Pre-invasion Data Research Articles

The influence of non-native invertebrate species in the food web structure of two Neotropical reservoirs

To investigate the influence of non-native aquatic invertebrate species on food web structure, we selected two reservoirs located in the Grande River (upper Paraná River basin, Brazil) with similar fish communities, different age and different taxa introductions history. We quarterly collected fish and benthonic macroinvertebrates samples in the Volta Grande and Funil reservoirs between October 2015 and August 2016. We used conventional methods of diet evaluation to assess the sampled fish and measured the availability of invertebrates (i.e. composition and density) present in the sediment samples from each reservoir. In addition, we performed a structural analysis of trophic interaction networks. Based on the data obtained, it was possible to identify that in Volta Grande most of the energy flow, between benthonic invertebrates (prey) and the fish community (predators), occurred through non-native prey species, especially Limnoperna fortunei and Macrobrachium amazonicum, while in Funil it was shared between non-native and native prey. Species loss simulations indicated that the networks did not differ substantially between random losses and losses between groups. In general, there was a decrease in the probability of occurrence of highly connected species in both reservoirs and between non-native and native species. Results showed that the new interactions among species influenced the importance of the available energy sources for the fish in the Volta Grande reservoir. The presence of non-native prey, especially M. amazonicum, may influence the interaction network structure, promoting community dependence on non-native species to ensure robustness to environmental disturbances. In the absence of pre-invasion data, the comparative study between systems with similar fish communities may provide a better understanding of the impacts caused by the introduction of non-native invertebrate prey.

The final frontier: ecological and evolutionary dynamics of a global parasite invasion.

Studying rapid biological changes accompanying the introduction of alien organisms into native ecosystems can provide insights into fundamental ecological and evolutionary theory. While powerful, this quasi-experimental approach is difficult to implement because the timing of invasions and their consequences are hard to predict, meaning that baseline pre-invasion data are often missing. Exceptionally, the eventual arrival of Varroa destructor (hereafter Varroa) in Australia has been predicted for decades. Varroa is a major driver of honeybee declines worldwide, particularly as vectors of diverse RNA viruses. The detection of Varroa in 2022 at over a hundred sites poses a risk of further spread across the continent. At the same time, careful study of Varroa's spread, if it does become established, can provide a wealth of information that can fill knowledge gaps about its effects worldwide. This includes how Varroa affects honeybee populations and pollination. Even more generally, Varroa invasion can serve as a model for evolution, virology and ecological interactions between the parasite, the host and other organisms.

Diversidad de las comunidades de peces en dos áreas marinas protegidas del Caribe y su relación con el pez león

Lionfish (Pterois volitans) invaded the Caribbean region with the potential to alter the composition and structure of native coral reef fish communities. The objective of this study was to analyze the diversity indices of these fish communities potentially affected by lionfish predation and to compare with pre-invasion data. The study was undertaken in two Caribbean marine protected areas (MPAs): Guanahacabibes National Park (PNG) in W Cuba and Xcalak Reefs National Park (PNAX) in S Quintana Roo. We carried out visual censuses of fish species in reef habitats during the dry and rainy seasons of the period 2013-2015. For this, nine sites were defined and evaluated using stationary counts. Our results showed higher species richness (43.47 ± 5.14) and mean abundance (0.76 ± 1.25) in PNG than in PNAX (40.22 ± 4.96, 0.19 ± 0.46, respectively). Diversity decreased after the arrival of lionfish in a single site of PNG and in two sites of the PNAX, but apparently, these results are more related to the fishing activity effect than to the lionfish presence. Based on the results and assuming that changes in the native fish communities by lionfish may not yet be detected, we recommend to continue the monitoring community descriptions in order to detect future changes in native fish communities.

