A new species of Mimulus endemic to copper mines in California

MACNAIR, M. R., 1989. A new species of Mimulus endemic to copper mines in California . The distribution and morphology of Mimulus cupriphilus , a new species restricted to two small copper mines in Calaveras County, California, is described. A comparison of flowers collected in the wild of M. guttatus and the new taxon shows that they differ considerably. These two species and three other species from the M. guttatus complex, M. nasutus, M. laciniatus and M. nudatus were grown in a glasshouse and compared. The five species were all clearly distinct. The distribution of M. cupriphilus is consistent with it having evolved comparatively recently on one or both of the two copper mines on which it is found.     

Mobilization of Nitrogen in Fruiting Plants of a Cultivar of Cowpea

Patterns of flow of nitrogen were constructed for the post-anthesisdevelopment of symbiotically-dependent cowpea (Vigna unguiculataWalp. cv. Vita 3-Rhizobium CB756). Nitrogen fixed after floweringcontributed 40% of the fruits' total intake of N, mobilizationof N fixed before flowering the remaining 60%. Leaflets, nodulatedroot, stem plus petioles, and peduncles contributed mobilizedN in the approximate proportions 5: 2: 1: 1 respectively. Eachfruit drew on all available current sources of N, but N fromleaves was distributed preferentially to closest fruit(s), andlower fruits monopolized the N exported from nodulated rootsduring late fruiting. Rates of nitrogen fixation declined parallel with decreasingnet photosynthesis of shoots. Leaflets at upper reproductivenodes mobilized 70–77% of their N and declined steeplyin net photosynthesis rate per unit chlorophyll or per unitribulose-l, 5-bisphosphate carboxylase (RuBPCase)² before abscisingduring mid- to late fruiting, whereas leaflets at lower vegetativenodes (1–3) mostly failed to abscise, lost 44–57%of their N and maintained photosynthetic activity throughoutfruiting. Peptide hydrolase activity was examined in extracts of leaflets,roots and nodules, by autodigestion of extracts, or in assaysusing bovine haemoglobin and purified RuBPCase isolated fromcowpea as substrates. Hydrolase activities during fruiting werebroadly related to N loss from plant organs, but asynchronyin peaks of activity against different protein substrates indicateddistinct groups of hydrolases within single organs. Hydrolaseactivity of leaflet extracts against RuBPCase was highly andpositively correlated with in vivo rates of loss of RuBPCasefrom the same leaflets, and preferential degradation of thisprotein occurred during leaflet senescence. Key words: Nitrogen, Mobilization: Cowpea     

Self-thinning in Trifolium subterraneum not affected by cultivar shape

As it was thought that self-thinning in crowded plant populations might be influenced by the shape of the plants involved, self-thinning was examined in five cultivars of Trifolium subterraneum. The height of these cultivars is fixed after early growth, being determined mainly by petiole length which itself varies between cultivars. No detectable differences between cultivars were found, and it is argued that only wore considerable differences in shape than those reported here would have detectable effects. When plants can only grow radially but not in height, it is to be expected that log-log self-thinning curves would have a slope of -1, but these Trifolium populations had the – 3/2 slope usually found for species which exhibit continuous growth in height. This finding remains unexplained.     

Changes in sensitivity of Amaranthus retrof/exus L. seeds to ethylene during preincubation. I. Constant temperatures

Abstract. Germination responses of redroot pigweed ( Amaranthus retroflexus L.) seeds to ethylene were determined at 25, 30, 35, or 40° C after preincubation at various temperatures (15–35° C) for different periods (0.5–32 d). After 7 d preincubation, seeds showed a log-linear germination response to ethylene concentration in most of the temperature treatments. Sensitivity to ethylene increased with longer preincubation; response thresholds of 0.03−0.09 cm³ m⁻³ were observed after 32 d, compared to 0.18−1.6 cm³ m⁻³ after 7 d of preincubation. Preincubation at 15 or 20° C generally enhanced germinability, whereas 25 or 30° C produced secondary dormancy, which was readily broken with ethylene. Temperature during preincubation also significantly influenced the slope of the dose-response curve. The responses of preincubated redroot pigweed seeds to ethylene suggested that, in the field, seeds would probably not lose their sensitivity to this gas during prolonged burial in soil.     

Resistance of Calves to Reinfection with Eimeria bovis

SYNOPSIS. An immunity to reinfection with E. bovis was demonstrated in 3 experiments involving 60 calves. This immunity develops rapidly, as indicated by resistance to a challenge given 14 days after the immunizing inoculation. In 3 groups of 3 to 6 young calves each, immunity was still present to a moderate degree 2 to 3 months after inoculation; in one group of 5 animals about a year old there was apparently a high degree of immunity about 7 months after the last inoculation. In one experiment an immunizing inoculum of 10,000 oöcysts did not produce as much immunity as 50,000 oöcysts. In 2 experiments there appeared to be little difference in the immunity produced by a single inoculation of 50,000 as compared with 100,000 oöcysts, but inoculation with 100,000 oöcysts, resulted in substantially longer and more severe illness than 50,000 oöcysts. There appeared to be no appreciable difference in clinical symptoms or development of immunity between calves given a single immunizing inoculum and those given the same number of oöcysts in 5 equal inocula on successive days. Treatment with sulfamethazine and sulfamerazine (Merameth) 13 to 15 days after inoculation alleviated the clinical symptoms of coccidiosis without interfering appreciably with the development of immunity. In one experiment with 7 calves, no beneficial effect was noted from 1 or 2 transfusions of 500 ml. of plasma and leucocytes from immune calves into 4 calves 1 and 12 days or 11 days after a challenge inoculation.     

