1,354,174 research outputs found
Maternal predator-exposure affects offspring size at birth but not telomere length in a live-bearing fish
No full textThe perception of predation risk could affect prey phenotype both within and between generations (via parental effects). The response to predation risk could involve modifications in physiology, morphology, and behavior and can ultimately affect long-term fitness. Among the possible modifications mediated by the exposure to predation risk, telomere length could be a proxy for investigating the response to predation risk both within and between generations, as telomeres can be significantly affected by environmental stress. Maternal exposure to the perception of predation risk can affect a variety of offspring traits but the effect on offspring telomere length has never been experimentally tested. Using a live-bearing fish, the guppy (Poecilia reticulata), we tested if the perceived risk of predation could affect the telomere length of adult females directly and that of their offspring with a balanced experimental setup that allowed us to control for both maternal and paternal contribution. We exposed female guppies to the perception of predation risk during gestation using a combination of both visual and chemical cues and we then measured female telomere length after the exposure period. Maternal effects mediated by the exposure to predation risk were measured on offspring telomere length and body size at birth. Contrary to our predictions, we did not find a significant effect of predation-exposure neither on female nor on offspring telomere length, but females exposed to predation risk produced smaller offspring at birth. We discuss the possible explanations for our findings and advocate for further research on telomere dynamics in ectotherms
Sperm production is negatively associated with muscle and sperm telomere length in a species subjected to strong sperm competition
No full textLife-history theory suggests that ageing is one of the costs of reproduction. Accordingly, a higher reproductive allocation is expected to increase the deterioration of both the somatic and the germinal lines through enhanced telomere attrition. In most species, males' reproductive allocation mainly regards traits that increase mating and fertilization success, that is sexually selected traits. In this study, we tested the hypothesis that a higher investment in sexually selected traits is associated with a reduced relative telomere length (RTL) in the guppy (Poecilia reticulata), an ectotherm species characterized by strong pre- and postcopulatory sexual selection. We first measured telomere length in both the soma and the sperm over guppies' lifespan to see whether there was any variation in telomere length associated with age. Second, we investigated whether a greater investment in pre- and postcopulatory sexually selected traits is linked to shorter telomere length in both the somatic and the sperm germinal lines, and in young and old males. We found that telomeres lengthened with age in the somatic tissue, but there was no age-dependent variation in telomere length in the sperm cells. Telomere length in guppies was significantly and negatively correlated with sperm production in both tissues and life stages considered in this study. Our findings indicate that telomere length in male guppies is strongly associated with their reproductive investment (sperm production), suggesting that a trade-off between reproduction and maintenance is occurring at each stage of males' life in this species
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
Evaluation of criteria for species delimitation of bagworm moths (Lepidoptera: Psychidae)
No full textAccurate identification of species is fundamental for biological research and necessary for species conservation. DNA barcoding is particularly useful when identification using morphological characteristics is laborious and/or unreliable. However, barcodes for species are dependent on the availability of reference sequences from correctly identified specimens. The traditional use of morphology to delimit the species boundaries of Finnish bagworm moths (Lepidoptera: Psychidae: Naryciinae: Dahliciini) is controversial because there is overlap in their morphological characteristics. In addition, there are no suitable molecular markers. We verified the delimitation of seven out of eight previously described taxa, by using the currently standardized COI barcode and phylogenetic inference based on fragments of mitochondrial (COI) and nuclear genes (MDH). Moreover, we compared the results of molecular methods with the outcome of geometric morphometrics. Based on molecular identification, our findings indicate that there are five sexual species (Dahlica and Siederia spp.) and two parthenogenetic species (D. fennicella and D. triquetrella) in Finland. We suggest that molecular methods, together with geometric morphometrics of male genitalia are an effective way of delimiting species of bagworm moths
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
The role of niche breadth, resource availability and range position on the life history of butterflies
No full textWe analysed the relationship between three life history characteristics
(mobility, length of flight period and body size) and niche breadth
(larval host plant specificity and adult habitat breadth), resource
availability (distribution and abundance of host plants) and range
position (distance between the northernmost distribution record and
southernmost point of Finland) of the butterfly fauna of Finland. The
data is based on literature and questionnaires. Often in across species
studies phylogeny may create spurious relationships between life-history
and ecological variables. We took the phylogenetic relatedness of
butterfly species into account by analysing the data with
phylogenetically independent contrasts (CAIC method). Butterfly mobility
was positively related to the niche breadth, resource availability and
range position. The length of the flight period was negatively related
to the range position, indicating that the species at the northern edge
of their distribution range have shorter flight period than species
which are further way from the range edge. After controlling for the
phylogenetic relatedness we found no significant correlations between
body size and niche breadth, resource availability or range position. We
suggest that the relationship between the length of the flight period
and range position may arise as a consequence of lower hatching
asynchrony in edge species as a result of lower environmental variance
in larval growth conditions. Our results on the mobility suggest that
there is selection pressure towards lower migration rate in species that
have restricted niche breadth, low resource availability and in species
that are on the northern edge of their geographical distribution range.
