CALLING SONG DISPLACEMENT IN A ZONE OF OVERLAP AND HYBRIDIZATION

The ground crickets Allonemobius fasciatus and A. socius meet in a mosaic zone of overlap and hybridization stretching from the East Coast to at least Illinois. To test whether male calling song differences were enhanced in sympatry, we analyzed the songs of crickets from inside and outside the zone of overlap along two transects. No evidence of calling song displacement was found in A. socius males from populations within the zone of overlap. On the other hand, A. fasciatus displayed calling song displacement in three populations. Our results are consistent with the hypothesis that the selective pressure exerted by the challenge from a related species is frequency dependent. While not a conclusive demonstration, the observed shifts in calling song are strongly suggestive of reproductive character displacement.     

Egg weight, batch size and fecundity of the spotted stalk borer, Chilo partellus in relation to weight of females and time of oviposition

The egg laying pattern of the spotted stalk borer on sorghum and maize, Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae) was studied during the first three nights of oviposition under laboratory conditions. More than 50% of both eggs and egg batches are laid during the first night of oviposition. Batch size decreases with time, whereas mean egg weight remains constant.Larger females lay both larger eggs and egg batches than smaller ones. They are also more fecund but it is only the second night of oviposition that contributes significantly to this difference.The reproductive effort decreases much with time. Allocation of reproductive reserves to early eggs seems more important than having eggs evenly distributed over time. Larger females use proportionally more resources to the production of late eggs. Large eggs are likely to contain more yolk which could be of importance for the ballooning behaviour of newly hatched larvae.

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Résumé La ponte de C. partellus Swinhoe a été étudiée au laboratoire pendant les trois premières nuits de la ponte. Plus de 50% des ooplaques et des oefs ont été pondus pendant la première nuit. La taille des ooplaques diminue avec le temps, tandis que le poids moyen des oeufs reste constant.Les grosses femelles pondent des ooplaques et des oeufs plus grands que les petites. Elles sont aussi plus fécondes, mais c'est seulement à la seconde nuit de ponte qu'est due cette différence.Le reproduction diminue beaucoup avec le temps. L'affectation aux premiers oeufs des réserves utilizées pour la reprodution semble plus importante que l'émission d'oeufs régulièrement répartis dans le temps. Les grosses femelles utilisent proportionnellement plus de ressources à la production d'oeufstardifs. Les gros oeufs contiennent vraisemblablement plus de vitellus que pourrait être nécessaire pour le comportement aérostatique des chenilles néonates.

     

Salt sensitivity in chickpea (Cicer arietinum L.): ions in reproductive tissues and yield components in contrasting genotypes

The reproductive phase in chickpea (Cicer arietinum L.) is affected by salinity, but little is known about the underlying cause. We investigated whether high concentrations of Na⁺ and Cl^– in the reproductive structures influence reproductive processes. Chickpea genotypes contrasting in tolerance were subjected to 0, 35 or 50 mm NaCl applied to soil in pots. Flower production and abortion, pod number, percentage of empty pods, seed number and size were evaluated. The concentrations of Na⁺, K⁺ and Cl^– were measured in various plant tissues and, using X‐ray microanalysis, in specific cells of developing reproductive structures. Genotypic variation in reproductive success measured as seed yield in saline conditions was associated with better maintenance of flower production and higher numbers of filled pods (and thus seed number), whereas seed size decreased in all genotypes. Despite the variation in reproductive success, the accumulation of Na⁺ and Cl^– in the early reproductive tissues of developing pods did not differ between a tolerant (Genesis836) and a sensitive (Rupali) genotype. Similarly, salinity tolerance was not associated with the accumulation of salt ions in leaves at the time of reproduction or in seeds at maturity.     

The type and timing of social information alters offspring production

The acquisition and use of information are essential for decision-making in an uncertain world. The use of social information, or information from the behaviour of others, may be a common and efficient mechanism to improve estimates of resource quality by animals. According to theory, social information cues with higher information content should have a greater influence on decision-making, and current information should be weighed more than prior information. However, experimental tests of these hypotheses remain scarce. We exposed female cactus bugs (Chelinidea vittiger) to different types of social information (the presence of conspecific eggs or nymphs) presented at different times (current or prior to egg laying) to determine the influence of social information on offspring production. We found that social information substantially altered the number of eggs produced. The presence of conspecific eggs, regardless of timing, consistently increased egg production, whereas nymphs only increased egg production when present during egg laying. We conclude that the type and timing of social information may have an important, yet unappreciated, influence on reproductive allocation.     

