Measuring Ucrit and endurance: equipment choice influences estimates of fish swimming performance

This study compared the critical swimming speed (U_crit) and endurance performance of three Australian freshwater fish species in different swim‐test apparatus. Estimates of U_crit measured in a large recirculating flume were greater for all species compared with estimates from a smaller model of the same recirculating flume. Large differences were also observed for estimates of endurance swimming performance between these recirculating flumes and a free‐surface swim tunnel. Differences in estimates of performance may be attributable to variation in flow conditions within different types of swim chambers. Variation in estimates of swimming performance between different types of flumes complicates the application of laboratory‐based measures to the design of fish passage infrastructure.     

Repeated evolution of local adaptation in swimming performance: population‐level trade‐offs between burst and endurance swimming in Brachyrhaphis freshwater fish

Specialization is fundamentally important in biology because specialized traits allow species to expand into new environments, in turn promoting population differentiation and speciation. Specialization often results in trade‐offs between traits that maximize fitness in one environment but not others. Despite the ubiquity of trade‐offs, we know relatively little about how consistently trade‐offs evolve between populations when multiple sets of populations experience similarly divergent selective regimes. In the present study, we report a case study on Brachyrhaphis fishes from different predation environments. We evaluate apparent within/between population trade‐offs in burst‐speed and endurance at two levels of evolutionary diversification: high‐ and low‐predation populations of Brachyrhaphis rhabdophora, and sister species Brachyrhaphis roseni and Brachyrhaphis terrabensis, which occur in high‐ and low‐predation environments, respectively. Populations of Brachyrhaphis experiencing different predation regimes consistently evolved swimming specializations indicative of a trade‐off between two swimming forms that are likely highly adaptive in the environment in which they occur. We show that populations have become similarly locally adapted at both levels of diversification, suggesting that swimming specialization has evolved rather rapidly and persisted post‐speciation. Our findings provide valuable insight into how local adaptation evolves at different stages of evolutionary divergence.     

Sex‐specific growth in chicks of the sexually dimorphic Black‐tailed Godwit

Sexual size dimorphism (SSD) is common in birds and has been linked to various selective forces. Nevertheless, the question of how and when the sexes start to differentiate from each other is poorly studied. This is a critical knowledge gap, as sex differences in growth may cause different responses to similar ecological conditions. In this study, we describe the sex‐specific growth – based on body mass and five morphometric measurements – of 56 captive Black‐tailed Godwit Limosa limosa limosa chicks raised under ad libitum food conditions, and conclude that all six growth curves are sex‐specific. Females are the larger sex in terms of body mass and skeletal body size. To test whether sex‐specific growth leads to sex‐specific susceptibility to environmental conditions, we compared the age‐specific sizes of male and female chicks in the wild with those of Black‐tailed Godwits reared in captivity. We then tested for a relationship between residual growth and relative hatching date, age, sex and habitat type in which the wild chicks were born. Early‐hatched chicks were relatively bigger and in better condition than late‐hatched chicks, but body condition and size were not affected by natal habitat type. Female chicks deviated more negatively from the sex‐specific growth curves than male chicks for body mass and total‐head length. This suggests that the growth of the larger females is more susceptible to limiting environmental conditions. On average, the deviations of wild chicks from the predicted growth curves were negative for all measurements, which suggests that conditions are limiting in the current agricultural landscape. We argue that in estimating growth curves for sexually dimorphic species, it is critical first to make accurate sex and age determinations.     

