Darkness visible: reflections on underground ecology

1 Soil science and ecology have developed independently, making it difficult for ecologists to contribute to urgent current debates on the destruction of the global soil resource and its key role in the global carbon cycle. Soils are believed to be exceptionally biodiverse parts of ecosystems, a view confirmed by recent data from the UK Soil Biodiversity Programme at Sourhope, Scotland, where high diversity was a characteristic of small organisms, but not of larger ones. Explaining this difference requires knowledge that we currently lack about the basic biology and biogeography of micro-organisms. 2 It seems inherently plausible that the high levels of biological diversity in soil play some part in determining the ability of soils to undertake ecosystem-level processes, such as carbon and mineral cycling. However, we lack conceptual models to address this issue, and debate about the role of biodiversity in ecosystem processes has centred around the concept of functional redundancy, and has consequently been largely semantic. More precise construction of our experimental questions is needed to advance understanding. 3 These issues are well illustrated by the fungi that form arbuscular mycorrhizas, the Glomeromycota. This ancient symbiosis of plants and fungi is responsible for phosphate uptake in most land plants, and the phylum is generally held to be species-poor and non-specific, with most members readily colonizing any plant species. Molecular techniques have shown both those assumptions to be unsafe, raising questions about what factors have promoted diversification in these fungi. One source of this genetic diversity may be functional diversity. 4 Specificity of the mycorrhizal interaction between plants and fungi would have important ecosystem consequences. One example would be in the control of invasiveness in introduced plant species: surprisingly, naturalized plant species in Britain are disproportionately from mycorrhizal families, suggesting that these fungi may play a role in assisting invasion. 5 What emerges from an attempt to relate biodiversity and ecosystem processes in soil is our extraordinary ignorance about the organisms involved. There are fundamental questions that are now answerable with new techniques and sufficient will, such as how biodiverse are natural soils? Do microbes have biogeography? Are there rare or even endangered microbes

The family Onchulidae: establishment of monophyly, rediagnosis, review and keys, with descriptions of three new species

This paper presents a complete overview and monophyletic classification of the family Onchulidae. Thefamily is reviewed and rediagnosed, with the presence of alternating discs of glandular and muscular tissue in the oesophagus the primary feature uniting taxa of the family. Under this definition, the genus Tobriloides Loof, 1973 — formerly Tobrilidae -- is included. The structure of the dorsal tooth and tail are the distinguishing features of two new subfamilies: Pseudonchulinae n. subfam. and Onchulinae n. subfam. The buccal armature other than the dorsal tooth is the defining characteristic of genera: the genus Paronchulus Altherr, 1972 is synonymized with Limonchulus Andrássy, 1963, and Cyathonchus Cobb, 1933 is treated as genus incertae sedis. Amended descriptions of all taxa are presented with a diagnostic key to subfamilies, genera and species in the family, a checklist of species and descriptions of three new species from moist tropical forest. Onchulus biannulatus sp. n. is characterised by its small body size, two prominent cuticular rings in the stoma, anterior amphid aperture, V’ =57- 65%, adult females with empty spermathecae, and absence of males. Onchulus microdontus sp. n. is characterised by its very small body size, lightly sclerotized dorsal stoma and relatively small dorsal tooth, anterior amphid aperture, a large value of De Man’s b and b’, V’ less than 57%, adult females with empty spermathecae, and males absent. Limonchulus denticulatus sp. n. is characterised by its small size, stoma lacking sclerotized rings, anterior amphid aperture, cervical papillae absent in females, and empty spermathecae.   En esta contribución se presenta una revisión completa y una clasificación monofilética de la familia Onchulidae. Se ofrece una nueva diagnosis sobre la base de la presencia de discos alternativos de tejido muscular y glandular en el esófago como rasgo primario que confiere unidad a los táxones de la familia. De acuerdo con este concepto, se incluye el género Tobriloides Loof, 1973, antes perteneciente a la familia Tobrilidae. La morfología del diente dorsal y de la cola son los rasgos que distinguen las dos nuevas subfamilias: Pseudonchulinae n. subfam. and Onchulinae n. subfam. La armadura bucal antes que el diente dorsal es el rasgo que diferencia los géneros: el género Paronchulus Altherr, 1972 se propone como sinónimo de Limonchulus Andrássy, 1963, and Cyathonchus Cobb, 1933 se considera un género incertae sedis. Se presentan diagnosis de todos los táxones, una clave para la identificación de subfamilias, géneros y especies pertencecientes a la familia, así como una lista de especies, y la descripción de tres nuevas especies procedentes del bosque tropical húmedo. Onchulus biannulatus sp. n. se caracteriza por tener tamaño corporal pequeño, dos anillos cuticulares promientes en el estoma, abertura del anfidio en posición anterior, V’ =57-65%, hembra adulta con espermatecas vacías, y macho ausente. Onchulus microdontus sp. n. se distingue por su tamaño corporal muy pequeño, parte dorsal del estoma débilmente esclerotizado y con diente dorsal pequeño, abertura del anfidio en posición anterior, valor alto de los índices b and b’, V’ menor que 57%, hembra adulta con espermatecas vacías y macho desconocido. Limonchulus denticulatus sp. n. se caracteriza por tener tamaño pequeño, estoma sin anillos esclerotizados, abertura del anfidio en posición anterior, papilas cervicales ausentes en la hembra, y espermatecas vacías

