Inbreeding variability and population structure in the invasive haplodiploid palm‐seed borer (Coccotrypes dactyliperda)

We investigated the mating system and population genetic structure of the invasive haplodiploid palm‐seed borer Coccotrypes dactyliperda in California. We focused on whether these primarily inbreeding beetles have a ‘mixed‐breeding’ system that includes occasional outbreeding, and whether local inbreeding coefficients (F_IS) varied with dominant environmental factors. We also analysed the genetic structure of C. dactyliperda populations across local and regional scales. Based on the analysis of genetic variation at seven microsatellite loci in 1034 individual beetles from 59 populations, we found both high rates of inbreeding and plentiful evidence of mixed‐breeding. F_IS ranged from ?0.56 to 0.90, the highest variability reported within any animal species. There was a negative correlation between F_IS and latitude, suggesting that some latitude‐associated factor affecting mating decisions influenced inbreeding rates. Multiple regressions suggested that precipitation, but not temperature, may be an important correlate. Finally, we found highly significant genetic differentiation among sites, even over short geographic distances (< 1000 m).     

The mixed mating system of the sea palm kelp Postelsia palmaeformis: few costs to selfing

Naturally isolated populations have conflicting selection pressures for successful reproduction and inbreeding avoidance. These species with limited seasonal reproductive opportunities may use selfing as a means of reproductive assurance. We quantified the frequency of selfing and the fitness consequences for inbred versus outcrossed progeny of an annual kelp, the sea palm (Postelsia palmaeformis). Using experimentally established populations and microsatellite markers to assess the extent of selfing in progeny from six founding parents, we found the frequency of selfing was higher than expected in every population, and few fitness costs were detected in selfed offspring. Despite a decline in heterozygosity of 30 per cent in the first generation of selfing, self-fertilization did not affect individual size or reproduction, and correlated only with a marginally significant decline in survival. Our results suggest both that purging of deleterious recessive alleles may have already occurred and that selfing may be key to reproductive assurance in this species with limited dispersal. Postelsia has an alteration of a free-living diploid and haploid stage, where the haploid stage may provide increased efficiency for purging the genetic load. This life history is shared by many seaweeds and may thus be an important component of mating system evolution in the sea.     

Isolation and characterization of microsatellites in Sparganium emersum and cross‐species amplification in the related species S. erectum

We developed seven novel polymorphic microsatellite loci for the aquatic macrophyte Sparganium emersum (Sparganiaceae). These were characterized on 62 individuals collected from nine different populations. In this set of individuals, seven to 20 alleles per locus were detected and observed heterozygosity ranged between 0.16 and 0.95. Cross‐species amplification was tested in the related species Sparganium erectum, and was successful for five of the seven microsatellite loci.     

The European spruce bark beetle <Emphasis Type="Italic">Ips typographus</Emphasis> in a national park: from pest to keystone species

The influence of natural disturbance on biodiversity is poorly known in the intensively cultivated landscape of Europe. As an example of insect disturbance we studied effects of gaps generated by outbreaks of the spruce bark beetle (Ips typographus) on biodiversity in the area of the National Park “Bavarian Forest” and compared them with openings (e.g. meadows) created by humans in these forests. Insects were sampled using flight interception traps across twelve ecotones between edges of closed forest, six bark beetle gaps and six meadows. The diversity and species density of true bugs and of bees/wasps increased significantly from the closed stand to the edge, and continued to increase inside the openings at interior and exterior edges. Species density in saproxylic beetles also increased significantly from closed forest to opening, but only across ecotones including bark beetle gaps. Similarly, the number of critically endangered saproxylic beetles increased significantly in bark beetle gaps. Using indicator species analysis a total of 60 species were identified as possessing a statistically significant value indicating preference for one of the habitat types along the ecotones: 29 of them preferred gaps, 24 preferred meadows, three were characteristic for edges of meadows, three for edges of bark beetle gaps, but only one was typical of closed forest. Most of our results support the thesis that I. typographus fulfils the majority of criteria for a keystone species, particularly that of maintenance of biodiversity in forests. Our results emphasize the value for the study and conservation of insect diversity of the policy of non-interference with natural processes pursued in some protected areas. As a recommendation to forest management for increasing insect diversity even in commercial forest, we suggest that logging in recent gaps in medium aged mixed montane stands should aim at retention of a part of the dead wood. Planting should be avoided, to lengthen the important phase of sunlit conditions.     