The effect of substratum type on aspects of swimming performance and behaviour in shortnose sturgeon Acipenser brevirostrum

The swimming performance and associated swimming behaviour (i.e. substratum‐skimming, station‐holding and free swimming) were assessed in shortnose sturgeon Acipenser brevirostrum during critical swimming and endurance swimming tests over a rough and a smooth substratum. It was hypothesized that the addition of a rough substratum in the swimming flume may provide a surface for the A. brevirostrum to grip and offer an energetic advantage. Substratum type did not affect the critical swimming performance, but A. brevirostrum consistently performed more bottom behaviours (i.e. substratum‐skimming and station‐holding) while on a smooth substratum. Acipenser brevirostrum had little contact with the rough substratum until the velocity was >1 body length s^?1. Endurance swimming time was significantly lower for A. brevirostrum over the rough bottom at the highest velocity (30 cm s^?1) which may be attributed to the observed increase in free swimming and decrease in bottom behaviours. During endurance swimming, the rough substratum was mainly used at intermediate velocities, suggesting that there may be a stability cost associated with being in contact with the rough substratum at certain velocities.     

Ornamental evolution in Trinidadian guppies (Poecilia reticulata): insights from sensory processing‐based analyses of entire colour patterns

The evolution of exaggerated sexual ornamentation is classically thought to proceed as a compromise between opposing vectors of sexual and natural selection. In colour‐based ornamentation, as exhibited by guppies (Poecilia reticulata), heightened trait expression may be beneficial in promoting attractiveness, but costly in terms of predation. Opportunities to reconcile this compromise will exist if there are differences between conspecifics and predators in their sensory systems; in such situations guppies should evolve to exploit the ways in which their ornamentation would appear maximally conspicuous to conspecifics. In the present study, we addressed this hypothesis via a study of geographic variation employing the most sophisticated colour analysis yet attempted for Trinidadian guppies. We made two paired contrasts, one between two Aripo populations that vary in the presence of the potential predator Aequidens pulcher, and another between Quare and Marianne populations that vary in exposure to a predatory prawn, Macrobrachium crenulatum. We predicted that, if ornamentation is constrained by the presence of either predator, then guppy conspicuousness should change most markedly across each of the two paired populations as viewed by that predator. Although disparity analysis of entire colour patterns indicated significant differences in both contrasts, this prediction was most clearly supported for the Marianne/Quare contrast. Marianne fish, which co‐exist with prawns, exhibited larger black spots coupled with less extensive, less bright flank iridescence. The brightness reductions are notable because, as the only potential guppy predator with a dedicated ultraviolet (UV) photoreceptor, prawns may detect passing male guppies via their UV‐bright blues, violets and ‘UV/oranges’. We discuss our findings in light of the additional insights that might be obtained by combining spectral assessments and visual modeling with more traditional methods of colour pattern appraisal. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 734–747.     

Sex‐specific compensatory growth in the larvae of the greater wax moth Galleria mellonella

Deficiency of food resources in ontogeny is known to prolong an organism's developmental time and affect body size in adulthood. Yet life‐history traits are plastic: an organism can increase its growth rate to compensate for a period of slow growth, a phenomenon known as ‘compensatory growth’. We tested whether larvae of the greater wax moth Galleria mellonella can accelerate their growth after a fast of 12, 24 or 72 h. We found that a subgroup of female larvae showed compensatory growth when starved for 12 h. Food deficiency lasting more than 12 h resulted in longer development and lower mass gain. Strength of encapsulation reactions against a foreign body inserted in haemocoel was the weakest in females that showed compensatory growth, whereas the strongest encapsulation was recorded in the males and females that fasted for 24 and 72 h. More specifically, we found sex‐biased immune reactions so that females had stronger encapsulation rates than males in one group that fasted for 72 h. Overall, rapidly growing females had a short larval development period and the shortest adult lifespan. These results suggest that highly dynamic trade‐offs between the environment, life‐history traits and sex lead to plasticity in developmental strategies/growth rates in the greater wax moth.     

