Characterization of microsatellite markers for the invasive ant species Anoplolepis gracilipes

We present primer sequences for eight polymorphic microsatellite loci for the formicine ant Anoplolepis gracilipes, a serious pest species in South‐East Asia and Pacific islands and still spreading on all continents. Microsatellite loci were isolated with a highly efficient method of enrichment. The number of alleles ranged from two to 19 with an observed heterozygosity ranging from 0.842 to 1.0. The markers were designed for a sociogenetic study as well as for population genetics.     

Not all ants are equal: obligate acacia ants provide different levels of protection against mega‐herbivores

In obligate ant–plant mutualisms, the asymmetric engagement of a single plant species with multiple ant species provides the opportunity for partners to vary in their behaviour. Variation in behaviour has implications for the interactions with third‐party species such as herbivores. This study assessed the effect of obligate ant‐mutualists (Crematogaster mimosae, Crematogaster nigriceps and Tetraponera penzigi) inhabiting the African ant‐acacia (Acacia drepanolobium) on three mega‐herbivore browsers: the Maasai giraffe (Giraffa camelopardalis tippelskirchi), the reticulated giraffe (Giraffa c. reticulata) and the black rhino (Diceros bicornis). Giraffes are abundant and wide‐ranging herbivores of the acacias, whereas black rhinos are localized and perennial herbivores of the acacias. Multiyear field studies comparing the ants’ aggressive behaviour and browsing by mega‐herbivores suggested differences between the tending abilities of the primary ant species inhabiting A. drepanolobium. Trees occupied by the aggressive ant species C. mimosae had significantly less browsing by giraffes and black rhino than trees occupied by other ant species. The results of this study provide evidence that ant‐mutualists on African acacias can serve as deterrents to mega‐herbivores and that different ant species vary in their tending abilities.     

Isolation and characterization of microsatellite markers from the acacia-ant Crematogaster mimosae

We describe 10 microsatellite loci developed from Crematogaster mimosae, an ant species that nests mutualistically in Acacia drepanolobium trees in east Africa. Polymorphism ranged from 4 to 16 alleles per locus (mean = 7.3). Observed and expected heterozygosities ranged from 0.485 to 0.813 (mean 0.626), and from 0.502 to 0.894 (mean 0.674), respectively. These markers will foster studies of the population structure, colony structure, and reproductive strategies of these ants.     

Estimation of dispersal distances of the obligately plant‐associated ant Crematogaster decamera

1. In obligate symbioses with horizontal transmission, the population dynamics of the partner organisms are highly interdependent. Host population size limits symbiont number, and distribution of partners is restricted by the presence and thus dispersal abilities of their respective partner. The Crematogaster decamera–Macaranga hypoleuca ant–plant symbiosis is obligate for both partners. Host survival depends on colonisation by its ant partner while foundress queens require hosts for colony establishment. 2. An experimental approach and population genetic analyses were combined to estimate dispersal distances of foundresses in their natural habitat in a Bornean primary rainforest. 3. Colonisation frequency was significantly negatively correlated with distance to potential reproductive colonies. Results were similar for seedlings at natural densities as well as for seedlings brought out in the area experimentally. Population genetic analysis revealed significant population differentiation with an F_ST of 0.041 among foundresses (n = 157) located at maximum 2280 m apart. In genetic spatial autocorrelation, genotypes of foundresses were significantly more similar than expected at random below 550 m and less similar above 620 m. Direct estimation of dispersal distances by pedigree analysis yielded an average dispersal distance of 468 m (maximum 1103 m). 4. For ants that disperse on the wing, genetic differentiation at such small spatial scales is unusual. The specific nesting requirements of the queens and the necessity for queens to find a host quickly could lead to colonisation of the first suitable seedling encountered, promoting short dispersal distances. Nonetheless, dispersal distances of C. decamera queens may vary with habitat or host spatial distribution.     

