A new genus and species of passerine from the eastern rain forest of Madagascar

Cryptosylvicola randrianasoloi is described as a new genus and species in the family Sylviidae. This bird is endemic to the rain forests of eastern Madagascar, where it is restricted to elevations between 900 and 2100 m a.s.l. Cryptosylvicola randrianasoloi is distinguished from other Malagasy, African and Asian taxa by plumage colouration, external morphological characters and voice. The discovery of this new taxon in several well-known areas of Madagascar, and the fact that it has a relatively broad distribution in that country, indicates that much still remains to be learned about the biota of the island.     

Effects of host-odour plume altitude and changing wind velocity on upwind flight manoeuvres of a specialist braconid parasitoid

Abstract. Females of the specialist parasitoid, Microplitis croceipes (Cresson) (Hymenoptera: Braconidae), were released in a wind tunnel into host-odour plumes dispersed by winds of three velocities and winds whose speed was changed while the wasps were engaged in upwind flight. In steady winds of 61, 122 and 183 cms-^-1, wasps maintained similar 'preferred' ground speeds by adjusting their airspeed, while turning to a lesser degree as wind velocity increased. In winds of changing velocity (either increasing or decreasing within a 60–100 cm s-¹ range), wasps lowered their rate of upwind progress, leading to more tortuous tracks. During changing wind speeds longitudinal image flow decreased. Wasps flying in host-odour plumes 10 cm and 20 cm above the flight tunnel floor in a 122 cm s-¹ wind had similar ground speeds; thus their rate of ventral visual image flow varied two-fold. M.croceipes may 'aim' upwind by comparing how changes in the course angle vary with the direction of visual image flow. During changing wind velocities the relationship between changes in visual and flight muscle generated torque is ambiguous. Under these conditions most wasps cast, a manoeuvre characterized by wide lateral excursions across the wind without upwind progress. Once wind speed stabilizes, flight straightens out and upwind flight resumes.     

Competitive dominance in the organisation of Mediterranean ant communities

1. Competition by dominant species is thought to be key to structuring ant communities. However, recent findings suggest that the effect of dominant species on communities is less pronounced than previously assumed. 2. The aim of the present study was to identify the role of dominant ants in the organisation of Mediterranean communities, particularly the role of competition in invaded and uninvaded communities. The effects on ant assemblages of two dominant ants, the invasive Argentine ant and the native ant, Tapinoma nigerrimum Nylander, were assessed. 3. The abundances of both dominant ants were significantly correlated with a decrease in native ant richness at traps. However, only the invasive ant was associated with a reduction in diversity and abundance of other ant species at site scale. In the presence of T. nigerrimum, species co‐occurrence patterns were segregated or random. Community structure in both the dominant‐free and the Argentine ant sites showed random patterns of species co‐occurrence. 4. The present findings indicate that dominant ants regulate small‐scale diversity by competition. However, at the broader scale of the assemblage, T. nigerrimum may only affect species distribution, having no apparent effect on community composition. Moreover, we find no evidence that inter‐specific competition shapes species distribution in coastal Mediterranean communities free of dominant ants. 5. These results show that dominant species may affect ant assemblages but that the nature and the intensity of such effects are species and scale dependent. This confirms the hypothesis that competitive dominance may be only one of a range of factors that structure ant communities.     

Resistance of Drosophila suzukii to the larval parasitoids Leptopilina heterotoma and Asobara japonica is related to haemocyte load

Unlike other Drosophila species, the invasive Drosophila suzukii Matsumura (Diptera: Drosophilidae) shows a remarkable pest status. Among the physiological traits that may explain the high level of resistance to parasitoids of Drosophila larvae, the haemocyte load is shown repeatedly to play an important role. To determine whether haemocyte load can explain immunity resistance of D. suzukii to parasitoids, the haemocytes of parasitized and healthy larvae are quantified in two Japanese and three French populations of D. suzukii. Parasitization tests are conducted with two larval parasitoids: the paleartic Leptopilina heterotoma Thomson (Hymenoptera: Figitidae) and the Asian Asobara japonica Belokobylskij (Hymenoptera: Braconidae). Based on morphological and functional criteria, D. suzukii has classes of haemocytes similar to those described in Drosophila melanogaster. However, healthy larvae of the five populations tested possess particularly large numbers of haemocytes compared with D. melanogaster. Haemocyte load is also higher in larvae from the French populations than in the Japanese strains. The ability of D. suzukii larvae to encapsulate eggs of L. heterotoma is associated with a particularly high load of circulating haemocytes. However, it is notable that A. japonica induces a strong depression of the haemocyte population in this resistant host associated with an inability to encapsulate parasitoid eggs. The results show that the cellular immune system plays a major role in the failure of larval parasitoids to develop in most instances in larvae of D. suzukii, possibly contributing to the success of this species as an invader.     