Sex-biased genetic component distribution among populations: additive genetic and maternal contributions to phenotypic differences among populations of Chinook salmon

An approach frequently used to demonstrate a genetic basis for population-level phenotypic differences is to employ common garden rearing designs, where observed differences are assumed to be attributable to primarily additive genetic effects. Here, in two common garden experiments, we employed factorial breeding designs between wild and domestic, and among wild populations of Chinook salmon (Oncorhynchus tshawytscha). We measured the contribution of additive (V(A)) and maternal (V(M)) effects to the observed population differences for 17 life history and fitness-related traits. Our results show that, in general, maternal effects contribute more to phenotypic differences among populations than additive genetic effects. These results suggest that maternal effects are important in population phenotypic differentiation and also signify that the inclusion of the maternal source of variation is critical when employing models to test population differences in salmon, such as in local adaptation studies.     

Survival selection on escape performance and its underlying phenotypic traits: a case of many‐to‐one mapping

Selection often operates not directly on phenotypic traits but on performance which is important as several traits may contribute to a single performance measure (many‐to‐one mapping). Although largely ignored in the context of selection, this asks for studies that link all relevant phenotypes with performance and fitness. In an enclosure experiment, we studied links between phenotypic traits, swimming performance and survival in two Enallagma damselflies. Predatory dragonflies imposed survival selection for increased swimming propensity and speed only in E. annexum; probably E. aspersum was buffered by the former species’ presence. Accordingly, more circular caudal lamellae, structures involved in generating thrust while swimming, were selected for only in E. annexum. Other phenotypic traits that contributed to swimming speed were apparently not under selection, probably because of many‐to‐one mapping (functional redundancy). Our results indicate that not only the phenotypic distributions of syntopic prey organisms but also many‐to‐one mapping should be considered when documenting phenotype–performance–fitness relationships.     

Local genetic adaptation generates latitude‐specific effects of warming on predator–prey interactions

Temperature effects on predator–prey interactions are fundamental to better understand the effects of global warming. Previous studies never considered local adaptation of both predators and prey at different latitudes, and ignored the novel population combinations of the same predator–prey species system that may arise because of northward dispersal. We set up a common garden warming experiment to study predator–prey interactions between Ischnura elegans damselfly predators and Daphnia magna zooplankton prey from three source latitudes spanning >1500 km. Damselfly foraging rates showed thermal plasticity and strong latitudinal differences consistent with adaptation to local time constraints. Relative survival was higher at 24 °C than at 20 °C in southern Daphnia and higher at 20 °C than at 24 °C, in northern Daphnia indicating local thermal adaptation of the Daphnia prey. Yet, this thermal advantage disappeared when they were confronted with the damselfly predators of the same latitude, reflecting also a signal of local thermal adaptation in the damselfly predators. Our results further suggest the invasion success of northward moving predators as well as prey to be latitude‐specific. We advocate the novel common garden experimental approach using predators and prey obtained from natural temperature gradients spanning the predicted temperature increase in the northern populations as a powerful approach to gain mechanistic insights into how community modules will be affected by global warming. It can be used as a space‐for‐time substitution to inform how predator–prey interaction may gradually evolve to long‐term warming.     

Sex‐specific pathways of parental age effects on offspring lifetime reproductive success in a long‐lived seabird

The conditions under which individuals are reared vary and sensitivity of offspring to such variation is often sex‐dependent. Parental age is one important natal condition with consequences for aspects of offspring fitness, but reports are mostly limited to short‐term fitness consequences and do not take into account offspring sex. Here we used individual‐based data from a large colony of a long‐lived seabird, the common tern Sterna hirundo, to investigate longitudinal long‐term fitness consequences of parental age in relation to both offspring and parental sex. We found that recruited daughters from older mothers suffered from reduced annual reproductive success. Recruited sons from older fathers were found to suffer from reduced life span. Both effects translated to reductions in offspring lifetime reproductive success. Besides revealing novel sex‐specific pathways of transgenerational parental age effects on offspring fitness, which inspire studies of potential underlying mechanisms, our analyses show that reproductive senescence is only observed in the common tern when including transgenerational age effects. In general, our study shows that estimates of selective pressures underlying the evolution of senescence, as well as processes such as age‐dependent mate choice and sex allocation, will depend on whether causal transgenerational effects exist and are taken into account.     

