Find research datasets worth reusing

Data from: Inbreeding depression does not increase after exposure to a stressful environment: a test using compensatory growth

Background: Inbreeding is often associated with a decrease in offspring fitness ('inbreeding depression'). Moreover, it is generally assumed that the negative effects of inbreeding are exacerbated in stressful environments. This G × E interaction has been explored in many taxa under different environmental conditions. These studies usually manipulate environmental conditions either in adulthood or throughout an individual's entire life. Far fewer studies have tested how stressful environments only experienced during development subsequently influence the effects of inbreeding on adult traits. Results: We experimentally manipulated the diet (control versus low food) of inbred and outbred juvenile Eastern mosquitofish (Gambusia holbrooki) for three weeks (days 7-28) to test whether experiencing a presumably stressful environment early in life influences their subsequent growth and adult phenotypes. The control diet was a standard laboratory food regime, while fish on the low food diet received less than 25 % of this amount of food. Unexpectedly, despite a large sample size (237 families, 908 offspring) and a quantified 23 % reduction in genome-wide heterozygosity in inbred offspring from matings between full-siblings (f = 0.25), neither inbreeding nor its interaction with early diet affected growth trajectories, juvenile survival or adult size. Individuals did not mitigate a poor start in life by showing 'compensatory growth' (i.e. faster growth once the low food treatment ended), but they showed 'catch-up growth' by delaying maturation. There was, however, no effect of inbreeding on the extent of catch-up growth. Conclusions: There were no detectable effects of inbreeding on growth or adult size, even on a low food diet that should elevate inbreeding depression. Thus, the long-term costs of inbreeding due to lower male reproductive success we have shown in another study appear to be unrelated to inbreeding depression for adult male size or the growth rates that are reported in the current study.

Data from: Experimental test of genetic rescue in isolated populations of brook trout

Genetic rescue is an increasingly considered conservation measure to address genetic erosion associated with habitat loss and fragmentation. The resulting gene flow from facilitating migration may improve fitness and adaptive potential, but is not without risks (e.g., outbreeding depression). Here, we conducted a test of genetic rescue by translocating ten (five of each sex) brook trout (Salvelinus fontinalis) from a single source to four nearby and isolated stream populations. To control for the demographic contribution of translocated individuals, ten resident individuals (five of each sex) were removed from each recipient population. Prior to the introduction of translocated individuals, the two smallest above-barrier populations had substantially lower genetic diversity, and all populations had reduced effective number of breeders relative to adjacent below-barrier populations. In the first reproductive bout following translocation, 31 of 40 (78%) translocated individuals reproduced successfully. Translocated individuals contributed to more families than expected under random mating and generally produced larger full-sibling families. We observed relatively high (>20%) introgression in three of the four recipient populations. The translocations increased genetic diversity of recipient populations by 45% in allelic richness and 25% in expected heterozygosity. Additionally, strong evidence of hybrid vigour was observed through significantly larger body sizes of hybrid offspring relative to resident offspring in all recipient populations. Continued monitoring of these populations will test for negative fitness effects beyond the first generation. However, these results provide much-needed experimental data to inform the potential effectiveness of genetic rescue-motivated translocations.

opencc-zeroDec 2011View details →

Data from: CLIP test: a new fast, simple and powerful method to distinguish between linked or pleiotropic quantitative trait loci in linkage disequilibria analysis

An important question arises when mapping quantitative trait loci (QTLs) for genetically correlated traits: is the correlation due to pleiotropy (a single QTL affecting more than one trait) and/or close linkage (different QTLs that are physically close to each other and influence the traits)? In this article, we propose the Close Linkage versus Pleiotropism (CLIP) test, a fast, simple and powerful method to distinguish between these two situations. The CLIP test is based on the comparison of the square of the observed correlation between a combination of apparent effects at the marker level to the minimal value it can take under the pleiotropic assumption. A simulation study was performed to estimate the power and alpha risk of the CLIP test and compare it to a test that evaluated whether the confidence intervals of the two QTLs overlapped or not (CI test). On average, the CLIP test showed a higher power (68%) to detect close-linked QTLs than the CI test (43%) and a same alpha risk (4%).