The effect size of aphid‐tending ants in an agricultural tri‐trophic system

Most studies regarding ant–aphid interactions focus only on the direct effects of ants on tended aphids and aphidophagous predators, or the indirect effects on the host plant. Studies evaluating the effects of aphid‐tending ants on more than one trophic level are rare and evaluate only the presence or absence of such effects. Here we assessed the effect sizes of ants in a tri‐trophic system (common bean plants, aphids and lacewing larvae). We tested if the presence of aphid‐tending ants has positive effects on aphid abundance and host‐plant production and negative effects on aphid predator abundance. We also hypothesized that aphid‐tending ants affect more intensely trophic levels that are more directly related to them (i.e., first aphids, then aphid predators and then host plants). We tested these hypotheses in field mesocosms experiments using the presence and absence of ants. We found that aphid‐tending ants have great positive effects on final aphid abundance. Ants also positively affected the number of seeds; however, it was not possible to measure the effect size for this trophic level. Furthermore, ants had negative effects on lacewing larvae only at first release. The effect size of ants was greater for aphids, followed by lacewing larvae, and with no effects on the number of seeds produced. Ants positively affect aphids and host‐plant production, probably by way of honeydew collection preventing the development of entomophagous/saprophytic fungi. On the other hand, ants negatively affect lacewing larvae by excluding them from the host plant. In natural systems, several ant species may attend aphids, differently affecting the organisms of the various trophic levels within the ant–aphid interaction, thereby obscuring the real effect size of ants. Assessing the effect size of aphid‐tending ants on the organisms involved in ant–aphid interactions provides more realistic information about the effects of this interaction on natural systems.     

Polymorphic microsatellite markers from the formicine ant Lasius (Dendrolasius) fuliginosus

Six polymorphic microsatellite loci were isolated and characterized from the temporary social parasitic ant Lasius fuliginosus by a highly efficient enrichment procedure. Observed allele numbers ranged from three to 20 per locus, whereby four out of the six tested loci had more than 10 alleles and showed both observed and expected heterozygosities greater than 70%. For each locus we present suitable primer sequences. With these microsatellite markers we will be able to reveal colony and population structure of L. fuliginosus.     

Thorn‐dwelling ants provide antiherbivore defence for camelthorn trees,Vachellia erioloba,in Namibia

Ants are widely employed by plants as an antiherbivore defence. A single host plant can associate with multiple, symbiotic ant species, although usually only a single ant species at a time. Different plant‐ant species may vary in the degree to which they defend their host plant. In Kenya, ant–acacia interactions are well studied, but less is known about systems elsewhere in Africa. A southern African species, Vachellia erioloba, is occupied by thorn‐dwelling ants from three different genera. Unusually, multiple colonies of all these ants simultaneously and stably inhabit trees. We investigated if the ants on V. erioloba (i) deter insect herbivores; (ii) differ in their effectiveness depending on the identity of the herbivore; and (iii) protect the tree against an important herbivore, the larvae of the lepidopteran Gonometa postica. We show that experimental exclusion of ants leads to greater levels of herbivory on trees. The ants inhabiting V. erioloba are an effective deterrent against hemipteran and coleopteran, but not lepidopteran herbivores. Defensive services do not vary among ant species, but only Crematogaster ants exhibit aggression towards G. postica. This highlights the potential of the V. erioloba–ant mutualism for studying ant–plant interactions that involve multiple, simultaneously resident thorn‐dwelling ant species.     

Mutualistic acacia ants exhibit reduced aggression and more frequent off‐tree movements near termite mounds

In many ant–plant mutualisms, ants establish colonies in hollow thorns, leaf pouches, or other specialized structures on their host plants, which they then defend from herbivores. Resource heterogeneity could affect the maintenance of these mutualisms if it leads to one or both partners altering their investment in the interaction. Such a phenomenon may be especially pertinent to the Acacia–ant mutualism found in East African savannas, where termite mounds have a profound effect on the spatial structuring of resources used by both plants and ants. Here, we examined whether the proximity to termite mounds of Acacia drepanolobium trees is associated with variation in the behavior of one of their ant associates, Crematogaster nigriceps. We found that ant colonies near termite mounds had decreased aggressive responses to simulated herbivory as well as increased off‐tree movement. We hypothesize that these changes are the result of resident ant colonies near termite mounds shifting investment from defense of their host plant to foraging for nearby resources.     

