peninsula) fish assemblage was analyzed. The results suggest that climate change and extreme weather events altered the prevailing trait modalities of fishes, which led to the overall decrease in functional diversity of the fish assemblage over the course of a decade. This decrease is associated to the loss of some trait modalities that are exclusively found in native species. On the other hand, the invasive species added novel traits associated with the conditions of high temperatures and low precipitation regime currently observed in the studied area. Our results highlight that the shift in the presence and dominance of some traits is directly influenced by climatic changes. Also, despite the addition of novel modalities by the invasive species, the fish assemblage is now less functional and taxonomically diverse than previously.
Graphical abstract
... Even when such data do exist, per capita impacts may not scale up to statistically detectable community shifts when the overall invasive population size remains relatively small [2]. Additionally, assessment of impacts can "lag" behind their occurrence if impacted species have not yet had enough time to incur detectable demographic shifts (e.g., changes in vital rates; [3,4]). Yet gauging impacts early in the invasion process can buy managers valuable time in prioritizing limited resources to geographies or habitats before they incur dramatic losses [5]. ...
Predation by invasive species can threaten local ecosystems and economies. The European green crab (Carcinus maenas), one of the most widespread marine invasive species, is an effective predator associated with clam and crab population declines outside of its native range. In the U.S. Pacific Northwest, green crab has recently increased in abundance and expanded its distribution, generating concern for estuarine ecosystems and associated aquaculture production. However, regionally-specific information on the trophic impacts of invasive green crab is very limited. We compared the stomach contents of green crabs collected on clam aquaculture beds versus intertidal sloughs in Willapa Bay, Washington, to provide the first in-depth description of European green crab diet at a particularly crucial time for regional management. We first identified putative prey items using DNA metabarcoding of stomach content samples. We compared diet composition across sites using prey presence/absence and an index of species-specific relative abundance. For eight prey species, we also calibrated metabarcoding data to quantitatively compare DNA abundance between prey taxa, and to describe an ‘average’ green crab diet at an intertidal slough versus a clam aquaculture bed. From the stomach contents of 61 green crabs, we identified 54 unique taxa belonging to nine phyla. The stomach contents of crabs collected from clam aquaculture beds were significantly different from the stomach contents of crabs collected at intertidal sloughs. Across all sites, arthropods were the most frequently detected prey, with the native hairy shore crab (Hemigrapsus oregonensis) the single most common prey item. Of the eight species calibrated with a quantitative model, two ecologically-important native species–the sand shrimp (Crangon franciscorum) and the Pacific staghorn sculpin (Leptocottus armatus)–had the highest average DNA abundance when detected in a stomach content sample. In addition to providing timely information on green crab diet, our research demonstrates the novel application of a recently developed model for more quantitative DNA metabarcoding. This represents another step in the ongoing evolution of DNA-based diet analysis towards producing the quantitative data necessary for modeling invasive species impacts.
... However, amphibians are facing multiple stressors, like climate change and habitat modification, that might result in conflicting effects on how canopy coverage affects survival. In recent decades, many regions have experienced trends towards increased canopy coverage caused by climate change (Mantyka-Pringle et al., 2015;Song et al., 2018) and the spread of invasive flora (Crooks, 2002;Watling et al., 2011). In a warming climate, increased shade from a denser canopy could potentially help prevent amphibians from overheating or desiccating, but it might also result in the reduction of warm microhabitats needed for proper thermoregulation, especially in temperate regions (Kearney et al., 2009). ...
... Freshwater ecosystems have been particularly affected by the abiotic and biotic effects of invasive species (Darwall et al. 2018), where the rate of species loss has exceeded those observed in terrestrial systems (Ricciardi and Rasmussen 1999;Albert et al. 2021). Invasive species may harm native fauna and ecosystems indirectly by altering habitat conditions (Crooks 2002;Strayer 2010) or directly through biotic interactions that have cascading effects throughout the food web (Gallardo et al. 2016). Significant community-wide consequences might manifest also due to the evolutionary isolated and at times species-deprived states of freshwater systems (Cox and Lima 2006), particularly in isolated, oligotrophic pre-alpine lakes where species may be vulnerable due to their lack of adaptation to invaders (Moyle and Light 1996;Ros et al. 2019). ...
The rapid expansion of three-spined stickleback (Gasterosteus aculeatus Linnaeus, 1758 (Perciformes, Gasterosteida)) in the pelagic zone of Lake Constance, Central Europe, since 2012 contributed to stark ecosystem-wide effects, such as food-web shifts and declines in native biodiversity, including commercially important fish species. Yet, the origin of this invasive pelagic population remains unclear. Using RAD-sequencing of Lake Constance sticklebacks, we show that the pelagic Lake Constance population likely arose recently within the lake, potentially from the littoral population. We did not detect any substantial genome-wide genetic differentiation between individuals from different habitats, supporting a recent origin of the pelagic population and/or ongoing gene flow. This is further supported by minimal differences in meristic and morphometric traits. However, we also identified multiple outlier loci between littoral and pelagic individuals across the genome, potentially suggesting early signs of adaptation despite high connectivity. In this study, we provide an important example of rapid within-lake ecological diversification of an invasive species from standing genetic variation. Ultimately, our findings will have major implications for the management of invasive pelagic stickleback, as they indicate that the stickleback population has to be managed as a whole and that management efforts cannot only focus on the hyper-abundant pelagic population.
... Invasive alien species have the capability to make themselves, invade, adapt and compete natives and also make dominance at the new environment in few weeks only. 11 Invasive weeds are presently influencing each and every ecosystem types in the world and they are the second most noteworthy global threat to the biodiversity after habitat destruction. 9,12 IAS competes the native species for resources such as -breeding sites and food indirectly by changing habitat and adjusts nutrient cycling, hydrology and other ecosystem processes. ...
Lantana camara is more famous as poisonous weed instead of medicinal plant in the majority of the nations. The camara plant can propagate even in the outrageous extreme climate of tropical as well as subtropical areas and thus get naturalized overall as a decorative plant counting India. Steroid, flavonoids, saponins, alkaloids, triterpenoids and tannins are some phytochemicals that are identified from the L. camara L. Besides, this plant is also its contribution in the form of oil-generating plants, and the accessible fundamental oil available in the market is known by the name of Lantana oil. However it also shows its properties in treating variety of diseases viz. bronchitis, stomach pain, gastrointestinal diseases, etc. The natural resources are misused and have drawn nearer to the edges of earth's capability. Mill made paper's life cycle really damages the atmosphere from beginning and lasts for the end. Thus this study highlights that how an alternative eco-safe material and method can help in the production of handmade paper. The key purpose is to emphasize the potential of invasive plants and weeds those makes the negative effect on the other side by crops. Thus, these weeds are used as non-wood raw material for paper production.
... The studied population of F. paralugubris can be considered locally invasive due to its recognized effects on several autochthonous taxa Di Nuzzo et al. in press). In addition to direct impacts on other organisms, invasive species can also affect ecosystem functioning (Crooks, 2002), especially when they are also ecosystem engineers (Frelich et al., 2006;Jochum et al., 2021). ...
Red wood ants (RWA) are ecologically important keystone species that affect a multitude of taxa at different trophic levels. In the past century, some RWA species were used as biological control agents and exported outside their native range. One of these species is Formica paralugubris, which was transplanted from the Italian Alps to the Apennines (Central Italy) but also to Quebec (Canada). Recently, it has been demonstrated that some of the introduced populations have acquired some
invasivity features.
This PhD thesis investigated the ecology of Formica paralugubris, aiming to assess its impact at multiple levels, from single taxa to the forest ecosystem as a whole. To do this, I combined different techniques, from direct observations to gas analysis and stable isotopes analysis. I started with assessing the effect of the presence of this species on epiphytic lichen communities, and I analyzed the myrmecophilous fauna inhabiting the nest mounds of introduced and autochthonous populations. I then compared the trophic position of native and introduced populations of this species, using Stable Isotopes Analysis (SIA) techniques. Finally, I characterized the microbial
communities hosted within the nest mounds using molecular techniques and I measured the gas emissions from the mounds. To conclude, I have done an overview of the protection status of RWA throughout Europe.
Overall, the results of this thesis confirm the ecological importance of F. paralugubris. This species was shown to affect the composition of lichen communities, both from a taxonomic and a functional point of view. Its nest mounds host a rich myrmecophilous fauna and diverse microbial communities. The species was also found to occupy key positions in the trophic web and to play an important role in the carbon dynamics at the forest scale. These results were also discussed in light of the nature of F. paralugubris as a peculiar invasive species. Finally, the complex status of RWA protection was highlighted, also pointing out paradoxical situations in which the introduced populations are protected whereas the native and sometimes declining ones are not.
... The negative effects of invasive species have touched nearly every corner of the globe. Newly introduced species may alter every trophic level of the native community by initiating a trophic cascade both through direct (e.g., predation, competition) and indirect (e.g., habitat alteration) means (Moyle and Light 1996;Crooks 2002;Strayer 2010;Gallardo et al. 2016). Following a review of the species protected under the U.S. Endangered Species Act, Dueñas et al. (2018) found 73% of those with available information had been negatively impacted by invasive species. ...
Invasive species cause severe environmental and economic damage throughout the globe. Aside from preventing their introduction, early detection of newly introduced species is the most successful method to prevent their establishment, spread, and eventual negative impacts. Broad-spectrum monitoring for the early detection of novel non-native species is oftentimes heavily burdened by the inherent difficulty in maximizing the detection probabilities of numerous high priority species simultaneously with only finite resources. We attempted to increase the efficiency of broad-spectrum monitoring in four locations across Lake Erie (USA)—the Detroit River, Maumee Bay, Sandusky Bay, and Cleveland—by targeting our site and gear selections to maximize overall species richness and detection rates of rare and non-native species, with the results compared to a random sampling design. Overall species richness was significantly higher in all four locations, while non-native species detection rates were significantly higher in every location except for Cleveland. Detection rates of rare species was significantly higher in Maumee Bay only. Our results indicate this selective sampling design is more likely to detect a newly introduced non-native species than a random sampling design and are in support of the established literature for broad-spectrum monitoring for novel aquatic invasive species.
... insectivores and their predators [12]. By potentially reducing native biodiversity, nonnative plants can also diminish the ecosystem functions that native species perform, such as pollination and tree regeneration, which may consequently alter the succession dynamics of a landscape [13][14][15][16]. ...
Temperate insectivorous bats value high prey abundance and appropriate vegetative structure when selecting foraging habitats. Forests, particularly in the eastern United States, provide prime foraging habitats for bats but can be heavily impacted by non-native plants, which may alter arthropod diversity and abundance, as well as vegetative structure. To investigate the associations between non-native plants and insect abundance, vegetative structure, and, consequently, bat activity, we performed vegetation surveys, insect trapping, and acoustic monitoring at 23 forested plots in northern New Jersey, USA. We predicted that non-native vegetation would either positively influence bat activity by increasing structural openness (thus, facilitating flight) or negatively influence bat activity by lowering the abundance of putative prey. We also hypothesized that vegetative characteristics, and therefore non-native vegetation, impact bats differently depending on their foraging habitat preferences. The percent of non-native cover of the ground and midstory vegetative layers of our study plots ranged from 0 to 92.92% (x¯ = 46.94 ± 5.77 SE) and was significantly correlated with structural vegetative characteristics, such as midstory clutter (β = 0.01 ± 0.006 SE), but not putative prey abundance (β = −0.81 ± 2.57 SE). Generalized linear models with only vegetative characteristics best predicted overall bat activity and foraging, which were greatest in areas with a high percent non-native vegetation and low midstory clutter. Although percent non-native vegetation and midstory clutter were also significant effects for bats that prefer to forage in open areas, neither vegetative characteristics nor prey abundance were significant effects for clutter-loving bats. Such findings suggest that vegetative structure is more important than prey availability for predicting overall insectivorous bat activity, but other factors, such as foraging strategy and life history traits, can impact how bat guilds respond to non-native vegetation. Therefore, more research is required to reveal additional mechanisms by which non-native plants impact bats.
