Groundwater copepods: diversity patterns over ecological and evolutionary scales

Copepods are common components of the groundwater fauna, and greatly increase the diversity of groundwater communities. With more than 900 species/subspecies known from continental groundwaters, stygobiont copepods inhabit all kinds of aquifers (karstic, fissured, porous), as well as surface/subsurface ecotones (land/water and water/water). The polyhedral and varied structure of the stygohabitats is reflected in the surprising mixture of functional morphologies and habitat exploitations experienced by groundwater copepods. Morphological adaptations and specializations are discussed, as well as the chronology of their appearance in the evolutionary history of several taxa. Diversity patterns of copepod assemblages in groundwater are examined under both structural and functional profiles, as well as across a range of scales. Structure and function operate in an interactive, sometimes hierarchical ways, as well as scales. On the ecological scale, local heterogeneity and patchiness in geomorphic and hydrologic characteristics, as well as biotic interactions, are to be considered causal factors affecting the diversity patterns over a range of spatial and temporal scales. On the evolutionary scale, it is widely accepted that stygobiont copepods evolved from ancestors living in marine, freshwater and semiterrestrial environments. They gained access to the groundwater through major highways represented by the interstitial and the crevicular/karstic corridors. `Phylogenetic diversity' in groundwater copepod taxocoenoses is viewed as a heterogeneous assemblage of species belonging to different phylogenetic lineages, which entered groundwater at different times and by different ways.     

Phylogenetic taxonomy of the marine mite genus Rhombognathides (Acari: Halacaridae: Rhombognathinae)

This study examined the impacts of the alien waterweed, water hyacinth, on the abundance and diversity of aquatic macroinvertebrates in the littoral areas of northern Lake Victoria in Uganda. The weed had undergone explosive growth on the lake causing serious disruption to people, the economy and the ecosystem. This study was confined to impact of the weed in the littoral zone, not to the large floating mats of vegetation which float across the lake and clog large areas of shoreline.The littoral area studied comprised of fringing mats of Eichhornia crassipes (Mart) Solms (water hyacinth) to the lakeward of Cyperus papyrus; water hyacinth mats undergoing colonisation by Vossia cuspidata (Roxb.) Griff.; and a typical Cyperus papyrus L shore with no outer floating mat of water hyacinth. Numerical abundance (Nos. m^–2) and diversity (No. of taxa) of macroinvertebrates recovered from pure Eichhornia crassipes and the Eichhornia-Vossia succession increased from the fringe of the Cyperus papyrus towards the open water. In the typical Cyperus papyrus fringe, in the absence of water hyacinth, abundance was highest at the papyrus/open water interface and dropped off sharply towards open water. The Shannon–Weaver diversity index (H) of macroinvertebrates decreased progressively from pure Eichhornia crassipes stands, to Vossia/Eichhornia beds and Cyperus papyrus stands (H=0.56, 0.54 and 0.34, respectively) but were not significantly different. Dissolved oxygen decreased from open water into vegetation where it approached anoxia. Water hyacinth appeared to enhance the abundance and diversity of aquatic macroinvertebrates at the interface with the open water. The impoverished abundance and diversity of the macroinvertebrates deeper into the vegetation mats suggested negative environmental impacts of the water hyacinth when the fringe is too wide. Further research is recommended to establish the optimum width of the fringe of stationery water hyacinth that promotes maximum abundance and diversity of aquatic macroinvertebrates and, possibly, of other aquatic life. Since this study in 1997, there has been a dramatic decrease in Eichhornia infestations and by June 2000 it appeared largely to exist only as fringing vegetation in bays and inlets.     

Phylogeography and conservation genetics of the Iowa pleistocene snail

The Iowa Pleistocene snail, Discus macclintocki, is an endangered species that survives only in relictual populations on algific (cold-air) talus slopes in northeast Iowa and northwest Illinois in the central region of the USA. These populations are believed to have been isolated since the temperatures began to warm at the end of the last glacial period around 16 500 years ago. DNA sequencing of the 16s rRNA gene of the mitochondria was used to determine the genetic relationship among 10 populations and the genetic diversity within these populations. Genetic diversity is extremely high within this species with 40 haplotypes spread across the 10 populations sampled within a 4000 km2 region. Phylogenetic analyses showed that haplotypes formed monophyletic groups by the watershed on which they were found, suggesting that watersheds were important historical avenues of gene flow. Genetic distances were strongly related to the geographical distance among all populations, but this relationship was dependent on the scale being considered.     