Facilitation promotes invasions in plant‐associated microbial communities

While several studies have established a positive correlation between community diversity and invasion resistance, it is less clear how species interactions within resident communities shape this process. Here, we experimentally tested how antagonistic and facilitative pairwise interactions within resident model microbial communities predict invasion by the plant–pathogenic bacterium Ralstonia solanacearum. We found that facilitative resident community interactions promoted and antagonistic interactions suppressed invasions both in the lab and in the tomato plant rhizosphere. Crucially, pairwise interactions reliably explained observed invasion outcomes also in multispecies communities, and mechanistically, this was linked to direct inhibition of the invader by antagonistic communities (antibiosis), and to a lesser degree by resource competition between members of the resident community and the invader. Together, our findings suggest that the type and strength of pairwise interactions can reliably predict the outcome of invasions in more complex multispecies communities.     

Indirect mutualism: ants protect fig seeds and pollen dispersers from parasites

1. Mutualisms are ubiquitous and ecologically important, but may be particularly vulnerable to exploitation by species outside of the mutualism owing to a combination of an attractive reward and potentially limited defence options. For some mutualisms, ants can offer dynamic and relatively selective protection against herbivores and parasites. 2. The mutualism between fig trees and their pollinating wasps, a keystone mutualism in tropical forests, is particularly well suited for ant protection because pollinators are protected inside hollow inflorescences but parasites are exposed on the outside. 3. In the present study, it was shown that the presence of ants provides a fitness benefit for both the pollinators and the hosting fig tree. The presence of ants (i) reduced abortions of developing figs, (ii) reduced herbivory of figs, and (iii) reduced parasitic wasp loads, resulting in more pollinators and more seeds in ant‐protected figs. Even when taking costs such as ant predation on emerging pollinators into account, the total fitness increase of hosting ants was threefold for the tree and fivefold for the pollinators. 4. It was further shown that the seemingly most vulnerable parasitic wasps, of the genus Idarnes, have a specific behaviour that allows them to evade ant attack while continuing to oviposit. 5. Ants were present on 79% of surveyed Panamanian fig trees. Together with previous studies from the Old World, the results found here imply that ants are both powerful and common protectors of the fig mutualism worldwide.     

Intraspecific variation in herbivore‐induced plant volatiles influences the spatial range of plant–parasitoid interactions

Chemical information influences the behaviour of many animals, thus affecting species interactions. Many animals forage for resources that are heterogeneously distributed in space and time, and have evolved foraging behaviour that utilizes information related to these resources. Herbivore‐induced plant volatiles (HIPVs), emitted by plants upon herbivore attack, provide information on herbivory to various animal species, including parasitoids. Little is known about the spatial scale at which plants attract parasitoids via HIPVs under field conditions and how intraspecific variation in HIPV emission affects this spatial scale. Here, we investigated the spatial scale of parasitoid attraction to two cabbage accessions that differ in relative preference of the parasitoid Cotesia glomerata when plants were damaged by Pieris brassicae caterpillars. Parasitoids were released in a field experiment with plants at distances of up to 60 m from the release site using intervals between plants of 10 or 20 m to assess parasitism rates over time and distance. Additionally, we observed host‐location behaviour of parasitoids in detail in a semi‐field tent experiment with plant spacing up to 8 m. Plant accession strongly affected successful host location in field set‐ups with 10 or 20 m intervals between plants. In the semi‐field set‐up, plant finding success by parasitoids decreased with increasing plant spacing, differed between plant accessions, and was higher for host‐infested plants than for uninfested plants. We demonstrate that parasitoids can be attracted to herbivore‐infested plants over large distances (10 m or 20 m) in the field, and that stronger plant attractiveness via HIPVs increases this distance (up to at least 20 m). Our study indicates that variation in plant traits can affect attraction distance, movement patterns of parasitoids, and ultimately spatial patterns of plant–insect interactions. It is therefore important to consider plant‐trait variation in HIPVs when studying animal foraging behaviour and multi‐trophic interactions in a spatial context.     

