Faunistic knowledge and insect species loss in an urban area: the tenebrionid beetles of Rome

Journal of Insect Conservation - I used data on tenebrionid beetles (Coleoptera Tenebrionidae) accumulated in entomological collections from urban Rome to describe how faunistic knowledge developed...     

Use of insect rarity for biotope prioritisation: the tenebrionid beetles of the Central Apennines (Italy)

Insect conservation has been traditionally based mainly on the identification of priority biotopes. One of the most commonly used criteria for biotope prioritisation is the occurrence of priority species, hence the need for measures of species vulnerability. In this paper a two-step protocol for biotope prioritisation is proposed. Firstly, insect species vulnerability is estimated from rarity measures that can be easily derived from basic data. Then, these values of vulnerability are used to rank biotopes. The method was applied here to the tenebrionid beetles of the Central Apennines, a montane area of high conservation concern for South Europe. Their use in this paper is an example of the use of data hidden in museum collections for analyses dealing with traditionally overlooked insect groups. Most of conservation decisions for Mediterranean mountains are biased towards certain vertebrates. Although current management practices in the preserves of the study area are generally consistent with the conservation of tenebrionids (especially woodland protection, which is essential for arboreal species), results provided in this study stress the importance of preserving also open biotopes, which are crucial for many taxa, including several endemic forms. Moreover, there is indication that preservation of such kind of biotopes would be important also for vertebrates. The approach for biotope prioritisation based on species rarity was here applied to a single animal taxon, but it can be easily extended to other insect groups, in order to obtain a more general view of the relative importance of different biotope types for Apennine conservation.     

The toxic effects of phenoloxidase from the haemolymph of tenebrionid beetles

The injection of haemolymph originating from several species of tenebrionid beetles into blowfly larvae caused a gradual paralysis accompanied by colour changes in the haemolymph of the injected test insects. It was found that the lethal effect of the haemolymph of the beetle Blaps sulcata was due to phenoloxidase. The enzyme was activated by the exposure and incubation of the haemolymph at room temperature.The identity between the toxic factor and phenoloxidase in the beetle's haemolymph was demonstrated by the following data: (1) A correlation between the rate of lethal and phenoloxidase activities during the activation process of the toxic haemolymph. (2) Phenylthiourea, a well-known inhibitor of phenoloxidase, inhibited both the enzymatic and the toxic action of the beetle's haemolymph. (3) A commercial preparation of phenoloxidase (originating from mushrooms) imitated the lethal effects and the accompanying symptoms of the toxic haemolymph. (4) Sephadex G-100 column separation of the Blaps haemolymph revealed a complete overlap between the enzymatic and lethal regions of the elution pattern.The possible effects of phenoloxidase on the haemolymph of the injected insects are discussed.     

Island biogeography of urban insects: tenebrionid beetles from Rome tell a different story

Tenebrionid beetle records from 55 sites in urban Rome (Italy) were used to study the influence of structural parameters (area, isolation, forest cover, and shape) of green spaces on species richness and extinction trends. In line with biogeographical predictions, species richness correlated positively with area size of green spaces, extinction was enhanced by isolation and hindered by area size, but, in contrast with common findings, forest extent had a negative impact on tenebrionid persistence. This is explained by the fact that most of tenebrionid species from Rome are associated with open habitats typical of the landscape that characterized the study area before modern urbanization. In contrast with results obtained in other studies of urban ecology, distance to city centre (which expresses the urban–rural gradient) was never recovered as an important correlate of tenebrionid richness or extinction, which may be explained by the fact that tenebrionids include both urban avoider and urban adapter species. These results warn against making generalizations on urban diversity patterns and conservation strategies without reference to past land-use and species characteristics.     

The influence of food supplementation on a coastal dune rodent community

Studies of the rodent community in regenerating coastal dune forest areas north of Richards Bay, South Africa, have indicated that a number of species occupy newly rehabilitating areas. Unstable environmental conditions result in habitat changes, rather than competitive interactions, being the major determinant of rodent community development. This led to the present study, which investigated the effects of supplementary food on rodent assemblages. We attempted to stabilize food availability in order to elucidate some of the mechanisms responsible for the development of the rodent community. By only increasing an existing portion of the resource spectrum, we reduced species diversity, probably through dominance by competitive superior exploiters of the augmented resource. Thus, species diversity decreased with food supplementation, as a result of an increase in the abundance of Mastomys natalensis rather than because of a change in the number of species or the abundance of other species.     

