Host-parasite relatedness in wood ducks: patterns of kinship and parasite success

We investigated the role of kinship in intraspecific nest parasitismof wood ducks (Aix sponsa). Among waterfowl, female philopatrycreates the potential for female relatives to nest in proximity.Costs of intraspecific nest parasitism to host females may bereduced if parasites lay eggs with kin. However, previous observationsof marked wood ducks indicated that females avoided parasitizingclutch mates or the female that incubated them. To further examinethe role of kinship, we determined the genotypes of 27 host-parasitepairs at five microsatellite loci. Average relatedness betweenhosts and all females laying parasitic eggs was only 0.04 ±0.03. Parasites appeared to choose hosts randomly with respectto kinship from among females with nests in the neighborhoodand those within the entire study area. However, host relatednessto the parasite with the greatest number of young leaving thenest was 0.11 ± 0.03, which was greater than expectedif eggs were accepted randomly from neighboring females or fromfemales present on the entire study area (p = .03 and p = .02,respectively). These patterns may reflect parasitism of randomlyselected nests followed by differential acceptance by hosts,differential hatching success of related parasites (e.g., dueto greater laying synchrony), or a mixture of parasitic strategies,one with a focus on related hosts and the other on unrelatedhosts. Genetic data revealed that social relationships did notalways reflect true relatedness and that success of primaryparasites was associated with kinship to hosts.     

Alternative mechanisms of nonindependent mate choice

Aspects of the environment, including the social environment, can contribute to intrapopulation variation in mating preferences. One example of the effect of social environment on mate preferences is mate choice copying; however, other types of socially influenced (nonindependent) choice might exist. We develop a list of such alternatives based on possible physiological or psychological mechanisms, evaluate the evidence distinguishing one from another and clarify some controversial aspects of mate choice copying. This framework reveals many ways in which one female's mate choice can influence that of another, and suggests a broader array of hypotheses about the selective forces acting on such mechanisms. Because nonindependent choice can occur in a variety of ways, it could be more important for understanding patterns of mate choice than current theory suggests. Copyright 2000 The Association for the Study of Animal Behaviour.     

Phylogenetic relationships,evolution of broodcare behavior,and geographic speciation in the wrasse tribe Labrini

The family Labridae is a large assemblage of marine fish composed of about 580 species in 82 genera distributed in tropical and temperate marine waters around the world. Several subgroups, currently classified as tribes, have been identified in this large family, yet only a few phylogenetic analyses have been performed on labrid clades. We confirm monophyly of the labrid tribe Labrini and propose a phylogeny of the 23 species of the genera Acantholabrus, Centrolabras, Ctenolabrus, Labrus, Lappanella, Symphodus, Tautoga, and Tautogolabrus occurring in the eastern and western Atlantic and the Mediterranean. We analyzed a 577-bp segment of the mitochondrial 16S rDNA and a 506-bp segment of the mitochondrial control region in 22 species, for a total of up to 1069 bp per species. We used both parsimony and likelihood approaches under a variety of assumptions and models to generate phylogenetic hypotheses. The main features of the molecular phylogeny for the Labrini turned out to be the same for the two algorithms applied. The tree structure is similar to a previous, unpublished morphological phylogeny for a subset of labrine species. Estimated divergence times of the Labrini based on fossils and a molecular clock range from about 15 mya for the deepest splits to less than 1 mya for younger clades. Biogeographic patterns of the Symphodus species group and the genus Labrus are dominated by speciation events driven by the closing and opening of the Mediterranean Sea and periodic glaciation events during the past 1 million years. The Labrini are the only clade in the entire Labridae that exhibit nest-building and broodcare behavior. We use the phylogeny to show that similar broodcare behavior has evolved twice in the labrine fish and discuss scenarios for the evolution of broodcare from the diandric protogynous hermaphroditism found in ancestral labrines and many other wrasses.     

