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The Evolutionary Significance of Extrafloral Nectar Production by Costus Woodsonii (Zingiberaceae): An Experimental Analysis of Ant Protection Author(s)
Abstract
(1) Observations and experiments were carried out in central Panama to examine the hypothesis that ants increase the reproductive success of Costus woodsonii. (2) The plant secretes extrafloral nectar from bracts on the inflorescence and the nectar is harvested by ants. (3) The fly Euxesta sp., a specialist on Costus woodsonii, oviposits beneath the bracts on immature fruit, and its larvae destroy the seeds and arils. (4) In both the dry and wet seasons, plants with ants experimentally removed had a higher rate of fly-oviposition and produced only one-third as many seeds as control plants with ants. (5) The ant Camponotus planatus was dominant in the dry season, and had less influence on seed production than had Wasmannia auropunctata, the wet-season dominant. (6) Among dry-season control plants, the probability of fruit maturation was significantly correlated with an index of ant activity based on the consistency of ant occupation. (7) As a consequence of larval damage to the arils, seeds from plants with ants excluded had a lower probability of dispersal in both dry and wet seasons than those from plants with ants.
... EFN placement is often crucial, promoting visitation to vulnerable areas such as meristems and young leaves, or inflorescences, where ants can protect against seed predators. Ants visiting EFNs on the inflorescences of the herb Costus woodsonii (Costacae) disrupt the oviposition behaviour of Euxesta picture-wing flies (Ulidiidae) that would otherwise reduce seed set as their larvae develop on Costus seeds (Schemske, 1980). Ants attracted by EFNs to the inflorescences of the perennial vine Canavalia cathartica (Fabaceae) go on to nest in cavities produced in the fruit by moth larvae and reduce the likelihood of further moth damage being done (Yamashiro & Yamashiro, 2008). ...
... Ants foraging on plant surfaces may prey upon herbivores, or disrupt their feeding and oviposition, whilst ants attracted by hemipteran honeydew may benefit the plants by reducing levels of more damaging herbivores (Strysky & Eubanks, 2007). Many plant species produce extrafloral nectar (EFN), which attracts ants, and which may be sited to encourage ants to patrol vulnerable areas such as new growth (Hodson & Gastreich, 2006) and inflorescences (Schemske, 1980). In tropical canopies plant exudates from hemipteran honeydew and/or EFN can support huge populations of potentially beneficial ants (Davidson, 1997;Tillberg, 2004). ...
... The high temperatures in the tropics may cause volatile chemicals released by fresh flowers to disperse more quickly, and thus only be detectable at sufficient concentrations very close to the flowers, so that the response becomes indistinguishable from a tactile response. Additionally, plants in the tropics face significantly higher herbivory (Rosumek et al, 2009) so the benefits of attending ants are greater, especially on inflorescences where ants can potentially reduce seed predation (Schemske, 1980). Thus close-range repellent traits may be preferable to scents that keep larger areas of the plant clear of ants and may also be cheaper to produce than longer-range scent signals. ...
... -Dobzhansky 1950 Many of the early evolutionary-ecological studies of tropical plant-animal mutualisms emphasized highly taxon-specific interactions, like the ant-Acacia (Janzen 1966), figs-fig wasps (Janzen 1979, Wiebes 1979, euglossine bees-orchids (Dressler 1968), and others. Recent data suggest that tropical mutualistic interactions involving an assemblage of species (each one a facultative partner) may be far more frequent than one-onone mutualisms (Herrera 1982, Schemske 1982, 1983, Feinsinger 1983, 1986a, 1988a, Howe 1984, Wheelwright 1985, Snow and Roubik 1987, particularly when the mutualists are not symbionts (Thompson 1982, Benson 1988 Many studies of plant-animal mutualisms have found tremendous variability among taxa in the magnitude of the beneficial effect received by the host plant (Bentley 1978, Schemske 1980, Howe and Vande Kerchove 1981, 1986a, Murray 1986, Bronstein and Hoffman 1987, Snow and Roubik 1987. For example, although plants invest resources in extrafloral nectar production to attract antguards, or in specialized structures to attract and reward pollinators, the animals that utilize these resources often vary tremendously in their beneficial effects on seed production, an important plant fitness component . ...
... -Dobzhansky 1950 Many of the early evolutionary-ecological studies of tropical plant-animal mutualisms emphasized highly taxon-specific interactions, like the ant-Acacia (Janzen 1966), figs-fig wasps (Janzen 1979, Wiebes 1979, euglossine bees-orchids (Dressler 1968), and others. Recent data suggest that tropical mutualistic interactions involving an assemblage of species (each one a facultative partner) may be far more frequent than one-onone mutualisms (Herrera 1982, Schemske 1982, 1983, Feinsinger 1983, 1986a, 1988a, Howe 1984, Wheelwright 1985, Snow and Roubik 1987, particularly when the mutualists are not symbionts (Thompson 1982, Benson 1988 Many studies of plant-animal mutualisms have found tremendous variability among taxa in the magnitude of the beneficial effect received by the host plant (Bentley 1978, Schemske 1980, Howe and Vande Kerchove 1981, 1986a, Murray 1986, Bronstein and Hoffman 1987, Snow and Roubik 1987. For example, although plants invest resources in extrafloral nectar production to attract antguards, or in specialized structures to attract and reward pollinators, the animals that utilize these resources often vary tremendously in their beneficial effects on seed production, an important plant fitness component . ...
... For the antguards, this taxon was Wasmannia auropunctata, which was generally of low abundance (X = 12.9% of inflorescences occupied, N = 16 site-year combinations, Appendix 1) and was the taxon with the most beneficial effect on plant reproductive success Schemske 1984, 1988a). In the pollinator assemblage, this taxon was Euglossa, which was generally of high relative abundance (X = 55.9% of observations, N = 12 site-year combinations, Appendix 2) but was not a particularly stellar pollinator (Schemske andHorvitz 1984, 1988). ...
Describes striking spatiotemporal variation in the antguard and pollinator mutualist assemblages of Calathea ovandensis (Marantaceae). Fifteen different ant taxa (in 5 subfamilies) and 5 pollinator taxa (4 euglossine bees and 1 anthophorid bee) were associated with the plants in Veracruz, Mexico. Mean number of taxa per site per year was 6.8 for ants and 3.6 for pollinators. The ant assemblage varied more than the pollinator assemblage, particularly spatially. The ant assemblage varied more through space than through time (means of the proportional similarities for pairwise comparisons of assemblages were 0.37 and 0.51, respectively), while the pollinator assemblage varied equally through space and time (means of the proportional similarities were 0.53 and 0.50, respectively). For individual taxa of both assemblages, the coefficient of variation in relative abundance was large (>75%) for most spatial and temporal comparisons. In each assemblage there was a single taxon that was the least variable, in both time and space, in its relative abundance. Results, coupled with previous findings of significant variation among mutualist taxa in the magnitude of their beneficial effects, indicate that plants may be subject to highly variable selection by their mutualist assemblages. The most beneficial antguard was consistently rare; the most beneficial pollinator was abundant in one site-year but rare or absent in most site-years. The taxon that was consistently abundant was not an efficient pollinator. Evolutionary specialization of plants on particular animals may be constrained by lack of constancy in the relative abundance of animals and the opportunity for specialization may differ greatly between interactions due to divergent patterns of constancy, rarity and quality. -from Authors
... When an ant bites a caterpillar, the latter vigorously bends its body towards the ant and frequently regurgitates, eventually inhibiting further ant attacks. Moreover, field experiments have demonstrated that the stick-like frass chains built by caterpillars at leaf margins ( Although chasing by ants can have an inhibitory effect on the oviposition behavior of female insects (Janzen 1967;Schemske 1980), this was not detected in our observations of E. bechina. Since ants do not chase egglaying Eunica, and the oviposition event lasts only 1-3 seconds, the differential occurrence of butterfly eggs on ant-visited and ant-excluded Caryocar plants (Oliveira 1997) presumably results from the discriminating abilities of the ovipositing female. ...
