Population dynamics ofGlaux maritima (L.) along a distributional cline

Population fluctuations ofGlaux maritima, along a transect on a Baltle sea shore meadow, were recorded between 1979 and 1983. A bimodal distribution in numbers along the transect reflects the variation in factors regulating numbers: The two maintenance systems of the species, vegetative propagation and sexual reproduction play different roles. Vegetative propagation is fast and responds quickly to variations in the environment. The seeds germinate in strongly fluctuating temperatures which are triggered by disturbances such as flooding, damaging the vegetation.     

The occurrence and frequency of 2n pollen in 2x, 4x,and 6x wild,tuber-bearing Solanum species from Mexico,and Central and South America

Summary The occurrence of 2n pollen-producing plants was investigated in 187 plant introductions (PIs) of 38 wild species of tuber-bearing Solanum. These 2x, 4x, and 6x species are from Mexico, and Central and South America. The determination of 2n pollen-producing plants was conducted using acetocarmine glycerol. Plants with more than 1% large-size pollen were regarded as 2n pollen-producing plants. 2n pollen-producing plants were identified in the following species: 10 out of 12 Mexican 2x species, seven of nine South American 2x species, seven of seven Mexican and Central American 4x species, five of five South American 4x species, and five of five Mexican 6x species. The frequency of 2n pollen-producing plants varied among species at the same ploidy level, but the range of frequency, generally between 2 and 10% among species, was similar over different ploidy levels. The general occurrence of 2n pollen in both 2x and polyploid species, which are evolutionarily related, is evidence that the mode of polyploidization in tuber-bearing Solanums is sexual polyploidization. Furthermore, the frequencies of 2n pollen-producing plants in autogamous disomic polyploid species were not markably different from those of their related diploid species. It is thought that the frequent occurrence of 2n gametes with autogamy tends to disturb the fertility and consequently reduce fitness of polyploids. Thus, we propose that the breeding behavior of polyploids and the occurrence of 2n gametes may be genetically balanced in order to conserve high fitness in polyploid species in tuberbearing Solanum.Paper No. 3114 from the Laboratory of Genetics. Research supported by the College of Agriculture and Life Sciences; International Potato Center; USDA, SEA, CGRO 84-CRCR-1-1389; and Frito Lay, Inc.     

A unifying theory for methods of systematic analysis

A unifying theory for systematic analysis states that a number of methods should be used jointly to cope with various kinds of data; also that groups should be as consistent as possible, be made with least information loss, and where needed, be polythetic. A test of relationship, homogeneity, can use various kinds of data. It can take account of the internal variation of aggregate items such as genera. It can give due emphasis to smaller clusters that have likely important contexts of external items. It helps in analysing trends, cores and hazes in dendrograms. A proposed detector for formal groups can be based on measures of isolation, identifiability and inclusiveness. Non-mathematical, inter-item reaction tests such as hybridization and serology can also be used in grouping. All relationship data are used polythetically to reveal natural groups. This leads to a unified informational concept for taxa. This is more useful than the biological species concept that is restricted to inter-breeding data. All the methods appear to be analogues of the powerful human grouping instinct. The resulting compatibility is important as precise methods are needed mainly when the data are too complex for the mind to use reliably. Cladograms can be made by self-graded deweighting of homogeneity and agglomerative clustering. Unlike classical cladistics this can reveal any polythetic group. Finding the derived states for making cladograms is often much too hypothetical for a fully cladistic approach to be properly precise. Instead, where the evidence is weak, a milder strength of graded deweighting is used for the cladistic properties, which help to show relationships along with the others. Axiomatic failures of other classes of grouping methods are discussed. Unavoidable remnants of instinctive processing lower the precision of all the methods. The Uniter computer program, based on the theory, is tested with finely graded values of artificially ‘evolved’ items and with coarsely coded cladistic data. The results show that with natural data, the program should act as a fairly sensitive probe of past evolutionary branching. Another test shows how specimens from species complexes can be grouped and how distinctions between groups are analysed.     

