Bart Pollux
Wageningen University and Research Centre, Experimental Zoology, Faculty Member
- Evolutionary biologist interested in the evolution of biological complexity with a passion for fishedit
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Research Interests: Zoology, Biology, Ecology, Medicine, Reproductive Success, and 3 moreOecologia, Infestation, and Offspring
In dit artikel wordt de verspreiding van de Bittervoorn (Rhodeus sericeus amarus Bloch 1782) in 15 uiterwaardplassen langs de Maas in Noord-Limburg beschreven. Deze werden gedurende de jaren 2010 en 2011 vijfmaal bemonsterd. De... more
In dit artikel wordt de verspreiding van de Bittervoorn (Rhodeus sericeus amarus Bloch 1782) in 15 uiterwaardplassen langs de Maas in Noord-Limburg beschreven. Deze werden gedurende de jaren 2010 en 2011 vijfmaal bemonsterd. De Bittervoorn is in tien van de 15 plassen aangetroffen. In negen ervan zijn tijdens schepnetbemonsteringen ook grote zoetwatermosselen opgeschept, wat doet vermoeden dat deze algemeen in de uiterwaarden voorkomen. De aanwezigheid van zoetwatermosselen is, door de unieke paarsymbiose tussen beide soorten, een voorwaarde voor succesvolle voortplanting van de Bittervoorn. Op basis van vangsten van kleine pas uit het ei gekomen vissen blijkt dat de Bittervoorn zich in 2011 in vijf uiterwaardplassen heeft voortgeplant. Tot slot wordt inzichtelijk gemaakt dat de Bittervoornpopulaties in de uiterwaarden een aantal kenmerken vertonen die karakteristiek zijn voor een metapopulatie.
Research Interests: Humanities and Art
Background: The evolution of complex organs is thought to occur via a stepwise process, each subsequent step increasing the organ’s complexity by a tiny amount. Studying this process requires closely related species that vary in the... more
Background: The evolution of complex organs is thought to occur via a stepwise process, each subsequent step increasing the organ’s complexity by a tiny amount. Studying this process requires closely related species that vary in the complexity of their organs. This is the case for the placenta in the livebearing fish family Poeciliidae, as members of this family vary markedly in their placental complexity. Here, we look for the genomic basis underlying this phenotypic variation in the genome of Heterandria formosa, a poeciliid fish with a highly complex placenta. We compare this genome to three published reference genomes of non-placental poeciliid fish to gain insight in which genes play a role in the evolution of the placenta in the Poeciliidae. Results: We sequenced the genome of H. formosa, providing the first whole genome sequence information of a placental poeciliid. We looked for signatures of adaptive evolution by comparing its gene sequences to those of three non-placental live-bearing relatives. We found 18 positively selected genes exclusive to H. formosa, as well as 5 gene duplications. Eight of the genes evolving under positive selection in H. formosa have a placental function in mammals, most notably endometrial tissue remodelling or endometrial cell proliferation. Conclusions: Our results show that a substantial portion of positively selected genes have a function that correlates well with the morphological changes that form the placenta of H. formosa, compared to the corresponding tissue in non-placental poeciliids. These functions are mainly endometrial tissue remodelling and endometrial cell proliferation. Therefore, we hypothesize that natural selection acting on genes involved in these functions plays a key role in the evolution of the placenta in H. formosa.
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Research Interests: Freshwater Biology, Biology, Seed Dispersal, Experimental Design, Biological Sciences, and 13 moreEnvironmental Sciences, Standardisation, Experimental Study, Intraspecific Variation, Germination, Digestive Tract, Ingestion, Plant species, Intraspecific Competition, Chemical Composition, Retention Time, Hard Anodizing Coating, and Area of Interest
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Dispersal of seeds by animals is an important mechanism regulating plant diversity, range expansions and invasions. Many birds, mammals, fish, and reptiles regularly ingest, transport and excrete viable seeds (known as endozoochory). The... more
Dispersal of seeds by animals is an important mechanism regulating plant diversity, range expansions and invasions. Many birds, mammals, fish, and reptiles regularly ingest, transport and excrete viable seeds (known as endozoochory). The effectiveness of endozoochory is modelled in dispersal kernels: functions that describe seed shadows in the landscape by combining movement of animals with experimentally obtained seed retention times and survival. Currently, dispersal kernels use experimental data from resting animals, yet only moving animals disperse seeds. Although physical activity is known to affect digestive processes, little is known on how and to what extent this may influence current estimates of endozoochory. Activity may either prolong seed retention in the animal's gut (locomotion-priority mode hypothesis) or may not affect seed excretion rate (digestion-priority mode hypothesis), and may affect seed survival and germination positively or negatively. We tested how activity alters dispersal estimates in fish. We compared the seed dispersal potential of two riparian plant species (Carex acuta and C. riparia) by the common carp (Cyprinus carpio) subjected to three different activity levels: low (basal metabolic rate, BMR), medium (2×BMR), or high activity (3×BMR). Physical activity of the fish did not affect the number of intact retrieved seeds over 15 h of activity, but significantly affected seed retrieval patterns over time for both seed species. More active fish started seed excretion about 1 h later and kept excreting seeds at least 2 h longer. Effects of gut passage on germination could only be tested for C. acuta, where it reduced the percentage of germinating seeds by 22%, independent of the activity level. Seeds ingested by the fish germinated on average 3.5 days later than non-ingested control seeds. Seed retention times did not affect the timing of germination. Our results support the locomotion-priority mode hypothesis, and show that modelling dispersal kernels using parameters from inactive fish may underestimate potential dispersal distances. Because a trade-off between physical activity and digestive physiology is likely common in animals, it should be taken into account in future modelling of endozoochorous seed dispersal kernels
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Research Interests: Demography, Aquatic Ecology, Gene Flow, Biology, Ecology, and 15 moreMedicine, Genetic Diversity, Biological Sciences, Molecular, Germany, Aquatic Macrophytes, Genetic Differentiation, Angiosperms, Environmental Conditions, Asexual Reproduction, Genetic variation, Bayes Theorem, Environment, Genotypic diversity, and Gene frequency
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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,... more
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.
