Search publications of the members of the Royal Belgian institute of natural Sciences
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The gynogenetic reproduction of diploid and triploid hybrid spined loaches (Cobitis: Teleostei), and their ability to establish successful clonal lineages - On the evolution of polyploidy in asexual vertebrates
- Polyploidisation is assumed to have played a significant role in the evolution of hybrid asexual lineages. The virtual absence of natural asexual systems in which more than a single ploidy level successfully establishes successful independent clonal lineages is generally explained by the strong effects of polyploidisation on fitness. Experimental crosses were made between diploid and triploid asexual Cobitis elongatoides x C. taenia hybrids (female) and both parental spined loach species (male). Genotyping of the progeny using allozymes and multilocus DNA fingerprinting, along with flow cytometric measurement of ploidy level, demonstrated the occurrence of gynogenetic reproduction in both female biotypes. The incorporation of the sperm genome occurred in some progeny, giving rise to a higher ploidy level, but the rate of polyploidisation differed significantly between the diploid and triploid females. These outcomes are consistent with the existence of developmental constraints on tetraploidy, which determine the rarity of tetraploids in natural populations. No cases of ploidy level reduction were observed. Since diploid and triploid hybrid populations occur where the lack of potential progenitor excludes the possibility of de novo origin, it is probable that both diploid and triploid females can establish successful clonal lineages. Spined loaches represent a unique example, among asexual vertebrates, where more than one ploidy level can establish persistent clonal lineages, which are reproductively independent of one another. © 2007 Springer Science+Business Media, Inc.
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Phylogeography of western Palaearctic reptiles - Spatial and temporal speciation patterns
- A phylogeographic analysis of eight species complexes of European reptiles was performed using different molecular methods. While mitochondrial genes (mainly cytochrome b sequences) enabled conclusions about phylogeography and differentiation, additional application of bisexually inherited markers provided information about speciation stages. As species with similar distribution patterns in southern and Central Europe were selected, matching phylogeographic patterns are useful for drawing general conclusions:(1)The species complexes are in different stages of speciation. In some cases, cryptic species were detected.(2)Highest genetic diversity occurs in southern Europe, the Near East and the Caucasus, regions corresponding with glacial refuges in the Iberian, Apennine and Balkan Peninsulas as well as in Turkey and the Caucasus. Often, several microrefugia must have existed in close neighbourhood. Additional microrefugia were located in southern France and in the Carpathian Basin.(3)North Africa and the Middle East did not serve as glacial refuges for Central or northern European lineages and are typically inhabited by independent clades.(4)Evidence for multiple range retractions and expansions, which were postulated for the times of Pleistocene climatic oscillations, could be found in the Balkans, but in Central Europe their traces have been wiped out by the last glacial. Only the Holocene invasion has left imprints in the genomes from this area.(5)Central and northern Europe were recolonized from Balkan and Pontic refugia in the Holocene.(6)Groups from the Iberian and Apennine Peninsulas rarely conquered other regions. This limitation can be attributed to the barrier function of the Pyrenees and the Alps. © 2007 Elsevier GmbH. All rights reserved.
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Effects of mating, breeding system and parasites on reproduction in hermaphrodites: Pulmonate gastropods (Mollusca)
- There are approximately 20 000 pulmonate gastropod species that are all hermaphroditic and (with a few exceptions) can act in both (i.e., male and female) sexual roles. Life history traits such as growth (rate), age at first reproduction, fecundity, fertility, future survival and offspring survival are highly variable within pulmonate species, even among individuals of the same population. Here, we review some aspects of reproduction (availability of partners, size-dependent sex allocation, courtship, (multiple) mating, sperm longevity/viability, social facilitation), breeding system (selffertilisation, outcrossing or mixed) and parasitism that may influence an individual's reproductive success and therefore account for part of the intraspecific variation in life history traits. A literature study showed that fecundity, fertility and/or growth are significantly affected by: i) the mating group size through changes in interference competition (e.g., crowding), breeding system and sex allocation; ii) individual body size with larger individuals producing more eggs than smaller individuals; iii) mating whereby female fitness may be positively or negatively affected; iv) social facilitation whereby female fitness is positively affected by the presence of conspecifics; v) the breeding system including the phenomena of inbreeding and outbreeding depression; and vi) parasites that may suppress or stimulate reproduction, especially egg-laying, in parasitised individuals. Moreover, multiple mating and multiple paternity seem very common in pulmonates. Interestingly, several of the above-mentioned aspects seem to interact or even act synergetically. Although many aspects of life history variation in pulmonate gastropods are still poorly understood which makes it difficult to draw general conclusions, pulmonates offer ample opportunities to study the evolution of major topics in evolution and life history strategies. Indeed, there is a growing number of basommatophoran and stylommatophoran model species, experimental setups and molecular, histological and histochemical techniques that are used to test current hypothesis on sex allocation, sexual selection (sexual conflict, sperm competition or cryptic female choice), the evolution of breeding systems and host-parasite interactions which will yield much information for the study of life history strategies as well. © Koninklijke Brill NV 2007.