... Biological invasions induce fundamental changes in native environments by decreasing their functions and diversity at the species, genetic and ecosystem levels (Crooks 2002). Invasions happen more frequently in disturbed, fragmented and destroyed habitats, which may exacerbate habitat deterioration (Marvier et al. 2004). ...
Invasions of alien plants often result in biodiversity loss and may impact the biology of native species. However, the effects of biological invasions on the behavioural responses of native species have rarely been investigated. We studied how the alteration of habitat due to the invasion of alien goldenrod (Solidago spp) affects a native butterfly, the scarce large blue Phengaris teleius, which is a flagship species for grassland biodiversity conservation. To better understand immediate responses in flight behaviour (daily movements, resting, and dispersal) to a new habitat, we performed observations of experimentally translocated butterflies of two origins (invaded vs. non-invaded habitats) to four different environments: invaded habitat, non-invaded habitat, invaded matrix, non-invaded matrix. Moreover, we tested whether the level of invasion may be related to the variation in morphological traits associated with flight (wing size, body mass) and genetic variability. Flight behaviour was affected by the high goldenrod cover and the sex of the butterflies, regardless of the butterflies’ origin. In the habitat and matrix invaded by goldenrod, the butterflies tended to display dispersal behaviour more often compared to the non-invaded ones. Flight distances were longest in the matrix with goldenrod and resting time was longest in habitats invaded by goldenrod. Analysis of morphological traits as well as eight microsatellite loci did not reveal significant differences in morphology or genetic variation among the populations studied.
... Species invasions are ever increasing (Seebens et al., 2021) and, as one of the leading drivers of global environmental change, they can be a pressing and costly concern (Diagne et al., 2021;Pyšek et al., 2020). Invasive species may also be ecosystem engineers, modifying ecosystem structure and functioning by altering biogeochemical cycling (Barot et al., 2007;Vitousek et al., 1987), disturbance regimes (e.g., Mack & D'Antonio, 1998), species interactions (e.g., Gribben et al., 2009), and/or physical characteristics of the environment (Crooks, 2002;Gutiérrez et al., 2011). Research has typically focused on the negative effects of biological invasions, but invaders may also increase ecosystem services, posing management trade-offs. ...
Invasive plants formed via hybridization, especially those that modify the structure and function of their ecosystems, are of particular concern given the potential for hybrid vigor. In the U.S. Pacific Northwest, two invasive, dune‐building beachgrasses, Ammophila arenaria (European beachgrass) and A. breviligulata (American beachgrass), have hybridized and formed a new beachgrass taxa ( Ammophila arenaria × A. breviligulata ), but little is known about its distribution, spread, and ecological consequences. Here, we report on surveys of the hybrid beachgrass conducted across a 250‐km range from Moclips, Washington to Pacific City, Oregon, in 2021 and 2022. We detected nearly 300 hybrid individuals, or an average of 8–14 hybrid individuals per km of surveyed foredune. The hybrid was more common at sites within southern Washington and northern Oregon where A. breviligulata is abundant (75%–90% cover) and A. arenaria is sparse and patchy. The hybrid displayed morphological traits such as shoot density and height that typically exceeded its parent species suggesting hybrid vigor. We measured an average growth rate of 30% over one year, with individuals growing faster at the leading edge of the foredune, nearest to the beach. We also found a positive relationship between hybrid abundance and A. arenaria abundance, suggesting that A. arenaria density may be a controlling factor for hybridization rate. The hybrid showed similar sand deposition and associated plant species richness patterns compared with its parent species, although longer term studies are needed. Finally, we found hybrid individuals within and near conservation habitat of two Endangered Species Act‐listed, threatened bird species, the western snowy plover ( Charadrius alexandrinus nivosus ) and the streaked horned lark ( Eremophila alpestris strigata ), a concern for conservation management. Documenting this emerging hybrid beachgrass provides insights into how hybridization affects the spread of novel species and the consequences for communities in which they invade.
... All analyses were conducted using Morpheus. 5 capable of creating thick beds that limit water movement and light penetration, and ultimately reduce habitat complexity within the systems they invade (Crooks 2002). Starry stonewort has a similar growth habitat and exhibits characteristics that would allow it to become an ecosystem engineer like hydrilla and Eurasian watermilfoil, most notably the ability to develop a dense surface canopy that restricts light penetration, water movement, and gas exchange; and the production of bulbils. ...
Starry stonewort [Nitellopsis obtusa (Desvaux) J. Groves] is a green macroalga in the family Characeae that is native to Eurasia. In the United States it has invaded many waterbodies across the northern tier from New York to Minnesota. In Minnesota, starry stonewort often grows later into the growing (September to December) season than most native species; however, the environmental factors that influence this life history trait are not well understood. Starry stonewort was harvested every 3 wk from May to November in 2020 and 2021 from four locations in Lake Koronis, Stearns County, MN. Light, water pH, and water temperature were also collected to correlate these variables to starry stonewort growth. Rhizoid biomass had weak negative correlations with temperature (rs ¼ 0.19) and pH (rs ¼ 0.14). Bulbil biomass had weak negative correlations with temperature (rs ¼ 0.24), pH (rs ¼ 0.31), and light transmittance (rs ¼ 0.11). Bulbil density had weak negative correlations with temperature (rs ¼ 0.23), pH (rs ¼ 0.29), and light transmittance (rs ¼ 0.10). Bulbil production was highest between October and November of each year. Bulbil biomass and density was lower in 2020 (4.6 g m2 and 1,229 bulbils m2) thanin2021(14.7gm2 and 5,211 bulbils m2). The average annual bulbil density was 1,537 bulbils m2 and ranged from 0 to 157,000 bulbils m2. The ability of starry stonewort to grow in dense mats and produce large quantities of bulbils contributes to the difficulty of controlling infestations. Bulbils are a method of spatial and temporal distribution that can allow for recolonization of previously treated areas.
... However, restoring habitat-building species requires understanding the interaction network within which the species is embedded; this includes both positive and negative interactions that link community members (Halpern et al. 2007, Gagnon et al. 2020. Non-native species may alter these interaction networks, change physical structure, or alter disturbance regimes (Crooks 2002, Hensel et al. 2021 in different ways than resident species, complicating habitat restoration efforts. As such, pressure by invasive species on their invaded systems may influence the path, pace, and outcome of restoration efforts. ...
... When the positive feedbacks of an organism on its own growth are strong enough, the ecosystem engineer can locally create its own optimal environment and exist in suboptimal ambient environmental conditions where it would not survive otherwise (Jones et al., 1994;Crooks, 2002;Hastings et al., 2007). Recently, reef-forming cold-water corals were identified as a self-organized system, meaning that the corals enhance their resource intake by optimizing their spatial configuration on the seafloor (van der . ...
Framework-forming cold-water corals (CWCs) are ecosystem engineers that build mounds in the deep sea that can be up to several hundred metres high. The effect of the presence of cold-water coral mounds on their surroundings is typically difficult to separate from environmental factors that are not affected by the mounds. We investigated the environmental control on and the importance of ecosystem engineering for cold-water coral reefs using annotated video transect data, spatial variables (MEMs), and hydrodynamic model outputs in a redundancy analysis and with variance partitioning. Using available hydrodynamic simulations with cold-water coral mounds and simulations where the mounds were artificially removed, we investigated the effect of coral mound ecosystem engineering on the spatial configuration of reef habitat and discriminated which environmental factors are and which are not affected by the mounds. We find that downward velocities in winter, related to non-engineered environmental factors, e.g. deep winter mixing and dense-water cascading, cause substantial differences in reef cover at the broadest spatial scale (20–30 km). Such hydrodynamic processes that stimulate the food supply towards the corals in winter seem more important for the reefs than cold-water coral mound engineering or similar hydrodynamic processes in summer. While the ecosystem-engineering effect of cold-water corals is frequently discussed, our results also highlight the importance of non-engineered environmental processes. We further find that, due to the interaction between the coral mound and the water flow, different hydrodynamic zones are found on coral mounds that likely determine the typical benthic zonations of coral rubble at the mound foot, the dead coral framework on the mound flanks, and the living corals near the summit. Moreover, we suggest that a so-called Massenerhebung effect (well known for terrestrial mountains) exists, meaning that benthic zonation depends on the location of the mound rather than on the height above the seafloor or water depth. Our finding that ecosystem engineering determines the configuration of benthic habitats on cold-water coral mounds implies that cold-water corals cannot grow at deeper depths on the mounds to avoid the adverse effects of climate change.
... 13 However, they could be more significant when invasive species are ecosystem engineers. 26,27 Invasive earthworms, for example, can be particularly impactful to native biodiversity and ecosystems that previously lacked native earthworms, such as in most northern North American forests [28][29][30][31] and Arctic regions. 32 Recent studies showed that invasive earthworms affect soil microorganisms, soil ...
Among the most important impacts of biological invasions on biodiversity is biotic homogenization, which may further compromise key ecosystem processes. However, the extent to which they homogenize functional diversity and shift dominant ecological strategies of invaded communities remains uncertain. Here, we investigated changes in plant communities in a northern North American forest in response to invasive earthworms, by examining the taxonomic and functional diversity of the plant community and soil ecosystem functions. We found that although plant taxonomic diversity did not change in response to invasive earthworms, they modified the dominance structure of plant functional groups. Invasive earthworms promoted the dominance of fast-growing plants at the expense of slow-growing ones. Moreover, earthworms decreased plant functional diversity, which coincided with changes in abiotic and biotic soil properties. Our study reveals that invasive earthworms erode multiple biodiversity facets of invaded forests, with potential cascading effects on ecosystem functioning.
... For some authors, the use of native plants is also assumed as a strategy to reduce susceptibility to invasion by exotic species[62, [91][92][93], but even in areas where the composition is projected only for natives, and despite the higher maintenance rates, the establishment of invasive plants might occur, especially with herbaceous plants (Bidens pilosa, Digitaria sanguinalis, Soliva sessilis, etc.). Studies that correlate invasive species with ES and ED in the urban environment are beginning to emerge [77], showing that although these species generally have numerous consequences in the ecosystems [94][95][96], due to their good adaptability, they can serve, in an initial phase, as a vehicle for the recovery of degraded lands [97]. ...