opencc-zeroDec 2012View details →

Data from: Testing the link between phenotypic evolution and speciation: an integrated paleontological and phylogenetic analysis

1. The punctuated equilibrium model predicts that phenotypic change is concentrated into pulses associated with speciation, with little change otherwise accruing in established lineages. Paleontological tests of this model have generally lacked an adequate phylogenetic and modeling framework, whereas tests relying on extant populations lack direct constraints on the evolutionary dynamics within lineages. 2. The present study extends a modeling approach developed in comparative studies and applies it to a clade with a rich fossil record, the deep-sea ostracode genus Poseidonamicus. Using a phylogenetic framework and an independent set of shape traits plus body size, a model was fit that allows estimation of anagenetic (within-lineage) evolution, cladogenetic (speciational) change, and geographic variation within species. 3. Maximum-likelihood parameter estimates suggested dominantly speciational change for only one or two shape traits, depending on model assumptions. For the remaining shape traits and body size, the contribution of anagenesis was always substantial. Confidence limits on these solutions were quite broad (though narrower when multiple traits were analyzed jointly), with most traits consistent with both strongly anagenetic and strongly cladogenetic change. 4. Whereas uncertainty about phylogenetic topology and species limits has little influence on the conclusions, assuming stasis instead of Brownian motion within lineages shifted support to solutions in which speciational change was more dominant, although several traits remained dominantly explained by anagenetic evolution. 5. These results suggest that for the traits and taxa examined, anagenesis contributes substantially to long-term divergence. The uncertainty in the results highlights the analytical difficulty of decomposing anagenetic and cladogenetic sources of phenotypic evolution, even with fossil constraints. When model uncertainty is taken into account, the task of doing so using observations from entirely extant populations is even more daunting.

opencc-zeroMay 2019View details →

Data from: Sexual selection and the evolution of male and female cognition: a test using experimental evolution in seed beetles

The mating system is thought to be important in shaping animal intelligence and sexual selection has been depicted as a driver of cognitive evolution, either directly by promoting superior cognitive ability during mate competition, or indirectly via genic capture of sexually selected traits. However, it remains unclear if intensified sexual selection leads to general improvements in cognitive abilities. Here, we evaluated this hypothesis by applying experimental evolution in seed beetles. Replicate lines, maintained for 35 generations of either enforced monogamy (eliminating sexual selection) or polygamy, were challenged to locate and discriminate among mates (male assays) or host seeds (female assays) in a spatial chemo-sensory learning task. All lines displayed learning between trials. Moreover, polygamous males outperformed monogamous males, providing evidence that sexual selection can lead to the evolution of improved male cognition. However, there were no differences between regimes in rates of male learning, and polygamous females showed no improvement in host search and even signs of reduced learning. Hence, sexual selection increased performance in cognitively demanding mate search, but it did not lead to general increases in cognitive abilities. We discuss the possibility that sexually antagonistic selection is an important factor maintaining abundant genetic variation in cognitive traits.

opencc-zeroDec 2013View details →

Data from: A new approach using high-resolution computed tomography to test the buoyant properties of chambered cephalopod shells

