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Wandering and web spiders feeding on the nectar from extrafloral nectaries in neotropical savanna
Abstract
Despite their essentially carnivorous habits, spiders can supplement their diets with other food sources, such as extrafloral nectar. The extrafloral nectar can constitute an excellent complementary energy source for spiders because it is rich in mono and disaccharides besides other compounds. We investigate the presence of fructose and its concentration in the bodies of wandering and web weaver spiders collected on extrafloral nectary-bearing plants from a neotropical savanna area by means of cold anthrone test. The tested spiders belonged to seven families: Anyphaenidae, Araneidae, Oxyopidae, Pisauridae, Salticidae, Theridiidae and Thomisidae. A total of 265 (88.04%) of all tested individuals were fructose intake positive. In general, there was no difference in the percentage of positive spiders between wandering and web weaver spider species or between adult and immature individuals. Results found in this study corroborate those from other studies that suggest that nectar feeding is a common activity among spiders and it includes a new family (Theridiidae) in the nectivory spiders list.
... These well-marked climatic conditions can generate temporal partitions for the occurrence of different species. For instance, spiders and ants are among the most common predator arthropods inhabiting vegetation in this region (Calixto et al., 2018;Del-Claro et al., 2017), which are frequently attracted by plant-provided resources such as extrafloral nectar (Calixto et al., 2018;Calixto et al., 2020;Del-Claro et al., 2017;Heil, 2015;Nahas et al., 2016;Taylor & Pfannenstiel, 2009). Extrafloral nectaries (EFNs) produce a sugar-rich resource which is also composed of amino acids and other contents, works as a source of nutrient to balance the carbohydrate-protein ratio in the diet of ants and spiders (Byk & Del-Claro, 2011;Calixto, Lange, Bronstein, et al., 2021;Lange et al., 2017;Nahas et al., 2016), and is mainly produced in the rainy season concomitantly to leaf flushing Lange et al., 2013). ...
... For instance, spiders and ants are among the most common predator arthropods inhabiting vegetation in this region (Calixto et al., 2018;Del-Claro et al., 2017), which are frequently attracted by plant-provided resources such as extrafloral nectar (Calixto et al., 2018;Calixto et al., 2020;Del-Claro et al., 2017;Heil, 2015;Nahas et al., 2016;Taylor & Pfannenstiel, 2009). Extrafloral nectaries (EFNs) produce a sugar-rich resource which is also composed of amino acids and other contents, works as a source of nutrient to balance the carbohydrate-protein ratio in the diet of ants and spiders (Byk & Del-Claro, 2011;Calixto, Lange, Bronstein, et al., 2021;Lange et al., 2017;Nahas et al., 2016), and is mainly produced in the rainy season concomitantly to leaf flushing Lange et al., 2013). ...
... For instance, ant larvae have a high demand for nitrogen for the production of nucleic acids and proteins, while adult workers have a higher demand for carbohydrates as source of energy (Blüthgen & Feldhaar, 2010). Similarly to ants, spider performance can also be affected by nutrient intake and, therefore, a suitable balance of macronutrients like proteins, lipids and carbohydrates is necessary (Chen et al., 2010;Nahas et al., 2016;Taylor & Bradley, 2009;Toft, 2013). Despite the high frequency of both groups (ants and spiders) in these EFN-bearing plants and the similarity of their feeding behaviours, which could lead to competitive relationships, there is no study involving temporal or spatial co-occurrence patterns between ants and spiders which forage on EFN-bearing plants. ...
1. Mechanisms promoting stable coexistence allow multiple species to persist in the same trophic level of a given network of species interactions. One of the most common stabilizing mechanisms of coexistence is niche differentiation, such as temporal and spatial patchiness. To understand the limits of coexistence between species we have to understand the limits of competitive interactions which translate in species exclusion or patterns of non-co-occurrence. 2. We evaluated spatiotemporal niche-based mechanisms that could promote stable coexistence between ants and spiders which forage on extrafloral nectary (EFN)-bearing plants. We observed co-occurrence and overlapping patterns between ants and spiders in a temporal and spatial scale in nine different EFN-bearing plant species in a Neotropical savanna, using both community-and species-level approach. 3. Ants and spiders showed asynchrony of their abundances over the year with low temporal overlapping patterns between them (temporal niche specialization). Greater abundance of ants occurred between September and March, whereas greater abundance of spiders occurred between March and August, exactly at the time when the abundance of ants decreases on plants. However, there might also be some levels of temporal overlapping, but then individual ants and spiders occupy different branches (spatial segregation). Finally, we also observed a spatial negative effect of the abundance of ants on the presence of spiders. Synthesis. Our results suggest that spatiotemporal partitioning between ants and spiders may be one of the potential mechanisms behind a stable coexistence between these two groups of organisms that forage on EFN-bearing plants in the Brazilian savanna.
... According to Bruinsma and Dicke (2008), induced indirect defences in plants depend on the natural enemies of herbivores, such as predators and parasitoids. Studies on indirect defence induction to promote greater extrafloral nectar production have mainly dealt with the herbivore action of ants (Kost & Heil 2006, 2008Radhika et al. 2008); however, besides ants, spiders are abundant herbivores in vegetation sites (Wise 1993;Nyffeler et al. 2016;Nahas et al. 2016). At least nine spider families are known to include nectar in their diet, including jumping spiders (Salticidae), crab spiders (Thomisidae), ghost spiders (Anyphaenidae), sac spiders (Miturgidae and Clubionidae) and some representatives of families Eutichuridae, Trachelidae and Therididae (Taylor & Foster 1996;Jackson et al. 2001;Taylor & Pfannenstiel 2009;Nyffeler et al. 2016;Nahas et al. 2016). ...
... Studies on indirect defence induction to promote greater extrafloral nectar production have mainly dealt with the herbivore action of ants (Kost & Heil 2006, 2008Radhika et al. 2008); however, besides ants, spiders are abundant herbivores in vegetation sites (Wise 1993;Nyffeler et al. 2016;Nahas et al. 2016). At least nine spider families are known to include nectar in their diet, including jumping spiders (Salticidae), crab spiders (Thomisidae), ghost spiders (Anyphaenidae), sac spiders (Miturgidae and Clubionidae) and some representatives of families Eutichuridae, Trachelidae and Therididae (Taylor & Foster 1996;Jackson et al. 2001;Taylor & Pfannenstiel 2009;Nyffeler et al. 2016;Nahas et al. 2016). Spiders can find extrafloral nectary when they forage on plants (Nahas et al. 2016), but we lack information about whether spiders can increase EFN encounters by being attracted to chemical tracks associated with nectar production or with herbivoreinduced volatiles produced by damaged plants. ...
... At least nine spider families are known to include nectar in their diet, including jumping spiders (Salticidae), crab spiders (Thomisidae), ghost spiders (Anyphaenidae), sac spiders (Miturgidae and Clubionidae) and some representatives of families Eutichuridae, Trachelidae and Therididae (Taylor & Foster 1996;Jackson et al. 2001;Taylor & Pfannenstiel 2009;Nyffeler et al. 2016;Nahas et al. 2016). Spiders can find extrafloral nectary when they forage on plants (Nahas et al. 2016), but we lack information about whether spiders can increase EFN encounters by being attracted to chemical tracks associated with nectar production or with herbivoreinduced volatiles produced by damaged plants. ...
Some plant species attacked by herbivore species produce additional resources to attract predators and induce an indirect defence process. We evaluated whether Palicourea rigida (Rubiaceae) individuals can induce indirect defences as response to herbivory simulation by increasing pericarpial nectar production and volatile emissions, as well as whether spiders are attracted by such induced indirect defences. We selected 30 P. rigida individuals and simulated herbivory in 15 of them by cutting out half of all leaves using pruning shears. We did not manipulate the other 15 plants (control group). At three different times, we measured nectar volume and calories of the pericarpial nectary in the inflorescences of all plants of control and treatment groups. We also quantified spider abundance on these plants. In another experiment, we selected salticid spider, Thiodina sp., to determine whether predators detect chemical tracks of plant volatiles produced by the plant after herbivory simulations. We also tested whether the honey solution could emit olfactory signals capable of attractive spiders. We showed that P. rigida produced higher volume of pericarpial nectar presenting more calories after herbivory simulation. The abundance of spiders was higher in plants subjected to herbivory simulation than control plants. Thiodina sp. did not respond to the volatile chemical tracks produced by the leaves after the simulation, but it had a positive response to olfactory tracks associated with the sucrose solution. Such an outcome indicates the ability of this spider to locate nectar honey plants and olfactory signals of honey. Thus, plants respond to the action of herbivores by producing more pericarpial nectar and nectar with more calories. Although our knowledge about the olfactory physiology of arachnids remains incipient, we highlight the importance of chemical and olfactory tracks for decision‐making of spiders in foraging on plants and the herbivory influence on the behaviour of cursorial spiders.
... Sometimes the costs of biotic defences are high, because resources are the plant's own tissues when consumed by herbivores (Price 2002), whereas at other times the benefits of biotic defences are high, and plants receive protection against herbivores from third-partner species, such as ants, spiders, and wasps . The most common resource that plants offer to attract and reward these predators is nectar (Nahas et al. 2016). ...
... After more than 100 years of studies that were initiated by Belt (1874), the majority of reviews explain that EFN is a valuable resource to ants (Byk and Del-Claro 2011), and that its production generally benefits plants through indirect reductions in herbivory (Oliveira and Freitas 2004;Rosumek et al. 2009;Zhang et al. 2015;Del-Claro et al. 2016). However, we now know that both spiders and wasps feed on EFN (Figs. 8.1 and 8.2) and are effective plant guards (Ruhren and Handel 1999;Cuautle and Rico-Gray 2003;Torezan-Silingardi 2011;Nahas et al. 2012Nahas et al. , 2016Alves-Silva et al. 2013;Stefani et al. 2015). The ecological system in different interacting trophic levels: plants-herbivores-predators. ...
... Using the cold anthrone test, Nahas et al. (2016) investigated the presence and concentration of fructose in the bodies of wandering (Anyphaenidae, Oxyopidae, Pisauridae, Salticidae, and Thomisidae) and orbweaving (Araneidae and Theridiidae) spiders that were collected from extrafloral nectary-bearing plants in a Neotropical savanna. The authors collected and tested adults and subadults of 301 spiders (39 species from seven families) for fructose ingestion, and found that 88.04% of the spiders tested positive. ...
