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Oviposition, ovicide and larval competition in granivorous insects
... Several important variables have been identified, including host availability, dispersion and, especially, host size, all of which can influence the frequency of encounters (Godfray, 1987;Joshi & Thompson, 1995;Lane & Mills, 2003;Vamosi et al., 2011). When individual hosts are large relative to the resource needs of a single larva, avoidance or tolerance of competitors may maximize larval fitness, but aggressive behaviour may be favoured in very small hosts, where direct encounters are unavoidable (Smith & Lessells, 1985). ...
... Theoretical analyses (Smith & Lessells, 1985;Tuda & Iwasa, 1998), population comparisons (Messina, 1991a;Guedes et al., 2007) and selection experiments (Tuda, 1998;Messina, 2004) have suggested that features of the host species, particularly seed size, account for much of the differences in larval competitiveness among populations. In large seeds, which provide enough resources to support development of multiple larvae, avoidance and tolerance strategies appear to maximize individual fitness, whereas aggressive or contest behaviour is favoured in small seeds, within which co-occurring larvae are bound to come into contact (Smith, 1990). ...
... These analyses have shown that female-biased sex ratios and single-sex broods (Rosenheim, 1993), reduced mobility in aggressive genotypes (Pexton & Mayhew, 2001;Brodeur & Boivin, 2004), Allee effects (where the presence of conspecifics improves resource quality; Khafagi & Hegazi, 2008) and reduced host availability (Hoffmeister et al., 2005) all reduce the likelihood that an aggressive genotype will displace the tolerant genotype in a population. Similar theory has been used to examine when we expect to observe interference vs. exploitative strategies in seed beetles (Smith & Lessells, 1985;Toquenaga et al., 1994;Tuda & Iwasa, 1998). Because most C. maculatus populations exhibit larval tolerance within seeds (Guedes et al., 2007), and both this study and a previous one (Messina, 2004) have shown that greater tolerance readily evolves in only a few dozen generations, there may be greater constraints associated with evolving an increase in aggression than in its decay (but see Tuda, 1998). ...
Resource competition is frequently strong among parasites that feed within small discrete resource patches, such as seeds or fruits. The properties of a host can influence the behavioral, morphological, and life history traits of associated parasites, including traits that mediate competition within the host. For seed parasites, host size may be an especially important determinant of competitive ability. Using the seed beetle, Callosobruchus maculatus, we performed replicated, reciprocal host shifts to examine the role of seed size in determining larval competitiveness and associated traits. Populations ancestrally associated with either a small host (mung bean) or a large one (cowpea) were switched to each other's host for 36 generations. Compared to control lines (those remaining on the ancestral host), lines switched from the small host to the large host evolved greater tolerance of co-occurring larvae within seeds (indicated by an increase in the frequency of small seeds yielding two adults), smaller egg size, and higher fecundity. Each change occurred in the direction predicted by the traits of populations already adapted to cowpea. However, we did not observe the expected decline in adult mass following the shift to the larger host. Moreover, lines switched from the large host (cowpea) to the small one (mung bean) did not evolve the predicted increase in larval competitiveness or egg size, but did exhibit the predicted increase in body mass. Our results thus provide mixed support for the hypothesis that host size determines the evolution of competition-related traits of seed beetles; evolutionary responses to the two host shifts were consistent among replicate lines but the evolution of larval competition was asymmetric, with larval competitiveness evolving as predicted in one direction of host shift, but not the reverse. Nevertheless, our results indicate that switching hosts is sufficient to produce repeatable and rapid, but asymmetric, changes in the competition strategy and fitness-related traits of insect populations.
... Egg-laying decisions are rather plastic among some insect species, as the cowpea beetle Callosobruchus maculatus that rely in chemical and vibration cues to avoid overcrowding legume seeds (e.g., Messina and Renwick 1985;Messina et al. 1987;Ignacimuthu et al. 2000;Guedes and Yack 2016). However, other species do not exhibit such plasticity and more rigid patterns of isolated or aggregated egg distribution take place (e.g., Smith and Lessells 1985;Stejskal and Kučerová 1996;Nufio and Papaj 2001;Danho and Haubruge 2003a), further reinforcing the importance of larval competition with its processes and outcomes shaping insect life history (Smith 1991;Guedes et al. 2010). The recognition of such distribution patterns is also important in designing sampling plans for pest species to allow suitable estimates of population density (Taylor 1984;Pedigo and Zeiss 1996;Young and Young 1998). ...
