Habitat correlates of distribution and local population decline of the endemic Sardinian newt Euproctus platycephalus

Habitat-based statistical models relating patterns of presence and absence of species to habitat variables could be useful to resolve conservation-related problems and highlight the causes of population declines. In this paper, we apply such a modelling approach to an endemic amphibian, the Sardinian mountain newt Euproctus platycephalus, considered by IUCN a critically endangered species. Sardinian newts inhabit freshwater habitat in streams, small lakes and pools on the island of Sardinia (Italy). Reported declines of newt populations are not yet supported by quantitative data, however, they are perceived or suspected across the species' historical range. This study represents a first attempt trying to statistically relate habitat characteristics to Sardinian newt occurrence and persistence. Linear regression analysis revealed that newts are more likely to be found in sites with colder water temperature, less riparian vegetation and, marginally, absence of fish. The implications of the results for the conservation of the species are discussed, and suggestions for the short-term management of newt inhabited sites suggested.     

Long-term fluctuation of the soil fauna (Collembola and Oribatida) at groundwater-near sites in an alder wood

Collembola and oribatid mites were investigated at four sites along a cross section in an alder wood at a lake margin (northern Germany) over a period of 7 years. Monthly samples of the litter and the mineral layer were taken. Additionally, fluctuations of groundwater level, soil moisture, precipitation and soil temperature at 2 cm depth were measured. The alder wood was characterised by a depression between the lake margin and the foot of a hill slope, where waterlogged periods occurred. Groundwater level was the main environmental factor influencing the composition of collembolan and oribatid mite assemblages. Climatic factors, e.g. July temperature and July precipitation were also found to be significant factors, but with a much lower influence. Collembola predominantly showed higher variation in time than in space indicating that more collembolan species migrate within the investigated cross section or react with higher abundance fluctuations on the groundwater level changes, while Oribatida had a higher part of space variation, indicating that migration potential is lower and the environmental gradient is of higher influence on the distribution. Reaction time of soil fauna species on the groundwater fluctuation varies between 1 and 12 months. Retreat of Collembola from the waterlogged situation was between 4 and 6 months in the litter layer and 3 months in the mineral layer. Recolonisation of the waterlogged site lasted approximately 12 months. A positive reaction by precipitation was observed in four collembolan species that was 1 month in the edaphic species and between 9–10 months in the larger litter dwelling species. Only few oribatid mites reacted on the waterlogged situation.     

A priori valuation of land use for the conservation of black rhinoceros (Diceros bicornis)

The appropriateness of using carrying capacity (CC) estimates to indicate habitat utilisation for a particular species, and thus as a tool for conservation population planning, has been questioned. We argue individual fitness is driven by resource availability, and we therefore assume individuals select habitats with a higher quality, abundance, and availability of key resources. In the past such selection has been related to the CC of a habitat. We tested whether we can use CC estimates to indicate habitat selection by individuals using a selective forager, black rhinoceros Diceros bicornis, for which CC approaches underpin species conservation plans. We tested for correlation of individuals’ habitat selection with predicted CC values at three spatial scales of selection. Individual selection was not related to the value of the habitat according to our CC estimates for any of the three scales we tested at. We discuss how density-dependence, environmental variables, scale of selection, individual variation and intra- and inter-specific dynamics may have influenced these results. Following this, we question the use of a priori calculations of potential resource quality and abundance of habitats (CC estimates), which do not take into account the various factors that influence an animal’s selection of a habitat, as an indicator of species habitat selection. We raise caution regarding the use of such CC models to determine optimal population numbers for an area.     

