The importance of male and female acoustic behaviour for reproductive isolation in Ribautodelphax planthoppers (Homoptera: Delphacidae)

The importance for reproductive isolation of species-specific acoustic differences between closely related Ribautodelphax planthopper species is tested by measuring responses to playbacks of both conspecific and heterospecific signals. Females respond to heterospecific male calls at about 80% of the conspecific response level, irrespective of the degree of cross-insemination of the combination involved. In a combination involving R. albostriatus , a taxonomically more distantly related species, female response levels are only 15–33% of the normal level. Study of the development of both female responsiveness and receptiveness shows that response levels correspond fairly well with insemination levels. Female heterospecific response is far too high to explain isolation between the species. Female answers to heterospecific males calls have normal response-delay times and durations. When offered a two-way choice between female playback calls, males significantly more often approach the conspecific call in almost all combinations tested. Offering only a heterospecific female signal induces males to call, but not to search. Males are capable of maintaining at least part of the sexual isolation by distinguishing between different female calls. This seems in conflict with the popular theory that the sex with the greater parental investment, here the female, should be exerting the choice.     

Molecular and morphological data reveal cryptic taxonomic diversity in the terrestrial slug complex Arion subfuscus/fuscus (Mollusca, Pulmonata, Arionidae) in continental north-west Europe

The importance and abundance of cryptic species among invertebrate taxa is well documented. Nowadays, taxonomic, phylogenetic and conservation biological studies frequently use molecular markers to delineate cryptic taxa. Such studies, however, often face the problem of the differential resolution of the molecular markers and techniques involved. This issue is explored in the present study of cryptic taxa within the terrestrial slug complex Arion subfuscus/fuscus in continental north-west Europe. To this end, morphological, allozyme and mitochondrial 16S rDNA sequence data have been jointly evaluated. Using allozyme data and gonad type, two distinct groups were consistently delineated, even under sympatric conditions. The 16S rDNA data strongly supported both those groups and even suggested the presence of three distinct taxa within one of them. However, in view of: (1) the allopatric distribution of three OTUs, (2) the lack of allozyme or morphological differentiation, and (3) the extremely high degree of intraspecific mtDNA variation reported in pulmonate gastropods, they are, for the time being, not regarded as valid species under the biological species concept. By means of 16S rDNA and allozyme data, the position of type and topotype material of A. subfuscus s.s. and A. fuscus relative to the newly defined OTUs was determined, thus clarifying the nomenclature of this species complex. Additionally, gonad type proved to be a useful character for distinguishing the two species in north-west Europe.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 83 , 23–38.     

Effects of elevated CO2 concentrations on photosynthesis, growth and reproduction of branches of the tropical canopy tree species, Luehea seemannii Tr. & Planch.

Mature trees have already experienced substantial increases in CO₂ concentrations during their lifetimes, and will experience continuing increases in the future. Small open-top chambers were used to enclose branchlets that were at a height of between 20 and 25 m in the canopy of the tree species Luehea seemannii Tr. & Planch. in a tropical forest in Panamá. Elevated concentrations of CO₂ increased the rate of photosynthetic carbon fixation and decreased stomatal conductance of leaves, but did not influence the growth of leaf area per chamber, the production of flower buds and fruit nor the concentration of nonstructural carbohydrates within leaves. The production of flower buds was highly correlated with the leaf area produced in the second flush of leaves, indicating that the branchlets of mature trees of Luehea seemannii are autonomous to a considerable extent. Elevated levels of CO₂ did increase the concentration of nonstructural carbohydrates in woody stem tissue. Elevated CO₂ concentration also they increased the ratio of leaf area to total biomass of branchlets, and tended to reduce individual fruit weight. These data suggest that the biomass allocation patterns of mature trees may change under future elevated levels of CO₂. Although there were no effects on growth during the experiment, the possibility of increased growth in the season following CO₂ enrichment due to increased carbohydrate concentrations in woody tissue cannot be excluded.     

