1,721,044 research outputs found
Development and characterization of microsatellite markers in the Colorado potato beetle, Leptinotarsa decemlineata
No full textThe characterization of 11 Leptinotarsa decemlineata microsatellite loci
isolated using the fast isolation by AFLP of sequences containing
repeats (FIASCO) protocol is reported. Three to 15 alleles per locus
were detected in 54 beetles collected from four populations of L.
decemlineata. The mean number of alleles was 7.4 +/- 3.2 and the level
of expected heterozygosity ranged from 0.451 to 0.798. The total
exclusionary probabilities using these loci for the first and the second
parent were 0.982 and 0.999, respectively. These are the first
microsatellite loci characterized from the Colorado potato beetles that
can be used for estimating genetic diversity, population structure and
parentage analysis
EVOLUTION OF THE MITOCHONDRIAL RIBOSOMAL-RNA IN THE ORIENTAL SPECIES SUBGROUPS OF DROSOPHILA
No full textThe nucleotide sequence of two segments of the mtDNA molecule of
different species of Drosophila containing a portion of the large rRNA
(16S) and a portion of the small rRNA (23S) has been determined.
The polymerase chain reaction (PCR) technique with ''universal'' primers
has been used to amplify the segments for direct sequencing.
The species analysed belong to four different subgroups of the
melanogaster species group.
The phylogenetic relationships of the species have been reconstructed by
using the neighbour-joining algorithm and the significance of the
inferred phylogeny tested by bootstrap method
Genetic variation and bill size dimorphism in a passerine bird, the reed bunting Emberiza schoeniclus
No full textIn passerine birds morphological differentiation in bill size within
species is not commonly observed. Bill size is usually associated with a
trophic niche, and strong differences in it may reflect the process of
genetic differentiation and, possibly, speciation. We used both
mitochondrial DNA (mtDNA) and nuclear microsatellites to study genetic
variation between two subspecies of reed bunting, Emberiza schoeniclus
schoeniclus and E.s. intermedia, along their distributional boundary in
western Europe. These two subspecies are characterized by a high
dimorphism in bill size and, although breeding populations of the two
subspecies are found very close to each other in northern Italy,
apparently no interbreeding occurs. The observed morphological pattern
between the two subspecies may be maintained by geographically varying
selective forces or, alteratively, may be the result of a long
geographical separation followed by a secondary contact. MtDNA sequences
of cytochrome b and ND5 (515 bp) showed little variation and did not
discriminate between the two subspecies, indicating a divergence time of
less than 500 000 years. The analysis of four microsatellite loci
suggested a clear, although weak, degree of genetic differentiation in
the large- and small-billed populations, as indicated by F-ST and R-ST
values and genetic distances. The correlation between bill size and
genetic distance between populations remained significant after
accounting for the geographical distances between sampling localities.
Altogether, these results indicate a very recent genetic differentiation
between the two bill morphs and suggest that a strong selection for
large bills in the southern part of the breeding range is probably
involved in maintaining the geographical differentiation of this
species
Phylogeny and evolution of parthenogenesis in Finnish bagworm moth species (Lepidoptera : Psychidae : Naryciinae) based on mtDNA-markers
No full textWe investigated species diversity and evolution of parthenogenesis among
bagworm moth species of Dahlica and Siederia using mitochondrial DNA
sequencing. Parthenogenesis is rare among Lepidoptera other than
Psychidae. Genera Dahlica and Siederia form a confusing group with
controversial species boundaries and widely overlapping morphological
features that make species determination difficult. We evaluated the
reliability of species determination based on wing scale morphology by
comparing it with a phylogenetic tree obtained using mtDNA. Species
determination based on morphological characteristics did not correspond
to species determination based on mtDNA markers. On the basis of the
molecular phylogeny, the status of these two genera is questionable. Our
results indicate that parthenogenetic D. fennicella, D. triquetrella and
D. lichenella evolved independently from different sexual ancestors
suggesting that asexual reproduction is favoured in this group
Evolution of reproductive strategies and male sexual ornaments in poeciliid fishes as inferred by mitochondrial 16S rRNA gene phylogeny.