In terrestrial communities, multitrophic interactions comprise a minimum of three trophic levels that interact among each other: plants, herbivores and their natural enemies. The top-down forces exerted by invertebrate predators on herbivores, and their cascading effect on plants, are very important to community structuring. Among major invertebrate predators, ants exert a strong impact on the density and spatial distribution of leaf and floral herbivores, which is reflected in the reproductive capacity of the plants. This important effect has only recently also been attributed to spiders. Studies of trophic interactions involving spiders and their impacts on the vegetation have increased considerably in the last few years. This is to be expected, considering that spiders are present in almost all terrestrial environments and occur in higher abundance in vegetation-rich areas. Regarded as excellent predators, spiders also use plants as foraging substrates, exploring differences in the plant architecture and in prey-capture strategies. Furthermore, spiders commonly prey on insect herbivores, which can result in a great decrease in herbivory rates, benefiting the host plants. In this chapter we will explore the hypothesis that spiders increase the reproductive value of plants with extrafloral nectaries, complementing the services provided by ants.
... Plants bearing extrafloral nectaries (EFNs) attract arthropods, especially ants, that can reduce herbivory leading to increased fruit production (Nahas et al., 2017;Rosumek et al., 2009;Trager et al., 2010). In turn, ants are benefited from a carbohydrate-rich liquid that intensifies ant colony healthy and survivorship, the extrafloral nectar (Byk & Del-Claro, 2011;. ...
... Additionally, multiple predators often have effects on their common prey populations that cannot be predicted by summing the effects of each predator at a time. Thus, ants, wasps, spiders and also parasitoids may complement protective services and benefit the plants in these systems mediated by EFN-bearing Malpighiaceae plants (Mendes-Silva et al., 2021;Nahas et al., 2017;Rosumek et al., 2009). ...
Extrafloral nectarized plants attract ants, which may protect them against herbivory and increase plant fruit set production. In some cases, however, ants are ineffective against herbivores. Such events occur, for instance, when herbivores present adaptations to avoid ant predation. Thus, the outputs of these interactions depend on factors such as ant identity, plant phenology and herbivore features. Here, we investigated the endophytic florivorous beetles' impact on the reproductive success of their host plants, two sympatric Banisteriopsis (Malpighiaceae) species, depending on the action of extrafloral nectaries (EFNs) visiting ants. We experimentally manipulated the presence of ants and herbivores on B. malifolia and B. laevifolia species during their reproductive period to test the effectiveness of ants‐EFNs mutualism on plant fruit set production. We performed treatments where three similar inflorescences were selected to be (I) control branch, with no manipulations, (II) beetle‐free branch, isolated with textile cover and (III) ant‐free branch, isolated at the base with atoxic wax. We hypothesized that endophytic herbivores have a negative impact on the plant reproductive success because they escape the action of ants (biotic defences). As a result, we observed (i) that florivorous Anthonomus beetles have a negative impact on Banisteriopsis reproductive success; (ii) ants fail in protecting plants against floral endophytic beetles; and (iii) most of the results were species‐specific. Our results indicate that these systems present very conditional outcomes that depend on the intrinsic factors of each plant species. Abbreviated abstract summarizing the article: We hypothesized that endophytic herbivores have a negative impact on the plant reproductive success because they escape the action of ants (biotic defences). Our study strongly suggests that multitrophic systems based on plant biotic defences, here ants EFNs bearing plants‐herbivores, present very conditional outcomes that depend on the intrinsic factors of interacting species.
... EFNs are variable in structure, morphology, and extrafloral nectar composition (Koptur 1994;Díaz-Castelazo et al. 2005;Machado et al. 2008;Lange et al. 2017), and due to this variability, they can attract a high diversity of ants and other arthropods. Some studies have shown a significant increase in spider (Nahas et al. 2016) and ant colony fitness (Byk and Del-Claro 2010; Calixto et al. 2021d) fed on extrafloral nectar. Therefore, it is expected that many other arthropods search for this nutritious reward (Koptur 2005;Nahas et al. 2012Nahas et al. , 2016Alves-Silva et al. 2013;Calixto et al. 2018b;Pearse et al. 2020;Moura et al. 2021). ...
... Some studies have shown a significant increase in spider (Nahas et al. 2016) and ant colony fitness (Byk and Del-Claro 2010; Calixto et al. 2021d) fed on extrafloral nectar. Therefore, it is expected that many other arthropods search for this nutritious reward (Koptur 2005;Nahas et al. 2012Nahas et al. , 2016Alves-Silva et al. 2013;Calixto et al. 2018b;Pearse et al. 2020;Moura et al. 2021). ...
This book unveils forestry science and its policy and management that connect past and present understanding of forests. The aggregated knowledge is presented to cover the approaches adopted in studying forest structure, its growth, functioning, and degradation, especially in the context of the surrounding environment. The application of advance computation, instrumentation, and modelling has been elaborated in various chapters.
Forest ecosystems are rapidly changing due to forest fires, deforestation, urbanization, climate change, and other natural and anthropogenic drivers. Understanding the dynamics of forest ecosystems requires contemporary methods and measures, utilizing modern tools and big data for developing effective conservation plans. The book also covers discussion on policies for sustainable forestry, agroforestry, environmental governance, socio-ecology, nature-based solutions, and management implication.
It is suitable for a wide range of readers working in the field of scientific forestry, policy making, and forest management. In addition, it is a useful material for postgraduate and research students of forestry sciences.
... EFNs are variable in structure, morphology, and extrafloral nectar composition (Koptur 1994;Díaz-Castelazo et al. 2005;Machado et al. 2008;Lange et al. 2017), and due to this variability, they can attract a high diversity of ants and other arthropods. Some studies have shown a significant increase in spider (Nahas et al. 2016) and ant colony fitness (Byk and Del-Claro 2010; Calixto et al. 2021d) fed on extrafloral nectar. Therefore, it is expected that many other arthropods search for this nutritious reward (Koptur 2005;Nahas et al. 2012Nahas et al. , 2016Alves-Silva et al. 2013;Calixto et al. 2018b;Pearse et al. 2020;Moura et al. 2021). ...
... Some studies have shown a significant increase in spider (Nahas et al. 2016) and ant colony fitness (Byk and Del-Claro 2010; Calixto et al. 2021d) fed on extrafloral nectar. Therefore, it is expected that many other arthropods search for this nutritious reward (Koptur 2005;Nahas et al. 2012Nahas et al. , 2016Alves-Silva et al. 2013;Calixto et al. 2018b;Pearse et al. 2020;Moura et al. 2021). ...
Urbanisation has emerged as a major driver of ecosystem changes with mixed outcomes on the sustainability of production and protected landscapes in peripheries of cities. Urban demand for land, water and other resources significantly impacts peri-urban protected forests, a vital green infrastructure catering to multiple ecosystem services needs of cities. We assessed the ramifications of urban growth on social-ecological interactions around peri-urban protected areas (PAs) located in two megacities of India, using literature review and analysis of media content. Our analysis indicates that urban development creates negative impacts on the selected PAs in terms of land-use changes and the complexity of governance. Provisioning ecosystem service uses from PAs were found declining, while cultural service uses and ecosystem disservices were found prominent in both cases. Analysis of media coverage showed a greater frequency of themes such as infrastructure development projects, mining etc. indicating substantial media attention on the threats to urban PAs. The chapter further discusses the implications of urbanisation for forest conservation and ecosystem-dependent livelihoods in peri-urban spaces and suggests ways to integrate protected forests in the urban fabric.KeywordsUrbanisationLivelihoodsEcosystem servicesLand useGovernanceHuman-wildlife conflict
... EFNs are variable in structure, morphology, and extrafloral nectar composition (Koptur 1994;Díaz-Castelazo et al. 2005;Machado et al. 2008;Lange et al. 2017), and due to this variability, they can attract a high diversity of ants and other arthropods. Some studies have shown a significant increase in spider (Nahas et al. 2016) and ant colony fitness (Byk and Del-Claro 2010;Calixto et al. 2021d) fed on extrafloral nectar. Therefore, it is expected that many other arthropods search for this nutritious reward (Koptur 2005;Nahas et al. 2012Nahas et al. , 2016Alves-Silva et al. 2013;Calixto et al. 2018b;Pearse et al. 2020;Moura et al. 2021). ...
... Some studies have shown a significant increase in spider (Nahas et al. 2016) and ant colony fitness (Byk and Del-Claro 2010;Calixto et al. 2021d) fed on extrafloral nectar. Therefore, it is expected that many other arthropods search for this nutritious reward (Koptur 2005;Nahas et al. 2012Nahas et al. , 2016Alves-Silva et al. 2013;Calixto et al. 2018b;Pearse et al. 2020;Moura et al. 2021). ...
Evolutionary ecological studies have postulated that interactions between species are critical drivers of species diversification, in which each type of interaction promotes diversification in different ways. For instance, studies have suggested that antagonistic associations, such as plant–herbivorous insect interactions, can be paramount for the diversification process via coevolution between offensive and defensive traits that mediate interactions. In turn, plant–herbivore interactions, and the resulting diversification of traits, are therefore important determinants of community structure and dynamics. Here, we provide a general overview of how plant–herbivorous insect associations can be important for promoting diversity and maintaining ecosystem dynamics and structure. To this end, we start the chapter by presenting an overview of plant–herbivorous insect interactions, with a background of how evolutionary ecological studies about ecological interactions are important to understand the processes that drive species diversity. Then, we discuss the coevolutionary process between plants and insects by describing how plant–herbivorous insect coevolution can promote species diversity and shape ecosystems, and the potential mechanisms by which plants and herbivores might influence the ecosystem structure and biodiversity, which can act as a proxy for conservation measures. Next, we discuss the role of insect herbivory in shaping forest restoration outcomes, and how plant-provided resources mediating the protective mutualism can act as a biodiversity enhancer. Finally, we end the chapter by suggesting some novel and underrepresented perspectives within the topic, supporting researchers and policymakers to focus their efforts on certain measures to successfully maintain and protect biodiversity in different ecosystems.KeywordsHerbivoreAntagonismJanzen–Connell hypothesisDensity dependenceEcosystem engineeringBiodiversityCoevolutionForest restoration
... EFNs are variable in structure, morphology, and extrafloral nectar composition (Koptur 1994;Díaz-Castelazo et al. 2005;Machado et al. 2008;Lange et al. 2017), and due to this variability, they can attract a high diversity of ants and other arthropods. Some studies have shown a significant increase in spider (Nahas et al. 2016) and ant colony fitness (Byk and Del-Claro 2010; Calixto et al. 2021d) fed on extrafloral nectar. Therefore, it is expected that many other arthropods search for this nutritious reward (Koptur 2005;Nahas et al. 2012Nahas et al. , 2016Alves-Silva et al. 2013;Calixto et al. 2018b;Pearse et al. 2020;Moura et al. 2021). ...