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Metallothionein gene and protein expression as a biomarker for metal pollution in natural gudgeon populations
- Gudgeons (Gobio gobio) from historically Cd and Zn contaminated sites in Flanders (Belgium) were found to be resistant to elevated Cd levels. In previous work, this increased resistance was largely explained by increased metallothionein (MT) expression. Recently, environmental cleanup efforts resulted in a significant decrease in Cd concentrations in the surface water. In this study, we evaluated the use of hepatic metal and metallothionein (MT) concentrations as biomarkers of metal exposure before and after the cleanup. Hepatic MT mRNA levels were determined after the environmental metal levels decreased in order to assess the applicability of MT gene expression as an environmental biomarker in natural fish populations. Our data show that both metallothionein protein and gene expression have the potential to be sensitive biomarkers for metal exposure. Significant correlations were found (a) among accumulated metal concentrations and both MT protein and mRNA levels, and (b) between MT protein and mRNA levels. However, our data illustrated that while MT protein and gene expression give a quantitative picture of metal load at a single time point, quantitative information in natural populations cannot always be obtained when different time points (including different years) are compared, since MT gene and protein expression are affected by many other factors in addition to the metal load. Furthermore, the result of the environmental cleanup was reflected in a decrease of hepatic Cd concentrations. Zn remained the most important factor determining MT concentrations. Finally, two differently sized MT mRNAs were amplified to test the hypothesis that 3′-UTR length can offer a protective advantage in conditions of environmental stress. Our data provided no evidence to support this hypothesis. In contrast, the ratio of the long mRNA variant relative to total MT mRNA was surprisingly constant, and independent of exposure history. © 2007 Elsevier B.V. All rights reserved.
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First record of the rotifer Lecane shieli Segers and Sanoamuang, 1994 from Australia
- The monogonont rotifer Lecane shieli is recorded for the first time from Australia (Bora Channel in the Macquarie Marshes, New South Wales: 30.65872° S/147.53 144° E). Until recently, L. shieli was known only from Thailand, where the species was first described. This Australian record of a Thai 'endemic' is interesting in considering possible dispersal and biogeographical distribution.
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Stefania evansi (Groete Creek carrying frog): Froglet carrying
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A new species of Allobates (Anura: Aromobatidae: Allobatinae) exhibiting a novel reproductive behaviour
- A new species of Allobates is described from the Mabura Hill Forest Reserve, central Guyana, South America. The new species is distinguished from congeneric species by cryptic colouration, very small size, first finger longer than second, third finger not distinctly swollen in males, absence of lateral fringes on fingers and toes, complete lateral black band present, diffuse pale dorsolateral stripe present, diffuse, pale, partial oblique lateral stripe present, pale ventrolateral stripe present, throat in adult males pale, and unique advertisement call and reproductive behaviour. The new species occasionally deposits tadpoles in leptodactylid foam nests, which constitutes the first case of interspecific brood parasitism in frogs. Copyright © 2007 Magnolia Press.
