Twenty-spotted ladybird responses to synthetic volatiles (▪) versus solvent (CH₂Cl₂) controls (□) in a Y-tube behavioral assay.

<p>*: <i>P</i>-value of chi-square test against the expectation of random (1∶1) beetle choices.</p

Amounts of volatiles (mean

<p>±<b>SE) emitted from healthy and powdery mildew-infected plants in the greenhouse.</b> Panels A and B show individual compounds from whole plants and single leaves, respectively: A, (<i>E</i>)-2-hexenal; B, (<i>Z</i>)-3-hexenol; C, unknown; D, 3-octanone; E, 1-octen-3-ol; F, 3-octanol; G, benzyl alcohol; H, (<i>E</i>)-β-ocimene; I, octanol; J, nonanal; K, linanlool; L, (<i>E</i>)-4,8-dimethyl-1,3,7-nonatriene; M, ethylbenzaldehyde; N, 4-ethylbenzaldehyde; O, nonanol; P, decanal; Q, ethylacetophenone; R, ethylacetophenone; S, decanol. (The pairs of compounds, (i) M and N and (ii) Q and R, were determined to be isomers of ethylbenzaldehyde and ethylacetophenone, respectively.) Panels C and D show total volatiles. “Systemic” refers leaves without powdery mildew on infected plants. Lowercase letters indicate significant differences among treatments (<i>P</i><0.05 by ANOVA followed by Tukey-Kramer HSD).</p

Sexual versus Asexual Reproduction: Distinct Outcomes in Relative Abundance of Parthenogenetic Mealybugs following Recent Colonization

<div><p>Asexual reproduction, including parthenogenesis in which embryos develop within a female without fertilization, is assumed to confer advantages over sexual reproduction, which includes a “cost of males.” Sexual reproduction largely predominates in animals, however, indicating that this cost is outweighed by the genetic and/or ecological benefits of sexuality, including the acquisition of advantageous mutations occurring in different individuals and the elimination of deleterious mutations. But the evolution of sexual reproduction remains unclear, because we have limited examples that demonstrate the relative success of sexual lineages in the face of competition from asexual lineages in the same environment. Here we investigated a sympatric occurrence of sexual and asexual reproduction in the pineapple mealybug, <i>Dysmicoccus brevipes</i>. This pest invaded southwestern Japan, including Okinawa and Ishigaki Islands, in the 1930s in association with imported pineapple plants. Our recent censuses demonstrated that on Okinawa sexually reproducing individuals can coexist with and even dominate asexual individuals in the presence of habitat and resource competition, which is considered to be severe for this nearly immobile insect. Molecular phylogeny based on partial DNA sequences in the mitochondrial and nuclear genomes, as well as the endosymbiotic bacterial genome, revealed that the asexual lineage diverged from a common sexual ancestor in the relatively recent past. In contrast, only the asexual lineage exhibiting obligate apomictic thelytoky was discovered on Ishigaki. Co-existence of the two lineages cannot be explained by the results of laboratory experiments, which showed that the intrinsic rate of increase in the sexual lineage was not obviously superior to that of the asexual lineage. Differences in biotic and/or abiotic selective forces operating on the two islands might be the cause of this discrepancy. This biological system offers a unique opportunity to assess the relative success of sexual versus asexual lineages with an unusual morphology and life cycle.</p></div

Twenty-spotted ladybird responses to natural volatiles emitted from healthy (□) and infected (▪) plants in a Y-tube behavioral assay.

<p>A: an assays using whole plants; B: an assays using volatiles collected from whole plants, eluted in solvent (CH₂Cl₂), and re-evaporated from a filter-paper disc. *: <i>P</i>-value of chi-square test against the expectation of random (1∶1) beetle choices.</p

Developmental and reproductive performances (mean ± SE) of the sexually and asexually reproducing lineages of <i>Dysmicoccus brevipes</i> on Okinawa Island.

<p>Developmental and reproductive performances (mean ± SE) of the sexually and asexually reproducing lineages of <i>Dysmicoccus brevipes</i> on Okinawa Island.</p

Frequencies of sexual and asexual individuals of <i>Dysmicoccus brevipes</i> from Okinawa (a) and Ishigaki (b).

<p>Frequencies of sexual and asexual individuals of <i>Dysmicoccus brevipes</i> from Okinawa (a) and Ishigaki (b).</p

Phylogeny of the sexual and asexual lineages based on partial sequences of mitochondria (<i>CO1</i>; a), an intracellular symbiont (<i>rpoB</i>; b), and the nuclear (ITS2; c) genome.

<p>The trees were constructed by the maximum likelihood method using unambiguously aligned nucleotide sites. The trees of <i>rpoB</i> and ITS2 are rooted on each midpoint. The bootstrap values (>50%) obtained from 1000 resamplings are given at the nodes. Sequences of the taxa with the DDBJ/EMBL/GenBank accession numbers in brackets were obtained from the database.</p

Figure S1. Preparative (a) HPLC and (b) GC chromatograms. from Sex pheromone of a coccoid insect with sexual and asexual lineages: fate of an ancestrally essential sexual signal in parthenogenetic females

The 5% diethyl ether/pentane fraction from silica gel open-column chromatography was separated by HPLC, and fraction Lc. 3 was separated by GC. The pheromone compound was isolated at Gc. 2

Copulation of the pineapple mealybug, <i>Dysmicoccus brevipes</i>.

<p>Adult males and females exhibit completely different appearances and biology.</p