Alien Spiders Research Articles

Three new alien spider mites (Prostigmata, Tetranychidae) from south-eastern France

During this survey in southeastern France, there were found three new alien spider mites species: Aponychus corpuzae found on Phyllostachys sp. and Semiarundinaria yashadake; the Persea mite Oligonychus perseae found on Persea americana and most probably also on Vitis vinifera; Stigmaeopsis nanjingensis found on Phyllostachys sp. and S. yashadake. In connection with the new records of A. corpuzae, we propose an identification key for the world species of the genus Aponychus.

Three alien spider species (Araneae: Theridiidae) newly found in Poland

Global warming and intensive transport favor the spreading of species. In 2015, three theridiid spider species were found in Poland for the first time: Kochiura aulica, Latrodectus geometricus and Theridion melanostictum. Kochiura auilica was transported in pomegranates from Turkey and T. melanostictum in pomegranates from Chile. One female of Latrodectus geometricus hung, with three egg sacs, on a web in a car imported from the USA (2015), and also in grapes imported from Chile, Morocco and RPA (2017). Effect of non-native spider species in Poland is discussed.

Using Global and Regional Species Distribution Models (SDM) to Infer the Invasive Stage ofLatrodectus geometricus(Araneae: Theridiidae) in the Americas

The brown widow spider, Latrodectus geometricus C. L. Koch, 1841, is a large spider of the family Theridiidae that belongs to a genus of medical interest owing to its potent neurotoxic venom, which causes severe pain in humans. In America, this alien spider has been found in virtually all countries in the region, mainly associated with human dwellings, but also in agricultural sectors. However, the invasive process and potential distribution of this invasive species across the American continent are completely unknown. In this context, using a combination of both global and regional niche models, it is possible to hypothesize the invasive phase of the species as well as the geographic space where these different phases occur. By comparing the global and regional niches of L. geometricus, we examined its invasive process and potential distribution across the American continent. This work is an innovative approach to understanding the invasion of the brown widow spider in this area and the ecological processes that underlie this invasion. In this context, the global and regional niche comparison constitutes an appropriate tool to account for the complexities of the invasive process, generating different hypotheses amenable to being tested in future studies.

Retraction—Alien spiders in Chile: evaluating Darwin's naturalization hypothesis

Darwin's naturalization hypothesis (DNH) states that the successful establishment of alien species is favored when the phylogenetic relationship between the colonizer and the recipient community is distant. From a population perspective, the establishment involves both the progressive increase in size and spatial distribution of the invasive population. In this study, we focused our attention on the spatial component of establishment, assessing the role of phylogenetic relatedness as a determinant of its extension. Following DNH, it is expected that alien species closely related to the native spiders would show narrower distribution ranges than alien taxa less related to the native species. We found 18 alien spider species in Chile; all of these are synanthropic and most are of African origin. Our results indicate a difference in range size between related and unrelated species but it was not statistically significant. Consequently, the results do not support DNH as an explanation of the distributional component of establishment of alien spider species in Chile. We conclude that ecological constraints do not affect the process of invasion of spiders; therefore, it is only time that determines the spread of alien spiders in this country.