Comparison of the population genetics and densities of five pinanga palm species at kuala belalong, brunei

This study investigated the effect of population density on the population genetic structure of five co-occurring congeneric understorey palm species: Pinanga aristata, P. sp. aff. brevipes, P. dumetosa, P. tenella var. tenella and P. veitchii, all endemic to northern Borneo. The average population densities of the study species varied across a wide spectrum, ranging from 343 (plants per ha) in P. tenella to 10 (plants per ha) in P. veitchii. All species of Pinanga palms studied had quite high levels of genetic diversity (HE: 0.379, 0.256, 0.294, 0.133, 0.352). Genetic diversity (HE) was correlated with population density (D; rs = - 0.433, P < 0.01) and the average distance to the nearest conspecific neighbour (NN; rs = 0.576, P < 0.001) such that the most-dense species had less genetic diversity and the less-dense species had greater genetic diversity. Gene flow (Nm) among populations approximately followed a gradient of increasing species density and abundance, such that the most common species P. dumestosa had the greatest gene flow (Nm = 2.268) between its populations and the rarest, most sparsely distributed species P. sp. aff. brevipes had the lowest (Nm = 0.698). All species of Pinanga were effectively inbred (F: 0.760, 0.856, 0.640, 0.753, 0.674). The amount of homozygosity and inbreeding (HO, F) were not correlated (P > 0.05) with population density (D) or the distance between nearest neighbouring plants of the same species (NN).     

Glomalean mycorrhizal fungi from tropical Australia

 A comparison of different methods for isolation of vesicular-arbuscular mycorrhizal (VAM) fungi into open-pot cultures was undertaken as part of a study of the diversity of these fungi. Four different isolation techniques using spores separated from soil, soil trap cultures, root samples, or transplanted seedlings grown in intact soil cores were used to obtain as many fungi as possible from each site. Isolation methods were compared using paired samples from the same locations within natural (savanna, rocky hill, wetland, rainforest) and disturbed (minesite) habitats in a seasonally dry tropical region in the Northern Territory of Australia. There were large differences in (i) the efficiency (rate of increase in mycorrhizal colonisation), (ii) the proportion of successful cultures, (iii) fungal diversity (number of fungal species in each culture) and (iv) specificity (identity of species isolated) between these four procedures. However, the less-efficient procedures generally resulted in a higher proportion of cultures of one fungus, which could be used without further isolation steps. Most species of Scutellospora, Acaulospora and Gigaspora were obtained primarily from field-collected spores, but only 50% of these culture attempts were successful. Spores from these initial cultures produced mycorrhizas much more rapidly and successfully when used to start second-generation cultures. Several species of fungi, rarely recovered as living spores from field soils, were dominant in many trap cultures started from soil or roots. Most of these fungi were Glomus species, that were first distinguished by colonisation patterns in roots and eventually identified after sporulation in second- or third-generation trap cultures. These experiments demonstrated that glomalean fungi in the habitats sampled belonged to two functional categories, based on whether or not spores were important propagules. The "non-sporulating" fungi were dominant in many trap cultures, which suggests that these fungi had higher total inoculum levels in soils than other fungi. Pot-culturing methods provided additional information on fungal diversity which complemented spore occurrence data obtained using the same soil samples and provided valuable new information about the biology of these fungi. Accepted: 26 December 1998     

Structure,composition and species diversity in an altitude-substrate matrix of rain forest tree communities on Mount Kinabalu,Borneo