No full textPoeciliid fishes have been widely used as a model system in the study of
sexual selection mechanisms. In several species belonging to the genera
Xiphophorus and Poecilia males show conspicuous ornaments and use
courtship display to obtain female cooperation during mating. Conversely
most of the remaining poeciliids are drab and achieve copulation mainly
through gonopodial thrusting, a fertilization strategy that bypasses the
female's consent. We sequenced a portion of the large (16S)
mitochondrial ribosomal RNA gene to estimate the phylogenetic
relationships among the Eve tribes of the subfamily Poeciliinae (ROSEN &
BAYLEY 1963) and we used the molecular phylogeny to reconstruct the
origin of male ornaments and the evolutionary history of the
reproductive strategies in this family. Gambusiini were found to be the
basal tribe in the subfamily Poeciliinae. In our phylogeny, Xiphophorus
and Poecilia were not closely related thus suggesting that the tribe
Poeciliini is not a monophyletic group. Gonopodial thrusting was
probably the primitive mating strategy of the poeciliids. Sexual
ornaments and elaborate courtship behaviour apparently evolved more
recently in the genus Xiphophorus and independently in the genus
Poecilia
Genetic diversity in populations of asexual and sexual bag worm moths (Lepidoptera: Psychidae).
Full text linkDespite the two-fold cost of sex, most of the higher animals reproduce
sexually. The advantage of sex has been suggested to be its ability,
through recombination, to generate greater genetic diversity than
asexuality, thus enhancing adaptation in a changing environment. We
studied the genetic diversity and the population structure of three
closely related species of bag worm moths: two strictly sexual (Dahlica
charlottae and Siederia rupicolella) and one strictly asexual (D.
fennicella). These species compete for the same resources and share the
same parasitoids. Allelic richness was comparable between the sexual
species but it was higher than in the asexual species. All species
showed high heterozygote deficiency and a large variation was observed
among FIS values across loci and populations. Large genetic
differentiation was observed between populations confirming the poor
dispersal ability of these species. The asexual species showed lower
genotype diversity than the sexual species. Nevertheless, genotype
diversity was high in all asexual populations. The three different
species show a similar population structure characterised by high
genetic differentiation among populations and low dispersal. Most of the
populations showed high heterozygote deficiency likely due to the
presence of null alleles at most of the loci and/or to the Wahlund
effect. Although the parthenogenetic D. fennicella shows reduced genetic
diversity compared to the sexual species, it still shows surprisingly
high genotype diversity. While we can not totally rule out the presence
of cryptic sex, would explain this high genotype diversity, we never
observed sex in the parthenogenetic D. fennicella, nor was there any
other evidence of this. Alternatively, a non-clonal parthenogenetic
reproduction, such as automictic thelytoky, could explain the high
genotypic diversity observed in D. fennicella
Parasites and sexual reproduction in psychid moths
No full textPersistence of sexual reproduction among coexisting asexual competitors
has been a major paradox in evolutionary biology. The number of
empirical studies is still very limited, as few systems with coexisting
sexual and strictly asexual lineages have been found. We studied the
ecological mechanisms behind the simultaneous coexistence of a sexually
and an asexually reproducing closely related species of psychid moth in
Central Finland between 1999 and 2001. The two species compete for the
same resources and are often infected by the same hymenopteran
parasitoids. They are extremely morphologically and behaviorally similar
and can be separated only by their reproductive strategy (sexual vs.