The chambered shell of modern cephalopods functions as a buoyancy apparatus, allowing the animal to enter the water column without expending a large amount of energy to overcome its own weight. Indeed, the chambered shell is largely considered a key adaptation that allowed the earliest cephalopods to leave the ocean floor and enter the water column. It has been argued by some, however, that the iconic chambered shell of Paleozoic and Mesozoic ammonoids did not provide a sufficiently buoyant force to compensate for the weight of the entire animal, thus restricting ammonoids to a largely benthic lifestyle reminiscent of some octopods. Here we develop a technique using high-resolution computed tomography to quantify the buoyant properties of chambered shells without reducing the shell to ideal spirals or eliminating inherent biological variability by using mathematical models that characterize past work in this area. This technique has been tested on Nautilus pompilius and is now extended to the extant deep-sea squid Spirula spirula and the Jurassic ammonite Cadoceras sp. hatchling. Cadoceras is found to have possessed near-neutral to positive buoyancy if hatched when the shell possessed between three and five chambers. However, we show that the animal could also overcome degrees of negative buoyancy through swimming, similar to the paralarvae of modern squids. These calculations challenge past inferences of benthic life habits based solely on calculations of negative buoyancy. The calculated buoyancy of Cadoceras supports the possibility of planktonic dispersal of ammonite hatchlings. This information is essential to understanding ammonoid ecology as well as biotic interactions and has implications for the interpretation of geochemical data gained from the isotopic analysis of the shell.

opencc-zeroDec 2013View details →

Data from: Testing models of speciation from genome sequences: divergence and asymmetric admixture in Island Southeast Asian Sus species during the Plio-Pleistocene climatic fluctuations

In many temperate regions, ice ages promoted range contractions into refugia resulting in divergence (and potentially speciation), while warmer periods led to range expansions and hybridization. However, the impact these climatic oscillations had in many parts of the tropics remains elusive. Here, we investigate this issue using genome sequences of three pig (Sus) species, two of which are found on islands of the Sunda-shelf shallow seas in Island Southeast Asia (ISEA). A previous study revealed signatures of inter-specific admixture between these Sus species (Frantz et al. (2013) Genome sequencing reveals fine scale diversification and reticulation history during speciation in Sus. Genome biology, 14, R107). However, the timing, directionality and extent of this admixture remain unknown. Here we use a likelihood based model comparison to more finely resolve this admixture history and test whether it was mediated by humans or occurred naturally. Our analyses suggest that inter-specific admixture between Sunda-shelf species was most likely asymmetric and occurred long before the arrival of humans in the region. More precisely, we show that these species diverged during the late Pliocene but around 23% of their genomes have been affected by admixture during the later Pleistocene climatic transition. In addition, we show that our method provides a significant improvement over D-statistics which are uninformative about the direction of admixture.

Data from: Direct-to-consumer DNA testing of 6,000 dogs reveals 98.6-kb duplication associated with blue eyes and heterochromia in Siberian Huskies

Consumer genomics enables genetic discovery on an unprecedented scale by linking very large databases of personal genomic data with phenotype information voluntarily submitted via web-based surveys. These databases are having a transformative effect on human genomics research, yielding insights on increasingly complex traits, behaviors, and disease by including many thousands of individuals in genome-wide association studies (GWAS). The promise of consumer genomic data is not limited to human research, however. Genomic tools for dogs are readily available, with hundreds of causal Mendelian variants already characterized, because selection and breeding have led to dramatic phenotypic diversity underlain by a simple genetic structure. Here, we report the results of the first consumer genomics study ever conducted in a non-human model: a GWAS of blue eyes based on more than 3,000 customer dogs with validation panels including nearly 3,000 more, the largest canine GWAS to date. We discovered a novel association with blue eyes on chromosome 18 (P = 1.3x10-68) and used both sequence coverage and microarray probe intensity data to identify the putative causal variant: a 98.6-kb duplication directly upstream of the Homeobox gene ALX4, which plays an important role in mammalian eye development. This duplication is largely restricted to Siberian Huskies, is strongly associated with the blue-eyed phenotype (chi-square P = 5.2x10-290), and is highly, but not completely, penetrant. These results underscore the power of consumer-data-driven discovery in non-human species, especially dogs, where there is intense owner interest in the personal genomic information of their pets, a high level of engagement with web-based surveys, and an underlying genetic architecture ideal for mapping studies.