... The recognition of such distribution patterns is also important in designing sampling plans for pest species to allow suitable estimates of population density (Taylor 1984;Pedigo and Zeiss 1996;Young and Young 1998). Larval competition may be either scramble or contest depending on the process involved (Nicholson 1954;De Jong 1976;Smith and Lessells 1985). While accommodation of all competitors takes place within the resource patch in the process of scramble competition, leading to reduced survival and resource gain with increasing density of competition, contest competition implies direct interference among competing individuals with prevalence of a single or few individuals in a patch (De Jong 1976;Smith 1991;Guedes et al. 2007Guedes et al. , 2010. ...
... Internally feeding larvae of stored grain beetles are important pests whose development is constrained within a mother-selected grain. Intensive competition takes place among larvae motivating the use of these insect species, mainly legume beetles, for studies of larva competition (Smith and Lessells 1985;Smith 1990;Guedes et al. 2007;Oliveira et al. 2015). Nonetheless, grain weevils were also object of more recent attention in which not only the outcome, but also the behavioral process of larval competition was investigated and contest competition with direct larvae interference and cannibalism takes place, as followed with digital X-ray imaging (Guedes et al. 2010). ...
Resource limitation is an important determinant of life history and behavior while mediating competition and reproduction among organisms. Discreet and closed systems such as grain kernels and seeds impose drastic restrictions to grain beetles that spend their immature stages within a single kernel selected by their mother. This is the case of internally feeding stored grain beetles, such as the grain weevils. Female egg-laying decisions and larval competition largely determine resource limitation for such insects where clustered egg distribution and contest competition with larval interference and cannibalism take place. As the clustered eggs within a grain lead to larval competition and conspecific weevil larvae face each other off during development allowing the emergence of one or two larvae per kernel, we hypothesized that such competition and consequent cannibalism will have fitness consequences for the competing individuals and their offspring. Thus, larvae of the granary weevil (Sitophilus granarius L.) and the maize weevil (Sitophilus zeamais Motsch.) were subjected to larval competition with cannibalism, and lack of it, to assess the potential fitness consequence of cannibalism on these non-carnivorous pest species of stored grains. Larval cannibalism reduced developmental time of maize weevil, but not of granary weevil. However, such condition led to heavier adult weevils of both species exhibiting higher reproductive output generating more and better quality progeny than non-cannibal weevils. These findings indicate direct nutritional benefits of cannibalism to grain weevils favoring their status of key pest species of stored cereal grains.
... Much attention has been 63 devoted to the processes and outcomes of intra--specific competition in seed--feeding insects. 64 This is usually accomplished by analyzing survival curves in controlled experiments, from 65 which one can infer the process of competition (Smith & Lessels, 1985). However, such 66 studies usually miss the opportunity to observe the morphology and behavior mediating the 67 competitive interaction, and different behavioral processes could result in the same 68 outcome (Smith & Lessels, 1985). ...
... 64 This is usually accomplished by analyzing survival curves in controlled experiments, from 65 which one can infer the process of competition (Smith & Lessels, 1985). However, such 66 studies usually miss the opportunity to observe the morphology and behavior mediating the 67 competitive interaction, and different behavioral processes could result in the same 68 outcome (Smith & Lessels, 1985). Oliveira). ...
