Abstract: The concept of intraguild predation (IGP) appeared in 1987â1989 to describe trophic interactions within a guild of arthropods inhabiting a sand dune desert: consumers B prey on consumers A and both of them prey on a common resource. Theory predicts that the two types of consumers should only coexist if consumer A is more efficient in the conversion of the common resource than B. As a consequence, this resource is more abundant in the presence than in the absence of intraguild predators. Such a theoretical prediction probably explains the vivid interest shown by ecologists involved in biological control for IGP. It is therefore not surprising that many papers report on IGP among natural enemies of aphids. A close examination of these reported cases indicates that they rarely fulfil the theoretical requirements for IGP. That is, guilds of aphidophagous insects are rarely the theatre of IGP but frequently of interspecific predation. This is confirmed by experimental assessment of the cost of attacking and eating intraguild prey instead of extraguild in ladybird beetles.
Abstract: So far, only a few studies have explicitly investigated the consequences of admixture for the adaptative potential of invasive populations. We addressed this question in the invasive ladybird Harmonia axyridis. After decades of use as a biological control agent against aphids in Europe and North America, H. axyridis recently became invasive in four continents and has now spread widely in Europe. Despite this invasion, a flightless strain is still sold as a biological control agent in Europe. However, crosses between flightless and invasive individuals yield individuals able to fly, as the flightless phenotype is caused by a single recessive mutation. We investigated the potential consequences of admixture between invasive and flightless biological control individuals on the invasion in France. We used three complementary approaches: (i) population genetics, (ii) a mate-choice experiment, and (iii) a quantitative genetics experiment. The invasive French population and the biological control strain showed substantial genetic differentiation, but there are no reproductive barriers between the two. Hybrids displayed a shorter development time, a larger size and a higher genetic variance for survival in starvation conditions than invasive individuals. We discuss the potential consequences of our results with respect to the invasion of H. axyridis in Europe.
Abstract: Environmental constraints can be determinant key factors conditioning predator
life history evolution. Prey seems to have conditioned life history evolution in their
ladybird predator, with the predators of aphids apparently presenting faster development,
greater fecundity and shorter longevity than species preying on coccids. However a rigorous
comparison has never been done. We hypothesize that aphids and coccids differ by
their developmental rate, abundance, and distribution in the field, which act as ecological
constraints promoting life history evolution in ladybird predators. Field data reveal that
aphids are ephemeral resources available in the form of large colonies randomly distributed
in the habitat whereas coccids form smaller colonies that tend to be aggregated in space
and available for longer periods. A comparison in laboratory conditions of two predatory
species belonging to the tribe Scymnini (Coleoptera: Coccinellidae) show that the aphidophagous
species lives at a faster pace than the coccidophagous: it develops faster,
matures earlier, is more fecund, has a shorter reproductive life-span and allocate proportionally
more fat in its gonads relative to soma. This indicates that the life histories of
aphidophagous and coccidophagous ladybird predators appear to have evolved in response
to particular patterns of prey availability in time and space. Under the light of these results,
the existence of a slow-fast continuum in ladybirds is briefly addressed.
Abstract: We review the chemical ecology of the ladybird beetle Harmonia axyridis from the perspective of its
invasiveness and the deleterious effects it exerts in the regions it has colonised. We outline the nature and quantification of its chemical defence, and discuss the protection this provides against natural enemies, particularly intraguild predators. We consider the role of infochemicals in location of prey, intraspecific communication and intraguild interactions. We also discuss the role of prey allelochemicals in relation to H. axyridis extreme dietary generalism. Harmonia axyridis poses a number of practical problems for human health and well-being, including âladybug taintâ wine contamination and problems resulting from large aggregations overwintering in buildings. We consider chemical insights into these issues and, in particular, how attractants and repellents might help manage H. axyridis populations through a pushâpull strategy. We conclude by discussing future perspectives for research.
Abstract: A variety of arthropods, particularly insects, have developed myrmecophilous interactions with ants to gain access to resources and/or for protection. Among these myrmecophiles, only a few examples have been documented in the Coccinellidae, most of them involving species able to feed on ant-tended Hemiptera. We report here a new case of obligate myrmecophily in the coccinellid Diomus thoracicus. Larvae are invariably and exclusively found in the nests of the ant Wasmannia auropunctata and seem to rely on ant brood as their only food source. Not only do ant workers show no aggressiveness toward the D. thoracicus larvae in their behavioral interactions at the colonial level, but also at the species level; while coccinellid adults are always attacked. The integration of the larvae inside of the ant nests is based on their chemical mimicry of the host's cuticular cues. Therefore, given the presence of the D. thoracicus larvae inside of the ant's nest, their predation on Wasmannia brood and their chemical mimicry, this species can be considered a specific parasite of W. auropunctata. Overall, this new case of myrmecophily not only specifically involves a highly invasive ant species, but also provides insights into the evolution of myrmecophily and myrmecophagy in coccinellids.
