The adaptive significance of amphistomatic leaves

Abstract A clear correlation between the presence of stomata on both surfaces and factors such as habitat, growth form, and physiology has yet to emerge in the literature. However, certain loose trends with these factors are evident, and these are reviewed along with evidence for hypostomaty as the primitive form. It is proposed that the effect of developing stomata on the upper surface as well as the lower is to increase maximum leaf conductance to CO₂. Plants with a high photosynthetic capacity, living in full-sun environments, and experiencing rapidly fluctuating or continuously available soil water (as opposed to seasonal or long-term soil water depletion), are identified as deriving an adaptive advantage from a high maximum leaf conductance. The correlation between groups of plants fitting the above conditions and those noted to be amphistomatic is remarkable. Plants not fitting the conditions are found to be largely hypostomatic.     

Behaviour of the systemic nematicide oxamyl in plants in relation to control of invasion and development of Meloidogyne incognita

A single foliar application of oxamyl (12.5 μg) in acetone significantly reduced invasion of cucumber seedlings by Meloidogyne incognita juveniles for at least 21 days but did not affect the early stages of development of juveniles which had already invaded the roots. In contrast, application of oxamyl to the roots significantly reduced both invasion and development of juveniles. Concurrent studies using radiolabelled oxamyl showed that the amount of toxicant in the roots after 3 days was 13 times greater following root application than after foliar treatment. It is probable that oxamyl concentrates at the sites of nematode attack as an overall concentration of only 3 ng oxamyl g^-1 root was sufficient to prevent invasion. Much greater concentrations than this were required to affect the nematode in vitro. Oxamyl appeared to be lost from the roots into the soil principally in the form of its non-toxic oxime and it is suggested that the site of action following foliar application is at the root surface or outer cortex. Studies on the invasion behaviour of M. incognita juveniles on agar showed that the action of oxamyl had a sensory component.     

A New Species of Kudoa (Myxosporidea: Chloromyxidae) from the Spot,Leiostomus xanthurus Lacépède,in Clear Lake,Texas*

SYNOPSIS. Kudoa branchiata sp. n. (Myxosporidea: Chloromyxidae) is described from the gills of the marine sciaenid fish, Leiostomus xanthurus Lacépède, from Clear Lake, Texas. Twelve of the 429 hosts examined from 10 September 1970 to 28 April 1971, were infected. Eight of the 12 infected fish were collected in February and March 1971—a period during which only 13% of the total host sample was taken. The mean total length of infected hosts was 149 mm, with a range of 112–185 mm. The mean number of myxosporidean cysts per infected host was 3.5, with a range of 1–11.     

Ovule abortion in white clover (Trifolium repens L.)

Plants of white clover ( Trifolium repens L.) cv. Olwen were grown in an open glasshouse maintained at a mean temperature of 20^oC and ovule growth and seed production measured. Differences in the rate of growth of ovules within ovaries were observed as early as 2 days after pollination. Ovules reached a maximum size after 8 days with the smallest only half the size of the largest. After 8 days, the smallest ovules became flaccid and shrivelled. Ovule position within the ovary had little effect on the frequency of seed set and although there was an apparently higher probability that central ovules produced a seed than those nearer the peduncle or style this was not statistically significant. Inflorescence position and floret position on the inflorescence had a significant effect on the number of seeds per floret and seed weight; the first formed inflorescences and the first florets to be pollinated on each inflorescence had more seeds per floret and heavier seeds and fewer florets with no seed than later pollinated florets. There were also differences between florets within the same whorl. The role of a number of factors which may influence floret site utilisation are discussed.     

A molecular phylogeny for the pyraloid moths (Lepidoptera: Pyraloidea) and its implications for higher‐level classification

Pyraloidea, one of the largest superfamilies of Lepidoptera, comprise more than 15 684 described species worldwide, including important pests, biological control agents and experimental models. Understanding of pyraloid phylogeny, the basis for a predictive classification, is currently provisional. We present the most detailed molecular estimate of relationships to date across the subfamilies of Pyraloidea, and assess its concordance with previous morphology‐based hypotheses. We sequenced up to five nuclear genes, totalling 6633 bp, in each of 42 pyraloids spanning both families and 18 of the 21 subfamilies, plus up to 14 additional genes, for a total of 14 826 bp, in 21 of those pyraloids plus all 24 outgroups. Maximum likelihood analyses yield trees that, within Pyraloidea, differ little among datasets and character treatments and are strongly supported at all levels of divergence (83% of nodes with bootstrap ≥80%). Subfamily relationships within Pyralidae, all very strongly supported (>90% bootstrap), differ only slightly from a previous morphological analysis, and can be summarized as Galleriinae + Chrysauginae (Phycitinae (Pyralinae + Epipaschiinae)). The main remaining uncertainty involves Chrysauginae, of which the poorly studied Australian genera may constitute the basal elements of Galleriinae + Chrysauginae or even of Pyralidae. In Crambidae the molecular phylogeny is also strongly supported, but conflicts with most previous hypotheses. Among the newly proposed groupings are a ‘wet‐habitat clade’ comprising Acentropinae + Schoenobiinae + Midilinae, and a provisional ‘mustard oil clade’ containing Glaphyriinae, Evergestinae and Noordinae, in which the majority of described larvae feed on Brassicales. Within this clade a previous synonymy of Dichogaminae with the Glaphyriinae is supported. Evergestinae syn. n. and Noordinae syn. n. are here newly synonymized with Glaphyriinae, which appear to be paraphyletic with respect to both. Pyraustinae and Spilomelinae as sampled here are each monophyletic but form a sister group pair. Wurthiinae n. syn. , comprising the single genus Niphopyralis Hampson, which lives in ant nests, are closely related to, apparently subordinate within, and here newly synonymized with, Spilomelinae syn. n.     