Retraction—Alien spiders in Chile: evaluating Darwin's naturalization hypothesis

Retraction—Alien spiders in Chile: evaluating Darwin's naturalization hypothesis

Introduction, establishment rate, pathways and impact of spiders alien to Europe

A comprehensive analysis of spiders reported as alien for Europe over the last 200 years has yielded information for 184 spider species, which had been introduced at least once. The most common spider families are Theridiidae (27 species), Pholcidae (15), Salticidae (14), Sparassidae (14), Ctenidae (14), and Theraphosidae (13) but overall establishment rate was only 28 %. No ctenids or theraphosids established, and only one sparassid species, but many theridiids and pholcids. Most introduced species originated from South (34 %), Central (10 %) or North (12 %), America, Asia (19 %) and Africa (15 %). Only few of the South and Central American species could establish, while species from North America (36 %) and Asia (63 %) had much higher establishment rates. Over the last 200 years, introduction and establishment rates have been strongly increasing. Three pathways are responsible for the majority of introductions: fruit shipments (67 % of all cases), potted plants (16 %) and containers or packaging material (12 %). In contrast to fruit shipments, spiders introduced on plants or with containers have high establishment rates (65 and 47 %). Environmental impact of alien spiders can be expected on both insects (through predation) and spiders (through predation and competition), potentially leading to change of species composition and guild structure. Socio-economic impact includes reduction of marketability of horticultural products through excessive spinning activity which also may cause increased cleaning costs at facades and windows. Impact on human health may be caused by bites and subsequent need for medical treatments. For all these impact categories, however, only anecdotal evidence is given for alien spiders in Europe. This may change when spiders of medical importance such as the frequently introduced Latrodectus species will establish. Considering the current trends it is concluded that introduction and establishment rates of alien spiders will strongly increase in the next years unless preventive methods become more efficient.

Alien spiders in Chile: evaluating Darwin's naturalization hypothesis

Darwin's naturalization hypothesis (DNH) states that the successful establishment of alien species is favored when the phylogenetic relationship between the colonizer and the recipient community is distant. From a population perspective, the establishment involves both the progressive increase in size and spatial distribution of the invasive population. In this study, we focused our attention on the spatial component of establishment, assessing the role of phylogenetic relatedness as a determinant of its extension. Following DNH, it is expected that alien species closely related to the native spiders would show narrower distribution ranges than alien taxa less related to the native species. We found 18 alien spider species in Chile; all of these are synanthropic and most are of African origin. Our results indicate a difference in range size between related and unrelated species but it was not statistically significant. Consequently, the results do not support DNH as an explanation of the distributional component of establishment of alien spider species in Chile. We conclude that ecological constraints do not affect the process of invasion of spiders; therefore, it is only time that determines the spread of alien spiders in this country.

Spiders (Araneae). Chapter 7.3

A total of 47 spider species are alien to Europe; this corresponds to 1.3 % of the native spider fauna. They belong to (in order of decreasing abundance) Theridiidae (10 species), Pholcidae (7 species), Sparassidae, Salticidae, Linyphiidae, Oonopidae (4-5 species each) and 11 further families. There is a remarkable increase of new records in the last years and the arrival of one new species for Europe per year has been predicted for the next decades. One third of alien spiders have an Asian origin, one fifth comes from North America and Africa each. 45 % of species may originate from temperate habitats and 55 % from tropical habitats. In the past banana or other fruit shipments were an important pathway of introduction; today potted plants and probably container shipments in general are more important. Most alien spiders established in and around human buildings, only few species established in natural sites. No environmental impact of alien species is known so far, but some alien species are theoretically dangerous to humans.

First records ofSpermophora kerinci,Nesticella mogeraandPseudanapis alohaon the European Mainland (Araneae: Pholcidae, Nesticidae, Anapidae)