The adverse effects of urbanized areas’ growth might be mitigated by the multiple ecosystem services that urban green infrastructure provides. However, the design and composition of such infrastructure is still a hotly debated issue, mainly considering the challenges associated with the use of exotic plant species. To assess if there is a clear association between the species’ origin and ecosystem services or ecosystem disservices, an in-depth systematic literature review was carried out based on a bibliometric approach to assess the panorama of the scientific perspective. Based on the results, a detailed analysis was performed for the urban green infrastructure of five European Mediterranean cities, where management and expansion of the urban green infrastructure might act as tools to mitigate climate change and biodiversity loss. Urban green infrastructure benefits to urban areas and its composition must consider the balance between services and disservices provided by plant species. Data analysis shows that disservices are not exclusively related to exotic species, revealing that plant species selection based on their origin represents a biased approach, as it often disregards the higher capacity of some exotic species to thrive under continuous pressure and disturbance, along with relevant and highly valued cultural services provided. Since exotic species are commonly used, ecosystems formed can be seen as experiments to support decisions, allowing new approaches to planning, designing, and maintaining urban green infrastructure.
... The impacts of introduced parasite species on native hosts and their habitats can be profound (species extinction) or more subtle (decreased vigor or evolutionary pressure). Effects of species introductions are documented in countless examples and circumstances, from predation and direct competition for resources (Bury and Luckenbach 1976;Cadi and Joly 2004) to alteration of habitat conditions (Crooks 2002), fire regimes (Pellant 1996;Brooks et al. 2004), trophic cascades (Ellis et al. 2011), decreased fitness (Koop et al. 2011), and transmission of parasites to native species (Peeler et al. 2011;Héritier et al. 2017). ...
There is conservation concern for the Northwestern Pond Turtle (Actinemys marmorata) throughout its range and non-native parasitic leeches using A. marmorata as a host could impose an additional threat. Freshwater turtles native to eastern and central North America are common hosts of parasitic leeches and associated blood pathogens, although the health impacts on turtles are not well-studied. The Common North American Turtle Leech (Placobdella parasitica) is widespread east of the Rocky Mountains where it parasitizes a wide range of turtle species. Occurrences of P. parasitica west of the Rocky Mountains are presumed to be from translocations of their turtle hosts from east of this mountain range. Herein, we report P. parasitica using A. marmorata as a host in the Lower Rogue River, southwestern Oregon, USA. Leeches appear to be well-established in this stretch of river. Leech prevalence on turtles was significantly higher for adults than for juveniles but was not significantly different between adult male and female turtles. We did not detect a significant difference in body condition between adult turtles with or without leeches, although body condition was slightly lower in turtles with leeches. The health impacts of leech introductions on the only native turtle in southwestern Oregon warrants further investigation to determine if P. parasitica represents an emerging threat by reducing fitness or serving as a vector to spread pathogens within populations of A. marmorata.
... The ecological impact of invasive species on native communities is not well documented in Serbia but there is evidence of widespread distribution in Serbian waters, dense populations and coexistence with native fauna [63]. They can cause direct biotic interactions with the native community (e.g., predation and competition) and also indirect changes in habitat conditions (e.g., habitat structure and turbidity) [65,66].Evidence of the negative impact of invasive species on native unionids has already been observed in many European countries as well as in North America [19]. ...
The thick-shelled river mussel, Unio crassus Philipson, 1788, is considered to be one of the species with the highest conservation priority in Serbia. The study represents the first comprehensive research of the distribution of U. crassus in Serbian waters. The research covered a variety of waterbody types throughout Serbia, and distribution data were considered over three time periods from 1953 to 2019. The paper summarizes all the available literature data, field research and information obtained during the review of the collection of malacological material of the Natural History Museum in Belgrade. The results show a positive population trend, which is reflected in an extension of the distribution area and an increase in population density. After reviewing the museum collection, 13 synonyms for U. crassus were identified. The study also revealed a better insight into the habitat requirements and the limiting factors of the species. Substrate characteristics, waterbody types, altitude, and nitrate content of the water seem to be of great importance for the occurrence of the species. The results presented here can improve further measures for the conservation of U. crassus, not only in Serbia, but also in the Western Balkans.
... Worldwide, over 750 species of trees and shrubs are considered to be invasive (Rejmánek and Richardson, 2013). Due to their biomass dominance and ability to modify ecosystem characteristics (Corenblit et al., 2014;Crooks, 2002;García et al., 2023), most of them significantly affect biodiversity and ecosystem services (Castro-Díez et al., 2019;Potgieter et al., 2017;Wohlgemuth et al., 2022), as well as contribute to economic losses (Bacher et al., 2018). The impacts of invasive species are nonlinearly scaled with their quantity in the ecosystem (Kumschick et al., 2015;Pearse et al., 2019;Sapsford et al., 2020). ...
Biological invasions are one of the most important threats to biodiversity. However, spread mechanisms have been described in detail only for some widespread taxa. Here, we aim to characterize the unique phenomenon of ×Sorbaronia Mitschurinii (Rosaceae) spread into temperate Scots pine forests. We assessed the surroundings of an abandoned ×Sorbaronia Mitschurinii plantation, established in 1986 near Ośno Lubuskie (W Poland). Around the plantation we established 66 study plots in 30 m intervals along eight transects, in a systematic design. Using generalized linear mixed-effects models we analysed how the distance from the propagule source (i.e. abandoned plantation), maximum age of ×Sorbaronia shrubs assessed using dendrochronological techniques, and light availability determined the density and biomass of the studied plant. We found that its mean aboveground biomass in the plantation was 7.22 ± 0.66 Mg ha −1 , and decreased with distance from the propagule source: 6.83 Mg ha −1 30 m from the abandoned plantation, 1.38 Mg ha −1 at a distance of 90 m, and 0.11 Mg ha −1 at a distance of 180 m, almost disappearing at further distances (but present at the maximum distance of 450 m). The density and aboveground biomass of ×Sorbaronia Mitschurinii increased with increasing maximal age of the studied plant and its light availability. The ×Sorbaronia Mitschurinii plantation acted as a strong propagule source, as it reached a density of 100 ind. 100 m −2 after five years, forming a dense shrub layer, capable of reproducing. We conclude that alien species planted at high density and left with no management control might transform into invasion hotspots under favourable circumstances. The study highlights the importance of scientific awareness of similar cases of overlooked invasion sources, as management to limit their spread is still possible.
... Because non-native fish constitute new structural and functional components in local communities, leading to changes in trophic level (Strayer et al., 2005;Strayer, 2010). The direct interaction between non-native and native communities (e.g., competition and predation) and indirect changes in habitat (e.g., water quality and habitat structure) could further reduce the richness and abundance of native fish, even regional extinction and simplification of the food web structure (Crooks, 2002;Strecker and Arnott, 2008). In addition, individual taxonomic diversity is not enough to reveal the variation of communities, multifaceted metrics of diversity provide a complete perspective on different processes acting on communities (Jarzyna and Jetz, 2016;Li et al., 2020). ...
Subtropical rivers are one of the hotspots of global biodiversity, facing increased risks of fish diversity changes and species extinction. However, until now, human impacts on native and non-native fish communities in subtropical rivers still lack sufficient effort. Here, we used the environmental DNA (eDNA) approach to investigate fish communities in the Dongjiang River of southeast China, a typical subtropical river, and explored the effects of regional land use and local water pollution on fish taxonomic and functional diversity. Our data showed that 90 species or genera of native fish and 15 species or genera of non-native fish were detected by the eDNA approach, and there was over 85% overlap between eDNA datasets and historical records. The taxonomic and functional diversity of all, native and non-native fish communities showed consistent spatial patterns, that is, the upstream of the tributary was significantly higher than that of the mainstream and downstream. Land use and water pollution such as COD and TP were the determinants in shaping the spatial structure of fish communities, and water pollution explained 31.56%, 29.88%, and 27.80% of the structural variation in all, native and non-native fish communities, respectively. The Shannon diversity and functional richness of native fish showed a significant downward trend driven by COD (p Shannon = 0.0374; p functional = 0.0215) and land use (p Shannon = 0.0159; p functional = 0.0441), but they did not have significant impacts on non-native fish communities. Overall, this study emphasizes the inconsistent response of native and non-native fish communities to human impacts in subtropical rivers, and managers need to develop strategies tailored to specific fish species to effectively protect water security and rivers.
... However, wild boars can also negatively impact forest regeneration and understory biodiversity. They upturn extensive forest areas (Hegel and Marini, 2013;Orlowska and Nasiadka, 2022;van Doormaal et al., 2015;Wirthner et al., 2012), directly or indirectly affecting other organisms by altering habitat characteristics and resource availability (Baubet et al., 2003;Crooks, 2002;Maaroufi et al., 2022;Nagy et al., 2015). While the effects of wild boar grubbing on surface vegetation composition and function have been welldocumented (Brunet et al., 2016;Dovrat et al., 2014;Orlowska and Nasiadka, 2022), less is known about their impact on soil biomes (Brunet et al., 2016;Carpio et al., 2022). ...
Soil disturbances caused by large animals impact soil biodiversity and potentially alter forest ecosystem functioning and productivity. However, most studies have focused on the effects of wild boar infestations on above-ground vegetation and soil physical and chemical properties. Little is known about the influence of wild boar grubbing on the soil faunal community within forested ecosystems. To address this knowledge gap, we conducted a long-term (10-year) exclosure experiment to investigate the responses of soil nematode communities to wild boar grubbing and seasonal variations in a broad-leaved Korean pine forest in Changbai Mountain, China. The results indicated that wild boar grubbing did not significantly impact soil nematode abundance, genus richness, diversity indices (Shannon-Wiener diversity index, Simpson index, and evenness index), and ecological indices (en-richment index, channel index, structural index, and basal index). However, we observed that grubbing reduced the relative abundance of plant parasites while increased that of bacterivores and the maturity index (MI), leading to changes in nematode community composition. Notably, the influence of grubbing was more pronounced in the spring than in the autumn. Although season itself did not significantly affect soil nematode genus richness and diversity indices, it did affect soil nematode relative abundance, bacterivores, omnivores-predators, plant parasites, K-strategistis, r-strategistis, MI, enrichment index, and channel index. Long-term wild boar grubbing appeared to mitigate seasonal effects on soil nematode communities, resulting in higher MI and increased stability in nematode community abundance. Our findings suggest that changes in soil parameters, such as soil NH 4 + , soil pH, and soil NO 3-, likely mediate the observed impact of wild boars on the soil nematode community. In summary , our study demonstrated that wild boar grubbing altered the structure of soil nematode communities, albeit with seasonal variations, indicating that the effects of wild boar activity on forest soil ecosystems influence bio-geochemical cycles through changes in nematode community composition rather than nematode genera richness .
... S. alterniflora has been found in almost all regions of the mudflat shoreline of the Chinese mainland, with expanding invasion areas . In the invaded area, hydrology, sedimentary dynamics, primary productivity, biogeochemical cycling, and biodiversity have been significantly altered compared to the original habitat (Crooks, 2002;Neira et al., 2007;Ding et al., 2023;Li et al., 2023b). In particular, S. alterniflora not only invaded bare mudflat, but also replaced the native plant seepweed (Suaede salsa), which was the dominant species on the coastal mudflat of the Southern Yellow Sea Zhang et al., 2018;Li et al., 2023a). ...