... Ants can inhibit herbivore occupation of host plants and have been thought to provide a consistent defense system relatively immune to evolutionary changes by the herbivore (Schemske, 1980). One may expect that lepidopteran larvae bearing ant-avoiding traits would have an advantage in the cerrado ant-rich environment. ...
The ecological success of ants is attributed to their eusocial mode of life, local abundance, and diversity of adaptations. Such traits result in a wide variety of feeding habits and foraging strategies, including the use of plant foliage as a foraging substrate. Intense foraging on vegetation appears to have set the scenario for a multitude of interactions with many plant species worldwide, ranging from facultative to obligate ant-plant associations. Incidentally, by frequently foraging on the plant surface ants often affect the life of a particular trophic group -- the herbivores. Most studies on ant-plant interactions, however, have focused on the deterrence by ants toward insect herbivores and its possible influence on plant fitness. Rarely has this interface been studied from the herbivore's standpoint. In this chapter we illustrate how intense ant activity on plant foliage can strongly affect the behavioral ecology of insect herbivores in the cerrado. We first present the factors that likely promote ant foraging on cerrado plants, and then describe two study cases in which the behavior of insect herbivores has been demonstrated to be closely linked with encountering ants on the plant surface.
... Extrafloral nectar is produced in secretory glands, generally not involved in pollination [1,9]. Extrafloral nectar-visiting ants can protect plants by deterring or preying upon leaf [7,10], bud and flower herbivores [8,[11][12][13], as well as pre-dispersal seed predators [14,15]. However, some studies have suggested that EFN-visiting ants may be ineffective in plant defense [16][17][18][19][20][21] or even have negative effects by repelling pollinators or the natural enemies of herbivores [16,[22][23][24][25][26]. ...
... Inouye and Taylor [14] demonstrated that ants visiting EFN from involucral bracts of Helianthella quinquenervis (Asteraceae) reduced seed predation by tephritid and agromyzid flies. Similarly, in Costus woodsonii (Zingiberaceae) ants attracted to EFN from bracts on the inflorescence negatively interfered with fly oviposition on immature fruits [11]. In Caryocar brasiliense (Caryocaraceae), EFN-visiting ants have been shown to prevent phytophagous insects from ovipositing on both buds and fruits [13]. ...
Extrafloral nectaries can occur in both vegetative and reproductive plant structures. In many Rubiaceae species in the Brazilian Cerrado, after corolla abscission, the floral nectary continues to secret nectar throughout fruit development originating post-floral pericarpial nectar-ies which commonly attract many ant species. The occurrence of such nectar secreting structures might be strategic for fruit protection against seed predators, as plants are expected to invest higher on more valuable and vulnerable parts. Here, we performed ant exclusion experiments to investigate whether the interaction with ants mediated by the peri-carpial nectaries of Tocoyena formosa affects plant reproductive success by reducing the number of pre-dispersal seed predators. We also assessed whether ant protection was dependent on ant species composition and resource availability. Although most of the plants were visited by large and aggressive ant species, such as Ectatomma tuberculatum and species of the genus Camponotus, ants did not protect fruits against seed predators. Furthermore , the result of the interaction was neither related to ant species composition nor to the availability of resources. We suggest that these results may be related to the nature and behavior of the most important seed predators, like Hemicolpus abdominalis weevil which the exoskeleton toughness prevent it from being predated by most ant species. On the other hand, not explored factors, such as reward quality, local ant abundance, ant colony characteristics and/or the presence of alternative energetic sources could also account for variations in ant frequency, composition, and finally ant protective effects, highlighting the conditionality of facultative plant-ant mutualisms.
... Les nectaires (organes de production de nectar) qui se retrouvent sur différentes parties des végétaux sont de deux grands types : les nectaires floraux, situés au niveau des fleurs et impliqués dans les processus de pollinisation, et les nectaires extrafloraux. L'hypothèse protectionniste prévaut pour expliquer l'apparition de ces derniers chez les végétaux : en effet, les fourmis attirées par ces ressources vont débarrasser la plante des herbivores rencontrés lors de leurs visites (de la Fuente et Marquis 1999, Oliveira et al. 1999, Jolivet 1996, Beattie 1985, Schemske 1980, mais voir aussi Zachariades et Midgley 1999). ...
... Bien que le régime alimentaire de W. auropunctata soit généraliste, le miellat des hémiptères qui se trouvent sur la végétation constitue une grande partie des ressources ramenées au nid par les ouvrières , Clark et al. 1982. Les ouvrières peuvent également récolter des nectars floraux ou extra-floraux sur la végétation (Schemske 1980). Pour que ces ressources soient exploitées sans une trop grande dépense d'énergie, la distance les séparant des nids doit être la plus courte possible, donc les colonies doivent être installées au plus prés Basselinia pancheri (Palmae, Figure 11A) et Meryta coriacea (Araliaceae, Figure 11B). ...
... Les nectaires (organes de production de nectar) qui se retrouvent sur différentes parties des végétaux sont de deux grands types : les nectaires floraux, situés au niveau des fleurs et impliqués dans les processus de pollinisation, et les nectaires extrafloraux. L'hypothèse protectionniste prévaut pour expliquer l'apparition de ces derniers chez les végétaux : en effet, les fourmis attirées par ces ressources vont débarrasser la plante des herbivores rencontrés lors de leurs visites (de la Fuente et Marquis 1999, Oliveira et al. 1999, Jolivet 1996, Beattie 1985, Schemske 1980, mais voir aussi Zachariades et Midgley 1999). ...
... Bien que le régime alimentaire de W. auropunctata soit généraliste, le miellat des hémiptères qui se trouvent sur la végétation constitue une grande partie des ressources ramenées au nid par les ouvrières , Clark et al. 1982. Les ouvrières peuvent également récolter des nectars floraux ou extra-floraux sur la végétation (Schemske 1980). Pour que ces ressources soient exploitées sans une trop grande dépense d'énergie, la distance les séparant des nids doit être la plus courte possible, donc les colonies doivent être installées au plus prés Basselinia pancheri (Palmae, Figure 11A) et Meryta coriacea (Araliaceae, Figure 11B). ...
... Extrafloral nectar is produced in secretory glands, generally not involved in pollination [1,9]. Extrafloral nectar-visiting ants can protect plants by deterring or preying upon leaf [7,10], bud and flower herbivores [8,[11][12][13], as well as pre-dispersal seed predators [14,15]. However, some studies have suggested that EFN-visiting ants may be ineffective in plant defense [16][17][18][19][20][21] or even have negative effects by repelling pollinators or the natural enemies of herbivores [16,[22][23][24][25][26]. ...
... Inouye and Taylor [14] demonstrated that ants visiting EFN from involucral bracts of Helianthella quinquenervis (Asteraceae) reduced seed predation by tephritid and agromyzid flies. Similarly, in Costus woodsonii (Zingiberaceae) ants attracted to EFN from bracts on the inflorescence negatively interfered with fly oviposition on immature fruits [11]. In Caryocar brasiliense (Caryocaraceae), EFN-visiting ants have been shown to prevent phytophagous insects from ovipositing on both buds and fruits [13]. ...
