Characterization of microsatellite multiplexes for population genetic studies of bluehead wrasse (Thalassoma bifasciatum,Pisces: Labridae)

Bluehead wrasse (Thalassoma bifasciatum) are common coral reef fish found throughout the Caribbean. Larval duration in the plankton is relatively long for this species, which raises the possibility of long‐distance transport by ocean currents. Several nongenetic studies suggest, however, that most recruits were spawned locally. Determination of the relative importance of local recruitment vs. immigration for recruitment is needed for the effective management of populations and establishment of marine reserves. We characterized seven new polymorphic microsatellite loci for bluehead wrasse and optimized them into PCR multiplexes with three previously published loci to determine the level of dispersal between populations.     

Phenotypic plasticity of life-history traits in clonal and sexual fish (Poeciliopsis) at high and low densities

Models of resource allocation strategies predict an array of life-history responses of individuals living in resource-stressed versus non-stressed environments. I tested a number of these predictions using three fish strains (a sexual and two clonal strains) in high and low density treatments. To examine the plasticity of life-history traits in females raised in these two environments, I measured survival, growth, egg production, egg size, and proportion mature at 10 weeks of age. Survival was not affected by density treatment. However, both growth and overall egg production were lower in females from the high density treatments, and reproductive maturity was significantly delayed at the high density for all strains. Egg production per unit size was not affected by density in any strain, signifying that differences in the numbers of eggs produced was merely a reflection of the differences in size of fish in the two density treatments. Egg size was also unaffected by density in all strains. These results are related to models of resource allocation in stressful environments. There was a consistent pattern of increased reproductive investment in the sexual strain relative to the two clonal strains. The sexual strain matured earlier, produced more eggs per unit body weight, and had larger eggs than either clone at both densities. These results are interpreted by considering the predicted adaptive responses of these three strains to the long-term environmental differences in their natural habitats.     

Phenotypic plasticity in growth and fecundity induced by strong population fluctuations affects reproductive traits of female fish

Fish are known for their high phenotypic plasticity in life‐history traits in relation to environmental variability, and this is particularly pronounced among salmonids in the Northern Hemisphere. Resource limitation leads to trade‐offs in phenotypic plasticity between life‐history traits related to the reproduction, growth, and survival of individual fish, which have consequences for the age and size distributions of populations, as well as their dynamics and productivity. We studied the effect of plasticity in growth and fecundity of vendace females on their reproductive traits using a series of long‐term incubation experiments. The wild parental fish originated from four separate populations with markedly different densities, and hence naturally induced differences in their growth and fecundity. The energy allocation to somatic tissues and eggs prior to spawning served as a proxy for total resource availability to individual females, and its effects on offspring survival and growth were analyzed. Vendace females allocated a rather constant proportion of available energy to eggs (per body mass) despite different growth patterns depending on the total resources in the different lakes; investment into eggs thus dictated the share remaining for growth. The energy allocation to eggs per mass was higher in young than in old spawners and the egg size and the relative fecundity differed between them: Young females produced more and smaller eggs and larvae than old spawners. In contrast to earlier observations of salmonids, a shortage of maternal food resources did not increase offspring size and survival. Vendace females in sparse populations with ample resources and high growth produced larger eggs and larvae. Vendace accommodate strong population fluctuations by their high plasticity in growth and fecundity, which affect their offspring size and consequently their recruitment and productivity, and account for their persistence and resilience in the face of high fishing mortality.     

Comparisons of life-history traits between clonal and sexual fish (Poeciliopsis:Poeciliidae) raised in monoculture and mixed treatments

Summary Clonal and sexual co-existence is common in a number of vertebrate taxa, even though the cost of sex makes such co-existence theoretically unlikely. The frozen niche-variation (FNV) model explains this co-existence on the basis of differences in overall niche breadth and competition between clones and sexuals. In the present study I examined two predictions of the FNV model. First, I examined the prediction that genetically variable populations have higher relative fitness when compared with monoclonal populations by comparing the performances of clonal and outcrossed sexual strains ofPoeciliopsis in monocultures at two densities. The prediction of increased overall productivity for the sexuals was verified, with net reproductive rates for the sexuals being between two and four times as high as the clones. Second, I tested the prediction that derived clones will successfully compete with their sexual progenitor(s) in the narrow range to which the clones are adapted, while the sexuals should co-exist because of their ability to use a wider range of resources than any single clone. I examined this prediction by comparing performance variables (e.g. growth, fecundity and survival) of each strain in pure culture with their partitioned performance from the mixed treatments. Clonal performance increased in mixtures compared to monocultures, as expected. However, the expectation that the sexual's performance would be less affected by mixtures than the clones' performance, was not met. The sexuals had reduced growth and fecundity on a par with the increase in both variables in the clones. Therefore, support for the FNV model was mixed. Although the performance in monocultures suggests that the sexuals have a wider niche breadth than the clones, performances in mixtures do not indicate such a relationship. Switching of behaviours or resource-use patterns between mixed and pure cultures may have caused the equivocal results.     