Weevils are one of the largest groups of living organisms, with more than 60,000 species feeding mostly on plants. With only one exception, their described larvae are typical plant-feeders, with mouthparts adapted to chewing plant material. Here we describe the second case of a weevil with early-instar larvae adapted to killing conspecifics. We have studied the life history of Anchylorhynchus eriospathae G. G. Bondar, 1943, a species whose immatures feed internally on palm flowers and fruits. We provide detailed descriptions of all immature stages, including the extremely modified first-instar larva. Unlike other weevils and later instars, this stage exhibits a flat body with very long ventropedal lobe setae, a large and prognathous head with a gula, and falciform mandibles, each with a serrate retinaculum, that are used to fight with and eventually kill other first-instar larvae. We also provide biological notes on all stages and the results of behavioral tests that showed that larval aggression occurs only among early life stages. Finally we show that adult size is highly dependent on timing of oviposition. This specialized killer first instar probably evolved independently from the one other case known in weevils (in Revena rubiginosa ) . Interestingly, both lineages inhabit the same hosts, raising the possibility that both intra- and inter-specific competition shaped those phenotypes. Given the scarcity of knowledge on early larval stages of concealed insect herbivores, it is possible that our findings represent an instance of a much broader phenomenon. Our observations also allowed us to conclude that Anchylorhynchus eriospathae and A. hatschbachi G. G. Bondar, 1943 are actually the same species, which we synonymize here by considering the latter as a junior synonym (new synonymy).
... For example, insects, mainly coleopterans, are responsible for huge grain losses of up to 57% in Africa (Kumar and Kalita 2017). Several stored-product coleopterous species co-exist in storage facilities and consequently compete for the same food resources (Smith and Lessells, 1985;Smith, 1990Smith, , 1991Athanassiou et al., 2003Athanassiou et al., , 2005Athanassiou et al., , 2011Athanassiou et al., , 2017aKavallieratos et al., 2017b). Although competition is considered a serious issue in storage ecosystem (Smith and Lessells, 1985;Smith, 1990Smith, , 1991Kavallieratos et al., 4 2017b) there is a gap of knowledge regarding interspecific competition. ...
... Several stored-product coleopterous species co-exist in storage facilities and consequently compete for the same food resources (Smith and Lessells, 1985;Smith, 1990Smith, , 1991Athanassiou et al., 2003Athanassiou et al., , 2005Athanassiou et al., , 2011Athanassiou et al., , 2017aKavallieratos et al., 2017b). Although competition is considered a serious issue in storage ecosystem (Smith and Lessells, 1985;Smith, 1990Smith, , 1991Kavallieratos et al., 4 2017b) there is a gap of knowledge regarding interspecific competition. The significance of interspecific competition in stored-product insect pests has recently been highlighted, demonstrating its effect in community structure (Athanassiou et al. 2014Kavallieratos et al. 2017b). ...
The premises of stored agricultural products and food consists of a complex ecosystem in which several pests can seriously affect the quality and quantity of the products. In this study we utilize a 4-level hierarchical linear multilevel model in order to assess the effect of temperature, relative humidity (RH) and interspecific competition on the population size and damage potential of the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae) and the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae). As RH was increased, we observed higher percentage of live insects, while increased levels of temperature significantly decreased the percentage of live insects. The combination of R. dominica and P. truncatus lead to reduction of the percentages of live insects in comparison to single species treatments. However, P. truncatus is more damaging than R. dominica in maize, based on the proportion of damaged kernels which were infested by each insect species. We expect our results to have bearing in the management of these species.
... Nonetheless, these three species explore different ecological niches within the same habitat with S. oryzae laying eggs within the grain kernel, while R. dominica lay eggs outside the grain kernel and the larvae penetrates the grain in which it develops, both as internal feeders, in contrast with T. granarium whose larvae are longlived external feeders (Aitken, 1975;Hill, 2003); such distinct life histories allow for potential resource partition allowing co-existence of at least two species. Regardless, competition is recognized as an important phenomenon among grain beetles driving their natural selection and population regulation (Smith and Lessells, 1985;Smith, 1990Smith, , 1991, and has been tested in few species so far, but never in the case of T. granarium (Nicholson, 1954;De Jong, 1976;Connell, 1983;Krebs, 2002). Moreover, despite the considerable number of studies that are available for competition in stored-product beetles, such studies were usually focused in intraspecific competition, by conducting parallel experiments of life table characteristics of single species (Smith and Lessells, 1985;Smith, 1990;Horn, 1997;Guedes et al., 2010;Oliveira et al., 2015), and not interspecific competition (i.e., simultaneous presence of different species in the same substrate). ...