Aspects of the dynamics of the seed-banks and seedling populations of Acacia victoriae and Cassia spp. in arid western New South Wales

Acacia victoriae, Cassia nemophila and C. phyllodinea are shrubs which occur throughout large areas of arid and semi-arid Australia. This paper examines aspects of the dynamics of the seed-banks and seedling populations of these plants to determine their influence upon recruitment frequency. Seed-banks in the soil are large, ranging from 50 to 3900 seeds m^-2for A. victoriae and from 5 to 400 seeds m^-2for Cassia spp. A large proportion (ca. 80%) of these seeds are viable. Seedling densities soon after emergence range up to 25.7 m^-2for A. victoriae and up to 21.7 m^-2for Cassia spp. Any individual cohort of seedlings represents only a small proportion (< 6%) of the total seed-bank. Most viable seeds fail to germinate even when adequate moisture is available. Seedling mortality rates are high (ca. 100%) during the first 12 months after germination. If recruitment of these shrubs is intermittent, it is most likely a result of low seedling survival rather than infrequent germination.     

Opposing effects of spring defoliation on late season oak caterpillars

ABSTRACT. 1. The pedunculate oak, Quercus rohur L., suffers high annual levels of spring defoliation in Wytham Woods. near Oxford.
2. This spring defoliation affects late season caterpillars through a variety of damage-induced changes in the leaves.
3. Diurnea fagella (D. & S.), one of the commonest late season caterpillars, shows reduced larval survival and pupal weight on regrowth foliage when compared to undamaged primary foliage.
4. D. fagella also suffer higher larval mortality on naturally damaged primary foliage than they do on undamaged foliage.
5. Despite this, the three commonest late season caterpillar species are more abundant on damaged trees than undamaged ones. and their distributions are biased towards damaged leaves within the canopy.
6. Other factors that may be more important than leaf damage in determining the distribution and abundance of late season caterpillars are discussed. D.fagella larvae spin their larval refuges more rapidly on damaged than undamaged foliage, and this may reduce mortality by natural enemies, or ameliorate adverse effects of weather.     

The Red Queen Visits Sage Grouse Leks

Coevolution between parasites and host is a sufficient althoughnot necessary condition for the evolution of secondary sexualcharacteristics. I review evidence supporting the role of parasitesin the maintenance of lek behavior in Sage Grouse (Centrocercusurophasianus). Males bearing avianmalaria (Plasmodium pediocetii)or lice (Lagopoecus gibsoni or Goniodes centrocerci) have significantlylower reproductive success than noninfected males. Malaria-infectedmales attend leks significantly less frequently and lek attendanceis highly correlated with male reproductive success. Inaddition,males with malaria secured copulations later in the breedingseason with hens that wereyounger, in poorer condition, andless successful than mates of malaria-free males. Lice createhematomas on the air sacs of males which females can detectto avoid lousy males. Results of our field studies are reinforcedby experiments; captive males given antibiotics to reduce parasiteloads are chosen more often by females in arena trials. Ourresults lend empirical support for Hamilton and Zuk's (1982)interpretation of the RedQueen's hypothesis, although many unknownsremain in our understanding of the interaction between parasitesand Sage Grouse.     

Conservation genetics of an arctic species, Saxifraga rivularis L., in Britain

Genetic diversity in British populations of Saxifraga rivularis L. (Saxifragaceae) was assessed using isozymes, RAPDs, inter-SSRs and RFLPs of two non-coding chloroplast DNA regions. Low levels of variation were detected: only five molecular phenotypes were recovered, polymorphic for a single RAPD band and Pgd enzyme phenotype. The problem of drawing conservation recommendations from studies that show low levels of marker variation is discussed, and the importance of recognizing the limits of molecular genetic data in conservation biology is emphasized.     

Description of a new Eocene osteoglossid fish and additional information on †Singida jacksonoides Greenwood and Patterson, 1967 (Osteoglossomorpha), with an assessment of their phylogenetic relationships

A new genus and species of osteoglossomorph fish is described from the Eocene Mahenge site in north central Tanzania. The new species is sympatric with the previously described osteoglossomorph † Singida jacksonoides , but is easily distinguished from it by the presence in the new species of teeth on the jaws and entopterygoid. The new species shares characters with the Heterotidinae, such as the two arms of the preopercle being of similar length and the posterior end of the maxilla lying on the dentary, and other characters with the Osteoglossinae (including † Phareodus ), for example the enlarged pectoral fin ray and the shape of the opercular bone. New specimens of † S. jacksonoides also have been recovered from the site, providing more information on the osteology of this fish. The relationships of these two Mahenge osteoglossomorphs are assessed, with both fishes placed within the Osteoglossidae, but of uncertain position in the family. Addition of the new species to previous cladistic data sets, and the revised information for † S. jacksonoides , causes the subfamily Osteoglossinae to be nonmonophyletic.  © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society, 2005, 144 , 213–228.