Correlated effects of the response to conditioned medium in the flour beetle,Tribolium castaneum

Dispersal rates were measured in lines selected for high and low response of egg production to conditioned media, and responsivness of egg production was measured in lines selected for high and low dispersal. A positive correlation was found between these two traits, each of which had previously been found to have a simple genetic basis. It is suggested that in Tribolium castaneum the sensitivity to environmental conditions is mediated through a Sensor gene, which can activate either response, according to circumstances.     

Depth distribution of adults and immatures of twoTribolium Castaneum strains in pure and mixed cultures

1. The distribution of adults and immatures of two Tribolium castaneum strains in plexiglas towers was studied both in single-strain and in mixed cultures.
2. The adults of the + + strain tended to be, on the average, deeper in the flour than the bb adults, in pure and in mixed cultures.
3. Adult distribution was independent of sex.
4. The correlation between adult and egg distribution was usually negative, due to either adult movement in the flour, or to reduced fecundity and increased cannibalism of eggs where adults were numerous, or both.
5. Larvae, and especially pupae, of bb were more abundant in the upper sections, and + + in the lower sections, of towers, both in pure and in mixed cultures and, in particular, at the higher density.
6. In general, the distribution of the strains in the mixed cultures was very similar to the pure cultures, showing a very small effect of the interaction between the two strains, in comparison with GHENT’S results with two species. It seems that the two strains are very much alike in their ability to exploit their environment and therefore their success is the same (when pupal cannibalism is reduced) whether the biological component of the environment is composed of one or two strains.

     

Two orthodenticle-related genes in the short-germ beetle Tribolium castaneum

 To investigate the molecular basis of head evolution, we searched for genes related to the Drosophila orthodenticle (otd) homeobox gene in the short-germ beetle Tribolium castaneum. Unexpectedly, we found that there are two otd-related genes in Tribolium, with predicted homeodomains highly similar to that of the single Drosophila gene. One of the two genes (Tc otd-1) is more related in both amino acid sequence and expression pattern to fruitfly otd. Tc otd-1 is expressed in a broad anterior stripe in the blastoderm embryo, suggesting a role in early head segmentation similar to that of the Drosophila gene. The second gene (Tc otd-2) is more similar in sequence to the otd-related genes isolated from different vertebrate species (the Otx gene family). Tc otd-2 is not transcribed in the blastoderm, but is expressed later in more limited subsets of cells in the anterior brain. Both Tribolium genes and the Drosophila gene are, unlike the vertebrate genes, also expressed at the developing ventral midline of the embryo. Our results are consistent with the idea that an otd/Otx gene specified anterior head structures in the last ancestor common to arthropods and vertebrates. Within the arthropod lineage, we propose that this gene acquired a function in cells at the developing midline prior to the duplication that generated the two Tribolium genes. Received: 16 February 1996 / Accepted: 1 March 1996 Edited by C. Desplan     

GENETIC VARIANCE FOR RATE OF POPULATION INCREASE IN NATURAL POPULATIONS OF FLOUR BEETLES,TRIBOLIUM SPP.

The genetic and ecological effects of population subdividsion were investigated for two wild strains of Tribolium castaneum and two wild strains of T. confusum and compared with the effects of population subdivision on the synthetic laboratory strain of T. castaneum (c-SM), used extensively in earlier experiments. For the c-SM strain, it has been shown repeatedly, for a variety of different population structures (different combinations of effective numbers, N_e, and migration rates, m), that large heritable differences in population growth rate arise among demes during 10 to 15 generations of population subdivision. Because this laboratory strain was synthesized by mass mating several “inbred” strains in 1973 (80 to 100 generations ago), it is possible that it has genetic variation for fitness (measured as the heritable variance among demes in the rate of population increase) unusually large compared to natural populations of flour beetles. In this paper, I report that natural populations of flour beetle exhibit as much or more phenotypic and genetic variation in the effects of population structure on fitness than the laboratory strain, c-SM. The observation of substantial heritable variation for fitness in natural populations is unexpected under additive theory and may be indicative of nonadditive genetic variance.     

TEMPERATURE EFFECTS AND GENOTYPE-BY-ENVIRONMENT INTERACTIONS IN HYBRIDS: HALDANE'S RULE IN FLOUR BEETLES

When males of the flour beetle, Tribolium castaneum, are crossed to females of its close relative T. freemani, the sex ratio of the hybrids is female biased, owing in part to hybrid male mortality. Morphological abnormalities are also frequent in the surviving hybrid males, but not in the hybrid females. The finding that the heterogametic sex (male) is more adversely affected in interspecific crosses than the homogametic sex is consistent with Haldane's rule, which predicts that hybrid dysfunction should emerge as an indirect byproduct of divergent adaptation to differing environments. If so, environmental effects and genotype-by-environment interactions (GEI) should characterize the expression of Haldane's rule and interspecific hybrid traits in general. We used two wild-collected populations of T. castaneum (from Infantes, Spain, and Madagascar) to investigate the effects of environmental variation on the expression of Haldane's rule. Males from each population were mated to several T. freemani females and the half-sibling hybrid progenies were reared across a series of temperature regimes. For both populations, we found that hybrids raised at higher temperatures exhibited a more extreme expression of Haldane's rule: The hybrid sex ratios were more biased toward females and hybrid males had a much higher incidence of morphological abnormalities. The average response to temperature, the norm of reaction for Haldane's rule, varied between the two populations, and we found considerable and significant GEI for both hybrid traits within both populations. The evolutionary implications of these findings are discussed in the context of speciation arising as an indirect effect of local adaptation.     