The diversity and biogeography of koa-finches (Drepanidini: Rhodacanthis), with descriptions of two new species

All known populations of koa-finches, genus Rhodacanthis , became extinct in the Holocene epoch. Two new species are described here from Quaternary fossil sites in the Hawaiian Islands. One new species, from Kauai and Maui, is roughly the size of the historically known greater koa-finch ( R. palmeri ) but differs in having a more robust skull and in bill morphology. The second new species, from Oahu and Maui, is similar in size to the lesser koa-finch ( R. flaviceps ) but closer to R. palmeri in qualitative osteological traits. The two species of koa-finches known historically from the island of Hawaii are distinct in osteology from the fossil koa-finches on the older Hawaiian islands, indicating that at least two of the four known speciation events in the genus took place within approximately the past 500 kyr. However, the similarity of maxillae from Pleistocene and Holocene sites on Oahu suggests that the Oahu population maintained morphological stasis through the climate changes of the late Quaternary. The evidence that speciation occurred on the youngest island in the archipelago suggests that the process of community assembly on newly emergent Hawaiian landscapes was a stimulus to evolutionary diversification in Rhodacanthis .  © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society , 2005, 144 , 527–541.     

Phylogenetic relationships in brown argus butterflies (Lepidoptera: Lycaenidae: Aricia) from northwestern Europe

Lycaenid butterflies of the Aricia agestisartaxerxes complex pose an unresolved taxonomic and conservation problem in northwestern Europe. Two key issues require resolution: (i) how many species of Aricia occur in northwestern Europe and what are their distributions?; (ii) how is the morphological variation observed in northwestern Europe best explained? We investigated phylogenetic relationships and phylogeographic patterns in this species group using mitochondrial and nuclear markers in comparison with morphological variation. A 325 bp fragment of the mitochondrial cytochromeb gene was sequenced from 179 individuals representing 18 populations from the UK and Scandinavia. Seventeen enzymecoding loci were analysed from 538 individuals from the same populations. Highly congruent phylogenies between mitochondrial and allozyme markers demonstrate that the sample is composed of two closely related species, A. agestis and A. artaxerxes. Both marker types also suggest that Scottish and northern Scandinavian A. artaxerxes populations are conspecific, and consequently do not support the endemic status of A. artaxerxes in the UK. The subspecies division of British populations of A. artaxerxes is also not supported by phylogenetic analyses. Allozyme and mitochondrial analyses cluster two populations from the Peak District, UK, differently. The former suggests that they are A. artaxerxes whilst the latter suggests they are A. agestis. Further research is required to find the reason for this disagreement, which could be associated with the different dynamics of nuclear and mitochondrial genes across a hybrid zone between the two species. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 2002, 75 , 27–37.     

Evidence from double infestations for the specific status of human head lice and body lice (Anoplura)

Abstract Samples of head lice and body lice obtained from Ethiopians suffering from double infestations were mounted onto microscope slides and measured. The mean length of body lice (♀ 4.4mm; ♂ 3.8mm) was greater than that of head lice (♀ 3.5 mm; ♂ 2.9mm), but the best discriminant was the length of the tibia of the middle leg (♀ 425/296 μ♂421/291 μ). No intermediate specimens were found in these double infestations, although intermediates can can be produced experimentally by cross-mating. Since populations of head lice and body lice remain distinct it is concluded that they represent two distinct species, Pediculus capitis De Geer and P. humanus Linneaus.     

Spatial heterogeneity in soil nutrient supply modulates nutrient and biomass responses to multiple global change drivers in model grassland communities

Changes in the atmospheric concentration of carbon dioxide ([CO₂]), nutrient availability and biotic diversity are three major drivers of the ongoing global change impacting terrestrial ecosystems worldwide. While it is well established that soil nutrient heterogeneity exerts a strong influence on the development of plant individuals and communities, it is virtually unknown how nutrient heterogeneity and global change drivers interact to affect plant performance and ecosystem functioning. We conducted a microcosm experiment to evaluate the effect of simultaneous changes in [CO₂], nutrient heterogeneity (NH), nutrient availability (NA) and species evenness on the biomass and nutrient uptake patterns of assemblages formed by Lolium perenne, Plantago lanceolata and Holcus lanatus. When the nutrients were heterogeneously supplied, assemblages exhibited precise root foraging patterns, and had higher above‐ and belowground biomass (average increases of 32% and 29% for above‐ and belowground biomass, respectively). Nutrient heterogeneity also modulated the effects of NA on biomass production, complementarity in nitrogen uptake and below: aboveground ratio, as well as those of [CO₂] on the nutrient use efficiency at the assemblage level. Our results show that nutrient heterogeneity has the potential to influence the response of plant assemblages to simultaneous changes in [CO₂], nutrient availability and biotic diversity, and suggest that it is an important environmental factor to interpret and assess plant assemblage responses to global change.