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Increased Fecundity (increased + fecundity)
Selected AbstractsHAVE MALE AND FEMALE GENITALIA COEVOLVED?EVOLUTION, Issue 9 2005A PHYLOGENETIC ANALYSIS OF GENITALIC MORPHOLOGY AND SEXUAL SIZE DIMORPHISM IN WEB-BUILDING SPIDERS (ARANEAE: ARANEOIDEA) Abstract Sexual size dimorphism (SSD) can strongly influence the evolution of reproductive strategies and life history. If SSD is extreme, and other characters (e.g., genitalic size) also increase with size, then functional conflicts may arise between the sexes. Spiders offer an excellent opportunity to investigate this issue because of their wide range of SSD. By using modern phylogenetic methods with 16 species of orb-weaving spiders, we provide strong evidence for the "positive genitalic divergence" model, implying that sexual genitalic dimorphism (SGD) increases as SSD increases. This pattern is supported by an evolutionary mismatch between the absolute sizes of male and female genitalia across species. Indeed, our findings reveal a dramatic reversal from male genitalia that are up to 87X larger than female genitalia in size-monomorphic species to female genitalia that are up to 2.8X larger in extremely size-dimorphic species. We infer that divergence in SGD could limit SSD both in spiders, and potentially in other taxa as well. Further, male and female body size, as well as male and female genitalia size, are decoupled evolutionarily. Finally, we show a negative scaling (hypoallometry) of male and female genitalic morphology within sexes. Evolutionary forces specific to each sex, such as larger female size (increased fecundity) or smaller male size (enhanced mate-searching ability), may be balanced by stabilizing selection on relative genitalic size. [source] Butterfly life history and temperature adaptations; dry open habitats select for increased fecundity and longevityJOURNAL OF ANIMAL ECOLOGY, Issue 1 2005BENGT KARLSSON Summary 1Evidence suggests that changes of temperature-related performance curves can trigger a selective response in life-history traits. Hence, it should be expected that insects adapted to different temperature regimes should exhibit optimal performance at the temperature to which they are adapted. 2To test this idea we investigated how fecundity and longevity are influenced by ambient temperatures in a set of satyrine butterflies adapted to live in dry open landscapes or in closed forest landscapes, respectively, by keeping egg-laying adult females at five different constant temperatures ranging between 20 and 40 °C. 3We studied four species, two of which are confined to dry and hot open habitats, namely the grayling (Hipparchia semele) and the small heath (Coenonympha pamphilus), and two of which are shade dwelling, namely the ringlet (Aphantopus hyperantus) and the speckled wood butterfly (Pararge aegeria). 4As predicted, the results showed that lifetime fecundity exhibited bell-shaped curves in relation to temperature with the open landscape group peaking at a higher temperature, 30 °C, compared with the shade-dwelling group that peaked at 25 °C. Longevity decreased with increasing temperatures among all species, but the open landscape living species survived better at higher temperatures. Moreover, although the magnitude of reproductive effort measured as lifetime egg mass did not differ between the two ecological groups, lifetime fecundity did with open landscape species laying more and smaller eggs than the shade-dwelling species. 5This difference in life-history character traits suggests either that dry and relatively warm open habitats open life-history opportunities in terms of higher fecundity and longevity that remain closed to butterflies adapted to cooler temperatures, or that life in dry open habitats actively selects for higher fecundity and survival as a result of increased offspring mortality. [source] Influence of plant quality on pine sawfly population dynamicsOIKOS, Issue 3 2000Stig Larsson The contribution of plant quality to the population dynamics of herbivorous insects has been an issue of much controversy. Many studies have documented how variable plant quality differentially influences the survival and fecundity of insect individuals. Whether or not such effects can be translated to the level of insect populations is, however, not clear. In order to test this hypothesis one needs to combine processes at both the level of the individual and the population. This is difficult with an empirical approach, but could be achieved by means of modeling given that appropriate data exist for both levels of organization. In this paper we report on a model developed to analyze whether altered Scots pine (Pinus sylvestris) quality can contribute to the build-up of populations of the European pine sawfly (Neodiprion sertifer). Experimental data on responses of sawfly larvae to variable plant quality, i.e. needle concentrations of resin acids, were used to parameterize the model. Larval survival and sawfly fecundity are reduced at high resin acid concentrations. However, high resin acid concentrations are, at the same time, beneficial because larval defense against predators is enhanced. In the model, data on individual responses were combined with literature data