Outbreeding and lack of temporal genetic structure in a drone congregation of the neotropical stingless bee Scaptotrigona mexicana

Drone aggregations are a widespread phenomenon in many stingless bee species (Meliponini), but the ultimate and proximate causes for their formation are still not well understood. One adaptive explanation for this phenomenon is the avoidance of inbreeding, which is especially detrimental for stingless bees due to the combined effects of the complementary sex-determining system and the small effective population size caused by eusociality and monandry. We analyzed the temporal genetic dynamics of a drone aggregation of the stingless bee Scaptotrigona mexicana with microsatellite markers over a time window of four weeks. We estimated the drones of the aggregation to originate from a total of 55 colonies using sibship re-construction. There was no detectable temporal genetic differentiation or sub-structuring in the aggregation. Most important, we could exclude all colonies in close proximity of the aggregation as origin of the drones in the aggregation, implicating that they originate from more distant colonies. We conclude that the diverse genetic composition and the distant origin of the drones of the S. mexicana drone congregation provides an effective mechanism to avoid mating among close relatives.     

Isolation,characterization and cross‐species amplification of microsatellite loci in the cycad genus Dioon (Zamiaceae). Potential utilization in population genetics studies of Dioon edule

Dioon edule (Zamiaceae) is an endemic Mexican cycad. Nineteen microsatellite loci were isolated from three enriched genomic libraries of D. edule var. angustifolium, D. tomasellii, and D. caputoi. Seven of these loci showed polymorphisms in D. edule. Levels of polymorphism were assessed using 16 individuals from each of seven populations throughout the range of this species. The number of alleles per locus ranged from two to five and the observed and expected heterozygosities ranged from 0.0 to 0.9821 and from 0.0088 to 0.6318, respectively. All loci show significant linkage disequilibrium. Three loci depart significantly from Hardy–Weinberg equilibrium.     

Seasonal variation in the mating system of a selfing annual with large floral displays

Background and Aims Flowering plants display considerable variation in mating system, specifically the relative frequency of cross- and self-fertilization. The majority of estimates of outcrossing rate do not account for temporal variation, particularly during the flowering season. Here, we investigated seasonal variation in mating and fertility in Incarvillea sinensis (Bignoniaceae), an annual with showy, insect-pollinated, ‘one-day’ flowers capable of delayed selfing. We examined the influence of several biotic and abiotic environmental factors on day-to-day variation in fruit set, seed set and patterns of mating.Methods We recorded daily flower number and pollinator abundance in nine 3 × 3-m patches in a population at Mu Us Sand land, Inner Mongolia, China. From marked flowers we collected data on daily fruit and seed set and estimated outcrossing rate and biparental inbreeding using six microsatellite loci and 172 open-pollinated families throughout the flowering period.Key Results Flower density increased significantly over most of the 50-d flowering season, but was associated with a decline in levels of pollinator service by bees, particularly on windy days. Fruit and seed set declined over time, especially during the latter third of the flowering period. Multilocus estimates of outcrossing rate were obtained using two methods (the programs MLTR and BORICE) and both indicated high selfing rates of ∼80 %. There was evidence for a significant increase in levels of selfing as the flowering season progressed and pollinator visitation declined. Biparental inbreeding also declined significantly as the flowering season progressed.Conclusions Temporal variation in outcrossing rates may be a common feature of the mating biology of annual, insect-pollinated plants of harsh environments but our study is the first to examine seasonal mating-system dynamics in this context. Despite having large flowers and showy floral displays, I. sinensis attracted relatively few pollinators. Delayed selfing by corolla dragging largely explains the occurrence of mixed mating in I. sinensis, and this mode of self-fertilization probably functions to promote reproductive assurance when pollinator service is limited by windy environmental conditions and competition from co-occurring flowering plants.     

