Impact of density of Aphis craccivora (Aphididae) on growth and yield of susceptible and resistant cowpea cultivars

Impact of initial density of cowpea aphid Aphis craccivora Koch (Aphididae) at infestation on the growth and yield of aphid-susceptible cowpea cultivar ICV-1 and aphid-resistant cultivar ICV-12, was investigated. Plants at the seedling, flowering and podding stages of development were infested with five aphid densities consisting of 0, 2, 5, 10 and. 20 aphids per plant and maintained for 22 days. Extended leaf heights of plants and aphid counts were recorded at 7, 12, 17 and 22 days after infestation. Two crop growth parameters (biomass duration and leaf area duration), and two plant yield parameters (number of pods per plant and number of seeds per pod) were recorded. Due to the occurrence of parthenogenesis and changes in population dynamics during infestations, aphid densities were converted into cumulative cowpea aphid-days, to facilitate data analyses and interpretation. ANOVA indicated that there was significant (P=s 0.05) difference in aphid-day accumulations between the two cultivars when infested at the seedling stage. Accumulations on cv. ICV-1 were greater than on cv. ICV-12. However, no such differences between the cultivars were detected when plants were infested at flowering and podding stages. Therefore, the seedling stage was used for comparisons of the impact of cowpea aphid-days on the growth and yield parameters of the two cultivars. At the 95% confidence intervals, ICV-12 plants were consistently taller than ICV-1 plants. Infested ICV-1 seedlings showed stunting and other growth deformities which were not observed on ICV-12 plants. Regression analyses revealed substantial reductions in the growth and yield parameters of ICV-1 relative to ICV-12. Overall, cowpea aphid-days provided a convenient and reliable method for studying the aphid population dynamics and the subsequent impact on plant growth and yield performance.     

Polyphyly of the genus Apalis and a new generic name for the species pulchra and ruwenzorii

The genus Apalis is a member of the African forest warblers clade of the Cisticolidae. In view of its morphological diversity, it was suggested that this genus needs a taxonomic revaluation. For this, we sequenced a nuclear intron (myoglobin intron 2) and two mitochondrial protein‐coding genes (ND2 and ND3). The 2016 bp of sequence data obtained were aligned and subjected to parsimony, maximum likelihood and Bayesian inference. All three genes strongly reject the monophyly of Apalis but support the placing of all apalises within a broader clade of forest cisticolids which also includes Urolais. Within this forest clade, a subclade is defined which includes the genera Urolais, Schistolais and a well‐supported clade comprising three afromontane species, the Black‐collared Apalis Apalis pulchra, the Ruwenzori Apalis Apalis ruwenzorii and the African Tailorbird Artisornis. This subclade is sister to other members of Apalis, including the type species of the genus the Bar‐throated Apalis Apalis thoracica. A new generic name, Oreolais, is suggested for the Black‐collared and Ruwenzori Apalises.     

The potential implications of rainforest history, hybridization, and climate change on the phylogenetics of a rare genus of herbs Romnalda (Dasypogonaceae) from New Guinea and Australia

There are many genera shared between Australian and Papua New Guinean rainforests. Species in the rare rainforest herbaceous genus Romnalda have a relictual and disjunct distribution within the major rainforest blocs of southern Queensland, north Queensland, and New Guinea. There are only four species in this genus: R. strobilacea , R. grallata , and R. sp. 'Cooper Ck' from Australia, and R. papuana from New Guinea. The Australian species have restricted distributions and high conservation status. Allozymes were used to study the genetic variation and distinctiveness of all four species. Genetic diversity varied significantly amongst the four species. The species in the centre of the genus distribution contained the highest genetic diversity, regardless of rarity. The undescribed R. sp. 'Cooper Ck' was identified as a clearly distinct species with morphological affinities to R. papuana , but genetic affinities to R. grallata. The study showed that, where the distributions of R. grallata and R. sp. 'Cooper Ck' overlapped, there was evidence of hybridization. Reproductive participation within populations was typically low with limited flowering synchrony. Populations of all four species were inbred, but higher levels of inbreeding were not correlated with lower genetic diversity. The timing of flowering appeared to be determined by climate. Altitudinal variation in phenological timing in R. sp. 'Cooper Ck' has led to genetic isolation within the species, but has also limited its genetic introgression with the co-occurring R. grallata . © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 157 , 455–474.