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Suspended matter in the Scheldt estuary
- The Scheldt estuary is characterised by a specific energy pattern resulting from the interaction of wave energy, tidal energy and river energy. It divides the estuary into three parts and governs suspended matter transport and distribution pattern. Observation of suspended matter transport shows the existence of three estuarine turbidity maxima (ETM), a marine-dominated ETM in the lower estuary at the river mouth, a river-dominated ETM in the upper estuary with suspended matter concentration reaching up to 300 mg/l, and the most important tide-dominated ETM in the middle estuary with suspended matter concentrations from several hundred milligrams per litre up to a few grams per litre. Resuspension is the dominant phenomenon in this last ETM due to the tidal related bottom scour, which is initiated when a critical erosion velocity of 0.56 m/s is exceeded. An assessment of residual current along the axis of the estuary shows distinctive pattern between the surface water flow and the near bottom water flow. Also the local morphology of the river, natural or man-made, has a prominent effect on the orientation and strength of the residual currents flowing along either side of the river or river bend. Evaluation of suspended matter concentration in relation to the current flow shows no systematic correlation either because of phenomena as scour lag and settling lag mainly in the middle estuary, or because of the current independency character of uniform-suspension mainly in the upper and lower estuary. Quantification of suspended matter load exhibits a net downstream transport from the upper estuary, a near-equilibrium sustainable status in the middle estuary and a net upstream transport of suspended matter from the lower estuary. The characteristic of suspended matter is induced by and is a function of e.g. tidal phase, spring-neap tide, longitudinal and vertical distribution mechanisms, seasons, short and long terms of anthropogenic influence and/or estuarine maintenance. Suspended matter is dominated by complex and cohesive organo-mineral aggregates. It consists of a variable amount of an inorganic fraction (average of 89\%) and an organic fraction and occurs largely as flocs, the size of which is remarkably larger in the upper estuary and smallest within the ETM in the middle estuary. Independent time series measurements (1990-2000) of suspended matter property show an increasing sand fraction, a decreasing organic matter content, a rise in δ13C as well as a decrease in water transparency. These independent measurements exhibit coherent consequences of estuarine maintenance operations. Maintenance dredging of the shipping channel and harbours and dumping operation in the Scheldt strengthen marine influence further landward, resulting in a sustained tidal range increment and upstream flow and transport of suspended matter. © Springer 2005.
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Restoration of tropical peat swamp rotifer communities after perturbation: An experimental study of recovery of rotifers from the resting egg bank
- In order to assess the recovery potential of tropical freshwater communities after disturbance, we performed an experimental study on the effects of exposure conditions and durations of storage on hatching of rotifer resting eggs in sediment. Well-mixed surface sediment samples from Mai Khao peat swamp on Phuket Island, Thailand, were stored under three conditions (cold -4°C & dark: CD; ambient -32-42°C & dark: AD; and ambient & daylight conditions: AL), for different periods of time (1, 2, 4, 6, 12, 18 and 24 months). The number of species hatching from the sediment was significantly affected by treatment for both short- (1-6 months) and long-term (6-20 months) exposure. Significant effects of short- and long-term exposure within treatments were also present. Both factors interacted significantly. Regarding numbers of specimens hatching, no short-term effects of differences in treatment condition were found, but increasing the duration did have an effect. Significant effects of treatment occurred after 6 months, in addition to prolonged effects of duration. Again, both factors interacted significantly. These experiments indicate that exposure time has a strong impact on the viability of resting eggs, whereas, an effect of exposure condition appears only after 6 months. So, recovery of rotifer communities from resident sediment egg banks in disturbed peat swamps can only be effectively attained when restoration occurs within a relatively short period after perturbation. © Springer 2005.
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Phylogenetic systematics of the Empis (Coptophlebia) hyalea-group (Insecta: Diptera: Empididae)
- Six clades are inferred from a phylogenetic analysis including 42 species belonging to the Empis (Coptophlebia) hyalea-group. These clades are named as follows: E. (C.) acris, E. (C.) aspina, E. (C.) atratata, E. (C.) hyalea, E. (C.) jacobsoni and E. (C.) nahaeoensis. The presence of two dorsal more or less developed epandrial projections is considered autapomorphic for the E. (C.) hyalea-group in addition to two characters previously found to support the monophyly of this group (presence of an unsclerotized zone in the middle of labella and epandrium unpaired). Amongst the cladistically analysed species, 24 are newly described [E. (C.) acris, E. (C.) aspina, E. (C.) cameronensis, E. (C.) duplex, E. (C.) incurva, E. (C.) inferiseta, E. (C.) kuaensis, E. (C.) lachaisei, E. (C.) lamellalta, E. (C.) lata, E. (C.) loici, E. (C.) longiseta, E. (C.) mengyangensis, E. (C.) menglunensis, E. (C.) missai, E. (C.) nimbaensis, E. (C.) padangensis, E. (C.) parvula, E. (C.) projecta, E. (C.) pseudonahaeoensis, E. (C.) submetallica, E. (C.) urumae, E. (C.) vitisalutatoris and E. (C.) woitapensis], five are reviewed [E. (C.) hyalea Melander, E. (C.) jacobsoni De Meijere, E. (C.) ostentator Melander, E. (C.) sinensis Melander and E. (C.) thiasotes Melander] and 13 were recently described in two previous papers. Two additional species, E. (C.) abbrevinervis De Meijere and E. (C.) multipennata Melander, are also reviewed but not included in the cladistic analysis since they are only known from the female. A lectotype is designated for E. (C.) jacobsoni. A key is provided to the six clades of the E. (C.) hyalea-group as well as to species of each clade. A catalogue of the E. (C.) hyalea-group, including 72 species, is given. The taxonomic status of 25 additional species mainly described by Bezzi and Brunetti, from the Oriental and Australasian regions, is discussed. The E. (C.) hyalea-group is firstly recorded from the Palaearctic Region and Australia. Finally, the distribution and the habitats of the species compared with their phylogeny suggest a possible relationship between the diversification of the group and forest fragmentations during the Quaternary. © 2005 The Linnean Society of London.