... Some studies have shown a significant increase in spider (Nahas et al. 2016) and ant colony fitness (Byk and Del-Claro 2010; Calixto et al. 2021d) fed on extrafloral nectar. Therefore, it is expected that many other arthropods search for this nutritious reward (Koptur 2005;Nahas et al. 2012Nahas et al. , 2016Alves-Silva et al. 2013;Calixto et al. 2018b;Pearse et al. 2020;Moura et al. 2021). ...
Peatland is one of the important ecosystems in Indonesia, which covers about 14.9 Mha area. It has significant roles in carbon storage, water regulation, and biodiversity habitat. However, peatland has been degraded fast owing to overexploitation and massive canals development, which cause water drainage, subsidence, and carbon emission. Peatland restoration has become an important agenda in Indonesia to reduce fire risk and, at the same time, improve the resiliency of farmers by improving their livelihood. Sustainable peatland management systems have been applied by communities in the peatland landscape of Sebangau river and Kahayan river in Central Kalimantan, Indonesia. We identified tree-based agroforestry types been practiced in the peatland landscape of Central Kalimantan, such as jelutong tree-based agroforestry, agrosilvopastoral, agrosilvofishery, and apiculture system. All those agroforestry systems provide alternative livelihoods for farmers and improve peatland productivity. This chapter provides the performance of tree-based agroforestry types in Central Kalimantan. A patchy peat-swamp forest that still exists in the landscape provides habitats for natural vegetations and animals, which play important roles as pollinator and seed dispersal agents. Also, the existing forest provides sources for non-timber forest products.KeywordsAmeliorantAgrosilvofisheryAgrosilvopastoralPeat water levelPeat Hydrological Unit
... The antmimicking spiders may need to compete for food resources with the model ants, because ants and spiders are often assumed to be general predators and there are antagonistic interactions between the two arthropod groups (Sanders & Platner 2007;Katayama et al. 2015). Meanwhile, earlier studies have suggested that plant-based diets, such as floral nectar, extrafloral nectar and honeydew produced by hemipterans, are an important nutrient source for many spider species, including ant-mimicking spiders (Taylor & Foster 1996;Jackson et al. 2001;Jackson et al. 2008;Nahas et al. 2017). However, it is difficult to estimate the amount of nectar and other carbohydrate food sources assimilated by ant-mimicking spiders under field conditions. ...
... The importance of a plant-based diet is being increasingly recognized not only in ant-mimicking spiders but also in non-ant-mimicking spiders (Jackson et al. 2001;Nahas et al. 2017). Nyffeler et al. (2016) reviewed previous studies on plant feeding by spiders and found that more than 60 spider species belonging to 10 families have been observed to feed on plantbased diets under field conditions. ...
Ant‐mimicking spiders are a well‐known example of Batesian mimicry. Earlier studies have proposed that plant‐based diets (e.g. extrafloral nectar) are an important food source for ant‐mimicking spiders. However, it is still unclear whether the plant‐based diets are a main food source or supplementary energy source to the spiders. To examine the feeding habits, we measured stable nitrogen and carbon isotope ratios (δ¹⁵N and δ¹³C) of ant‐mimicking spiders (six species of Myrmarachne; one species of Agorius, Salticidae; and two species of Corinnidae) collected from a tropical rain forest in Malaysia and a dry evergreen forest in Thailand. We also investigated the isotopic signatures of several ant species sampled from the two forests for comparison. In general, the ant‐mimicking spiders had relatively low δ¹⁵N values, which were comparable to those of the nectar‐feeding and omnivorous ants. The δ¹⁵N values of the ant‐mimicking spiders differed significantly among the species: some species (e.g. Myrmarachne sp. H and Myrmarachne sp. 2) showed δ¹⁵N values similar to those of the nectar‐feeding ants, whereas the δ¹⁵N values of others (e.g. Myrmarachne maxillosa and Myrmarachne malayana) were close to those of the omnivorous ants. The δ¹³C values of the ant‐mimicking spiders did not differ significantly among the species, but tended to be similar to those of the nectar‐ and honeydew‐feeding ants rather than the predatory ants. These results indicate that plant‐based diets are important for the nutrition of ant‐mimicking spiders and suggest that the importance would differ among the ant‐mimicking spider species.
... Besides insects, spiders may spend time on flowers benefiting from food sources other than prey. Spiders can feed on stigma exudates, nectar, and pollen [63][64][65][66][67][68]. While we did not witness this behavior directly, we often saw individual spiders sitting on the corolla, with their mouthparts very close to the stigma, anthers, or postfloral nectaries. ...
Plants whose flowers open at night but remain open during the day also attract diurnal flower visitors, potentially boosting their pollination rates and providing resources that can support diverse arthropod communities. The rough-leaf velvetseed, Guettarda scabra (Rubiaceae), is an evergreen shrub that thrives only in the imperiled pine rockland habitat in south Florida. Its white, tubular, and fragrant flowers open during late afternoon, exhibiting traits strongly associated with the attraction of nocturnal hawkmoths (Sphingidae). Flowers of G. scabra remain open until the following morning, becoming available to a wider array of visitors, bringing into question the expectation that sphingophilous flowers are visited mainly by hawkmoths. To evaluate whether the flowers of G. scabra are mainly visited by nocturnal hawkmoths and understand the role of this plant in the pine rockland habitat, we characterized the arthropod fauna associated with its flowers during the morning, evening, and at night. We found that most flower visitors were diurnal insects of the orders Hymenoptera and Lepidoptera, although we observed other arthropod groups too. Visitation at night was dominated by two species of hawkmoths. Nectar was the main resource used by the arthropod community during this study. Legitimate visitation and nectar-robbing were the behaviors most frequently observed among the flower visitors. Our results suggest that flowers of the night-blooming G. scabra constitute an important food source for both diurnal and nocturnal arthropod fauna in the fire-dependent pine rocklands of southern Florida. Our study provides novel data to support efforts to conserve and protect pine rocklands and the plants and animals that inhabit them.
... When spiders are in vicinities of nectaries, they have a choice to feed directly on nectar or the nectarivorous insects [3]. Under such conditions, EFNs act as an excellent complementary energy source since it is rich in mono-and disaccharides besides other compounds [17]. Spiders in the present study spend more time on abaxial leaf surfaces before sucking nectar and do not predate ants. ...
Several plant species are known to differentiate extrafloral nectaries (EFNs) many of which secrete nectar that encourages numerous visitors to forage plants. Feeding at more than one trophic level is a common theme among various predatory insects. Particularly serving as a way to protect the plant from herbivory, nectivory is, however, not a widely appreciated feature of spiders. Here, we present one such observation in Urena lobata (Malvaceae). The plants are visited by five different members of Araneae owing to the presence of EFNs on leaves. Initially the spiders were envisaged as a predator of ants lured by nectar from EFNs. However, critical observations reveal that spiders prefer nectar to ants. Details on behaviour of spiders, time, and frequency of their visitation were generated and furnished. Our findings suggest that nectar feeding by arthropod predators may have beneficial interaction with U. lobata.
... Therefore, there are some limitations on this approach, including the limited availability of natural non-prey foods for spiders (e.g., pollen and nectar) (Vogelei and Greissl 1989;Taylor and Bradley 2009;Nyffeler et al. 2016). In addition, there are a few spiders species known to consume these non-prey foods, which contain a limited macronutrients, especially carbohydrates (Taylor and Pfannenstiel 2008;Wilder 2011;Nahas et al. 2017). The second approach requires the manipulation of the quantity or ratio of macronutrients present in a single species of prey (Mayntz and Toft 2001;Hawley et al. 2014;Wen et al. 2020). ...
As predators, the macronutrients spiders extract from their prey play important roles in their mating and reproduction. Previous studies of macronutrients on spider mating and reproduction focus on protein, the potential impact of prey lipid content on spider mating and reproduction remains largely unexplored. Here we tested the influence of prey varying in lipid content on female mating, sexual cannibalism, reproduction and offspring fitness in the wolf spider Pardosa pseudoannulata. We acquired two groups of fruit fly Drosophila melanogaster that differed significantly in lipid but not protein content by supplementing cultural media with a high or low dose of sucrose on which the fruit flies were reared (HL: high lipid; LL: low lipid). Subadult (i.e., one molt before adult) female spiders that fed HL flies matured with significantly higher lipid content than those fed LL flies. We found that the mated females fed with HL flies significantly shortened pre-oviposition time and resulted in a significantly higher fecundity. However, there was no significant difference in female spiders varying in lipid content on other behaviors and traits, including the latency to courtship, courtship duration, mating, copulation duration, sexual cannibalism, offspring body size and survival. Hence, our results suggest that the lipid content of prey may be a limiting factor for female reproduction, but not for other behavioral traits in the wolf spiders P. pseudoannulata.
... Many plant species also recruit natural enemies by providing an attractive food source in the form of extrafloral (EF) nectar. EF nectar, which is typically rich in sucrose, glucose, and fructose, encourages ants, parasitoids, and other predatory arthropods such as spiders [3,4] to forage for carbohydrates on the plant (reviewed in [5]). This improves the chance of an encounter between the natural enemies and herbivores such as caterpillars that may be damaging the plant. ...
