Hemispheric asymmetries in biodiversity: a serious matter for ecology

[FIRST PARAGRAPH] Penguins have been receiving a lot of bad press lately. They are considered somehow counter, spare, strange. Unlike most plant and animal groups, they do not show a peak of species richness towards the equator and a decline towards the poles. This more conventional spatial pattern is conveniently known as the latitudinal diversity gradient because of the strong covariance of richness and other measures of biodiversity that it describes. It is one of the most venerable, well-documented, and controversial large-scale patterns in macroecology (Willig et al. 2003). Equatorial peaks in species richness have characterised the planet since the Devonian (408–362 million years ago) (Crame 2001) and are typical of a wide range of both terrestrial and marine plants and animals (Gaston 1996; Willig et al. 2003). Despite the fact that this pattern has been documented since the late 1700s, sustained interest in both the regularity of the pattern and its likely underlying mechanisms is relatively modern. The realisation that human activity is posing substantial threats to biodiversity has quickened the pace of this interest (Willig et al. 2003). Where the peaks in richness lie (biodiversity hotspots), how these peaks relate to centres of endemism (areas that support large numbers of species that occur nowhere else), and how these patterns are likely to change through time, especially in the face of major environmental change, are major concerns. Without such knowledge, conservation is unlikely to succeed

Effects of thermal acclimation on water loss rate and tolerance in the collembolan Pogonognathellus flavescens

A few days of thermal acclimation (to 5°C versus 15°C) may strongly affect tolerance to drought stress in Collembola. To better understand this phenomenon, the effect of acclimation on water loss rate and its consequence for survival in the species Pogonognathellus flavescens Tullberg (Tomoceridae) is investigated. Acclimation does not affect the water content of hydrated animals but animals exposed to 15°C and 76% relative humidity lose water much faster after having been acclimated to 5°C rather than 15°C. Tolerance to water loss is not affected; in both treatment groups, animals survive up to 40% loss of the water content recorded when fully hydrated. The percentage water content of hydrated animals decreases with size, which may explain why the proportion of initial water lost appears to be a better predictor for survival than the amount of remaining water. The proportion of initial water lost per unit time is little influenced by size in animals acclimated to 15°C but increases with decreasing size in the group at 5°C, indicating that acclimation affects a physiological protection against water loss.Centre of Excellence for Invasion Biolog

Litter decomposition in fynbos vegetation, South Africa

The Western Cape of South Africa is characterized by the hyperdiverse vegetation of the Fynbos biome. Typical fynbos vegetation is a !re-adapted sclerophyllous Mediterranean-type ecosystem on poor, sandy or stony soils. It is characterized by plants with low nutrient content producing slowly decomposing litter. Fire is recognized as a major factor for carbon and nutrient cycling in this vegetation type. However, knowledge of biological decomposition processes in this biome is limited.We used litter-bags to measure mass loss and changes in chemical composition in litter from three species representing characteristic taxa in fynbos, a Protea exima hybrid, Erica multumbellifera, and Restio multi!orus, during approximately 180 days. In addition, we used a standard litter of a species with high nutrient content, Galenia africana, and a mixture of Protea and Erica. We compare our results with a previous study from renosterveld including the geophyte Watsonia borbonica, which occurs in both vegetation types and occurs commonly in the study area. We found that decomposition rate among the true fynbos plant species P. exima, E. multumbellifera, R. multi!orus and W. borbonica varied almost eight-fold. Litter decomposition was strongly correlated to litter stoichiometry, i.e. C/N and C/P-ratios. Most litters accumulated one or several nutrients during the study period. The mixture of litters decomposed faster than expected from the results of each litter separately. Our study indicates that biological decomposition may be more important for carbon and nutrient cycling in fynbos than previously thought. These results are in accordance with recent studies showing large variation in plant litter quality within vegetation types and biomes. Such large variation in litter quality and decomposition rate suggests that some generalisations about ecosystem processes in the fynbos may need reevaluation

High spatial turnover in springtails of the Cape Floristic Region

Aim The extraordinary diversity of plants across the Cape Floristic Region is characterized by considerable species turnover among sites. Phytophagous insects show similarly high turnover, but their patterns are closely coupled to those of their hosts. If the mechanisms underlying high plant turnover are not unique to plants, similar patterns of turnover should also be seen in non-herbivorous arthropod groups. We tested this hypothesis using new data for the Collembola fauna of the Fynbos biome. Location The south-western Cape, South Africa. Taxon Springtails (Hexapoda: Collembola). Methods We sampled springtails from six sites over two seasons. Species richness was compared with expected values from other studies worldwide given the environmental characteristics of the sites sampled. Nestedness and turnover components of beta diversity were calculated and compared against beta diversity patterns of springtails across Europe. Results A total of 114 morphospecies from 14 families was collected. Species richness of Fynbos sites ranged from 14 to 31 species, which was not significantly different to that previously reported for non-Fynbos locations and generally within expectations given the temperature, rainfall and productive energy of each site. Beta diversity was high across all pairwise comparisons of Fynbos sites and dominated by species replacement rather than assemblage nestedness. Relative to the distance between sites, Fynbos assemblages, with a median inter-site distance of 140 km, showed beta diversity substantially higher than in European assemblages, which had a median inter-site distance of 1,270 km. Main conclusions Alpha diversity of Fynbos Collembola assemblages is in keeping with species richness expectations. By contrast, beta diversity is high given the small distances among sites and is characterized predominantly by species turnover. These patterns of unremarkable alpha diversity, but high turnover among sites are comparable to many Fynbos plant groups. The mechanisms giving rise to high beta diversity of the plants may also have led to high diversity in other taxa