Extrafloral nectaries can occur in both vegetative and reproductive plant structures. In many Rubiaceae species in the Brazilian Cerrado, after corolla abscission, the floral nectary continues to secret nectar throughout fruit development originating post-floral pericarpial nectaries which commonly attract many ant species. The occurrence of such nectar secreting structures might be strategic for fruit protection against seed predators, as plants are expected to invest higher on more valuable and vulnerable parts. Here, we performed ant exclusion experiments to investigate whether the interaction with ants mediated by the pericarpial nectaries of Tocoyena formosa affects plant reproductive success by reducing the number of pre-dispersal seed predators. We also assessed whether ant protection was dependent on ant species composition and resource availability. Although most of the plants were visited by large and aggressive ant species, such as Ectatomma tuberculatum and species of the genus Camponotus, ants did not protect fruits against seed predators. Furthermore, the result of the interaction was neither related to ant species composition nor to the availability of resources. We suggest that these results may be related to the nature and behavior of the most important seed predators, like Hemicolpus abdominalis weevil which the exoskeleton toughness prevent it from being predated by most ant species. On the other hand, not explored factors, such as reward quality, local ant abundance, ant colony characteristics and/or the presence of alternative energetic sources could also account for variations in ant frequency, composition, and finally ant protective effects, highlighting the conditionality of facultative plant-ant mutualisms.
... Humboldtia brunonis attracts many ants to its inflorescences, just like some other plants that produce large amounts of extrafloral nectar on their flowers (Bentley, 1977;Inouye and Taylor, 1979;Schemske, 1980;Oliviera et al., 1999). Although in many cases ants have been reported to enhance seed set by their anti-herbivore behaviour (Bentley, 1977;Rico-Gray and Thien, 1989;Del-Claro et al., 1996;Willmer and Stone, 1997;Oliviera et al., 1999), their presence on flowers may also decrease pollination success and seed set (Puterbaugh, 1998;Galen, 1999;Ghazoul, 2001). ...
Questions: Do protective plant-ants perturb the pollination process and the reproduction of their host-plant? If they do, have partner selective mechanisms evolved against such conflicts? Organisms: The semi-myrmecophyte Humboldtia brunonis and its ant associates. Field site: Makut Reserve Forest, Western Ghats. South India. Methods: We tracked insect and extrafloral nectar activity on inflorescences of several trees over a 24 h cycle. We repeatedly measured the extrafloral nectar produced by bracts of flowers throughout their phenology from the bud stage until and beyond flower opening. We studied the behaviour of ants towards the reproductive apparatus of the flowers and conducted ant exclusion experiments to test for my negative effect on herbivores of fruit production. Conclusions: Pollinators did not visit inflorescences that had more than four ants on them. Ants. solely by their presence on bud bracts and bracteoles. intimidate other insects, both pollinators and herbivores. Some spatial and temporal mechanisms partially prevent negative ant-pollinator interactions. First. extrafloral nectar production on the bracts of flower buds, which attracts ants to inflorescences. was highest at night, attracting the largest numbers of ants at that time, whereas the major pollinators were active during the day. Second, this extrafloral nectar production declines after the first flower of each inflorescence opens. Third, the anthers and stigma are placed at the apex of a thin elongate axis, which offers a precarious foothold to ants. One ant species, Crematogaster dohrni, succeeds despite these difficulties by acting just before the flower-opens, and damaging the flower when the style and stamens are still folded. This is the fourth case of castration behaviour of a plant-ant directed against its host-plant. Despite its anti-herbivore protection of flower buds. this plant-ant has a negative impact on fruit production in H. brunonis.
... Extrafloral nectaries are those not involved in pollination, they are sugar producing glands found outside the flower. Several studies have shown that, in general, the main function of these nectaries is to attract insects, particularly ants, that protect the plant against herbivores (Keeler, 1980(Keeler, , 1981Schemske, 1980;Oliveira and Marcio, 1998). These nectar-secreting glands are structurally diverse and occur on virtually all aboveground plant organs; they are especially common on the leaf blade, petiole, young stems, stipules and on reproductive structures such as buds, calyx, inflorescence axis, flower peduncles and fruits (Elias, 1983;Oliveira and Leitao-Filho, 1987;Koptur, 1992;Diaz-Castelazo et al. 2004, 2005. ...
... 10). Other ants reported to be aggressive to herbivores, such as Wasmannia auropunctata, Azteca sp., and Solenopsis geminata (Schemske 1980 Longino 1984) were rare and their effects could not be quantified. ...
Rates of disappearance (mortality) in Heliconius caterpillars of various sizes were investigated by experimental placement on Passiflora host plants growing in their native rain forest habitat. Survivorship of experimental larvae was similar to that of Heliconius larvae in natural populations: 60% mortality during the initial 2 d, followed by 30% mortality during each 2-d period thereafter. Survivorship was not dependent on larval size or instar, nor was it related to larval growth rate or host plant isolation from surrounding foliage. However, survivorship was appreciably lower on host plants on which ants were attending extrafloral nectaries (70% vs. 45% mortality in first 2 d), indicating that ants may be a primary source of high mortality. I conclude that for these Heliconius, high first-instar mortality is not due to the small size of the caterpillars but rather is a consequence of ant attendance to some host plants; most caterpillars on plants with ants are killed in the first instar, while caterpillars on ant-free plants have much lower mortality and make up the majority of the cohort in later instars.
... Associações mutualísticas são extremamente comuns entre formigas e plantas, uma vez que tais agregações são abundantes e altamente diversas ao redor do mundo (HUXLEY; CUTLER, 1991). Em geral, nessas interações, as formigas encontram recursos nas plantas (locais de nidifi cação e alimento) e, em contrapartida, as formigas defendem a planta contra herbívoros (BENTLEY, 1977a;KOPTUR, 1979;SCHEMSKE, 1980;BEATTIE, 1985). O néctar produzido por nectários extrafl orais representa um dos mais importantes recursos açucarados que as formigas podem encontrar em mais de 93 famílias de angiospermas e em algumas famílias de samambaias (KOPTUR, 1992). ...
... The interaction of plants with their nectarfeeders has been shown to be a mutualistic antiherbivore defense: ants exclude or prey upon herbivores while visiting extrafloral nectaries (e.g. Bentley 1977, Tilman 1978, Inouye and Taylor 1979, Keeler 1980b, Schemske 1980, Beckmann and Stucky 1981, Stephenson 1982, but see also O'Dowd andCatchpole 1983, andTempel 1983 for counter-examples). ...
Since the Hawaiian Islands lack native ants, it was hypothesized that extrafloral nectaries, an ant-related mutualistic trait, should be lacking on native species. Presence of extrafloral nectaries (EFNs) on plants was determined by direct observation and related to vegetation structure and floral composition. Frequency of plants with EFNs was low by all possible comparisons. However, several endemic species had functional EFNs. The hypotheses to explain these anomalies are (1) phylogenetic inertia or (2) mutualism with some other organism than ants. /// Так как на Гавайских островах отсутствуют нативные муравьи, высказано предположение, что экстрафлоральные нектарники - мутуалистический признак, связанный с муравьями - должны отсутсвовать у туземных видов растений. Наличие экстрафлоральных нектарников (EFNs) у растений было установлено прямыми наблюдениями и связано со структурой растительности и флористическим составом. Частота встречаемости растений с EFNs низка при всех возможных сравнениях. Однако, некоторые эндемичные виды имеют функционирующие EFNs. Гипотезы для объяснения этих аномалий следующие: 1. филогенетическая инерция; 2. мутуализм с другими организмами, помимо муравьев.
... 10). Other ants reported to be aggressive to herbivores, such as Wasmannia auropunctata, Azteca sp., and Solenopsis geminata (Schemske 1980 Longino 1984) were rare and their effects could not be quantified. ...
