John Hollier

Direct and indirect effects of climate change on insect herbivores: Auchenorrhyncha (Homoptera)

1. Novel manipulations of local climate were employed to investigate how warmer winters with either wetter or drier summers would affect the Auchenorrhyncha, a major component of the insect fauna of grasslands. Direct and indirect effects of climate manipulation were found.

Interactions between plant and insect diversity in the restoration of lowland calcareous grasslands in southern Britain

The lowland calcareous grasslands of northwestern Europe are highly prized by ecologists and conservationists as a result of the diversity of their plant and invertebrate commu- nities. Large areas of such grasslands have been lost this century as a result of changes in agricultural land use. Recent changes in agricultural policies, in particular the introduction of agri-environmental incentive schemes, have resulted in an increasing area being managed for the restoration of these communities. This paper reviews the management techniques employed in the restoration of lowland calcareous grasslands and the factors that govern their success. Constraints on the enhance- ment of the plant diversity of restoration sites include high soil fertility and the presence of undesirable species in the soil seed bank. However, it is thought that the primary constraint is the availability of propagules from which new populations can be established. Similarly, the dispersal mode and ability of insect species is likely to be the major factor limiting the enhance- ment of insect diversity. Evaluation of the success of restoration management usu- ally involves monitoring changes in the plant community. How- ever, as a result of their short life-cycles and sensitivity to small- scale environmental conditions, insects may respond more rap- idly to changes resulting from restoration management and therefore provide better indicators of success. With the excep- tion of a few high-profile butterfly species, the use of insects as indicator taxa has largely been neglected in terrestrial systems. This paper illustrates their potential use with reference to low- land calcareous grasslands in southern Britain.

The effects of small mammal predators on grassland invertebrates, investigated by field exclosure experiment

The effects of small mammals on invertebrate prey populations in grassland were investigated by means of an exclosure experiment over a period of 2 yr. Using direct searches and suction sampling, numbers of invertebrates were compared in four experimental plots fenced to exclude small mammals and four control plots where they had free access. There was no evidence of differences in guild structure or species composition in either large or small invertebrates as a result of mammal predation, but numbers of large invertebrates were consistently and significantly smaller (by 22.7−64.8%) in the presence of mammals, due principally to the predatory effects of shrews

Grassland leafhoppers (Hemiptera: Auchenorrhyncha) as indicators of habitat condition - a comparison of between-site and between-year differences in assemblage composition.

The Auchenorrhyncha (leafhoppers) show great potential as indicators of grassland habitat quality, which would make them useful as a conservation tool. However, they are known to have labile populations. The relative importance of site identity and the year of sampling in the composition of leafhopper assemblages on chalk grassland are assessed for two sets of sites sampled twice. The study included a total of 95 sites (one set of 54, the other of 41), and demonstrated that for both sets the vegetation community and geographical location had high explanatory value, while the influence of year was small. The conclusion is that, notwithstanding population fluctuations, the leafhopper assemblages are a good indicator of habitat quality, and represent a potentially valuable tool in grassland conservation and restoration.

Successional leafhopper assemblages: Pattern and process

Auchenorrhyncha (leafhopper) faunas of a series of experimental plots of different successional age were recorded by vacuum sampling. There were clear successional trends in the assemblages. The life-history strategy of the dominant species changed during succession; the mobile and multivoltine or bivoltine species, which overwinter as adults or nymphs, are replaced by less active, univoltine or bivoltine species which overwinter as eggs. Leafhopper assemblages clearly responded to the changes in plant species composition and vegetation structure during succession; however, disentangling the relative importance of the various factors requires further experimental manipulation.