The alien spider species Spermophora kerinci Huber, 2005, Nesticella mogera (Yaginuma, 1972) and Pseudanapis aloha Forster, 1959 are recorded from greenhouses in Germany. These are the first records from the European mainland. All these species have recently been found in the British Isles. The study of exotic spiders in greenhouses of the Botanic Garden in Berlin rendered interesting re- sults (KIELHORN 2008). Consequently, the spider fauna of other greenhouses in Berlin and Bran- denburg was examined. Spiders were collected in a hothouse of the Zoo-Aquarium Berlin (52°30'22N 13°20'29E, TK 3446, 37 m a.s.l.) and in the 'Tropical Islands' dome, a recreation facility with tropical plants in Brand, Brandenburg (52°2'20N 13°44'55E, TK 3948, 78 m a.s.l.). Several exotic spider species, which had been found in the Botanic Garden Berlin-Dahlem, were also present in the other greenhouses (KIELHORN 2009). Additionally, three species newly reported from the British Isles were caught: the pholcid Spermophora kerinci Huber, 2005, the nesticid Nesticella mogera (Yaginuma, 1972) and the anapid spider Pseudanapis aloha Forster, 1959. In Britain, these spiders were collected from leaf litter in the humid tropical greenhouse of the Eden project, a large greenhouse complex enclosing several artificial ecosystems (SNAZELL & SMITHERS 2007). Large tropical greenhouses, such as in the Eden project, have become popular attractions and have been built around the globe. It is nearly impossible to reconstruct the path by which exotic spider spe- cies may have reached these greenhouses (PAQUIN et al. 2008, SNAZELL & SMITHERS 2007). In the case presented here, a group of species has been imported to various countries in recent years. It is very likely that the institutions have acquired plants from the same common sources.

Aliens among us: nestmate recognition in the social huntsman spider, Delena cancerides

Unlike all other social spiders, the social huntsman spider, Delena cancerides, has been reported to rapidly respond to non-nestmates with lethal aggression, similar to the behavior of some eusocial insects. We tested for the presence of nestmate recognition in D. cancerides under laboratory conditions by introducing 105 unrelated alien conspecifics into foreign colonies and comparing their behavior to 60 control spiders removed and returned to their natal colony. Spiders demonstrated nestmate recognition by investigating alien spiders far more than nestmates and by resting closer to nestmates than to aliens. Serious attacks or deaths occurred in 23% of all trials; however, aggression was not directed significantly more toward aliens than to nestmates. Most notably, aggression was largely mediated by the adult females (resident or alien), who were most likely to attack or kill other subadult or mature individuals. Young individuals (resident or alien) were largely immune from serious aggression. Spiders recently collected from the field tended to be more aggressive than spiders born and raised in the laboratory, possibly due to blurring of recognition cues related to laboratory husbandry. Our findings support the prediction that nestmate recognition should evolve when there is a benefit to discriminating against non-kin, as in this social spider system where foraging individuals may enter a foreign colony and the colony retreat is a limited resource.

A glimpse of the tropics – spiders (Araneae) in the greenhouses of the Botanic Garden Berlin-Dahlem

In a survey of the spider fauna in greenhouses of the Botanic Garden Berlin-Dahlem, 30 spider spe- cies were recorded. Two species are new to Europe: Theotima minutissima (Petrunkevitch, 1929) and Heteroonops spinimanus (Simon, 1891). T. minutissima is the first member of the family Ochyroceratidae reported from Europe. Oecobius navus Blackwall, 1859 is new to Central Europe. Triaeris stenaspis Simon, 1891, is recorded from Germany for the first time. Zodarion italicum (Canestrini, 1868) is new to eastern Germany. Despite the discovery of some species previously unknown to Germany, the spider fauna in the Botanic Garden consisted mainly of well- known synanthropic species and common inhabitants of greenhouses. Several alien spiders recently found in greenhouses, garden centers and houses were not recorded in the Botanic Garden. The species composi- tion of the exotic spider fauna in greenhouses seems to depend chiefly on the specific modes of acquisition of plants and plant substrate. The spider fauna of botanic gardens and green- houses has attracted several researchers, starting with SIMON (1896) and followed by PICKARD- CAMBRIDGE (1906), VAN DER HAMMEN (1949a), HOLZAPFEL (1932) and others. BOETTGER (1929)