Endophyte transmission and activity in the Anabaena-Azolla association

Summary The survival of Azolla was studied in an artificial system which simulated the soil/water interface and the desiccation of soil during a fallow period in lowland rice culture. Tests with non-sporulating and sporulating Azolla fronds showed that Azolla only survives with sporulated fronds. At their reappearance the Azolla fronds already harboured the Anabaena endophyte. A detailed light microscopic and transmission electron microscopic study of macro- and micros-porocarp formation and development revealed that the endophyte is transmitted by the macrosporocarps and not by the microsporocarps. The Anabaena cells within the macrosporocarps are found just below the indusium cap. These cells are not nitrogen-fixing akinetes. The free-living Anabaena cells at the stem apex and below the overarching developing leaves do not bear heterocysts and accordingly are non nitrogen-fixing. During the development of the leaf the Anabaena enters the leaf cavity, but later the pore of this, cavity closes and the imprisoned cyanobacteria are lysed before the leaf decays. As the Azolla leaves age a nitrogen-fixing capability is successively built up concomittantly with the production of heterocysts. Heterocyst frequencies of 40–50% can be found inAnabaena azollae. Usually a gradient of nitrogen-fixing capacity occurs along the Azolla rhizome with two distinct peaks at leaf number 7/8 and at leaf number 13/14 from the apex.     

强壮水螅的特征及其与寡水螅的种间差别问题

一种广泛分布于黑龙江省的大型具柄水螅被暂定为强壮水螅Hydra robusta(IT(?) 1947)。这一中国品系与IT(?)(1947)在日本报告的新种主要特征相同,包括具有精巢乳头。只是精巢乳头不稳定。在实验室条件下第一次有性生殖时每个雄体都发生精巢乳头,但第二次有性生殖时,同一群的后代可全部失去精巢乳头。这是介于强壮水螅与寡水螅Hydra oligactis Pallas(1766)之间的中间性状。从而导致作者做出结论,认为过去其他学者所主张的,以精巢乳头的有无做为鉴别特征来区分强壮水螅和寡水螅是不可靠的。因此,本文又检验了此种水螅的体细胞染色体,证明2n=30,其中第二对染色体上有明显近中位置的次缢痕,最小染色体的长度为最大染色体长度的二分之一以上。这些可做为此种水蝗的鉴别特征。对Niiyama(1944)和Datta(1970)在寡水螅上所做的染色体研究也做了比较及讨论。     

Sexual dimorphism in neuronal projections from the antennae of silk moths (Bombyx mori,Antheraea polyphemus) and the gypsy moth (Lymantria dispar)

Summary The antennal lobe of both sexes of the silk moth Bombyx mori contains 55–60 ventrally located antennal glomeruli; in addition, that of the male contains a dorsal macroglomerular complex (MGC). A group of identifiable glomeruli consisting of two lateral large glomeruli (LLG) and four medial small glomeruli (MSG) is present in both sexes, but the LLG are greatly enlarged in the female. A MGC is also present in the male gypsy moth Lymantria dispar and male giant silk moth Antheraea polyphemus. The MGC in all of these species is organized into 3–4 distinct levels of glomeruli. Antennal sensory fibers were stained by cobalt backfills in B. mori, A. polyphemus, and L. dispar. Most fibers stained from cut long hairs (sensilla trichodea) projected to MGC in males and LLG in both sexes of B. mori. The distribution of fibers in the MGC of B. mori was topographically biased in that a majority of fibers from anterior branches projected medially in MGC while most fibers from posterior branches projected laterally or anteriorly. Terminal arborizations of single fibers were each restricted to a single glomerular level of the MGC. Fibers projecting to the posterior antennal center were frequently stained in cut-hair and control preparations, apparently by uptake of cobalt through intact sensilla on flagellar branches.     