asexual) or by genetic markers. We compared the life-history traits of
these species in two locations where they coexist to test predictions of
the cost-of-sex hypothesis. We did not find any difference in female
size, number of larvae, or offspring survival between the sexuals and
asexuals, indicating that sexuals are subject to cost of sex. We also
used genetic markers to check and exclude the possibility of Wolbachia
bacteria infection inducing parthenogenesis. None of the samples was
infected by Wolbachia and, thus, it is unlikely that these bacteria
could affect our results. We sampled 38 locations to study the
prevalence of parasitoids and the moths' reproductive strategy. We found
a strong positive correlation between prevalence of sexual reproduction
and prevalence of parasitoids. In locations where parasitoids are rare
asexuals exist in high densities, whereas in locations with a high
parasitoid load the sexual species was dominant. Spatial distribution
alone does not explain the results. We suggest that the parasite
hypothesis for sex may offer an explanation for the persistence of
sexual moths in this system
A large panel of novel microsatellite markers for the bank vole (Myodes glareolus)
No full textWe describe a set of 66 highly polymorphic microsatellite loci isolated
from the bank vole, Myodes (Clethrionomys) glareolus. These
microsatellites were characterized for a long-term study on periodically
fluctuating density of the bank vole population in Central Finland. We
detected six to 38 alleles per locus in the population sampled at two
different density phases, and the levels of observed and expected
heterozygosities varied between 0.17 and 1.00, and between 0.72 and
0.95, respectively. This microsatellite panel serves as an informative
tool for population and molecular genetic studies
Influence of male mating history on female reproductive success among monandrous Naryciinae (Lepidoptera: Psychidae)
No full text1. Multiple male copulations can have detrimental effects on female fitness
due to sperm limitation. 2. Monandrous Naryciinae females are immobile while the males are
short-lived and do not feed. Multiple male mating is therefore expected
to lead to sperm limitation in females. Sperm limitation and male
limitation are hypothesised as causes of the repeated evolution of
parthenogenetic reproduction in the Psychidae.
3. In this study, the effects of multiple male mating on female
reproduction are investigated in several species of Naryciinae by
allowing males multiple copulations. The results for two species,
Siederia listerella and Dahlica lichenella, are compared. The sex ratios
of 53 natural populations are examined for indications of male
limitation.
4. Previous copulations by the male increased the female's risk of
remaining unfertilised. However, contrary to expectations, those
unfertilised females were capable of successful re-mating.
5. In S. listerella, the number of previous copulations of males
negatively influenced female fitness. Females produced 30% fewer
offspring if they mated with a previously mated male. In D. lichenella,
the older the male and the lower its number of total lifetime
copulations, the higher the female's reproductive success.
6. Only a fraction of the investigated populations had a female-skewed
sex ratio, but differences in development time between males and females
could lead to reproductive asynchrony.
7. In conclusion, male mating history did not lead to strong sperm
limitation in Naryciinae as had been suggested by their life history
Cold tolerance during larval development: effects on the thermal distribution limits of Leptinotarsa decemlineata
No full textInsects' cold tolerance during their development is a surprisingly
understudied subject in ecology, despite the fact that subzero
temperatures during the growing season are common at high altitudes and
latitudes. Subzero temperatures can have detrimental effects on
organisms, restricting a species' range. This study addresses the
question whether night frosts during the growing season have an instant
or delayed negative impact on larval mortality of the Colorado potato
beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae). We
also tested whether populations from the centre (Poland) and margins
(Russia) of the distribution range of L. decemlineata differ in their
responses to subzero exposure and a low rearing temperature. Larvae of
three ages were subjected to a subzero temperature (-4 degrees C for 3 h
simulating night frost) twice, after which they were reared on a
fluctuating temperature regime of 10-15 degrees C. These rearing
conditions imitated cool summer temperatures beyond the beetles' current
range, such as in Finland. Individuals of both populations were highly
cold tolerant, as only 3.1% of larvae died immediately following the
subzero treatment. Nonetheless, the low rearing temperature was harmful
to beetles of both populations. It caused high larval (ca. 90%) and
overwintering (ca. 80%) mortality. As beetle performance was affected
solely by rearing temperature, low temperatures during the growing
season rather than night frosts apparently retard the beetle's northern
expansion
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