Using a reference population yardstick to calibrate and compare genetic diversity reported in different studies: an example from the brown bear

In species with large geographic ranges, genetic diversity of different populations may be well studied, but differences in loci and sample sizes can make the results of different studies difficult to compare. Yet, such comparisons are important for assessing the status of populations of conservation concern. We propose a simple approach of using a single well-studied reference population as a ‘yardstick'' to calibrate results of different studies to the same scale, enabling comparisons. We use a well-studied large carnivore, the brown bear (Ursus arctos), as a case study to demonstrate the approach. As a reference population, we genotyped 513 brown bears from Slovenia using 20 polymorphic microsatellite loci. We used this data set to calibrate and compare heterozygosity and allelic richness for 30 brown bear populations from 10 different studies across the global distribution of the species. The simplicity of the reference population approach makes it useful for other species, enabling comparisons of genetic diversity estimates between previously incompatible studies and improving our understanding of how genetic diversity is distributed throughout a species range.     

Adaptive significance of the recurrent photoperiodic response in a spring‐breeding carabid beetle,Carabus yaconinus

Seasonal changes in the photoperiodic sensitivity for reproduction in adults of a spring‐breeding carabid beetle, Carabus yaconinus (Coleoptera: Carabidae), were examined by transferring adults from outdoor to photoperiodic conditions in various seasons. Newly‐emerged adults transferred to the laboratory in September to December showed a long‐day photoperiodic response, but lost photoperiodic sensitivity gradually during winter. In late April, overwintered adults were not sensitive to the photoperiod, with females continuing to have mature eggs under both long‐day and short‐day conditions. In contrast, in late June and late July, the adults were sensitive to the photoperiod, with only those kept under short‐day conditions re‐entering reproductive diapause. This recovery of photoperiodic sensitivity appears to play a definitive role in maintenance of diapause in autumn for adults that have reproduced. The adults collected in late April regained photoperiodic sensitivity in two months even after being kept under unchanged conditions. Therefore, no environmental cue is required for recovery of photoperiodic sensitivity, which apparently recovers with the lapse of time. Our results suggest that the recurrent photoperiodic response is required in long‐living adults of C. yaconinus to regulate the timing of reproduction, and also indicate a difference in photoperiodic sensitivity in summer between overwintered and newly‐emerged adults.     

Local selection and population structure in a deep‐sea fish,the roundnose grenadier (Coryphaenoides rupestris)

Local populations within a species can become isolated by stochastic or adaptive processes, though it is most commonly the former that we quantify. Using presumably neutral markers we can assess the time‐dependent process of genetic drift, and thereby quantify patterns of differentiation in support of the effective management of diversity. However, adaptive differences can be overlooked in these studies, and these are the very characteristics that we hope to conserve by managing neutral diversity. In this study, we used 16 hypothetically neutral microsatellite markers to investigate the genetic structure of the roundnose grenadier in the North Atlantic. We found that one locus was a clear outlier under directional selection, with F_ST values much greater than at the remaining loci. Differentiation between populations at this locus was related to depth, suggesting directional selection, presumably acting on a linked locus. Considering only the loci identified as neutral, there remained significant population structure over the region of the North Atlantic studied. In addition to a weak pattern of isolation by distance, we identified a putative barrier to gene flow between sample sites either side of the Charlie‐Gibbs Fracture Zone, which marks the location where the sub‐polar front crosses the Mid‐Atlantic Ridge. This may reflect a boundary across which larvae are differentially distributed in separate current systems to some extent, promoting differentiation by drift. Structure due to both drift and apparent selection should be considered in management policy.     

Flexible mating system in a logged population of <Emphasis Type="Italic">Swietenia macrophylla</Emphasis> King (Meliaceae): implications for the management of a threatened neotropical tree species