Data from: An experimental test of the relationship between yolk testosterone and the social environment in a colonial passerine

Maternal hormones can be transferred to offspring during prenatal development in response to the maternal social environment, and may adaptively alter offspring phenotype. For example, numerous avian studies show that aggressive competition with conspecifics tends to result in females allocating more testosterone to their egg yolks, and this may cause offspring to have more competitive phenotypes. However, deviations from this pattern of maternal testosterone allocation are found, largely in studies of colonial species, and have yet to be explained. Colonial species may have different life-history constraints causing different yolk testosterone allocation strategies in response to conspecific competition, but few studies have experimentally tested whether colonial species do indeed differ from that of solitary species. To test this, we collected eggs from zebra finches (Taeniopygia guttata), a colonial species, in the presence and absence of conspecific intrusions. Females did not alter the concentration of testosterone deposited in eggs laid during intrusions despite becoming more aggressive. These results suggest that maternal effects are not characterized by a uniform response to the social environment, but rather need to be contextualized with life-history traits.

opencc-zeroDec 2014View details →

Data from: A test of genetic models for the evolutionary maintenance of same-sex sexual behaviour

The evolutionary maintenance of same-sex sexual behaviour (SSB) has received increasing attention because it is perceived to be an evolutionary paradox. The genetic basis of SSB is almost wholly unknown in non-human animals, though this is key to understanding its persistence. Recent theoretical work has yielded broadly applicable predictions centred on two genetic models for SSB: overdominance and sexual antagonism. Using Drosophila melanogaster, we assayed natural genetic variation for male SSB and empirically tested predictions about the mode of inheritance and fitness consequences of alleles influencing its expression. We screened 50 inbred lines derived from a wild population for male–male courtship and copulation behaviour, and examined crosses between the lines for evidence of overdominance and antagonistic fecundity selection. Consistent variation among lines revealed heritable genetic variation for SSB, but the nature of the genetic variation was complex. Phenotypic and fitness variation was consistent with expectations under overdominance, although predictions of the sexual antagonism model were also supported. We found an unexpected and strong paternal effect on the expression of SSB, suggesting possible Y-linkage of the trait. Our results inform evolutionary genetic mechanisms that might maintain low but persistently observed levels of male SSB in D. melanogaster, but highlight a need for broader taxonomic representation in studies of its evolutionary causes.

Data from: Aerobic power and flight capacity in birds: a phylogenetic test of the heart-size hypothesis

Flight capacity is one of the most important innovations in animal evolution; it only evolved in insects, birds, mammals and the extinct pterodactyls. Given that powered flight represents a demanding aerobic activity, an efficient cardiovascular system is essential for the continuous delivery of oxygen to the pectoral muscles during flight. It is well known that the limiting step in the circulation is stroke volume (the volume of blood pumped from the ventricle to the body during each beat), which is determined by the size of the ventricle. Thus, the fresh mass of the heart represents a simple and repeatable anatomic measure of aerobic power of an animal. Although several authors have already compared heart masses across bird species, a phylogenetic comparative analysis of these comparisons is still lacking. Compiling heart sizes for 915 species and applying several statistical procedures controlling for body size and/or testing for adaptive trends in the dataset (e.g., model selection approaches, phylogenetic generalized linear models), we found that (residuals of) heart sizes are consistently associated with four categories of flight capacity. In general, our results indicate that species exhibiting continuous hovering flight (i.e., hummingbirds) have substantially larger hearts than do other groups, that species that use flapping flight and gliding show intermediate values, and that species categorized as poor flyers show the smallest values. Our study shows that at a broad scale, routine flight modes seem to have shaped the energetic requirements of birds sufficiently to be anatomically detected at the comparative level.