We studied forest structure, composition and tree species diversity of eight plots in an environmental matrix of four altitudes (700, 1700, 2700 and 3100 m) and two types of geological substrates (ultrabasic and non-ultrabasic rocks) on Mount Kinabalu, Borneo. On both substrate series, forest stature, mean leaf area and tree species diversity (both 4.8 cm and 10 cm diameter at breast height [dbh]) decreased with altitude. The two forests on the different substrate series were similar at 700 m in structure, generic and familial composition and tree species diversity, but became dissimilar with increasing altitude. The decline in stature with altitude was steeper on the ultrabasic substrates than on the non-ultrabasic substrates, and tree species diversity was generally lower on ultrabasic substrates than on non-ultrabasic substrates at 1700 m. The forests on non-ultrabasic substrates at higher altitudes and those on ultrabasic substrates at the lower altitudes were similar in dbh versus tree height allometry, mean leaf area, and generic and familial composition at 1700 m. These contrasting patterns in forest structure and composition between the two substrate series suggested that altitudinal change was compressed on the ultrabasic substrates compared to the non-ultrabasic substrates. Tree species diversity was correlated with maximum tree height and estimated aboveground biomass, but was not with basal area, among the eight study sites. We suggest that forests with higher tree species diversity are characterized by greater biomass allocation to height growth relative to trunk diameter growth under more productive environment than forests with lower tree species diversity.     

Reserve selection in the Succulent Karoo,South Africa: coping with high compositional turnover

The Succulent Karoo biome is home to the world's richest succulent flora. It has approximately 1954 endemic plant species, and is the only semi-arid region to qualify as a hotspot of global significance. Despite its importance, only 2% of the biome is currently protected. Based on its flora, the biome can be divided into 12 bioregions, reflecting its high compositional turnover in relation to environmental and geographical gradients. Only three of these bioregions (the Gariep Centre, the Namaqualand Rocky Hills and the Tanqua Karoo) contain National Parks, and three contain large (over 10000 ha) provincial reserves (the Gariep Centre, the Namaqualand Rocky Hills and the Little Karoo). The current reserve system does little to conserve biodiversity, with only one reserve significantly conserving Red Data Book (RDB) plant diversity. Using a RDB plant species database of 3874 records at a quarter degree scale (QDS = 15×15), we used hotspot analyses and iterative reserve selection algorithms to identify possible locations for future reserves. The hotspot analysis and iterative analyses yielded similar results for the top 11 QDS, mainly due to very high local endemism. Also because of the local endemism and the high species turnover within the biome, the real-world iterative algorithm (starting with the seven already reserved QDS) selected a very large total number of QDS (59% of the total in the biome) to conserve all RDB species. As a possible alternative to conservation planning based on QDS, we also assessed priorities at the scale of bioregions, but showed that representation at this geographic level misses important areas defined at a finer scale. We suggest that if the objective is to maximise the retention of RDB species in the landscape (to pre-empt extinction by scheduling the allocation of limited conservation resources), at least the top 5% of QDS (n=11) selected by the iterative procedure, and identified as the core conservation sequence by analysis of endemicity and threat, should be given priority for reservation. Less extensive and, in some cases, less formal conservation action can be applied to QDS later in the sequence, based on species-specific monitoring and action plans. Of the 11 core areas, four fall in a node centred on the Vanrhynsdorp Centre, two fall in a node centred on the Kamiesberg, and the remaining five are isolated. With existing reserves, the core areas capture 50% of the RDB flora in 8% of the biome.     

The ukc1 gene encodes a protein kinase involved in morphogenesis, pathogenicity and pigment formation in Ustilago maydis

The fungal phytopathogen Ustilago maydis alternates between budding and filamentous growth during its life cycle. This dimorphic transition, which is influenced by environmental factors and mating, is regulated in part by cAMP-dependent protein kinase (PKA). We have recently identified a related protein kinase, encoded by the ukc1 gene, that also plays a role in determining cell shape. The ukc1 gene is homologous to several other protein kinase-encoding genes including the cot-1 gene of Neurospora crassa, the TB3 gene of Colletotrichum trifolii, the orb6 gene of Schizosaccharomyces pombe, the warts tumor suppressor gene of Drosophila melanogaster and the myotonic dystrophy kinase gene in humans. Disruption of the ukc1 gene in U. maydis resulted in cells that were highly distorted in their morphology, incapable of generating aerial filaments during mating in culture and defective in their ability to cause disease on corn seedlings. In addition, the cells of ukc1 mutants became highly pigmented and resembled the chlamydospore-like cells that have been described for U. maydis. Overall, these results demonstrate an important role for the ukc1-encoded protein kinase in the morphogenesis, pathogenesis and pigmentation of U. maydis. Received: 6 May 1998 / Accepted: 19 November 1998