Human disturbance promotes herbivory by leaf‐cutting ants in the Caatinga dry forest

Anthropogenic disturbances are known to modify plant–animal interactions such as those involving the leaf‐cutting ants, the most voracious and proliferating herbivore across human‐modified landscapes in the Neotropics. Here, we evaluate the effect of chronic anthropogenic disturbance (e.g., firewood collection, livestock grazing) and vegetation seasonality on foraging area, foliage availability in the foraging area, leaf consumption and herbivory rate of the leaf‐cutting ant Atta opaciceps in the semiarid Caatinga, a mosaic of dry forest and scrub vegetation in northeast Brazil. Contrary to our initial expectation, the foraging area was not affected by either disturbance intensity or the interaction between season and disturbance intensity. However, leaf consumption and herbivory rate were higher in more disturbed areas. We also found a strong effect of seasonality, with higher leaf consumption and herbivory rate in the dry season. Our results suggest that the foraging ecology of leaf‐cutting ants is modulated by human disturbance and seasonality as these two drivers affect the spectrum and the amount of resources available for these ants in the Caatinga. Despite the low productivity of Caatinga vegetation, the annual rates of biomass consumption by A. opaciceps are similar to those reported from other leaf‐cutting ants in rain forests and savannas. This is made possible by maintaining high foraging activity even in the peak of the dry season and taking benefit from any resource available, including low‐quality items. Such compensation highlights the adaptive capacity of LCA to persist or even proliferate in human‐modified landscapes from dry to rain forests.     

High‐throughput physiological phenotyping and screening system for the characterization of plant–environment interactions

We present a simple and effective high‐throughput experimental platform for simultaneous and continuous monitoring of water relations in the soil–plant–atmosphere continuum of numerous plants under dynamic environmental conditions. This system provides a simultaneously measured, detailed physiological response profile for each plant in the array, over time periods ranging from a few minutes to the entire growing season, under normal, stress and recovery conditions and at any phenological stage. Three probes for each pot in the array and a specially designed algorithm enable detailed water‐relations characterization of whole‐plant transpiration, biomass gain, stomatal conductance and root flux. They also enable quantitative calculation of the whole plant water‐use efficiency and relative water content at high resolution under dynamic soil and atmospheric conditions. The system has no moving parts and can fit into many growing environments. A screening of 65 introgression lines of a wild tomato species (Solanum pennellii) crossed with cultivated tomato (S. lycopersicum), using our system and conventional gas‐exchange tools, confirmed the accuracy of the system as well as its diagnostic capabilities. The use of this high‐throughput diagnostic screening method is discussed in light of the gaps in our understanding of the genetic regulation of whole‐plant performance, particularly under abiotic stress.     

Polymorphic microsatellite markers for the ant Plagiolepis pygmaea

Detailed studies on kin structure, mating patterns and dispersal in social insects require highly polymorphic markers, of which the most commonly used today are DNA microsatellites. Here we characterize 10 polymorphic microsatellite markers for the ant Plagiolepis pygmaea. We also investigated the within‐genus applicability of the markers on P. xene, a social parasite of the source species. In addition, we tested amplification of the markers in three species of the genera Formica and Lasius. Eight of the markers also amplified in P. xene and were polymorphic. Seven markers amplified in at least one other formicine ant.     

Characterization of microsatellite markers from the gastropod genus Melongena

Eight microsatellite loci were isolated and characterized from the Florida crown conch (Melongena spp.). Approximately 500 individuals from 20 populations encompassing all known Melongena spp. groups in Florida and Alabama were genotyped at all loci. High levels of variation were found with eight to 28 alleles per locus and observed per locus heterozygosity ranging from 0.148 to 0.779 (mean 0.624). One locus, Mco5, was monomorphic in more than half of the populations. These loci can provide useful information for a variety of studies ranging from parentage to population‐level analyses of the Florida crown conch.     