I examined the role of ants in controlling the magnitude and distribution of caterpillar survival at Corcovado National Park, Costa Rica. Ants of 29 species were observed visiting the extrafloral nectary glands of Passiflora vitifolia and P. quadrangularis. Plants attended by ants had ants present 60% of the time. Approximately equal numbers of plants attended by ants and plants without ants were treated with Tanglefoot to exclude walking predators from a single branch on each plant. Heliconius ismenius caterpillars were placed on the treated plants and an equivalent set of unmanipulated controls, and their growth and survivorship were measured. Forty-eight percent of caterpillars died over a 2-d period on unmanipulated plants with many ants, while only 20, 22, and 23% died on unmanipulated plants with few ants, Tanglefoot-treated branches with many ants outside the Tanglefoot barrier, and Tanglefoot-treated branches with few ants outside the Tanglefoot barrier, respectively. This suggests that ants were the only significant walking predator of Heliconius ismenius caterpillars in this habitat, and that @?75% of the deaths observed on control plants were on plants with ants. After 4 d all caterpillars were replaced by a second set of caterpillars. Measurements of these latter individuals revealed that mortality was 62, 46, and 24% on control plants on which caterpillars previously survived for 0, 2, and 4 d, respectively. No trend was observed on branches with ants excluded. This indicates that the effects of ant predation are locally stable, i.e., that ant constancy causes plants to be heterogeneous in their suitability as host plants. Caterpillars thus are much more likely to survive on some plants than on others. Analysis of caterpillar growth rates did not reveal any effects on survival; i.e., slow-growing caterpillars survived as well as fast-growing ones.
... Several studies indicate that the pattern of ant attendance changes in direct relation to the level of nectar production, which in turn depends on the nectary's age, with peak attendance coïnciding with maximum nectar production (Bentley 1977a, Inouye & Taylor 1979, Keeler 1977, O'Dowd 1979, Schemske 1980. Heliconia (Heliconiaceae) is a genus of about 200-225 species of neotropical herbaceous plants (Kress 1994). ...
The neotropical understory plant Heliconia hirsuta is notable for the conspicuous presence of ants on its inflorescences. We recorded 17 ant species on inflorescences in a lowland forest in Trinidad, West Indies. The commonest of these in descending order were Ectatomma tuberculatum, Crematogaster sp., Solenopsis altinodis and Dolichoderus bispinosus. The ants collected exudate from the bracts, tended treehoppers (Membracidae), and nested on late-stage inflorescences, in addition to minor activities. Activity showed a distinct correlation with age of the inflorescence, with peak attendance in the middle developmental stages. The level of attendance by ants varied throughout the day. E. tuberculatum's alert responses to disturbance suggest that it may serve as an effective defender of Heliconia inflorescences against herbivores.
... Modusa procris, Componotus parius, Anoplolepis guanaiensis and C. pulverulentus was more or less gracilipis, flies are also seen to visit C. woodsonii for the Schemske (1980) germination and stigma receptivity in Moringa oleifera and Kay & Schemske (2003). According to Specht Lamk. ...
Costus woodsonii is a perennial herb, belongs to the family Costaceae under the order Zingiberales. Inflorescence
terminal, flowers emerge one at a time from bright red coloured bracts of inflorescence, flowers throughout the year.
Anthesis occurs between 05:00–06:00 and the average life span of individual flower is 1 day. Anther dehiscence
occurs between 03:00 and 03:30 through longitudinal slit. Flowers offer both nectar and pollen to visitors. Nectar
secreted both in bract and flower. Pollen grains are polyporate and remains as viable still after 13 hours after anther
dehiscence. Percentage of pollen viability is high at 07:00. High percentages of pollen grains are fertile (89.7 ± 0.8%)
on the day of anthesis. In vitro pollen germination is found maximum in 1% of sucrose solution. Stigma becomes more
receptive at 06:00 and stigma loss its receptivity after 15:00. Nectarinia asiatica, N. zeylonica are the main pollinators.
Autogamy, geitonogamy and xenogamy were carried out, to check whether the species is self compatible or not. Fruit
set on self pollinated flowers, revealed that C. woodsonii is self compatible.
... Such associations have been reported to effectively deter a variety of both vertebrate and invertebrate herbivores (Beattie, 1985;Fiala, 1994;Dejean, Djiéto-Lordon & Orivel, 2008). However, studies have concentrated on defence of leaves and shoots, and mutualistic ant defence against potential seed predators has rarely been considered (Inouye & Taylor, 1979;Schemske, 1980;Horovitz & Schemske, 1984). ...
Although plant-inhabiting ants are known to act as effective deterrents to a variety of vertebrate and invertebrate herbivores, this has been reported only once before for primates, a group better known for their predation of ants. In the present study, we investigated the effects that colonies of Pseudomyrmex viduus ants living in individual Macrolobium acaciifolium (Fabaceae) trees have on the rates of visitation and fruit removal by four taxa of seed-predating vertebrates: the primate Cacajao melanocephalus ouakary; macaws (Ara spp.); large parrots (Amazona spp.); and the Northern Amazonian red squirrel (Sciurus igniventris). We found that ant presence significantly reduced both rates of visitation and of fruit removal by C. m. ouakary. The same pattern of reduced fruit removal was also observed for other seed predators (parrots, macaws, and squirrels) but not for visitation rates (although this may be a result of the small sample size). This appears to be only the second-known demonstration of the repellent effect of ants on primates and, indeed, the first for squirrels and psittacine birds. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, ●●, ●●–●●.
... These glands are widely distributed among the angiosperms and present an enormous diversity in anatomy and morphology (e.g., Zimmermann 1932; Schnell et al. 1963; Elias 1983 ). A number of studies in different habitats show that ant visitors to EFNs can reduce herbivore damage to EFN-bearing plants (e.g., Bentley 1977a Bentley , 1977b Schemske 1980; and included references). Tropical floras usually contain a great number of plant taxa bearing EFNs, and recent surveys show that these plants are more abundant in tropical than in temperate communities (see Bentley 1977a; Keeler 198 1 ; Morellato and Oliveira 1991). ...
... In Neotropical species where the extrafloral nectaries have been studied, the nectar attracts ants that protect the inflorescence against oviposition by flies. These flies oviposit in immature fruit and their larvae destroy the seeds and arils of the plant resulting in seed loss (Schemske 1980(Schemske , 1982. The length of the calli ranges from 1-3 mm. ...
A taxonomic revision of the African genera of Costaceae (Costus and Paracostus) is given. Within the genus Costus 24 species are recognized, 8 of which are here described as new and one is given a new name. Included are chapters on the history of the taxonomy of the family, morphology, flower biology, pollination, dispersal, distribution, ecology, phylogeny and molecular studies and conservation. The species treatments include descriptions, full synonymy, geographical and ecological notes and taxonomic notes. For all species distribution maps are provided. A complete identification list with all exsiccatae studied and an index to scientific names is included at the end.
... Alguns experimentos demonstraram a proteção contra herbívoros para a planta quando ocorrem visitações de formigas em seus nectários, como demonstram os trabalhos de romero (2002) com espécies de Camponotus sp. e de aLmeida & figueredo (2003) com C. sericeiventris. Há um efeito benéfico para as plantas com a eliminação dos herbívoros pelas formigas (sCHemske 1980;stHePHenson 1982), uma vez que a área foliar não é diminuída e há uma redução nas vias de infecção por patógenos nas áreas herbivoradas. ...
