Climatic sensitivity of species’ vegetative and reproductive phenology in a Hawaiian montane wet forest

Understanding how tropical tree phenology (i.e., the timing and amount of seed and leaf production) responds to climate is vital for predicting how climate change may alter ecological functioning of tropical forests. We examined the effects of temperature, rainfall, and photosynthetically active radiation (PAR) on seed phenology of four dominant species and community-level leaf phenology in a montane wet forest on the island of Hawaiʻi using monthly data collected over ~ 6 years. We expected that species phenologies would be better explained by variation in temperature and PAR than rainfall because rainfall at this site is not limiting. The best-fit model for all four species included temperature, rainfall, and PAR. For three species, including two foundational species of Hawaiian forests (Acacia koa and Metrosideros polymorpha), seed production declined with increasing maximum temperatures and increased with rainfall. Relationships with PAR were the most variable across all four species. Community-level leaf litterfall decreased with minimum temperatures, increased with rainfall, and showed a peak at PAR of ~ 400 μmol/m²s⁻¹. There was considerable variation in monthly seed and leaf production not explained by climatic factors, and there was some evidence for a mediating effect of daylength. Thus, the impact of future climate change on this forest will depend on how climate change interacts with other factors such as daylength, biotic, and/or evolutionary constraints. Our results nonetheless provide insight into how climate change may affect different species in unique ways with potential consequences for shifts in species distributions and community composition.     

Evolutionary conservation of the chromosomal configuration and regulation of amylase genes among eight species of the Drosophila melanogaster species subgroup

Nuclear DNA was extracted from each of the eight species comprising the Drosophila melanogaster species subgroup. Southern hybridization of this DNA by using a molecular probe specific for the alpha-amylase coding region showed that the duplicated structure of the amylase locus, first found in D. melanogaster, is conserved among all species of the melanogaster subgroup. Evidence is also presented for the concerted evolution of the duplicated genes within each species. In addition, it is shown that the glucose repression of amylase gene expression, which has been extensively studied in D. melanogaster, is not confined to this species but occurs in all eight members of the species subgroup. Thus, both the duplicated gene structure and the glucose repression of Drosophila amylase gene activity are stable over extended periods of evolutionary time.      

Characteristics of dynamic postural reactions in the locust hindleg

Summary The use of the locust (Schistocerca americana) hindleg in postural control was examined in animals that stood on a repeatedly swayed vertical substrate. Myograms were recorded from leg muscles and the angle of the femoro-tibial joint was monitored photographically. Two discrete strategies were observed,; in compensatory reactions the hindleg was held in place, while in flexion reactions, the leg was moved, most often to complete flexion of the femoro-tibial joint. Tightly coupled, rhythmic bursting occurred in the flexor and levator muscles of the leg during compensatory reactions. Bursting was initiated repeatedly when the substrate was being pulled away from the animal. Bursting was correlated with subsequent decreases in the rate of change of the femorotibial joint angle. Compensatory and flexion reactions occurred preferentially in different ranges of joint angles: most often, compensatory reactions occurred in the midrange, while flexion reactions were elicited in the extremes of joint angle. These differences may be due to the mechanical advantages of the tibial muscles and the leg may be moved to full flexion because of a locking mechanism of the flexor muscle tendon. These reactions are compared with known reflexes of hindleg proprioceptors and contrasted with similar responses of vertebrates.     

The Molecular through Ecological Genetics of Abnormal Abdomen in DROSOPHILA MERCATORUM. I. Basic Genetics

The abnormal abdomen syndrome (aa) in Drosophila mercatorum is characterized by the persistence of juvenilized cuticle on the adult abdomen. The aa phenotype is shown to depend on at least two X-linked genetic elements that are about one map unit apart near the centromeric end of the X chromosome. These two genetic elements are necessary for aa expression; one behaves as a dominant element and the other as a recessive. Overlaying these genetic studies upon molecular work reported elsewhere, it is argued that the dominant element is the presence of a 5 kb insertion in a majority of the X-linked repeats coding for the 28S ribosomal RNA. The recessive element appears to be a locus controlling differential replication of noninserted over inserted 28S genes during polytenization. The aa syndrome requires both the presence of the inserted repeats and the failure to preferentially amplify noninserted repeats. Given the necessary X-linked elements for aa, a variety of modifiers are revealed. First, aa expression in males is Y-linked, apparently corresponding to a deletion of the 18S/28S rDNA gene cluster normally found on the Y. Moreover, all major autosomes can modify the penetrance of aa.     

Growth of Phytomonas serpens in a Defined Medium; Nutritional Requirements

ABSTRACT. Three strains of Phytomonas serpens two from tomatoes, Lycopersicon esculentum one from the insect Phtia picta (Hemiptera, Coreidae), were cultivated in a chemically defined medium developed from a defined medium for cultivating insect flagellates. Besides organic growth factors required by other insect trypanosomatids this flagellate requires, serine and inositol. Glutamine stimulates growth, and, surprisingly, does not require heme.     

Sequence variation in the outer-surface-protein genes of Borrelia burgdorferi

Borrelia burgdorferi is a spirochete pathogen transmitted among warm- blooded hosts by ixodid ticks. Frequency-dependent selection for variant outer-surface proteins might be expected to arise in this species, since rare variants are more likely to avoid immune surveillance in previously infected hosts. We sequenced the OspA and OspB genes of nine North American strains and compared them with nine strains previously described. For each gene, the mean number of synonymous substitutions per synonymous site and the mean number of nonsynonymous substitutions per nonsynonymous site show only a twofold excess of silent mutations. Synonymous rates vary widely along the OspB protein. Some regions show a significant excess of silent substitutions, while divergence in other regions is constrained by biased base composition or selection. The presence, in antigenically important regions of the protein, of significant variation among strains, as well as evidence for recombination among strains, should be considered in attempts to develop vaccines against this disease.      

ANTIVIRAL ACTIVITY OF CULTURED BLUE-GREEN ALGAE (CYANOPHYTA)1

Lipophilic and hydrophilic extracts from approximately 600 strains of cultured cyanophytes, representing some 300 species, were examined for antiviral activity against three pathogenic viruses. Approximately 10% of the cultures produced substances that caused significant reduction in cytopathic effect normally associated with viral infection. The screening program identified the order Chroococcales as commonly producing antiviral agents.     

Characterisation of a 34 kD protein from potato cyst nematodes, using monoclonal antibodies with potential for species diagnosis

Two monoclonal antibodies, which differentially recognise the two species of potato cyst nematodes (PCN), Globodera pallida and G. rostochiensis, are described. They have been shown to have potential for quantification of these two species, recognising proteins of the same molecular weight (34 kD) in both species. Further investigation showed these proteins to have isoelectric points at pH values of 5.7 in G. pallida and 5.9 in G. rostochiensis, in common with the proteins used by Fleming & Marks (1983) to differentiate the species of PCN. They are likely to be structurally very similar, with the same physiological function (and therefore similar concentrations) in the two species. In cross-reactivity tests with a wide range of soil nematode species, the antibodies reacted strongly only with species of the genus Globodera, and thereby confirmed their potential as the basis of a quantitative immunoassay likely to be useful in management of PCN populations.