Cultivated cotton, such as Gossypium hirsutum L., produces extrafloral (EF) nectar on leaves (foliar) and reproductive structures (bracteal) as an indirect anti-herbivore defense. In exchange for this carbohydrate-rich substance, predatory insects such as ants protect the plant against herbivorous insects. Some EF nectar-bearing plants respond to herbivory by increasing EF nectar production. For instance, herbivore-free G . hirsutum produces more bracteal than foliar EF nectar, but increases its foliar EF nectar production in response to herbivory. This study is the first to test for systemically induced changes to the carbohydrate composition of bracteal EF nectar in response to foliar herbivory on G . hirsutum . We found that foliar herbivory significantly increased the sucrose content of bracteal EF nectar while glucose and fructose remained unchanged. Sucrose content is known to influence ant foraging behavior and previous studies of an herbivore-induced increase to EF nectar caloric content found that it led to increased ant activity on the plant. As a follow-up to our finding, ant recruitment to mock EF nectar solutions that varied in sucrose content was tested in the field. The ants did not exhibit any preference for either solution, potentially because sucrose is a minor carbohydrate component in G . hirsutum EF nectar: total sugar content was not significantly affected by the increase in sucrose. Nonetheless, our findings raise new questions about cotton’s inducible EF nectar responses to herbivory. Further research is needed to determine whether an herbivore-induced increase in sucrose content is typical of Gossypium spp ., and whether it constitutes a corollary of systemic sucrose induction, or a potentially adaptive mechanism which enhances ant attraction to the plant
... Although the interactions between EFN-bearing plants and ants are relatively well-studied, interactions involving other species of nectar-consuming animals (Heil 2015) such as wasps (Cuautle and Rico-Gray 2003), beetles (Agarwal and Rastogi 2010), flies (Agarwal and Rastogi 2010), bees (Thorp and Sugden 1990), neuropterans (Limburg and Rosenheim 2001), and spiders (Taylor and Foster 1996;Nahas et al. 2017) are underexplored. The latter is particularly surprising, considering that spiders are among the most common arthropods inhabiting vegetation (Wise 1993; Foelix 2011) and have been observed feeding upon EFNs (Ruhren and Handel 1999;Cross and Jackson 2009;Nahas et al. 2017, . ...
Biotic defenses, often called indirect defenses, are relationships in which one organism attracts predators of its own enemies. A classic example of biotic defense is the ant-plant mutualism in which ants protect EFN-bearing plants from herbivores, but other interspecific interactions also qualify as biotic defense, including spider-plant, ant-aphid, and ant-butterfly defense relationships. Animal-animal relationships can also be a form of biotic defense, although host plants can still indirectly benefit from the defense in some cases. Overall, the costs and benefits to the organisms involved in biotic defense depend upon multiple factors, and the overall outcomes and implications for the stability of the relationship will thus also vary. Further consideration of this variation will lead to a deeper understanding of the evolutionary pressures behind these relationships and their contributions to the maintenance of biodiversity, and will also help us predict how they will change in the future.
... The secretory activity of those glands provides adequate conditions for leaf primordia and young leaves to develop and perform their metabolic processes under more appropriate conditions in terms of hydration and protection against herbivory and parasitism (Fahn, 1988;Morris et al., 2005;Drennan, Goldsworthy & Buswell, 2009;Singh, 2014;Tresmondi et al., 2015;Silva et al., 2017). In the case of hydathodes and EFNs, their secretory activity usually persists throughout the entire life cycle of the leaf, with the glands being associated with water flow and with mediating interactions between the plant and other organisms, respectively (Burgess & Dawson, 2004;Koulman et al., 2007;Shepherd & Wagner, 2007;Gish, Mescher & Moraes, 2015;Nahas, Gonzaga & Del-Claro, 2017). Thus, these glands play important biological roles according to leaf development stage. ...
Leaf teeth are projections on the leaf blade margin. They are structurally variable, with characters that are important for taxonomy and phylogeny, but there is a paucity of information on the anatomy of these structures and little understanding of the features and their functions. Here we describe and compare the leaf tooth anatomy of 47 eudicot species. Toothed margin samples from leaves at different developmental stages were collected, fixed and studied under light and scanning electron microscopy. We identified eight leaf tooth morphotypes, six of which occurred with glands. Hydathodes were the most common glands, being found in 11 species; colleters were found in ten species and extrafloral nectaries were found in two species. Cunonioid teeth either devoid of glands or associated with hydathodes were found in Lamiales, Asterales and Apiales. Dillenioid teeth associated with hydathodes were found in Dilleniales. Spinose teeth associated with colleters were found in Aquifoliales. In rosids, we found begonioid, malvoid, theoid, urticoid and violoid teeth, which may be associated with either colleters or nectaries or lack an associated gland. For each family studied, there was only one type of association between gland and tooth, demonstrating the systematic potential of these glands in eudicots.
... Plants generally support a wide range of spider species and abundant number of individuals (Foelix 2011), and they benefit spiders by providing substrates for web building and hunting (Wise 1993), suitable microclimates (Whitney 2004), and foodstuffs such as pollen and plant fluids as extrafloral nectary (Vogelei & Greissl 1989;Nahas et al. 2016;Nyffeler 2016), and by attracting prey (Schmalhofer 2001). Plantspider interactions can have both positive and negative effects on plants; for example, spiders may consume or deter herbivorous prey via signs of its presence (e.g., silk draglines and feces), which would increase plant fitness (Hlivkro & Rypstra 2003;Romero & Vasconcellos-Neto 2007a, 2011Bucher et al. 2015). ...
Spiders are diverse and abundant predators on vegetation in all terrestrial ecosystems, but only a few studies have examined their role in modulating spider–herbivore interactions throughout the year. We tested the hypothesis that spiders may reduce herbivore abundance on vegetation, resulting in lower leaf area loss and increased fitness (seed set production) of plants studied. In the tropics, this relationship will continue throughout the year. Our study was conducted in a cerrado environment in Brazil, using a shrub with glandular trichomes, Chamaecrista neesiana (Leguminosae Caesalpinioideae). We recorded phenological information, as well as the herbivorous insects and spiders present, on two groups of plants: a control group in which spiders were present and an experimental group in which spiders were removed. The results indicated that spiders had a positive indirect effect on plants by reducing leaf area loss and increasing seed set production, confirming our hypothesis. The benefits were higher in the rainy season, coinciding with the peak abundance of the spider species Peucetia flava. Our results indicate that protection against herbivory by spiders in the tropical savanna is conditional on the abundance of predators over time.
... EFNs have been hypothesised to act as plant defences against herbivores via mutualistic interactions with nectar-feeding arthropods (ants, non-ant predators, parasitoids). The protection through various arthropod taxa has been amply demonstrated by studies with ants (Costa et al. 1992;Rudgers 2002;Rico-Gray and Oliveira 2007), parasitoids (Hespenheide 1985;Mathews et al. 2007), several predators such as Araneae (Ruhren and Handel 1999;Nahas et al. 2017) and ladybird beetles (Pemberton and Vandenberg 1993). This is in concordance with our observation that particularly many Carabidae were associated to both L. hebantha and M. subarachnophylla. ...
Nectaries are structures that secrete a sugary solution and can occur on vegetative and/or reproductive parts of plants. The significance of floral nectaries to reward vertebrate and arthropod pollinators is well supported. The role of extrafloral nectaries (EFNs) is more ambiguous, though research has been skewed to the ant-plant mutualism. Many other insects feed at EFNs, but these interactions are vastly understudied. This study addresses the hypothesis that EFNs may influence the occurrence and structure of Neotropical canopy beetle communities. Seven canopy trees (four families) exhibiting EFNs and their associated beetles were studied over a one-year period in southern Venezuela. In total, 6818 adult beetles identified to 868 species were recorded on 25 investigated canopy tree species (#47 individuals). Of the 868 beetle species, 150 species (517 individuals; 17.3% species) from 20 families were observed drinking from foliar EFNs on seven EFN-bearing tree species. Dietary dependence on EF nectar varied, with 95 beetle species utilising this nectar within a broader diet and 55 species found feeding exclusively on EFNs. This study demonstrates unequivocally that EF nectar is a frequently utilised food resource of many beetle adults and beetles have been a significantly underestimated visitor group. A more detailed study was conducted on six individual canopy trees of two species of Chrysobalanaceae, Licania hebantha Mart. ex Hook. f. and Moquilea subarachnophylla (Cuatrec.) Sothers and Prance. In total, 115 individual adults of 64 beetle species were collected on nectar secreted on newly-sprouted leaves. These beetle assemblages were dominated by species utilising EF nectar and were associated with distinct phenological phases of the host trees. Altogether, the beetle survey found support for the hypothesis that EFNs influence the occurrence and structure of beetle communities. These beetle-EFN relationships have implications for spatial arrangement, community assembly and evolution of both host plants and beetles. Like ant-EFN mutualism, EFN-bearing trees and beetles may also form mutualism. It is possible that the plants offer easier access to a nutritious resource that may deflect herbivory of vegetative parts.
... For example, physical features, such as the size and height of the pitcher, have been shown to affect the rate of spider residency near S. purpurea (Cresswell 1993), but the presence of nectar or pigment does not (Milne and Waller 2013). In addition, it has been shown that some spiders readily drink nectar that is similar in composition to S. purpurea nectar (Cipollini et al. 1994, Pollard et al. 1995, Deppe et al. 2000, Amalin et al. 2001, Jackson et al. 2001, Taylor 2004, Nahas et al. 2016. Spiders have also been observed to use S. purpurea pitchers (Jones 1935, Milne 2012) and seed heads (Jennings et al. 2008) as oviposition sites. ...
The purple pitcher plant, Sarracenia purpurea, is a low‐lying carnivorous plant that uses pitcher‐shaped leaves to catch arthropod prey for nutrition. Spiders make up a significant portion of these prey. To determine the tendency of specific spider taxa to be captured by the plant, we compared the composition (by taxonomic family) of three spider assemblages: those captured by the plant, those residing on or over the plant, and those found nearby in the local environment. Although there were some broad similarities within the three spider assemblages, significant differences existed when specific families and guilds were considered. While some families (e.g., Linyphiidae and Lycosidae) and guilds (e.g., low sheet/tangle weavers) were heavily represented in all three assemblages, other groups varied, and we found that the taxonomic makeup of victimized and resident spiders did not always reflect their environmental abundances. Moreover, spider assemblages captured by S. purpurea were extremely similar across distant locations regardless of environmental spider assemblage composition, suggesting that S. purpurea is very selective in its spider capture regimen.
... It is known that extrafloral nectar positively interferes with the survival, body size of individuals and egg numbers of ant colonies (Byk & Del-Claro, 2011) and attracts a great diversity of insects and other arthropods, like spiders (Stefani et al., 2015;Nahas et al., 2016) and wasps (Koptur et al., 2015). According to Koptur (1992), insects from 10 orders have already been reported feeding on nectar or visiting EFNs (see also Almeida et al., 2011). ...