Camponotus sericeiventris Guérin are described as omnivorous, their diet including floral and extrafloral nectar, exudates of hemipteran and lepidopteran, prey, seed and fruit foraged in the environment. The aim of this study was to examine the foraging behavior of C. sericeiventris, correlating the foraging activity and climatic factors as well as quantify and identify the resources exploited by the species and time of the foraging
and action range. The specie studied was influenced positively by variations in the temperature. In most of the returns (94.81%, n = 7,072) the ants did not carry a load visible. Only 5.19% (n = 387) of the returns were identified and distributed as feces (35.40%, n = 137), animal protein (27.65%, n= 107) and vegetable fiber (36, 95%, n = 143). Two foraging trails, from colony to trees where ants were seeking resources, were measured (73 and 86 m) representing an average of the distance of 79.5 ± 9.19 m, resulting in 19,596 m² of colony action. The duration of foraging of the C. sericeiventris had an average of 67 ± 16’97’’ (37’03’’- 101’) minutes. The results of this study provide important insights into understanding the dynamics of foraging activity of the C. sericeiventris in the human environment. Moreover, it shows the interaction of this specie with the nvironmental.
... Although surprising, this result was not wholly unexpected. While several authors have observed increased EFN production on and around developing fruit, in line with optimal defense theory (Holland et al. 2009;Falcão et al. 2014), few studies have shown ants to reduce pre-dispersal seed predation (but see Inouye & Taylor 1979;Schemske 1980). Lenoir and Pihlgren (2006) observed 10 species of ants attracted to EFNs of the Bush vetch, Vicia sepium L. (Fabaceae). ...
Extrafloral nectar mediates food-for-protection mutualisms between plants and ants. Ant-plant mutualisms are keystone associations, occurring within a complex web of biotic interactions. As such, these interactions may affect plant fitness in a number of ways, both positive and negative. In Senna mexicana var. chapmanii (Isely) H. S. Irwin & Barneby (Fabaceae), the presence of ants has been shown to reduce herbivory and increase fruit and seed set. These effects, however, are not the result of only one interaction but the balance of many. We conducted a field study to determine the processes by which ants affect reproductive fitness in S. chapmanii. Thirty plants were established in a semi-natural area adjacent to native pine rockland habitat in southern Florida. Ants were excluded from half of the plants by painting a sticky resin (Tanglefoot™) around the base of each stem. Over the course of a single flowering season (Oct-May), we observed the effects of ants on the activity of herbivores, predators, pollinators, and pre-dispersal seed predators. We also observed the overall effects of ants on plant size and reproductive output. Plants with ants were quicker to establish, grew larger, and produced floral displays that attracted more pollinators. Contrary to our expectations, relative pollinator efficiency and rates of pre-dispersal seed predation were unaffected by ants. In S. chapmanii, ants did not appear to affect the outcome of other plant-insect associations, but they affected the scale at which they occurred. Ants facilitated plant growth and establishment in S. chapmanii, with subsequent effects on reproductive investment.
... Geralmente, espécies do gênero Costus crescem em baixa densidade populacional. A maioria tem ramos espirais com inflorescências terminais que produzem apenas uma flor por dia (raramente duas) e apresenta um período de floração estendido (Schemske, 1980;1981;1982;1983;Kay e Schemske, 2003). ...
... Geralmente, espécies do gênero Costus crescem em baixa densidade populacional. A maioria tem ramos espirais com inflorescências terminais que produzem apenas uma flor por dia (raramente duas) e apresenta um período de floração estendido (Schemske, 1980;1981;1982;1983;Kay e Schemske, 2003). ...
... Um caso particular de interação que merece especial atenção envolve plantas que possuem nectários extraflorais e formigas que forrageiam em busca de néctar (Elias 1983). Se por um lado o benefício obtido pela formiga pode ser facilmente detectado, por outro, a eficiência da proteção contra a herbivoria é de difícil constatação, não podendo ser considerada de forma generalizada (Schemske 1980). Irlbachia alata é uma planta colonizadora de clareiras e bordas de fragmentos de floresta (Machado et al. 1998) que possui nectários extraflorais (NEFs) e uma arquitetura particularmente apropriada para testes de hipóteses sobre a eficiência da proteção das formigas. ...
Introdução Interações entre formigas e plantas têm sido reconhecidas como fundamentais para a manutenção da diversidade de espécies nas florestas tropicais, no entanto a forma como cada componente beneficia ou é beneficiado pelo outro ainda não está completamente esclarecido. Um caso particular de interação que merece especial atenção envolve plantas que possuem nectários extraflorais e formigas que forrageiam em busca de néctar (Elias 1983). Se por um lado o benefício obtido pela formiga pode ser facilmente detectado, por outro, a eficiência da proteção contra a herbivoria é de difícil constatação, não podendo ser considerada de forma generalizada (Schemske 1980). Irlbachia alata é uma planta colonizadora de clareiras e bordas de fragmentos de floresta (Machado et al. 1998) que possui nectários extraflorais (NEFs) e uma arquitetura particularmente apropriada para testes de hipóteses sobre a eficiência da proteção das formigas. Essa espécie apresenta duas inflorescências terminais e NEFs no cálice, persistentes até a fase final do fruto. Partindo da premissa de que a eficiência de proteção depende da freqüência e da dinâmica das formigas sobre as estruturas florais de I. alata, foram testadas as seguintes hipóteses: 1) existe correlação entre o número de estruturas reprodutivas (botões, flores e frutos) da planta e o número de formigas visitando; 2) existe diferença na freqüência de vistas das formigas às diferentes estruturas florais; 3) a freqüência de visitas das formigas é maior nas estruturas com herbívoros presentes (iscas) do que nas estruturas sem herbívoros e 4) em média as formigas visitam em tempos mais curtos as estruturas com herbívoros (iscas) do que aquela s sem herbívoros. Material e Métodos As análises foram realizadas a partir da seleção aleatória de dez indivíduos de I. alata presentes no Parque Estadual Dois Irmãos (8º7'30''S; 34º52'30''W), um remanescente de floresta ombrófila aberta com 388,67ha, localizado no município de Recife, Pernambuco. Foram contados os números de estruturas reprodutivas de cada indivíduo e verificada a freqüência de visita das formigas a cada uma das estruturas. A freqüência das formigas foi registrada em intervalos de uma hora, durante dez horas consecutivas (100 observações). Foram consideradas visitadas apenas as estruturas que possuíam formigas no exato momento da primeira visualização. Uma estrutura reprodutiva de cada indivíduo de I. alata foi selecionada para verificar se Camponotus sp.2 (a formiga mais freqüente) seria capaz de detectar a presença de herbívoros e/ou visitava com maior freqüência às estruturas com herbívoros presentes. Em um primeiro momento, foi registrado o número de estruturas visitadas pela formiga antes de encontrar a estrutura selecionada (i.e., grupo controle). Posteriormente, foram colocadas iscas (i.e., cupim) e novamente registrado o número de estruturas visitadas antes que a formiga encontrasse a isca (i.e., grupo experimental).
... W. auropunctata feeds on almost all available food sources. Its choice of food may include other invertebrates, plant parts or seeds (Clark et al. 1982;Romanski, 2001), nectar produced by plants (Schemske, 1980;Smiley, 1986) and on sugary honeydew excreted by different insects such as aphids, mealybugs, scale insects and whiteflies (Delabie et al. 1994;Naumann, 1994). Wherever food is found, W. auropunctata will congregate in large numbers to feed and to carry the food away to the waiting queen and brood (Clark et al. 1994;Armbrecht and Ulloa-Chaon, 2003). ...
