scholarly journals Direct and indirect interactions of native and introduced species in coastal habitats

2021 ◽  
Author(s):  
◽  
Susanne Claudia Krejcek
Keyword(s):  
Invasive Species ◽  
Native Species ◽  
Plant Density ◽  
Spatial Scales ◽  
Stress Gradient ◽  
Natural Populations ◽  
Plant Morphology ◽  
Abiotic Conditions ◽  
Bare Sand ◽  
Marram Grass

<p>Current research has emphasized the need to identify and quantify the effects of positive and negative interactions (both direct and indirect) between species, taking into account the influence of abiotic conditions and spatial scales. In this research it is particularly challenging to adequately assess and predict the impact of introduced species on native communities. This study examined interactions of introduced and native species on coastal sand dunes in New Zealand. Substantial areas of this habitat have become dominated by the highly competitive exotic sand-binder marram grass (Ammophila arenaria) and other exotic weeds, replacing native species, including the native eco-engineering spinifex (Spinifex sericeus). First, I examined direct interactions (competition and facilitation) between marram and spinifex along an abiotic stress gradient where experimental plots were subject to different restoration management techniques. In my large-scale dune experiment I planted 2475 spinifex seedlings in three different treatments (bare sand, live marram, dead marram) including an unplanted control, and monitored the plots for one year along exposed marram grass-dominated dune fields near Whanganui, West Coast, North Island/New Zealand. The stress gradient hypothesis predicts facilitation will be greatest where stress is most severe. I hypothesized facilitation of spinifex plantings and other self-colonizing plants in dead sprayed marram compared to live marram and a change of interaction between spinifex and marram grass along an abiotic stress gradient. Spinifex survival was not significantly different across treatments, but the interaction between treatment and location from the sea as well as pre-existing marram cover were significant predictors of plant growth in a linear mixed effect model. Exotic weeds such as Senecio elegans, Conyza canadensis, dandelions and legumes were facilitated by sprayed marram grass relative to abundances in live marram grass, while grasses other than marram grass and spinifex performed best in bare sand, in the absence of competitors. For S. elegans, abundances were higher closer to the sea. Spinifex growth was greatest in plots closest to the sea. Comparing spinifex growth in live marram grass and dead marram showed similar patterns at the fore, mid and back dune, but sprayed maram showed better facilitation of spinifex. For restoration plantings it is only recommended to plant into dead marram if the site is not weed prone as weeds were facilitated in the same way as spinifex and in some instances appeared to hinder spinifex growth. Crucial for a successful conversion from marram to spinifex is that the initial marram cover is not too high prior to spraying- lower densities allow for better spinifex growth. Second, I examined indirect competition with a survey of natural populations and a common garden experiment at a shingle beach. I was interested in determining the influence of plant density at different spatial scales as well as plant morphology on insect abundances. I studied indirect interactions by choosing native and introduced Senecio spp. as host plants for insect colonization and incorporated fine scale plant density (50cm radius circle, area = 0.8 m²) and coarse scale plant density (6m quadrat annulus, area = 32 m²) as predictors for insect colonization in addition to plant morphology. I surveyed Senecio spp. over a period of three growth seasons and conducted an experiment where I manipulated densities of pairs of species of either introduced Senecio elegans, S. skirrhodon and native S. lautus. My survey of natural populations and the manipulative field experiment show a negative impact of high conspecific and heterospecific plant density on the colonization of the seed head predator fly Sphenella fascigera. Along with plant density, plant size was a significant predictor of insect abundances. Higher densities of introduced S. elegans indirectly facilitated S. lautus at fine spatial scales by reducing the incidence of S. fascigera. This supports the resource dilution hypothesis which predicts higher insect herbivore numbers on isolated resource patches. Thus, my results provide empirical evidence for apparent facilitation of a native plant by an introduced plant via a shared herbivore. For future assessments of the impacts of invasive species it will be important to consider the net-outcome of direct and indirect competitive and facilitative interactions. In particular, for restoration purposes in stressful environments removal of invasive species may have to occur in a carefully controlled manner taking into account the abiotic conditions and spatial scales at which interactions occur.</p>