Data from: All-trans retinoic acid disrupts development in ex vivo cultured fetal rat testes. II: modulation of mono-(2-ethylhexyl) phthalate toxicity

Humans are universally exposed to low levels of phthalate esters (phthalates), which are used to plasticize polyvinyl chloride. Phthalates exert adverse effects on the development of seminiferous cords in the fetal testis through unknown toxicity pathways. To investigate the hypothesis that phthalates alter seminiferous cord development by disrupting retinoic acid signaling in the fetal testis, gestational day 15 fetal rat testes were exposed for 1-3 days to 10-6 M all-trans retinoic acid (ATRA) alone or in combination with 10-6 to 10-4 M mono-(2-ethylhexyl) phthalate (MEHP) in ex vivo culture. As previously reported, exogenous ATRA reduced seminiferous cord number. This effect was attenuated in a concentration-dependent fashion by MEHP co-exposure. ATRA and MEHP-exposed testes were depleted of DDX4-positive germ cells but not Sertoli cells. MEHP alone enhanced the expression of the retinoic acid receptor target Rbp1 and the ovary development-associated genes Wnt4 and Nr0b1, and suppressed expression of the Leydig cell marker, Star, and the germ cell markers, Ddx4 and Pou5f1. In co-exposures, MEHP predominantly enhanced the gene expression effects of ATRA, but the Wnt4 and Nr0b1 concentration-responses were non-linear. Similarly, ATRA increased the number of cells expressing the granulosa cell marker FOXL2 in testis cultures, but this induction was attenuated by addition of MEHP. These results indicate that MEHP can both enhance and inhibit actions of ATRA during fetal testis development and provide evidence that retinoic acid signaling is a target for phthalate toxicity in the fetal testis.

opencc-zeroDec 2008View details →

Data from: Testing hypotheses of chaetognath origins: long branches revealed by 18S ribosomal DNA

Many hypotheses regarding the phylogenetic position of the Chaetognatha (arrow worms) have been proposed; these organisms are problematic primarily because their morphology offers few unambiguous systematic characters that ally them with other taxa. Early researchers proposed a plethora of phylogenetic placements for the Chaetognatha, grouping them with such divergent taxa as acanthocephalans and mollusks, but more traditional hypotheses posit that chaetognaths are, in fact, deuterostomes. Recently, Telford and Holland (1993, Mol. Biol. Evol. 10:660--676) and Wada and Satoh (1994, Proc. Natl. Acad. Sci. USA 91:1801--1804) disputed the deuterostome affinities of chaetognaths based on 18S nuclear ribosomal RNA (rDNA) gene sequence data. By employing published 18S rDNA gene sequence data, I extended these previous analyses by testing specific hypotheses of chaetognath affinities to nematodes, mollusks, acanthocephalans, and deuterostomes. Both parsimony and neighbor-joining analyses supported the monophyly of a chaetognath--nematode clade. Faith's T-PTP test and winning-sites analyses were employed to discriminate among competing hypotheses. The possibility of long-branch attraction accounting for the chaetognath--nematode relationship was explored by analyzing alternative four-taxon trees. An evolutionary scenario for the origin of the chaetognath lineage from a vermiform benthic organism is presented.

Data from: Low reversed cyclic loading tests for integrated precast structure of lightweight wall with single-row reinforcement under a lightweight steel frame

Given the development of precast structures for low-rise residential buildings, this study explores a new structure—namely, an integrated precast structure of lightweight recycled-concrete wall with single-row reinforcement—under a lightweight steel frame filled with recycled concrete (integrated precast structure for short). The lightweight steel frame and lightweight wall cooperate to bear the forces. The applied concealed bracing, either a rebar bracing or a steel plate bracing, increases the shear resistance of the wall. The lightweight steel frame is designed to bear the vertical loading, whereas the seismic load in the horizontal direction is jointly borne by the frame and wall. This study presents the results of low reversed cyclic loading tests on nine specimens of integrated precast structures. An analysis is then carried out to investigate the mechanical properties of the specimens; based on these results, a formula for the force-bearing performance of the inclined section is developed. The results show satisfactory performance as an integrated piece; the proposed structure has two seismic lines of defence, with the lightweight wall restraint by the side frame being the first line and the steel frame being the second line. Because the failure of the wall can be categorised as shear failure, the restraint of the lightweight steel frame significantly reduces the potential damage of the wall. As the beams and columns of the steel frame tend to bend against failure, the wall filling helps resist sliding. Therefore, the reinforced joints of the connecting beams and columns show no visible signs of damage, indicating that the connection between the beams and columns is reliable. The narrow spacing of rebars and the setting of concealed bracing contribute to the increase in ductility and energy efficiency and the evident reduction in the failure process. Furthermore, the recycled concrete increases the seismic resistance of the structure.