The history of plant and soil nematology in Australia and New Zealand, with particular reference to the contributions of six pioneering nematologists

The history of plant and soil nematology in Australia and New Zealand, with particular reference to the contributions of six pioneering nematologists G. R. Stirling A , E , G. W. Yeates B , K. Davies C and M. Hodda D A Biological Crop Protection Pty Ltd, 3601 Moggill Road, Moggill, Qld 4072, Australia. B Landcare Research, Private Bag 11052, Palmerston North 4442, New Zealand. C Plant and Food Science, Waite Campus, The University of Adelaide, PMB 1, Glen Osmond, SA 5064, Australia. D CSIRO Entomology, GPO Box 1700, Canberra, ACT 2601, Australia. E Corresponding author. Email: [email protected] Abstract In an era of rapid technological advancement, it is easy to overlook those who established the knowledge base that underpins today’s research programs. This paper traces the history of plant and soil nematology in Australia and New Zealand and recognises six pioneers who contributed significantly to its development, namely N. A. Cobb, R. C. Colbran, H. R. Wallace, A. F. Bird, J. M. Fisher and W. C. Clark. Collectively, these scientists described many unique and economically important nematodes, advanced our understanding of the biology and ecology of both plant-parasitic and free-living species, laid the foundation for many of the nematode control measures that are in use today and also contributed to the development of the discipline of nematology at an international level.G. R. Stirling, G. W. Yeates, K. Davies and M. Hodd

Dispersal of Potato Cyst Nematodes Measured Using Historical and Spatial Statistical Analyses

Rates and modes of dispersal of potato cyst nematodes (PCNs) were investigated. Analysis of records from eight countries suggested that PCNs spread a mean distance of 5.3 km/year radially from the site of first detection, and spread 212 km over ≈40 years before detection. Data from four countries with more detailed histories of invasion were analyzed further, using distance from first detection, distance from previous detection, distance from nearest detection, straight line distance, and road distance. Linear distance from first detection was significantly related to the time since the first detection. Estimated rate of spread was 5.7 km/year, and did not differ statistically between countries. Time between the first detection and estimated introduction date varied between 0 and 20 years, and differed among countries. Road distances from nearest and first detection were statistically significantly related to time, and gave slightly higher estimates for rate of spread of 6.0 and 7.9 km/year, respectively. These results indicate that the original site of introduction of PCNs may act as a source for subsequent spread and that this may occur at a relatively constant rate over time regardless of whether this distance is measured by road or by a straight line. The implications of this constant radial rate of dispersal for biosecurity and pest management are discussed, along with the effects of control strategies

First record of stubby-root nematode (Paratrichodorus porosus) associated with barley in Australia

High populations (5000 to 20 000/kg soil) of the stubby-root nematode Paratrichodorus porosus were identified morphologically from soil samples taken under patches of poorly growing barley in a field between Yuleba and Surat in western Queensland, Australia. Lower populations (<4000/kg soil) were recovered from soil samples taken from asymptomatic barley. This is the first record of this nematode species on barley in Australia