Spatial variability in macroinvertebrate assemblages along and among neighbouring equatorial glacier‐fed streams

1. During the past two decades, understanding of the structure and function of glacier‐fed stream ecosystems at temperate latitudes has increased substantially. In contrast, information on their tropical counterparts is very limited. We studied three neighbouring glacier‐fed streams in the tropical Andes of Ecuador. Our main goals were (i) to determine overall longitudinal patterns in density, taxon richness and the composition of macroinvertebrate assemblages and driving factors in equatorial glacial streams and (ii) to examine variability among replicate streams in faunal metrics and assemblages, and stream‐specific effects of supposed environmental key factors. 2. We measured four geographical and 17 environmental factors and collected five Surber samples (500 cm²) of macroinvertebrates at each of nine sites, three sites along three streams. The streams were located 1–5 km apart. In each stream, the three sites were placed at comparable distances from the glacier and were grouped as ‘upper’ (50–200 m), ‘middle’ (1.5 km) and ‘lower’ sites (3.5–5.6 km). 3. In total, 2200 individuals (64% chironomids) were collected and 47 taxa (30 dipterans, 18 of these Chironomidae) identified. Density ranged from 176 to 372 ind. m^?2, and the number of taxa ranged from 2 to 6 at the upper sites and 868–3044 ind. m^?2 and 21–27 taxa at the lower sites. Density, number of taxa, rarefied richness and axis‐1 coordinates from a MDS ordination increased logarithmically with distance from the glacier. These faunal metrics were equally related to altitude and glacier per cent of catchment and correlated with maximum conductivity, mean temperature, mean daily maximum temperature and a channel stability index. As expected, the mean difference in distance decay in similarity was higher at the upper (47% km^?1) than at the lower reaches (20% km^?1) of the streams. 4. The number of taxa varied among sites within the upper and middle groups, but not among the lower sites. In contrast, but in accordance with our expectation, assemblage composition did not differ among upper sites but did so at middle and lower sites, following a supposed decrease in environmental harshness along the streams. Relationships between faunal metrics and the four environmental variables mean temperature, the stability index, chlorophyll a and coarse particulate organic matter also varied among the three streams. Generalised linear model analyses revealed that temperature interacted with stream on macroinvertebrate density, while chlorophyll a had a significant effect on the number of taxa in interaction with stream and stability. 5. The basic predictions of the Milner et al. (2001a) , model regarding longitudinal faunal patterns and temperature and stability as main driving factors were met by our three replicate equatorial glacial streams. Qualitative departures from the model were mainly because of zoogeographical differences. We demonstrated that variability in assemblages between comparable sites in closely situated streams was considerable, and the effect of key environmental factors varied among streams and interacted with other factors. Quantifying spatial variation in benthic assemblages may help us foresee possible consequences for biodiversity as a result of glacial retreat.     

Reproductive dynamics of three amphibian species in Mediterranean wetlands: the role of local precipitation and hydrological regimes

1. Although the influence of water availability and precipitation regimes on amphibians has been studied at large scales, whether and how interannual rainfall and hydrological variations affect amphibians dynamics at a local scale have rarely been addressed. In this respect, accounting for variations in species detectability in space and time has also been overlooked. 2. We assessed the effects of rainfall and hydrological variations on the breeding dynamics of three amphibian taxa: Pelodytes punctatus, Hyla meridionalis and Pelophylax spp. in 20 ponds of the Camargue region (southern France) over a 7‐year study period. 3. We used multiple season occupancy models to test the effect of winter–spring rainfall and interannual variations in hydroperiod, mean water depth and drought events on tadpole presence in spring (March–June), a proxy for breeding dynamics. 4. We used an independent survey with spatial replicates (dipnet sweeps) to disentangle the relative contributions of phenology and detectability to the absence of records in a given month. For the three taxa considered, the probability of missing a species when that species was actually present in a pond was most often negligible. Hence, we could consider that multiseason models properly tracked changes in species phenology. 5. Pelodytes punctatus was first detected in March, while the two other taxa appeared later in April. Hyla meridionalis appeared as a mid‐season species with much more synchronous pond occupancy than Pelodytes punctatus. The detection peak of Pelophylax spp. was short and unexpectedly early for this taxon. 6. Seasonal winter–spring rainfall was associated with a decrease in extinction rates and even more strongly with an increase in colonisation rates at individual ponds. 7. Colonisation rate increased following an annual drought and was best modelled as a negative quadratic effect of the variance of pond hydroperiod. Extinction probability was best modelled by a negative quadratic effect of mean water level. Hence, breeding was more stochastic (i) in unpredictable and shallow ponds because of yearly drying up and (ii) in highly predictable and deep ponds, possibly due to the presence of predators such as fish and crayfish. 8. Overall, we show that ponds with intermediate rather than extreme variations in environmental conditions currently correspond to optimal breeding sites. Our study demonstrates that amphibian monitoring coupled with fine‐scale analysis of environmental conditions is necessary to understand species dynamics in the long run and to inform conservation efforts for these species.     