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In live-bearing animal lineages, the evolution of the placenta is predicted to create an arena for genomic conflict during pregnancy, drive patterns of male sexual selection, and increase the rate of speciation. Here we test these... more
In live-bearing animal lineages, the evolution of the placenta is predicted to create an arena for genomic conflict during pregnancy, drive patterns of male sexual selection, and increase the rate of speciation. Here we test these predictions of the viviparity driven conflict hypothesis (VDCH) in live-bearing poecilid fishes, a group showing multiple independent origins of placentation and extreme variation in male sexually selected traits. As predicted, male sexually selected traits are only gained in lineages that lack placentas; while there is little or no influence of male traits on the evolution of placentas. Both results are consistent with the mode of female provisioning governing the evolution of male attributes. Moreover, it is the presence of male sexually selected traits (pre-copulatory), rather than placentation (post-copulatory), that are associated with higher rates of speciation. These results highlight a causal interaction between female reproductive mode, male sexual selection and the rate of speciation, suggesting a role for conflict in shaping diverse aspects of organismal biology
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Swimming performance of pregnant live-bearing fish is presumably constrained by the additional drag associated with the reproductive burden. Yet, it is still unclear how and to what extent the reproductive investment affects body drag of... more
Swimming performance of pregnant live-bearing fish is presumably constrained by the additional drag associated with the reproductive burden. Yet, it is still unclear how and to what extent the reproductive investment affects body drag of the females. We examined the effect of different levels of reproductive investment on body drag. The biggest measured increase in body volume due to pregnancy was about 43%, linked to a wetted area increase of about 16% and 69% for the frontal area. We printed three-dimensional models of live-bearing fish in a straight body posture representing different reproductive allocation (RA) levels. We measured the drag and visualized the flow around these models in a flow tunnel at different speeds. Drag grew in a power fashion with speed and exponentially with the increase of RA, thus drag penalty for becoming thicker was relatively low for low speeds compared to high ones. We show that the drag increase with increasing RA was most probably due to bigger regions of flow separation behind the enlarged belly. We suggest that the rising drag penalty with an increasing RA, possibly together with pregnancy-related negative effects on muscle- and abdominal bending performance, will reduce the maximum swimming speed
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Research Interests: Biology and Placentation
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Research Interests: Biomechanics and Biology
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Reproductive mode is predicted to influence the form of sexual selection. The viviparity‐driven conflict hypothesis posits that a shift from lecithotrophic (yolk‐nourished) to matrotrophic (mother‐nourished or placental) viviparity drives... more
Reproductive mode is predicted to influence the form of sexual selection. The viviparity‐driven conflict hypothesis posits that a shift from lecithotrophic (yolk‐nourished) to matrotrophic (mother‐nourished or placental) viviparity drives a shift from precopulatory towards post‐copulatory sexual selection. In lecithotrophic species, we predict that precopulatory sexual selection will manifest as males exhibiting a broad distribution of sizes, and small and large males exhibiting contrasting phenotypes (morphology and coloration); conversely, in matrotrophic species, an emphasis on post‐copulatory sexual selection will preclude these patterns. We test these predictions by gathering data on male size, morphology and coloration for five sympatric Costa Rican poeciliid species that differ in reproductive mode (i.e. lecithotrophy vs. matrotrophy). We find tentative support for these predictions of the viviparity‐driven conflict hypothesis, with some interesting caveats and subtleties. In particular, we find that the three lecithotrophic species tend to show a broader distribution of male sizes than matrotrophic species. Furthermore, large males of such species tend to exhibit proportionately large dorsal and caudal fins and short gonopodia relative to small males, while these patterns are expressed to a lesser extent in the two matrotrophic species. Finally, large males in some of the lecithotrophic species exhibit darker fins relative to small males, a pattern not evident in either matrotrophic species. One unexpected finding was that even in the matrotrophic species Poeciliopsis retropinna and Poeciliopsis paucimaculata, which lack courtship and dichromatic coloration, some morphological traits exhibit significant allometric relationships, suggesting that even in these species precopulatory sexual selection may be present and shaping size‐specific male phenotypes in subtle ways.
