Male larval nutrition in Choristoneura rosaceana (Lepidoptera: Tortricidae): an important factor in reproductive success

This study examines how Choristoneura rosaceana male quality, as determined by larval diet, age and mating history, affects the reproductive success of both sexes. While the size of the spermatophore produced at first mating increased linearly with male age, the frequency of mating was significantly higher for middle-aged males (2–4 days old) than younger (0–2 days old) or older (6–8 days old) individuals, when both sexes were fed on artificial diet. However, the duration of copulation was longer in couples with older than younger males. The observed age-related changes in spermatophore size had no significant effect on female longevity, fecundity or fertility, suggesting no direct relationship between male investment and spermatophore size under these experimental conditions. Different larval food sources (artificial diet, maple and hazelnut) did not affect the proportion of 2-day-old virgin males that mated; however, the proportion that remated was significantly higher for males reared on high-quality food (maple and artificial diet) than those on hazelnut, a poorer food source. There was a 5-fold decline in spermatophore size between the first and second matings on all diets, but female reproductive output was reduced by only 25%. In contrast, while the first spermatophore produced by males on hazelnut was 1.5 times smaller than those produced on maple and artificial diet, the fecundity of their mates was 40% less than those mated with high-quality virgin males. These results provide additional support to the idea that spermatophore size is not a valuable indicator of male quality. Most tethered females placed in the field during the first flight period mated with virgin males (based on the size of the spermatophore), suggesting that female choice exists in this species. These results are discussed in relation to the incidence of polyandry in naturally occurring populations of Choristoneura and the potential use of size and/or chemical cues by females to assess male quality.     

Colonization of artificial substrates by benthos in a second-order high altitude river in Kenya

An investigation on the colonization of artificial substrate baskets by benthos was carried out in the Naro Moru River, a second-order high altitude river in Kenya, from November, 1986 to October, 1987. Simuliidae dominated the colonizing benthos. The mean (±95% CL) maximum colonization time was achieved after 9.63±1.57 days. The highest mean diversity (H) occurred after 6 days of exposure whilst the highest mean H_maximum, evenness (J) and species richness (s) were achieved after 10, 8 and 10 days respectively.The benthos arrival rate (AR) declined exponentially with time. The changes in benthos departure rate (DR) with time was insignificant. Equilibrial state (AR:DR=1.0) was not achieved in the present study.     

THE FOUNDING OF A NEW POPULATION OF DARWIN'S FINCHES

We report the natural colonization of the small Galápagos island Daphne Major by the large ground finch (Geospiza magnirostris). Immigrants of this species were present in every year of a 22-yr study, 1973–1994. Typically they arrived after a breeding season and left at the beginning of the next one. Geospiza magnirostris bred on the island for the first time in the exceptionally wet El Niño year of 1982–1983, and bred in all subsequent years except drought years. In agreement with theoretical expectations the frequency of inbreeding was unusually high. Pronounced fluctuating asymmetry in tarsus length, together with slightly reduced breeding success of inbreeding pairs, suggests a low level of inbreeding depression. Despite this, the population increased from 5 breeding individuals in 1983 to 20 breeding individuals in 1992, and probably more than twice that number in 1993, largely through recruitment of locally born birds.     

Bifurcation, Bursting, and Spike Frequency Adaptation

Many neural systems display adaptive properties that occur on timescales that are slower than the time scales associated withrepetitive firing of action potentials or bursting oscillations. Spike frequency adaptation is the name givento processes thatreduce the frequency of rhythmic tonic firing of action potentials,sometimes leading to the termination of spiking and the cell becomingquiescent. This article examines these processes mathematically,within the context of singularly perturbed dynamical systems.We place emphasis on the lengths of successive interspikeintervals during adaptation. Two different bifurcation mechanisms insingularly perturbed systems that correspond to the termination offiring are distinguished by the rate at which interspike intervalsslow near the termination of firing. We compare theoreticalpredictions to measurement of spike frequency adaptation in a modelof the LP cell of the lobster stomatogastric ganglion.     