Landscape occupancy and local population size depends on host plant distribution in the butterfly Cupido minimus

We tested whether the landscape occupancy and local population size of the monophagous butterfly Cupido minimus can be predicted by patch size and isolation of its host plant or by other habitat characteristics. C. minimus and its larval food plant Anthyllis vulneraria are classified as rare and endangered in northern Germany. Adults of C. minimus are ranked as the most sedentary butterfly species in northern Europe.Around the city of Göttingen (Germany), we checked all known locations of A. vulneraria (n=70) in June 2002 for butterfly eggs (in blooming flowerheads) and adult butterflies (within 20-min transects).We found eggs of C. minimus or a high number of adults (>7) in all habitats with A. vulneraria (which are calcareous grasslands) even when isolated up to 2-4 km. In multiple regression analyses, local population size of adult butterflies was positively related to the cover of its larval food plant A. vulneraria explaining 65% of variance. Cover of A. vulneraria increased with increasing habitat area and increasing cover of plant species in flower and decreased with increasing cover of shrub layer. Habitat isolation and further factors describing habitat quality were not related to C. minimus population size or cover of its larval food plant.The results suggest that dispersal ability of C. minimus is greater than expected and that management should focus to increase A. vulneraria patches. For conservation, low impact grazing once a year and removing of excessive shrubs in winter seems to be the most appropriate strategies.     

Habitat models and habitat connectivity analysis for butterflies and burnet moths - The example of Zygaena carniolica and Coenonympha arcania

In this paper, habitat models were used to predict potential habitat for endangered species, which is an important question in landscape and conservation planning. Based on logistic regression, we developed habitat distribution models for the burnet moth Zygaena carniolica and the nymphalid butterfly Coenonympha arcania in Northern Bavaria, Germany. The relation between adult occurrence and habitat parameters, including the influence of landscape context, was analyzed on 118 sites. Habitat connectivity analyses were carried out on the basis of (1) habitat suitability maps generated from these models and (2) dispersal data from mark recapture studies. Our results showed that (1) the presence of the burnet depended mainly on the presence of nectar plants and of nutrient-poor dry grasslands in direct vicinity, that of the nymphalid on larger areas of extensively used dry grasslands within 100 m vicinity in combination with small patches of higher shrubs and bushes. (2) Internal as well as external validation indicated the robustness and general applicability of the models. Transferability in time and space indicated their high potential relevance for applications in nature conservation, such as predicting possible effects of land use changes. (3) Habitat connectivity analyses revealed a high degree of habitat connectivity within the study area. Thus, we could show no effects of isolation or habitat size for both species.     

Recovery of reproduction after drought in the soil living Folsomia candida (Collembola)

Soil dwelling (euedaphic) Collembola have evolved to live in soil pores where the atmosphere is saturated with water vapour. Here we show that reproduction in the euedaphic Folsomia candida ceases during drought where soil water potentials are lower than −7 bar (∼99.4% RH). Recovery of the moulting cycle after cessation of drought showed increasing delay with increasing previous drought pressure. However, reproduction was rapidly resumed. Only in F. candida recovering from the most severe drought (−55 bar, 96% RH) was the time lapse between drought and resumed reproduction significantly different from the control (99.4% RH). Furthermore, the final numbers of eggs were unaffected by the degree of drought exposure. Hence, these results suggest that while even very mild drought will stop the reproductive cycle, subsequent recovery is rapid and complete.     

Defensive strategies of soil fungi to prevent grazing by Folsomia candida (Collembola)

Fungi represent a major part of the living biomass in the upper soil horizon and serve as an important food source for many soil organisms. We hypothesized that certain mycelial characteristics may serve to protect fungi from grazing. Specifically, this study focused on the influence of poisonous or other repellent metabolites and crystalline structures at the hyphal surface on the feeding preference of the soil microarthropod Folsomia candida Willem. The formation of crystalline structures was studied microscopically and the content of certain metabolites such as amanitin and muscarin was investigated using analytical methods. The feeding preference of F. candida was studied in different in-vitro food choice experiments. Additionally, the palatability of the fungal isolates was estimated by the amount of egg clusters laid by F. candida and by analysing the carbon and nitrogen content of the mycelia. F. candida was repelled by fungal species with toxic metabolites or crystals on their hyphal surface, which indicates that these traits serve as feeding protection. F. candida preferred dark-pigmented fungi. Total number of egg clusters and feeding preference were not correlated. However, insects that fed on fungi without repellent characteristics laid the most eggs. The amount of carbon and nitrogen in the mycelium had no influence on feeding behaviour. We conclude that the content of repellent metabolites and crystalline structures at the hyphal surface are defensive strategies of soil fungi and strongly influence feeding preference of F. candida. Other traits such as palatability were less important. Our results help to explain collembolan feeding behaviour and interactions between soil fungi and Collembola.     