at the population level; a type III functional response related to cocoon predation was presumed to be the density-dependent process regulating sawfly populations. The analysis showed that the risk for an outbreak is high when needle resin acid concentration (r) or larval predation pressure (p) is low. When r or p is high there is no risk. By analyzing different scenarios it was found that small changes in r and p can result in the sawfly population moving from low to high outbreak risk. Changes of the same, or larger, magnitude in r have been observed in empirical studies. The role of tritrophic interactions was also considered. This was done by removing the positive effects of resin acids on larval performance in the model. It was found that the anti-predator defense of N.sertifer makes it prone to outbreak under wider combinations of r and p than an insect without the defense. We conclude that small changes in a density-independent factor, such as needle chemistry, can have significant effects on herbivore population dynamics because increased fecundity and survival caused by needle quality may allow the population to escape the control of density-dependent factors, such as cocoon predation. [source] Competition strategies and correlated selection on responses to polyandry in the seed beetle Callosobruchus maculatusPHYSIOLOGICAL ENTOMOLOGY, Issue 4 2008RAUL NARCISO C. GUEDES Abstract Polyandry reflected in multiple mating with different mates is regarded as favoured by natural selection in males but not necessarily in females, where conflicting effects on fitness components can occur. The present study aims to provide empirical evidence to predict which fitness components may be affected in this sexual conflict using a species that demonstrates potential between-population variation in their resolution: the cowpea weevil Callosobruchus maculatus. Two strains showing contrasting competition outcomes (scramble × contest) and contrasting life-history strategies based on trade-offs between longevity and fecundity are crossed for subsequent selection based on larval-competition strategy, expecting the production of a correlated response to multiple (polyandrous) mating. Such a response is expected because the scramble strain shows high fecundity (and lower longevity) and would benefit from multiple mating, in contrast with the contest strain, which shows high juvenile mortality. The scramble-selected lines would evolve a response of increased fecundity and reduced longevity under multiple and potentially polyandrous mating but the contest-selected lines would not respond to multiple (polyandrous) mating. Instead, both scramble- and contest-selected lines show increased fecundity and reduced longevity with multiple (polyandrous) matings, which did not affect egg weight. Indirect benefits of multiple (polyandrous) mating appear to be relevant for lines showing contest competition among juveniles. [source] Tracking the decline of the once-common butterfly: delayed oviposition, demography and population genetics in the hermit Chazara briseisANIMAL CONSERVATION, Issue 2 2010T. Kadlec Abstract Large populations, seemingly not at risk of extinction, can decline rapidly due to alteration of habitat. This appears to be the case of the butterfly Chazara briseis, which is declining in all of Central and Eastern Europe, even from apparently large areas of its steppe grassland habitats. We combined mark,recapture, allozyme electrophoresis and adult behaviour observation to study the last remaining metapopulation of this once-widespread butterfly in the Czech Republic. The total population estimate was 1300 males and 1050 females in 10 colonies within a 70 km2 landscape. Adults were long-lived, and inseminated females required several weeks before they started ovipositing. Models using realistic lengths of the preoviposition period estimated that due to background mortality, only 25,55% of the female census population lived long enough to contribute to the next generation. This demographic load was unlikely to be balanced by an increased fecundity. Allozyme electrophoresis of 22 loci revealed much higher allelic variation than in most other studies of butterflies living in small populations (mean heterozygosity: 20.7%). If expressed as per individual colony, the genetic variation did not correlate with population density, survival or longevity. This was probably due to frequent movements among colonies; during 8 weeks of adult flight, 5.1% of recaptured males and 3.6% of recaptured females moved between colonies. The high preoviposition mortality indicates that populations of this species must contain more individuals compared with populations not suffering this additional demographic load. The high allelic diversity of each single colony suggests that the population as a whole has not undergone genetic bottlenecks, but now may be facing risks of inbreeding depression due to allele frequency shifts and the possible increase of weakly deleterious alleles. In the past, high effective population sizes were maintained by frequent dispersal in dense networks of steppic grasslands. Generous habitat restoration is necessary to safeguard populations of this specialized, yet formerly common species. [source] | ||||||||||