Publications by authors named "Bart J A Pollux"

18 Publications

  • Page 1 of 1

Female reproductive mode shapes allometric scaling of male traits in live-bearing fishes (family Poeciliidae).

J Evol Biol 2021 Jul 21;34(7):1144-1155. Epub 2021 Jun 21.

Department of Animal Sciences, Wageningen University, Wageningen, The Netherlands.

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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http://dx.doi.org/10.1111/jeb.13875DOI Listing
July 2021

The evolution of the placenta in poeciliid fishes.

Curr Biol 2021 May 2;31(9):2004-2011.e5. Epub 2021 Mar 2.

Department of Biology, University of California, Riverside, Riverside, CA 92521, USA. Electronic address:

How and why complex organs evolve is generally lost to history. The mammalian placenta, for example, was derived from a single common ancestor that lived over 100 million years ago. Therefore, the selective factors favoring this complex trait remain obscure. Species in the live-bearing fish family Poeciliidae have independently evolved placentas numerous times while retaining closely related non-placental sister species. This provides the raw material to test alternative hypotheses for the evolution of the placenta. We assemble an extensive species-level dataset on reproductive mode, life histories, and habitat, and then implement phylogenetic comparative methods to test adaptive hypotheses for the evolution of the placenta. We find no consistent family-wide associations between placentation and habitat. However, placental species exhibit significantly reduced reproductive allotment and have a higher likelihood of exhibiting superfetation (the ability to gestate multiple broods at different developmental stages). Both features potentially increase body streamlining and enhance locomotor performance during pregnancy, possibly providing selective advantage in performance-demanding environments such as those with high predation or fast water flow. Furthermore, we found significant interactions between body size and placentation for offspring size and fecundity. Relative to non-placental species, placentation is associated with higher fecundity and smaller offspring size in small-bodied species and lower fecundity and larger offspring size in large-bodied species. This pattern suggests that there may be two phenotypic adaptive peaks, corresponding to two selective optima, associated with placentation: one represented by small-bodied species that have fast life histories, and the second by large-bodied species with slow life histories.
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http://dx.doi.org/10.1016/j.cub.2021.02.008DOI Listing
May 2021

Parallel Genomic Changes Drive Repeated Evolution of Placentas in Live-Bearing Fish.

Mol Biol Evol 2021 May;38(6):2627-2638

Experimental Zoology Group, Wageningen University, Wageningen, The Netherlands.

The evolutionary origin of complex organs challenges empirical study because most organs evolved hundreds of millions of years ago. The placenta of live-bearing fish in the family Poeciliidae represents a unique opportunity to study the evolutionary origin of complex organs, because in this family a placenta evolved at least nine times independently. It is currently unknown whether this repeated evolution is accompanied by similar, repeated, genomic changes in placental species. Here, we compare whole genomes of 26 poeciliid species representing six out of nine independent origins of placentation. Evolutionary rate analysis revealed that the evolution of the placenta coincides with convergent shifts in the evolutionary rate of 78 protein-coding genes, mainly observed in transporter- and vesicle-located genes. Furthermore, differences in sequence conservation showed that placental evolution coincided with similar changes in 76 noncoding regulatory elements, occurring primarily around genes that regulate development. The unexpected high occurrence of GATA simple repeats in the regulatory elements suggests an important function for GATA repeats in developmental gene regulation. The distinction in molecular evolution observed, with protein-coding parallel changes more often found in metabolic and structural pathways, compared with regulatory change more frequently found in developmental pathways, offers a compelling model for complex trait evolution in general: changing the regulation of otherwise highly conserved developmental genes may allow for the evolution of complex traits.
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http://dx.doi.org/10.1093/molbev/msab057DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8136483PMC
May 2021

Parasite infestation influences life history but not boldness behavior in placental live-bearing fish.

Oecologia 2020 Dec 3;194(4):635-648. Epub 2020 Nov 3.

Experimental Zoology Group, Department of Animal Sciences, Wageningen University, 6708 WD, Wageningen, The Netherlands.