Data from: Modelling tooth–prey interactions in sharks: the importance of dynamic testing

The shape of shark teeth varies among species, but traditional testing protocols have revealed no predictive relationship between shark tooth morphology and performance. We developed a dynamic testing device to quantify cutting performance of teeth. We mimicked head-shaking behaviour in feeding large sharks by attaching teeth to the blade of a reciprocating power saw fixed in a custom-built frame. We tested three tooth types at biologically relevant speeds and found differences in tooth cutting ability and wear. Teeth from the bluntnose sixgill (Hexanchus griseus) showed poor cutting ability compared with tiger (Galeocerdo cuvier), sandbar (Carcharhinus plumbeus) and silky (C. falciformis) sharks, but they also showed no wear with repeated use. Some shark teeth are very sharp at the expense of quickly dulling, while others are less sharp but dull more slowly. This demonstrates that dynamic testing is vital to understanding the performance of shark teeth.

Data from: Colour as a backup for scent in the presence of olfactory noise: testing the efficacy backup hypothesis using bumblebees (Bombus terrestris)

The majority of floral displays simultaneously broadcast signals from multiple sensory modalities, but these multimodal displays come at both a metabolic cost and an increased conspicuousness to floral antagonists. Why then do plants invest in these costly multimodal displays? The efficacy backup hypothesis suggests that individual signal components act as a backup for others in the presence of environmental variability. Here, we test the efficacy backup hypothesis by investigating the ability of bumblebees to differentiate between sets of artificial flowers in the presence of either chemical interference or high wind speeds, both of which have the potential to impede the transmission of olfactory signals. We found that both chemical interference and high wind speeds negatively affected forager learning times, but these effects were mitigated in the presence of a visual signal component. Our results suggest that visual signals can act as a backup for olfactory signals in the presence of chemical interference and high wind speeds, and support the efficacy backup hypothesis as an explanation for the evolution of multimodal floral displays.

opencc-zeroMay 2019View details →

Data from: Effect of detection heterogeneity in occupancy-detection models: an experimental test of time-to-first-detection methods

Imperfect detection can bias estimates of site occupancy in ecological surveys but can be corrected by estimating detection probability. Time-to-first-detection (TTD) occupancy models have been proposed as a cost-effective survey method that allows detection probability to be estimated from single site visits. Nevertheless, few studies have validated the performance of occupancy-detection models by creating a situation where occupancy is known, and model outputs can be compared with the truth. We tested the performance of TTD occupancy models in the face of detection heterogeneity using an experiment based on standard survey methods to monitor koala (Phascolarctos cinereus) populations in Australia. Known numbers of koala faecal pellets were placed under trees, and observers, uninformed as to which trees had pellets under them, carried out a TTD survey. We fitted five TTD occupancy models to the survey data, each making different assumptions about detectability, to evaluate how well each estimated the true occupancy status. Relative to the truth, all five models produced strongly biased estimates, overestimating detection probability and underestimating the number of occupied trees. Despite this, goodness-of-fit tests indicated that some models fitted the data well, with no evidence of model misfit. Hence, TTD occupancy models that appear to perform well with respect to the available data may be performing poorly. The reason for poor model performance was unaccounted for heterogeneity in detection probability, which is known to bias occupancy-detection models. This poses a problem because unaccounted for heterogeneity could not be detected using goodness-of-fit tests and was only revealed because we knew the experimentally determined outcome. A challenge for occupancy-detection models is to find ways to identify and mitigate the impacts of unobserved heterogeneity, which could unknowingly bias many models.