Microsatellite markers for testing host plant‐related population differentiation in the moth genus Yponomeuta

Nine microsatellite primers were developed for Yponomeuta padellus (Lepidoptera: Yponomeutidae) and tested for their applicability in analysing genetic population structure. Eight of the nine loci were highly polymorphic with on average 11.4 alleles. Cross‐species amplification of the nine primer pairs was tested in five other moth species. Primer pairs amplified in Y. cagnagellus, Y. malinellus, Y. evonymellus, and Y. rorellus but not in Y. sedellus and Plutella xylostella.     

Trait‐mediated indirect interactions: Moose browsing increases sawfly fecundity through plant‐induced responses

相似文献   

A procedure for the transient expression of genes by agroinfiltration above the permissive threshold to study temperature‐sensitive processes in plant–pathogen interactions

Localized expression of genes in plants from T‐DNAs delivered into plant cells by Agrobacterium tumefaciens is an important tool in plant research. The technique, known as agroinfiltration, provides fast, efficient ways to transiently express or silence a desired gene without resorting to the time‐consuming, challenging stable transformation of the host, the use of less efficient means of delivery, such as bombardment, or the use of viral vectors, which multiply and spread within the host causing physiological alterations themselves. A drawback of the agroinfiltration technique is its temperature dependence: early studies have shown that temperatures above 29 °C are nonpermissive to tumour induction by the bacterium as a result of failure in pilus formation. However, research in plant sciences is interested in studying processes at these temperatures, above the 25 °C experimental standard, common to many host–environment and host–pathogen interactions in nature, and agroinfiltration is an excellent tool for this purpose. Here, we measured the efficiency of agroinfiltration for the expression of reporter genes in plants from T‐DNAs at the nonpermissive temperature of 30 °C, either transiently or as part of viral amplicons, and envisaged procedures that allow and optimize its use for gene expression at this temperature. We applied this technical advance to assess the performance at 30 °C of two viral suppressors of silencing in agropatch assays [Potato virus Y helper component proteinase (HCPro) and Cucumber mosaic virus 2b protein] and, within the context of infection by a Potato virus X (PVX) vector, also assessed indirectly their effect on the overall response of the host Nicotiana benthamiana to the virus.     

Production of food bodies on the reproductive organs of myrmecophytic Macaranga species (Euphorbiaceae): effects on interactions with herbivores and pollinators

In protective ant–plant mutualisms, plants offer ants food (such as extrafloral nectar and/or food bodies) and ants protect plants from herbivores. However, ants often negatively affect plant reproduction by deterring pollinators. The aggressive protection that mutualistic ants provide to some myrmecophytes may enhance this negative effect in comparison to plant species that are facultatively protected by ants. Because little is known about the processes by which myrmecophytes are pollinated in the presence of ant guards, we examined ant interactions with herbivores and pollinators on plant reproductive organs. We examined eight myrmecophytic and three nonmyrmecophytic Macaranga species in Borneo. Most of the species studied are pollinated by thrips breeding in the inflorescences. Seven of eight myrmecophytic species produced food bodies on young inflorescences and/or immature fruits. Food body production was associated with increased ant abundance on inflorescences of the three species observed. The exclusion of ants from inflorescences of one species without food rewards resulted in increased herbivory damage. In contrast, ant exclusion had no effect on the number of pollinator thrips. The absence of thrips pollinator deterrence by ants may be due to the presence of protective bracteoles that limit ants, but not pollinators, from accessing flowers. This unique mechanism may account for simultaneous thrips pollination and ant defense of inflorescences.     

Characterization of 24 microsatellite markers in 11 species of fire ants in the genus Solenopsis (Hymenoptera: Formicidae)

The social parasite ant Solenopsis daguerrei infests colonies of several mound-building fire ant species. Twenty-four microsatellite markers were isolated from a repeat-enriched genomic library of S. daguerrei. Eleven loci were polymorphic in this ant with two to six alleles per locus. Expected heterozygosity ranged from 0.0222 to 0.7940 among loci. Most microsatellites amplified successfully across the 11 Solenopsis species tested and will be useful for evolutionary genetic studies in this diverse ant group.