On a Chinese coast of the Yellow Sea, a 15-year Spartina alterniflora invasion sequence was classified into five stages: no invasion, initial invasion, immature invasion, mature invasion, and senescing invasion. The effects of invasion on Bullacta caurina distribution were studied. The stem density and vegetation coverage, and sediment organic matter content increased after S. alterniflora invaded, whereas chlorophyll a concentration and porewater salinity decreased. The stem density and vegetation coverage, and porewater salinity were the dominant factors explaining habitat variations. The invasion stages, seasons and their interaction had significant effects on B. caurina density, and the density decreased after initial invasion stage of S. alterniflora. Here, a clumped spatial distribution pattern was detected on B. caurina population. Organic matter content and chlorophyll a concentration were distinguished for predicting B. caurina density. The hydrologic condition, food resources, temperature, and predation risk comprehensively affected B. caurina distribution after S. alterniflora invasion.
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... Ecosystem engineers have profound effects on ecosystem structure and functioning in terrestrial and aquatic ecosystems globally (Jones et al., 1994;Crooks, 2002;Emery-Butcher et al., 2020). When an invasive species is classed as both a habitatforming and habitat-modifying ecosystem engineer, not only does it compete with native species (Mooney and Cleland, 2001;Morriën et al., 2010), but it may also create novel habitat (Rodriguez 2006;Byers et al., 2012;Firth et al., 2021), and modify abiotic conditions such as light, temperature or sediment deposition (Levin et al., 2006;McKinney and Goodell, 2010) that can have cascading environmental, economic and social impacts (Thomsen, 2010;Gribben et al., 2019;Wood et al., 2022; for a review see Guy-Haim et al., 2018). ...
Background and aims
Worldwide, invasive species are spreading through marine systems at an unprecedented rate with both positive and negative consequences for ecosystems and biological functioning of organisms. Human activities from shipping to habitat damage and modification are known vectors of spread, although biological interactions including epibiosis are increasingly recognised as potentially important to introduction into susceptible habitats.
Methods
We assessed a novel spread mechanism - limpets as transporters of invasive algae, Sargassum muticum into beds of the seagrass Zostera marina - and the physiological impact of its invasion. The association of S. muticum with three limpet species and other habitats was assessed using intertidal surveys on rocky shores and snorkelling at two seagrass sites in the UK. A 4-yr field study tested the effect of S. muticum on Z. marina shoot density, dry weight and phenolic compounds (caffeic and tannic acid) content, and a laboratory experiment tested the impact of S. muticum on nutrient partitioning (C/H/N/P/Si), photosynthetic efficiency (Fv/Fm) and growth of Z. marina.
Results
On rocky shores 15% of S. muticum occurrences were attached to the shells of live limpets. In seagrass beds 5% of S. muticum occurrences were attached to the shells of dead limpets. The remainder were attached to rock, cobblestones, the seagrass matrix or embedded within the sand. Z. marina density and phenolics content was lower when S. muticum co-occurred with it. Over 3-years, photosynthetic response of Z. marina to S. muticum was idiosyncratic, and S. muticum had no effect on nutrient partitioning in Z. marina.
Conclusions
Our results show limpets support S. muticum as an epibiont and may act as a previous unreported transport mechanism introducing invaders into sensitive habitats. S. muticum reduced phenolics production in Z. marina which may weaken its defensive capabilities and facilitate proliferation of S. muticum. The effect of S. muticum on Z. marina photosynthesis requires further work but having no effect on the capacity of Z. marina to sequester nutrients suggests a degree of resilience to this invader.
... Invasive alien species (IAS) are one of the five direct drivers of global change in the Anthropocene, with an estimated 20% of Earth's surface at risk from invasions (Balvanera et al. 2019). Globally, IAS are a key threat to many endangered species and habitats (Crooks 2002;Maxwell et al. 2016), while also presenting threats to human health, wellbeing and economies (Pyšek and Richardson 2010;Rai and Singh 2020). Despite increases in policyorientated research in invasion science (Pinto et al. 2022) and in the development and implementation of legislation and agreements to manage and prevent this threat, there appears to be no saturation in the accumulation of alien species introductions worldwide (Seebens et al. 2017). ...
Invasive alien species (IAS) pose a key threat to biodiversity, the economy and human well-being, and continue to increase in abundance and impact worldwide. Legislation and policy currently dominate the global agenda for IAS, although translation to localised success may be limited. This calls for a wider range of responses to transform IAS management. An under-appreciated strategy to achieve success may come from bottom-up, experimental innovations (so-called “seeds”), which offer alternative visions of what may be possible for IAS management in the future. We present an application of a participatory process that builds on such innovations to create alternative visions of the future, with actionable pathways to guide change. Through a series of workshops with practitioners and academics, we used this process to explore alternative positive futures for IAS management in South Africa. We then identified a set of domains of change, that could enable these visions to be actioned by appropriate stakeholders. The domains of change highlight the social–ecological nature of the IAS sector, with interconnected actions needed in financial, cultural, social, technological and governance spheres. Key domains identified were the need to shift mindsets and values of society regarding IAS, as well as the need for appropriate and functional financing. This participatory futuring process offers a way to interrogate and scale bottom-up innovations, thereby creating optimism and allowing stakeholders to engage constructively with the future. This represents an important step in fostering the potential of bottom-up innovations to transform IAS management.
... As wide-ranging ecosystem engineers, marine bivalves increase habitat complexity and influence the biodiversity of benthic communities through the formation of biogenic reef structures (Commito et al. 2005;Borthagaray and Carranza 2007;Sousa et al. 2009). Many bivalves, such as mussels, are filter-feeders that play critical roles in the cycling of nutrients and improving water quality in coastal systems (Crooks 2002). One such mussel, Perna viridis (Linnaeus 1758), is abundant and widely distributed throughout the Indo-Pacific region (Siddall 1980). ...
The ability of marine organisms to persist under, and recover from, periods of stressful conditions will shape their occurrence in future oceans characterized by exacerbated marine heatwaves (MHWs). Organism persistence and recovery may, in turn, be shaped by traits of the organisms themselves including, for example, body size. In the present study, we tested the responses (survival, heart rate, Arrhenius breakpoint temperature – ABT, clearance rate, respiration rate, and condition index) of large (5 cm) and small (3 cm) Perna viridis mussels after exposure to a three-week marine heatwave (MHW; + 4 °C) and a one-week recovery period. Exposure to elevated temperatures did not affect the survival of large or small mussels, however, at the end of the MHW both size classes exhibited increased heart rate under elevated temperatures, small mussels exhibited increased ABT, and large mussels exhibited significantly increased clearance rate. Following one week of recovery at control temperature, the altered responses had returned to be similar to those of mussels held under control conditions. The results obtained here indicate that both sizes of mussels can readily recover from exposure to short-term elevated temperatures imposed by MHWs, enabling the continued persistence of P. viridis mussels in future oceans.
... On the other hand, few invasive plant species significantly contribute to ecosystem services than the native species through rapid carbon sequestration and biomass accumulation (Ni et al. 2019;Parepa et al. 2013). These plants also cater to services for effective nitrogen fixation while adopted during reforestation of degraded lands, improved fallows, and contour hedgerows (Crooks 2002;Richardson et al. 2004). Many such alien and invasive plant species are also reported for their medicinal uses (Bhagwat 2022;Tripathi et al. 2020) and as nutritious conventional food. ...
With the rapid increase in urbanization including construction for road and rail connectivity and accelerated disturbances in the natural habitats, the introduction, establishment, and invasion of alien and native invasive plants are favored in the Indo-Burma biodiversity region. Detail information on alien and invasive plants in the Indo-Burma Biodiversity region are very meager. Therefore, detail studies on such plants are very important so that the plant invasion process does not get out of hand. Present study deals with assessment of the distribution of alien and invasive and other native plants which were considered as weeds. In the study, different localities distributed in the hills and the valleys at tropical, subtropical, and temperate zones of Manipur state were randomly surveyed and plants of non-woody life forms (herbs, shrubs and climbers) were investigated. A total of 98 alien and invasive plant species were recorded from different localities of the state. Most of them originated from the American continent and contributing ca. 59%. With 28 species, the Asteraceae family was the most dominant among the total 29 families recorded. Dominant species include Ageratina adenophora (Spreng.) King and H. Rob., Ageratum conyzoides L., Ageratum houstonianum Mill., Bidens pilosa L., Chromolaena odorata (L.) R.M. King and H. Rob., Lantana camara L., and Mikania micrantha Kunth. Most of these species were recorded from tropical habitats and their abundance value was comparatively lower in temperate region. Among the recorded species, 37 species were documented for various uses where most of them were used for curing various ailments.
... While our study showed no preferential settlement on non-native or native basibionts, the availability of novel three-dimensional surfaces is expected to support additional species settlement. Improving habitat complexity is likely to increase potential for additional species, thereby increasing species richness (Crooks, 2002). Wonham et al. (2005) describe the facilitation of other species, including invaders, by the presence of the non-native Asian hornsnail (Batrillaria attrimentaria) on a mudflat. ...
... Negative, for example, normally refers to reduced abundance of a native species in the presence of the invader or reduced native diversity or reduced functions or some negative impact on environmental aspects relevant to human well-being; and positive, the opposite. Whether on land or in water, invasive ecosystem engineers (IEE) are indeed considered one of the most influential forms of bioinvasions (see Crooks, 2002 who first discussed the role of IEE; and see a recent study demonstrating the extensive ecological effects of invasive plants specifically within protected areas in China, Ren et al., 2021). Such species have been mobilized by humans across continents for thousands of years, fundamentally transforming ecosystems in their new environments. ...
In both terrestrial and aquatic ecosystems, invasive species are a major driver of global change that is increasing in scope and impact due to the increase in global trade, habitat modification and climate change. Among invasive species, those that are known as ‘ecosystem engineers’ are considered a specific, highly influential, type of invaders, where an invader significantly alters the new environment, either physically or chemically. In this context, this perspective review discusses the different types of possible impacts of invasive ecosystems engineers (IEE) in terrestrial, freshwater, and marine ecosystems.
Scanning the relevant literature on the topic, we find a 12‐year lag in the use of terms relevant to the concept of ecosystem engineers in invasion‐related publications since the first publication of the concept in 1994, with a steep increase in use between 2006 and 2014. A bibliometric mapping showed a high level of connectedness between related terms and clusters, suggesting an ample flow of concepts, ideas and knowledge between realms, ecosystems and regions, and researchers that study them.
Throughout this essay, we illustrate with recent examples the context‐dependency of their (positive and negative) impacts in the three realms. We review the distinction between autogenic (altering the environment for other species with their body) and allogenic (altering the environment for other species with their actions) ecosystem engineering in the context of alien species. We also put a spotlight on the well‐studied engineering effects of IEE plants and macroalgae, terrestrial and aquatic bioturbators and burrowers as well as highly effective consumers.
We finalize with discussing how IEE can strongly affect ecosystem services for human wellbeing and explore the possible contribution of IEE in restoring functions and services in the face of climate change in highly invaded and fast‐warming systems like the southeastern Mediterranean Sea or areas that face frequent fires for example. We claim that the last topic has received little attention from the scientific community and should be given priority in future studies.