Spatio-temporal patterns of recruitment of labroid fishes (Pisces: Labridae and Scaridae) to damselfish territories

Recent studies have shown that recruitment variability is an important process structuring reef fish assemblages. The aim of this study is to describe the spatio-temporal patterns of recruitment of three abundant labroid taxa (Coris schroederi, Halichoeres melanurus and Scarus spp.), using damselfish territories as replicate units of habitat. Temporal recruitment patterns of each taxa were consistent among three sites along 2 km of reef tract, with small differences among sites probably the result of hydrological or random factors operating at that scale. Recruitment of only one species (C. schroederi) showed consistent differences in the magnitude of recruitment among sites, which was probably due to an overriding effect of habitat selection for the location of the territories on the reef profile at one site. Two taxa, C. schroederi and Scarus spp., recruited in low to moderate rates over many weeks with moderate recruitment peaks detected in one year only. This pattern may be characteristic of many labroid species that have protracted periods of production of larvae. In contrast, H. melanurus recruited in a single short pulse of high magnitude each summer, which suggests that production of larvae by this species may occur over a more restricted period of time. No strong pattern of lunar entrainment of recruitment was detected for any taxa, which may be due to a lack of lunar periodicity in production of larvae. Further studies are now required to identify the processes that are important in determining patterns of labroid recruitment. This revised version was published online in August 2006 with corrections to the Cover Date.     

Coexistence of Tetranychus urticae (Acarina: Tetranychidae) with different capacities for diapause: comparative life-history traits

Summary Individuals of the two-spotted spider mite, Tetranychus urticae Koch (Acarina: Tetranychidae), with and without a capacity for diapause, coexist in central Japan. Diapause appears to be adaptive because females in diapause suffered less mortality than non-diapausing individuals when frozen at –24°C for more than 4 h. However non-diapausing females showed good survival up to 4 h of freezing. Active non-diapausing mites survived on rose leaves in Kyoto (35°N) throughout the winters of 1988–1989 and 1989–1990. Cultures of mites with low (LD) and high (HD) diapause capacities at 18°C and 9L-15D photoperiod were successfully selected from the rose population and from a population on chrysanthemum in Nara (34.4°N). Their life-history traits at 15, 20, 25 and 30°C were characterized. HD and LD mites from both populations were of similar ages at first reproduction at 15–30° C. However, at temperatures 20° C, HD individuals produced more eggs than LD individuals, resulting in higher fecundity and intrinsic rate of natural increase. These traits allow HD individuals, which stop breeding between October and April, to increase faster in summer than LD individuals. This provides a mechanism, together with climatic fluctuations, in maintaining the coexistence of diapausing and non-diapausing T. urticae in Kyoto where winter conditions are rarely lethal to the non-diapausing individuals.     

A fecundity cost of (walking) mobility in an insect

Evolutionary theory predicts trade‐offs between fecundity and mobility, but there is substantial lack of empirical evidence if and how basic mobility relates to fitness costs. In a field experiment, we investigated fecundity costs of mobility in a non‐migratory, wing‐monomorphic grasshopper, Stenobothrus lineatus, and at the same time tested for possible effects of reproductive state (egg‐load) on the mobility. For 10 days, body weight and activity radius of 60 females were recorded daily and oviposition events were inferred from abrupt weight losses. We found a strong and significant relationship between the individual mobility and the time between egg pods laid (interpod period). Individual egg‐laying was reduced by a rate of 0.36 eggs per day with each meter increase in mean daily activity radius. The trade‐off was not biased by the size of the females, that is, constitution did not positively influence both offspring number and mobility. Egg‐load had no significant influence on the individual distances travelled. We could demonstrate that mobility – as induced and selected for by foraging, thermoregulation, predator escape, shelter seeking, and reproduction – can be directly paid off by fecundity. This direct consequence of mobility on individual fitness was detected for the first time in a walking insect.     