In such species, selection against mobile individuals is likely to
result from the decreased probability of finding another habitat patch
suitable for egg laying
The voyage of an invasive species across continents: genetic diversity of North American and European Colorado potato beetle populations
No full textThe paradox of successful invading species is that they are likely to be
genetically depauperate compared to their source population. This study
on Colorado potato beetles is one of the few studies of the genetic
consequences of continent-scale invasion in an insect pest.
Understanding gene flow, population structure and the potential for
rapid evolution in native and invasive populations offers insights both
into the dynamics of small populations that become successful invaders
and for their management as pests. We used this approach to investigate
the invasion of the Colorado potato beetle (Leptinotarsa decemlineata)
from North America to Europe. The beetles invaded Europe at the
beginning of the 20th century and expanded almost throughout the
continent in about 30 years. From the analysis of mitochondrial DNA
(mtDNA) and amplified fragment length polymorphism (AFLP) markers, we
found the highest genetic diversity in beetle populations from the
central United States. The European populations clearly contained only a
fraction of the genetic variability observed in North American
populations. European populations show a significant reduction at
nuclear markers (AFLPs) and are fixed for one mitochondrial haplotype,
suggesting a single successful founder event. Despite the high vagility
of the species and the reduction of genetic diversity in Europe, we
found a similar, high level of population structure and low gene flow
among populations on both continents. Founder events during range
expansion, agricultural management with crop rotation, and selection due
to insecticide applications are most likely the causes partitioning
genetic diversity in this species
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
Quantitative genetic approach for assessing invasiveness: geographic and genetic variation in life-history traits
No full textPredicting the spread of invasive species is a challenge for modern
ecology. Although many invasive species undergo genetic bottlenecks
during introduction to new areas resulting in a loss of genetic
diversity, successful invaders manage to flourish in novel environments
either because of pre-adaptations or because important traits contain
adaptive variation enabling rapid adaptation to changing conditions. To
predict and understand invasion success, it is crucial to analyse these
features. We assessed the potential of a well-known invader, the
Colorado potato beetle (Leptinotarsa decemlineata), to expand north of
its current range in Europe. A short growing season and harsh
overwintering conditions are apparent limiting factors for this species'
range. By rearing full-sib families from four geographically distinct
populations (Russia, Estonia, Poland, Italy) at two fluctuating
temperature regimes, we investigated (a) possible differences in
survival, development time, and body size among populations and (b) the
amount of adaptive variation within populations in these traits. All
populations were able to complete their development in cooler conditions
than in their current range. A significant genotype-environment
interaction for development time and body size suggests the presence of
adaptive genetic variation, indicating potential to adapt to cooler
conditions. The northernmost population had the highest survival rates
and fastest development times on both temperature regimes, suggesting
pre-adaptation to cooler temperatures. Other populations had minor
differences in development times. Interestingly, this species lacks the
classical trade-off between body size and development time which could
have contributed to its invasion potential. This study demonstrates the
importance of considering both ecological and evolutionary aspects when
assessing invasion risk
Low parasitism rates in parthenogenetic bagworm moths do not support the parasitoid hypothesis for sex
No full textThe parasite hypothesis for sex is one of the many theories that have been suggested to solve the mystery of the widespread occurrence of sex despite its high short-term costs. It suggests that sexual lineages have an evolutionary advantage over parthenogens because they can frequently generate new genotypes that are temporarily less prone to coevolving parasites. In this study, we looked for further supporting evidence for the parasite hypothesis of sex in an attempt to understand the coexistence of sexual and parthenogenetic bagworm moths (Naryciinae). The bagworm moths and their parasitoids form one of the few natural host-parasite systems where sexual and parthenogenetic hosts are apparently not separated by ecological or geographical barriers. Furthermore, in support of the parasite hypothesis for sex, parthenogenetic presence is negatively correlated with parasitism rate. We specifically tested, by identifying the reproductive mode of the parasitized individuals, whether parasitoids preferentially attack the parthenogens in sites with both sexual and parthenogenetic forms, as predicted by the parasite hypothesis. We collected hosts from sites with different frequencies of parthenogenetic and sexual moths. A DNA barcoding approach was used to determine the reproductive mode of the parasitized hosts. Furthermore, we investigated whether differences in host and parasitoid phenology could provide an alternative explanation for the variation in parasitism rates between parthenogens and sexuals. Our results contradict the prediction of the parasite hypothesis because parthenogenetic bagworm moths were less parasitized than sexuals in sympatric sites. Our findings can be explained by differences in phenology between the parthenogenetic and sexual moths rather than genetic incompatibility between parthenogenetic hosts and parasitoids. The stable coexistence of sexual and parthenogenetic Naryciinae despite the many apparent costs of sex in this system remains a mystery. Our work adds to the list of studies were the assumptions of the parasite hypothesis for sex are not all met. © 2012 European Society For Evolutionary Biology
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