Community‐level plant–soil feedbacks explain landscape distribution of native and non‐native plants

Plant–soil feedbacks (PSFs) have gained attention for their potential role in explaining plant growth and invasion. While promising, most PSF research has measured plant monoculture growth on different soils in short‐term, greenhouse experiments. Here, five soil types were conditioned by growing one native species, three non‐native species, or a mixed plant community in different plots in a common‐garden experiment. After 4 years, plants were removed and one native and one non‐native plant community were planted into replicate plots of each soil type. After three additional years, the percentage cover of each of the three target species in each community was measured. These data were used to parameterize a plant community growth model. Model predictions were compared to native and non‐native abundance on the landscape. Native community cover was lowest on soil conditioned by the dominant non‐native, Centaurea diffusa, and non‐native community cover was lowest on soil cultivated by the dominant native, Pseudoroegneria spicata. Consistent with plant growth on the landscape, the plant growth model predicted that the positive PSFs observed in the common‐garden experiment would result in two distinct communities on the landscape: a native plant community on native soils and a non‐native plant community on non‐native soils. In contrast, when PSF effects were removed, the model predicted that non‐native plants would dominate all soils, which was not consistent with plant growth on the landscape. Results provide an example where PSF effects were large enough to change the rank‐order abundance of native and non‐native plant communities and to explain plant distributions on the landscape. The positive PSFs that contributed to this effect reflected the ability of the two dominant plant species to suppress each other's growth. Results suggest that plant dominance, at least in this system, reflects the ability of a species to suppress the growth of dominant competitors through soil‐mediated effects.     

Prenatal exposure to dexamethasone in the mouse induces sex‐specific differences in placental gene expression

Prenatal stress during pregnancy leads to sex‐specific effects on fetal development and disease susceptibility over the life span; however, the origin of sex differences has not been identified. The placenta not only plays a key role in fetal growth and development throughout pregnancy, but also affects the fetal programming underlying subsequent adult health and accounts. Therefore, sex‐specific adaptation of the placenta may be central to the sex differences in fetal growth and survival. Here, we analyzed the effects of prenatal dexamethasone (Dex) on sex‐specific changes in placental gene expression using RNA‐Seq. Placental tissues from males and females were separated into two developmentally distinct fetal and maternal parts at E11.5 stage. The majority of genes in female placentas were downregulated by prenatal Dex, whereas those were mostly maintained or rather upregulated in male placentas. RNA‐Seq results were validated using independent biological replicates from the same stage and placental tissue samples from E18.5 by realtime PCR assays. Activation of various inflammatory response‐related genes, chemokines and their receptors, particularly in male placentas, strongly implies that prenatal Dex exposure causes sex‐specific physiological responses that can lead to inflammatory diseases involving vascular pathology.     

Sex‐specific prey partitioning in breeding piscivorous birds examined via a novel,noninvasive approach

Piscivorous birds frequently display sex‐specific differences in their hunting and feeding behavior, which lead to diverging impacts on prey populations. Cormorants (Phalacrocoracidae), for example, were previously studied to examine dietary differences between the sexes and males were found to consume larger fish in coastal areas during autumn and winter. However, information on prey partitioning during breeding and generally on sex‐specific foraging in inland waters is missing. Here, we assess sex‐specific prey choice of Great Cormorants (Phalacrocorax carbo) during two subsequent breeding seasons in the Central European Alpine foreland, an area characterized by numerous stagnant and flowing waters in close proximity to each other. We developed a unique, noninvasive approach and applied it to regurgitated pellets: molecular cormorant sexing combined with molecular fish identification and fish‐length regression analysis performed on prey hard parts. Altogether, 364 pellets delivered information on both, bird sex, and consumed prey. The sexes differed significantly in their overall prey composition, even though Perca fluviatilis, Rutilus rutilus, and Coregonus spp. represented the main food source for both. Albeit prey composition did not indicate the use of different water bodies by the sexes, male diet was characterized by higher prey diversity within a pellet and the consumption of larger fish. The current findings show that female and male cormorants to some extent target the available prey spectrum at different levels. Finally, the comprehensive and noninvasive approach has great potential for application in studies of other piscivorous bird species.     