Data from: Comparison of target-capture and restriction-site associated DNA sequencing for phylogenomics: a test in cardinalid tanagers (Aves, genus: Piranga)

Restriction-site associated DNA sequencing (RAD-seq) and target capture of specific genomic regions, such as ultraconserved elements (UCEs), are emerging as two of the most popular methods for phylogenomics using reduced-representation genomic datasets. These two methods were designed to target different evolutionary timescales: RAD-seq was designed for population-genomic level questions and UCEs for deeper phylogenetics. The utility of both datasets to infer phylogenies across a variety of taxonomic levels has not been adequately compared within the same taxonomic system. Additionally, the effects of uninformative gene trees on species tree analyses (for target capture data) have not been explored. Here, we utilize RAD-seq and UCE data to infer a phylogeny of the bird genus Piranga. The group has a range of divergence dates (0.5 my – 6 my), contains eleven recognized species, and lacks a resolved phylogeny. We compared two species tree methods for the RAD-seq data and six species tree methods for the UCE data. Additionally, in the UCE data, we analyzed a complete matrix as well as datasets with only highly informative loci. A complete matrix of 189 UCE loci with ten or more parsimony informative (PI) sites, and an ~80% complete matrix of 1128 PI SNPs (from RAD-seq) yield the same fully resolved phylogeny of Piranga. We inferred non-monophyletic relationships of P. lutea individuals, with all other a priori species identified as monophyletic. Finally, we found that species tree analyses that included predominantly uninformative gene trees provided strong support for different topologies, with consistent phylogenetic results when limiting species tree analyses to highly informative loci or only using less informative loci with concatenation or methods meant for SNPs alone.

Data from: Asynchronous hatching in a non-avian species: a test of the hurry-up hypothesis

The hurry-up hypothesis suggests that completing reproduction as soon as possible is favoured when the quantity or quality of resources used for breeding declines over time. However, completing reproduction sooner may incur a cost if it leads to an asynchronous hatching pattern that reduces overall growth and survival of offspring. Here, we present the first test of the hurry-up hypothesis in a non-avian system, the burying beetle Nicrophorus vespilloides, which breeds on small vertebrate carcasses. To this end, we conducted two experiments in which we provided females with an incentive to complete reproduction sooner by giving them carcasses that varied either with respect to decomposition (decomposed or fresh) or size. We recorded the delay until laying, and measures of the laying pattern and fitness consequences for the offspring. As predicted, we found that larvae dispersed from the carcass earlier when females commenced oviposition sooner and that laying spread was greater when females commenced egg laying earlier. However, we found no evidence that females commenced egg laying earlier on either decomposed or larger carcasses. Our results suggest that, although asynchronous hatching might emerge as a by-product of parents attempting to complete reproduction sooner, there is no evidence that females attempt to complete reproduction sooner under conditions where this would be favourable. Our results are therefore inconsistent with the hurry-up hypothesis.

Data from: Testing the Münch hypothesis of long distance phloem transport in plants

Long distance transport in plants occurs in sieve tubes of the phloem. The pressure flow hypothesis introduced by Ernst Münch in 1930 describes a mechanism of osmotically generated pressure differentials that are supposed to drive the movement of sugars and other solutes in the phloem, but this hypothesis has long faced major challenges. The key issue is whether the conductance of sieve tubes, including sieve plate pores, is sufficient to allow pressure flow. We show that with increasing distance between source and sink, sieve tube conductivity and turgor increases dramatically in Ipomoea nil. Our results provide strong support for the Münch hypothesis, while providing new tools for the investigation of one of the least understood plant tissues.