Parasites can negatively affect the reproductive success of hosts. Placental species may be particularly susceptible, because parasite-induced stress during pregnancy could potentially influence embryo development. Here, we examine the consequences of a trematode infestation (black spot disease, BSD) for fetal development and adult behavior in 19 natural populations of the placental live-bearing fish species Poeciliopsis retropinna (Poeciliidae) in Costa Rica. First, we observed substantial variation in parasite infestation among populations which correlated with a number of local environmental conditions (elevation, river width, depth, and flow velocity). Furthermore, we observed substantial variation in parasite infestation among females within populations associated with maternal age and size. We found that the infestation rate significantly influenced embryonic development, with more heavily parasitized females producing smaller and worse-conditioned offspring at birth, possibly, because a costly immune response during pregnancy limits, either directly or indirectly, nourishment to developing embryos. Finally, a behavioral experiment in the field showed that the infestation rate did not affect an individual's boldness. Our study indicates that in placental live-bearing fish parasite infestation leads to reduced embryo provisioning during pregnancy, resulting in a smaller offspring size and quality at birth potentially with negative implications for offspring fitness.
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http://dx.doi.org/10.1007/s00442-020-04795-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7683485PMC
December 2020

Molecular Signatures of Placentation and Secretion Uncovered in Poeciliopsis Maternal Follicles.

Mol Biol Evol 2020 09;37(9):2679-2690

Department of Genetics, Stanford University School of Medicine, Stanford, CA.

Placentation evolved many times independently in vertebrates. Although the core functions of all placentas are similar, we know less about how this similarity extends to the molecular level. Here, we study Poeciliopsis, a unique genus of live-bearing fish that have independently evolved complex placental structures at least three times. The maternal follicle is a key component of these structures. It envelops yolk-rich eggs and is morphologically simple in lecithotrophic species but has elaborate villous structures in matrotrophic species. Through sequencing, the follicle transcriptome of a matrotrophic, Poeciliopsis retropinna, and lecithotrophic, P. turrubarensis, species we found genes known to be critical for placenta function expressed in both species despite their difference in complexity. Additionally, when we compare the transcriptome of different river populations of P. retropinna, known to vary in maternal provisioning, we find differential expression of secretory genes expressed specifically in the top layer of villi cells in the maternal follicle. This provides some of the first evidence that the placental structures of Poeciliopsis function using a secretory mechanism rather than direct contact with maternal circulation. Finally, when we look at the expression of placenta proteins at the maternal-fetal interface of a larger sampling of Poeciliopsis species, we find expression of key maternal and fetal placenta proteins in their cognate tissue types of all species, but follicle expression of prolactin is restricted to only matrotrophic species. Taken together, we suggest that all Poeciliopsis follicles are poised for placenta function but require expression of key genes to form secretory villi.
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http://dx.doi.org/10.1093/molbev/msaa121DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7475030PMC
September 2020

Predation risk shapes the degree of placentation in natural populations of live-bearing fish.

Ecol Lett 2020 May 12;23(5):831-840. Epub 2020 Mar 12.

Department of Animal Sciences, Wageningen University, 6708 WD, Wageningen, Netherlands.

The placenta is a complex life-history trait that is ubiquitous across the tree of life. Theory proposes that the placenta evolves in response to high performance-demanding conditions by shifting maternal investment from pre- to post-fertilisation, thereby reducing a female's reproductive burden during pregnancy. We test this hypothesis by studying populations of the fish species Poeciliopsis retropinna in Costa Rica. We found substantial variation in the degree of placentation among natural populations associated with predation risk: females from high predation populations had significantly higher degrees of placentation compared to low predation females, while number, size and quality of offspring at birth remained unaffected. Moreover, a higher degree of placentation correlated with a lower reproductive burden and hence likely an improved swimming performance during pregnancy. Our study advances an adaptive explanation for why the placenta evolves by arguing that an increased degree of placentation offers a selective advantage in high predation environments.
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http://dx.doi.org/10.1111/ele.13487DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7187176PMC
May 2020

The Genomes of the Livebearing Fish Species Poeciliopsis retropinna and Poeciliopsis turrubarensis Reflect Their Different Reproductive Strategies.

Mol Biol Evol 2020 05;37(5):1376-1386

Animal Breeding and Genomics Group, Wageningen University, Wageningen, The Netherlands.

The evolution of a placenta is predicted to be accompanied by rapid evolution of genes involved in processes that regulate mother-offspring interactions during pregnancy, such as placenta formation, embryonic development, and nutrient transfer to offspring. However, these predictions have only been tested in mammalian species, where only a single instance of placenta evolution has occurred. In this light, the genus Poeciliopsis is a particularly interesting model for placenta evolution, because in this genus a placenta has evolved independently from the mammalian placenta. Here, we present and compare genome assemblies of two species of the livebearing fish genus Poeciliopsis (family Poeciliidae) that differ in their reproductive strategy: Poeciliopsis retropinna which has a well-developed complex placenta and P. turrubarensis which lacks a placenta. We applied different assembly strategies for each species: PacBio sequencing for P. retropinna (622-Mb assembly, scaffold N50 of 21.6 Mb) and 10× Genomics Chromium technology for P. turrubarensis (597-Mb assembly, scaffold N50 of 4.2 Mb). Using the high contiguity of these genome assemblies and near-completeness of gene annotations to our advantage, we searched for gene duplications and performed a genome-wide scan for genes evolving under positive selection. We find rapid evolution in major parts of several molecular pathways involved in parent-offspring interaction in P. retropinna, both in the form of gene duplications as well as positive selection. We conclude that the evolution of the placenta in the genus Poeciliopsis is accompanied by rapid evolution of genes involved in similar genomic pathways as found in mammals.
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http://dx.doi.org/10.1093/molbev/msaa011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7182214PMC
May 2020

Superfetation reduces the negative effects of pregnancy on the fast-start escape performance in live-bearing fish.