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... The AGM occurs most often in intertidal and/or shallow subtidal rocky reef environments, usually in waters of higher and more constant salinity regimes (Segnini et al., 1998;Rajagopal et al., 2006). P. viridis is both an ecosystem engineer (e.g., Crooks, 2002;Borthagaray and Carranza, 2007;Sousa et al., 2009) and an important aquaculture and wild-caught fisheries species (Vakily, 1989;Ong et al., 2009;Prakoon et al., 2010;Awan et al., 2012;Divya et al., 2012;Laxmilatha, 2013;Divya et al., 2020;Rejeki et al., 2020) and is an important source of protein and revenue for peoples in many coastal locations throughout SE Asia (FAO, 2019). In addition, the AGM is now a widely distributed invasive species (CABI, 2021), being found in many warm-water locations, including Brazil, Cuba, eastern Indonesia, Jamaica, Japan, South Africa, Trinidad and Tobago, southeast USA, Venezuela, and several island locations in the South Pacific Ocean (e.g., Siddall, 1980;Hanyu and Sekiguchi, 2000;Baker et al., 2007;Gilg et al., 2013;Castillo et al., 2014;Huhn et al., 2015;Micklem et al., 2016;Dias et al., 2017;de Messano et al., 2019;Arrieche et al., 2020). ...
The Asian green mussel (AGM), Perna viridis, is a mussel of ecological and economic importance throughout much of the tropical and subtropical regions of Asia, from China and Korea in the east to Oman on the Arabian Peninsula in the west. We collated published DNA sequence data and then analysed 467 bp of cytochrome c oxidase I gene (COI) sequence variation from 649 mussels (576 from SE Asia and 73 from India) to test for regional differentiation. Analysis of molecular variation, a haplotype network and a neighbour-joining tree all revealed significant differentiation between mussels from India and those from SE Asia. We observed a greater number of segregating sites (haplotypes) and private haplotypes than expected for Indian mussels compared to SE Asian mussels, based on the respective sample sizes. Tests of neutrality revealed population expansion or a recent selective sweep for only the mussels from India. We suggest that the differentiation of the Indian from the SE Asian mussels is explained by the pronounced seasonal input of freshwater into the northern Bay of Bengal area, which acts as a (semi-permeable) barrier to gene flow between the two regions (i.e., east versus west of the Bay). This suggestion is based on the oceanography of the region and is consistent with the biogeography and reports of genetic breaks in a range of taxa in this region. Further targetted sampling of AGMs from the east coast of India, Bangladesh and Myanmar is required to test this hypothesis, and additional sampling of AGMs from west of India (e.g., Pakistan, Iran, the Arabian Peninsula) will also be informative. Finally, this study is based on the analysis of a single marker (COI) because this is all that is presently available from published sources but we note that the application of new molecular markers such as single nucleotide polymorphisms to newly collected mussel samples will greatly advance our understanding of the AGM genetic discontinuity and its age, and help test its geographical location and its nature (e.g., a steep/shallow cline or a stepped cline).
... When the positive feedbacks of an organism on its own growth are strong enough, the ecosystem engineer can locally create its own optimal environment and exist in suboptimal ambient environmental conditions where it would not survive otherwise (Jones et al., 1994;Crooks, 2002;Hastings et al., 2007). Recently, reef-forming cold-water corals were identified as a 'self-50 organized' system, meaning that the corals enhance their resource intake by optimizing their spatial configuration on the seafloor (van der Kaaden et al., under review). ...
Framework-forming cold-water corals are ecosystem engineers that build mounds in the deep-sea that can be several hundred meters high. The effect of the presence of cold-water coral mounds on their surrounding is typically difficult to separate from environmental factors that are not affected by the mounds. We investigated the environmental control on cold-water coral reefs at multiple spatial scales, using annotated video transects data, spatial variables (MEMs) and hydrodynamic model output in a redundancy analysis and with variance partitioning. Using available hydrodynamic simulations with cold-water coral mounds and simulations where the mounds were artificially removed, we investigated the effect of coral mound ecosystem engineering on the spatial configuration of reef habitat and discriminated which environmental factors are and which are not affected by the mounds. We find that, due to the interaction between the coral mound and the water flow, different hydrodynamic zones are created on a coral mound that likely determine the typical benthic zonation of coral rubble at the mound foot, dead coral framework on the mound flank, and living corals near the summit. Moreover, we observed a so-called massenerhebung effect (well-known for terrestrial mountains) meaning that benthic zonation depends on the location on the mound rather than on the height above the seafloor or water depth. Our finding that ecosystem engineering determines the configuration of benthic habitats on cold-water coral mounds has many implications, such as that cold-water corals cannot simply move towards deeper water depths to avoid the adverse effects of climate change. We further find that downward velocities in winter, related to non-engineered environmental factors, e.g., deep winter mixing and dense water cascading, correlated to substantial differences in reef cover at the broadest spatial scale (20–30 km). Such hydrodynamic processes that stimulate the food supply towards the corals in winter are more important for the reefs than similar hydrodynamic processes in summer. There is much research on the ecosystem engineering effects of cold-water corals, but our results highlight that the influence of non-engineered environmental processes that accelerate the food supply towards the cold-water corals should not be underestimated.
Background
Marine biofouling is a threat to industries working in the marine environment, representing significant costs associated with equipment impairment and loss of performance. In the Marine Renewable Energy (MRE) and other maritime sectors which operate at sea for long periods, an important aspect of biofouling is related to the type and frequency of inspections and biofouling removal procedures.
Methods
This study investigated important parameters of macrofouling (e.g. composition, including the presence of non-indigenous species, thickness, and weight) from communities growing on samples that emulate tubular components of marine renewable devices. The trials were performed during short periods of submersion (one to eight weeks) in the seasons when the colonisation process should be most intensive (spring, summer, and autumn). Furthermore, the frictional resistance forces generated during the scraping of biofouling from those components were investigated.
Results
Overall, results provide insights on the growth rates and removal requirements of biofouling in marine components. The results show that, while biofouling growth in early colonization stages might not present great detrimental effects to wave energy components, the consequent marine corrosion (fostered by biofouling) and the settlement of non-indigenous species (NIS) should be factors of concern.
Conclusions
Performing biofouling-related maintenance activities after the peak of maximum growth and reproduction (during the warmer seasons in temperate to cold environments) is suggested to reduce the number and frequency of activities. NIS can be detected at very early stages in the colonization process, highlighting the importance of biofouling monitoring and the implementation of biosecurity risk assessment plans early in the operational stage of MRE projects.
The biochemical composition of the muscles of two fish species, European smelt Osmerus eperlanus and the Common (Caspian) kilka Clupeonella cultriventris, that were successively invaded and naturalized in the Rybinsk Reservoir in the second half of the 20th century, differs significantly in the fatty acid content. The sum content (mg/g) of eicosapentaenoic (20:5n-3) and docosahexaenoic (22:6n-3) polyunsaturated fatty acids in the muscle tissue of the kilka is almost four times higher than that in European smelt. Given that smelt and the kilka are similar in their ecological and morphological characteristics and do not differ significantly in the composition of their diet in the Rybinsk Reservoir, it is obvious that the observed differences primarily result from the phylogenetic aspect. The obtained data on the composition of the fatty acids of the invaders show that the replacement of one alien species with another (European smelt with the kilka) significantly changed the quality of production of an important link in the trophic web of the reservoir.
The marine otter or chungungo (Lontra felina) is one of the least known carnivore species in Chile, and the available information is scarce and dispersed in time. Few studies have been conducted in Chile before and after the revision of the Natural History of the species in 1998. Therefore, we re-examine the knowledge of the species with current evidence on the marine otter in Chile and the main threats described for its conservation. We observed an irregular pattern in its distribution associated with the size and distance of rocky patches on the coast along with human influence. Also, the southern limit of the distribution remains unclear, with scarce current evidence of the marine otter presence south of Chiloe Island. It has been observed that the marine otter modifies its diet according to the availability of prey, so this would be a limiting environmental variable for its population density and distribution. Threats to the conservation of the species have been identified related to the alteration of its habitat, including incidental mortality from fishing activities, persecution by domestic dogs, and the potential for disease transmission. There is a great need for studies focused on ecology and human dimensions of the marine otter, to carry out adequate conservation of the species.
The barnacle Balanus glandula is a non-native species inhabiting Argentinian rocky shores. The native mussel Brachidontes rodriguezii forms extensive beds in the mid-intertidal zone of these shores, generating a physical structure that determines the diversity of the assemblage. Yet, this native foundation species is prone to mortality due to disturbances associated with extreme climatic events. The aim of this study was to experimentally investigate the role of early-colonizing, non-native B. glandula in the succession process and the recovery of mussel beds following disturbance. Experimental plots were demarcated in the mussel bed and initially cleared of mussels, to produce exposed rock surfaces similar to those that form after a disturbance event. Half of these plots were kept barnacle-free throughout the experiment by removing all recruiting B. glandula , whereas all recruits were allowed to develop in the remaining plots. Our results showed that mussel cover at the end of the experiment was higher in the plots with barnacles. The plots with and without barnacles followed different successional trajectories, with increasing limpet densities and reduced cover of crustose algae in the presence of barnacles during early successional stages. The results indicate that the presence of B. glandula at the early stages of succession can alter successional dynamics and facilitate the recovery of mussel bed cover after disturbance events. More broadly, this study also shows that non-native species, although frequently considered a ‘nuisance’, can accelerate the recovery of foundation species that characterize entire communities and sustain the greatest share of their diversity.
Humans have used surface waters from the beginning on, first for drinking water and for the exploitation of fish and other seafood. Later in human history, freshwater was abstracted for irrigation and for manufacturing purposes. Lakes, rivers, and the oceans became important transport routes first regionally, then globally. Water bodies have been modified physically and new water bodies created by constructing waterways and dams. Construction of infrastructure for shipping and coastal protection further modified surface waters. More recently, tourism became a further use of surface waters. While enjoying all these “ecosystem goods and services” in ever-increasing amounts and intensity, surface waters have also been used as a dump for human wastes of all kind, deteriorating water quality and leading to adverse ecosystem effects. Wastes liberated to the atmosphere, most notably CO2 resulting from combustion processes, finally affect aquatic ecosystems indirectly by climate change or directly end up in surface waters.
Among the many human impacts on aquatic ecosystems, five, globally particularly important impacts have been selected as examples for this book: eutrophication, climate warming, acidification, overfishing, and transport of invasive species. All these examples and further human activities acting on land add up to a domination of the Earth’s surface by humans. This domination is taken as a justification to define our period as a new geological epoch, the Anthropocene.
This research elucidates the ecological status and spatial extent of two non-native invasive species, Lantana
camara L. and Ageratina adenophorum Sprengel, within dominant forest communities across an altitude gradient
in the western Himalayan region. The study, conducted from 2017 to 2019 in the Nainital district of Kumaun
Himalaya, focused on four forest communities; Sal, Chir-pine, Banj-oak, and Mixed-oak, spanning an altitudinal
range from 300 to 2250 meters. Environmental predictors encompassing topographic, physiographic, and climatic
factors, along with species occurrence records, were employed to determine spatial extent. The MaxEnt
statistical model, a machine learning algorithm, facilitated the assessment of the spatial distribution of invasives.
Results indicate that L. camara has invaded Sal, Chir-pine, and Banj oak forests but has not established in highelevation
mixed-oak stands. Conversely, A. adenophora has invaded Chir-pine, Banj-oak, and Mixed-oak stands
but has not been observed in low-altitude Sal forests. No significant variation in species number, diversity, or
distribution pattern along the elevation gradient was observed for either species. Spatial assessment using
MaxEnt revealed an estimated area of 380 km2 for A. adenophora and 285 km2 for L. camara. The study highlights
the mid-altitude zone as the most vulnerable to species invasion. This scientific inquiry contributes valuable
insights for the conservation of non-native shrubs, offering guidance for effective, species-specific conservation
and management strategies in the Himalayan region.
