The nature and role of learning in the orientation and migratory behavior of fishes

Synopsis Fish migration may be viewed as the product of two processes; the selection and tracking of optimal environmental conditions through time and space, and the use of predictive information about environmental structure to bias movements towards a goal. The establishment and maintenance of directional bias is based on the interaction of experience and instinct. The preoccupation of much fish orientation research with innate fixed patterns of behavior on one hand and hydrodynamics on the other has led us to underestimate the possibility that orientation is a flexible process relying on developmental sequences, calibration of the motor-sensory interaction based on experience and the learning of environmental pattern. Evidence illustrating how experience and learning may influence the direction of movement and how the goal is recognized is presented according to two general categories: (a) imprinting and early experience and (b), spatial learning, including the social transmission of migratory routes and directions. In the first category, the olfactory hypothesis of salmon homing is briefly reviewed and new data presented describing olfactory imprinting in Atlantic salmon,Salmo salar. In the second category, evidence is presented demonstrating the modifiability of sun-compass orientation and the ability of some fish species to learn the spatial distribution of landmarks. The role of social transmission in the migration of coral reef fishes is reviewed. The possible role of these learning phenomena in the formation of familiar area maps, route-based and location-based navigation and the critical distance factor is considered. The relationship between life history and the nature of learning in migratory orientation is discussed     

The genetic structure of a primate species: Rhesus macaques and other Cercopithecine monkeys

Among rhesus macaques (Macaca mulatta)and other cercopithecine monkeys, social groups occupying adjacent home ranges (i.e., members of the same local population) exchange individuals and genes and thus exhibit marked genetic similarities. To assess the degree to which this pattern extends beyond the local population, the genetic structure of M. mulattaand six other primate species was determined using Nei’s (1973) gene-diversity analysis. The genetic similarities seen among social groups in the Dunga Gali population of M. mulatta (Melnick et al.,1984a) can be seen over the entire species range. Comparison of these results with the structures of other similarly organized primate species indicates that (1) the average social group contains most of its local population’s genetic diversity, (2) the average local population contains the majority of the genetic diversity found in the region to which it belongs, and (3) the proportion of species gene diversity found in the average regional population varies substantially between species. Genetic homogeneity within local and regional populations is probably the product of gene flow. The application of a number of analytical models of selection and gene flow strongly suggests that gene flow, genetic drift, and zoogeography offer a more parsimonious and plausible explanation for interspecific variation in regional differentiation than does stabilizing selection.     

Effect of adaptation to high light intensity on the kinetics of energy transfer from phycobilisomes to photosystem II in Anabaena cylindrica

Transfer efficiencies between phycobilisomes and photosystem II antenna chlorophylls were determined on membrane fragments isolated from low and high light adapted Anabaena cells. The observed increase in energy transfer in high light adapted cells is a consequence of shorter interchromophore distances and a decrease in the number of jumps of the exciting photons. Calculation of the rates of energy transfer and the coupling energies indicate that the weak interaction inferred for energy transfer between phycobilisome and photosystem II in low light adapted cells is replaced by an intermediate interaction in high light adapted cells.Abbreviations LLA low light adapted - HLA high light adapted - PBS phycobilisome - PS photosystem     

Do holly leaf spines really deter herbivory?

Summary Although spinose teeth of holly leaves have been widely cited as an example of a physical defense against herbivores, this assumption is based largely on circumstantial evidence and on general misinterpretation of a single, earlier experiment. We studied the response of third and fifth instar larvae of the fall webworm, Hyphantria cunea Drury, a generalist, edge-feeding caterpillar, to intact American holly leaves and to leaves that had been modified by blunting the spines, by removing sections of leaf margin between the spines, or by removing the entire leaf margin. The results suggest that the thick glabrous cuticle and tough leaf margin of Ilex opaca are more important than the spinose teeth in deterring edge-feeding caterpillars. Microscopic examination of mature leaves revealed that the epidermis is thickened at the leaf margin, and that the leaf is cirucumscribed by a pair of fibrous veins. In simple choice tests neither domesticated rabbits nor captive whitetailed deer discriminated between spinescent holly foliage and foliage from which spines were removed. Nevertheless, we found little evidence of herbivory by mammals in the field, either on small experimental trees or in the forest understory. While it is possible that spinose teeth contribute to defense by reducing acceptibility of holly relative to other palatable plant species, we suggest that the high concentrations of saponins and poor nutritional quality of holly foliage may be more important than spines in deterring vertebrate herbivores. The degree of leaf spinescence and herbivory was compared at different heights with the tree canopy to test the prediction that lower leaves should be more spinescent as a deterrent to browsers. Leaves on lower branches of mature forest trees were slightly more spinescent than were upper leaves, and juvenile trees were slightly more spinescent than were mature trees. However, there was no relationship between degree of spinescence and feeding damage. The greater spinescence of holly leaves low in the canopy is probably an ontogenetic phenomenon rather than a facultative defense against browsers.The investigation reported in this paper (No. 87-7-8-77) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Dirctor     

