Towards a theory of the evolution of butterfly colour patterns under directional and disruptive selection

Two general models for the transspecific evolution of butterfly colour patterns are advanced: directional selection acting equally on both sexes, and disruptive selection involving periods of polymorphism. To consider possible outcomes of me latter process, a morphism notation based on an integrated classification for polymorphism and sexual dimorphism is developed. This notation is used to examine the properties of all morphism transformations possible from the minimal expressions of the nine morphism categories, as reached through defined minimum step changes. The significance of such pathway models is analysed in terms of general properties of butterfly polymorphism. The potential use of pathway models in evolutionary studies is briefly discussed, mainly with respect to phylogenetics, and ideas on the evolution of genetic dominance.     

Crypsis in a heterogeneous environment: relationships between changeable polymorphic colour patterns and behaviour in a galaxiid fish

1. The ability to achieve optimal camouflage varies between microhabitats in heterogeneous environments, potentially restricting individuals to a single habitat or imposing a compromise on crypsis to match several habitats. However, animals may exhibit morphological and behavioural attributes that enhance crypsis in different habitats. 2. We used an undescribed fish species, Galaxias‘nebula’, to investigate two objectives. First, we examined two potential methods of enhancing crypsis: change in colour pattern and selection of a suitable background. Second, we characterised the colour pattern of this unstudied fish and assessed its capacity for crypsis. 3. No background selection was apparent but the area of dark pigment expressed varied between backgrounds, which may negate the requirement to be choosy about habitats. The capacity to change colour and selection of a background that maximises crypsis are most likely separate, non‐mutually exclusive strategies. 4. Galaxias‘nebula’ exhibits polymorphic, non‐interchangeable colour patterns that have elements of both background pattern matching and disruptive colouration. This, coupled with habitat characteristics, suggests a combination of generalist and specialist strategies of habitat use. The fish’s camouflage strategy and air‐breathing ability may be key to survival under increasing pressure from habitat degradation and invasive predators.     

Contributions to the systematic position of Hydrolea (Hydroleaceae) based on floral development

In the flower of Hydrolea palustris, unusually orientated with one sepal abaxially, organogenesis starts in following sequence: five sepals (2/5 sequence), five simultaneously initiated alternating petals, five episepalous stamens, two (seldom three) carpels forming a coenocarpous septate gynoecium. The two carpels are orientated rather in the diagonal floral plane than in the median one. Petal primordia fuse very late by forming interprimordial bridges (late sympetaly!). Many ovules develop on considerably widened placentas. On the very basis of the superior ovary a five-humped nectary disk is formed.Within Solanales (APG II 2003) late sympetaly, an intrastaminal disk and a 2-carpellate, septate, superior ovary are found in Hydroleaceae, Convolvulaceae, and Solanaceae. Enlarged axile placentas characterize Hydrolea, Solanaceae, and Sphenocleaceae but Sphenocleaceae differ considerably by early sympetaly. Montiniaceae differ by having a choripetalous corolla. Nearly diagonal orientation of the carpels seems to relate Hydrolea close to Solanaceae, but the orientation of the calyx is different.     

The Amino Acid Content in Gamma-irradiated Rice†

High phosphate accumulating bacteria were isolated by autoradiography. One isoate, Arthrobacter globiformis PAB-6 accumulated phosphate intracellularly at 20% of dry cell mass in a simple synthetic medium. This amount was 3~7 times higher than type cultures examined. Almost no phosphate was released into the medium after cessation of growth. Fifty percent of total intracellular phosphate was fractionated as nucleic acids, while 20% each was recovered from cold PCA soluble fractions and polyphosphate fractions. The large content of nucleic acids in this bacterium appeared due to increased RNA content, specifically 4 S RNA fraction.     