Sensitivity of Modeled Channel Hydraulic Variables to Invasive and Native Riparian Vegetation

2017 ◽  
Vol 8 (4) ◽  
pp. 47-61 ◽  
Author(s):  
Adriana E. Martinez
Keyword(s):  
Invasive Species ◽  
Riparian Vegetation ◽  
Native Species ◽  
Plant Density ◽  
Dominant Role ◽  
Individual Species ◽  
Stream Velocity ◽  
Plant Characteristics ◽  
Vegetation Patches ◽  
Hydraulic Variables

Quantifying the roughness of riparian vegetation is important where it plays a dominant role by reducing water velocity. Vegetation roughness was calculated based on the plant characteristics of three dominant herbaceous plants, including one invasive, along the Sprague River, Oregon. E. palustris and invasive P. arundinacea exhibit higher and similar roughness values whereas C. vesicaria is lower. To determine differences, hydraulic channel conditions were modeled within NAYS 2DH. First, current conditions were modeled by populating the channel banks with roughness, plant density, and height of vegetation patches. Next, along the same reach, monocultures were modeled assuming dominance of individual species. In comparing the two native species to the invasive species, monoculture conditions show that plant density and roughness causes the native E. palustris to have the highest ability to decrease stream velocity. In areas where the invasive species is outcompeting E. palustris, such changes could cause increases in velocity and less stable bank surfaces.

Restoring Abandoned Agricultural Lands in Cold Desert Shrublands: Tradeoffs between Water Availability and Invasive Species

2014 ◽  
Vol 7 (1) ◽  
pp. 176-189 ◽  
Author(s):  
Jeanne C. Chambers ◽  
Eric P. Eldredge ◽  
Keirith A. Snyder ◽  
David I. Board ◽  
Tara Forbis de Queiroz ◽  
...  
Keyword(s):  
Invasive Species ◽  
Water Relations ◽  
Invasive Plants ◽  
Native Species ◽  
Plant Density ◽  
Native Plant ◽  
Agricultural Lands ◽  
Cold Desert ◽  
Positive Effects ◽  
Density And Biomass

AbstractRestoration of abandoned agricultural lands to create resilient ecosystems in arid and semi-arid ecosystems typically requires seeding or transplanting native species, improving plant–soil–water relations, and controlling invasive species. We asked if improving water relations via irrigation or surface mulch would result in negative tradeoffs between native species establishment and invasive species competition. We examined the effects of sprinkler irrigation and straw mulch on native seed mixtures planted in two consecutive years in an abandoned agricultural field in a cold desert shrubland in southwestern Nevada, USA. Restoration effects differed among years because of contingency effects of growing season conditions. Precipitation was low during the first year and seeded plant density and biomass increased in response to irrigation. Precipitation was relatively high during the second year, seeded plant densities and biomass were generally high, and irrigation had inconsistent effects. Mulch increased native plant cover in the absence of irrigation during the dry year. Invasive plant biomass and cover also were influenced by year, but irrigation increased invasive plants regardless of precipitation. Positive effects of irrigation on seeded plant density, cover, and biomass outweighed negative tradeoffs of increases in invasive plants. In ecosystems with highly variable precipitation, the most effective restoration strategies will most likely be adaptive ones, requiring determination of timing and amount of irrigation based on precipitation, native plant establishment, and invasive species composition and abundance.

High predatory efficiency and abundance drive expected ecological impacts of a marine invasive fish

2020 ◽  
Vol 637 ◽  
pp. 195-208 ◽  
Author(s):  
EM DeRoy ◽  
R Scott ◽  
NE Hussey ◽  
HJ MacIsaac
Keyword(s):  
Invasive Species ◽  
Native Species ◽  
Ecological Impact ◽  
Marine Species ◽  
Ecological Impacts ◽  
Negative Effects ◽  
Marine Predator ◽  
Eastern Gulf Of Mexico ◽  
Red Grouper ◽  
Per Capita

