Extension of the Castle-Wright effective factor estimator to sex linkage and haplodiploidy.
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The Castle-Wright effective factor estimator gives a minimum estimate of the number of genes underlying complex traits. Because the Castle-Wright estimator does not rely on genetic markers, it is especially useful in genetically undeveloped species. In this article I describe two extensions of this estimator. The first corrects the estimator in heterogametic (XY) species with a partially sex-linked trait. In this case the traditional estimator underestimates gene number in F2 males and overestimates it in F2 females and backcross females and males. The second extension adapts the Castle-Wright equation to haplodiploid species. (+info)
Infiltration of a Hawaiian community by introduced biological control agents.
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To examine the community-wide effects of introduced biocontrol agents on Kauai Island, Hawaii, we constructed quantitative food webs showing interactions among plants, moths, and moth parasitoids in a native forest. Eighty-three percent of parasitoids reared from native moths were biological control agents, 14% were accidental immigrants, and 3% were native species. Although parasitism by biological control agents reached 28% in some species of moth, all biocontrol agents reared had been released before 1945. This study highlights the importance of considering the potential damage caused by an introduced control agent, in addition to that caused by the target alien species. (+info)
Reproduction and recruitment in perennial colonies of the introduced wasp Vespula germanica.
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We investigated the genetic structure of perennial colonies of the yellowjacket wasp (Vespula germanica) in its introduced range in Australia and New Zealand. The nuclear genotypes of 712 gynes from 21 colonies, 147 workers from 5 colonies, and 81 males from 4 colonies were assayed at three polymorphic microsatellite loci. The mitochondrial haplotypes of all wasps also were determined for a 450-bp region of the mtDNA using double-stranded conformational polymorphism (DSCP) analysis. We found that multiple reproductives were needed to explain the genotypes of gynes, workers, and males in 7 of 21, 2 of 5, and 2 of 4 colonies, respectively, and that nestmate relatedness of these three castes equaled 0.42, 0.16, and 0.22, respectively. The mitochondrial data revealed that all individuals shared the same mtDNA haplotype in 20 of the 21 colonies. However, in one colony, gynes and workers displayed multiple mtDNA haplotypes, indicating that nonnestmate recruitment had occurred. Overall the genetic structure within the majority of perennial colonies conformed to expectations based on the biology of V. germanica and kin selection theory for polygyne colonies; multiple reproductives successfully produced offspring and were recruited into their natal nests, thereby maintaining relatively high relatedness between interacting individuals. (+info)
Using artificial evolution and selection to model insect navigation.
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BACKGROUND: An animal's behavioral strategies are often constrained by its evolutionary history and the resources available to it. Artificial evolution allows one to manipulate such constraints and explore how they influence evolved strategies. Here we compare the navigational strategies of flying insects with those of artificially evolved "animats" endowed with various motor architectures. Using evolutionary algorithms, we generated artificial neural networks that controlled a virtual animat's navigation within a 2D, simulated world. Like a flying insect, the animat possessed motors that generated thrust and torque, a compass, and visual sensors. Some animats were limited to forward motion, while others could also move sideways. Animats were selected for the precision with which they reached a target specified by a visual landmark. RESULTS: Animats given sideways motors could alter flight direction without changing body orientation and evolved strategies similar to those of flying bees or wasps performing the same task. Both animats and insects first aimed at the landmark. In the last phase, both adopted a fixed body orientation and adjusted their position to keep the landmark at a fixed retinal location. Animats unable to uncouple flight direction and body orientation evolved subtly different strategies and performed less robustly. CONCLUSIONS: This convergence between the navigational strategies of animals and animats suggests that the insect's strategies are primarily an adaptation to the demands of using visual information and compass direction to reach a position in space and that they are not significantly compromised by the insect's evolutionary history. (+info)
Possible horizontal transfer of a transposable element from host to parasitoid.
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Full-length mariner-like elements (MLEs) were identified from both a parasitoid wasp, Ascogaster reticulatus, and its moth host, Adoxophyes honmai. MLEs were detected in two related Tortricid moths, but not in another Ascogaster species. The MLEs of A. reticulatus and A. honmai were 97.6% identical in DNA sequence. This high similarity suggests a recent horizontal transfer, probably from the moth host to the wasp parasitoid, facilitated by the intimacy of the host-parasitoid relationship. (+info)
Helping effort and future fitness in cooperation animal societies.
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Little attention has been paid to a conspicuous and universal feature of animal societies: the variation between individuals in helping effort. Here, we develop a multiplayer kin-selection model that assumes that subordinates face a trade-off because current investment in help reduces their own future reproductive success. The model makes two predictions: (i) subordinates will work less hard the closer they are to inheriting breeding status; and (ii) for a given dominance rank, subordinates will work less hard in larger groups. The second prediction reflects the larger pay-off from inheriting a larger group. Both predictions were tested through a field experiment on the paper wasp Polistes dominulus. First, we measured an index of helping effort among subordinates, then we removed successive dominants to reveal the inheritance ranks of the subordinates: their positions in the queue to inherit dominance. We found that both inheritance rank and group size had significant effects on helping effort, in the manner predicted by our model. The close match between our theoretical and empirical results suggests that individuals adjust their helping effort according to their expected future reproductive success. This relationship has probably remained hidden in previous studies that have focused on variation in genetic relatedness. (+info)
A newly discovered bacterium associated with parthenogenesis and a change in host selection behavior in parasitoid wasps.
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The symbiotic bacterium Wolbachia pipientis has been considered unique in its ability to cause multiple reproductive anomalies in its arthropod hosts. Here we report that an undescribed bacterium is vertically transmitted and associated with thelytokous parthenogenetic reproduction in Encarsia, a genus of parasitoid wasps. Although Wolbachia was found in only one of seven parthenogenetic Encarsia populations examined, the "Encarsia bacterium" (EB) was found in the other six. Among seven sexually reproducing populations screened, EB was present in one, and none harbored Wolbachia. Antibiotic treatment did not induce male production in Encarsia pergandiella but changed the oviposition behavior of females. Cured females accepted one host type at the same rate as control females but parasitized significantly fewer of the other host type. Phylogenetic analysis based on the 16S rDNA gene sequence places the EB in a unique clade within the Cytophaga-Flexibacter-Bacteroid group and shows EB is unrelated to the Proteobacteria, where Wolbachia and most other insect symbionts are found. These results imply evolution of the induction of parthenogenesis in a lineage other than Wolbachia. Importantly, these results also suggest that EB may modify the behavior of its wasp carrier in a way that enhances its transmission. (+info)
Skewed paternity and sex allocation in hermaphroditic plants and animals.
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Models predict a reduced allocation to sperm when females preferentially use one of two males' sperm and the males do not know who is favoured. An analogous discounting occurs in plants when their paternity success is skewed by random, non-heritable factors such as location in the population and pollinator behaviour. We present a model that shows that skewed paternity can affect the sex allocation of hermaphrodites, that is it leads to a female-biased investment. The model highlights the close links between local mate competition and sperm competition. We use paternity data from Ficus in order to illustrate that skews in paternity success can lead to a high degree of sibling gamete competition in an apparently open breeding system. Since skews in paternity are ubiquitous in hermaphroditic plants and animals these findings should apply broadly. (+info)