Molecular phylogeny of three subfamilies of the Neanuridae (Insecta, Collembola) and the position of the antarctic species Friesea grisea Schäffer.

The nuclear 28S rRNA and the mitochondrial COII gene were used to establish phylogenetic relationships among species of the family Neanuridae, with special emphasis on species of the subfamily Neanurinae. Phylogenetic analysis was conducted using genetic distances, parsimony and likelihood methods. The D3-D5 fragment of the rRNA gene was very conserved, both in sequence and in secondary structure features. This fragment supplied little information on relationships at this level. The phylogenetic reconstruction based on 1st and 2nd codon positions of the COII gene was partly in accordance with morphological data, but it was discordant for the placement of some species. Relationships among the subfamilies Frieseinae, represented by the Antarctic species Friesea grisea, Pseudachorutinae and Neanurinae were uncertain. The subfamily Neanurinae and its tribes Neanurini and Paleonurini were shown as monophyletic taxa. Relationships between three species of the genus Bilobella were in accordance with morphological and biochemical data. Relationships between genera within the Neanurini were more controversial. In accordance with morphological hypotheses, a basal position of Thaumanura was suggested, but the molecular data placed Neanura muscorum in a derived position, in sharp contrast with morphological evidence. A close relationship was suggested between Deutonura conjuncta, Cansilianura malatestai and Lathriopyga longiseta. The disagreement between molecular and morphological data suggests that one or both data sets might be affected by a certain degree of homoplasy and that these data should be interpreted with caution in phylogenetic reconstructions.     

Habitat use, predicted distribution and conservation of green peafowl (Pavo muticus) in Dak Lak Province, Vietnam

In the last few decades, green peafowl numbers have declined drastically across their south-east Asian range, primarily, it is believed, due to human persecution and loss of habitat. They were formerly common across Vietnam, but are now restricted to a few central provinces. In this study green peafowl were surveyed in Dak Lak province, Vietnam, using a point-count methodology to assess their status and distribution, and to investigate their habitat use. Results showed that the most used habitat was dry deciduous forest with access to permanent water and free from human disturbance. Green peafowl density was lower in mixed and evergreen forest and lower when water was distant and/or human settlement was nearby. A map of predicted distribution was created which predicted that eastern and north-eastern Dak Lak are important areas containing much of the remaining habitat and populations of green peafowl. Several key river systems within this area were predicted to be of particular value. Deciduous forest < 2 km from water and > 2 km from human settlement was estimated to occupy only 3% of the province but to hold 37% of green peafowl. Conservation of green peafowl in Dak Lak, and elsewhere, should concentrate on maintaining undisturbed access to permanent water within large tracts of dry deciduous forest. The spread of human settlement presents the greatest threat; both directly due to hunting pressure and habitat loss and indirectly by preventing access to water in otherwise suitable areas.     

The distribution and diversity of Collembola in saltmarsh habitats of the German North Sea – a preliminary study

The distribution pattern and diversity of Collembola communities in the soils of low and high intertidal saltmarshes were compared. The intertidal “mud” soils are colonized by Collembola to depth of 30 cm and at a distance of 10 m towards the sea from coastal edge. The communities of Collembola in low intertidal saltmarsh soils are dominated by a population of Archisotoma sp. The contents of organic matter in the intertidal saltmarsh soils influenced the distribution of Archisotoma sp.     