Genetic characteristics of coastal cutthroat trout inhabiting an urban watershed

Watersheds in urban areas are often heavily degraded due to human activity, which can have negative impacts on freshwater fishes. Monitoring the genetic characteristics of urban populations can provide insights into the impact of development on aquatic ecosystems. We performed a genetic analysis of coastal cutthroat trout (Oncorhynchus clarkii clarkii) inhabiting urban tributaries in Portland, OR. By analyzing nuclear microsatellite genotypes, we were able to assess population structure, genetic diversity, and effective population size for six locations across two tributaries on opposite sides of the Willamette River. Genetic diversity was generally equivalent across all sampling locations, although populations from smaller tributaries higher in the stream network had lower levels. Levels of effective population size were low but within expected ranges for small salmonid populations. As anticipated, smaller populations had higher levels of inter-individual relatedness. The primary genetic structure divided populations on opposite sides of the Willamette River, although there was evidence of dispersal between the two groups. Our results suggest that cutthroat trout inhabiting metropolitan areas are not necessarily genetically impoverished and may exhibit characteristics typical of populations in more ‘natural’ environments. Understanding how fish, especially anadromous species, respond to urban environments is essential to evaluating the value of these areas for conservation planning.     

The reproductive behavior of six species of Namib desert tenebrionid beetles (Coleoptera: Tenebrionidae)

The reproductive behavior of six species of tenebrionid beetles (Coleoptera: Tenebrionidae) was studied in the Namib Desert of southern Africa. In three species, males follow closely behind females (following behavior), while in the other three species, males mount females and remain clasped to them for extended periods (riding behavior). Following behavior occurs before and sometimes after copulation, while riding behavior occurs primarily after copulation. Males of all six species guard females from contesting males, although the effectiveness of guarding is greater in riding species. The evolution of the two male mating strategies does not appear to be related to operational sex ratio differences but, rather, to differential tendencies of females to remate. Variation in total pair duration within following and riding species may be attributed partly to species differences in operational sex ratio. However, pair durations are not affected by experimental manipulations of sex ratio in each species.     

Disentangling the effects of available area,mid-domain constraints,and species environmental tolerance on the altitudinal distribution of tenebrionid beetles in a Mediterranean area

Most studies have attempted to identify the major environmental factors responsible for elevational variations in species richness. Such studies have been mainly performed in temperate and tropical areas, whereas the mediterranean biome has been substantially neglected. The aim of this paper was to disentangle the effects of available area, mid-domain constraints, and the environmental tolerance of species, on the altitudinal distribution of tenebrionid beetles in a Mediterranean region. A comprehensive faunistic database was used to assess the elevational distribution of tenebrionids in Latium (Central Italy). Variations in species richness, beta diversity and nestedness were analysed in association with variation in species ranges and midpoints. Variation in species richness was contrasted with patterns expected on the basis of the mid domain effect (MDE) and available surface area. After correcting for differences in area availability due to the conical shape of mountains, an unexpected triphasic pattern emerged: (1) at low altitudes, species richness was higher than expected on the basis of the effect of area and the MDE; (2) at around 800 m elevation, there is an abrupt change in species assemblages, and richness values fit those predicted by the MDE; (3) a new dramatic change occurred at 1,700 m, with tenebrionid assemblages composed of a small number of mainly eurytopic species. The integrated approach used in this study demonstrates that neither MDE nor monotonic patterns fully explain the observed diversity patterns. Variations in species ranges indicate that the elevational gradient filters species according to their ecological tolerance.     

The primary structure of the hypertrehalosemic neuropeptide from tenebrionid beetles: a novel member of the AKH/RPCH family

A hypertrehalosemic neuropeptide from the corpora cardiac of the two tenebrionid beetle species, Tenebrio molitor and Zophobas rugipes, was purified by high performance liquid chromatography, and its sequence determined by pulsed-liquid phase sequencing employing Edman degradation after deblocking enzymatically the N-terminal pyroglutamate residue. Additionally, the C-terminus of the peptide was blocked as shown by the lack of breakdown using carboxypeptidase. In both species an identical octapeptide, designated Tem-HrTH, with the following amino acid sequence, was found: pGlu-Leu-Asn-Phe-Ser-Pro-Asn-Trp-NH2. This primary sequence has an 88% homology with the hypertrehalosemic hormone I (Pea-CAH-I) from the American cockroach as well as with the red pigment-concentrating hormone (RPCH) of prawns. Injection of the synthetic peptide into larvae or young adults of T. molitor or adult Z. rugipes increases the hemolymph carbohydrate levels in a dose-dependent manner. Thin layer chromatography identified the elevated sugar component of the hemolymph as the disaccharide trehalose. Carbohydrate release from larval fat body in vitro was also shown upon administration of a low concentration of synthetic Tem-HrTH.     