Abstract: Faced with an ephemeral prey, aphidophagous ladybirds rely on the hydrocarbons present in the tracks of their larvae to choose an unoccupied patch for egg laying. Although both conspecific and heterospecific larval tracks might deter females from oviposition, the response to the later is often less striking. Several explanations have been suggested to account for this. In this paper we tested the phylogeny hypothesis, which predicts that the chemical composition of the tracks of closely related species of ladybirds will be more similar to one another than to those of more distantly related species. Qualitative and quantitative information on the chemical nature of the larval tracks and a molecular phylogeny of seven species belonging to three different genera are provided, and the congruence between these two sets of results assessed. The results confirm the phylogeny hypothesis and infer a gradual mode of evolution of these infochemicals.
Abstract: The Coccinellidae (ladybirds) is a highly speciose family of the Coleoptera. Ladybirds are well known because of their use as biocontrol agents, and are the subject of many ecological studies. However, little is known about phylogenetic relationships of the Coccinellidae, and a precise evolutionary framework is needed for the family. This paper provides the first phylogenetic reconstruction of the relationships within the Coccinellidae based on analysis of five genes: the 18S and 28S rRNA nuclear genes and the mitochondrial 12S, 16S rRNA and cytochrome oxidase subunit I (COI) genes. The phylogenetic relationships of 67 terminal taxa, representative of all the subfamilies of the Coccinellidae (61 species, 37 genera), and relevant outgroups, were reconstructed using multiple approaches, including Bayesian inference with partitioning strategies. The recovered phylogenies are congruent and show that the Coccinellinae is monophyletic but the Coccidulinae, Epilachninae, Scymninae and Chilocorinae are paraphyletic. The tribe Chilocorini is identified as the sister-group of the Coccinellinae for the first time.
Abstract: Intraspecific and interspecific predation of eggs is a well documented phenomenon amongst aphidophagous coccinellids. The invasive species Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is known to be a top intraguild predator and reported to attack the eggs of many coccinellid species both in a laboratory setting and in the wild. A previous laboratory study highlighted that while many species' eggs were highly palatable to H. axyridis, the eggs of Calvia quatuordecimguttata (Linnaeus) (Coleoptera: Coccinellidae) appeared to be extremely well protected from attack. Here we present the results of behavioural experiments testing the hypothesis that substances on the egg surface are responsible for this protection, and report preliminary results of GC-MS analysis of these compounds. When the coatings of C. quatuordecimguttata eggs were removed using hexane, they became significantly more susceptible to predation by neonate H. axyridis larvae. However, their overall palatability was not affected, in that complete consumption was never or rarely observed. This suggests that the surface compounds are a true indicator of unpalatability in this species. The effect of hexane-washing on already palatable conspecific eggs was also analysed but had no significant effect on the susceptibility of eggs to cannibalism. We conclude that the eggs of at least one European species are effectively protected by surface deterrents from intraguild predation by H. axyridis. This effect might be due to both the diversity and abundance of hydrocarbons present within the egg coating, the presence of alkenes and/or the presence of patches of a red substance on the eggs' surface, which is thought to belong to the acid group. In conjunction with data on the susceptibility of other immature stages of C. quatuordecimguttata, this finding may indicate a decreased risk of the species falling victim to invasive H. axyridis, despite their coincident habitat ranges.
Abstract: Aphid colonies can reach high levels of abundance but last for short periods of time. The larvae of aphidophagous ladybirds (Coleoptera: Coccinellidae) that feed on these colonies might therefore suffer from starvation, which favours the occurrence of cannibalism and intraguild predation. Thus, the assessment of patch quality becomes crucial and it has been shown that female ladybirds refrain from laying eggs in the presence of an oviposition deterring semiochemical deposited by their larvae. Adalia bipunctata (L.), Adalia decempunctata (L.) and Coccinella septempunctata L. are 3 sympatric species of ladybirds, which can co-occur in aphid colonies. As a consequence, their eggs and larvae are under threat, not only from cannibalism but also intraguild predation. Females should, therefore, also use the tracks deposited by heterospecific larvae to assess the quality of aphid colonies as oviposition sites. The expectation is that: 1- the strength of the reaction to each other's larval tracks should be correlated with percentage habitat overlap and that 2- the reaction to conspecific larval tracks should be stronger than to heterospecific tracks. In order to test these hypotheses, females' oviposition behaviour was analysed and a chemical analysis of the tracks of their larvae undertaken. The results show that oviposition behaviour is not related to habitat overlap. Both species of Adalia react to tracks of their own larvae and those of C. septempunctata, but A. decempunctata reacted more strongly than A. bipunctata. C. septempunctata reacted very slightly to its own tracks but not to those of either species of Adalia. The larval tracks are mainly composed of alkanes. Those of the two species of Adalia are qualitatively 100% similar and 60% so when the quantitative results are compared. They are, however, only 24-29% similar to those of Coccinella septempunctata.