Litter decomposition in fynbos vegetation, South Africa

The Western Cape of South Africa is characterized by the hyperdiverse vegetation of the Fynbos biome. Typical fynbos vegetation is a fire-adapted sclerophyllous Mediterranean-type ecosystem on poor, sandy or stony soils. It is characterized by plants with low nutrient content producing slowly decomposing litter. Fire is recognized as a major factor for carbon and nutrient cycling in this vegetation type. However, knowledge of biological decomposition processes in this biome is limited. We used litter-bags to measure mass loss and changes in chemical composition in litter from three species representing characteristic taxa in fynbos, a Protea exima hybrid, Erica multumbellifera, and Restio multiflorus, during approximately 180 days. In addition, we used a standard litter of a species with high nutrient content, Galenia africana, and a mixture of Protea and Erica. We compare our results with a previous study from renosterveld including the geophyte Watsonia borbonica, which occurs in both vegetation types and occurs commonly in the study area. We found that decomposition rate among the true fynbos plant species P.exima, E.multumbellifera, R.multiflorus and W.borbonica varied almost eight-fold. Litter decomposition was strongly correlated to litter stoichiometry, i.e. C/N and C/P-ratios. Most litters accumulated one or several nutrients during the study period. The mixture of litters decomposed faster than expected from the results of each litter separately. Our study indicates that biological decomposition may be more important for carbon and nutrient cycling in fynbos than previously thought. These results are in accordance with recent studies showing large variation in plant litter quality within vegetation types and biomes. Such large variation in litter quality and decomposition rate suggests that some generalisations about ecosystem processes in the fynbos may need reevaluation. © 2011 Elsevier Ltd

Supercooling point frequency distributions in Collembola are affected by moulting

1. Many arthropods depress the freezing point of their body fluids (supercool) to avoid freezing at subzero temperatures. This is normally a seasonal response and is achieved by the production of specific biomolecules including cryoprotectants, a cessation in feeding, and the removal or masking of ice-nucleating material from their bodies. 2. In springtails, the mid-gut is shed during moulting which results in the complete evacuation of the gut and a concomitant reduction in the supercooling point (SCP). We determined whether this non-adaptive explanation could account for the variability observed in the SCP of summer-acclimatized springtails. 3. Moult preparation resulted in a highly significant reduction in the SCP. Feeding after moulting restored the SCP to previous high levels. 4. Significant differences in SCP between springtails sampled from vegetation and the soil surface, on different days, and at different sites on the same day were also documented, demonstrating that not all variation in SCP is environmentally induced. 5. Investigations of the responses of the SCP to environmental variation in springtails and other arthropods should take into account the effects of moulting before solely adaptive conclusions are drawn

Ticks collected from birds in the northern provinces of South Africa, 2004-2006

Approximately 3 000 birds, mainly passerines, caught in mist nets in the northern provinces of South Africa, were examined for ticks. A total of 178 ticks, belonging to 14 species, were recovered from 83 birds of 43 different species. Hyalomma rufipes was the most numerous tick, with 26 larvae and 109 nymphs collected, followed by Amblyomma marmoreum, with 13 larvae and two nymphs. Despite the study being conducted within the distribution range of Amblyomma hebraeum, it was not seen on any passerines, whereas three larger species were infested. The potential for small birds to spread ticks with their associated tick-borne pathogens is discussed

The response of springtails to fire in the fynbos of the Western Cape, South Africa

Although fire is a natural form of disturbance in many ecosystems, the frequency of fires is increasing due to human activities. Hence, understanding the impacts of fire on biodiversity and ecosystem functioning has become increasingly important. In this study we investigated the effects of a large-scale fire on an important soil-dwelling group, springtails (Collembola), one year before and for three consecutive years after a fire in the fire-prone fynbos ecosystem in South Africa. In particular, we investigate the resistance of the springtail assemblages (i.e. their ability to remain relatively unchanged in the face of a disturbance), and their resilience (i.e. ability to return to a pre-disturbance state). To do this we sampled two sites with contrasting vegetation (Erica and Protea) and used three different standardized litter types in litterbag traps. A total of 35 springtail species from 31 genera and 14 families was found. The springtail assemblages in this fynbos system showed slightly more resistance to fire than resilience after the fire event, though substantial variation was found among vegetation types. Mean species richness and abundance per litterbag varied among the Protea and Erica sites, with resistant species being dominant in the Erica site, while species that showed an increase after the fire were dominant in the Protea site. Differences were also found between life forms: atmobiotic (free-living in vegetation) and epiedaphic (surface dwelling) species showed a significant decline in mean species richness directly after the fire in the Erica site. Euedaphic (soil-dwelling) species richness remained unchanged post-fire in the Erica site, while actually slightly increasing after the fire in the Protea site. Although the fynbos springtail assemblages had not fully recovered to pre-fire abundance after three years, many species appear to be resistant to or recover rapidly after fires, at least as ascertained over the relatively short (four years) duration of the study. It is likely that this response is influenced by the presence of suitable refugia within sites and by species-specific traits. Given changing fire regimes and the increasing frequency of fires due to human disturbances, the system will likely become more dominated by resistant springtail species preferring nutrient rich circumstances and easily decomposed litters

Autocatalysis as a source of synchronised rhythmical activity in social insects

SCOPUS: ar.jinfo:eu-repo/semantics/publishe