Climatic correlates of body size in European tenebrionid beetles (Coleoptera: Tenebrionidae)

Tenebrionidae are one of the largest families of beetles and are known for their adaptations to hot and dry climates. An increase in body size also increases the volume/surface area ratio, which reduces transpiration, and hence water loss. If an increase in body size is an important adaptation in tenebrionids to cope with increasing aridity, we expect a correlation between body size and climatic gradients in the major tenebrionid clades. Alternatively, we can postulate that arid climates do not drive body size evolution, but rather select, from a wider fauna containing species of any size, those that have larger bodies. In this case we expect that drier regions will host faunas that contain, on average, larger species. To test the first hypothesis, we correlated inter-specific body size variation in the main tenebrionid clades with climatic gradients in Europe. We found only weak trends. To test the second hypothesis, we regressed mean body size of European country faunas against climatic characteristics. We found a strong increase in body size in southern faunas experiencing hot and dry climates. Therefore, increase in body size is not a major adaptation in tenebrionid evolution, but climate is an important filtering factor that determines a prevalence of larger species in southern Europe.     

Body temperatures of Namib Desert tenebrionid beetles: their relationship in laboratory and field

Abstract The body temperatures of six apterous species of Namib Desert tenebrionid beetles were measured continuously with indwelling thermocouples under laboratory conditions and in the field. The range of body temperatures selected was within the upper half of their 'tolerated range', which we defined as the temperatures lying between measured critical thermal maximum and critical thermal minimum. In the field, individuals also maintained their body temperatures within the upper half of the 'tolerated range'. These beetles maintained higher body temperatures than those recorded for any other ectothermic insect. Three of the six species maintained lower body temperatures in the field than they selected in the laboratory. The other three species showed no significant difference between field and laboratory body temperatures. We conclude that these beetles are not forced by biotic or abiotic factors to adopt thermal niches which present them with physiological difficulties.     

A comparative study of the chemical defensive system of tenebrionid beetles: Chemistry of the secretions

The chemical compositions of the defensive secretions of 147 species of tenebrionid beetles from 55 genera and 16 tribes were analysed by gas-liquid chromatography on three different stationary phases. All species contained toluquinone and ethylquinone, but benzoquinone was relatively rare. A great many species contained various 1-alkenes in addition to quinones. Species of Pedinini were distinguished by the secretion of n-propylquinone, whereas 2,3-methylmethoxyquinone set apart the subgenus Blapylis (of Eleodes) and possibly Amphidora. Large amounts of octanoic acid were restricted to the genera Embaphion and Neobaphion (both Eleodini), and small amounts of 1-nonadecene were restricted to Lariversius (Eleodini) and Cratidus (Amphidorini). Most species of Eleodes had complex secretions with toluquinone, ethylquinone, 1-nonene, 1-undecene, and 1-tridecene in various ratios. 1-Pentadecene and/or 1-heptadene occurred in substantial amounts in Tribolium, Uloma, Phaleria, Pyanisia, Melanopterus, Gonopus, Schelodontes, Psorodes, Neatus, and Merinus. The genus Argoporis (Scaurini) is unique in its synthesis of 6-alkyl-1,4-naphthoquinones, and other members of the tribe also contain characteristic, as yet unidentified compounds. Many groups not distinguished by unique compounds still show characteristic combinations and ratios of compounds, and these are discussed along with problems of variation at the individual, geographic, specific, and generic levels.     