Allelopathy, or chemically mediated interference between co-occurring species, is present in more than half of invasive plant species globally and plays an important role in invasive species dominance in native plant communities. Allelopathy commonly increases the competitive advantage of invasive plants and their ability to displace native species. In extreme cases, invasive plants can cause native species to go extinct and this effect is particularly pronounced in small island ecosystems or isolated and fragmented ecosystems. Extirpation of native species from local communities greatly reduces biodiversity and ecosystem stability and can potentially reduce system productivity and thus C sequestration. Invasive allelopathic plants can also have wide-ranging effects on plant communities and ecosystem processes such as herbivory, decomposition, and nutrient mineralization. Invasive plants are notoriously difficult to control, and management strategies can be expensive, labor-intensive, and often marginally effective. Biochar, or charcoal used as a soil amendment, is primarily known for its potential to enhance productivity and carbon sequestration, but it also has a high capacity to sorb toxic organic compounds, including allelochemicals. Biochar is a form of pyrogenic carbon (PyC) that shares properties with naturally occurring forms of PyC that are widespread in forest soils, particularly in systems with natural fire regimes. Sorption of allelopathic compounds by natural PyC can widely influence overall productivity and species composition in plant communities. Studies to date indicate that biochar can greatly reduce the allelopathic effects of invasive allelopathic plants, including Psidium cattleianum, Acer platanoides, and Alliaria petiolata. Biochar has also been shown to promote native tree growth in invaded plant communities and can also suppress the regeneration of invasive plants. In a seemingly hopeless battle against invasive species, biochar may be a critical tool for successfully combatting invasive allelopathic plants and climate change while simultaneously promoting native biodiversity and carbon sequestration. This chapter reviews the ecological impacts of invasive plants, the facilitation of plant invasions via allelopathy, and the potential of biochar to mitigate the effects of allelopathic invasive plants and climate change.
The anthropogenic deterioration of aquatic ecosystems affects water resources due to agricultural malpractices, pollution from domestic septic tanks, recreational activities, and poor watershed management, among other factors. This study examines the management of Las Curias Reservoir, San Juan, Puerto Rico, after the 2016 arrival of the invasive aquatic fern Salvinia molesta. In September 2019, a community-led initiative introduced the Cyrtobagous salviniae weevil, an effective
biological control agent for S. molesta, and commenced a mechanical removal campaign using an aquatic harvester. Limnological sampling (September 2019 to September 2022) and drone flights were employed to measure physicochemical and floating plant cover changes, respectively, in the reservoir. Monitoring of weevils in the reservoir demonstrated rapid establishment and dispersal, which resulted in visible damage including browning of plants and eventually sinking of entire mats.
From 23 July 2019, the reservoir surface was predominantly covered by salvinia, occupying an area of 17.7 ha (100% coverage). This coverage decreased to 12.6 ha (71%) by 29 January 2021. By 12 August 2022, the coverage had been substantially reduced to just 1.1 ha, representing only 6% of the reservoir surface. In 2022, the reservoir recorded an average dissolved oxygen concentration of 2.4 mg L−1
(±0.0, n = 144), the highest in the study period and indicative of ecosystem recovery. After three years of control efforts, dissolved oxygen, pH, and specific conductance returned to levels recorded prior to Salvinia molesta introduction. This ecosystem recovery, a first in Puerto Rico, could be attributed to early use of mechanical control and the long-term impact of biological control.
To inform regional conservation planning, we assessed mammalian and avian biodiversity in the Djéké Triangle, which is an intact forest with long-term research and tourism focused on western lowland gorillas (Gorilla gorilla gorilla). This critical region serves as a conservation conduit between the Nouabalé-Ndoki National Park (NNNP) in the Republic of Congo and the Dzanga-Ndoki National Park in Central African Republic. Wildlife inventories were conducted to determine if biodiversity in the Djéké Triangle (initially part of a logging concession) was equivalent to the NNNP. Camera traps (CTs) were deployed to estimate species richness, relative abundance, naïve occupancy, and activity patterns of medium-to-large species in mixed species and monodominant Gilbertiodendron forests that comprise the majority of regional terra firma. Species inventories were collected from CTs positioned on a grid and at termite nests throughout the Djéké Triangle and compared to CTs placed in the Goualougo Triangle located within the NNNP. From 10,534 camera days at 65 locations, we identified 34 mammal and 16 bird species. Allaying concerns of wildlife depletion, metrics of species richness in the Djéké Triangle surpassed those of the Goualougo Triangle. Many species were observed to occur across habitats, while others showed habitat specificity, with termite mounds indicated as an important microhabitat feature. Our comparisons of animal activity budgets in different habitat types provide important reference information for other populations and contexts. In conclusion, this study provided empirical evidence of the high conservation value of this region that contributed to increasing the protected status of the Djéké Triangle.
The end-Neoproterozoic transition marked a gradual but permanent shift between distinct configurations of Earth's biosphere. This interval witnessed the demise of the enigmatic Ediacaran Biota, ushering in the structured trophic webs and disparate animal body plans of Phanerozoic ecosystems. However, little consensus exists on the reality, drivers, and macroevolutionary implications of end-Neoproterozoic extinctions. Here we evaluate potential drivers of late-Neoproterozoic turnover by addressing recent findings on Ediacaran geochronology, the persistence of classical Ediacaran macrobionts into the Cambrian, and the existence of Ediacaran crown-group eumetazoans. Despite renewed interest in the possibility of Phanerozoic-style 'mass extinctions' in the latest Neoproterozoic, our synthesis of the available evidence does not support extinction models based on episodic geochemical triggers, nor does it validate simple ecological interpretations centred on direct competitive displacement. Instead, we argue that the protracted and indirect effects of early bilaterian innovations, including escalations in sediment engineering, predation, and the largely understudied impacts of reef-building, may best account for the temporal structure and possible selectivity of late-Neoproterozoic extinctions. We integrate these processes into a generalised model of early eumetazoan-dominated ecologies, charting the disruption of spatial and temporal isotropy on the Ediacaran benthos as a consequence of diversifying macrofaunal interactions. Given the nature of resource distribution in Ediacaran ecologies, the continuities among Ediacaran and Cambrian faunas, and the convergent origins of ecologically disruptive innovations among bilaterians we suggest that the rise of Phanerozoic-type biotas may have been unstoppable.
Many invasive species establish uniquely, or with particular success, in disturbed ecosystems. We propose that for an invasive species, ecosystem disruption may thus constitute an adaptive strategy of niche construction. Accordingly, a species’ propensity to induce large-scale ecosystem change is likely to increase not only its expected damage as an invasive species but also its success as one. We suggest that this perspective, focusing on positive feedback mechanisms driven by invasive species, may be instrumental in understanding and predicting invasive species’ dynamics. It complements the common view, which focuses on invasion dynamics’ effects on native species but not on their effect on the invasive species itself.
The East American mudminnow Umbra pygmaea was introduced to Europe a century ago and is now established in at least six European countries. Although considered harmless and with low spread potential, this fish species shows potential to colonise a broad range of habitats due to its wide environmental tolerance. Stomach content analyses were conducted over 3 years to obtain a first insight into this species' diet, which could indicate the potential to alter the biotic composition of recipient ecosystems. The results showed that this fish can potentially have a high impact on insects, fish, and even amphibians through predation. Species distribution models further indicated that environmental conditions of Central European ecoregions are currently a limiting factor for the spread of this species which seems, at least for now, to be driven by anthro-pogenically driven introductions. Considering the species' potential to be invasive and impact native biota, monitoring of potential spread is recommended.
The behavior of animals can change when they become invasive. Whilst many species demonstrate exaggerations of existing behaviors, signal crayfish (Pacifastacus leniusculus) display a novel burrowing activity in some invaded rivers. Understanding if burrowing is learned or innate is important for modelling the geomorphological effects of invasion into new territories. Mesocosm experiments were undertaken with signal crayfish to investigate the effects of population density, shelter availability, and population provenance on their likelihood to burrow. Crayfish were collected within their native range in the USA; a recently invaded site in the USA; and two well-established invasive populations in the UK—one where burrowing in the field was present, and one population where burrowing in the field was absent. Crayfish from all populations constructed burrows in laboratory experiments. Population density and shelter availability were significant drivers of burrowing. There was no difference in burrowing between the invasive UK populations and the US native population, suggesting that burrowing is an innate, rather than learned, behavior. Therefore, crayfish have the capacity to affect geomorphic processes in any river that they invade, regardless of the source population. However, crayfish from the recently invaded USA river excavated more sediment than crayfish from their native range. These results demonstrate high plasticity of signal crayfish activities and show that innate behavioral strategies not seen in the native range can be activated at invaded sites.
This study aimed to explore the diversity levels of the Orchidacea family in the Koran River area of Sebangau National Park, Central Kalimantan. The research was conducted over a period of 8 months, from August 2021 to March 2022, and involved preparing research proposals, data collection, analysis, and result preparation, research result seminars, and final exams/thesis. The research tools and materials used included a camera, meter, writing tools, machete, compass, computer, calculator, location map, orchid literature book, and tali rapia. Primary data was collected through direct visits to the research location and analyzing orchid plants with the assistance of four field workers. Secondary data was obtained from the people of Central Kalimantan. Sampling of orchid plants was done using the Purposive Sampling technique, and the research plot was carried out using the path method. The study found three genera of orchids, namely Bulbophyllum, Dendrobium, and Eria, in the research area. Four types of orchids were found in the naturally overgrown path (line 1), and nine types of orchids were found in the orchid cultivation route (line 2). The variable data taken were types of terrestrial and epiphytic orchids. This study provides valuable information on the diversity of orchids in Sebangau National Park's Koran River area and highlights the importance of preserving this valuable natural resource.
Commercial afforestation of natural ecosystems is increasing worldwide. There is little information however, on the extent to which biodiversity is being affected by this practice. This especially so for stream fauna, including the conspicuous Odon. Some dragonflies and damselflies may decline when their natural environment is anthropogenically changed and, as a group, they are sensitive to the impact of afforestation. The sites were four pine plantations in KwaZulu-Natal, South Africa.14 environmental factors were recorded along stretches of streams running through each of the four sites. The diversity of Odon. spp. and their abundances along these streams were measured. There was a strong positive correlation between certain abiotic factors, for example, boulder cover and shade, with the local distributions of these insects. Water pH was also a strong correlate. Most spp. required both unpolluted water and a sunlit stream. Particular vegetation type and exact distance of pine trees from the water's edge (so long as they did not shade the stream) were not strong correlates. This meant that species diversity dropped dramatically where the water was completely shaded by a closed canopy, whether it was from natural forest or from exotic trees. It is recommended that no plantation trees should shade a stream edge, and should be planted at least 30m from the water. All highly invasive, dense-canopy weeds, especially Acacia mearnsii, should be removed, and extensive and intensive cattle trampling of the banks avoided.