Individual variation in parental care reaction norms: integration of personality and plasticity

Personality (consistent differences between individuals in behavior) and plasticity (changes within individuals in behavior) are often viewed as separate and opposing phenomena. We tested this idea by analyzing parental care reaction norms in a bird that exhibits biparental care. Personality in provisioning behavior existed ([Formula: see text]) and persisted despite being reduced after accounting for individual differences in environment. Plasticity was also evident and differed between the sexes. Male visit rate was associated with changes in brood size and time of day, but female visit rate was associated with changes in nestling age and date. In both sexes changes in visit rate were positively correlated with changes in their partner's visit rate. Both sexes also exhibited multidimensional reaction norms; interaction terms revealed that within-individual visit rates increased more steeply with brood size when nestlings were older, and the effect of the partner's visit rate was sensitive to variation in date, precipitation, and the focal bird's age. Individuals also varied in how they responded (reaction norm slope) to changes in nestling age and partner visits. Moreover, parental personality was interdependent with individual plasticity in several ways. Individuals of both sexes with a high visit rate also responded more positively to changes in nestling age, and males also showed this pattern with changes in partner visit rate. Explicit use of the behavioral reaction norm integrated personality and plasticity, revealed that these are not opposing concepts, and stimulated new hypotheses about sexual conflict over care and provisioning as a life-history trait.     

Heterozygosity predicts clutch and egg size but not plasticity in a house sparrow population with no evidence of inbreeding

We investigated the link between heterozygosity and the reaction norm attributes of reproductive performance in female house sparrows (Passer domesticus). We collected data on clutch size, egg size, hatching success and nestling survival in 2816 nesting attempts made by 791 marked individuals over a 16-year period. Pedigree analysis revealed no evidence of inbreeding. Neither parent-offspring regression nor an animal model revealed significant heritability in clutch or egg size. We selected 42 females that laid at least seven clutches at our study site and used a survey of 21 autosomal microsatellite loci to estimate heterozygosity for each female. We controlled for phenotypic plasticity and found that both clutch and egg size showed significant positive correlations with heterozygosity. We found no evidence that heterozygosity influenced the slope of individual reaction norms. Further analysis suggested that clutch size was affected by heterozygosity across the genome, but egg size had more complex relationships, with evidence favouring the influence of multiple loci. Given the apparent lack of inbreeding and large population size, our results suggest associative overdominance as the likely mechanism for the impact of heterozygosity, but also created a puzzle about the process producing associations between neutral markers and the genes affecting clutch size or egg size. One possible explanation is a long-term residual effect of the historical bottleneck that occurred when house sparrows were introduced into North America. The existence of heterozygosity-fitness correlations in a population with considerable phenotypic plasticity and little inbreeding implies that the effects of heterozygosity may be more significant than previously thought.     

Feeding mechanics and bite force modelling of the skull of Dunkleosteus terrelli, an ancient apex predator

Placoderms are a diverse group of armoured fishes that dominated the aquatic ecosystems of the Devonian Period, 415-360 million years ago. The bladed jaws of predators such as Dunkleosteus suggest that these animals were the first vertebrates to use rapid mouth opening and a powerful bite to capture and fragment evasive prey items prior to ingestion. Here, we develop a biomechanical model of force and motion during feeding in Dunkleosteus terrelli that reveals a highly kinetic skull driven by a unique four-bar linkage mechanism. The linkage system has a high-speed transmission for jaw opening, producing a rapid expansion phase similar to modern fishes that use suction during prey capture. Jaw closing muscles power an extraordinarily strong bite, with an estimated maximal bite force of over 4400 N at the jaw tip and more than 5300 N at the rear dental plates, for a large individual (6 m in total length). This bite force capability is the greatest of all living or fossil fishes and is among the most powerful bites in animals.     