Movements of carabid beetles (Coleoptera: Carabidae) inhabiting cereal fields: a field tracing study

Summary The individual movements of four carabid species were investigated by tracing beetles in the field using a portable radar system (harmonic radar). The field-inhabiting a Pterostichus melanarius Illiger, P. niger Schaller and Harpalus rufipes De Geer were traced in cereal fields. The movements of P. melanarius Mnd P. niger were also tracked in a wood and then compared with the movements of the forest-species Carabus nemoralis Müller. P. melanarius and P. niger displayed directed movements in cereal fields, although P. niger moved faster than P. melanarius. The movement pattern of H. rufipes in the field, and C. nemoralis and P. malanarius in the wood can be described as a c correlated random walk. In cereal fields, P. melanarius burrowed actively into the soil, and P. niger searched out crevices. In contrast, none of these two carabids burrowed in the forest soil, whereas C. nemoralis did. No statistically significant difference was observed between the movements of hungry and satiated beetles, although starved beetles tended to disperse shorter distances per move and turned back more often (especially P. niger). The significance of the various movement patterns exhibited by the species studied for their reproduction and survival on arable land is discussed.     

Mite and insect zonation on a Marion Island rocky shore: a quantitative approach

This study provides the first quantitative analysis of the littoral and supralittoral insect and mite assemblages of sub-Antarctic Marion Island. Seventeen mite species (126,203 individuals) from 11 families were found on the shore at Macaroni Bay. Three families dominated the assemblages in both abundance and diversity: the Hyadesiidae, Ameronothridae and Halacaridae. Six insect species from three orders were found on the shore. Species richness increased from one in the littoral, to four and two species in the Mastodia and Caloplaca zones, respectively. The littoral chironomid midge Telmatogeton amphibius was the most abundant insect species, constituting 80% of all insects counted. Arthropod assemblages corresponded closely to the cryptogam-dominated zonation patterns previously identified for the Marion Island shore. This clear association between arthropod and cryptogam zonation patterns provided a clear indication of habitat specificity in many of the species, and a quantitative analysis of habitat specificity on a species by species basis supported this idea. The specificity of most species to the shore, which forms part of the epilithic biotope, is most likely a consequence of the considerable age of this biotope compared to the younger, post-glacial vascular vegetation. Tourist species, i.e. species transient to an assemblage, inflated species richness in zones and the distribution ranges of species across zones. It is suggested that previous qualitative analyses of shoreline arthropod communities may have overestimated species ranges and richnesses because of the inclusion of tourist species. It is suggested that if a sound understanding of patterns in, and processes underlying Antarctic arthropod assemblages is to be achieved, quantitative analyses must be expanded in the region. Accepted: 14 May 2000     

The importance of facilitation in the zonation of shrubs along a coastal salinity gradient

Question: What are the interactive roles of abiotic stress and plant interactions in mediating the zonation of the shrub Tamarix chinensis along a salinity gradient? Location: Yellow River estuary (37°46′N, 119°09′E), northeast China. Methods: We surveyed the zonation of T. chinensis along a salinity gradient and quantified its salt tolerance using a pot experiment. In two field experiments, we transplanted T. chinensis seedlings into salt marsh, transitional zone and upland habitats, manipulated neighbours and quantified survivorship and biomass to examine neighbour effects. We also quantified vegetation effects on abiotic conditions in each zone. Results: Tamarix chinensis dominated the transitional zone, but was absent in upland and salt marsh habitats. In the pot experiment, T. chinensis grew well in freshwater treatments, but was inhibited by increasing salinity. Field experiments revealed that competition from neighbours limited T. chinensis growth in the uplands, while T. chinensis transplants were limited, with or without neighbours, in the salt marsh by high soil salinity. In the transitional zone, however, T. chinensis transplants performed better with than without neighbours. Vegetation removal significantly elevated soil salinity in the transitional zone, but not in other zones. Conclusions: Competition, facilitation and abiotic stress are all important in mediating the zonation of T. chinensis. Within its physiological stress tolerance range, or fundamental niche, it is limited by plant competition in low salinity habitats, and facilitated by neighbours in high salt stress habitats, but cannot survive in salt marshes having salinities above its salt stress tolerance limit. Our results have implications for understanding the relationships between facilitation and stress gradients.     

Ancient origin of a Western Mediterranean radiation of subterranean beetles

Background  

Cave organisms have been used as models for evolution and biogeography, as their reduced above-ground dispersal produces phylogenetic patterns of area distribution that largely match the geological history of mountain ranges and cave habitats. Most current hypotheses assume that subterranean lineages arose recently from surface dwelling, dispersive close relatives, but for terrestrial organisms there is scant phylogenetic evidence to support this view. We study here with molecular methods the evolutionary history of a highly diverse assemblage of subterranean beetles in the tribe Leptodirini (Coleoptera, Leiodidae, Cholevinae) in the mountain systems of the Western Mediterranean.     