Alterations induced by beaver (Castor canadensis) provide a striking example of how the animals influence forest ecosystems. Beavers modify stream morphology and hydrology by removing trees, building dams and retaining sediment and organic material in the stream channel. We studied the effect of beaver impoundments on nutrient dynamics of the native forest (Nothofagus sp.) of Isla Grande of Tierra del Fuego (Argentina), by comparing sediments and pond waters of beaver altered and unaltered sites (controls) over a 3 year period. Concentration of organic carbon, nitrogen, phosphorous, and inorganic nitrogen (nitrate-N and nitrite-N) were significantly greater in sediments of beaver sites. Also nitrites and nitrates were higher in beaver pond waters. Resumen. Las alteraciones provocadas por las actividades del castor (Castor canadensis) resultan un ejemplo claro de cómo los animales influencian el ecosistema forestal. Los castores modifican la morfología e hidrología de las cursos de agua por la remoción de árboles, construcción de diques y retención de sedimento y materia orgánica en la cuenca. Nosotros estudiamos el efecto de los endicamientos producidos por el castor sobre la dinámica de nutrientes del bosque de Nothofagus de Tierra del Fuego (Argentina) comparando sedimentos y agua de estanques de sitios alterados por castor y no alterados (controles) durante un periodo de 3 años. Las concentraciones de carbono, nitrógeno orgánico e inorgánico (N-nitrato y N-nitrito) y fósforo fueron significativamente mayores en los sedimentos de sitios alterados. Tambien las concentraciones de nitratos y nitritos fueron significativamente más altas en aguas de estanques de castor.
Alien species (those carried outside their original ranges by human activities) have strongly affected the distribution and abundance of mollusks in many North American fresh waters. The best known of these aliens in North America is the zebra mussel (Dreissena polymorpha), which has nearly extirpated native unionid clams from infested lakes and rivers by fouling their shells and outcompeting them for food. Zebra mussels also have reduced populations of native sphaeriid clams, and both increased and reduced populations of snails. The effects of the other well-known alien bivalve in North America, Corbicula fluminea, are surprisingly poorly known. Corbicula probably caused some populations of native bivalves to decline, but other native populations seem to coexist with Corbicula. Several plausible mechanisms of interaction between Corbicula and the native biota have been proposed, but not demonstrated. Other aliens, including the recently arrived snail Potamopyrgus antipodarum, probably compete strongly with native freshwater mollusks under some circumstances. Several alien species, such as round goby and some sunfishes and crayfishes introduced outside their native ranges in North America, are effective predators on native mollusks and have strong effects on their distribution and abundance. Other aliens (particularly aquatic plants) affect mollusks by altering the food base or the physicochemical environment. Alien species can affect water quality, cycling of contaminants, and performance of biological indices of water quality. Because of ineffective control of aliens in North America, they may be an increasingly important factor in molluscan distribution as new species arrive from other continents and established species spread throughout the continent.
There is no summary to this chapter - only a two-page section entitled 'Summary and Conclusions' which is too long to reproduce here.
Antarctic Ecosystems comprises 55 papers presented at the Fifth Symposium on Antarctic Biology held under the auspices of the Scientific Committee on Antarctic Research (SCAR) in Hobart, Australia, 29 August - 3 September, 1988. Both short- and long-term changes in ecosystems and community structures caused by natural and human factors were discussed to help understand the ecological processes taking place in a changing environment. The variability of ecological factors must be known for the development of realistic monitoring strategies and sound conservation practices.
In 1967, a breeding bird census was conducted on a 24.28-ha plot in a virgin red spruce-Fraser fir forest on Mt. Guyot in Great Smoky Mountains National Park. The survey was made prior to infestation of Fraser fir by the introduced balsam woolly aphid. In 1985 an effort was made to duplicate the original census on the same plot after aphid infestation and the subsequent destruction of most of the old-growth spruce-fir forest. Two territorial species present in 1967 were absent in 1985, and three new early successional species were present. Most of the 11 species present during both census years had decreased in density.
The avian community of montane coniferous forests changed substantially over 21 years In response to the introduction of the balsam woolly adelgid insect (Adelges piceae) and the resulting death of endemic Fraser fir trees (Abies fraseri), These relict forests are at the southern limit of their distribution on the highest ridges of the southern Appalachian Mountains. We combined a historical study at Mount Collins in the Great Smoky Mountains with a geographic comparison of sites within five southern Appalachian mountain ranges variably affected by the adelgid At Mount Collins, fir was virtually eliminated and canopy cover reduced to half its previous level. Long-term data front Mount Collins showed that the combined density for all breeding birds also declined by half Of the common territorial species present in 1974, 10 of 11 declined, Ci by more than 50%. Some species are neat local extinction. Canopy-and subcanopy-foraging species declined more than near-ground and trunk-foraging species. In addition, invasions of birds characteristic of open and disturbed forests have diluted the boreal character of the avifauna. These changes are consistent with two other long-term studies and are not explained by regional population trends. In the other southern Appalachian mountain ranges where habitat is not as extensive, the adelgid invasion resulted in greater declines in avian abundance, stronger effects on sensitive species, and more pronounced invasions by successional species. Sensitive species in the southern Appalachian studies were also strongly affected in other studies of forest disturbance by fire and logging. The extent of relatively pristine spruce-fir forest and the population pools in other forest types in the Great Smokey Mountains appear, to hn ve buffered the effects of forest decline on the bird community.
Disturbance is both a major source of temporal and spatial heterogeneity in the structure and dynamics of natural communities and an agent of natural selection in the evolution of life histories. This review emphasises the impact of disturbance on the numerical abundance of populations and on the relative abundance of species in guilds and communities. Disturbance also has an important influence on ecosystem-level processes, eg primary and secondary production, biomass accumulation, energetics, and nutrient cycling. Assemblages of sessile and mobile organisms are subject to disturbance with rather different responses. -from Author
The chief prey of feral house mice on Marion Island is larvae of the flightless moth Pringleophaga marioni Viette (Tineidae), which constitute about 50% of their diet throughout the year. The litter-dwelling, detritivorous larvae take more than 2 years to mature, during which time they process (i.e. fragment, ingest and excrete) large quantities of litter. At an annual mean biomass of 9.3 kg ha−1, and an individual consumption rate of approximately 0.6 × their own mass in litter daily, P. marioni larvae are estimated to process at least 1500 t of litter annually on Marion Island’s vegetated coastal plain (all results expressed as dry mass). The larvae facilitate the release of nutrients from plant litter through their feeding activity and the resultant enhancement of microbial decay. Mice remove daily 65 g ha−1 or 0.7% of the standing crop of P. marioni larvae on the island’s coastal plain. The indirect effect of mouse predation, through the removal of a large proportion of decomposer biomass and subsequent impediment of nutrient mineralization, has implications for the functioning of the decomposer subsystem of the Island’s terrestrial ecosystem. Since mice and their prey appear to be in dynamic or even stable equilibrium, the direct impact of mice through predation may be eclipsed by these indirect detrimental effects to nutrient cycling.
Population, community, and ecosystem ecologists historically have asked different kinds of questions about nature, and as a result have defined domains of study quite differently. In this chapter, the general question “Why link species and ecosystems?” will be explored from an ecosystem ecologist’s point of view. I begin by considering the subdisciplinary distinctions in ecology: how they are reflected in questions asked, what theories underlie them, and what areas are ripe for integration.
Examples drawn largely from stream ecology are presented in a discussion of redundancy and keystone species. The primary conclusion is that these phenomena occur in nature, are applicable to ecosystem processes as well as community structure, and should be predictable from ecosystem and species characteristics. Although available data do not always allow prediction of which species is likely to affect ecosystem functioning, use of variables such as biomass or production as indicators of a given species’ status may lead to misinterpretation. Concepts of interaction strength are applicable to ecosystem studies.
Species occur in nature as members of interactive assemblages, and their interactions may affect ecosystem functioning in either subtle or dramatic ways. Given the attention that has been paid by community ecologists to biotic interactions, does an understanding of these processes contribute to understanding ecosystem functioning? A complex stream system and conceptual model are described for the purpose of highlighting questions relevant to integrating biotic interactions, disturbance, and ecosystem functioning.
Finally, some loose ideas on the themes of disturbance and stability, patchiness, and scale as potential starting points for linking species and ecosystems are given in the final section. To facilitate interaction between population/community and ecosystem/landscape ecology, units of study should be spatially based.
The SCOPE Programme on the Ecosystem Function of Biodiversity is aimed at ascertaining whether it is necessary to prevent the predicted man-induced extinction of much of the Earth’s current biodiversity (Ricklefs et al. 1990) on the grounds of securing the adequate functioning of global life-support systems. Given this background, it would appear inappropriate to focus on oceanic islands, as they constitute a minute fraction of the Earth’s total land surface and, accordingly, are likely to make an infinitesimally small contribution to global fluxes in the biosphere. Even on simple biodiversity conservation grounds, a focus on islands within a global programme is of doubtful validity, as most biodiversity is located on the continents and in the oceans.
Keystone species and community effects of biological introductions planned introductions in biological control surface transport of micro-organisms soil and groundwater transport of micro-organisms aerial transport of bacteria physiochemical and biological factors affect the transfer of genetic information among micro-organisms genetic exchange and genetic stability in bacterial populations models for the population dynamics of transposable elements in bacteria fitness and gene stability quantitative approaches to questions about the spread of recombinant genes or recombinant organisms.
Nature reserves are often considered to be assemblages of species in natural or semi-natural communities, but in many parts of the world they also contain exotic species that interact with the native flora and fauna. Data for 4 invasive species within the British Isles are analysed: Indian balsam Impatiens glandulifera, rhododendron Rhododendron ponticum, mink Mustela vison and coypu Myocastor coypus. Rates of spread have been variable, usually increasing after an establishment phase. Discussion concentrates on assessing the impact of invasive species, on deciding whether control measures are feasible and/or desirable, on deciding whether or not nature reserves are less prone to invasion than other habitats, and on assessing wildlife conservation values when invasive species are present. -from Author
Interactions between organisms are a major determinant of the distribution and abundance of species. Ecology textbooks (e.g., Ricklefs 1984, Krebs 1985, Begon et al. 1990) summarise these important interactions as intra- and interspecific competition for abiotic and biotic resources, predation, parasitism and mutualism. Conspicuously lacking from the list of key processes in most text books is the role that many organisms play in the creation, modification and maintenance of habitats. These activities do not involve direct trophic interactions between species, but they are nevertheless important and common. The ecological literature is rich in examples of habitat modification by organisms, some of which have been extensively studied (e.g. Thayer 1979, Naiman et al. 1988).
Fledging success was determined at nests of urban Red-shouldered Hawks (Buteo lineatus) in California. Fourteen of 27 nests in 1994 and 38 of 58 nests in 1995 were in exotic trees, predominantly eucalyptus (Eucalyptus spp.). Nesting and fledging success were higher in exotic trees than in native trees in both years, owing in part to greater stability and protective cover. Most nest trees in upland areas (>100 m from water) were exotics, and even in riparian habitats, where tall native cottonwoods (Populus fremontii) and sycamores (Platanus racemosa) were available, Red-shouldered Hawks selected eucalyptus more often than expected based on their availability. Of the habitat and nest-tree variables measured at each nest, only nest-tree height and diameter were significantly associated with reproductive success, suggesting that large, sturdy trees provided the best nest sites. Red-shouldered Hawk populations in the study area have likely benefited from the planning of exotic eucalyptus and fan palms. Reproductive success was not affected by the degree of urbanization around nest sites, as many successful nests were found in heavily urbanized areas close to human activity.