The distribution, age and growth of wrasse (Labridae) in inshore waters of west Scotland

Wrasse were widely distributed in inshore waters of west Scotland in rocky and algal habitats. Ctenolabrus rupestris and Centrolabrus exoletus dominated commercial and experimental catches using creels, traps and fyke nets, but Crenilabrus melops, Labrus bergylta and L. mixtus were infrequent. Maximum age of sampled fish was 16yr in C. rupestris , 9 yr in C. exolefus , 5 yr in C. melops , 15 yr in L. bergylta , and 11 yr in L. mixtus . Growth was more rapid prior to maturation in all species. The von Bertalanffy growth model fitted data for C. rupestris and C. exoletus . Male C. rupestris and C. exoletus were significantly longer than females in most age groups and growth of all species captured in mid–Scottish areas was more rapid than in northern localities. Mortality (Z) of C. rupestris was 0–1861 per year and 0·4185 in C exoletus .     

Phenotypic plasticity and constancy of life-history traits in laboratory clones of Daphnia magna Straus: effects of neonatal length

1. The phenotypic constancy of four laboratory Daphnia magna clones in fitness-related life-history traits, such as age and clutch size at maturity, was studied among consecutive experimental runs in differing food environments.
2. A significant part of the observed clonal and genetic-by-environmental variation in age and clutch size at maturity was explained by experimentally uncontrollable variations in neonatal body length.
3. Despite food availability, neonatal length determined the number of instars invested to maturity and thus maturation age. Clonal differences in neonatal length and thus in maturation instar occurrence across environments explained most of the clonal variability observed in maturation age.
4. Although interclonal differences in clutch size existed, most of the phenotypic plasticity observed for clutch size was mediated by clonal differences in neonatal length.
5. Clonal differences in neonatal length and in the occurrence of maturation instars across environments dramatically affected the body length of instar IM-2 where provisioning of eggs take place. Since clutch size is determined from clutch mass and clutch mass was strongly related to the body length of instar IM-2, clonal differences across environments in body length of instar IM-2 mirrored clonal differences across environments in clutch size.
6. The results reported in the present study show that maternally mediated traits such as neonatal length affect how genotypes respond to different environmental selection regimes (genetic-by-environmental interaction). Future research needs to focus on the effects of neonatal length on the heritability or genetic variation of the reaction norms, since prediction of the response to selection is a key research objective in quantitative genetic studies.     

Behavioral repertoire of biparental care in Apistogramma trifasciata (Pisces: Cichlidae)

Cichlid fish exhibit a complex behavioral repertoire, mainly regarding social and reproductive behaviors. Nevertheless, although dwarf cichlids exhibit a remarkable diversity of behaviors, only a few studies have been conducted with these fish. Apistogramma trifasciata is a common dwarf cichlid in the Neotropics and widely used as ornamental fish. Both males and females are territorial and engage in biparental care. Here we observed the behavior of A. trifasciata males and females to construct an ethogram. We registered the parental care of a couple since the spawn until the moment when the offspring became independent. Striking behaviors were observed, such as male-male contests involving circling displays and mouth wrestling, and parental care, which involved mouth brooding and parental color change. Finally, we suggest that our results may be used to establish this species as a model for parental care and territoriality studies.     

Phenotypic plasticity of pigmentation and morphometric traits in Pnigalio soemius (Hymenoptera: Eulophidae)

Species of the genus Pnigalio Schrank are ectoparasitoids on several pest insects. Most species are polyphagous parasitoids of lepidopteran and dipteran leafminers. Despite their potential economic importance, information on intraspecific phenotypic variability is insufficient. Pnigalio soemius (Walker) was reared at five different temperatures (10, 15, 20, 25, 30 degrees C) on mature larvae of one of its natural hosts, Cosmopterix pulchrimella Chambers (Lepidoptera: Cosmopterigidae), to investigate the influence of temperature on size, colour and other morphological traits, and to measure the range of variation of several characters. Thermal developmental reaction norms, which represent the effect of temperature during growth and development on the value of some adult traits, were produced. The results confirmed the influence of temperature on numerous characters and that these characters had a larger range of variation than realized previously in the construction of taxonomic keys to species. In particular, the number and position of the costulae on the propodeum and colour of the gaster were affected by rearing temperature.     

