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opencc-zeroMay 2022View details →

Invasive brown widow spiders disperse aerially under a broad range of environmental conditions

Spiders commonly disperse on silk lines as juveniles by means of rappelling or ballooning. These modes of dispersal, especially long-distance dispersal via ballooning, can greatly increase the distance an individual can move, and at the population level, the speed of range expansion and likelihood of gene flow. Nevertheless, few studies have examined how spiders disperse under field conditions, and which environmental and meteorological conditions may affect their decision to disperse. We tested dispersal by spiderlings of the invasive brown widow (Latrodectus geometricus) under field conditions in the Negev Desert of Israel. We documented pre-dispersal (climbing and tiptoeing) and dispersal (short-distance dispersal by rappelling and long-distance dispersal by ballooning) behaviours during the day (n = 147 spiders) and night (n = 171 spiders), while recording wind speed, temperature, and humidity. We found that spiders ballooned significantly more during the day (14.3%) compared with 1.8% of spiders ballooning at night. At night, spiders were more likely to disperse in conditions of higher wind speeds, lower temperature, and higher humidity, whereas during the day, environmental factors were less predictive of dispersal behaviour. In addition, we found significant differences in the proportion of spiderlings showing pre-dispersal and dispersal behaviour depending on family line. In conjunction with human-mediated dispersal, ballooning and rappelling may be an important mechanism of range expansion in the brown widow spider. Understanding the environmental and genetic factors affecting dispersal may lead to better management of invasive species.

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Figure 2. Two adult male Maratus cristatus with light-brown setation. 1 in Five new peacock spiders from Western Australia (Araneae: Salticidae: Euophryini: Maratus Karsch 1878)

Figure 2. Two adult male Maratus cristatus with light-brown setation. 1, Anterior view of extended fan during courtship display. 2, Ventral view of opisthosoma during display showing retracted lateral tuft beneath each lobe of the fan. The white colular tuft is found in many Maratus species. 5, Display with lateral tufts of the fan fully extended. 8, The black cuticle of the carapace is almost fully exposed on the clypeus. Background scales in the eye region of the first male (♂ #1) are light brown and corresponding scales of the second male (♂ #3) are grey.

opencc-by-nd-4.0Aug 2017View details →

opencc-zeroApr 2023View details →

Data for: Invasive brown widow spiders avoid parasitism despite high densities

Invasive species are sometimes less susceptible to natural enemies compared to native species, but the mechanism is often unclear. Here we tested two potential mechanisms for lower parasitism of invasive species: density-dependent parasitism and preference for human-dominated habitats. We investigated how variation in host density and habitat type affect egg sac parasitism in two widow spider species (family Theridiidae). We compared parasitism on the egg sac of the brown widow, Latrodectus geometricus, an urban invasive species, and the white widow, L. pallidus, a species native to Israel. To investigate variation in host and parasitoid density, we measured nearest-neighbor distance between spider webs and parasitism rates in 16 sites, and in a single site monthly throughout a year. In L. pallidus, denser sites were more heavily parasitized (up to 55%) and parasitism rate increased with population density throughout the season. Extremely dense L. geometricus populations, however, had very low rates of parasitism (0-5%). We then conducted an egg sac transplant experiment in human-dominated and natural habitats. We found no parasitism of either species in the human-dominated habitat, compared to 30% parasitism of both species in the natural habitat. In addition, we found evidence for higher predation of L. pallidus than of L. geometricus egg sacs, particularly in the natural habitat. These combined results suggest that the human-dominated habitats inhabited by L. geometricus have a lower abundance of predators and parasites. We conclude that lower parasitism and predation in human-dominated habitats could contribute to the invasion success of L. geometricus.

publicMar 2025View details →

Data from: Maternal care thwarts parasitoids in the invasive brown widow spider (Latrodectus geometricus)

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publicApr 2023View details →

Data for: Invasive brown widow spiders avoid parasitism despite high densities

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Invasive brown widow spiders disperse aerially under a broad range of environmental conditions

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Dispersal and life history of brown widow spiders in dated invasive populations on two continents