Microsatellites were used to evaluate the mating system of the remaining trees in a logged population of Swietenia macrophylla, a highly valuable and threatened hardwood species, in the Brazilian Amazon. A total of 25 open pollinated progeny arrays of 16 individuals, with their mother trees, were genotyped using eight highly polymorphic microsatellite loci. Genotypic data analysis from the progeny arrays showed that 373 out of the 400 seedlings (93.25%) were unambiguously the result of outcrossed matings and that the remaining 6.75% had genotypes consistent with self-fertilisation. Apomixis could be ruled out, since none of the 400 seedlings analysed had a multi-locus genotype identical to its mother tree. The high estimate of the multi-locus outcrossing rate (t _m = 0.938 ± 0.009) using the mixed mating model also indicated that the population in this remnant stand of S. macrophylla was predominantly allogamous. The relatively large difference between the multi-locus and single-locus outcrossing estimates (t _m −t _s = 0.117 ± 0.011) provides evidence that, in spite of the high outcrossing rate, a considerable degree of biparental inbreeding has contributed to the genetic structure of this population. Levels of outcrossing were not evenly distributed among maternal trees (t _m ranging from 0.39 to 1.00), suggesting the occurrence of a variable degree of self-incompatibility and/or dichogamy among individual trees of this monoecious species. Due to its generalist pollination system and some level of tolerance for selfing, S. macrophylla seems to be resilient to environmental disturbances such as those caused by logging, since it sets fruits with predominantly outcrossed seeds even at low stand densities. Therefore, the remaining individuals in logged areas or in relict fragments may be very important for long-term population recovery and genetic conservation programmes.     

Variance in reproductive success and the opportunity for selection in a serially monogamous species: simulations of the mating system of <Emphasis Type="Italic">Tropheus</Emphasis> (Teleostei: Cichlidae)

Sexual selection is believed to play a major role in speciation processes of cichlid fishes in the East African Great Lakes, in particular Lakes Malawi and Victoria, by driving diversification in male nuptial coloration. In Lake Tanganyika, a high rate of color pattern diversification is found in the genus Tropheus, where more than 100, mostly allopatric, color morphs have been described. Whether color pattern differentiation in Tropheus could follow from sexual selection as well, has not yet been conclusively shown. Unlike typical sexually selected species, Tropheus are sexually monomorphic, establish temporary pair bonds and spawn monogamously. Variance in mating success among individuals would still allow for sexual selection, but due to their high population census sizes, parentage data from natural populations are difficult to obtain. Simulations designed according to existing data on mating behavior in Tropheus suggested that variance in male reproductive success can be substantial and lead to levels of opportunity for selection, which are similar to values estimated, for example, from natural populations of sexually dimorphic songbirds. Variance in male success was mostly affected by the way females perceived and reacted to differences between males, and to a lesser extent by the duration of components of the reproductive cycles of males and females. These results indicate that future work on the importance of sexual selection in Tropheus should concentrate on mate choice cues and female mate choice behavior, but does not depend critically on the acquisition of more detailed life history data.     

Forest succession and prey availability influence the strength and scale of terrestrial‐aquatic linkages in a headwater salamander system

1. Trophic linkages between terrestrial and aquatic ecosystems are common and sensitive to disruption. However, there is little information on what causes variation in the strength and spatial scale of these linkages. 2. In the highly aquatic adults of the headwater salamander Gyrinophilus porphyriticus (family Plethodontidae), use of terrestrial prey decreases along a gradient from early‐ to late‐successional riparian forests. To understand the cause of this relationship, we tested the predictions that (i) terrestrial prey abundance is lower in late‐successional forests, and (ii) G. porphyriticus adults cannot move as far from the stream to forage in late‐successional forests, thus limiting access to terrestrial prey. 3. We established 100‐m long study reaches on six headwater streams in the Hubbard Brook Experimental Forest, New Hampshire. Three reaches were in early‐successional forests and three were in late‐successional forests. We conducted pitfall trapping for invertebrate prey in June and July of 2005, with three traps at 0, 2, 5 and 10 m from the stream at each reach. In June, July and August of 2004 and 2005, nighttime salamander surveys were conducted at each reach along ten, 10‐m long by 2.5‐m wide transects perpendicular to the stream. 4. Abundance of terrestrial prey was consistently lower in late‐successional forests, suggesting that consumption of terrestrial prey by G. porphyriticus is affected by prey abundance. Contrary to our prediction, G. porphyriticus adults moved farther from the stream in late‐successional forests, suggesting that habitat conditions in late‐successional forests do not limit movement away from the stream, and that lower abundances of terrestrial prey in these forests may cause salamanders to move farther from streams. 5. Our results provide novel insight on the extent of terrestrial habitat use by G. porphyriticus. More broadly, these results indicate that major habitat gradients, such as forest succession, can affect the strength and scale of terrestrial‐aquatic linkages. Application of this insight to the design of vegetation buffers along headwater streams would have widespread benefits to freshwater ecosystems.     