Consequences of a mixed reproductive system in the hog peanut,Amphicarpaea bracteata, (Fabaceae)

Summary The forest annual, Amphicarpaea bracteata L. can reproduce via aerial chasmogamous, aerial cleistogamous, and subterranean cleistogamous flowers. Both plant size and light intensity influenced the utilization of the three modes of reproduction. chasmogamous and aerial cleistogamous flower number and the ratio of chasmogamous flowers to the total number of aerial flowers increased with plant size. The latter demonstrated a shift to xenogamy and outbreeding in larger plants. Light intensity indirectly influenced reproductive modes through its infuence on plant size. Seed set by both types of aerial flowers was low and unrelated to plant size. Subterranean seed number and the total dry weight of subterranean seeds per plant increased with size. The subterranean seeds of Amphicarpaea bracteata are thirty-four times larger than the aerial seeds (fresh weight). Under field conditions, subterranean seeds had greater germination after one year than acrial seeds. The plants arising from subterranean seeds were significantly larger and more fecund than those from aerial seeds. Seeds produced by aerial cleistogamous, hand selfpollinated chasmogamous, and naturally pollinated chasmogamous flowers had equivalent germination rates and produced plants of equal size and fecundity. This suggests that the outbred progeny from chasmogamous flowers have no advantage over the inbred progeny from aerial cleistogamous flowers.     

The histogenesis of somaclones from tomato (Lycopersicon esculentum Mill.) cotyledons

Summary A histological study ofin vitro cultured cotyledonary expiants of tomato (Lycopersicon esculentum) was performed in order to determine the site (differentiated tissue or developing callus) and the mode of plant regeneration.Results have shown that callus develops at the excision sites of cotyledonary expiants and that shoots are formed exclusively within the unorganized callus: excision areas are the only morphogenetic sites and the proximal excision is the preferred site for plant regeneration.Shoots differentiate by organogenesis within the superficial region of the callus. Few neocambial cells cooperate in the neoformation. Origin from a single cell is highly unlikely since rarely observed single activated cells never developed into shoots.Regenerated plants may be chimeras if invitro culture induces genetic diversity in the initial cells.Abbreviations IAA Indole-3-acetic acid - c callus - d vegetative dome - s shoot - ad adaxial - ab abaxial - t tracheid - p parenchyma - S sieve tube     

Präadaptation, Wirtskreiserweiterung and Parallel-Cladogenese in der Evolution von phytophagen Insekten1, 2

Preadaptation, host shifts and parallel cladogenesis in the evolution of phytophagous insects In this contribution we investigate the possibilities to apply concepts developed for the evolution of animal parasites to insect-plant systems. We compare host parasite systems in animals with plant-herbivore systems and list similarities and differences. The terms preadaptation, predisposition, expansion and contraction of host ranges, and parallel cladogenesis are discussed. We enumerate general preadaptations for the evolution of herbivory in insects and preadaptations for shifts between herbivory and entomophagy. Examples are given for expansions of host ranges based on phytochemical or structural characters of host plants. Cases of parallel cladogenesis in herbivoreparasitoid systems and plant-herbivore systems are compiled from the literature. An analysis of the insect fauna of the “thistles” (Cynaroideae) in the Palearctic and Nearctic demonstrates the importance of the evolutionary history of the plant taxa and of the existence of preadapted pools of herbivores for the evolution of guilds of specialized herbivores. The members of the Curculionid taxon Cleoninae provide examples for multiple colonizations and radiations of herbivores on the Cynaroideae. The taxonomic and biological relationships of the weevil genera Rhinocyllus, Bangasternus and Larinus which exploit the flower heads of Cynaroideae, can be interpreted as result of a basic parallel cladogenesis between herbivore and host. A gelelectrophoretic analysis of Larinus spp. supports this hypothesis.     

不同季节银木叶精油化学成分的研究

用毛细管气相色谱-质谱-计算机联用技术、毛细管气相色谱双柱保留指数法和双柱标准品叠加法分析了不同季节银木叶精油化学成分。从分离出来的207—250个色谱峰中,初步鉴定出59个成分,被鉴定成分的总量占精油总组成的94.45—98.92%,其主要成分随采油季节不同而有所不同。     

Gaps in the canopy: the missing dimension in vegetation dynamics

Canopy gaps are important as entry points for new genotypes and new species into many types of vegetation, yet little is known about them in any type of vegetation but forests. Forest gaps are too large for manipulative experiments to be readily undertaken, and hitherto grassland gaps have been too small to be easily mapped. Preliminary results from mapping small (>1 cm) grassland gaps with a new fibre-optic device suggest that experiments need to be performed at a smaller physical scale than has hitherto been achieved.