Stonefly nymphs use hydrodynamic cues to discriminate between prey

Summary Playback experiments conducted in a Rocky Mountain, USA, stream determined whether predatory stonefly nymphs (Kogotus modestus; Plecoptera: PerlodiMae) used hydrodynamic cues to discriminate prey species from nonprey species. In the laboratory we recorded pressure wave patterns associated with swimming escape behavior of Baetis bicaudatus (Baetidae), the favored mayfly prey species, and those of a nonprey mayfly, Ephemerella infrequens (Ephemerellidae). We video taped the responses of 24-h starved Kogotus to Baetis playbacks, Ephemerella playbacks or no playbacks made by oscillating (or not) live mayflies (Ephemerella) or clear plastic models placed within in situ flow-through observation boxes. The probability of attacks per encounter with Baetis playbacks was highest and independent of the model type used, but Kogotus also showed an unexpected high probability of attacks per encounter when Ephemerella playbacks were made through live Ephemerella. Thus, Kogotus discriminated between Baetis and Ephemerella swimming patterns but only when playbacks were made through the plastic model. Kogotus never attacked motionless mayflies or motionless plastic models. We allowed some Kogotus to successfully capture one small Baetis immediately before playbacks, which resulted in a much higher probability of attacks per encounter with Baetis playbacks on either model and a heightened discrimination of prey versus nonprey playbacks. The probability of attacks per encounter by Kogotus with live Baetis swimming under similar experimental conditions was strikingly similar to its response to Baetis playbacks made by oscillating the plastic model after a successful capture. Order of playback presentation (Baetis first or Ephemerella first) did not influence predatory responses to mayfly swimming patterns. This study is the first to document the use of hydrodynamic cues by stream-dwelling predators for discrimination of prey from nonprey and provides a mechanism to explain selective predation by stoneflies on Baetis in nature.     

Parasites and showy males: malarial infection and color variation in fence lizards

Summary Hamilton and Zuk (1982) proposed that the quality of male showy traits reflects genetically-based resistance to parasites and can be used by females to select mates that are less prone to parasitic attack. The hypothesis requires that a particular state of a variable showy trait should be associated with parasite infection. We tested this idea with a population of western fence lizards, Sceloporus occidentalis, infected with the malarial parasite, Plasmodium mexicanum. Ventral color pattern is strongly dimorphic in fence lizards and varies greatly among males in this population. Malaria-infected males exhibited significantly more black and less pale on their ventral surface than did noninfected males of similar body size. This difference was not a function of differing ages of infected and noninfected animals of the same body size. However, logistic regression demonstrated that females using male ventral color as a gauge of infection status would only marginally improve their chance of choosing a noninfected lizard over random selection of mates.     

Rise in age of sexual maturation in male Japanese monkeys at Takasakiyama in relation to nutritional conditions

A few reports have suggested the possibility that feeding conditions might affect the sexual maturation of free-ranging Japanese monkeys in provisionized troops. In the present study, the sexual maturation of male monkeys at Takasakiyama in 1984, nine years after the start of restriction of artificial feeding, was examined externally and histologically and the results were compared with data obtained in 1971, when artificial foods were abundantly given. Spermatogenesis was not observed in any of the males under 4.5 years old in the present study, whereas it was noted in some premature 3.5-year-old males and in all males over 4.5 years old in the 1971 study. The age of sexual maturation thus rose by one or more years over the 13-year period from 1971 to 1984. The lag in sexual maturation of the males at Takasakiyama in 1984 could have been induced by the restriction of artificial feeding.     

A ten-month study of endogenous testosterone levels and behaviour in outdoor-living female rhesus monkeys (Macaca mulatta)

Endogenous testosterone levels were measured in association with sexual, aggressive, and social/affiliative behaviors in 11 outdoor-housed female rhesus monkeys over a ten-month period. Several behaviors (sex directed toward the male, sex received from the male, aggression directed toward the male, submission directed toward the male, submission directed toward the female, and groom another female) were significantly (p<0.05) positively correlated with testosterone in from one to five females. No trends were strong enough across all females to suggest that any of these correlations have species-wide significance. Factor analysis revealed clearcut clusters of behaviors, but elevations in testosterone were not strongly associated with any of these clusters. It is concluded that endogenous testosterone levels have little measurable effect on overt behavior in female rhesus monkeys.