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Live-bearing fish start hunting for mobile prey within hours after birth, an example of extreme precociality. Because prenatal, in utero, development of this behaviour is constrained by the lack of free-swimming sensory-motor... more
Live-bearing fish start hunting for mobile prey within hours after birth, an example of extreme precociality. Because prenatal, in utero, development of this behaviour is constrained by the lack of free-swimming sensory-motor interactions, immediate success after birth depends on innate, evolutionarily acquired patterns. Optimal performance however requires flexible adjustment to an unpredictable environment. To distinguish innate from postnatally developing patterns we analysed over 2000 prey capture events for 28 metallic livebearers (Girardinus metallicus; Poeciliidae), during their first 3 days after birth. We show that the use of synchronous pectoral fin beats for final acceleration and ingestion is fixed and presumably innate. It allows for direct, symmetrical control of swimming speed and direction, while avoiding head yaw. Eye movements and body curvatures, however, change considerably in the first few days, showing that eye-tail coordination requires postnatal development. The results show how successful prey captures for newborn, live-bearing fish are based on a combination of fixed motor programmes and rapid, postnatal development
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Swimming performance of pregnant live-bearing fish is presumably constrained by the additional drag associated with the reproductive burden. Yet, it is still unclear how and to what extent the reproductive investment affects body drag of... more
Swimming performance of pregnant live-bearing fish is presumably constrained by the additional drag associated with the reproductive burden. Yet, it is still unclear how and to what extent the reproductive investment affects body drag of the females. We examined the effect of different levels of reproductive investment on body drag. The biggest measured increase in body volume due to pregnancy was about 43%, linked to a wetted area increase of about 16% and 69% for the frontal area. We printed three-dimensional models of live-bearing fish in a straight body posture representing different reproductive allocation (RA) levels. We measured the drag and visualized the flow around these models in a flow tunnel at different speeds. Drag grew in a power fashion with speed and exponentially with the increase of RA, thus drag penalty for becoming thicker was relatively low for low speeds compared to high ones. We show that the drag increase with increasing RA was most probably due to bigger regions of flow separation behind the enlarged belly. We suggest that the rising drag penalty with an increasing RA, possibly together with pregnancy-related negative effects on muscle- and abdominal bending performance, will reduce the maximum swimming speed.
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De afgelopen decennia is er in toenemende mate aandacht gekomen voor natuurontwikkeling in rivieruiterwaarden. Een belangrijk onderdeel hiervan vormt het graven van hoogwatergeulen: korte nevenlopen die (bij hoogwater) parallel aan de... more
De afgelopen decennia is er in toenemende mate aandacht gekomen voor natuurontwikkeling in rivieruiterwaarden. Een belangrijk onderdeel hiervan vormt het graven van hoogwatergeulen: korte nevenlopen die (bij hoogwater) parallel aan de hoofdstroom met de rivier meestromen en die gedurende de rest van het jaar ook water houden. Zulke geulen worden vaak gekenmerkt door een lagere stroomsnelheid dan de rivier zelf, gevarieerde oevers met ondiepe zandbanken en een rijke oever- en onderwatervegetatie. In dit artikel wordt de visfauna beschreven in een recent aangelegde hoogwatergeul in natuurgebied de Raaijweide bij Venlo.
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Table S1. Literature study on all genes positively selected exclusively in H. formosa. (XLSX 16 kb)
Predicted change in female body volume during pregnancy in two hypothetical lecithotrophic (non-placental) and placentotrophic (placental) live-bearing fish species, assuming an equal female length, offspring number and offspring size at birth (IB = 1): (1) the placental species (dash-dot line) w...more
<p>Similar plots could be constructed for frontal or wetted surface area. For heuristic purposes the temporal patterns are assumed linear, because the exact shape of the relationship between female volume and time is currently... more
<p>Similar plots could be constructed for frontal or wetted surface area. For heuristic purposes the temporal patterns are assumed linear, because the exact shape of the relationship between female volume and time is currently unknown [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0195976#pone.0195976.ref020" target="_blank">20</a>].</p