The hypothesis that the understory herbs Costus allenii and C. laevis (Zingiberaceae) have converged in floral characteristics to use the same pollinator was investigated in central Panama. Observations and experiments indicated that these species (1) occupy the same habitats, (2) flower synchronously, (3) are identical in flower color, morphology, and nectar secretion patterns, (4) share the same pollinator, the bee Euglossa imperialis, (5) are self-compatible, but not autogamous, and (6) have strong barriers to hybridization. Both grow in low density along streamsides and produce a single flower per day for an extended period (up to 4 mo). Flower density is depressed through extensive predation by the weevil Cholus cinctus, which damaged 31% of all C. allenii and 60% of all C. laevis inflorescences. Direct observation of foraging bees indicated that individuals regularly visit both plant species. An experimental analysis of interspecific pollen transfer using powered paint as a marker verified these results; 97% of the flowers checked had received heterospecific visits. The high probability of interspecific pollination did not affect fruiting success. I suggest that low flower density, exaggerated by extreme floral predation, has selected for floral similarity and pollinator sharing in these species. Floral convergence increases effective flower density and nectar supplies, and probably increases the regularity and rate of pollinator visitation.
(1) The benefit and loss provided to oak trees by wood ants were assessed in a Quercus dentata chaparral located in a supercolony of the red wood ant, Formica yessensis. (2) Ants decreased the numbers of leaf feeders such as lepidopteran larvae and weevils, thereby reducing leaf loss; however, aphid numbers increased in the presence of ants. (3) Acorn production was similar on trees with and without ants, but the percentage of acorns not infested by acorn borers was much higher on ant-abundant trees (48.8%) than on trees where ants were infrequent (27.7%). (4) These results support the presence of an indirect mutualism between oaks and wood ants via myrmecophilous aphids.
As the most species-rich and biologically eclectic of all social insects, ants present considerable challenges to the process of cataloguing and understanding their remarkable diversity. Substantial progress has been made in recent years, however, in identifying the major clades of ants and in clarifying their evolutionary history. We now have a higher classification of ants in which most of the subfamilies and tribes appear to be monophyletic and well diagnosed, with a few notable exceptions. Uncertainty persists regarding the phylogenetic relationships among old lineages at the base of the ant tree and concerning the time frame of ant evolution. The specieslevel taxonomy of ants has advanced more fitfully, and ant ecologists have an extensive but far-from-complete set of resources for identifying ant species. Ongoing and sustained effort is needed in the area of species discovery and delimitation, and in the delivery of this information to potential users.
In an examination of the “ant-guard” hypothesis for plant defence, simple probability models are proposed to describe the distribution of insects over developing flowerheads, some of which are “attended” by ants, and some of which are not. A Monte Carlo approach is adopted to examine the goodness of fit of the models to the data. By means of the modelling, a complex data set can be described by just two parameters. Shortcomings of the models are discussed, and avenues for further work are outlined.
Experimentally excluded ants from one member of pairs of fronds within patches of Pteridium aquilinum at Skipwith Common, North Yorks. In addition, we compared the herbivore populations of bracken patches which had naturally different ant densities; this was done at 2 sites in northern England. Although ant activity on treatment fronds was significantly reduced, there was no effect on the total number of species per frond, nor on the population sizes of most species, compared to control fronds. Only one species, the hemipteran Monalocoris filicis was unequivocally more common on fronds from which ants were excluded. Between-patch comparisons showed no differences in total herbivore species richness on sites with markedly different number of ants. Differences between the populations of individual species revealed varying patterns which were difficult to relate to ant density. It is concluded that the effects of ant predation are feeble relative to other environmental or host-plant influences acting on M. filicis; for all other bracken herbivores, ant predation effects appear to be non-existent. Alternative hypotheses for the bracken nectary-ant association are discussed. We suggest that evolutionary adaptions amongst the herbivores, in response to ant predation, may now place most of the bracken insects in 'enemy-free space'. The association may be maintained by continuing mild selection if the ants are effective against non-adapted generalist species and potential colonists. -from Authors
This study examined a complex interaction among species, focused on (1) a neotropical perennial plant, Calathea ovandensis (Marantaceae), that produces extrafloral nectar, (2) ants that visit the nectaries, (3) an ant-tended specialist herbivore, Eurybia elvina (Lepidoptera: Riodiniadae), that feeds on buds, flowers, and fruits, and (4) other herbivores of reproductive tissues. We experimentally investigated: (1) to what extent seed production was influenced by ants and herbivores, and (2) whether spatial variation in seed production was influenced by spatial variation in the ant community. The lowest seed production (x = 6) was for inflorescences with Eurybia but without ants. Highest seed production (x = 21) was for inflorescences with ants, but without Eurybia. In the presence of ants, Eurybia lowered mean seed production by 33%. In the absence of ants, Eurybia lowered mean seed production by 66%. The eight ant species differed greatly in the magnitude of their beneficial effects on seed production. Ants were not equally distributed over sites, and spatial hetrogeneity in seed production by Calathea reflected differences in ant communities among sites. We concluded that variation and interdependence of various components of plant-animal interactions are likely to result in variation in the magnitude of their beneficial or detrimental impact on plants. Such variation should be incorporated into plant demograpic models as spatially varying alternate life history paths to yield insight into the evolutionary impact of plant-animal interactions.
(1) The influence of wood ants (Formica lugubris Zett.) on populations of bracken herbivores was studied at sites in North Yorkshire, England. (2) Ant-exclusion experiments at one site, using a grease-banding technique, produced no significant changes in the abundances of the insect herbivores present. (3) In contrast, experimental introductions and encounters between ants and herbivores revealed that F. lugubris can readily find and remove most external feeders within a few hours. Only sawfly larvae, Aneugmenus spp., showed any significant immunity to predation by wood ants. They exhibited reflex bleeding when attacked by ants and were apparently highly distasteful. (4) A survey of the herbivore faunas on bracken at matched sites with and without ants revealed consistently lower populations of external feeders at sites where F. lugubris was present, but the only significant difference was for the guild of sucking insects. Only two species, Aneugmenus spp. and an aphid (Macrosiphum ptericolens), were apparently immune to the ants, as were all internally feeding miners and gall formers. (5) This is the first demonstration that ants can have any, even weak, effects on populations of common bracken herbivores in contemporary time. The effectiveness of these aggressive wood ants as protectors of bracken is discussed in relation to the evolution of extrafloral nectaries and the possible mutualistic role of ants.
The antioxidant and antimicrobial activity of the methanolic extracts of various plant parts of Costus woodsonii were evaluated. The total phenolic content and total flavonoid content in leaves and inflorescence extracts were higher compared to the rhizome and stem extracts. Highest total tannin content was noted in the inflorescence. Leaves extracts demonstrated the strongest 2,2-diphenyl-1-picrylhydrazyl scavenging and ferric reducing power activity (IC50 = 1.3 ± 0.2 mg mL⁻¹; FRP = 3.8 ± 0.5 mg mL⁻¹). Rhizome extract showed ferrous ion chelating activity with CC50 at 2.7 ± 0.3 mg mL⁻¹. The leaves extract demonstrated antimicrobial activities against various Staphylococcus aureus strains (MIC: 0.625 mg mL⁻¹ and 1.25 mg mL⁻¹). Liquid chromatography-mass spectrometry (LCMS-MS) analysis showed that rutin and quercetin-3-galactoside were found in leaves; epicatechin in the inflorescences; and dioscin in the rhizomes.
