SEXUAL SELECTION IN AMERICAN TOADS: A TEST OF A GOOD-GENES HYPOTHESIS

Adaptive mate choice in species lacking male resource control and/or paternal care might be maintained by selection because preferred males sire genetically superior offspring. For such a process to occur, some male phenotypic trait(s) must both reliably indicate male genetic quality and influence the pattern of mate choice by females. In American toads, Bufo americanus, male body length has been documented to influence female mating patterns: females usually mate with males that are larger than average. However, the relationship between male size and male genetic quality is unknown. We conducted a controlled breeding experiment using 48 sires and 19 dams to determine if larger males sire offspring with superior larval performance characteristics (greater survival to metamorphosis, larger mass at metamorphosis, and earlier metamorphosis). We also aged each sire to test the hypothesis that older males are, on average, genetically superior to younger males. We crossed each female with three sires representing three body size categories (mean and 1 SD ± mean snout-ischium length). Hatchlings (500 from each cross) were reared to metamorphosis in seminatural ponds in the field. Metamorph weight (log transformed) and age at metamorphosis showed significant heritability and were genetically correlated with each other. Hence, sires differed in genetic quality. However, none of the three measures of offspring performance was correlated with sire body size or age. Thus, we obtained no support for the prediction that sire body size or age is related to genetic quality.     

Reflections on biosystems motivating supramolecular engineering

Some goals of bioelectronics—interfacing biology and electronics — are the understanding of supramolecular bioprocesses and the construction of supramolecular devices. The principles for the design and fabrication of machineries with functional components of molecular size are inspired by reflecting on biosystems, and it seems important to consider such principles. We first discuss attempts to construct supramolecular machines, and then we consider the bacterial reaction centre as an example where supramolecular engineering helps to elucidate a bioprocess. We then discuss possible mechanisms leading to the emergence of life-like systems in the light of the basic principles used to design supramolecular devices. Finally, we reflect on prospects in molecular engineering inspired by studying the emergence of life-like systems.     

On the relationship between food, reproduction and survival of two carabid beetles: Calathus melanocephalus and Pterostichus versicolor

Abstract.

• 1 The relative influences of temperature and availability of food on reproduction, survival and growth of all developmental stages of two carabid beetle species are discussed with special reference to the suggested relationship between availability of food, size of egg production and survival of adults from one breeding season to the next.
• 2 Temperature as well as food supply influence the length of larval growth and adult body size. Beetles grown at low temperatures and low amounts of food are smaller than those grown at higher temperature and with more food.
• 3 The number of eggs laid per female was correlated with the amount of food gathered. There was no inverse relationship (trade-off) between reproductive output and survival in the field until the next breeding season.
• 4 In 1980 no significant relationship was found between winter mortality and the amounts of food gathered by beetles in the period after reproduction and before winter diapause. However, in 1981 in C. melanocephalus a lower number of starved beetles survived the winter than the fed ones and‘field’beetles.
• 5 Only in the first part of the feeding activity period in autumn can enough food be gathered by C.melunocephalus for successful hibernation. In the second part of this period there is not enough food to build up the fat reserves needed to survive the winter.
• 6 Difference in population fluctuations of both species are discussed in relation to their life histories.

     

湘北烟区烟青虫发生情况研究

烟青虫在湘北烟区1年发生5代,第一至四代危害烟草,第五代在其他作物上取食。自然条件下,世代重叠比较明显,幼虫发生与危害最大的是第一代,危害时期是5月下旬至6月下旬,同时,还得出了烟青虫各代的发生期、历期及其发育起点温度和有效积温。     

褐飞虱五龄若虫翅芽长度与成虫翅型关系的研究

褐飞虱饲养于不同水稻品种、不同生育期以及不同种群密度条件下,5龄若虫翅芽长度与成虫翅型具有稳定的相关性：翅芽长于1．10mm羽化后为长翅型雌虫,介于0．96～1．09mm之间为长翅型雄虫或短翅型雌虫,小于0．95mm为短翅型雄虫。根据5龄若虫翅芽长度结合外生殖器特征,编制了成虫翅型检索表。由此,可在5龄若虫期预测成虫的翅型和种群盛衰的趋势。     