Density- and frequency-dependent predation of artificial bird nests

Predators are often expected to vary their relative predation rates according to the frequency of prey types in the environment (frequency-dependent predation). The underlying cause for this must lie in some dependency of absolute predation rates on the density of prey types in the environment (density-dependent predation). However, frequency-dependent predation may either be caused by 'simple' density-dependent predation, in which the absolute predation rate on a given prey type depends purely on the density of that type, or by more complex responses in which absolute rates depend also on the density of other prey types. It is usually difficult to distinguish the underlying cause of frequency-dependent predation, because frequencies tend to change as densities change. Here, we describe the results of an experiment conducted to disentangle these phenomena under two prey richness (low and high) conditions. We used artificial bird nests (placed on shrubs and on saplings) baited with quail eggs placed in natural forests as models of natural bird nests. Our results indicate that both the absolute and relative predation rates on the prey types may vary in complex ways. Predation rates depend on a complex interaction between the prey's own density, other prey density and the diversity of prey in the environment. Neglecting to include, or consider, these complexities into analyses may lead to erroneous conclusions in studies of absolute or relative predation rates.     

Colonization history of north European field voles (Microtus agrestis) revealed by mitochondrial DNA

The genetic structure of field vole (Microtus agrestis) populations from northern Europe was examined by restriction fragment length polymorphisms of mitochondrial DNA (mtDNA) in 150 individuals from 67 localities. A total of 83 haplotypes was observed, most of which were rare and highly localized geographically. Overall nucleotide diversity was high (134%), but showed a tendency to decrease with higher latitude. Two major mtDNA lineages differing by 2% in nucleotide sequence were identified. A southern mtDNA lineage was observed in field voles from Britain, Denmark and southern and central Sweden, whereas voles from Finland and northern Sweden belonged to a northern lineage. The strict phylogeographic pattern suggests that the present population generic structure in field voles reflects glacial history: the two groups are derived from different glacial refugia, and recolonized Fennoscandia from two directions. A 150–200-km-wide secondary contact zone between the two mtDNA groups was found in northern Sweden. Distinct phylogeographic substructuring was observed within both major mtDNA groups.     

侗族九个红细胞血型系统和ABH分泌型的分布

报道了广西侗族的ABO、MNSs、Rhesus、Duffy、Kidd、P、Diego、Lewis和Xg等九种红细胞血型系统和ABH唾液分泌型的分布。共调查了201名父母均系侗族而彼此无血缘的学生,其中男116名,女85名。结果表明,广西侗族中ABO系统的r基因(0.6286)、MN系统的m基因(0.6294)、Duffy系统的Fy~a基因(0.9651)、Kidd系统的JK~a基因(0.4628)和Rhesus系统的CDe染色体(0.7532)等频率都很高,ABO系统的q基因(0.1672)、P系统的P_1基因(0.1333)和Lewis系统的Le~a基因(0.3232)等频率较低。MNSs系统的S基因(0.0124)频率很低,而MS染色体连锁率却为零。Xg系统的Xg~a基因频率(0.3746)与汉族和维吾尔族一样,处于低水平。Lewis系统的Le(a )表型者中发现八例是ABH唾液分泌型,但分泌的物质不是A便是B,而分泌H物质的唾液分泌型者全部都是Le(a-)型。六个民族间遗传距离分析表明,侗族与壮族在血缘上最近,其次是与朝鲜族、蒙古族、汉族相近,而与维吾尔族最远。     

华北地区汉族的Lewis、ABO、MN、Rh、P等血型系统和ABH分泌型的分布

调查了原籍华北地区汉族的ABO、Lewis、MN、Rh、P等血型系统和ABH分泌型的分布,结果表明:O型(33.44％)和B型(29.38％)较多;N型(27.97％)略多于M型(27.65％);Le(a )型的频率很高(24.17％)。在94人中还发现四名Le(a )型属于ABH分泌型,且都属于分泌A或B血型物质的类型,无一例为分泌H血型物质的类型;Rh(D)阴性率仅0.3％,CCDee和CcDE型占75％以上;P_1( )型占39.1％;ABH分泌型占72％,低于全国其他民族中已知的分布。     

Infrared spectra of carbon monoxide bound to mitochondria from diverse species and tissues reveal structurally similar cytochrome c oxidase dioxygen reaction sites

Infrared bands for CO bound to mitochondria from bovine and porcine hearts, bovine brain, rat kidney, and blowfly flight muscle and to intact blowfly flight muscle have been measured in the carbon-oxygen stretch region. Each spectrum contains a narrow band near 1963 cm-1 similar to the major band found earlier for the carbonyl cytochrome c oxidase purified from bovine heart. A second band near 1959 cm-1 ascribed to a less stable conformer of the purified oxidase carbonyl is also detected in mitochondria. These spectra support very similar CO (and O2) binding sites among all the oxidases examined whether the enzyme is purified or is still within mitochondria or intact tissue and therefore suggest that the reduced heme A ligand binding site has been highly conserved during evolution.