Theory and empirical work suggest that behaviours such as dispersal and exploration are predictors of invasive success, and that behaviours may shift predictably after invasive populations have established and spread. However, there are limited data on temporal patterns in the distribution of behavioural traits linked to the timeline of establishment of invasive species. We examine dispersal and exploration, along with life history traits that may be linked to behaviour, across multiple invasive populations of the brown widow spider (Latrodectus geometricus). This global invader has established populations across the United States and Israel. Using this temporal and spatial variation, we tested predictions about changes in suites of traits over establishment time. We compared trait distributions of four U.S. populations of L. geometricus to patterns in four populations in Israel. We predicted that selective filters during the invasion process would result in more dispersive, more exploratory spiders that are larger and more fecund in recently established populations, but, if tradeoffs occur, dispersal would be favoured at the expense of fecundity and size in recent populations. We found more frequent and faster dispersal in more recently established populations in Israel, but not the United States. Spiders in more recently established populations in Israel were larger than those in older populations, but there were no consistent patterns across U.S. populations. However, there was evidence in both the U.S. and Israel for differing tradeoffs among fecundity, dispersal, and size. In more recently-established populations, spiders had lower fecundity than expected based on body size, but were more variable in resource allocation to egg sacs. The results suggest that in some populations, trade-offs underlying dispersal, fecundity, and body size are shaped by the time interval, and thus the number of generations, since establishment, with implications for the role of evolutionary processes in invasion success.

opencc-zeroDec 2021View details →

opennotspecifiedMar 2013View details →

On following pages 14 Brown-headed Spıder Monkey (Ateles fuscıceps) 15 Black Spider Monkey (Areias chamekl. 16 Red-faced Black Spıder Monkey (Areias paniscus) 17 Whne-wmskered Spodev Monkey (Areias margmatus) 18 Whıtebellıed Spıdeı Monkey (Areias belzeburh), 19 Vanegated Spıder Monkey (Areias hybndus) in Atelidae

On following pages 14 Brown-headed Spıder Monkey (Ateles fuscıceps) 15 Black Spider Monkey (Areias chamekl. 16 Red-faced Black Spıder Monkey (Areias paniscus) 17 Whne-wmskered Spodev Monkey (Areias margmatus) 18 Whıtebellıed Spıdeı Monkey (Areias belzeburh), 19 Vanegated Spıder Monkey (Areias hybndus)

Figure 6. Identity test between L. laeta and L in Ecological niche divergence between the brown recluse spiders Loxosceles laeta and L. surca (Sicariidae) in Chile

Figure 6. Identity test between L. laeta and L. surca in Chile. The expected niche area is significantly out of the observed niche between them.

Figure 4 in Ecological niche divergence between the brown recluse spiders Loxosceles laeta and L. surca (Sicariidae) in Chile

Figure 4. Environmental suitability map for Loxosceles surca and Loxosceles laeta under Maxent algorithm. Colours represent different ranges of probabilities of presence (high probability: 0.75– 1.0). (a) Potential distribution of Loxosceles surca. (b) Potential distribution of Loxosceles laeta.

Figure 5 in Ecological niche divergence between the brown recluse spiders Loxosceles laeta and L. surca (Sicariidae) in Chile

Figure 5. Precipitations and annual mean temperatures both Loxosceles laeta and Loxosceles surca records. (a) Histogram of the frequency of precipitation of warmest quarter period, constructed from the known distribution of both species. (b) Histogram of the frequency of annual mean temperature, constructed from the known distribution of both species.

Figure 1 in Ecological niche divergence between the brown recluse spiders Loxosceles laeta and L. surca (Sicariidae) in Chile

Figure 1. Location records for two species of Loxosceles showing the range overlap in northern of Chile; L. laeta (blue circles) and L. surca (red triangles).

Figure 2 in Ecological niche divergence between the brown recluse spiders Loxosceles laeta and L. surca (Sicariidae) in Chile

Figure 2. Loxosceles surca in northern of Chile. (a) Habitat where the spiders were found. (b) Live female specimen of the Loxosceles surca, Altos de Pica, Chile. (Photography: William H. Piel).

Figure 3 in Ecological niche divergence between the brown recluse spiders Loxosceles laeta and L. surca (Sicariidae) in Chile

Figure 3. Maximum likelihood phylogeny of an alignment of COI and 28S sequences from Loxosceles species. The digits by each clade indicate percent bootstrap support based on 1,000 replicates. The species groups, as delineated by Gertsch (1967), are indicated by boxes enclosing clades. Continental biogeographic history is estimated using common-sense inference based on contemporary species distributions and is indicated in the figure using branch colours.