The impact of the introduced Digitonthophagus gazella on a native dung beetle community in Brazil during 26 years

Following successful establishment in Australia and North America, the South African dung beetle (DB) Digitonthophagus gazella was introduced in Brazil in 1990. We investigated the impact of the exotic species on the native community of 42 native DB species using a unique weekly data set spanning 26 years, including 4 years of pre-invasion data. The invasion of D. gazella was very rapid with abundances increasing by 4 orders of magnitude during the first few years following establishment. We show that the DB diversity shrank to sixty percent of the pre-invasion level. Results from multivariate analyses identified three distinct periods of changes in composition and abundance: before the invasion (BI); after invasion I (AI-I); and AI-II each one characterized by a particular dynamic of the native species. The impacts on the native species differed according to their nesting behavior. Species with the same behavior as D. gazella (tunneler) became less abundant and five species went locally extinct. Dweller species, in contrast, became more abundant. Although the analysis of all species combined showed an increase in abundance and a less oscillatory dynamic in AI-II compared to BI, this was the case only for the dweller species, as the tunnelers showed a tendency to continued decrease throughout the 26-year study. Our results show that a new community was originated as a consequence of the invasion, in which dweller species, particularly Labarrus pseudolividus, are the dominant species and all the tunnelers, including D. gazella, are decreasing in abundance.

Water Quality Improvement of a Reservoir Invaded by an Exotic Macrophyte

AbstractThe aim of this study was to evaluate the effect of the macrophyte waterhyacinth on the water quality of a reservoir in Colombia. Postinvasion water quality assessments were performed during three different hydrological periods and compared with preinvasion data. The results show that water quality has improved, especially in terms of transparency, showing an increase in Secchi disk values from 0.3 to 2 m (1 to 6.6 ft). The analysis strongly suggests that the improvement in water quality is due to the filtering and precipitation effects provided by waterhyacinth. This case highlights the dilemma of managing an invasive species that provides a beneficial ecological service while posing a high ecological risk.

Arthropod invasion disrupts Cycas micronesica seedling recruitment

We recently described characteristics of reproductive effort for the cycad Cycas micronesica on the island of Guam. The data were serendipitously recorded just prior to the devastating invasion of the armored scale Aulacaspis yasumatsui. This invasion decimated the cycad population and after six years of infestation no recruitment is occurring among the survivors. We describe various underlying mechanisms that may explain how this homopteran insect has eliminated host recruitment among categories including plant-pollinator mutualism disruptions, direct damage to reproductive structures, population level responses to declining plant health, and failures of seedlings to establish. Our pre-invasion data on reproductive effort will serve as the benchmark for quantifying how this alien pest is endangering the endemic cycad.

Red Lionfish (Pterois volitans) Invade San Salvador, Bahamas: No Early Effects on Coral and Fish Communities

Biological invaders are a leading contributor to global losses of biodiversity. A recent invader to the waters surrounding San Salvador, Bahamas, the red lionfish, Pterois volitans, was first reported in 2006; by 2009 they were common in waters 2-40 m deep around the island. Our study collected data on coral communities and fish assemblages at three patch reef complexes (Rice Bay, Rocky Point, Lindsay Reef) in 2007, during the initial phase of the invasion, and compared the results to a nearly identical study done in 2001 before P. volitans colonized San Salvador. Prey selection and quantity of consumption by P. volitans were also examined. Coral and fish species richness, diversity, percent cover (corals) and abundance (fish) were similar in 2001 and 2007. Of the 5,078 fish recorded during our study on shallow patch reefs, only two were P. volitans, but they were more prevalent in deeper water along San Salvador’s “wall.” Captured P. volitans ranged in size from 19-32 cm, all longer than maturity length. Pallid goby (Coryphopterus eidolon), black cap basslet (Gramma melacara) and red night shrimp (Rynchocienetes rigens) were the most commonly identified stomach contents. The effects of the successful invasion and increasing population of P. volitans on San Salvador’s reef ecosystem are uncertain at this time; future monitoring of potential changes in coral and fish communities on the patch reefs of San Salvador is recommended to determine if population control measures need to be considered. Initial post-invasion data (2007), along with pre-invasion data (2001), are valuable benchmarks for future studies.