Suppression of the stored-product insect Tribolium confusum by Xylocoris flavipes and Amphibolus venator

Abstract:  We evaluated the suppression of the confused flour beetle, Tribolium confusum , by the anthocorid bug Xylocoris flavipes and the reduviid bug Amphibolus venator . Four treatments were tested: X. flavipes adults, A. venator adults, X. flavipes adults and A. venator adults released, and control (no predators). After 25 days, X. flavipes alone showed 96.9% suppression of T. confusum , A. venator alone showed 76.2% suppression and both the predatory bugs together showed 95.6% suppression. The rates of loss of whole-wheat flour as an index of damage caused by T. confusum were 2.7%, 6.4%, 3.6% and 11.7% in X. flavipes adults, A. venator adults, X. flavipes adults and A. venator adults released, and control respectively. Furthermore, A. venator attacked X. flavipes adults but not X. flavipes nymphs. The possibility of using both X. flavipes and A. venator against T. confusum is discussed.     

Effects of the plant alkaloid castanospermine as an antimetabolite of storage pests

The secondary plant compound castanospermine is toxic to the larvae of the bruchid beetle Callosobruchus maculatus F. and the flour beetle Tribolium confusum J. & V. when incorporated into the diet. The larval alimentary tract -D-glucosidase and -D-glucosidase activities of C. maculatus were strongly inhibited by castanospermine in a non-competitive and competitive manner respectively. The larval alimentary tract -D-glucosidase activity of T. confusum was strongly inhibited in a competitive manner, but the -D-glucosidase activity was not markedly inhibited; however, the -D-galactosidase activity exhibited strong uncompetitive inhibition.

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Résumé La castanospermine, substance secondaire végétale, incorporée à l'aliment est toxique pour les larves de Callosobruchus maculatus F. et de Tribolium confusum J. & V. Les activités -D-glucosidase et -D-glucosidase du tube digestif de C. maculatus ont été fortement inhibées par la castanospermine respectivement de façon non-compétitive et compétitive. L'activité -D-glucosidase du tube digestif de T. confusum était, fortement inhibée d'une façon compétitive, mais l'activité -D-glucosidase n'était pas nettement inhibée; cependant, l'activité -D-galactodase ne présentait pas une forte inhibition compétitive.

     

An experimental analysis of the relationships between fitness components and malic enzyme genotypes inTribolium confusum

The hypothesis that natural selection is capable of maintaining allozyme variation in natural populations was tested using a species of flour beetles,Tribolium confusum. We selected a polymorphic locus (a locus encoding variation for malic enzyme) in an experimental population ofT. confusum and scored the genotypes at this locus for a series of fitness components on different flour types. Measurements included survival rate, development time, fecundity, and rate of egg cannibalism. Flour type had significant effects on most traits. Significant differences among genotypes for fecundity and rates of egg cannibalism and the presence of genotype × flour type interactions for development time were demonstrated. Thus, changes in allele frequencies at the malic enzyme locus could in part be under the influence of natural selection. The existence of genotype × flour type interactions suggests that environmental heterogeneity could maintain allozyme variation at the malic enzyme locus.     

Response of Tribolium castaneum larvae to synthetic aggregation pheromone

Responses of larval Tribolium castaneum Herbst. to the synthetic adult aggregation pheromone (4,8-dimethyldecanal) were studied. Larvae of T. castaneum were attracted both by contact and vapour of 4,8-dimethyldecanal at concentrations of 1, 5 and 10 g. g^-1 of medium.

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Reaktion von Tribolium castaneum Larven auf synthetisches Aggregationspheromon

Zusammenfassung Die Reaktionen der Larven von T. castaneum auf das kunstliche Aggregations pheromon (4,8-dimethyldecanal) in Versuchen in Petrischalen untersucht. Die Larven wurden angezogen, wenn sie mit Pheromon auf Filterpapier oder mit verdampftem Pheromon in Kontakt kamen. Diese Reaktion wurde bei Konzentrationen von 1, 5 und 10 g · g^-1 Medium festgestellt. Die höchste Konzentration rief die grosste Reaktion hervor. Fruhe Larvenstadien zeigten stärkere Reaktionen als spatere Stadien.

     

赤拟谷盗和杂拟谷盗的生殖隔离研究

赤拟谷盗和杂拟谷盗是两个同域发生的近缘储粮害虫。为明确它们的生殖隔离程度和机制,本研究比较分析了赤拟谷盗和杂拟谷盗雄虫对同种和异种雌虫的交配选择;赤拟谷盗与杂拟谷盗交配后,测定了精子在异种雌体内的存活情况;将赤拟谷盗和杂拟谷盗进行正反杂交,研究其F1代、F2代和回交代杂种是否产生及其雌雄比。结果显示,赤拟谷盗和杂拟谷盗雄虫对同种雌虫的爬跨率和交配率高于其对异种雌虫的爬跨率和交配率,表明赤拟谷盗和杂拟谷盗种间性隔离不完全;赤拟谷盗和杂拟谷盗交配后精子在异种雌体内是存活的,杂交所产的F1代卵为受精卵,说明交配后完成了精子传送和受精过程,表明种间机械隔离和配子隔离不完全;赤拟谷盗和杂拟谷盗的杂种F1代自交和回交产生了F2代和回交代,表明种间不存在杂种不育;一些杂交组合产生的F2代和回交代数量少且存在雌雄性比偏离,表明种间存在部分杂种不活和杂种衰败。本研究明确了赤拟谷盗和杂拟谷盗的生殖隔离机制,这对于揭示它们的物种进化关系有着重要意义。