Seasonal and Sex-specific mRNA Levels of Key Endocrine Genes in Adult Yellow Perch (Perca flavescens) from Lake Erie

To better understand the endocrine mechanisms that underlie sexually dimorphic growth (females grow faster) in yellow perch (Perca flavescens), real-time quantitative polymerase chain reaction (qPCR) was used to measure pituitary, liver, and ovary mRNA levels of genes related to growth and reproduction-sex in this species. Adult perch were collected from Lake Erie and body mass, age, gonadosomatic index (I (G)), hepatosomatic index (I (H)), and gene expression for growth hormone (GH), prolactin, somatolactin, insulin-like growth factor Ib (IGF-Ib), estrogen receptor alpha (esr1), estrogen receptor betaa (esr2a), and aromatase (cyp19a1a) were measured. Females had higher body mass, I (H), and liver esr1 mRNA level than males, while males had higher liver IGF-Ib, liver esr2a, and liver cyp19a1a mRNA levels. In both sexes, season had a significant effect on GH and liver IGF-Ib mRNAs with higher levels occurring in spring, which also corresponded with higher liver cyp19a1a mRNA levels. For females, I (G), liver esr1, and ovary cyp19a1a mRNA levels were higher in autumn than the spring, and ovary cyp19a1a mRNA levels showed a significant negative correlation with pituitary GH and liver IGF-Ib mRNA levels. The most significant (p 相似文献   

Parentage and the evolution of parental behavior

Parentage is the proportion of juveniles in a brood that areoffspring of potential care givers. We analyzed how reductionsin parentage affect the evolution of parental behavior usinga static optimization model. The main benefit of parental effortwas an increase in the survival of offspring, and the main costswere reduced opportunities to seek additional matings or toparasitize neighbors and or reduced survival. Both the costsand benefits included terms for relatedness to young. The effectof parentage depended on (1) whether parents responded in ecologicaltime (facultative response) or in evolutionary time (nonfacultativeresponse), (2) whether the cues enabling assessment of parentagepermitted discrimination among offspring, and (3) whether parentagewas the same among different groups of juveniles (unrestricted)or varied between them (restricted). When parents did not knowtheir own parentage and mean parentage was the same for allmatings, reduced parentage affected the costs and benefits equally,so, as in several previous models, there was no effect on theoptimal level of parental effort. Parentage did affect optimalparental effort when mean parentage to the present brood differedfrom that to young from alternative or future matings. Loweredparentage reduced optimal parental effort when the cost of parentingwas missed opportunities for extrapair copulations or broodparasitism or when parentage was consistently higher in alternativeor future matings. Nonlinear changes in parentage with age gavecomplex trajectories of parental care, with individuals of differentages having similar parentage but exhibiting different levelsof parental effort. Correlations between parentage and othervariables in the model (such as opportunities for additionalmatings) sometimes masked, but never eliminated, the effectsof parentage. When parents could discriminate their own youngin a brood, overall parental effort was reduced, but nepotismwas increased. When parents could not discriminate their ownoffspring but had general cues about average parentage to thebrood, effects varied depending on the costs and benefits ofparental behavior. When parental behavior was costly to caregivers, parentage had more effect than when parenting was notcostly. Likewise, parentage had less effect when care greatlyincreased offspring survival than when care was less necessary.Our analyses reconcile conflicting results from previous modelsand suggest a general framework for analyzing parental behaviorwithin populations and among higher taxonomic groups.     

Kinematics, dynamics, and energetics of rowing and flapping propulsion in fishes

The shape and motion of the pectoral fins vary considerablyamong fishes that swim in the labriform mode. Pectoral fin motionin fishes is highly variable, but one conspicuous axis of thisvariation is the rowing-flapping axis. At one extreme of thisaxis, paddle-shaped fins row back and forth in a plane thatis parallel to fish motion, while at the other extreme, wing-shapedfins flap up and down in a plane that is perpendicular to fishmotion. We have used two fish, the threespine stickleback (Gasterosteusaculeatus) and the bird wrasse (Gomphosus varius), that fallnear the extremes of the rowing-flapping axis to study the dynamic,energetic, and ecological and evolutionary consequences of thiskinematic variation. Our work confirms some traditionally heldassumptions about rowing and flapping dynamics and energeticsbut reject others. A computer simulation experiment of virtualrowing and flapping appendages makes several predictions aboutdifferences in maneuvering performance and swimming energeticsbetween rowing and flapping, which, in turn, make predictionsabout the behavior and ecological distribution of fishes thatvary along the rowing-flapping axis. Both laboratory and fieldstudies of labrid swimming ability and distribution supportthese predictions.