The ecological impacts of invasive species are highly variable and mediated by many factors, including both habitat and population abundance. Lionfish Pterois volitans are an invasive marine species which have high reported detrimental effects on prey populations, but whose effects relative to native predators are currently unknown for the recently colonized eastern Gulf of Mexico. We used functional response (FR) methodology to assess the ecological impact of lionfish relative to 2 functionally similar native species (red grouper Epinephelus morio and graysby grouper Cephalopholis cruentata) foraging in a heterogeneous environment. We then combined the per capita impact of each species with their field abundance to obtain a Relative Impact Potential (RIP). RIP assesses the broader ecological impact of invasive relative to native predators, the magnitude of which predicts community-level negative effects of invasive species. Lionfish FR and overall consumption rate was intermediate to that of red grouper (higher) and graysby grouper (lower). However, lionfish had the highest capture efficiency of all species, which was invariant of habitat. Much higher field abundance of lionfish resulted in high RIPs relative to both grouper species, demonstrating that the ecological impact of lionfish in this region will be driven mainly by high abundance and high predator efficiency rather than per capita effect. Our comparative study is the first empirical assessment of lionfish per capita impact and RIP in this region and is one of few such studies to quantify the FR of a marine predator.

scholarly journals Long Term Interactions of Native and Invasive Species in a Marine Protected Area Suggest Complex Cascading Effects Challenging Conservation Outcomes

Diversity ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 71
Author(s):  
Charalampos Dimitriadis ◽  
Ivoni Fournari-Konstantinidou ◽  
Laurent Sourbès ◽  
Drosos Koutsoubas ◽  
Stelios Katsanevakis
Keyword(s):  
Invasive Species ◽  
Native Species ◽  
High Performance ◽  
Marine Protected Area ◽  
Habitat Degradation ◽  
Population Increase ◽  
Rocky Reef ◽  
Cascading Effects ◽  
High Level

Understanding the interactions among invasive species, native species and marine protected areas (MPAs), and the long-term regime shifts in MPAs is receiving increased attention, since biological invasions can alter the structure and functioning of the protected ecosystems and challenge conservation efforts. Here we found evidence of marked modifications in the rocky reef associated biota in a Mediterranean MPA from 2009 to 2019 through visual census surveys, due to the presence of invasive species altering the structure of the ecosystem and triggering complex cascading effects on the long term. Low levels of the populations of native high-level predators were accompanied by the population increase and high performance of both native and invasive fish herbivores. Subsequently the overgrazing and habitat degradation resulted in cascading effects towards the diminishing of the native and invasive invertebrate grazers and omnivorous benthic species. Our study represents a good showcase of how invasive species can coexist or exclude native biota and at the same time regulate or out-compete other established invaders and native species.

scholarly journals Complex community responses underpin biodiversity change following invasion

2021 ◽  
Author(s):  
Alessandra R. Kortz ◽  
Anne E. Magurran
Keyword(s):  
Invasive Species ◽  
Species Richness ◽  
Spatial Scales ◽  
Species Abundance ◽  
Ecological Systems ◽  
Multi Scale ◽  
Mechanistic Approach ◽  
Α Diversity ◽  
Biodiversity Change ◽  
Insight Into

AbstractHow do invasive species change native biodiversity? One reason why this long-standing question remains challenging to answer could be because the main focus of the invasion literature has been on shifts in species richness (a measure of α-diversity). As the underlying components of community structure—intraspecific aggregation, interspecific density and the species abundance distribution (SAD)—are potentially impacted in different ways during invasion, trends in species richness provide only limited insight into the mechanisms leading to biodiversity change. In addition, these impacts can be manifested in distinct ways at different spatial scales. Here we take advantage of the new Measurement of Biodiversity (MoB) framework to reanalyse data collected in an invasion front in the Brazilian Cerrado biodiversity hotspot. We show that, by using the MoB multi-scale approach, we are able to link reductions in species richness in invaded sites to restructuring in the SAD. This restructuring takes the form of lower evenness in sites invaded by pines relative to sites without pines. Shifts in aggregation also occur. There is a clear signature of spatial scale in biodiversity change linked to the presence of an invasive species. These results demonstrate how the MoB approach can play an important role in helping invasion ecologists, field biologists and conservation managers move towards a more mechanistic approach to detecting and interpreting changes in ecological systems following invasion.