Habitat requirements of the endangered pygmy bluetongue lizard, Tiliqua adelaidensis

The pygmy bluetongue lizard, Tiliqua adelaidensis, occupies spider burrows as home sites. It is an endangered species, known from only 19 small natural grassland sites in the mid-north of South Australia, all on privately owned land. Habitat requirements of the pygmy bluetongue lizard were investigated at four sites. Both within and between sites, lizards were more likely to be found in areas with a greater number of deep spider burrows. Areas where lizards were not found tended to lack these burrows. Strong site similarities were found for a range of habitat parameters examined. Within these grasslands there was no specific vegetation community associated with areas occupied by pygmy bluetongue lizards. However there was a distinct vegetation community associated with an absence of lizards. Generally there was no difference in the abundance and diversity of ground dwelling invertebrates between areas with and without lizards. As the only protected area of natural grassland within the known distribution, Mokota Conservation Park was assessed as a potential reintroduction site. It was found to be unsuitable due to a low number of deep spider burrows and a vegetation community similar to that found in uninhabited areas of known lizard inhabited sites. Unless other conservation areas can be established, preservation of this lizard will rely on habitat management by private land holders. Community goodwill and informed advice to the land holders will be essential in this process.     

Habitat characteristics of the endangered flightless beetle Dorcadion fuliginator (Coleoptera: Cerambycidae): implications for conservation

Habitat destruction and degradation are the major causes for the decline of the endangered grass-feeding flightless beetle Dorcadion fuliginator in Central Europe. We examined habitat characteristics at 19 localities which still support abundant D. fuliginator populations in the southern part of the Upper Rhine valley (border region of Switzerland, Germany and France) to obtain basic information for the management of deteriorating habitats with declining beetle populations. Populations of D. fuliginator were found in different types of grassland on south, south-west and south-east facing slopes and flat ground. Correspondence analysis showed that plant communities of D. fuliginator localities overlap widely with fertilized, dry hay meadows (phyto-sociologically defined as dry type of the Arrhenatheretum community) and to a minor extent with traditionally extensively cultivated dry grasslands (Xerobrometum and Teucrio-Mesobrometum communities). Average indicator scores of the plant communities characterize the habitat of D. fuliginator as fairly light-exposed and warm, but with relatively large ranges in humidity and nutrient content. The results of a 16-year study on the timing of emergence of the first beetles in a population provided further evidence for the high temperature requirements of D. fuliginator. Proposed conservation measures include traditional cultivation of the present secondary, man-made D. fuliginator habitats, introduction of beetles to suitable motorway embankments as well as large-scale measures allowing natural dynamics in the flood plain along the river Rhine, the presumably primordial habitat of this highly endangered beetle.     

Vertical distribution of Collembola (Hexapoda) and their food resources in organic horizons of beech forests

 Micro-samples of the surface organic horizons of 13 beech forests in Belgium were fixed immediately after collection in ethanol. Collembola (6255 animals) were sorted directly from micro-samples in the laboratory using a dissecting microscope, while the litter/soil matrix was analysed semi-quantitatively. The vertical distribution of Collembolan species was studied by correspondence analysis. Gut contents of animals were examined under a light microscope and their composition was compared with that of the matrix. A consistent association was found between the vertical distribution of gut contents and that of food resources in the immediate proximity of animals. Species differed in their feeding habits but most of them ingested a wide spectrum of food items. Plasticity in the food regime according to depth could be demonstrated in members of the Onychiuridae family. Received: 11 January 1999     

Effects of Medicago sativa, Taraxacum officinale and Bromus sterilis on the density and diversity of Collembola in grassy arable fallows of different ages