Reproductive fitness consequences of progenesis: Sex‐specific pay‐offs in safe and risky environments

Progenesis is considered to have an important role in evolution because it allows the retention of both a larval body size and shape in an adult morphology. However, the cost caused by the adoption of a progenetic process in both males and females remains to be explored to explain the success of progenesis and particularly its biased prevalence across the sexes and environments. Here, through an experimental approach, we used a facultative progenetic species, the palmate newt (Lissotriton helveticus) that can either mature at a small size and retain gills or mature after metamorphosis, to test three hypotheses for sex‐specific pay‐offs of progenesis in safe versus risky habitats. Goldfish were used because they caused a higher decline in progenetic than metamorphic newts. We determined that progenetic newts have a lower reproductive fitness than metamorphic newts. We also found that, when compared to metamorphs, progenetic males have lower reproductive activity than progenetic females and that predatory risk affects more progenetic than metamorphic newts. By identifying ultimate causes of the female‐biased sex ratios found in nature, these results support the male escape hypothesis, that is the higher metamorphosis rate of progenetic males. They also highlight that although progenesis is advantageous in advancing the age at first reproduction, it also brings an immediate fitness cost and this, particularly, in hostile predatory environments. This means that whereas some environmental constraints could favour facultative progenesis, some others, such as predation, can ultimately counter‐select progenesis. Altogether, these results improve our understanding of how developmental processes can affect the sexes differently and how species invasions can impair the success of alternative developmental phenotypes.     

Sex‐specific distribution and diet of Platichthys flesus at the end of spawning in the northern Baltic Sea

This study examined the relationship of seascape structure, prey availability and sex on the post‐spawning distribution and diet of European flounder Platichthys flesus in the northern Baltic Sea. The objectives were to determine whether: (1) wave exposure and substratum affect abundance and distribution of P. flesus, (2) diet reflects the benthic prey composition and (3) sex affects the distribution or diet of P. flesus. The results showed that P. flesus was evenly spread in the archipelago with no correlation to wave exposure. The distribution was, however, sex specific; reproductive males dominated the exposed zone and mainly post‐reproductive females dominated the intermediate and sheltered zones. Platichthys flesus fed mainly on two bivalve prey species: blue mussels Mytilus edulis and Baltic tellins Macoma balthica. Hard substratum invertebrates dominated the diet in all habitats and apart from some typical soft substratum species, there was no clear link between fish feeding and the dominance structure of benthic prey. Diet was further sex specific, with females showing a broader range of diet than males. Results suggest that P. flesus is a specialist molluscivore found commonly and equally in soft‐ and hard‐substratum habitats throughout the archipelago area. Previous studies on P. flesus in the Baltic Sea have yielded inconsistent results regarding diet and it has commonly been believed that the distribution of Baltic Sea P. flesus is linked to sand and soft substrata. The present findings emphasize the importance of including the entire range of habitats when diet and regional species distributions are assessed.     