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Empidine dance flies from Singapore and southern Malaysia (diptera: Empididae: Empidinae)
- Five new species belonging to the Empis (Coptophlebia) hyalea-group are described, namely E. (C.) neesoonensis, new species, E. (C.) producta, new species, E. (C.) tortuosa, new species, E. (C.) triseta, new species and E. (C.) verruca, new species. A key to all known species of the group is provided for Singapore and Southern Malaysia. © National University of Singapore.
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Atypical mating behaviour in the empidine dance fly Rhamphomyia (Lundstroemiella) magellensis (Diptera : Empididae : Empidinae)
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Spatiotemporal allozyme variation in the damselfly, Lestes viridis (Odonata: Zygoptera): Gene flow among permanent and temporary ponds
- Several insect species seem to persist not only in permanent but also in temporary ponds where they face particularly harsh conditions and frequent extinctions. Under such conditions, gene flow may prevent local adaptation to temporary ponds and may promote phenotypic plasticity, or maintain apparent population persistence. The few empirical studies on insects suggest the latter mechanism, but no studies so far quantified gene flow including both pond types. We investigated the effects of pond type and temporal variation on population genetic differentiation and gene flow in the damselfly Lestes viridis in northern Belgium. We report a survey of two allozyme loci (Gpi, Pgm) with polyacrylamide gel electrophoresis in 14 populations from permanent and temporary ponds, and compared these results with similar data from the same permanent populations one year before. The data suggested that neither pond-drying regime, nor temporal variation have a substantial effect on population genetic structuring and did not provide evidence for stable population differentiation in L. viridis in northern Belgium. Gene flow estimates were high within permanent and temporary ponds, and between pond types. Our data are consistent with a source-sink metapopulation system where temporary ponds act as sinks in dry years, and are quickly recolonized after local population extinction. This may create a pattern of apparent population persistence of this species in permanent and temporary ponds without clear local adaptation. © Springer 2005.
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Mitochondrial DNA variation and cryptic speciation within the free-living marine nematode Pellioditis marina
- An inverse correlation between dispersal ability and genetic differentiation among populations of a species is frequently observed in the marine environment. We investigated the population genetic structure of the free-living marine nematode Pellioditis marina. A total of 426 bp of the mitochondrial cytochrome oxidase subunit 1 (COI) gene were surveyed on a geographical scale of approximately 100 km during spring 2003. Nematodes were collected from 2 coastal locations in Belgium, and from 2 estuaries and a saltwater lake (Lake Grevelingen) in The Netherlands. Molecular variation was assessed with the single-strand conformation polymorphism (SSCP) method. In total, 32 different haplotypes were observed, and sequence divergence among 452 individuals ranged from 0.2 to 10.6\%. We discovered 4 distinct mitochondrial lineages, with low divergences within the lineages (0.2 to 1.6\%) and high divergences between the lineages (5.1 to 10.6\%). The nuclear ribosomal ITS (internal transcribed spacer) region showed concordant phylogenetic patterns, suggesting that nematode species diversity may be considerably underestimated. Analysis of molecular variance (AMOVA) indicated a strong genetic differentiation among populations. The Lake Grevelingen population was clearly differentiated from all other populations, but genetic structuring was also significant within the Westerschelde and was correlated with gradients in salinity and pollution. The observed population genetic structure is in accordance with the limited active dispersal capacity of P. marina, but is at variance with its significant potential for passive dispersal. We therefore suggest that autecological characteristics, including short generation time, high colonization potential and local adaptation, may be at the basis of this nematode's population genetic structure. © Inter-Research 2005.