Solitary aculeate wasps represent the family Mutillidae (Hymenoptera) with high sexual dimorphism. The adult females are wingless and usually immature parasitoids of other insects and males are most often winged and generally feed on nectar. There are few records in the literature of adults of Mutillidae wasps feeding on extrafloral nectaries (EFNs) and still less in Brazil. Here, we report six fortuitous observations of mutillid wasps feeding on extrafloral nectar and their behavior in different plants in a reserve of cerrado stricto sensu, in Uberlândia, Brazil. We observed six species of mutillid wasps: Traumatomutilla sp. and T. latevittata (Cresson, 1902) feeding on EFNs of Stryphnodendron polyphyllum (Mart.), Hoplocrates sp. feeding on the EFNs of Eriotheca gracilipes (K. Schum.), Timulla sp. feeding on the EFNs of Banisteriopsis malifolia (Nees & Mart.), Hoplomutilla sp. feeding on the EFNs of Qualea grandiflora (Mart.) and an unidentified male species in Q. multiflora (Mart.). All mutillid wasps showed similar behavior on the plants. They quickly climbed on to the plant and foraged over with frequent movements of the antennas until they found the EFNs. We suggest that it is not a fortuitous observation, neither rare. We are just not looking with the needed attention to EFNs.
Insect-plant interactions are among the oldest, most diverse and complex biotic
relationships, ranging from antagonisms (e.g., herbivory) to mutualisms (e.g., protection
mutualism). Regarding the herbivory, we know that both bottom-up and top-down
forces affect the occurrence of insect herbivores and the structure of terrestrial
communities. However, it is not well understood how these selective forces change
among herbivore guilds and environments, especially in tropical areas such as the
Cerrado. In addition to being one of the most threatened biomes on the planet due to its
rapid transformation into pasture and/or cash-crop agriculture, large Cerrado's botanical
families such as Fabaceae has few information in relation to their interactions with
insects. Thus, the general aims of this thesis were to: (1) characterize the community of
arthropods, insect herbivores and their natural enemies, associated with the Fabaceae
species commonly found in the Cerrado: Andira humilis, Bauhinia rufa, Chamaecrista
cathartica, Mimosa setosa var. paludosa, and Stryphnodendron polyphyllum; and (2)
evaluate the effects of bottom-up (plant traits) and top-down (spiders, ants and wasps)
forces on the occurrence of insect herbivores. This thesis was divided in five chapters.
In the Chapter 1, we described the insect herbivores, natural enemies, Fabaceae-
herbivore network and community metrics such as Shannon-diversity index,
specialization, modularity and robustness. We found 1623 insect herbivores belonging
to five orders, 23 families and 87 species. Their main natural enemies were species of
ants (n= 11), spiders (n= 01), hemipterans (n= 01), and parasitoid wasps (n= 03). The
Fabaceae-herbivore network was modular, with only six species of insects feeding on
more than one host plant species. In the Chapter 2, we chose the two most abundant
insect herbivores as models, Acanthoscelides winderi and A. quadridentatus, and found
that these beetles were responsible for the predation of about 15% of seeds produced by
M. setosa var. paludosa. The attacked seeds did not germinate, and even the healthy
seeds from infested fruits had worse germination rate than healthy seeds from non-
infested fruits, suggesting a decrease in resource allocation by plants in attacked
structures. Acanthoscelides winderi and A. quadridentatus were synchronized with the
fruiting, but with a temporal partitioning in their occurrence, suggesting the avoidance
of competition in order to maintain their coexistence. In the Chapter 3, we found that
seed traits such as size, weight, hardness, and water content varied in a spatial (~240
km, four populations of M. setosa var. paludosa from Minas Gerais to Goiás) and
temporal (fruiting period) scale, affecting the occurrence of these beetles. The body
weight of A. quadridentatus was positively correlated with seed weight, length and
water content. Larger and heavier seeds were most protected (hardness), but individuals
of A. quadridentatus that had overcome seed hardness obtained larger sizes, being
males and females 15 and 25% larger, respectively. In the Chapter 5, we showed that
one of the main natural enemies found, Peucetia flava, decreased 3.3-fold the damage
inflicted by insect herbivores on leaves of M. setosa var. paludosa. In addition, this
spider also fed on insect carrion provided by the plant's glandular trichomes, which
suggests a facultative mutualism. If on the one hand the spider was effective in
protecting the plant against exophytic leaf herbivores, on the other hand it was unable to
protect the plant against endophytic seed herbivores (e.g., A. winderi) since these beetles were able to defend themselves against the spider by hiding vulnerable body parts under
their elytra. Consequently, the presence of spiders did not reduce the proportion of seeds
taken by those beetles. Finally, we found a new species of parasitoid wasp in this
system. Thus in the Chapter 5 we described Cotesia itororensis and notes on its impact
on the host, Oospila pallidaria. The results of this thesis highlighted that the most
abundant species of insect herbivores presented a pattern of high specificity and
phenological synchronicity with their host plants. Both plant traits and natural enemies
affected the results of interactions, the former changing traits of herbivores' life history
(e.g., size) and the latter decreasing their occurrence. We suggest conditionality in the
interaction outcomes, which may vary spatiotemporally and depend on the guild and/or
taxa of the insect herbivores. Furthermore, due to the high host plant specificity by
insect herbivores, we suggest that is crucial the conservation of areas with huge plant
diversity to maintain insects' occurrence and their important roles in structuring
terrestrial communities in Brazilian Cerrado. Making that it is also possible that more
new species will be described, which will increases our knowledge about the Brazilian
biodiversity.
KEYWORDS: Bottom-up force, Endophytic insects, Herbivory, Natural history,
Spatio-temporal scale, Top-down force, Tritrophic interactions.
Spiders are ubiquitous in most vegetation, however very little empirical data are available on specific spider-plant interactions and their reciprocal outcomes. In the Brazilian Cerrado, the plant Mimosa setosa var. paludosa, (Fabaceae) has glandular trichomes in its leaves and stems, commonly entrapping insects (i.e. carrion) as well as hosting the lynx spider, Peucetia flava. We hypothesized that: (1) the damage inflicted by exophytic (leaves) and endophytic (seeds) herbivore insects that overcome the glandular trichomes is lower in plants where the lynx spider is present ; and (2) the presence of this predator is positively related to food availability (live insects and/or carrion) and plant size. We performed field observations and an experimental field study in terms of the spider's presence versus absence on the Fabaceae plants. Our results showed that the proportion of damaged foliolules on the Fabaceae plants differed between the spiders-present and spiders-absent treatments , and that the absence of spiders led to a 3.3-fold increase in the number of damaged foliolules. However, there was no significant difference in the proportion of seeds taken by endophytic herbivores from branches with and without spiders. We also found that the presence of Peucetia flava was positively related to the presence of entrapped carrion on plants, and that there was a positive and marginally significant effect of increasing abundance of the spiders on taller plants. The results of this study suggest that it is more common to find lynx spiders interacting with M. setosa var. paludosa in larger plants with higher carrion abundance (food source), and that P. flava and M. setosa var. paludosa interact in a facultative mutualism, in which plants provide entrapped carrion for spiders to feed on and possibly facilitate prey manipulation. In return, lynx spiders decrease the damage inflicted by exophytic, but not by endophytic herbivores. These results also contribute to a better understanding of which ecological factors may affect plant selection by lynx spiders and what the influence of this predator is on the structure of food webs in glandular plants.
All mutualistic plant–animal interactions are mediated by costs and benefits in relationships where resources (from plants) are exchanged by services (from animals). The most common trading coin that plants offer to pay for animal services is nectar; the main servers are hymenopterans. Extrafloral nectar (EFN) is produced in almost all aboveground plant parts not directly related with pollination, and their true function has long been an issue of discussion among naturalists and will be our main subject. The protective function of extrafloral nectaries (EFNs) is reviewed and considered with an alternative hypothesis, presenting not only ants, but also spiders and wasps as potential and effective agents in these protective interactions. Despite their likely relevance, the phenological variation (mainly sequential flowering and resprouting) of host plants mediating these interactions have been generally ignored. We discuss how the outcomes of each ant–EFN bearing plant interaction vary depending on physical and biotic changes in interacting organisms (internal factors such as phenology and species identity) as well as in their environments (external factors such as climatic variation), all of which may modify the character of each interaction. We propose that ant–EFN bearing plant interactions serve an excellent and unique model to test the “Geographic Mosaic Theory” of coevolution providing us a more clear view of how evolution has structured these plant–animal ecological networks.
Interactions between ants and hemipterans (Auchenorryncha e Sternorryncha) are important to understand the impact of multitrophic relationships on arthropod diversity on vegetation. The present field study experimentally investigates the outcomes of a multispecies interaction involving four components: ants, hemipteran trophobionts (Enchenopa brasiliensis Strümpel, chewing herbivores, and host plant (Solanum lycocarpum St. Hill). The occurrence of temporal variation in the outcomes of the relationships was also investigated. Results showed that ants were benefited by a rich food source predictable in time and space, while membracids survived better under ant attendance. Ant tending also had a positive impact on treehopper fecundity. Presence of ant-hemipteran associations was demonstrated to benefit the host plant through a significant reduction in herbivory caused by chewing insects.
Predators affect plant fitness when they forage on them and reduce the action of herbivores. Our study evaluates the complementary effects of spiders and ants that visit the extrafloral nectaries of Eriotheca gracilipes(Malvaceae) on the production of fruits and viable seeds of these savanna trees. Four experimental groups were established: control group – with free access of spiders and ants; exclusion group – spiders and ants excluded; ant group – absence of spiders; and spider group – absence of ants. The presence of ants reduced the spider richness; however, the presence of spiders did not affect the ant richness. A significantly higher number of fruits per buds were found in the presence of spiders alone or spiders and ants together (control group) compared with the absence of both predators (exclusion group). The number of seeds per fruits and seed viability were higher in the control group. This is the first study showing that spiders and ants may exert a positive and complementary effect on the reproductive value of an extrafloral nectaried plant. Mostly the impact of ants and/or spiders on herbivores is considered, whereas our study reinforces the importance of evaluating the effect of multiple predators simultaneously, exploring how the interactions among predators with distinct skills may affect the herbivores and the plants on which they forage.
Using Evarcha culicivora, an East African jumping spider (Salticidae), we investigate how nectar meals function in concert with predation specifically at the juvenile stage between emerging from the egg sac and the first encounter with prey. Using plants and using artificial nectar consisting of sugar alone or sugar plus amino acids, we show that the plant species (Lantana camara, Ricinus communis, Parthenium hysterophorus), the particular sugars in the artificial nectar (sucrose, fructose, glucose, maltose), the concentration of sugar (20%, 5%, 1%) and the duration of pre-feeding fasts (3 days, 6 days) influence the spider's prey-capture proficiency on the next day after the nectar meal. However, there were no significant effects of amino acids. Our findings suggest that benefits from nectar feeding are derived primarily from access to particular sugars, with fructose and sucrose being the most beneficial, glucose being intermediate and maltose being no better than a water-only control.