The density and diversity of Collembola of nine grassy arable fallows of different ages were investigated in a factorial design with the factors ‘plant species’ (legume: Medicago sativa, herb: Taraxacum officinale, grass: Bromus sterilis) and ‘age class’ (2-3, 6-8 and 12-15 years) including the random effect ‘site’ (1-9). In May 2008, four plots were selected randomly at each fallow. Within each plot five M. sativa, T. officinale and B. sterilis plants were extracted with their associated soil using steel cylinders. The material from each plant species was used for extraction of Collembola and for determination of environmental parameters. Thus, the new aspect of the present study compared to other field studies investigating the relationships between plant and Collembolan communities is the focus on the “micro-scale”, investigating the Collembolan communities of the soil associated with single plants.We found that species richness and density of total and euedaphic Collembola were significantly higher in B. sterilis than in T. officinale samples with the M. sativa samples being intermediate. Fine-root feeding euedaphic Collembola particularly benefited from the higher amount of fine roots in B. sterilis samples. We also discovered that the age of the fallows had no significant influence on the number of Collembolan species and the density of the Collembolan groups. Notably, however, species of the epedaphic genera Lepidocyrtus and Sminthurinus were associated with the 12-15 year-old fallows and presumably benefited from the high number of plant species in the old fallows. Finally, canonical correspondence analysis (CCA) indicated that the soil organic matter content and the microbial biomass, both potential food sources for many Collembolan species, were important structuring forces for the Collembolan communities.     

The effect of pH and calcium on copper availability to the springtail Folsomia candida in simplified soil solutions

The effect of pH and calcium on copper bioavailability to the springtail Folsomia candida was determined by assessing uptake kinetics upon copper exposure for 15 days in simplified soil solutions. A slight bioaccumulation of copper was observed in all treatments and controls. The effect of exposure concentration and calcium level on copper accumulation was not significant. Although pH and time slightly but significantly affected copper concentrations in the body, copper uptake rates were not significantly different from zero. This suggests that copper uptake in F. candida exposed to sub-lethal copper concentrations in soil pore water is not affected by pH and calcium.     

Habitat modelling for the conservation of the rare ground beetle species Carabus variolosus (Coleoptera, Carabidae) in the riparian zones of headwaters

Carabus variolosus is a highly endangered insect which is listed in the EC Habitats and Species Directive. Detailed knowledge of the habitat requirements of this semi-aquatic woodland carabid beetle is needed if effective conservation and management strategies are to be developed. Previous habitat models have proved to be a successful analytical and predictive tool for the conservation of species. We conducted an intensive study over a two year period on two extant C. variolosus populations in Westphalia (Germany) using live capture pitfall traps. We analysed the distribution of the beetles over their main activity period in relation to a large number of edaphic and vegetation variables in order to estimate habitat suitability models and describe optimum ranges. C. variolosus is restricted to the fringes of water bodies and to areas of high soil moisture that display patches of bare soil, shows a slight preference for sparse tree vegetation, and avoids acidic soil. Temporal and spatial transferability of the statistically significant habitat models indicates their robustness and validity. Based on the results of our study, we suggest management measures for the conservation of C. variolosus, which promote the rehabilitation of natural flood plains of headwater areas.     

Collembola effects on plant mass and nitrogen acquisition by ash seedlings (Fraxinus pennsylvanica)

We studied the effects of varied collembolan numbers on three compensatory mechanisms of nutrient uptake: fine root mass, endomycorrhizal development, and physiological uptake capacity. We grew ash (Fraxinus pennsylvanica) with or without the arbuscular mycorrhizal fungus Glomusintraradices, with 0, 10 or 50 initial Collembola (Folsomia candida). After 83 d root and uptake rates, endomycorrhizal development, and plant biomass were determined. Plant mass increased with Collembola number. Collembola interacted with mycorrhizae in their effects on N uptake and leaf N. Collembola in the absence of mycorrhizal roots were associated with lower N uptake and leaf N at 10 than at 0 or 50 initial Collembola. In contrast, Collembola in the presence of mycorrhizal roots were associated with the highest rate of N uptake and leaf N at 10 versus 0 or 50 initial Collembola. Hence as initial Collembola number increased, the relative importance of root system traits that determined N uptake changed from root physiological uptake capacity, presence of mycorrhizal roots, to fine root biomass.