Alien spider introductions to Europe supported by global trade

ABSTRACTGlobal trade is permanently ongoing and increases its volume every year. In this study, the occurrence of 87 unintentionally introduced spider species alien to Europe is analysed. The analysis includes (1) the introduction potential of six different origin areas of the world according to trade volume, area size, and geographical distance; (2) the body size of native and alien species; and (3) occurrence in or at buildings (synanthropic) or in natural habitats. We found the eastern Palearctic as the most influencing origin area with 44 introduced spider species to Europe. The eastern Palearctic and the Indomalayan provided a significantly higher number of introductions than expected, whereas the Nearctic, Neotropical, and Afrotropical provided a significantly lower number of introduced species than expected. This can be explained with their lower trade volume, smaller area, larger geographical distance to Europe, and stronger climate differences to Europe. Comparing the body size of introduced and native European spider species of the same family, we found for Theridiidae significantly larger alien spiders and for all other tested families a trend to a larger body size of alien species compared to the native spiders. The family affiliation of alien spiders is the most important factor for synanthropic occurrence in Europe. On the base of a very conservative estimation of spider species introductions to Europe combined with possible effects of climate change, we predict for the near future a permanent increase in the number of alien spider species in Europe.

Impacts of biological control and invasive species on a non-target native Hawaiian insect

The potential for classical biological control to cause unintended harm to native species was evaluated in the case of the endemic Hawaiian koa bug, Coleotichus blackburniae White (Hemiptera: Scutelleridae), and parasitoids introduced to Hawaii for control of an agricultural pest, the southern green stink bug, Nezara viridula (L.) (Hemiptera: Pentatomidae). Parasitism of C. blackburniae eggs, nymphs and adults by biocontrol agents was quantified across a wide range of habitats and compared to other sources of mortality. Egg mortality due to the biocontrol agent Trissolcus basalis Wollaston (Hymenoptera: Scelionidae) was low (maximum 26%) and confined to elevations below 500 m on a single host plant. Predation, mainly by alien spiders and ants, was the greatest source of egg mortality (maximum 87%). Parasitism of adult C. blackburniae by the biocontrol agent Trichopoda pilipes (F.) (Diptera: Tachinidae) was near zero at 21 of 24 sites surveyed. Three sites with high bug density had higher levels of T. pilipes parasitism, reaching maxima of 70% among adult female bugs, 100% among males and 50% among fifth instars. Male-biased parasitism indicated that T. pilipes is adapted to using male aggregation pheromone for finding C. blackburniae hosts. The relative impacts of biocontrol agents and other sources of mortality were compared using life tables. Invasive species, particularly generalist egg predators, had the greatest impacts on C. blackburniae populations. Effects of intentionally introduced parasitoids were relatively minor, although the tachinid T. pilipes showed potential for large impacts at individual sites. In retrospect, non-target attacks by biological control agents on C. blackburniae were predictable, but the environmental range and magnitude of impacts would have been difficult to foresee.

Darwin's Naturalization Hypothesis Revisited

In The Origin of Species, Darwin (1859) drew attention to observations by Alphonse de Candolle (1855) that floras gain by naturalization far more species belonging to new genera than species belonging to native genera. Darwin (1859, p. 86) goes on to give a specific example: “In the last edition of Dr. Asa Gray’s ‘Manual of the Flora of the United States’ ... out of the 162 naturalised genera, no less than 100 genera are not there indigenous.” Darwin used these data to support his theory of intense competition between congeners, described only a few pages earlier: “As the species of the same genus usually have, though by no means invariably, much similarity in habits and constitution, and always in structure, the struggle will generally be more severe between them” (1859, p. 60). Darwin’s intriguing observations have recently attracted renewed interest, as comprehensive lists of naturalized plants have become available for various regions of the world. Two studies (Mack 1996; Rejmanek 1996, 1998) have concluded that naturalized floras provide some support for Darwin’s hypothesis, but only one of these studies used statistical tests. Analyses of additional floras are needed to test the generality of Darwin’s naturalization hypothesis. Mack (1996) tabulated data from six regional floras within the United States and noted that naturalized species more often belong to alien genera than native genera, with the curious exception of one region (New York). In addition to the possibility of strong competition between native and introduced congeners, Mack (1996) proposed that specialist native herbivores, or pathogens, may be