Nine polymorphic microsatellite markers in Crepis sancta (Asteraceae)

We describe nine new variable di‐ and trinucleotide microsatellites in the plant Crepis sancta, as well as conditions for multiplexing and simultaneous genotyping sets of loci. Their variability was assessed in four populations. Four to 33 alleles were detected per locus; two to 23 alleles per population. Significant deviations from Hardy–Weinberg equilibrium could be attributed either to a mating system involving partial selfing or to null alleles. Genetic differentiation over all loci was significant among the four populations studied. These markers will constitute an efficient tool for investigating dispersal patterns in fragmented landscapes. Cross‐species amplification provided few loci variability in three other Crepis species (C. pulcra, C. foetida and C. rubra).     

Invertebrate hydraulic preferences and predicted impacts of changes in discharge in a large river

• 1 Instream habitat models are attractive tools for assessing the impacts of flow restoration on aquatic organisms, but have been rarely used for invertebrates due to the lack of knowledge of their hydraulic preferences.
• 2 In this study, we provide quantitative models of the hydraulic preferences for 66 invertebrate taxa found in the Upper Rhône River (France), and combine these preferences with a statistical habitat model (FSTress) to predict the effects of minimum flow restoration on invertebrate abundances in two bypassed sections of the river.
• 3 Many taxa show marked preferences for particular hydraulic conditions. Average preferred hydraulic conditions were significantly related to those observed in smaller streams (R² = 0.37).
• 4 Our model predicted that habitat values of 27 taxa should be enhanced by restoration operations, but also predicted a decrease of habitat values in the main channel for 12 limnophilic taxa. However, these taxa are expected to maintain populations by finding refuges in restored cut‐off channels and overall invertebrate diversity is predicted to increase in the two bypassed sections studied here.

     

Plumage development and moult in the European Quail Coturnix c. coturnix: criteria for age determination

Sequence, rate and duration of moult were studied in captive bred European Quail Coturnix coturnix coturnix. The founder population originated from southwest France. The study was conducted between 1986 and 1989 on birds aged from 1 day to 2 years, exposed to a seasonal photoperiod corresponding to latitude 16°N during autumn and winter and latitude 48°N during the remainder of the year. Under these conditions, adult quail showed two annual moults with only the post-breeding one being complete. The pre-breeding moult essentially involved the throat feathers. Large interindividual variation was observed in the duration, timing and development of the post-breeding moult: 60% of the studied birds suspended moult when they developed migratory restlessness and then finished renewing their feathers during the winter. The post-juvenile moult was also suspended when 7–9 weeks old (3–6 primaries and 1–10 secondaries renewed). After this suspension, the length of which was related to the hatching date, the moult continued up to p7. The three outer primaries were kept for the first year and were replaced only during the post-breeding moult. Based on the examination of wing patterns, our study provides reliable criteria for discriminating between age classes. The numbers of primaries and secondaries simultaneously in growth or renewed were different between the age classes. The secondaries of adults were renewed later in the moult stage than were the secondaries of juveniles. These criteria provide field researchers with a guide that enables them to age quail with reasonable accuracy.     

Feeding mechanics in Triassic stem-group sauropterygians: the anatomy of a successful invasion of Mesozoic seas

The jaw adductor musculature in Triassic stem-group sauropterygians is reconstructed on the basis of a paradigmatic model of muscle architecture (functional equivalence of sarcomeres) and using invariant traits of the anatomy of the trigeminal jaw adductor muscles in extant reptiles. The reconstructed jaw adductor musculature predicts trophic specializations in stem-group sauropterygians. Suction feeding is a component in prey capture for some benthic feeding, as well as for some pelagic feeding taxa. The differentiation of 'pincer' jaws is correlated with the potential for rapid, snapping bites. There is some evidence for habitat partitioning among Triassic stem-group sauropterygians with respect to trophic specialization. © 2002 The Linnean Society of London. Zoological Journal of the Linnean Society , 2002, 135 , 33–63.