Plasticity of reproductive traits responding to variation in light availability at the rosette stage of the first year in a strict biennial,Pedicularis torta,from a field on the Qinghai–Tibet Plateau,China

Light is a fundamental heterogeneous environmental factor for plants and often varies at both spatial and temporal scales. In the present study, we carried out a shading experiment to investigate the effect of variable light availability at the rosette stage of the first year in the strict biennial species Pedicularis torta (an endemic species of the Qinghai‐Tibet Plateau) on reproductive traits (i.e. total number of flowers per plant, total number of fruits per plant/total number of flowers per plant, the number of seeds per fruit, mean individual seed mass and estimation of the total number of seeds per plant, plant size at maturity in the second year and on the relationships between reproductive traits and plant size at this stage). We found that light availability affected most of the reproductive traits (except for mean individual seed mass), plant size at maturity in the second year, and the relationship between the total number of flowers per plant and plant size at this stage. Our results indicate that reproductive traits respond to changes in light availability during the rosette plant stage.     

Copulation Is Not a Prerequisite to Male Reception of Eggs in the Golden Egg Bug Phyllomorpha laciniata (Coreidae; Heteroptera)

Females of the golden egg bug, Phyllomorpha laciniata, lay eggs on the backs of conspecifics. Male response to female oviposition attempts is either passive or resistant. Passive males remain still during oviposition, while resistant males move repeatedly and thereby delay or avoid being encumbered. We investigated how previous mating experience affected male acceptance of eggs. Males from two Spanish populations, from Andalusia and Catalonia, were allowed to mate with single females repeatedly. These experimental pairs were then presented with either a single, nonmating male or a pair in copula. We expected mating partners to resist oviposition attempts less strongly than nonmating males but no differences were detected. However, there was a significant difference in behavior exhibited by males from the two populations; males from Catalonia were relatively passive but males from Andalusia routinely resisted encumbrance. Predation pressure and the availability of receptive females may explain the observed differences between the populations.     

Molecular cloning of the promoter region of the glyceraldehyde-3-phosphate dehydrogenase gene that contributes to the construction of a new transformation system in <Emphasis Type="Italic">Coriolus versicolor</Emphasis>

The white-rot basidiomycete Coriolus versicolor secretes several enzymes that participate in the degradation of lignin and various persistent organic pollutants. In this study, we attempted to establish a genetic transformation system with a homogenous promoter sequence for driving the gene for antibiotic resistance. We succeeded in cloning the promoter sequence of the gene for glyceraldehyde-3-phosphate dehydrogenase (gpd), which is expressed at high levels in C. versicolor. The expression vector pT7GPTHPT was constructed, which included a gene for resistance to hygromycin B under control of the gpd promoter. The successful selection of transformants on medium that contained hygromycin B indicated that the system should be useful not only for the genetic transformation of C. versicolor, but also for the overproduction of useful fungal enzymes such as laccase and peroxidase.     

Development of a system for the on‐line measurement of carbon dioxide production in microbioreactors: Application to aerobic batch cultivations of Candida utilis

We developed and applied a conductometric method for the quantitative online measurement of the carbon dioxide (CO₂) production during batch cultivations of Candida utilis on a 100‐μL scale. The applied method for the CO₂ measurement consisted of absorption of the produced CO₂ from the exhaust gas of the microbioreactor in an alkali solution, of which the conductivity was measured on‐line. The measured conductivity change of the alkali solution showed a linear relation with the total amount of CO₂ absorbed. After calibration of the CO₂ measurement system, it was connected to a well of a 96‐well microtiter plate. The mixing in the well was achieved by a magnetic stirrer. Using online measurement of the CO₂ production during the cultivation, we show reproducible exponential batch growth of C. utilis on a 100‐μL scale. The CO₂ production measurements obtained from the microcultivation were compared with the CO₂ production measurement in a 4‐L bioreactor equipped with a conventional off‐gas analyzer. The measurements showed that on‐line measurement of the CO₂ production rate in microbioreactors can provide essential data for quantitative physiological studies and provide better understanding of microscale cultivations. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009