Species‐specific physiological response of dinoflagellates to quantified small‐scale turbulence1

Turbulence has been shown to alter different aspects of the physiology of some dinoflagellates. The response appears to be species‐specific and dependent on the experimental design and setup used to generate small‐scale turbulence. We examined the variability of the response of three dinoflagellate species to the turbulence, following the same experimental design used by Berdalet (1992) on Akashiwo sanguinea (Hirasaka) Ge. Hansen et Moestrup (=Gymnodinium nelsonii G. W. Martin). In all experiments, turbulence was generated by an orbital shaker at 100 rpm, which corresponded on bulk average, to dissipation rates (ε, quantified using an acoustic Doppler velocimeter) of ≈2 cm² · s^?3. Turbulence did not appreciably affect Gymnodinium sp., a small dinoflagellate. However, Alexandrium minutum Halim and Prorocentrum triestinum J. Schiller exhibited a reduced net growth rate (33% and 28%, respectively) when shaken during the exponential growth phase. Compared to the still cultures, the shaken treatments of A. minutum and P. triestinum increased the mean cell volume (up to 1.4‐ and 2.5‐fold, respectively) and the mean DNA content (up to 1.8‐ and 5.3‐fold, respectively). Cultures affected by turbulence recovered their normal cell properties when returned to still conditions. The swimming speed of the cells exposed to agitation was half that of the unshaken ones. Overall, the response of A. minutum and P. triestinum was similar, but with lower intensity, to that observed previously on A. sanguinea. We found no clear trends related to taxonomy or morphology.     

The relative importance of plasticity versus genetic differentiation in explaining between population differences; a meta‐analysis

Both plasticity and genetic differentiation can contribute to phenotypic differences between populations. Using data on non‐fitness traits from reciprocal transplant studies, we show that approximately 60% of traits exhibit co‐gradient variation whereby genetic differences and plasticity‐induced differences between populations are the same sign. In these cases, plasticity is about twice as important as genetic differentiation in explaining phenotypic divergence. In contrast to fitness traits, the amount of genotype by environment interaction is small. Of the 40% of traits that exhibit counter‐gradient variation the majority seem to be hyperplastic whereby non‐native individuals express phenotypes that exceed those of native individuals. In about 20% of cases plasticity causes non‐native phenotypes to diverge from the native phenotype to a greater extent than if plasticity was absent, consistent with maladaptive plasticity. The degree to which genetic differentiation versus plasticity can explain phenotypic divergence varies a lot between species, but our proxies for motility and migration explain little of this variation.     

Inter‐specific differences in invader and native fish functional responses illustrate neutral effects on prey but superior invader competitive ability

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The 1st step initiation essential for allergen‐specific IgE antibody production upon the 2nd step: Induction of non‐specific IgE+ small B cells containing secondly‐sensitized allergen‐specific ones in mice firstly‐sensitized with an allergen

There was a significant amount of non‐specific, but not of allergen (e.g., papain, mite feces and four kinds of pollen)‐specific, IgE antibodies (Abs) in the sera of normal mice. An i.n. injection of each allergen without adjuvant into mice caused an increase in total IgE Ab titers with a similar time course in the serum. However, the stage of initiation of allergy varied from allergen to allergen. Submandibular lymph node cells from normal mice contained papain‐, but not mite feces‐ or pollen‐specific IgE⁺ cells and an i.n. injection of papain induced papain‐specific IgE Abs in the serum. In contrast, one (i.n.) or two (i.n. and s.c) injections of mite feces induced neither mite feces‐specific IgE⁺ cells in the lymph nodes nor mite feces‐specific IgE Abs in the serum. I.n. sensitization with cedar pollen induced cedar pollen‐specific IgE⁺ small B cells in the lymph nodes on Day 10, when non‐specific IgE Ab titers reached a peak in the serum, implying induction of related allergen‐specific IgE⁺ small cells as well. In fact, a second (s.c.) injection of ragweed (or cedar) pollen into mice sensitized i.n. once with cedar (or ragweed) pollen, but not with mite feces, induced a large amount of ragweed (or cedar) pollen‐specific IgE Abs in the serum. These results indicate that when firstly‐sensitized non‐specific IgE⁺ small B cells in mouse lymph nodes include some secondly‐sensitized allergen‐specific ones, mice produce IgE Abs specific for the secondly‐injected allergen.