Effects of hatchling body colour and rearing density on body colouration in last-stadium nymphs of the desert locust, Schistocerca gregaria

Abstract.  The influences of hatchling character and rearing density on body colour at the last-nymphal stadium are investigated for the desert locust, Schistocerca gregaria . Hatchlings are divided into five groups based on the darkness of the body colour and reared either under isolated or crowded conditions. Two types of body colour variation at the last-nymphal stadium are separately analysed (i.e. the background colour and black patterns). Under isolated conditions, the background body colour is either greenish or brownish. Most individuals are greenish and the highest percentage of brownish insects is obtained from hatchlings with the darkest body colour. Under crowded conditions, the background colour is yellow or orange and the percentage of yellowish nymphs tends to decrease when they are darker at hatching. The intensity of black patterns differs depending on the body colour at hatching and subsequent rearing density. Most isolated-reared nymphs exhibit few or no black patterns but nymphs with some black patterns also appear, particularly among those that had been dark at hatching. Under crowded conditions, the black patterns become more intense when they are darker at hatching. Therefore, last-stadium nymphs with typical solitarious or gregarious body colouration appear when they have the phase-specific body colouration at hatching as well. The present results demonstrate that both body colour at hatching and rearing density during nymphal development influence body colouration at the last-nymphal stadium.     

Detection of a natural point mutation in Potato virus A that overcomes resistance to vascular movement in Nicandra physaloides., and studies on seed-transmissibility of the mutant virus

Isolate M of Potato virus A (PVA‐M; genus Potyvirus) is avirulent in Nicandra physaloides L. (family Solanaceae). The inoculated leaves are infected but no systemic infection is observed. Forty plants of ‘Black Pod’ (BP) and ‘Black Pod Alba’ (BPA), two variants of N. physaloides described in this study, were inoculated with PVA‐M. Two plants of BP and one plant of BPA were systemically infected. Mosaic, blistering and dark green islands developed on the systemically infected leaves, and flowers showed colour‐break symptoms. PVAprogeny were sequence‐characterised for the 6K2 protein and viral genome‐linked protein (VPg) encoding regions known to control the long distance movement of PVA in N. physaloides. All virus progeny (designated as PVA‐Mm) in the systemically infected leaves of the plants inoculated with PVA‐M contained only a single amino acid substitution (Vail 16Met) in the central part of VPg due to a nucleotide substitution G6033A, as compared to PVA‐M. Other PVA isolates that infected N. physaloides systemically also contained Metll6 in VPg. In a previous study using chimeric viruses, Metl16 in VPg was shown to be a major determinant for vascular movement of PVA in N. physaloides, and this study reveals that the mutation for Metl16 can occur in vivo during replication of the avirulent PVA‐M in infected plants. Immunolocalisation studies on BP and BPA plants showed that the pods (berries) and seed coat contained PVA‐Mm in the developing seeds, but no virus was detected in embryons. Up to 27% of the mature seeds contained PVA‐Mm but no transmission to seedlings was observed in a total of 450 seeds tested, and no test plants were infected following mechanical inoculation with extracts prepared from the seeds.     

Location and distribution of symbiotic bacteria during floral development in Ardisia crispa

Abstract. The location and distribution of symbiotic bacteria during floral development in Ardisia crispa (Thunb.) A.DC., a species characterized by bacterial leaf nodules, has been studied using light, scanning and transmission electron microscopy. During early floral development, bacteria in mucilage derived from host plant trichomes, become enclosed in a small conical chamber on top of the placenta, as a result of the closure and fusion of the carpel initials. The placental epidermal cells, which appear to be secretory in nature, become detached apically in places forming a network of grooves which traverse the placental surface. The symbiotic bacteria are preferentially located in these grooves. As growth and development of the placenta proceed, the grooves widen and deepen to form channels. The cells lining these channels secrete a mucilaginous material. The network of channels covers the entire placental surface and terminates at the placental margins surrounding the ovules. Bacteria are found within the channels, at the ends of the channels near the margin of the placenta, on the surface of the ovules and in the micropyle. It is suggested that these mucilage-filled channels are responsible for, and a prerequisite of, ensuring that the bacterial partner is efficiently transmitted from one host generation to the next by providing a mechanism by which the bacteria arc accurately placed within the developing seed.     

Flower change in Oenothera drummondii Hooker as a response to pollinators' visits

Flower change in Oenothera drummondii Hooker as a response to pollinators' visits. The colour and shape of flowers of Oenothera drummondii change owing to senescence, pollination and/or nectar withdrawal. This phenomenon is interpreted as a signal emitted by the plant to 'inform' the potential pollinator of its new status as a rewardless flower. This method of signalling might be important for the pollinators in order to save energy in seeking the correct flowers and for the plant to ensure visits to those flowers that have not yet been visited.