Habitat fragmentation strongly affects the abundance, distribution, body size and population genetics of invertebrates. Urban growth in Brazil has led to severe fragmentation, especially in the Atlantic Forest and savannas. The effects of this fragmentation on the common funnel-web spider Aglaoctenus lagotis were examined in two forest fragments within the interior savanna: a smaller fragment within an urban environment and a larger fragment within a rural environment. The reproductive period occurred in October, coinciding with the beginning of the rainy season, when the species was aggregated in the two forest fragments. The smaller fragment contained a larger population, and the spiders had a larger average prosoma size and web area. The presence of a larger population in a smaller area within the urban centre may reflect a limited dispersal ability, reduced predator abundance or low interspecific competition. The larger prosoma length and web area in the smaller habitat fragment suggest greater resource availability and a higher probability of capturing prey in the urban environment. In both areas, a larger number of capture threads was positively correlated with the presence of inquiline spiders in the webs. The genetic data indicate close similarity between and within the two areas, indicating that the species has low genetic variability or that the areas studied, consistent with their proximity, have separated only recently. Most savannas and forests in midwestern Brazil have recently undergone severe fragmentation, and further studies of this nature are needed.
More than 80 incidences of fish predation by semi-aquatic spiders - observed at the fringes of shallow freshwater streams, rivers, lakes, ponds, swamps, and fens - are reviewed. We provide evidence that fish predation by semi-aquatic spiders is geographically widespread, occurring on all continents except Antarctica. Fish predation by spiders appears to be more common in warmer areas between 40° S and 40° N. The fish captured by spiders, usually ranging from 2-6 cm in length, are among the most common fish taxa occurring in their respective geographic area (e.g., mosquitofish [Gambusia spp.] in the southeastern USA, fish of the order Characiformes in the Neotropics, killifish [Aphyosemion spp.] in Central and West Africa, as well as Australian native fish of the genera Galaxias, Melanotaenia, and Pseudomugil). Naturally occurring fish predation has been witnessed in more than a dozen spider species from the superfamily Lycosoidea (families Pisauridae, Trechaleidae, and Lycosidae), in two species of the superfamily Ctenoidea (family Ctenidae), and in one species of the superfamily Corinnoidea (family Liocranidae). The majority of reports on fish predation by spiders referred to pisaurid spiders of the genera Dolomedes and Nilus (>75% of observed incidences). There is laboratory evidence that spiders from several more families (e.g., the water spider Argyroneta aquatica [Cybaeidae], the intertidal spider Desis marina [Desidae], and the 'swimming' huntsman spider Heteropoda natans [Sparassidae]) predate fish as well. Our finding of such a large diversity of spider families being engaged in fish predation is novel. Semi-aquatic spiders captured fish whose body length exceeded the spiders' body length (the captured fish being, on average, 2.2 times as long as the spiders). Evidence suggests that fish prey might be an occasional prey item of substantial nutritional importance.
Orb-weaving spiders (Araneidae) are commonly regarded as generalist insect predators but resources provided by plants such as pollen may be an important dietary supplementation. Their webs snare insect prey, but can also trap aerial plankton like pollen and fungal spores. When recycling their orb webs, the spiders may therefore also feed on adhering pollen grains or fungal spores via extraoral digestion. In this study we measured stable isotope ratios in the bodies of two araneid species (Aculepeira ceropegia and Araneus diadematus), their potential prey and pollen to determine the relative contribution of pollen to their diet. We found that about 25% of juvenile orb-weaving spiders' diet consisted of pollen, the other 75% of flying insects, mainly small dipterans and hymenopterans. The pollen grains in our study were too large to be taken up accidentally by the spiders and had first to be digested extraorally by enzymes in an active act of consumption. Therefore, pollen can be seen as a substantial component of the spiders' diet. This finding suggests that these spiders need to be classified as omnivores rather than pure carnivores.
We predicted that because plant nectar is high in energy, it is likely to provide multiple benefits to spiders that
spend a substantial amount of energy foraging. In three laboratory experiments, we tested the effects of dietary extrafloral
nectar on the survival, molting, and activity of two foliage wanderers, Cheiracanthium mildei L. Koch 1864 (Miturgidae)
and Hibana velox (Becker 1879) (Anyphaenidae), both highly active, quick-moving nocturnal foragers. Extrafloral nectar
contributed significantly to survival and molting in prey-deprived H. velox. On a marginal diet of prey (one Drosophila
adult on alternate days) offered to spiders as soon as they emerged, 97% of C. mildei underwent their first molt if they also
received nectar, compared to 7% of controls without nectar. On a marginal diet of prey (one Drosophila adult on alternate
days) offered to spiders starting two days after their emergence, 78% of the spiders also receiving nectar molted, compared
to 0% of controls without nectar. Video recordings of activity showed that prey-deprived groups of C. mildei maintained
their active nocturnal foraging for many days on nectar, whereas controls became increasingly quiescent until they died.
Non-web-building spiders that feed on nectar may utilize its energy for foraging and thereby allocate the nutrients of prey
to maintenance and growth.
Prey specialization and the predatory behavior of two European ant-eating zodariid spiders, Zodarion germanicum and Zodarion rubidum, were studied in detail. The spiders were offered 12 ant species and seven other insects (termites, beetles, aphids, silverfish, flies, crickets and grasshoppers). Study spiders turned out to be ant specialists as they were able to subdue many ant species but ignored all other insects, except termites, which they attacked but rarely subdued. The best capture success was obtained with medium-sized ants (e.g. Lasius and Formica). The predatory behavior of the zodariid spiders involves an attacking and a handling phase separated by a period of waiting at a safe distance. The attacking phase consisted of a very rapid lunge from the rear, followed by a bite on the most extended ant leg. After an attack, the spider retreated to a safe distance, perhaps an indication that natural selection has favored such caution in the presence of an aggressive prey. The spider waited until the ant ceased moving. Such predatory behavior, which limits contact with the predator and prey, is clearly an effective means of handling a dangerous prey.
Evarcha culicivora, an East African jumping spider, is known for feeding indirectly on vertebrate blood by actively choosing blood-carrying mosquitoes as prey. Using cold-anthrone tests to detect fructose, we demonstrate that E. culicivora also feeds on nectar. Field-collected individuals, found on the plant Lantana camara, tested positive for plant sugar (fructose). In the laboratory, E. culicivora tested positive for fructose after being kept with L. camara or one of another ten plant species (Aloe vera, Clerodendron magnifica, Hamelia patens, Lantana montevideo, Leonotis nepetaefolia, Parthenium hysterophorus, Ricinus communis, Senna didymobotrya, Striga asiatica, and Verbena trivernia). Our findings demonstrate that E. culicivora acquires fructose from its natural diet and can ingest fructose directly from plant nectaries. However, experiments in the laboratory also show that E. culicivora can obtain fructose indirectly by feeding on prey that have fed on fructose, implying a need to consider this possibility when field-collected spiders test positive for fructose. In laboratory tests, 53.5% of 1,215 small juveniles, but only 3.4% of 622 adult E. culicivora, left with plants for 24 hours, were positive for fructose. These findings, along with the field data, suggest that fructose is especially important for early-instar juveniles of E. culicivora.
Interactions between ants and hemipterans (Auchenorryncha e Sternorryncha) are
important to understand the impact of multitrophic relationships on arthropod diversity on vegetation.
The present field study experimentally investigates the outcomes of a multispecies interaction involving
four components: ants, hemipteran trophobionts (Enchenopa brasiliensis Strümpel, chewing
herbivores, and host plant (Solanum lycocarpum St. Hill). The occurrence of temporal variation in
the outcomes of the relationships was also investigated. Results showed that ants were benefited by
a rich food source predictable in time and space, while membracids survived better under ant
attendance. Ant tending also had a positive impact on treehopper fecundity. Presence of ant-hemipteran
associations was demonstrated to benefit the host plant through a significant reduction in herbivory
caused by chewing insects.
Using cold-anthrone tests, spiders collected in the field were sampled for the presence of plant sugar (fructose). The spiders came from three different habitats: a cotton field, a mixed rape and fava bean field, and a park with flowering woody and herbaceous plants. The percentages of fructose-positive spiders were compared among the different habitats, as well as among the different sexes and ages of Ebrechtella tricuspidata (F.) (Araneae Thomisidae). Out of 745 field-collected spiders, 18.7% were positive for fructose, indicating that these spiders feed on plant nectar. Of the 12 families of spiders represented, individuals from 9 families were positive for fructose: Oxyopidae, Thomisidae, Pisauridae, Salticidae, Lycosidae, Tetragnathidae, Araneidae, Nephilidae, and Agelenidae. All members of the other three families (Linyphiidae, Clubionidae and Theridiidae) were negative for fructose. There were no differences for nectar feeding in spiders among the three habitats: 19.3% of individuals from the cotton field, 16.6% from the mixed rape and fava bean field, and 20.0% in park with flowering woody and herbaceous plants tested positive for fructose. For E. tricuspidata, significantly more females were positive than males (87.5% versus 42.9%); and immatures tested positive at a lower rate than adults (26.5% and 66.7%, respectively).
Nectivory was studied in 90 species from the spider family Salticidae. Observations of 31 of these species feeding on nectar from flowers in nature was the impetus for laboratory tests in which all 90 species fed from flowers. That sugar, not just water, is relevant to salticids was implied by choice tests where salticids spent more time drinking from a simulated nectar source (30% sucrose solution) than from distilled water. Our findings suggest that nectar feeding may be widespread, if not routine, in salticid spiders.
The initial energy supply of emerging spiderlings is relatively meagre, so survival without feeding on insects during a spell of bad weather is limited to a period of a few days or weeks. During our investigations, spiderlings of Thomisus onustus (Arachnida, Thomisidae) were kept on different diets. There was a significant difference in survival rate between spiderlings that were starved or fed on pollen, nectar, or Drosophila. The results showed that pollen and nectar can be a source of energy for spiders for an extensive period. This demonstrates another way in which spiders may survive starvation when insect prey is lacking and thus ensure the survival of a whole population.