Alterations in Yellowstone Lake Nitrogen Cycling Due to Introduced Lake Trout and Subsquent Decline of Yellowstone Cutthoat Trout

Invasive species may alter processes by indirectly affecting other species in the ecosystem, but indirect affects are difficult to measure and often pre-invasion data were not collected. However, models may be used with empirical relationships and available past data to reconstruct past processes. The introduction of lake trout (Salvelinus namaycush) in Yellowstone Lake may have indirect effects on nitrogen cycling and provide an opportunity to study the effects of an invasive species on lake processes. To estimate how lake trout altered nitrogen cycling in Yellowstone Lake, we measured ammonium (NH4+) uptake by phytoplankton in 2005 and estimate past NH4+ uptake using empirical relationships and past data. Using 1 5N, we measured phytoplankton uptake in 4 areas of Yellowstone Lake. Phytoplankton demanded 4.9 mg N m-2 hr- 1 during the ice-free season of 2005. Uptake was higher at warmer water temperatures and shallower Secchi disk depths (measure of phytoplankton biomass). Using relationships among uptake, water temperature, and Secchi disk depth, we estimated phytoplankton uptake in the past based on historical Secchi disk depths and water temperatures. Water temperatures have increased 0.29.C/decade and Secchi disk depths became 0.53 m/decade deeper over the past 30 years. Using our multiple regression model, phytoplankton uptake did not change between 1976 and 2006. The interaction between warmer water temperatures and deeper Secchi disk depths (a sparser algal assemblage) cancelled out resulting in no changed in modeled uptake. Therefore, when estimating past processes, we should use multiple predictors.

Impacts of zebra mussel on walleye (Stizostedion vitreum) reproduction in western Lake Erie

A walleye spawning shoal (Sunken Chicken Reef) in western Lake Erie was sampled during the spring of 1990 and 1991 to assess the abundance of the zebra mussel Dreissena polymorpha and to determine its impact on walleye reproduction. Mussel abundance ranged from 76 500/m2 at 1.5 m depth to 344 300/m2 at 4.5 m depth at the shoal (1990). Despite the almost total coverage of spawning beds walleye continued to spawn at the shoal, with no apparent effect of the mussels on egg deposition, egg viability, and interstitial dissolved oxygen. Although preinvasion data for walleye egg deposition are not comparable to data from this study, deposition appears adequate based on good indices of recruitment of young-of-the-year walleye derived from resource agency trawling during 1990 and 1991. Thus there appears to have been no adverse impacts of zebra mussel on walleye reproduction in western Lake Erie during 1990 and 1991.

Benthic Macroinvertebrate Communities of Southwestern Lake Ontario Following Invasion of Dreissena

Changes in benthic macroinvertebrate communities inhabiting natural cobble and artificial reef substrates in southwestern Lake Ontario were quantified following invasion of zebra mussels ( Dreissena polymorpha) and “quagga” mussels ( Dreissena sp.). Post- Dreissena invasion data (1991–1992) were compared with pre-invasion data (1983) from the same sites. In 1991–1992, Dreissena comprised 79% and 93% of macroinvertebrates collected at cobble and artificial reef sites, respectively, replacing the amphipod Gammarus fasciatus as the numerically dominant taxon at both sites. Total abundance of non- Dreissena macroinvertebrates was significantly greater at both sites in 1991–1992 than in 1983. Taxa showing the greatest increases in abundance at the cobble site included the annelids Manayunkia speciosa, Spirosperma ferox, and unidentified tubificids; the gastropods Helisoma anceps, Physa heterostropha, Stagnicola catascopium, Valvata tricarinata, Goniobasis livescens, and Amnicola limosa; the amphipod Gammarus fasciatus; and the decapod Orconectes propinquis. At the artificial reef site, significant population increases of Physa heterostropha, Valvata tricarinata, Goniobasis livescens, Amnicola limosa, Gammarus fasciatus and the trichopteran Polycentropus were observed. No taxon was less abundant in 1991–1992 than 1983. Comparisons of macroinvertebrate community similarity in 1983 and 1991–1992 by Morisita's Index, excluding Dreissena, indicated that previously established taxa did not change substantially between 1983 and 1991–1992 at either site. Although many factors may have contributed to the changes observed, our results support theories that Dreissena is facilitating energy transfer to the benthos through pseudofecal/fecal deposition, and that mussel colonies are providing additional habitat for other invertebrate taxa.