Community associations of chalk grassland leafhoppers (Hemiptera: Auchenorrhyncha): conclusions for habitat conservation

Due to their confinement to specific hostplants or restricted habitat types, Auchenorrhyncha have the potential to make suitable biological indicators to measure the quality of chalk grassland under different management practices for nature conservation. The Auchenorrhyncha data from a study designed to identify the factors influencing the invertebrate diversity of chalk grasslands in southern England was used to evaluate the potential use of this group of insects as biological indicators. Between 1998 and 2002 altogether 81 chalk grassland sites were sampled. Vegetation structure and composition were recorded, and Auchenorrhyncha were sampled at each site on three occasions in each of two seasons using a ‘Vortis’ suction sampler. Auchenorrhyncha assemblages were then linked to the different grassland plant communities occurring on chalk soils according to the British National Vegetation Classification (NVC). Altogether 96 Auchenorrhyncha species were recorded during the study. Using data on the frequency and dominance of species, as is commonly done for plant communities, it was possible to identify the preferential and differential species of distinct Auchenorrhyncha assemblages. Significant differences between the Auchenorrhyncha assemblages associated with the various chalk grassland plant communities of the NVC were observed down to a level of sub-communities. We conclude that data on Auchenorrhyncha assemblages can provide valuable information for the setting of conservation management priorities, where data on floristic composition alone may not be sufficient, providing additional information on aspects of vegetation structure and condition.

Microcrystals coating the wing membranes of a living insect (Psocoptera: Psyllipsocidae) from a Brazilian cave

Two specimens of Psyllipsocus yucatan with black wings were found with normal individuals of this species on guano piles produced by the common vampire bat Desmodus rotundus. These specimens have both pairs of wings dorsally and ventrally covered by a black crystalline layer. They did not exhibit any signs of reduced vitality in the field and their morphology is completely normal. This ultrathin (1.5 µm) crystalline layer, naturally deposited on a biological membrane, is documented by photographs, SEM micrographs, energy dispersive spectroscopy (EDS) and X-ray diffractometry (XRD). The crystalline deposit contains iron, carbon and oxygen, but the mineral species could not be identified. Guano probably played a role in its formation; the presence of iron may be a consequence of the excretion of iron by the common vampire bat. This enigmatic phenomenon lacks obvious biological significance but may inspire bionic applications. Nothing similar has ever been observed in terrestrial arthropods.

A replacement name for Dalodesmus sakalava (de Saussure & Zehntner, 1901) (Diplopoda: Polydesmida: Dalodesmidae)

Polydesmus (Pterodesmus) voeltzkowi nom. nov. is proposed as a replacement name for Polydesmus (Pterodesmus) sakalava de Saussure Zehntner, 1901, now Dalodesmus sakalava (de Saussure Zehntner, 1901), a junior primary homonym of Polydesmus sakalava de Saussure Zehntner, 1897.

Reinstatement of Spirostreptus kandyanus Humbert, 1865 and deletion of Thyropygus allevatus (Karsch, 1881) and Sphaeropoeus hercules (Brandt, 1833) in the checklist of Sri Lankan Diplopoda

The Diplopoda have been studied for some 250 years, but until the later part of the nineteenth century most descriptions were rather cursory and neither the species concept nor type concept were well established (Hoffman 2009). Even for well-explored regions like Europe, the description of the Diplopoda saw a proliferation of synonyms (Enghoff 1976) while the complexity of Diplopoda systematics was severely underestimated until very recently (Brewer et al. 2012).

The glacier theory of Louis Rendu (1789–1859) and the Forbes–Tyndall controversy

A translation is presented of an early formulation by Louis Rendu of the ideas later expanded in his 1841 Theorie des glaciers de Savoie, which described the movement of glaciers in terms of flowing ice. The reputation of James Forbes suffered, at least temporarily, from the accusation that he had deprived Rendu of due credit for this discovery. Although Rendu played no part in the disagreement, subsequent discussion of his scientific work has continued to view it in the context of this dispute, and concentrated on a single monograph. Rendus earlier discussion of glaciers in his monograph about the geology of Savoy, in which he summarised his argument, but without the supporting evidence included in the latter work, was apparently overlooked even by his supporters.