Nectar properties tend to be similar for plants visited by the same kinds of pollinators, and much of the available information on nectar chemistry has been collected in the context of pollination syndromes. These are defined as broad associations between floral features and types of animal pollinators (Faegri & van der Pijl, 1979; Proctor et al., 1996) and are discussed further by Nicolson (2007, Chapter 7 in this volume). Faegri and van der Pijl included nectar volume in their classic descriptions of the various syndromes. The concept was extended to include nectar chemistry (specifically sugar and amino acid content and composition) in the influential reviews of Baker and Baker (1982a 1983b). Herbert and Irene Baker analysed many different substances in nectar and were largely responsible for drawing attention to its chemical complexity. However, the adaptive significance of nectar components has perhaps been overemphasized and is now being examined more critically.
Current evidence suggests that ant–plant relationships may influence species composition, abundance, and interactions at the
community scale. The main resource that plants offer to ants is extrafloral nectar (EFN) and the major part of published studies
shown benefits from ants to plants possessing EFNs. However, the complementary question of whether and how ants benefit from
EFNs is rarely addressed. Here, we present the results of a long-term study to demonstrate whether EFN has a positive effect
on ant colony fitness. We quantified colony growth rate, survival and the final weight of individuals as measures of benefit
derived from EFN. Our results provide clear evidence that EFN can have a significant positive impact on the survivorship,
growth and reproduction of the Myrmicinae Cephalotes pusillus. In fact, a diet rich in EFN (providing at least 30cal per day) resulted in five times more individuals per colony, greater
body weights, and more eggs. These results have shed new light on the relationships between ants and EFN-bearing plants such
as in tropical and temperate systems. The ant C. pusillus is the first case in which we have firm evidence that EFN improves colony growth and development, corroborating more than
100years of experimental evidence of benefits to plants in these widespread relationships.
Keywords
Cephalotes
–
Chamaecrista
–Colony growth rate–Mutualism–Tropical
Stenophagy (narrow diet breadth) represents an extreme of trophic specialization in carnivores, but little is known about the forces driving its evolution. We used spiders, the most diversified group of terrestrial predators, to investigate whether stenophagy (1) promoted diversification; (2) was phylogenetically conserved and evolutionarily derived state; and (3) was determined either by geographical distribution and foraging guild. We used published data on the prey of almost 600 species. Six categories of stenophagy were found: myrmecophagy, araneophagy, lepidopterophagy, termitophagy, dipterophagy, and crustaceophagy. We found that the species diversity of euryphagous genera and families was similar to stenophagous genera and families. At the family level, stenophagy evolved repeatedly and independently. Within families, the basal condition was oligophagy or euryphagy. Most types of stenophagy were clearly derived: myrmecophagy in Zodariidae; lepidopterophagy in Araneidae; dipterophagy in Theridiidae. In contrast, araneophagy was confined to basal and intermediate lineages, suggesting its ancestral condition. The diet breadth of species from the tropics and subtropics was less diverse than species from the temperate zone. Diet breadth was lower in cursorial spiders compared to web-building species. Thus, the evolution of stenophagy in spiders appears to be complex and governed by phylogeny as well as by ecological determinants.
Plants produce nectar to attract pollinators in the case of floral nectar (FN) and defenders in the case of extrafloral nectar (EFN). Whereas nectars must function in the context of plant-animal mutualisms, their chemical composition makes them also attractive for non-mutualistic, exploiting organisms: nectar robbers and nectar-infesting microorganisms. We reviewed the chemical composition of both FNs and EFNs and found that nectar composition appears tailored to fulfil these ambivalent roles. Carbohydrates and amino acids usually function in the attraction of mutualists and appear adapted to the physiological needs of the respective mutualists. Volatiles are a further group of compounds that serves in the attractive function of nectars. By contrast, secondary compounds such as alkaloids and phenols serve the protection from nectar robbers, and most nectar proteins that have been characterised to date protect FN and EFN from microbial infestation. Nectar components serve both in attraction and the protection of nectar.
We measured the effects of plant nectar consumption on Cheiracanthium inclusum (Hentz) (Miturgidae), an agriculturally important spider. Newly emerged spiderlings were reared on the eggs of Helicoverpa zea (Boddie) at four prey densities, 1, 5, 25, or 125 eggs, three times a week, with or without nectar. Nectar came from the extrafloral nectaries of Indian almond, Terminalia cattapa L. (Combretaceae). The addition of nectar to prey (1) allowed spiderlings on the 1-egg diet to survive longer and molt many more times; (2) allowed virtually all of the spiderlings on the 5-egg diet to become small adults and 50% to mate and reproduce versus those without nectar, none of which matured to adulthood; and (3) increased fecundity of females on 5-egg and 25-egg diets to the level of females fed five times the amount of prey. These results show that spiders that feed on nectar increase their fitness with increased survival, growth, and fecundity, particularly when density of prey is inadequate or marginal.
Spiders, a group of predominantly insectivorous predators, occasionally use plant food to supplement their insect prey. In the current review, we tracked down 95 reported incidents of spiders feeding on plant food under natural conditions. Globally, >60 spider species representing ten families have been observed feeding on plant materials from over 20 plant families. Cursorial spiders including the families Anyphaenidae, Clubionidae, Eutichuridae, Salticidae, Thomisidae, and Trachelidae dominate among the spiders feeding on plant food (>80% of reported incidents). Spiders feed on a wide diversity of plant-derived products including floral nectar, extrafloral nectar, stigmatic exudate, plant sap, honeydew, seeds, Beltian bodies, Müllerian bodies and pollen (originating from very different plant types such as coniferous and deciduous trees, herbaceous plants and shrubs, annual weeds, grasses, climbing plants, orchids, carnivorous plants, and ferns). Furthermore, spiders have been shown to consume fungal spores in laboratory trials. Supplementary feeding on plant materials by spiders was shown to be global in extent and widespread across spider taxa, plant taxa and plant materials; however, the extent to which the different categories of plant food contribute to the spiders’ diet and how this may affect their behavior and life history is still largely unexplored. This review is expected to lay a foundation for future research on this topic.
The range of prey theoretically available to a given species of spider is called its potential prey. It is usually determined by the method used to trap or catch all arthropods in the habitat in which the spider species lives. For methods, see Southwood (1978). The potential prey of epigeous spiders, for example, consists mainly of Collembola, Diptera (Brachycera), Coleoptera, Hymenoptera (Formicoidea), Araneae and, to a lesser extent, Hemiptera. Spiders hunting on vegetation have a potential prey spectrum of Hemiptera (Aphidina, Cicadina), Diptera, Coleoptera, Araneae and Collembola, but less Hymenoptera (mainly parasitic wasps). Diptera (Nematocera), Hemiptera (Aphidina, Cicadina), Hymenoptera (parasitic wasps) and Coleoptera, but less Collembola or Araneae (order according to decreasing abundance) are available to web-building spiders which filter their prey from the air (Nentwig 1981).
Nectar is the most important reward offered by plants to pollinating animals. This book is a modern and interdisciplinary text on nectar and nectaries, prompted by the expansion of knowledge, especially in the more ecological and now molecular fields, and the strong recent interest in pollination biology. The topics covered vary widely: they include historical aspects, the structure and ultrastructure of nectaries and relationships to plant systematics, the dynamics of nectar secretion, nectar chemistry and the molecular biology of defence proteins, adaptations to insect and vertebrate nectar consumers and consequences for pollination ecology, and broad-scale studies of nectar resources at the community level.
The study of the thermal and water relations of spiders began with observations on the thermal relations of growth (Wagner 1888), with experiments on temperature sensing (Gaubert 1892; Mclndoo 1911) and with the description of interspecific differences in the drinking behaviour of spiders (Gerhardt 1923, 1928b). Millot and Fontaine (1937) measured the water content of ecologically different species, introducing both a comparative approach and experimental methods into the analysis of spider water relations. Autecological aspects were introduced by Weese (1924), who studied the response of various spiders to humidity gradients, and by Savory (1930), who related the habitat choice of two araneids, Zygiella x-notata and Z. atrica, to positive and negative hygrotaxis, respectively. Palmgren (1939) combined both field and laboratory studies and demonstrated that access to water is crucial in the habitat selection of a pisaurid,Dolomedes fimbriatus.
There is a growing body of evidence for a wide range of spider families that they use nectar as supplementary resource, while pollen feeding in web-building spiders has been studied in the laboratory including a few species only. Considering that many spiders use nectar provided by plants, we can assume a greater potential for mutualistic interactions between plants and spiders as currently found in the literature as it is known, for example, for ants and plants. We certainly need more data on pollen feeding in spiders, but it is very likely that many web-building spiders use pollen when available. To judge the importance of herbivory for spiders and their classification as pure carnivores, however, we need data on the proportion incorporated into the body in relation to prey catches.
We examined the effects of the sit-and-wait spider Misumenops argenteus (Thomisidae) on the herbivore assemblage and fitness of the perennial woody shrub Trichogoniopsis adenantha (Asteraceae). Because crab spiders prey on both pollinators and phytophagous insects, they can have potentially negative and positive effects on plants. In a manipulative experiment using paired plants, spiders decreased the density of sucking and some endophagous herbivores on the leaves and capitula and reduced the number of damaged achenes produced by the plants. Damaged capitula had a higher proportion of fertilized achenes in plants with spiders than without spiders, but not undamaged capitula. These results indicate that M. argenteus exerted a double positive effect on seed production in T. adenantha. The effect of M. argenteus on herbivores may be taxon specific and vary among years with different herbivore abundances.
Spiders are known to influence plant fitness, and vice versa. Yet, it has not been appreciated that these facultative relationships can be mutualistic. I examined the interaction between Phryganoporus candidus, a subsocial Australian spider, and the ex-trafloral nectary-bearing shrub Acacia ligulata to explore variability in mutualistic inter-actions over a three-year period. Spiders enhanced seed production by reducing seed pre-dation by heteropterans, wasps, and weevils. Because spider colonies occupy only a fraction of a plant's volume, average benefits ranged from 0.4 to 6% increases in whole-plant seed production. These benefits were strongest in years of low seed production, suggesting that spiders may buffer plants against female reproductive failure. To evaluate benefits for spiders, I established experimental spider colonies on three common hosts. Spider perfor-mance (persistence and prey capture rates) on live A. ligulata and live hopbush Dodonaea viscosa exceeded that on dead acacia, suggesting that live hosts are more beneficial than dead hosts. Stable-isotope analyses demonstrated that colonies living on the three hosts differed substantially in diet, providing a possible mechanism for the observed differential suitability of hosts. However, the analyses were unable to establish conclusively that A. ligulata extrafloral nectar was an important reward for spiders. Variability in the A. ligulata– P. candidus system suggests that plant–spider associations, like other facultative protection relationships, likely vary along a continuum from antagonism to mutualism.
