Number Of Invaders Research Articles

Analysis Evaluation of Resource Value Effects Territorial Defense by Broad-Tailed and Rufous Humming Birds

Hummingbirds of the species Selasphorous platycercus and Selasphorous rufus were studied in Colorado, where they displayed territorial behaviour at feeders containing 10%, 20%, and 30% sucrose solutions. At each of the three energy availability levels, the number of invaders, the number of territory owners, and the level of Defence were recorded. After being forced out of their breeding area by Rufous Hummingbirds, Broad-tailed Hummingbirds only bother to defend locations of inferior quality. Both Wide-tailed and Rufous hummingbirds, while keeping tabs on important locations, resort to more flamboyant modes of behaviour, such as extended pursuits augmented with chip cries and aimless wing flapping. According to certain probes, a chase is ready to start if chip calls and hovering are any indication. However, I learned that when an intruder was present, it was only natural to want to get rid of them. Hovering and chip calls were utilised to increase the intensity of the chase. Broad-tailed Hummingbirds were less likely than Rufous Hummingbirds to make chip sounds or hover without giving pursuit.

Categorizing threat types and cyber-assaults over Internet of Things-equipped gadgets

AbstractInternet of Things (IoT) gadgets are very attractive globally, and IoT facilities are universal. Their progress has not been ignored, and the number of invaders and outbreaks on IoT and facilities is growing. Because cyber-assaults are zero-trust to the IoT, and the IoT is deeply ingrained in our lives and culture, we must embrace a comprehensive Zero-Trust strategy for cyber defense. As a result, the new model is no longer vulnerable to fear and outbreak on the IoT structure. In this article, an effort is made to categorize threat types and analyze and explain invaders and assaults on IoT gadgets and facilities.

Checklist of the vascular alien flora of Catalonia (northeastern Iberian Peninsula, Spain)

This is an inventory of the vascular alien flora of Catalonia (northeastern Iberian Peninsula, Spain) updated to 2018, representing 1068 alien taxa in total. 554 (52.0%) out of them are casual and 514 (48.0%) are established. 87 taxa (8.1% of the total number and 16.8 % of those established) show an invasive behaviour. The geographic zone with more alien plants is the most anthropogenic maritime area. However, the differences among regions decrease when the degree of naturalization of taxa increases and the number of invaders is very similar in all sectors. Only 26.2% of the taxa are more or less abundant, while the rest are rare or they have vanished. The alien flora is represented by 115 families, 87 out of them include naturalised species. The most diverse genera are Opuntia (20 taxa), Amaranthus (18 taxa) and Solanum (15 taxa). Most of the alien plants have been introduced since the beginning of the twentieth century (70.7%), with a strong increase since 1970 (50.3% of the total number). Almost two thirds of alien taxa have their origin in Euro-Mediterranean area and America, while 24.6% come from other geographical areas. The taxa originated in cultivation represent 9.5%, whereas spontaneous hybrids only 1.2%. From the temporal point of view, the rate of Euro-Mediterranean taxa shows a progressive reduction parallel to an increase of those of other origins, which have reached 73.2% of introductions during the last 50 years. The most important way of introduction is gardening (58.0%), followed by agriculture and commerce, while forestry is marginal. Invasive taxa mainly come from gardening and trade, but the proportion of the latter that become invasive is higher (6.1% and 15.6%, respectively). Most of the established aliens are annual and perennial forbs, while other biological types are less represented. These two types are also dominant among the invasive alien species, although a notable increase of trees and climbers has been observed recently.

Effect of Zebra Mussel Dreissena polymorpha (Pallas, 1771) (Mollusca, Dreissenidae) and Perch Perca fluviatilis (L.) (Pisces, Perciidae) of Different Age Groups on the Structure and Main Characteristics of Macrozoobenthos in Experimental Mesocosms

The composition of macrozoobenthos in experimental mesocosms has been studied. A total of 116 invertebrate taxa are found, with chironomids (50 species), mollusks (25), and oligochaetes (21) the most widely represented. Most of the revealed taxa (61%) are common for Dreissena polymorpha (Pallas, 1771) biocenoses in the Rybinsk Reservoir; other species have invaded mesocosms during the experiment. The minimal number of invaders is found in mesocosms with perch larvae; the maximal is in both variants with the zebra mussel. It is shown that in the absence of zebra mussels those age groups of perch consuming macrozoobenthos reduce its main structural characteristics. The maximum sum of the main structural characteristics is recorded in mesocosms with yearlings of perch and zebra mussels. This indicates a positive environment-forming role of Dreissena polymorpha in benthic communities and the possibility that other invertebrates can use its druses as refuge.

Biotic resistance shapes the influence of propagule pressure on invasion success in bacterial communities.

The number of invaders and the timing of invasion are recognized as key determinants of successful invasions. Despite the recognized importance of "propagule pressure," invasion ecology has largely focused on how characteristics of the native community confer invasion resistance. We simultaneously manipulated community composition and invader propagule pressure in microcosm communities of freshwater bacteria. We show that high propagule pressures can be necessary to establish an invader population, but that the influence of propagule pressure depends on the composition of the resident species. In particular, the number of individuals invading was most important to invasion success when one of the species in a resident community is a strong competitor against other species. By contrast, the timing of invasion was most important when communities had lower growth rates. The results suggest that the importance of propagule pressure varies both between communities and within the same community over time, and therefore have implications for the way we understand the relationship between biotic resistance and invasion success.

