Distribution of male yellow dungflies around ovipasition sites: the effect of body size

Abstract.

• 1 Spatial and temporal variation in body size of yellow dungflies, Scatophaga stercoraria, gathering on and around cow droppings was studied in an Icelandic population in order to elucidate the effect of male and female size on male mating tactics.
• 2 Males copulating on droppings were on average larger than males copulating in the grass, but of similar size to males guarding ovipositing females. Males searching on droppings were smaller than males copulating or guarding females on droppings but larger than males copulating in the grass. No such differences were found in female size.
• 3 Resource-holding power of males (RHP, i.e. male: female size ratio) differed between the three mating groups and was highest for males on the droppings. Size and RHP clearly affect the tactics of copulating males. Males with low RHP tend to copulate in the grass in spite of the cost of longer copulation duration. We argue that this is caused by risk of takeovers from large searching males.
• 4 There was no change in male size with the age of individual droppings. Contrary to what might be expected, large searching males are not predominantly found at fresh droppings when the probability of catching unpaired females is highest. We suggest instead that good prospects in taking females over from other males must make the strategy to search for females on older droppings profitable.
• 5 RHP did not change with age of dropping in the three mating groups. The size of ovipositing females increased with age of dropping, probably reflecting longer copulation and egg-laying times of large females.
• 6 We found an overall positive relationship between sizes of male and female partners. This correlation was highly significant for copulating pairs in the grass. This is probably a consequence of males with low RHP copulating in the grass and fights in which larger males take over females from smaller males. A weaker, but significant, correlation was found amongst ovipositing pairs. This must be due to take-over effects. No size correlation was found for pairs copulating on droppings.

     

Effect of acetylcholine on growth and isoperoxidases of the lentil(Lens culinaris) root

The effects of acetylcholine (Ach) on growth, the total peroxidase activity and the isoperoxidase spectrum of the roots ofLens culinaris were studied and compared with actual and earlier results obtained with an auxin (IAA) treatment. The general growth and peroxidase activity patterns of Ach treated roots and IAA treated ones showed many important similarities.     

Temporal consistency is currency in shifts of transient visual attention

Background

Observers respond more accurately to targets in visual search tasks that share properties with previously presented items, and transient attention can learn featural consistencies on a precue, irrespective of its absolute location.

Methodology/Principal Findings

We investigated whether such attentional benefits also apply to temporal consistencies. Would performance on a precued Vernier acuity discrimination task, followed by a mask, improve if the cue-lead times (CLTs; 50, 100, 150 or 200 ms) remained constant between trials compared to when they changed? The results showed that if CLTs remained constant for a few trials in a row, Vernier acuity performance gradually improved while changes in CLT from one trial to the next led to worse than average discrimination performance. The results show that transient attention can quickly adjust to temporal regularities, similarly to spatial and featural regularities. Further experiments show that this form of learning is not under voluntary control.

Conclusions/Significance

The results add to a growing literature showing how consistency in visual presentation improves visual performance, in this case temporal consistency.     

Two closely linked tomato HKT coding genes are positional candidates for the major tomato QTL involved in Na+/K+ homeostasis

The location of major quantitative trait loci (QTL) contributing to stem and leaf [Na⁺] and [K⁺] was previously reported in chromosome 7 using two connected populations of recombinant inbred lines (RILs) of tomato. HKT1;1 and HKT1;2, two tomato Na⁺‐selective class I‐HKT transporters, were found to be closely linked, where the maximum logarithm of odds (LOD) score for these QTLs located. When a chromosome 7 linkage map based on 278 single‐nucleotide polymorphisms (SNPs) was used, the maximum LOD score position was only 35 kb from HKT1;1 and HKT1;2. Their expression patterns and phenotypic effects were further investigated in two near‐isogenic lines (NILs): 157‐14 (double homozygote for the cheesmaniae alleles) and 157‐17 (double homozygote for the lycopersicum alleles). The expression pattern for the HKT1;1 and HKT1;2 alleles was complex, possibly because of differences in their promoter sequences. High salinity had very little effect on root dry and fresh weight and consequently on the plant dry weight of NIL 157‐14 in comparison with 157‐17. A significant difference between NILs was also found for [K⁺] and the [Na⁺]/[K⁺] ratio in leaf and stem but not for [Na⁺] arising a disagreement with the corresponding RIL population. Their association with leaf [Na⁺] and salt tolerance in tomato is also discussed.     