THE POPULATION DYNAMICS OF NORTHERN SEA LIONS, 1975-1985

Abstract: Populations of northern sea lions ( Eumetopias jubatus ) in the vicinity of Marmot Island, Alaska declined during 1975–1985 at about 5% per year (Merrick et al. 1987). The cause of this decline is not known. A life table for the northern sea lion was calculated assuming that life spans follow a Weibull distribution. Samples of northern sea lions taken in the vicinity of Marmot Island, Alaska during 1975–1978 and 1985–1986 indicate that the average age of females older than 3 yr increased about 1.55 yr (SD = 0.35 yr) while the population was declining at about 5% per year. Fecundity rates decreased by 10% over the same period, but the decrease was not statistically significant (Calkins and Goodwin 1988). Possible causes of the population decline and the change in age structure were examined by writing the Leslie matrix population equation in terms of changes in juvenile and adult survival rates and fecundity, and examining the short–term behavior of the trajectories of the average age of adult females, total number of females, and total number of pups with respect to those changes in the vital parameters. From the observed rate of declines of adults and the changes in average age of adult females and fecundity, estimates of the changes in adult and juvenile survival were calculated; estimates of the standard deviations of these changes were estimated via a bootstrap procedure. One purpose of this exercise is to aid in setting priorities for research for determining the cause of the decline. An explanation for the observed declines in numbers of adult sea lions consistent with the observed fecundity rates, a rate of decrease of 5% in the number of adults, and the corresponding increase in average age (of females age 3 yr and older) was a 10%–20% decrease in the survival of juveniles (age 0-3 yr) coupled with an insignificant change in adult survival (0.03%, SD = 1%).     

Effects of Different Photoperiods and Chilling Treatments on Growth and Reproduction of Cardamine flexuosa With. and Its Ecological Implications

Abstract Phenotypic variability of Cardamine flexuosa (Cruciferae) was examined in response to different lengths of exposure to low temperature (5°C) at the juvenile stage, and to two photoperiod regimes (8 and 16 hrs day-lengths) in the subsequent growth period. The results indicated that this species had a facultative chilling or long-day requirement for flowering. The long-day and chilling treatments both caused an earlier onset of stem internode elongation. Longer chilling treatments reduced the number of nodes and increased internode length under both long and short photoperiod regimes. Prolonged chilling treatments followed by long-day photoperiod remarkably induced more numerous basal branches and inflorescences, as a result producing more siliques. Remarkable rosette leaves Were formed at the base of the main stem when partial chilling and the short-day treatment suppressed stem internode elongation. The responses to chilling and long-day treatment closely resembled the synchronized flowering of this species in spring in the field. Delayed flowering under the short-day treatment resembled size- or age-dependent flowering in late summer to autumn in the field populations.     

The effect of growth form on the evaporation in some subalpine mosse

In order to evaluate the importance of growth of mosses in controlling evaporative water loss, the evaporation rates of some subalpine moss species of various growth forms were compared with each other. The growth forms of the xerophytic species examined were large cushion and compact mat, while those of the mesophytic species in the coniferous forest floor were smooth mat, weft and tall turf. The evaporation rate per moss dry weight (Ew) was much smaller in the xerophytic species than in the mesophytic species. However, the evaporation rate per basal area of moss colony (Ea) was not necessarily smaller in the xerophytic species. The relation between Ea and dry weight per basal area of the colony (Wa) had a close correlation with the growth form. It was concluded that the difference in the evaporation rate per weight between the exerophytic species and the mesophytic species was largely due to the difference in Wa, and that the growth forms of the xerophytic species were suitable for increasing Wa without increasing surface roughness.     

Effects of the parasitic botfly Philornis carinatus on nestling house wrens,Troglodytes aedon,in Costa Rica

I studied the life cycle of a botfly (Diptera: Muscidae: Philornis carinatus) and examined the effects of botfly ectoparasitism on nestling house wrens (Passeriformes: Troglodytidae: Troglodytes aedon) during three years in Costa Rica. At three study sites, I found that nestlings were relatively unaffected by botflies, in contrast to all other studies of birds infected with philornid botflies. At Monteverde, the main study site, infected chicks grew slightly slower and had slightly shorter tarsi and wing chords than uninfected chicks, but both groups fledged at similar weights. Since weight at fledging is the only growth character associated with post-fledging survivorship, botfly infections likely cost wrens little in terms of fitness. At all sites, fledging success did not differ between infected and uninfected nests. Botfly infections were more prevalent at two lower elevation sites than at the high elevation Monteverde side. Infection prevalence increased during the nesting season at all study sites, which suggests a botfly life cycle in which adult population levels increase during the wren breeding season and then decline during a dormant period when wrens are not nesting. Finally, botflies may attack chicks throughout the period before fledging, but there is no indication they locate nests before hatching. In sum, botfly parasitism on wrens appears to be benign, perhaps because the study sites are at the edge of the botfly's range or because wrens are not a preferred host.     

Evolutionary epistemology as an overlapping,interlevel theory

I examine the branch of evolutionary epistemology which tries to account for the character of cognitive mechanisms in animals and humans by extending the biological theory of evolution to the neurophysiological substrates of cognition. Like Plotkin, I construe this branch as a struggling science, and attempt to characterize the sort of theory one might expect to find this truly interdisciplinary endeavor, an endeavor which encompasses not only evolutionary biology, cognitive psychology, and developmental neuroscience, but also and especially, the computational modeling of artificial life programming; I suggest that extending Schaffner's notion of interlevel theories to include both horizontal and vertical levels of abstraction best fits the theories currently being developed in cognitive science. Finally, I support this claim with examples drawn from computational modeling data using the genetic algorithm.