A global comparison of plant invasions on oceanic islands

Abstract Oceanic islands have long been considered to be particularly vulnerable to biotic invasions, and much research has focused on invasive plants on oceanic islands. However, findings from individual islands have rarely been compared between islands within or between biogeographic regions. We present in this study the most comprehensive, standardized dataset to date on the global distribution of invasive plant species in natural areas of oceanic islands. We compiled lists of moderate (5–25% cover) and dominant (>25% cover) invasive plant species for 30 island groups from four oceanic regions (Atlantic, Caribbean, Pacific, and Western Indian Ocean). To assess consistency of plant behaviour across island groups, we also recorded present but not invasive species in each island group. We tested the importance of different factors discussed in the literature in predicting the number of invasive plant species per island group, including island area and isolation, habitat diversity, native species diversity, and human development. Further we investigated whether particular invasive species are consistently and predictably invasive across island archipelagos or whether island-specific factors are more important than species traits in explaining the invasion success of particular species. We found in total 383 non-native spermatophyte plants that were invasive in natural areas on at least one of the 30 studied island groups, with between 3 and 74 invaders per island group. Of these invaders about 50% (181 species) were dominants or co-dominants of a habitat in at least one island group. An extrapolation from species accumulation curves across the 30 island groups indicates that the total current flora of invasive plants on oceanic islands at latitudes between c. 35°N and 35°S may eventually consist of 500–800 spermatophyte species, with 250–350 of these being dominant invaders in at least one island group. The number of invaders per island group was well predicted by a combination of human development (measured by the gross domestic product (GDP) per capita), habitat diversity (number of habitat types), island age, and oceanic region (87% of variation explained). Island area, latitude, isolation from continents, number of present, non-native species with a known invasion history, and native species richness were not retained as significant factors in the multivariate models. Among 259 invaders present in at least five island groups, only 9 species were dominant invaders in at least 50% of island groups where they were present. Most species were invasive only in one to a few island groups although they were typically present in many more island groups. Consequently, similarity between island groups was low for invader floras but considerably higher for introduced (but not necessarily invasive) species – especially in pairs of island groups that are spatially close or similar in latitude. Hence, for invasive plants of natural areas, biotic homogenization among oceanic islands may be driven by the recurrent deliberate human introduction of the same species to different islands, while post-introduction processes during establishment and spread in natural areas tend to reduce similarity in invader composition between oceanic islands. We discuss a number of possible mechanisms, including time lags, propagule pressure, local biotic and abiotic factors, invader community assembly history, and genotypic differences that may explain the inconsistent performance of particular invasive species in different island groups.

Invaders Galore!

This 9-page activity illustrates factors that influence increases and decreases in numbers of invaders.

Biodiversity as a barrier to ecological invasion.

Biological invasions are a pervasive and costly environmental problem that has been the focus of intense management and research activities over the past half century. Yet accurate predictions of community susceptibility to invasion remain elusive. The diversity resistance hypothesis, which argues that diverse communities are highly competitive and readily resist invasion, is supported by both theory and experimental studies conducted at small spatial scales. However, there is also convincing evidence that the relationship between the diversity of native and invading species is positive when measured at regional scales. Although this latter relationship may arise from extrinsic factors, such as resource heterogeneity, that covary with diversity of native and invading species at large scales, the mechanisms conferring greater invasion resistance to diverse communities at local scales remain unknown. Using neighbourhood analyses, a technique from plant competition studies, we show here that species diversity in small experimental grassland plots enhances invasion resistance by increasing crowding and species richness in localized plant neighbourhoods. Both the establishment (number of invaders) and success (proportion of invaders that are large) of invading plants are reduced. These results suggest that local biodiversity represents an important line of defence against the spread of invaders.

Invasion of North American drainages by alien fish species

1. Data from the literature were used to document colonization patterns by introduced freshwater fishes in 125 drainages across temperate North America. We analysed this data set to quantify susceptibility to invasion, success of the invaders and changes in species richness.2. Drainages with a high number of impoundments, large basin area and low native species diversity had the greatest number of introduced species. Those drainages containing few native fishes exhibited great variation in the number of invaders, while waters with a rich native fauna contained few introduced species. However, this pattern did not differ significantly from random simulations because the pool of potential invaders is greater for drainages with low species richness.3. In most drainages, there were more introduced than imperilled or extirpated species, suggesting that invaders tend to increase overall species richness.4. These patterns suggest that North American fish communities are not saturated with species, but instead, are capable of supporting higher levels of diversity if the pool of potential colonists and the rate of colonization from that pool is increased.

The Effects of Staring and Pew Invasion in Church Settings.

The agonistic effects of staring in human beings was tested in a field experiment. Confederates approached worshippers in six churches and attempted to "invade" the pew, with or without staring at the seated person at the end of the pew. The results of 98 invasions over 18 Sunday services revealed that invader staring increased the likelihood of a worshipper moving over or returning the gaze; the same worshippers rarely made both responses. Number of invaders did not influence moving or gaze return. The results are interpreted as yielding support and external validation for previous studies of the agonistic properties of the stare in Americans.