The hypothesis that ants attracted to the nectar secreted by bracken fern (Pteridium aquilinum Kuhn) foliar nectaries protect the frond from herbivore damage was tested experimentally in three New Jersey populations. There was no difference in the amount of herbivore damage experienced by control ferns and those from which ants were excluded. Sugar secretion rates were highest in fiddleheads just prior to the start of frond enlargement, and ant activity was highest on fronds in this developmental stage. Both sugar secretion and ant activity decreased during frond enlargement to low levels at maturity. Despite considerable variability among fronds in sugar secretion, population sugar production and ant activity remained constant through most of the summer. The developmental and seasonal patterns of nectar secretion therefore fit those that would be predicted if bracken and ants were engaged in a mutualistic interaction, but there is no evidence that the ferns in fact derived any benefit from their ant visitors.
Extrafloral nectaries are secretory glands, usually found on leaves, that have been shown to promote ant defense against the insect herbivores of many modem day plants. Extrafloral nectaries were found on the 35-million-year-old fossil leaves of the extinct Populus crassa from Florissant, Colorado. Extinct ant species (belonging to five still extant genera that have modem ant-guard species), and other predators and parasitoids (whose modem relatives frequent extrafloral nectaries) also lived at Florissant. The extrafloral nectaries of P. crassa (and perhaps other plants) probably operated to attract ants and/or other arthropod defenders as early as the Oligocene.
The reproductive biology of Ipomoea pes-caprae, a pantropical beach morning glory, was studied at five sites around the Gulf of Mexico. The primary pollinators were Xylocopa species (carpenter bees) which dispersed pollen up to 90 m. Exclusion experiments demonstrated that ants feeding on extrafloral nectaries increased seed set but did not protect seeds from predation by the bruchid beetle Megacerus. The water-dispersed seed and long-range dispersal of pollen may function to counter the sporophytic incompatability mechanism of the plant; populations exhibit a large neighborhood size. Key reproductive factors in the life cycle of I. pes-caprae are the long-range pollen flow and mass germination of water-dispersed seeds.
The structure and distribution of defense nectaries in the genus Ipomoea (Convolvulaceae) were investigated. These nectaries do not reward pollinators and probably contribute to antiherbivore defense. Of 22 species sectioned, 15 had defense nectaries on the sepals. Of 12 other species observed, ten had sepal nectaries and two did not. Structurally, 14 of the species sectioned had crypt sepal nectaries and one had a basin nectary. Of the 14 species with crypt nectaries, two had invaginated spaces adding greatly to the internal area of these nectaries, and forming the most complex nectaries that have been reported. We term these labyrinthine crypt nectaries. All three types of nectaries are lined with secretory trichomes along the proximal surfaces of the crypts. Species with defense nectaries on the sepals tend to have petiolar defense nectaries as well, but the two locations may have different nectary types; e.g., basins on the petiole and crypts on the sepals. Since most reports of the function of these nectaries have shown antiherbivore defense by nectar feeders, the distributions of defense nectaries with respect to region and life history of the species were sought. Plants without sepal nectaries were found to have significantly smaller seeds than plants with sepal nectaries; they were also more frequently annuals. No significant relationship was found between region or breeding system and defense nectaries.
We present a quantitative synthesis of trophic cascades in terrestrial systems using data from 41 studies, reporting 60 independent tests. The studies covered a wide range of taxa in various terrestrial systems with varying degrees of species diversity. We quantified the average magnitude of direct effects of carnivores on herbivore prey and indirect effects of carnivores on plants. We examined how the effect magnitudes varied with type of carnivores in the study system, food web diversity, and experimental protocol. A metaanalysis of the data revealed that trophic cascades were common among the studies. Exceptions to this general trend did arise. In some cases, trophic cascades were expected not to occur, and they did not. In other cases, the direct effects of carnivores on herbivores were stronger than the indirect effects of carnivores on plants, indicating that top‐down effects attenuated. Top‐down effects usually attenuated whenever plants contained antiherbivore defenses or when herbivore species diversity was high. Conclusions about the strength of top‐down effects of carnivores varied with the type of carnivore and with the plant‐response variable measured. Vertebrate carnivores generally had stronger effects than invertebrate carnivores. Carnivores, in general, had stronger effects when the response was measured as plant damage rather than as plant biomass or plant reproductive output. We caution, therefore, that conclusions about the strength of top‐down effects could be an artifact of the plant‐response variable measured. We also found that mesocosm experiments generally had weaker effect magnitudes than open‐plot field experiments or observational experiments. Trophic cascades in terrestrial systems, although not a universal phenomenon, are a consistent response throughout the published studies reviewed here. Our analysis thus suggests that they occur more frequently in terrestrial systems than currently believed. Moreover, the mechanisms and strengths of top‐down effects of carnivores are equivalent to those found in other types of systems (e.g., aquatic environments).
Plants provide protection (domatia), alternative food (nectar, exudates, pollen) and chemical lures which benefit predatory arthropods and thereby protect plants against herbivorous arthropods. Experimental evidence for these indirect effects is reviewed and hypotheses are provided to explain why plants invest in attracting, feeding and protecting predatory arthropods despite the fact that (1) other organisms not beneficial to the plant may utilize these facilities too, and (2) also competing neighbour-plants may profit from these investments. It is argued that although the plant may benefit under certain conditions, plant-bodyguard interactions do not have a single anticipated outcome. Instead, these interactions may have a range of positive, neutral and negative outcomes, the exact value of which depends on position in space and moment in time. The benefits to the plant investing in indirect defence depend on the availability and responsiveness of predatory arthropods, the abundance and responses of cheaters, the degree to which neighbouring plants profit from these investments, and the extent to which other plants in the environment invest or harbour profitable prey. Possibilities for indirect plant defence to arise from coevolution are discussed.
Pteridium aquilinum was studied at sites in northern England, and New Mexico. Bracken extrafloral nectaries secrete sugars and amino acids at low and variable rates. Nectar production increased rapidly to a peak in mid-June, then declined slowly to zero in late August. Seasonal patterns of ant activity on bracken fronds usually mirrored nectar availability. Spatially, ants were often, but not always, randomly distributed among fronds within a patch. The maximum potential predation rates which ants might impose on bracken herbivores were measured. Calculated attack rates indicated a high potential impact of ants on bracken herbivore populations. Other insect species visiting extrafloral nectaries on bracken include potential natural enemies (both predators and parasitoids); 'robbers' that steal nectar; and 'robber-herbivores', with adults that feed on nectaries and larvae that are bracken-specific herbivores. The hypothesis that the nectaries facilitate a mutualistic association with ants, which in turn defend the plant against insect herbivores, is discussed. The bracken-extrafloral nectary-ant association closely resembles many other ant-extrafloral nectary systems independently evolved by other plants, where ants are known to have a defensive role. Paradoxically, despite high attack rates on introduced caterpillars, available evidence suggests that the ants have no significant effect on bracken-specific herbivores. -from Authors
Present study focuses on the different groups of arthropods visiting extrafloral nectaries of Ipomoea pes-caprae and the interactions among these different groups of arthropods. Diurnal activity patterns of arthropods on nectaries were recorded. This study also reports the presence of similar extrafloral nectaries in other species of Ipomoea.