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A wingless intertidal ground beetle, new to the Belgian fauna, in the river IJzer estuary nature restoration site: Bembidion nigropiceum Marsham, 1802
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Bottlenecks, drift and differentiation: The fragmented population structure of the saltmarsh beetle Pogonus chalceus
- We investigated the distribution of genetic variation within and between 10 fragmented populations of the saltmarsh beetle Pogonus chalceus in the region of Flanders (Belgium) representing all extant populations of the species in that region by using allozyme and microsatellite markers. Beetle population size and habitat area failed to explain a significant part of the genetic variability. Microsatellite allelic diversity was sensitive to population size differences but not to saltmarsh area estimates. Heterozygosities of both marker types and allozyme allelic diversity on the other hand showed no significant correlation to population size and saltmarsh area. There was also no correlation between geographical and genetic distances among populations. Evidence was found for past bottlenecks in some of the smallest populations. Maximum likelihood methods using the coalescent approach revealed that the proportion of common ancestors was also high in those small populations. 35\% of our studied individuals, especially in the largest populations showed a relative wing size smaller than 70\%. Moreover, only six out of the 10 studied populations showed a few individuals with functional flight musculature. In conclusion, the overall pattern of distribution of genetic variation and the low flight capacity did not support an equilibrium model of population structure in P. chalceus, but mainly suggested a lack of regional equilibrium with both drift and gene flow influences. © Springer 2005.
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Genetic differentiation among populations of the salt marsh beetle Pogonus littoralis (Coleoptera: Carabidae): A Comparison between Atlantic and Mediterranean populations
- Genetic differentiation was studied among populations of the salt marsh beetle Pogonus littoralis (Coleoptera: Carabidae), comparing Atlantic and Mediterranean populations over a large part of its range. The genetic structure of this highly mobile beetle was investigated by studying allozyme polymorphism at nine enzyme loci in 13 populations. Mediterranean P. littoralis were highly significantly differentiated from Atlantic populations. Moreover, more isolated Atlantic populations showed increased differentiation and decreased genetic diversity compared to less fragmented Mediterranean populations. © The American Genetic Association. 2005. All rights reserved.
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Linking science and policy for biodiversity
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The continuous exploitation of wild animal resources in the archaeozoological record of Ghana
- The paper provides a critical review of the archaeozoological information from Ghanaian sites published up to now and summarizes the new faunal analysis of several Gonja and Asante sites. The data suggest the persistence of the use of the various wild animal resources available and limited reliance on domestic animals since late prehistoric times up to today, although certain resources such as molluscs, insects etc. may have limited or no visibility. Intensive utilisation of edible wild resources may be prevalent in African woodlands.
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Post-storm surveys reveal large-scale spatial patterns and influences of site factors, forest structure and diversity in endemic bark-beetle populations
- The storm that struck France on december 26th and 28 th 1999 felled 140 million m3 of timber and had a high economic, social and landscape impact. This event offered the opportunity to study large-scale patterns in populations of forest insect pests that would benefit from the abundant breeding material. A large-scale survey was carried out in France in 2000 to sample the most frequently observed species developing on spruce (Ips typographus, Pityogene schalcographus) and pine (Tomicus piniperda, Ips sexdentatus) in 898 locations distributed throughout wind-damaged areas. The local abundance of each species scored on a 0 to 5 scale was analysed using geostatistical estimators to explore the extent and intensity of spatial autocorrelation, and was related to site, stand, and neighbourhood landscape metrics of the forest cover (in particular the interconnection with broadleaf forest patches) found within dispersal distance. All species but I. sexdentatus, which was much less abundant, displayed large-scale spatial dependence and regional variations in abundance. Lower infestation levels per tree (windfalls and standing trees) were observed in stands with a high proportion of wind-damaged trees, which was interpreted as the result of beetles distributing themselves among the available breeding material. More infestations were observed in wind-broken trees as compared to wind-felled trees. More importantly, populations showed significant relationships with the structure of coniferous stands (in particular with the number of coniferous patches). T. piniperda population levels were negatively correlated to the amount of coniferous edge shared with broadleaf forest patches, possibly because of the disruptive effect of non-host volatiles on host-finding processes at the landscape-scale. The differences observed between species regarding patterns and relationships to site, stand, and forest cover characteristics are discussed in relation to the ecological characteristics of each species. © Springer 2005.
