Distribution and spacing of Drosophila mycetophaga flies on bracket fungi used as mating arenas

Abstract.

• 1 To understand the nature of male aggregations in Drosophila mycetophaga, data were collected on male and female distribution and male spacing on bracket fungi used as mating arenas in cool rainforests of south-eastern Australia.
• 2 Both males and females appeared to be aggregated among bracket fungi that were used as mating arenas. Females were associated with large male aggregations. The probability of a fungus being occupied increased with its area. However, a multiple Poisson regression analysis suggested that fungus area did not affect female distribution when male number was controlled.
• 3 The presence of female breeding and feeding resources did not determine where aggregations were formed, because there were aggregations on fungi without resources, and fungi with resources were not used more often than those without them.
• 4 D.mycetophaga males did not select and defend territories within bracket fungi, and did not determine female access to areas. However, males were more evenly spaced than expected on the basis of a random distribution, suggesting that males kept apart from each other.
• 5 The distribution of the different sexes and male spacing pattern supports the interpretation that D.mycetophaga has a lek mating system.

     

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.

     

Changes in the behavior of the female short-tailed cricket,Anurogryllus muticus (De Geer) (Orthoptera: Gryllidae) following mating

InAnurogryllus muticus females, mating stimulates burrow construction, burrow provisioning, feeding, egg production, and egg-laying. Since mating often occurs before the ovaries are fully developed, the time span between mating and oviposition is used for increased food intake and the accumulation of nutrient reserves in the fatbody. Oviposition triggers maternal care of eggs and emerging hatchlings, and blocks egg consumption. Hatchling behavior is investigated. When hatchlings eat eggs, they prefer newly laid over older, embryonic eggs.     

Multiple paternity in the red-eyed treefrog Agalychnis callidryas (Cope)

DNA fingerprinting of tadpoles from two different ‘one female-two male’ matings of the red-eyed treefrog, Agalychnis callidryas, revealed multiple paternity of offspring. Offspring were assigned paternity based on bands shared with the putative father, but not shared between putative fathers or with the mother. Paternity was split 44/56% and 36/64% in two matings. These results do not support a hypothesis of sperm priority in access to unfertilized eggs by primary males. Multiple paternity may be commonplace in species of anurans with matings by multiple males.     

植物生活史对策的进化

植物生活史对策的进化班勇（中国林业科学院林业研究所,北京１０００９１）ＥｖｏｌｕｔｉｏｎｏｆＬｉｆｅＨｉｓｔｏｒｙＳｔｒａｔｅｇｙｉｎＰｌａｎｔｓ￥ＢａｎＹｏｎｇ（ＲｅｓｅａｒｃｈＩｎｓｔｉｔｕｔｅｏｆＦｏｒｅｓｔｒｙ,ＣｈｉｎｅｓｅＡｃａｄｅｍｙｏ...     

Mating type differentiation in tetrahymena thermophila: Characterization of the delayed refeeding effect and its implications concerning intranuclear coordination

Mating type determination in Tetrahymena thermophila involves developmentally programmed, heritable alterations of the macronucleus, localized to the mtd locus. This determination can be predictably controlled by the environmental conditions during macronuclear development, eg, temperature and time of refeeding. In this article we have further characterized the effects of delayed refeeding on mating type determination, as revealed by the frequency of mating types among the progeny of a cross. Our results show that 1) the magnitude of this starvation effect decreases with temperature of conjugation and becomes undetectable at 18°C; 2) starvation during the interval 14 to 22 hr (after conjugation is induced at 30°C) is a necessary and sufficient condition for the induction of starvation effects; 3) relative mating type frequencies vary monotonically with nutrient concentration present during this critical period; and 4) sister macronuclei, developing under starvation conditions in the same cytoplasm, differentiate majority mating types characteristic of early or late refeeding; sister macronuclei show no apparent correlation with each other. On the basis of our observations on early and late refed cells, we propose that the composition of the newly developed macronucleus is the outcome of two key events: 1) mating type determination at the mtd locus and 2) differential molecular cloning of generally one or two autonomously replicating fragments (ARFs) of the macronuclear DNA bearing the mtd locus.     