Invasions by non-native plants threaten the preservation of many plant and animal species and communities throughout North America. These pest species compete with and displace native plants and animals and may substantially alter ecosystem functions (e.g., fire occurrence and frequency, nutrient cycling). Awareness of these threats among wildland managers has greatly increased in the last decade. In a recent poll of National Park superintendents, 61% of 246 respondents indicated non-native plant invasions were moderate or major problems at their parks. Likewise, over 60% of Nature Conservancy stewards nationwide polled in 1992 indicated weeds were among their top 10 management problems, listing nearly 200 problem species. Over 12% indicated weeds were their worst problem. Weed control programs are now in place in wildlands across the continent, employing techniques ranging from manual removal, mechanical methods, prescribed fire, judicious use of herbicides, the release of biological control agents, and encouragement of native competitors. The most successful endeavors follow an adaptive management strategy in which plans based on the goals of the preserve are developed, weeds that interfere with those goals are identified and prioritized, and control measures are selected and implemented where appropriate. Emphasis is placed on preventing new weeds from becoming established and on early detection and elimination of incipient infestations. Managers must focus on the vegetation or community desired in place of the weeds and periodically re-evaluate whether their programs are moving them toward this objective. Control of weeds in wildlands poses unusual problems not ordinarily met in other systems which offer challenging research opportunities for weed scientists and ecologists.
Examines how vegetation structure can affect the species richness and abundance of herbivorous insects, concentrating on the responses of sap-feeders of the order Homoptera, including planthoppers (Delphacidae, Issidae), leafhoppers (Cicadellidae), spittle bugs (Cercopidae), aphids (Aphididae) and scale insects (Coccoidea). Particular attention is paid to dispersal ability, overwintering and other traits that influence a sap-feeder's ability to colonise and persist on its host plants. Plant persistence and severe climates are among factors which alter the species composition and life histories of sap-feeder guilds, thereby modifying the guild's response to changes in vegetation structure. -from Authors
South Florida contains more conspicuous introduced plants and animals than any other region in the continental United States. At the same time the region also encompasses one of the largest contiguous complexes of preserved ecosystems in the eastern U.S. (Fig. 13.1.). Everglades National Park, dedicated in 1947, covers about 2500 (terrestrial) km2; the Big Cypress National Preserve, established only a decade ago, occupies 2300 km2; and the Fakahatchee State Preserve, whose acquisition by the State of Florida began in 1974, contains about 200 km2. An additional 3600 km2 are included in the three diked basins with modified hydroperiods controlled since 1949 by the South Florida Water Management District. Most of the introduced species that cause concern in South Florida were present before government agencies gained control of these lands.
Publisher Summary This chapter discusses the positive-feedback switches in plant communities. A vegetation positive-feedback switch is a process in which a community modifies the environment, making it more suitable for that community. Positive-feedback switches operate by modifying any of several features of the environment, including water, pH, soil elements, light, temperature, wind, fire, or allelopathic toxins. The four types of switch can be distinguished as: (1) one-sided switch, where a single community modifies the environment of the patches it occupies, (2) reaction switch, where the community additionally modifies the patches it is not in, but in the opposite direction, (3) symmetric switch, where communities of both alternative states modify the same factor of their environment, but in opposite directions, and (4) two-factor switch, where the two communities both modify their environments, but in different factors. The positive-feedback switches producing four major vegetational effects (A–D): a stable vegetational mosaic may be produced in a previously uniform environment(situation A), or a vegetational gradient caused by environmental change can be intensified to give a sharp boundary (situation B). These mosaics and boundaries can occur at a wide variety of spatial scales, from landscape-scale to individual plant-scale. Switches can also sharpen or displace temporal boundaries: succession can be accelerated (situation C) or delayed (situation D). Not all of these effects can be produced by all types of switch; in particular, a one-sided (type 1) switch cannot produce a stable mosaic.
As one component of invasion resistance, native predators may consume non-indigenous species in the invaded habitat. I studied the contribution of predation to mortality in populations of a potentially dominant, habitat-modifying mussel (Musculista senhousia) which has been introduced from Asia to California. In short-term (2 to 4 wk) experiments performed in San Diego Bay, a muricid snail (Pteropurpura festiva) decimated transplanted mussel populations by up to 65% within 2 wk. Crustacean predators were responsible for mortality rates of <4 %. The experimental removal of byssal cocoons in M, senhousia did not increase the susceptibility of the mussel to predation compared to unmanipulated individuals. In all experiments, predation was more intense inside an eelgrass (Zostera marina) bed compared to either unvegetated clearings or to sand flats adjacent to the eelgrass bed. In a 4 mo predator exclusion experiment, mussel numbers were reduced by 95 % in the eelgrass compared to a decimation of only 36 and 50 % on the unvegetated sand flat above and below the Z, marina bed, respectively. An aquarium experiment revealed that P, festiva favored M. senhousia over an abundant native clam in San Diego Bay, Chione undatella. In southern California, predation contributes significantly to the resistance of the recipient community to invasion and may locally prevent M. senhousia from establishing dense, habitat-modifying beds with potential effects on native infauna and eelgrass.
Oceanic islands represent a set of systems in which biological diversity varies as a consequence of remoteness or size, not environment; they are also generally simpler than continental ecosystems. Islands therefore provide an opportunity to determine the direct effects of biological diversity on ecosystem function. This volume addresses the following topics: components of biological diversity on islands and their patterns of variation; the modern threats to the maintenance of biological diversity on islands; the consequences of island biology and its modification by humanity regarding aspects of ecosystem function; the global implications of islands for conservation; and how islands can help one to understand the processes inducing changes throughout the world.
In recent years, there has been a growing interest in understanding the ecological importance of ecosystem engineers. In this paper we argue that parasites, through the phenotypic alterations they induce in their hosts, are likely to be involved in engineering processes for at least two reasons. First, when ecosystem engineers are themselves infected, phenotypic alterations induced by parasites can interfere with host traits involved in the engineering processes. Secondly, parasites themselves can be ecosystem engineers since the phenotypic alterations of hosts directly modify the habitat of all the species inhabiting free-living organisms. This new research area at the interface between ecology and parasitology should improve our understanding of the ecological consequences of phenotypic alterations induced by parasites in ecosystems.
The plants and Homoptera on three old fields in southeast Michigan were sampled. Within fields, correlations between plant and insect diversity were generally weak. But using all samples from three fields, evenness (J) and diversity (H) of the insects were highly correlated with plant evenness and plant diversity, respectively. For example, 72% of the variance in insect H could be accounted for by variation in plant H. Number of species (S) showed a positive but weaker correlation. When correlations were based on the pooled samples from each field, all three statistics for insects were highly correlated with those for the plants. Insect H was also highly correlated with plant structure (foilage height diversity FHD) over all three fields. These two measures of plant diversity (H and FHD) were highly correlated and were equally good correlates of insect H. Together they accounted fir 79% of the variance in insect H. This extends to insects a correlation between plant and animal diversity, already well established for birds and possibly true for lizards and rodents. It leaves open the unresolved question as to whether plant structure or plant species diversity is more important.
(1) The appearance of the British farming landscape has been drastically altered over the last decade by the death and felling of elm trees. This paper attempts to assess the effect of this on bird numbers, distributions and territory sizes on a farm in Dorset, England. (2) Comparison of bird numbers with an index for unaffected farms showed significant differences, but not in the expected direction if elm death is detrimental. (3) There were few indications that elm death caused birds to redistribute among hedges. Conversely, elm felling had a far greater impact and affected species in relation to their use of dead elms. (4) Elm death increased the size of chaffinch territories but not of the other five species examined. However, after elm felling, the territories of great and blue tits were also larger. (5) Elm death alone is probably not of great significance to most bird species (with some notable exceptions), but felling causes reductions in numbers and species diversity. Some species may be more sensitive to operations incidental to felling, e.g. accidental damage to live trees or ditch clearance. (6) The question of how farmland birds react to habitat change is complicated by the interaction of habitat choice and population levels which is poorly understood. In particular, the contribution of breeding success in hedgerows to overall population levels, and to what extent hedgerow populations are maintained by recruitment from elsewhere, deserve special attention.
The European wild boar Sus scrofa L., an exotic species, entered the Great Smoky Mountains National Park during the 1940s. Because of their high reproductive potential and their adverse impact on the native flora and fauna, the wild hogs have become a major management problem within the park. During the summer of 1973, quadrat sampling of the canopy and understory of Gray Beech Forest was conducted in both the hog-free and hog-occupied sectors of the park. Removal of the herbaceous understory and other types of hog rooting damage showed no direct relationship to the importance of any individual canopy species, including beech Fagus grandifolia. Cover reduction was related, however, to the importance of mesic herbs in a plot. Polynomial and Gaussian regressions of cover against indirect ordination axes indicate that hog rooting within Gray Beech Forest is most intense in the mesic portion of the moisture gradient and decreases both on xeric, south-facing slopes and on more mesic, north-facing slopes. Understory cover in the most severely damaged plots was between 2% and 15%, while understory cover in hog-free plots in the same position on the moisture gradient was usually between 80% and 110%. Hog rooting significantly reduced the number of species in the most disturbed plots but had no effect on the H' values of the largest plot sizes sampled. High H' values for the damaged plots are related to the lack of succession after disturbance of the understory without removal of the canopy.
The feeding habits of the Snail Kite (Rostrhamus sociabilis) were observed intermittently from 1967-1980 in Florida, USA. Approximately 97% of all observed foraging bouts were over marshes having sparse emergent vegetation. The visually-hunting kite was unable to forage over floating mats of exotic water hyacinth (Eichhornia crassipes). Male kites had shorter hunting bouts than females. For still-hunting, the birds' perches ranged from 0.15-4.6 m high and captures occurred an average of 5.8 m from perches. Females were significantly more successful (70%) for course-hunting than males (48%), but I found no difference for still-hunting. Birds tended to forage throughout the day, except for occasional inactive periods by some individuals during midday. On cooler days, foraging commenced slightly later in the morning than on warmer days. Kites probably capture freshwater apple snails (Pomacea paludosa) as deep as 16 cm. Capture rates for adults generally ranged from 1.7-3.4 snails per hour. Kites usually foraged over a common hunting area, and defense of foraging sites was rare. Handling of snails, from the kite's arrival at the feeding perch until consumption, averaged 2.7 min, with no significant difference between sexes. However, adult females were more efficient at the extraction portion of this process than were adult males. Snails were usually extracted before being brought to the nest, except in the latter part of the nestling period when some snails were extracted at or near the nest and some were brought intact. Adults feed small chicks bill to bill, and both parents generally shared equally in care of the young, except at two nests where the females did 67% or more of the feeding. Mean length of snails taken by kites was 42.8 mm (range 25.2-71.3, n=697) and mean diameter was 45.8 mm (range 27.4-82.4, n=697). The most common size classes taken were 30-60 mm in length and diameter. Nutritional and gross energy values were determined for apple snails. Female snails with albumen glands removed (versus males or mixed samples of both sexes of complete tissue or with viscera removed) had the highest caloric value (x̄=4.04 kcal/g, n=10). Kites cast pellets, a behavior documented here for the first time.