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Carlo R Largiadèr

Publications and source records attributed to Carlo R Largiadèr.

6 recordsLinked to original sources
PubMed2006

Slow fertilization of stickleback eggs: the result of sexual conflict?

BACKGROUND: The fertilization success in sperm competition in externally fertilizing fish depends on number and quality of sperm. The time delay between sequential ejaculations may further influence the outcome of sperm competition. Such a time interval can load the raffle over fertilization if fertilization takes place very fast. Short fertilization times are generally assumed for externally fertilizing fish such as the three-spined stickleback (Gasterosteus aculeatus). In this pair-spawning fish, territorial males often try to steal fertilizations in nests of neighbouring males. This sneaking behaviour causes sperm competition. Sneakers will only get a share of paternity when eggs are not fertilized immediately after sperm release. Contrary to males, females may be interested in multiple paternity of their clutch of eggs. There thus may be a sexual conflict over the speed of fertilization. RESULTS: In this study we used two different in vitro fertilization experiments to assess how fast eggs are fertilized in sticklebacks. We show that complete fertilization takes more than 5 min which is atypically long for externally fertilizing fishes. CONCLUSION: This result suggests that the time difference does not imply high costs to the second stickleback male to ejaculate. Slow fertilization (and concomitant prolonged longevity of sperm) may be the result of sexual conflict in which females aimed at complete fertilization and/or multiple paternity.

Animals↗
PubMed2004

Inbreeding affects female preference for symmetry in computer-animated sticklebacks.

Fluctuating asymmetries are small random deviations from perfect symmetry in bilateral traits caused by the inability of individuals to cope with stress during development. The degree of asymmetry of secondary sexual characters is supposed to convey information about a male's phenotypic and/or genetic quality, and females are thus expected to use bilateral symmetry as a cue in mate choice. We offered female three-spined sticklebacks (Gasterosteus aculeatus L.) that had been inbred for one generation and outbred control females the choice between computer-animated male models differing exclusively in the symmetry of their pelvic spines. Inbred females exhibited a significantly stronger preference for the symmetric model than outbred females, suggesting that females of relatively poor quality are more prepared to pay the costs of choosiness and obtain higher marginal benefits from their discrimination than females of better quality.

Animals↗
PubMed2003

SNPs by AFLP (SBA): a rapid SNP isolation strategy for non-model organisms.

Despite the great potential of single nucleotide polymorphism (SNP) markers in evolutionary studies, in particular for inferring population genetic parameters, SNP analysis has almost exclusively been limited to humans and 'genomic model' organisms, due to the lack of available sequence data in non-model organisms. Here, we describe a rapid and cost effective method to isolate candidate SNPs in non-model organisms. This SNP isolation strategy consists basically in the direct sequencing of amplified fragment length polymorphism bands. In a first application of this method, 10 unique DNA fragments that contained 24 SNPs were discovered in 11.11 kb of sequenced genomic DNA of a non-model species, the brown trout (Salmo trutta).

Animals↗
PubMed2003

Recent habitat fragmentation caused by major roads leads to reduction of gene flow and loss of genetic variability in ground beetles.

Although habitat fragmentation is suspected to jeopardize the long-term survival of many species, few data are available on its impact on the genetic variability of invertebrates. We assess the genetic population structure of the flightless ground beetle Carabus violaceus L., 1758 in a Swiss forest, which is divided into several fragments by a highway and two main roads. Eight samples were collected from different forest fragments and analysed at six microsatellite loci. The largest genetic differentiation was observed between samples separated by roads and in particular by the highway. The number of roads between sites explained 44% of the variance in pairwise F(ST) estimates, whereas the age of the road and the geographical distance between locations were not significant factors. Furthermore, a comparison of allelic richness showed that the genetic variability in a small forest fragment isolated by the highway was significantly lower than in the rest of the study area. These findings strongly support the hypothesis that large roads are absolute barriers to gene flow in C. violaceus, which may lead to a loss of genetic variability in fragmented populations.

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PubMed2003

The phylogeographic importance of the Strait of Gibraltar as a gene flow barrier in terrestrial arthropods: a case study with the scorpion Buthus occitanus as model organism.

The phylogenetic relationship between Buthus occitanus populations across the Strait of Gibraltar was investigated using nuclear 18S/ITS-1 DNA sequences and mitochondrial 16S and COI DNA sequences. All analyses showed that the European samples are highly separated from North African samples, and also suggest the existence of three main groups within this species complex, i.e., an European, an Atlas (=Moroccan samples) and a Tell-Atlas group (=Tunisian samples). The European clade was subdivided into three distinct subclades. The application of a previous calibration of the molecular clock of another buthid species suggested that most of the detected mitochondrial DNA lineages including the European lineages are about three times older than the re-opening of the Gibraltar Strait, and consequently, that other and older vicariant events are responsible for the observed phylogeographic structure of this species complex. Concerning the Moroccan samples, a discordance between nuclear and mitochondrial gene markers was observed. The 18S/ITS-1 gene tree could not resolve the phylogenetic relationships among the Moroccan B. occitanus subspecies and the closely related species B. atlantis, whereas mitochondrial genes suggested the co-existence of several old phylogenetic lineages in Morocco. We hypothesized that this difference may be explained by male-biased gene flow and gene conversion at the tandemly repeated 18S/ITS-1 gene regions.

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