Life history variation among female surfperches (Perciformes: Embiotocidae)

Synopsis Life history variation within the family Embiotocidae is extensive and involves differences in age of first reproduction, fecundity schedules, growth rates, longevity and size of young. Based on maximum reported body lengths, there are three distinct size groups among the family's 23 species. Small species do not exceed 215 mm TL, medium-size species attain 275 to 335 mm TL, and the large species attain 380 to 470 mm TL. The longevity oh surfperches varies from two to ten years, growth is indeterminate, and females of the medium-and large-size groups may delay first reproduction beyond age one. With one exception, all species show increasing length-specific fecundities. The life history characteristics of females differ among the three size groups. Relative to smaller species, the largest species have moderately high fecundity, delayed maturity and long life. Medium-size species have low fecundity, may delay maturity for 1 to 3 years and have intermediate life spans. Small species have generally higher, but variable, fecundity, do not delay maturity, and are short lived. Among the small North American species, the trend in fecundity varies inversely with environmental predictability. Fecundity is highest in the species which occupies highly seasonal freshwater environments. Coastal species produce moderately large broods and species which occupy stable deep water environments produce the smallest broods.     

Limits of artificial selection under unbalanced mating systems

Summary The influence of unbalanced mating systems — factorial mating (FM) and random loss of families after a full diallel crossing (RS) — on the ultimate probability of gene fixation (u()) and the time required to fix or lose a gene (t()) are investigated. The average u() of these systems is smaller than that of random mating, and the range of u() for a given initial parental genotype combination is very large (close to one for most initial genotypic combinations). The average u() of different parental genotypic combinations of a given gene frequency are different. These systems accelerate the t().This article was written and prepared by U.S. Government employees on official time, and it is therefore in the public domain     

中国疫霉属异宗配合种的交配型

在疫霉属真菌中,很多种是重要的经济植物的病原菌,寄主范围广泛,包括乔木、灌木和各种农作物;为害性大,常带来严重的经济损失。本文主要研究疫霉异宗配合种的交配型。根据疫霉在纯培养和成对培养(dual culture)中产生有性器官的能力,疫霉属可分为同宗配合种和异宗配合种两大类群。异宗配合种的A~1交配型与同一种或其它种的A~2交配型进行成对培养时,可以形成有性器官。两个可亲合菌系配合而形成有性器官时,可能发生基因重组,其结果将使病原菌具有更强的生存能力、致病力以及更广泛的寄主范围。因此,研究疫霉两种不同的交配型的分布,不仅对认识病害的发生发展规律,进一步设计防治措施有着重要意义,而且对疫霉属的起源、演化和移栖也有着深远的理论意义。作者对收集到的7个异宗配合种:Phytophthora capsici,P.cinnamomi,P.citrophthora,P.colocasiae,P.infestans,P.nicotianae,P.palmivora的38个分离物进行了交配型的研究,测定工作使用澄清的Campbell蔬菜汁琼脂培养基(V8C),用于确定交配型的菌系有P.nicotianae var.parasitica A~1,P.nicotianae var.parasitica A~2,P.cinnamomi A~1,P.cinnamomi A~2,P.palmivora A~1,P.palmivora A~2.每个分离物分别与已知种的A~1和A~2两个菌系成对接种于同一V8C平板上,放入25℃温箱中培养,2周后在两个菌落的连线上检查有性器官的产生情况。实验结果表明,中国疫霉属异宗配合种的这些分离物的交配型与寄主或地理分布似无相关性,同一种植物上分离到的同种疫霉可以是A~1交配型,也可以为A~2交配型;同一地区可以出现两种交配型,不同地区又有相同的交配型。云南西双版纳橡胶园中的分离物(P.citrophthora,P.colocasiae,P.palmivora)都表现为中性。