Facilitation between coastal dune shrubs: a non-nitrogen fixing shrub facilitates establishment of a nitrogen-fixer

Understanding positive interactions among species is integral to predicting the outcomes of community-level dynamics. Few studies have explored intraspecific variation in positive associations. We investigated facilitation between two coastal dune shrubs in California, Baccharis pilularis and the nitrogen-fixing species, Lupinus arboreus . L. arboreus seedlings and adults were non-randomly distributed, occurring most frequently in association with B. pilularis . The relationship depended on the genotype of B. pilularis ; only the prostrate architectural form of this species was positively associated with L. arboreus . To evaluate the nature of this association, we assessed the influence of three microhabitat types (prostrate B. pilularis , Ammophila arenaria (an introduced dune grass), and exposed sand) on four life history stages of L. arboreus . Prostrate B. pilularis benefited L. arboreus seedling emergence, survival, and growth but had no effect on post-dispersal seed predation or adult establishment. Enhanced resistances to granivory by rodents or to seedling predation by voles were not important mechanisms underlying facilitation. In addition, an experiment manipulating herbivory by cutworms found no effects of microhabitat on susceptibility to damage. Evidence supports the hypothesis that the prostrate form of B. pilularis facilitates L. arboreus germination, seedling growth, and establishment as compared to exposed sand and dune grass. Furthermore, in combination with prior research, the results suggest that by facilitating an important nitrogen-fixer, B. pilularis may have effects that cascade to other members of the coastal plant community.     

Structure of the apical cells of the testis of the tenebrionid beetles: Tenebrio molitor and Zophobas rugipes

The developmental cytology of the apical tissue of the testis of Tenebrio molitor and Zophobas rugipes was studied with light and electron microscopy. In the early larvae of both species the tisue was found to be a thickened protrusion of nongerminal cells appearing at the apical end of each testis follicle following gonadal differentiation. The cells persist through pupal and adult stages in both species, becoming more prominent at these stages in Z. rugipes, despite tracheal invasion in both species. In older adults the apical tissue regresses and ultimately distintegrates. Ultrastructurally the apical cells are distinguished from adjacent germinal cells by their (1) small, rounded or oval nuclei, (2) highly convoluted plasma membrane, (3) electron-opaque cytoplasm, (4) profuse concentrically-stacked, granular endoplasmic reticulum, (5) large aggregates of glycogen-like granules, (6) numerous small, tubular mitochondria, (7) well-developed Golgi centers and (8) striking arrays of microtubules. These cells have many cytological features in common with the androgenic gland cells of crustaceans, but not with the steroidogenic cells of vertebrates. Evidence for the formation of protein granules is also lacking. As yet, experimental procedures have not indicated an endocrine function for these cells in tenebrionids. However, their cytology is consistent with secretory activity of some kind.     

Factors controlling soil development in sand dunes: evidence from a coastal dune soil chronosequence

Aerial photographs, maps and optically stimulated luminescence dates were combined with existing soil data to construct high resolution chronosequences of soil development over 140 years at a temperate Atlantic UK dune system. Since soil formation had progressed for varying duration under different climate and nitrogen deposition regimes, it was possible to infer their relative influence on soil development compared with location-specific variables such as soil pH, slope and distance to the sea. Results suggest that soil development followed a sigmoid curve. Soil development was faster in wet than in dry dune habitats. In dry dunes, rates were greater than in the literature: they increased with increasing temperature and nitrogen deposition and decreased with increasing summer gales. The combination explained 62% of the variation. Co-correlation meant that effects of nitrogen deposition could not be differentiated from temperature. In wet dune habitats rates increased with temperature and decreased with gales. The combination explained only 23% of the variation; surprisingly, rainfall was not significant. Effects of location-specific variables were not significant in either habitat type. Nitrogen accumulation was faster in wet than dry dune habitats, averaging 43 kg N ha^?1 per year overall. Nitrogen accumulation greatly exceeded inputs from atmospheric deposition, suggesting rates of input for biological N fixation are 10–60 kg N ha^?1 per year. Recent climate and/or nitrogen deposition regimes may have accelerated soil development compared with past rates. These data suggest the importance of changing climate on soil development rates and highlight the contribution of biological N fixation in early successional systems.