... Regardless, competition is recognized as an important phenomenon among grain beetles driving their natural selection and population regulation (Smith and Lessells, 1985;Smith, 1990Smith, , 1991, and has been tested in few species so far, but never in the case of T. granarium (Nicholson, 1954;De Jong, 1976;Connell, 1983;Krebs, 2002). Moreover, despite the considerable number of studies that are available for competition in stored-product beetles, such studies were usually focused in intraspecific competition, by conducting parallel experiments of life table characteristics of single species (Smith and Lessells, 1985;Smith, 1990;Horn, 1997;Guedes et al., 2010;Oliveira et al., 2015), and not interspecific competition (i.e., simultaneous presence of different species in the same substrate). The outcome of this competition is apparently determined by several biotic and abiotic conditions, including temperature and type of commodity, but there is still inadequate information regarding the effect of these conditions in competition of T. granarium with other major stored-grain insects. ...
Local potential competitor species are important determinants of the invasibility of an environment even when widely recognized invasive species are concerned since it may compromise its establishment. Thus, the outcome of the direct competition among the invasive khapra beetle, Trogoderma granarium, and the cosmopolitan species lesser grain borer, Rhyzopertha dominica and rice weevil, Sitophilus oryzae, and thus the likelihood of establishment of T. granarium under their co-occurrence, was here explored in paddy rice and wheat, at temperatures between 25 and 35°C and through 200 days of storage. Insect infestations were higher in wheat rather than in paddy rice. Trogoderma granarium was unable to displace any of the competing species under two and three-species competition experiments retaining lower adult population than both local competitors at the lowest temperature level. Rhyzopertha dominica prevailed in paddy rice, while S. oryzae prevailed in wheat. Paradoxically, T. granarium adults retained low population growth but contributed more for the total frass production and grain loss, much more than that recorded for R. dominica. Nonetheless, T. granarium larvae exhibited high population numbers 130 days after the introduction of the parental individuals. At higher temperature levels (30 and 35°C) the numbers of T. granarium larvae were extremely high even after 65 days, while the numbers of the other two species rapidly declined. Interestingly, the simultaneous presence of R. dominica and S. oryzae was beneficial for the population growth of T. granarium. Consequently, T. granarium has the ability to outperform other primary stored-product insects at high temperatures, while its presence at low temperatures remains for long periods apparently unaffected by other co-occurring species. Hence, T. granarium, in wheat, is able to outcompete other major species of stored-product insects at elevated temperatures, while at 25°C this species can maintain low numbers of individuals for long periods, which can rapidly produce population outbursts when the prevailing conditions are suitable for its development.
... Problems arose for both species during larval development, when queens neglected or ejected their young. Although we cannot exclude eggs or larvae being abandoned due to poor health, we suggest this behaviour was more likely a response to stress or a perceived lack of resources (Smith 1985;Parmigiani and Vom Saal 1994). However, we did not observe any queen consuming their abandoned larvae, or failure of the larvae to feed pollen provided by the queen. ...
Bumblebees are important pollinating insects, but many species have suffered declines over the last century. Long-tongued bumblebees have been identified as particularly at risk, partly due to their more selective diet. Attempts to study these species in captivity have been impeded by stress-induced behaviours which cause queens to kill or abandon their brood. Here, we attempt to further develop techniques, using queen pairing and Bombus terrestris cocoons, to successfully rear two common long-tongued bumblebee species (B. pascuorum and B. hortorum) in captivity. Approximately half of queens laid eggs and 29% produced workers. Although challenges remain, there is a great deal to be gained from optimising the captive rearing of these species.
... Thus, we could conclude that the host legumes affect fecundity and adult emergence size. In these regards, our results are in accordance with those described by (Credland et al. 1986;Messina 1991;Smith and Lessells 1985) who point out the relationship between fecundity and the size of adults of Callosobruchus beetles. Additionally, Kawecki (1997) demonstrated that females emerging from Vigna radiate and Vigna angularis had different fecundities but apparently similar weights. ...