Phenotypic plasticity in reproductive traits: importance in the life history of Helix aspersa (Mollusca: Helicidae) in a recently colonized habitat

Reproductive traits of the land snail Helix aspersa Mtiller were investigated under artificial conditions from two samples, one collected from a population exposed to unpredictable human pressures in its natural environment, i.e. a recently created polders area with intensive agriculture, and the other from a snail farm in which animals were reared under constant conditions denned as 'optimal' for growth and reproduction. Results were compared with data collected from natural populations of the same region (Brittany) and from habitats spanning the environmental heterogeneity of the range of the species. A large part of the variation among populations could be explained by different phenotypic covariances between shell size, clutch size and egg size, but not by the number of clutches per snail. Thus, the higher egg production of snails from the polders was related to (i) a strong correlation between clutch size and shell size, shell size being in the upper limit of the overall range for the region concerned; (ii) an uncommonly low egg weight in comparison with the 'norm' of Helix aspersa , this trait seeming to be involved in a trade-off with clutch size. Second clutches were smaller than the first ones, but their eggs were significantly heavier. This difference may be linked to a size-dependent mortality of juveniles during winter which arises in all populations in which hibernation occurs as an adaptation to low temperatures. In addition to the selective regime usually involved for populations of helicid snails from Western Europe, several unpredictable mortality factors occurred in the polders area: herbicide and pesticide treatments (lethal for young snails), human predation (lethal for adults) and burning (letiial for all snails). Life-history patterns of Helix aspersa are discussed in relation to its ability to successfully colonize a large range of habitats modified by humans, to such an extent that it can become a pest.     

Olfactory and physical manipulation by males on life-history traits in Echinothrips americanus MORGAN 1913 (Thysanoptera: Thripidae)

Thrips are highly successful invaders due to their broad host range, cryptic lifestyle, fast development of insecticide resistance and adaptability to changing environmental conditions. Echinothrips americanus is native to the eastern USA and has now spread to over 30 countries, including Europe, Asia and Australia. This species is able to adapt oviposition rate, duration of larval development and sex ratio of progeny in relation to the mating status of the mother and presence of males. We designed experiments to distinguish between the mechanical and olfactory male contact for these changes in longevity, fecundity and developmental time of E. americanus. Individuals were reared either pairwise or with known male pheromonal substances (dimethylglutarate DBE-5 and dimethyladipate DBE-6), but separated by gauze from each other, which allows olfactory perception but no physical contact. Longevity, fecundity of the parents as well as developmental time and sex ratio of the progeny were recorded. Mated females had a significantly lower longevity under the impact of DBE-5, compared to virgin ones. On the other hand, mating status itself is shown to affect oviposition rate and total fecundity, as well as developmental time of the progeny. Offspring of mated females had a slower development, compared to offspring of virgin mothers. Alternative strategies for integrative pest management that use male-produced pheromones are discussed.     

Variation in female life-history traits among Alaskan populations of the threespine stickleback, Gasterosteus aculeatus L. (Pisces: Gasterosteidae)

Life-history characteristics of female threespine stickleback (Gasterosteus aculeatus) were examined in 12 populations, 11 freshwater and one anadromous, within the Cook Inlet region of Alaska. Because this area has been deglaciated during the last 20 000 years, the freshwater populations are recently derived, probably independendy, from the local marine or anadromous stickleback. Freshwater threespine stickleback have undergone considerable morphological evolution within this region, apparently in response to environmental factors including predatory regimes and environmental productivity. Our freshwater study populations were selected to sample this range of morphological variation in order to determine whether life-history traits and morphologies have followed similar evolutionary trajectories. Freshwater populations could be categorized generally into one of three ecomorphotypes: those inhabiting relatively productive lakes having one or more piscivorous fishes present, and in which the stickleback exhibit a fully developed pelvic girdle; those inhabiting low-calcium lakes that lack piscivorous fishes, and in which the pelvic structures are incomplete; those living in streams with piscivorous fishes, in which the stickleback have fully developed pelvic girdles. The anadromous population constituted a fourth ecomorphotype that lives in marine waters, and is robusdy armored. The freshwater populations showed considerable variation in all life-history traits assessed, and this variation generally corresponded to our ecomorphological classifications. Nevertheless, within each ecomorphotype there was sufficient variation to suggest that morphological and life-history traits may not always respond in the same manner in response to the same selective regime.     