Perennial, rhizomatous, non-aromatic herbs, terrestrial or more rarely epiphytic. Indumentum of uniseriate, multicellular or unicellular hairs. Stems terete, most often unbranched, leafy, sometimes spirally contorted; when branched, then secondary branches breaking through the leaf sheaths (Tapeinochilus). Leaves spirally arranged, sheaths closed, tubular; ligule present; petiole short; pulvinus absent; lamina narrowly to broadly elliptic, rolled up from one side to the other in bud. Inflorescence a strobilaceous spike, terminal on the leafy shoot or on a separate, short, leafless shoot, or flowers solitary, axillary (Monocostus). Bracts imbricate, with a linear, nectariferous callus below the tip, each subtending 1–2 flowers; bracteoles tubular or folded. Flowers epigynous, perfect, zygomorphic; calyx tubular, shortly 2–3-lobed; corolla 3-lobed, the lobes basally fused, imbricate in bud, unequal; stamen 1, often petaloid, bearing 2 2-sporangiate thecae, dehiscing introrsely by longitudinal slits, often appendaged at the apex. Labellum petaloid, staminodial, opposite to the stamen, as long as or much longer than the corolla, ± 3-lobed, often with crisped margin; basal part of stamen and labellum united into a papillate tube. Gynoecium 3(−2)-carpellate; ovary inferior, 3(−2)-Jocular; placentation axile; ovules numerous, anatropous, crassinucellar; septal nectaries 2, immersed in the apical part of the ovary; style filiform, commonly enclosed between the thecae; stigma Wet, with or without a dorsal appendage. Fruit a 3(−2)-locular capsule crowned by the persistent calyx, dehiscing loculicidally, rarely explosively, or indehiscent and irregularly breaking when old. Seeds numerous, aril white to yellow; operculum next to the prominent radicle; embryo straight; endosperm poorly developed; perisperm abundant, with copious starch in simple grains.
All species are self-compatible, and require a treefall gap for germination and establishment. Self-pollination resulted in lower seed output in all species; this difference was significant for Costus allenii and C. laevis. Seedling growth of selfed, outcrossed and naturally-pollinated Costus allenii, C. laevis and C. guanaiensis in sun and shade habitats in the greenhouse was unaffected by breeding system, but significantly affected by habitat, with reduced growth in shade. Selfed progeny had the lowest biomass in all treatments, with inbreeding depression for growth ranging from 8-25% compared to out-crossed performance. Reduced growth and greater variation in growth for selfed, as compared to out-crossed, progeny are consistent with the hypothesis that inbreeding depression in these species results from homozygosity of rare, deleterious alleles which are not expressed in the heterozygous state. Relative biomass production varied more between sun and shade habitats for selfed, than outcrossed or naturally-pollinated progeny, suggesting that increased homozygosity following inbreeding reduces genotypic versatility.-from Author
From scorching, barren deserts to humid tropical forests, from deep in the soil, to high in the tree canopies, ants are everywhere! Comprising a substantial part of living biomass on earth, ants are integral to the functioning of terrestrial ecosystems. More than 12,000 species have been described to date, and it is estimated that perhaps as many still await classification. Their social structure provides a rich ground for exploring how division of labour affects the acquisition of resources, foraging and defensive behaviours, and coevolution with the flora and fauna with which they interact. The study of ants has led to significant advances in our understanding of insect evolution, global diversity patterns, competitive interactions, mutualisms, ecosystem's responses to change, and biological invasions. Ant Ecology explores these and other key ecological issues and new developments in myrmecology across a range of scales. The book begins with a global perspective on species diversity in time and space and explores interactions at the community level before describing the population ecology of these social insects. The final section covers the recent ecological phenomenon of invasive ants: how they move across the globe, invade, affect ecosystems, and are managed by humans. Each chapter links ant ecology to broader ecological principles, provides a succinct summary, and discusses future research directions. The Synthesis and Perspectives highlights contributions of ant ecology to ecology more broadly, and outlines promising areas for future research.
Field experiments, designed to imitate the role of extrafloral nectaries, demonstrate that ants attracted to sugar droplets on plants can reduce the level of herbivore damage. This protection is more effective in disturbed habitats, such as forest clearings and edges, where ant-forager abundance is high. Natural nectary-bearing plants are more abundant in these same habitats. Other forms of disturbance such as annual flooding and fire, reduce ant abundance, reduce protection levels, and alter the frequency of natural nectary plants.
The North American black cherry, Prunus serotina Ehrh., has extrafloral nectaries which are most active during the first 3 wk after budbreak. These nectaries attract large numbers of the ant Formica obscuripes Forel, especially to trees within @?20 m of an ant colony. The average number of ant visits per bud is highest just after budbreak, decreasing as the number of active extrafloral nectaries decreases. These ants are predacious on many species of insects found on P. serotina, including the eastern tent caterpillar, Malacosoma americanum Fabricus, the major defoliator of black cherry. Formica obscuripes is only able to prey upon M. americanuum within @?3 wk of budbreak, after which time, tent caterpillar larvae are large enough that most escape ant predation. Tent caterpillar survivorship was found to be positively related to distance from colonies of F. obscuripes. It is suggested that the ant-cherry relationship is a faculative mutualism and that nectar production is timed so as to maximize the chance of successful ant predation on tent-caterpillar colonies.
Observations have been made on the nectar flow rates of the extrafloral nectaries on the pedicels of a number of individuals of the shrub Bixa orellana, growing in Costa Rica, and on the ant activities on the same plants. Damage to the flower buds by insects just prior to flower-opening can result in high abortion rates. Greatest nectar flow rates and ant activity were associated with this particularly vulnerable stage of development. More buds mature to ripe fruits on plants with higher visitation rates of ants at the extra-floral nectaries. The results suggest that the presence of numerous ants on a plant reduces the activities of phytophagous insects, and raises its relative reproductive fitness through increased production of fruits.
lpomoea carnea (Convolvulaceae) possesses two types of extrafloral nectaries, located on the petiole and on the pedicel. These secrete a complex nectar containing sugars and amino acids. The insects attracted to the extrafloral nectaries are predominantly ants and they are relatively abundant throughout the year. A number of incidents of plant defense as a result of the presence of extrafloral nectary visitors at the extrafloral nectaries of I. carnea were observed and are consistent with the ant-guard theory of the function of extrafloral nectaries.
Helianthella quinquenervis (Asteraceae), the aspen sunflower, secretes sugar and amino acid rich nectar from involucral bracts during bud and flowering stages. The nectar is usually collected by ants as fast as it is secreted. H. quinquenervis is subject to predispersal seed predation by larvae of several insect species, primarily tephritid flies, an agromyzid fly, and 3 Lepidoptera. When present, ants interrupt oviposition efforts by the female flies but do not appear to be effective against lepidopteran or mammalian herbivores. The degree of protection by ants conferred upon plants was investigated by excluding ants from some plants and by correlating ant density with subsequent damage to ovules and developing seeds. At higher elevations (2896 and 3091 m) damage to plants with ants was significantly reduced compared with plants without ants. At a lower elevation (2734 m) where seed predator and ant densities were highest, the ants were less effective as deterrents and predation on ovules and seeds usually exceeded 60%. Flowers of some other composite species in the same habitats appear to be more effectively protected from predation by chemical deterrents, raising questions of the relative benefits of chemical deterrents compared to ants as a means of protection.
Higher activity of midgut microsomal oxidase enzymes in polyphagous than in monophagous species indicates that the natural
function of these enzymes is to detoxify natural insecticides present in the larval food plants. Differing strategies of adaptation
to plant defenses may partly account for the great diversity of insect herbivores.
Plant trichomes can act as efjective defenses against herbivores, but at least one species of ithomiid butterfly, Mechanitis
isthmia, has evolved a unique adaptation for avoiding the trichomes on its spiny Solanum hosts. The larvae are gregarious
all together they spin a fine silk scaffolding over the tops of the spines on which they can crawl and feed in safety.
Studies of the trumpet creeper, Campsis radicans (L.) Seem. (Bignoniaceae), reveal five distinct nectary systems, a phenomenon never before reported among temperate zone plants.
Ant activity, centered around the four extrafloral systems, clearly demonstrates the ant-guard symbiosis usually associated
only with tropical or subtropical species. Floral nectar, an attractant for hummingbird and bumblebee pollinators, differs
chemically from the ant-attracting nectar produced extraflorally.