Abstract: The prey of coccidophagous ladybird beetles has a slower rate of development and is less mobile than that of aphidophagous ladybirds. These differences are paralleled by a suite of characters suggesting that coccidophagous species live at a slower pace than aphidophagous species. Data in the literature tend to indicate that coccidophagous ladybirds live longer and have a lower fecundity than aphidophagous species. Thus the expectation is that coccidophagous species allocate proportionally less resources to their gonads than aphidophagous species. The reproductive investment in C. montrouzieri and A. bipunctata support this prediction. The fat in gonads represents 27.4 % of the total body fat in C. montrouzieri and 37.1 % in A. bipunctata.
Abstract: Mills (1982) formulated the satiation hypothesis in order to explain why ladybirds are generally more effective in the biological control of coccids than of aphids: aphidophagous ladybirds are supposedly less efficient because they become more rapidly satiated than coccidophagous ladybirds. If this is true, the former should spend less time eating than the latter. This hypothesis is tested in this study using the coccidophagous Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) and the aphidophagous Adalia bipunctata (L.) (Coleoptera: Coccinellidae). Contrary to Mills' (1982) prediction the coccidophagous ladybird did not feed continuously and even spent less time feeding than the aphidophagous ladybird. Furthermore, the gut capacity of C. montrouzieri is smaller than that of A. bipunctata.
Abstract: Coccinellids were sampled in 88 citrus groves from the centre/south of continental
Portugal. Analysis of distribution were performed by the usual indices but also with the
help of a new method - SADIE.
38 species were identified, 36 of which are predators. Five coccinellids seem to
have aggregated distributions; UTM maps of those species distributions are presented.
Among these five, Nephus reunioni Fiirsch and Nephus includens (Kirsch) are the more
abundant. Previous studies about these two coccinellids distributions are confirmed: N.
reunioni is limited to a region of about 80 Km diameter around Lisbon while N. includens
appears only in Algarve.
Coccidophagous species and a group of Scymnus sp. and Nephus sp., with unknown
food preferences in citrus, are the most important in terms of richness and abundance.
Abstract: Integrated Pest Management programmes in Portugal pay main attention to coccids.
The study of coccinellids for the biological control of those pests was undertaken.
This paper aimed firstly to determine which coccidophagous ladybirds are more
likely to control coccids by examining Dominance, Constancy and Persistence along
the year. A second goal was to shed some light on the feeding regime of several species
of the Scymnini tribe.
Eight coccidophagous ladybirds have been observed to have a strong presence in
Portuguese citrus groves. They correspond to species regularly considered as important
for the biological control of coccids in other Mediterranean countries.
Five species of the Scymnus genus are also very important in the sampled orchards.
Though usually considered as aphidophagous, their abundance is correlated to the appearance
of coccinellids which are predators of coccids.
A first large scale phenology of the most important ladybird beetles in citrus
orchards is provided which can help to schedule chemical interventions.
Abstract: Dysaphis plantaginea is one of the major pests of apple trees in Western Europe. It is usually recommended that apple trees be sprayed with insecticide as soon as the first aphid is recorded. Thus, orchards are sprayed with insecticide almost every year although aphids rarely remain abundant for several successive growing seasons. Consequently signs of resistance to pesticides in the aphid have already been recorded. Therefore, fruit growers are willing to become less dependent on insecticides and to adopt an integrated pest management approach. One of our aims is to understand the population dynamics of D. plantaginea in order to develop a forecasting model. The factors associated with seasonal increases in aphid abundance are known for several pest species and have been used to develop such models. As the catches of aphids by suction traps are well correlated with aphid abundance on adjacent crops, data from the Agraphid network have been used to search for patterns in the population dynamics of D. plantaginea. Analysis of the yearly variations in D. plantaginea numbers indicates density dependence.