scholarly journals Diet composition of the invasive red-whiskered bulbul Pycnonotus jocosus in Mauritius

2010 ◽  
Vol 26 (3) ◽  
pp. 347-350 ◽  
Author(s):  
Jannie Fries Linnebjerg ◽  
Dennis M. Hansen ◽  
Nancy Bunbury ◽  
Jens M. Olesen
Keyword(s):  
Invasive Species ◽  
Introduced Species ◽  
Native Species ◽  
Diet Composition ◽  
Ecological Perspective ◽  
Positive Interactions ◽  
Invasional Meltdown ◽  
Ecological Processes ◽  
Successful Establishment ◽  
The Impact

Disruption of ecosystems is one of the biggest threats posed by invasive species (Mack et al. 2000). Thus, one of the most important challenges is to understand the impact of exotic species on native species and habitats (e.g. Jones 2008). The probability that entire ‘invasive communities’ will develop increases as more species establish in new areas (Bourgeois et al. 2005). For example, introduced species may act in concert, facilitating one another's invasion, and increasing the likelihood of successful establishment, spread and impact. Simberloff & Von Holle (1999) introduced the term ‘invasional meltdown’ for this process, which has received widespread attention since (e.g. O'Dowd 2003, Richardson et al. 2000, Simberloff 2006). Positive interactions among introduced species are relatively common, but few have been studied in detail (Traveset & Richardson 2006). Examples include introduced insects and birds that pollinate and disperse exotic plants, thereby facilitating the spread of these species into non-invaded habitats (Goulson 2003, Mandon-Dalger et al. 2004, Simberloff & Von Holle 1999). From a more general ecological perspective, the study of interactions involving introduced and invasive species can contribute to our knowledge of ecological processes – for example, community assembly and indirect interactions.

scholarly journals Emerging fungal pathogen of an invasive grass: Implications for competition with native plant species

PLoS ONE ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. e0237894
Author(s):  
Amy E. Kendig ◽  
Vida J. Svahnström ◽  
Ashish Adhikari ◽  
Philip F. Harmon ◽  
S. Luke Flory
Keyword(s):  
Invasive Species ◽  
Plant Species ◽  
Fungal Pathogen ◽  
Native Species ◽  
Grass Species ◽  
Leaf Spot Disease ◽  
Native Plant ◽  
Invasive Grass ◽  
Native Plant Species ◽  
Species Specific

Infectious diseases and invasive species can be strong drivers of biological systems that may interact to shift plant community composition. For example, disease can modify resource competition between invasive and native species. Invasive species tend to interact with a diversity of native species, and it is unclear how native species differ in response to disease-mediated competition with invasive species. Here, we quantified the biomass responses of three native North American grass species (Dichanthelium clandestinum, Elymus virginicus, and Eragrostis spectabilis) to disease-mediated competition with the non-native invasive grass Microstegium vimineum. The foliar fungal pathogen Bipolaris gigantea has recently emerged in Microstegium populations, causing a leaf spot disease that reduces Microstegium biomass and seed production. In a greenhouse experiment, we examined the effects of B. gigantea inoculation on two components of competitive ability for each native species: growth in the absence of competition and biomass responses to increasing densities of Microstegium. Bipolaris gigantea inoculation affected each of the three native species in unique ways, by increasing (Dichanthelium), decreasing (Elymus), or not changing (Eragrostis) their growth in the absence of competition relative to mock inoculation. Bipolaris gigantea inoculation did not, however, affect Microstegium biomass or mediate the effect of Microstegium density on native plant biomass. Thus, B. gigantea had species-specific effects on native plant competition with Microstegium through species-specific biomass responses to B. gigantea inoculation, but not through modified responses to Microstegium density. Our results suggest that disease may uniquely modify competitive interactions between invasive and native plants for different native plant species.

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