Haouel-Hamdi, S., Titouhi, F., Boushih, E., Dhraief, M.Z., Amri, M., and Mediouni-Ben Jemâa, J. 2017. Population demographic traits and reproductive parameters of the seed beetle Callosobruchus maculatus infesting stored lentil and chickpea commodities. Tunisian Journal of Plant Protection 12: 67-81. This paper carried out first exhausted investigations on pest status of the cowpea weevil Callosobruchus maculatus on two food legumes namely chickpea (Amdoun 1 variety) and lentil (Ncir variety) during six months of storage. Data on populations' dynamic, demographic traits, reproductive parameters, juvenile and adult fitness, economic injury level (EIL) and damages (impact on germination and weight losses) were studied through this work. Results revealed that C. maculatus is a major pest on stored chickpea in Tunisia. Moreover, results indicated that reproductive parameters, the juvenile and adult fitness of C. maculatus exhibited great variations among hosts. In this respect, linear regression analysis demonstrated that hosts have significant effects on adult fitness. Results showed that host contributed respectively by 77% for body weight and 80% for body size. Chickpea was more suitable host compared to lentil, since the mortality rate of eggs and larvae and the generation duration means were higher in lentil. In addition, significant differences were observed in the Susceptibility Index of the two food legume hosts showing chickpea seeds as moderately susceptible to C. maculatus attacks while, lentil seeds were resistant. C. maculatus caused large reductions in seed germination (78% chickpea and 33% lentil for highest infestation level 80%) and seeds weight (45% for chickpea against 8% for lentil after 6 months of storage) of both hosts; the infestation levels and the weight losses were significantly different in the storage periods. Overall, this study provides reasons for farmers and traders to make a decision to take a control action against C. maculatus during storage. Moreover, this work pointed out the variability of economic injury levels with host legumes.
... In these populations, many adults can emerge from a single seed, and females are much more likely to add eggs to occupied seeds (i.e., engage in superparasitism). Population comparisons (Messina and Mitchell 1989;Messina et al. 1991;Horng 1997), a previous selection experiment (Messina and Karren 2003;Messina 2004), and theoretical analyses (Smith and Lessells 1985;Toquenaga et al. 1994;Tuda and Iwasa 1998) have suggested that seed size is the main driver of these population differences. When seeds are large, avoidance and tolerance appear to maximize larval fitness, but aggressive behavior is favored in small seeds, where co-occurring larvae are bound to come into contact. ...
Colonization of new environments can lead to rapid changes in fitness-related traits. For herbivorous insects, switching to a new host plant can be comparable to invading a new habitat. Behavioral, physiological, and life-history traits commonly vary among insect populations associated with different plants, but how host shifts cause trait divergence is often unclear. We investigated whether experimental host shifts would modify a key insect trait, egg-laying behavior, in a seed beetle. Beetle populations associated long-term with either a small-seeded host (mung bean) or a large-seeded host (cowpea) were switched to each other’s host. After 36–55 generations, we assayed three aspects of oviposition behavior known to differ between the mung bean- and cowpea-adapted populations. Responses to the host shifts were asymmetrical. Females from lines transferred from mung bean to cowpea produced less uniform distributions of eggs among seeds, were more likely to add an egg to an occupied seed, and were more likely to “dump” eggs when seeds were absent. These lines thus converged toward the cowpea-adapted population. In contrast, the reciprocal host shift had no effect; oviposition behavior was unchanged in lines transferred from cowpea to mung bean. We suggest that these results reflect an asymmetry in the fitness consequences of each host shift, which in turn depended on differences in larval competitiveness in the original populations. Interactions among multiple fitness components are likely to make evolutionary responses less predictable in novel environments.
The big avocado seed weevil Heilipus lauri Boheman (Coleoptera: Curculionidae), is one of the most limiting pests for avocado exports in Latin America due to its quarantine nature. However, many aspects of its behavior and its relationship with the crop are still unknown. The infestation of an avocado backyard orchard at the Catholic University of the East in Antioquia, Colombia, and the removal of plant material allowed the collection of 66 infected fruits to collect biological data on the pest. The objective of this research was to determine the relationship between the number of perforations, the larvae found in the seeds and the morphological variables of the fruit. The results of this work suggest that a high proportion of the fruits drilled in the field have the presence of larvae of the pest, and that the weight of the fruits may influence the number of perforations carried out by the females. The instars did not show any relationship with the morphological variables of the fruits, nor with the number of perforations, which means that it is possible to find larvae of different instars regardless of the size of the fruit. These results suggest that drilling allows early detection of the pest and estimation of population densities of the immature stages in the field.
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