Multiple predators often have effects on their common prey populations that cannot be predicted by summing the effects of each predator at a time. When predators forage on the same vegetation substrate, intraguild interactions might cause emergent outcomes for the plants on which the predators co-occur. We experimentally evaluated the effects of spiders and ants on herbivory and reproduction in the extrafloral nectary-bearing tree Qualea multiflora (Vochysiaceae). Plants were divided in four experimental groups, depending on the presence or absence of ants and spiders. We compared the effects of each treatment on richness and abundance of chewing and sucking herbivores and on herbivory (leaf area loss). We also evaluated the impact of predators on the production of buds, fruits and seeds, and weight of the fruits. The presence of ants reduced the abundance and richness of spiders, but spiders did not affect the abundance and richness of ants. Only the removal of ants resulted in a significant increase in the abundance of herbivores and herbivore richness. Herbivory, however, was also affected by spiders. In addition, we found a significant interaction effect of ants and spiders on herbivory, indicating an emergent multiple predator effect. Neither ants nor spiders had an impact on the number of buds produced, number of fruits per bud, and seeds per fruits or fruit weight. This study highlights the importance of evaluating the effect of the predator fauna as a whole and not only one specific group on herbivory.
Many plants secrete nectar from extrafloral nectaries (EFNs), specialized structures that usually attract ants which can
act as plant defenders. We examined the nectar-mediated interactions between Chamaecrista nictitans (Caesalpineaceae) and jumping spiders (Araneae, Salticidae) for 2 years in old fields in New Jersey, USA. Previous research
suggests that spiders are entirely carnivorous, yet jumping spiders (Eris sp. and Metaphidippus sp.) on C. nictitans collected nectar in addition to feeding on herbivores, ants, bees, and other spiders. In a controlled-environment experiment,
when given a choice between C. nictitans with or without active EFNs, foraging spiders spent 86% of their time on plants with nectar. C. nictitans with resident jumping spiders did set significantly more seed than plants with no spiders, indicating a beneficial effect
from these predators. However, the presence of jumping spiders did not decrease numbers of Sennius cruentatus (Bruchidae), a specialist seed predator of C. nictitans. Jumping spiders may provide additional, unexpected defense to plants possessing EFNs. Plants with EFNs may therefore have
beneficial interactions with other arthropod predators in addition to nectar-collecting ants.
Selection might favor group foraging and social feeding when prey are distributed in patches that do not last long enough for a solitary individual to consume more than a small fraction of them (Pulliam and Millikan 1982; Pulliam and Caraco 1984). Here we considered the foraging behavior of a social spider, Anelosimus eximius, in light of this ephemeral resource hypothesis. This species builds large webs in which members cooperate to capture a wide variety of different sizes and types of prey, many of which are very large. The capture success of this species was very high across all prey sizes, presumably due to the fact that they foraged in groups. Group consumption times in natural colonies for all prey larger than five mm were less than the time that dead insects remained on the plastic sheets that we used as artificial webs. Solitary consumption estimates, calculated from the rate at which laboratory individuals extracted insect biomass while feeding, were the same as the residence times of insects on artificial webs in the field for insects between 6 and 15 mm in length and were significantly longer than the persistence of insects on plastic sheets for all larger insects. Large prey, that contribute substantially to colony energy supplies, appeared to be ephemeral resources for these spiders that could not be consumed by a single spider in the time they were available. These factors made the food intake of one spider in a group less sensitive to scavenging by others and could act to reinforce the social system of this species.
Misumenoides formosipes is a protandrous, semelparous crab spider common on flowers in North America. Females are 20–50 times heavier than males, which seldom feed on prey as adults, but search for and guard potential mates. Nectivory, previously unproven for spiders, was observed in male M. formosipes. Males were studied on Queen Anne's lace, Daucus carota, to determine the importance of nectar as an energy and water source and its effect on male longevity. Because of their low mass and large surface-to-volume ratio males were more prone to dehydration than females. Drinking nectar replaced fluid that males lost through evaporation, although dew and rainwater were more efficient sources of fluid because the volume per nectary was very small. Males preferred drinking a simulated nectar source (30% sucrose solution) to water, and even when satiated with water would still drink the sucrose solution, suggesting nectar was used as an energy source. Males offered nectar for an hour a day lived longer than males given only water. Nectar feeding may have evolved because of the selective advantage of increased longevity for male reproductive success.
Studies of ant–plant relationships elucidate how top-down effects of the third trophic level can affect the biomass, richness, and/or species composition of plants. Although widespread in the neotropics, few studies have so far examined the direct effects of ants on plant fitness. Here, through experimental manipulation (ant-exclusion) under natural conditions, we examined the effect of ant visitation to extrafloral nectaries on leaf herbivory and fruit set in Chamaecrista debilis in the Brazilian savanna. As opposed to other Chamaecrista species, our results showed that visiting ants (15 species) significantly reduce herbivory and increase fruit set by more than 50% compared to plants from which ants were excluded. This mutualistic system is facultative in nature, and corroborates the potential beneficial role of exudate-feeding ants as anti-herbivore agents of tropical plants.
Carnivorous arthropods are known to rely on non-prey foods, such as honeydew, pollen, and nectar. Consumption of plant-based nutrients by spiders also appears to be widespread, especially in cursorial species. This is not surprising, as studies have shown that these spiders' activity levels, survivorship, and reproduction are increased when their diet includes plant-based nutrients, especially under conditions of prey scarcity. However, the sensory and behavioral means by which they recognize and locate non-prey food is unknown. Here we show that immatures of a nectarivorous spider [Hibana futilis Banks (Araneae: Anyphaenidae)] can recognize and remember particular chemical stimuli associated with nectar. Following ingestion of minute amounts of sugar, these spiders exhibited counterturning and other local searching behaviors that increased their chances of finding more nectar. When placed on test arenas, spiders that were naïve with respect to nectar aroma located artificial nectaries composed of diluted honey significantly faster than unscented nectaries composed of 1 m sucrose solution. These results indicate that H. futilis is neurophysiologically and behaviorally adapted for recognizing olfactory stimuli. Interestingly, only spiders that ingested sugar and were engaged in local search responded to nectar aroma, suggesting that stimulation into local search is necessary to prime olfactory responses. We found that H. futilis could be conditioned to associate the presence of nectar with a novel aroma, in this case vanilla, and remember this aroma over the course of several hours. In arenas with vanilla-scented nectaries, spiders that had previous experience feeding on vanilla-scented sucrose droplets located the nectaries significantly faster than did vanilla-naïve spiders. The capacity to remember specific aromas could enhance the spiders' ability to find nectar, either when moving between different parts of the same plant or among different plant species. The results here indicate that nectarivorous spiders possess the sensory capabilities and programed behaviors necessary for efficient detection, recognition, and location of nectar sources.
Ants are probably the most dominant insect group on Earth, representing ten to fifteen percent of animal biomass in terrestrial ecosystems. Flowering plants, meanwhile, owe their evolutionary success to an array of interspecific interactionsâsuch as pollination, seed dispersal, and herbivoryâthat have helped to shape their great diversity. The Ecology and Evolution of Ant-Plant Interactions brings together findings from the scientific literature on the coevolution of ants and plants to provide a better understanding of the unparalleled success of these two remarkable groups, of interspecific interactions in general, and ultimately of terrestrial biological communities. The Ecology and Evolution of Ant-Plant Interactions synthesizes the dynamics of ant-plant interactions, including the sources of variation in their outcomes. Victor Rico-Gray and Paulo S. Oliveira capture both the emerging appreciation of the importance of these interactions within ecosystems and the developing approaches that place studies of these interactions into a broader ecological and evolutionary context. The collaboration of two internationally renowned scientists, The Ecology and Evolution of Ant-Plant Interactions will become a standard reference for understanding the complex interactions between these two taxa.
Spiders are thought to be strict predators. We describe a novel exception: Bagheera kiplingi, a Neotropical jumping spider (Salticidae) that exploits a well-studied ant-plant mutualism, is predominantly herbivorous. From behavioral field observations and stable-isotope analyses, we show that the main diet of this host-specific spider comprises specialized leaf tips (Beltian food bodies; Figure 1A) from Vachellia spp. ant-acacias (formerly Acacia spp.), structures traded for protection in the plant's coevolved mutualism with Pseudomyrmex spp. ants that inhabit its hollow thorns. This is the first report of a spider that feeds primarily and deliberately on plants.
Spiders are assumed to be strictly carnivorous in assessments of their nutritional and energetic requirements, their habitat preferences, and their potential as biological control agents. However, members of Salticidae (jumping spiders), Thomisidae (crab spiders), and the fast-moving Miturgidae, Anyphaenidae, and Corinnidae, all non-webbuilding wandering spiders, have been observed at floral and extrafloral nectaries of plants, presumably feeding on nectar. To test spiders in the field for nectar feeding, we used a cold anthrone test to detect the presence of ingested fructose, a plant-derived sugar, in wandering spiders occupying cotton plants (Gossypium hirsutum L.), which have floral and extrafloral nectaries. Field collections focused on three ecologically similar, highly active nocturnal spiders: Cheiracanthium inclusum (Hentz) (Miturgidae), Hibana futilis (Banks), and H. arunda (Platnick) (Anyphaenidae). During 2002 and 2003, 27 and 21%, respectively, of all field-collected adults and subadults tested positive for fructose, indicating consumption of extrafloral nectar. In both years, significantly more females were positive than males (38 versus 11% in 2002; 26 versus 12% in 2003). Immatures tested positive at a lower rate than adults (3 and 13%, respectively). Smaller numbers of spiders in the Lycosidae, Oxyopidae, and Thomisidae were also tested. Among the thomisids, 38% in 2002 and 41% in 2003 tested positive for fructose. None of the lycosids (wolf spiders) tested positive; two of nine oxyopids (lynx spiders) did test positive. Oxyopidae is new to the list of nectarivorous spiders. These results suggest that nectarivory is common for foliage wandering spiders and may contribute to fitness.
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