Environmental drivers of the bryophyte propagule bank and its comparison with forest-floor assemblage in Central European temperate mixed forests

Species richness, composition and abundance of the bryophyte diaspore bank of Central European temperate mixed forests were compared with the forest-floor bryophyte assemblage. The impact of environmental variables and anthropogenic disturbances, including tree species composition, stand structure, microclimate, light conditions, soil and litter properties, management history, and landscape properties, potentially influencing bryophyte diaspore bank assemblages were explored. Thirty-four, 70–100 years old mixed stands with differing tree species composition were examined in the ?rség National Park, Western Hungary. The diaspore bank was studied by soil collection and cultivation, and data were analysed by multivariate methods. Contrary to the forest-floor bryophyte assemblage, where substrate availability, tree species composition and stand structure were the most influential environmental variables, the composition and abundance of the diaspore bank was mainly affected by site conditions (microclimate, litter and soil properties). Species richness of the bryophyte diaspore bank was lower than that of the forest-floor bryophyte assemblage. Short-lived mosses (colonists, short-lived shuttles) were dominant in the diaspore bank, as opposed to the forest-floor bryophyte community, where perennial mosses dominated. In the studied forests, the importance of the bryophyte diaspore bank was relatively low in the regeneration and maintenance of the forest-floor bryophyte vegetation.     

Observations on the development and maintenance of the deep sea barnacle,Octolasmis aymonini geryonophila (Pilsbry)

Thirty-two pedunculate barnacles, O. a. geryonophila, were maintained in culture for a period of 2 yr in the laboratory. These barnacles were obtained from the pleopods and mouth parts of the giant marine isopod, Bathynomus giganteus, which had been collected, at a depth of 200 fathoms, in the Gulf of Mexico.

The carina, scutum, mandible and maxilla of adult barnacles were typical of deep water species. However, the tergum and labrum were intermediate between those of shallow and deep water species.

Adults 3.1–4.1 mm in length were cultured in sea water (15–19°C), and fed on benthic copepods such as Tisbe furcata and Laophonte sp. Three broods of nauplii from 8 barnacles were obtained in 2 yr. Larvae were reared on plankton collected from Coney Island waters in which nauplii reached Stage IV in 10–14 days at 16°C. Isochrysis galbana and Thalassiosira pseudonana individually or in combination maintained nauplii to Stage IV, but with very high mortality. The lack of spines on the carapace edge of the nauplii distinguishes this deep water species from the shallow water form, O. mulleri.     

Habitat complexity affects how young of the year Atlantic cod Gadus morhua perceive predation threat from older conspecifics

The response of age 0+ year juvenile Atlantic cod Gadus morhua to the presence of age 1+ and age 3+ year conspecifics was measured with and without cover available. Juveniles reacted by aggregating more closely and maintaining distance from older conspecifics in an experimental setting without cover but only to age 3+ year conspecifics when cover was available. The results indicate that prior residence of older juveniles can affect age 0+ year juveniles during benthic settlement and highlights the conservation value of structurally complex nursery habitats.     

Ecological correlates and phylogenetic signal of host use in North American unionid mussels

Mussels in the order Unionoida comprise ～75% of the world’s freshwater bivalve species and are free-living apart from a brief larval stage that parasitizes fish. We investigated the relationships among species of North American unionid mussels and their known host fishes from a macroevolutionary perspective to test whether and how ecological and evolutionary factors correlate with patterns of host use. A subset of 69 mussel species was chosen based on data availability regarding their fish host repertoires, phylogenetic relationships, and ecology. Despite the brevity of their parasitic life stages, the mussels conformed to the right-skewed distribution of host specificity typical of parasitic taxa, in which most species are specialists and a few are generalists. Phylogenetic least squares regression models identified affinity for low-gradient and riffle habitats, and colonization of post-glacial watersheds as the best predictors for the number of fish host species per mussel. However, the second-best model identified citation number as a predictor of the number of hosts, implying that many mussel–host interactions still remain to be identified. A Multiple Regression Mantel test was performed to identify factors associated with the proportion of hosts shared between pairs of mussel species. Range overlap, citations, genetic distance, and similarity in host infection strategy were significantly correlated with the proportion of hosts shared, yet total variation as explained by the best model was low (R²?=?0.14). There was evidence of a topological association between mussels and their hosts (P?=?0.001) and a significant phylogenetic signal of host specificity (λ?=?0.81, P?=?0.003), indicating closely related mussels that overlap in range are more likely to be competing for hosts. Our results provide an initial macroevolutionary framework for studying the evolution of host infection strategies in these mussels but also highlights gaps still remaining in our fundamental ecological knowledge of this endangered clade.     

Variation in egg mass within two Atlantic herring Clupea harengus stocks

The main objective of this study was to investigate if egg size (mass) at spawning is invariant for Scotia-Fundy summer and autumn (SFSH) and Icelandic summer (ISSH) spawning herring Clupea harengus. Oocyte dry mass measurements for SFSH females collected in 2001 and ISSH females collected in 1999 and 2000 showed a large variation. Difference in egg dry mass among fish was found to vary by as much as twofold in each stock. For ISSH, variation in egg mass was also apparent from oocyte volume measurements made jointly with a histological examination of the ovaries. Approximately 20% of the variation in egg mass could be explained by maternal whole-body mass or total length, indicating that length or age composition in the stocks can potentially influence the recruitment success. This implies that fisheries management strategies should aim to maintain a broad range in age composition.