Distribution of behaviours and species interactions within home range contours in five Caribbean reef fish species (Family Labridae)

Synopsis This study investigated the distribution of behaviours and species interactions within home range contours in five Caribbean labrid species: Halichoeres bivittatus, H. garnoti, H. maculipinna, H. poeyi, and Thalassoma bifasciatum. For this study, contours were defined as: (a) 30%—the core use area, (b) 30–75%—the intermediate activity area, and (c) 75–95%—the peripheral activity area. Behaviours analyzed for this study included: (i) feeding (=biting the substrate or chewing), (ii) chased by pomacentrids, (iii) swimming alone, (iv) swimming with other fishes, and (v) all activities with other fishes. Fifty-nine percent of Halichoeres bivittatus observed showed a higher frequency than expected being chased by pomacentrids in the peripheral region of their home ranges. Halichoeres garnoti showed a lower frequency than expected swimming with other individuals in their core use area, and 64% of the individuals observed showed a higher frequency than expected being chased by pomacentrids in the peripheral region. In general, H. maculipinna exhibited a random distribution of behaviours throughout their home range areas, with a non-significant trend for more agonistic interactions with pomacentrids in peripheral regions. Halichoeres poeyi and T. bifasciatum showed higher frequencies than expected being chased by pomacentrids in the peripheral regions. Overall, the non-random distribution of agonistic interactions with pomacentrids throughout home range areas suggests that the presence or prior residence of territorial pomacentrids on coral reefs may modify the post-settlement selection of home range areas by these labrid species.     

Phylogeny, biogeography, and the evolution of life-history traits in Leucadendron (Proteaceae)

Leucadendron is a moderately large genus of Proteaceae almost entirely restricted to the Cape Floristic Region of southern Africa. The genus is unusual in being dioecious and sexually dimorphic. ITS sequence data were obtained from 62 of the 96 currently recognized taxa (85 species and 11 subspecies). Phylogenetic analyses were conducted under Maximum Likelihood and parsimony and resolved nine groups of species with varying degrees of bootstrap support, but relationships between these groups are largely unsupported. The phylogeny conflicts with the current taxonomic arrangement, which is based mainly on fruit morphology. The two sections of the genus, Alatosperma and Leucadendron, and several subsections within these sections, are resolved as non-monophyletic. This means that taxonomically important characters (such as fruit shape) have evolved multiple times, as the species with nut-like fruit (resolved into two of the nine groups) appear to have evolved independently from ancestors with winged fruit. Based on the topology obtained, the life history traits of anemophily, myrmechochory, and re-sprouting have also originated multiple times. Dispersal-Vicariance (DIVA) analysis suggests that the genus had an ancestral area in the Karoo Mountain and Southeastern phytogeographic centres of endemism in the southwestern Cape.     

Phenotypic plasticity and selection in Drosophila life history evolution. 2. Diet,mates and the cost of reproduction

While it is commonplace for biologists to use the response to environmental manipulation as a guide to evolutionary responses to selection, the relationship between phenotypic plasticity and genetic change is not generally well-established. The life-histories of laboratory Drosophila populations are among the few experimental systems which simultaneously afford information on phenotypic plasticity and evolutionary trajectories. We employed a combination of two replicated selectively differentiated stocks (postponed aging stocks and their controls; 10 populations in total) and two different environmental manipulations (nutrition and mating) to explore the empirical relationship between phenotypic plasticity and evolutionary trajectories. While there are a number of parallels between the results obtained using these two approaches, there are important differences. In particular, as the detail of the biological characterization of either type of response increases, so their disparities multiply. Nonetheless, the combination of environmental manipulation with evolutionary divergence provides valuable information about the biological connections between life-history, caloric reserves, and reproductive physiology in Drososphila.     

A comparative study on morphology, growth rate and reproduction of Clarias gariepinus (Burchell, 1822), Heterobranchus longifilis Valenciennes, 1840, and their reciprocal hybrids (Pisces, Clariidae)

A detailed study on reproduction indicated that female C. gariepinus mature earlier (5–7 months) than female H. longifilis (12–14 months). In the reciprocal hybrids, female first sexual maturity was attained at 20–21 months. Both reciprocal hybrids and parental species displayed an equilibrated sex ratio. Macroscopical and microscopical observations revealed numerous abnormalities in gonadal development of the hybrids. GSI and fecundity in female hybrids were considerably lower than those found in the parental species. Moreover, intra-ovarian tumors occurred in 20% of the hybrids. In hybrid males, GSIs were generally higher than those found in the parental species, but the spermatozoa concentration in the semen was about 100 times less. Despite these abnormalities, viable larvae, resulting from F2 and backcross fertilizations, were obtained.