粉尘螨生殖系统形态学研究

粉尘螨Dermatophagoides farinae是一种重要的医学螨类。本文用光镜和扫描电镜研究了粉尘螨雌雄生殖系统的形态和结构。结果表明：雄性生殖系统由睾丸、输精管、 附腺、射精管、阳茎及附属交配器官组成。睾丸位于血腔末端,不成对,精原细胞、精母细胞和精子依照精子发育的顺序有规则地分布在其内部。雌性生殖系统包括交配孔、囊导管、储精囊、囊导管、卵巢、输卵管、子宫、产卵管及产卵孔,其中卵巢由一个中央营养细胞和围绕其周围的卵母细胞组成。     

The effect of timing of pollination on the mating system and fitness ofKalmia latifolia (Ericaceae)

Plant mating systems are known to vary within species and some immediate ecological factors have been found to be associated with the geographic distribution of selfing. The environmental condition of the maternal plant may influence the production of selfed seed relative to outcrossed seed. This study investigated the effect of late pollination on the mating system of Kalmia latifolia, a long-lived perennial shrub. A 2 × 2 experimental design was used to determine whether reproductive success declines over the course of the flowering season and whether there was an interaction between pollination time (early vs. late in the season) and pollen type (self-fertilized vs. outcrossed). An interaction of this sort would indicate context-dependent fitness of selfed seeds compared to outcrossed seeds and, thus, show an ecological influence over a plant's mating system. Relative fitness was assessed in terms of female reproductive success. Timing of pollination did not affect abortion of outcrossed seeds; however, delay in pollination increased abortion of selfed seeds by 34.7%. Thus, it appears that plants selectively aborted selfed seeds rather than outcrossed seeds and this selection was more intense at the end of the season. An ecological factor such as time of pollination may affect the mating system of K. latifolia.     

Simultaneous spawning by female stream goby Rhinogobius sp. and the association with brood cannibalism by nesting males

A laboratory experiment was conducted by varying the undersurface area of nesting substratum and the number of females in an experimental tank to elucidate the determinants of the mating pattern in the stream goby, Rhinogobius sp. cross‐band type. Males with larger nests tended to attract two or more females to their nest in a tank. Moreover, males spawned simultaneously with multiple females and entire brood cannibalism by males was rarely observed under a female‐biased sex ratio. When males spawned with a single female with low fecundity, however, entire brood cannibalism occurred at a high frequency, suggesting that a male guarding a nest with fewer eggs consumes the brood. Therefore, spawning behaviour of females that leads to a large egg mass would decrease the risk of entire brood cannibalism. In this species, simultaneous spawning by multiple females in a nest serves as a female counter‐measure against entire brood cannibalism. These results suggest that a conflict of interest between the sexes through brood cannibalism is a major determinant of simultaneous spawning.     

Reproduction of Meloidogyne incognita Race 3 on Flue-cured Tobacco Homozygous for Rk1 and/or Rk2 Resistance Genes

Most commercial tobacco cultivars possess the Rk1 resistance gene to races 1 and 3 of Meloidogyne incognita and race 1 of Meloidogyne arenaria, which has caused a shift in population prevalence in Virginia tobacco fields toward other species and races. A number of cultivars now also possess the Rk2 gene for root-knot resistance. Experiments were conducted in 2013 to 2014 to examine whether possessing both Rk1 and Rk2 increases resistance to a variant of M. incognita race 3 compared to either gene alone. Greenhouse trials were arranged in a completely randomized design with Coker 371-Gold (C371G; susceptible), NC 95 and SC 72 (Rk1Rk1), T-15-1-1 (Rk2Rk2), and STNCB-2-28 and NOD 8 (Rk1Rk1 and Rk2Rk2). Each plant was inoculated with 5,000 root-knot nematode eggs; data were collected 60 d postinoculation. Percent galling and numbers of egg masses and eggs were counted, the latter being used to calculate the reproductive index on each host. Despite variability, entries with both Rk1 and Rk2 conferred greater resistance to a variant of M. incognita race 3 than plants with Rk1 or Rk2 alone. Entries with Rk1 alone were successful in reducing root galling and nematode reproduction compared to the susceptible control. Entry T-15-1-1 did not reduce galling compared to the susceptible control but often suppressed reproduction.     

Within‐group relatedness is correlated with colony‐level social structure and reproductive sharing in a social fish

In group‐living species, the degree of relatedness among group members often governs the extent of reproductive sharing, cooperation and conflict within a group. Kinship among group members can be shaped by the presence and location of neighbouring groups, as these provide dispersal or mating opportunities that can dilute kinship among current group members. Here, we assessed how within‐group relatedness varies with the density and position of neighbouring social groups in Neolamprologus pulcher, a colonial and group‐living cichlid fish. We used restriction site‐associated DNA sequencing (RADseq) methods to generate thousands of polymorphic SNPs. Relative to microsatellite data, RADseq data provided much tighter confidence intervals around our relatedness estimates. These data allowed us to document novel patterns of relatedness in relation to colony‐level social structure. First, the density of neighbouring groups was negatively correlated with relatedness between subordinates and dominant females within a group, but no such patterns were observed between subordinates and dominant males. Second, subordinates at the colony edge were less related to dominant males in their group than subordinates in the colony centre, suggesting a shorter breeding tenure for dominant males at the colony edge. Finally, subordinates who were closely related to their same‐sex dominant were more likely to reproduce, supporting some restraint models of reproductive skew. Collectively, these results demonstrate that within‐group relatedness is influenced by the broader social context, and variation between groups in the degree of relatedness between dominants and subordinates can be explained by both patterns of reproductive sharing and the nature of the social landscape.