Cuticular Hydrocarbon Content that Affects Male Mate Preference of Drosophila melanogaster from West Africa

Intraspecific variation in mating signals and preferences can be a potential source of incipient speciation. Variable crossability between Drosophila melanogaster and D. simulans among different strains suggested the abundance of such variations. A particular focus on one combination of D. melanogaster strains, TW1(G23) and Mel6(G59), that showed different crossabilities to D. simulans, revealed that the mating between females from the former and males from the latter occurs at low frequency. The cuticular hydrocarbon transfer experiment indicated that cuticular hydrocarbons of TW1 females have an inhibitory effect on courtship by Mel6 males. A candidate component, a C25 diene, was inferred from the gas chromatography analyses. The intensity of male refusal of TW1 females was variable among different strains of D. melanogaster, which suggested the presence of variation in sensitivity to different chemicals on the cuticle. Such variation could be a potential factor for the establishment of premating isolation under some conditions

Differences in Male Mate Recognition between the Invasive <i>Anoplophora glabripennis</i> (Coleoptera: Cerambycidae) and Japanese Native <i>A. malasiaca</i>

The Asian longicorn beetle Anoplophora glabripennis is a recently arrived invasive species to Japan. The Japanese native A. malasiaca shows an extensive overlap with A. glabripennis with host plants, niches, and emergence season. Hybridization between these two species is suspected in Japan. The surface of the female is covered with contact sex pheromones that elicit male mating behavior within species. We evaluated the contact pheromonal activity of crude extract and fractions of female A. glabripennis coated on a black glass model and revealed a hydrocarbon fraction and a blend of fractions to show activity but relatively weak, suggesting the presence of other unknown active compounds. Few male A. glabripennis showed mating behavior when they were exposed to a crude extract of female A. malasiaca. However, a considerable number of A. malasiaca males mounted and showed abdominal bending behavior when presented with glass models that were coated with each extract of female A. glabripennis and A. malasiaca. Gomadalactones are essential contact pheromone components that elicit mating behavior in male A. malasiaca; however, we could not detect them in female A. glabripennis extract. Here, we investigated the possible reasons for this phenomenon and the difference in male mate recognition systems between these two species

Virulence of entomopathogenic fungi to the termite from colony C.

<p>Virulence of entomopathogenic fungi to the termite from colony C.</p

Concentration-dependent avoidance of 6 isolates of high- and low-virulence entomopathogenic fungi by the termite <i>C. formosanus</i>.

<p>The vertical axis shows the proportion of termites that chose the stimulus odor branch. n = 30. A: Choice of the odor from <i>I. fumosorosea</i> K3 conidia suspension (y = −0.067x + 0.53, r² = 0.120, p<0.001, linear regression). B: Choice of the odor from <i>I. fumosorosea</i> 8555 conidia suspension (y = −0.051x + 0.60, r² = 0.057, p = 0.001, linear regression). C: Choice of the odor from <i>B. brongniartii</i> 782 conidia suspension (y = −0.066x + 0.58, r² = 0.106, p<0.001, linear regression). D: Choice of the odor from <i>B. bassiana</i> F1214 conidia suspension (y = −0.028x + 0.62, r² = 0.016, p = 0.088, linear regression). E: Choice of the odor from <i>M. anisopliae</i> 455 conidia suspension (y = −0.046x + 0.64, r² = 0.044, p = 0.005, linear regression). F: Choice of the odor from <i>M. anisopliae</i> UZ conidia suspension (y = 0.002x + 0.54, r²<0.001, p = 0.922, linear regression).</p

Attachment and persistence of FITC-labeled conidia of high-virulence entomopathogenic fungi on <i>C. formosanus</i> cuticle.

<p>A: Termites treated with <i>I. fumosorosea</i> K3 were reared individually (y = −1.281x + 31.90, r² = 0.160, p<0.001, linear regression). B: Termites treated with <i>I. fumosorosea</i> K3 were reared as a group (y = −1.553x + 30.01, r² = 0.209, p<0.001, linear regression). C: Termites treated with <i>B. brongniartii</i> 782 were reared individually (y = −1.319x + 36.85, r² = 0.266, p<0.001, linear regression). D: Termites treated with <i>B. brongniartii</i> 782 were reared as a group (y = −1.474x + 28.67, r² = 0.247, p<0.001, linear regression). E: Termites treated with <i>M. anisopliae</i> 455 were reared individually (y = −0.789x + 23.51, r² = 0.262, p<0.001, linear regression). F: Termites treated with <i>M. anisopliae</i> 455 were reared as a group (y = −0.900x + 17.98, r² = 0.257, p<0.001, linear regression). n = 10. : Termites just after inoculation. : Termites at 3 h post-inoculation. : Termites at 6 h post-inoculation. : Termites at 24 h post-inoculation. Bars at the top of the columns represent standard errors. n = 10.</p

Chemical Discrimination and Aggressiveness via Cuticular Hydrocarbons in a Supercolony-Forming Ant, <em>Formica yessensis</em>

<div><h3>Background</h3><p>Territorial boundaries between conspecific social insect colonies are maintained through nestmate recognition systems. However, in supercolony-forming ants, which have developed an extraordinary social organization style known as unicoloniality, a single supercolony extends across large geographic distance. The underlying mechanism is considered to involve less frequent occurrence of intraspecific aggressive behaviors, while maintaining interspecific competition. Thus, we examined whether the supercolony-forming species, <em>Formica yessensis</em> has a nestmate recognition system similar to that of the multicolonial species, <em>Camponotus japonicus</em> with respect to the cuticular hydrocarbon-sensitive sensillum (CHC sensillum), which responds only to non-nestmate CHCs. We further investigated whether the sensory system reflects on the apparent reduced aggression between non-nestmates typical to unicolonial species.</p> <h3>Methodology/Principal Findings</h3><p><em>F. yessensis</em> constructs supercolonies comprising numerous nests and constitutes the largest supercolonies in Japan. We compared the within-colony or between-colonies’ (1) similarity in CHC profiles, the nestmate recognition cues, (2) levels of the CHC sensillar response, (3) levels of aggression between workers, as correlated with geographic distances between nests, and (4) their genetic relatedness. Workers from nests within the supercolony revealed a greater similarity of CHC profiles compared to workers from colonies outside it. Total response of the active CHC sensilla stimulated with conspecific alien CHCs did not increase as much as in case of <em>C. japonicus</em>, suggesting that discrimination of conspecific workers at the peripheral system is limited. It was particularly limited among workers within a supercolony, but was fully expressed for allospecific workers.</p> <h3>Conclusions/Significance</h3><p>We demonstrate that chemical discrimination between nestmates and non-nestmates in <em>F. yessensis</em> was not clear cut, probably because this species has only subtle intraspecific differences in the CHC pattern that typify within a supercolony. Such an incomplete chemical discrimination via the CHC sensilla is thus an important factor contributing to decreased occurrence of intraspecific aggressive behavior especially within a supercolony.</p> </div