An electrophoretic characterisation of three paratypes of Arion fagophilus De Winter, 1986, with notes on the subgeneric division of the genus Arion Férussac, 1819 (Mollusca, Pulmonata)

Three paratypes of Arion fagophilus were electrophoretically compared with nine other West European species of the genus Arion. Esterases, glutamate-oxaloacetate-transaminase, a-amylase, superoxide dismutase, phosphoglucomutase, fumarase, α-glycerophosphate dehydrogenase and phosphogluconate dehydrogenase were screened in the hepatopancreas and general proteins in the albumen gland. A. fagophilus appears to be a very well defined species, which may be assigned to the subgenus Kobeltia. The subgeneric division of the genus Arion is preliminary discussed with respect to electrophoretic and chromosomal data. It is concluded to retain four subgenera, which may be grouped two by two: Mesarion and Arion s. s. on one hand, and Kobeltia and Carinarion on the other. It is remarked that the electrophoretic differences between Norwegian and Belgian A. ater suggest a separation into two taxa.     

A panel of microsatellite markers to detect and monitor demographic bottlenecks in the riverine dragonfly Orthetrum coerulescens F.

Odonates (dragonflies and damselflies) are important indicators for monitoring anthropogenic impacts on freshwater ecosystems. We developed a panel of microsatellite loci for the keeled skimmer Orthetrum coerulescens, a libellulid dragonfly inhabiting small streams. By using two different isolation techniques, nine microsatellite loci have been isolated. Screening of 209 individuals resulted in an overall number of 88 alleles, ranging from three to 19 alleles per locus. The observed heterozygosity ranged from 0.37 to 0.83. One locus showed significant deviation from Hardy–Weinberg equilibrium.     

Polymorphic microsatellite loci to study population dynamics in a dragonfly,the libellulid Trithemis arteriosa (Burmeister, 1839)

One of the most widely distributed dragonfly species in Africa is the red‐veined‐dropwing Trithemis arteriosa. It is an indicator for permanent water bodies, which are freshwater ecosystems of high environmental value especially in arid regions. For studies to determine population structures, assess species viability and monitor environmental changes, a panel of 10 polymorphic microsatellite loci was developed. The number of alleles per locus ranged from four to 12, with an observed heterozygosity ranging from 0.149 to 0.843.     

Diatoms as indicators of river quality in the Nepalese Middle Hills with consideration of the effects of habitat-specific sampling

1. Using a replicated survey design at the catchment scale, we compared the composition and diversity of diatom communities in three stream groups in the Middle Hills of Nepal: semi-natural reference (Arun Valley), enriched by agricultural runoff (Likhu Khola) and grossly polluted by sewage (Kathmandu Valley). We sampled riffles at all sites; in the Kathmandu Valley and Likhu Khola we also sampled diatoms in pools and on vegetation.
2. Species richness and diversity H' were significantly higher in agricultural streams than in either organically polluted streams or references. Community composition, as shown by principal components analysis, varied significantly between all three stream types due to differences in the abundances of species characteristic of organic enrichment (Kathmandu Valley), moderate enrichment (Likhu Khola) or undisturbed hillstreams (Arun Valley).
3. Few species varied in relative abundance between pools, riffles and vegetation so that variations in community composition and diversity were stronger between stream groups than between habitats. Samples from any one habitat produced only 75.7% (± 8.6 SD) of the species from three habitats, so that surveys aimed at recording biodiversity may need more comprehensive habitat coverage than surveys for biomonitoring.
4. We conclude that diatom communities can indicate different sources of pollution in Nepalese streams, and advocate further studies to develop this indicator potential over a wider area of the Himalaya. Comparisons between replicate groups of streams selected a priori helped to clarify effects which were sometimes obscured by other survey designs.     

A panel of microsatellite markers to study sperm precedence patterns in the emperor dragonfly Anax imperator (Odonata: Anisoptera)

Odonates were the first group of organisms where sperm competition and last male sperm precedence have been identified. With the development of 10 microsatellites for the emperor dragonfly Anax imperator, the function and priority patterns of the multiple sperm storage organs of females can be studied and compared between species in natural populations. In addition, two microsatellite loci developed for the sister species Anax parthenope, are also highly polymorphic in A. imperator. For the presented 12 microsatellite loci, the number of alleles per locus ranged from two to 24. Observed heterozygosity ranged from 0.07 to 0.88.