Proc Biol Sci 2019 12 27;286(1916):20192245. Epub 2019 Nov 27.

Experimental Zoology Chair Group, Wageningen University and Research, 6708WD Wageningen, The Netherlands.

Superfetation, the ability to simultaneously carry multiple litters of different developmental stages , is a reproductive strategy that evolved repeatedly in viviparous animal lineages. The evolution of superfetation is hypothesized to reduce the reproductive burden and, consequently, improve the locomotor performance of the female during pregnancy. Here, we apply new computer-vision-based techniques to study changes in body shape and three-dimensional fast-start escape performance during pregnancy in three live-bearing fishes (family Poeciliidae) that exhibit different levels of superfetation. We found that superfetation correlates with a reduced abdominal distension and a more slender female body shape just before parturition. We further found that body slenderness positively correlates with maximal speeds, curvature amplitude and curvature rate, implying that superfetation improves the fast-start escape performance. Collectively, our study suggests that superfetation may have evolved in performance-demanding (e.g. high flow or high predation) environments to reduce the locomotor cost of pregnancy.
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http://dx.doi.org/10.1098/rspb.2019.2245DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6939275PMC
December 2019

How conflict shapes evolution in poeciliid fishes.

Nat Commun 2019 07 26;10(1):3335. Epub 2019 Jul 26.

Department of Biology, University of California, Riverside, CA, 92521, USA.

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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http://dx.doi.org/10.1038/s41467-019-11307-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6659687PMC
July 2019

The genome of the live-bearing fish Heterandria formosa implicates a role of conserved vertebrate genes in the evolution of placental fish.

BMC Evol Biol 2019 07 26;19(1):156. Epub 2019 Jul 26.

Experimental Zoology Group, Wageningen University, Wageningen, The Netherlands.

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. This evolutionary process can be studied by comparing closely related species that vary in the presence or absence of their organs. This is the case for the placenta in the live-bearing fish family Poeciliidae, as members of this family vary markedly in their ability to supply nutrients to their offspring via a placenta. Here, we investigate the genomic basis underlying this phenotypic variation in 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 may have played 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 for a placental poeciliid. We looked for signatures of adaptive evolution by comparing its gene sequences to those of three non-placental live-bearing relatives. Using comparative evolutionary analyses, we found 17 genes that were positively selected exclusively in H. formosa, as well as five gene duplications exclusive to H. formosa. 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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http://dx.doi.org/10.1186/s12862-019-1484-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6660938PMC
July 2019

Coasting in live-bearing fish: the drag penalty of being pregnant.

J R Soc Interface 2019 02;16(151):20180714

2 Faculty of Science & Engineering, University of Groningen , Nijenborgh 7, AG Groningen 9747 , The Netherlands.

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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http://dx.doi.org/10.1098/rsif.2018.0714DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6408347PMC
February 2019

Maternal size and body condition predict the amount of post-fertilization maternal provisioning in matrotrophic fish.

Ecol Evol 2018 Dec 11;8(24):12386-12396. Epub 2018 Dec 11.

Department of Animal Sciences Wageningen University Wageningen The Netherlands.

Maternal effects often provide a mechanism for adaptive transgenerational phenotypic plasticity. The maternal phenotype can profoundly influence the potential for such environmentally induced adjustments of the offspring phenotype, causing correlations between offspring and maternal traits. Here, we study potential effects of the maternal phenotype on offspring provisioning prior to and during gestation in the matrotrophic live-bearing fish species . Specifically, we examine how maternal traits such as body fat, lean mass, and length relate to pre- (i.e., allocation to the egg prior to fertilization) and post-fertilization (i.e., allocation to the embryo during pregnancy) maternal provisioning and how this ultimately affects offspring size and body composition at birth. We show that pre- and post-fertilization maternal provisioning is associated with maternal length and body fat, but not with maternal lean mass. Maternal length is proportionally associated with egg mass at fertilization and offspring mass at birth, notably without changing the ratio of pre- to post-fertilization maternal provisioning. This ratio, referred to as the matrotrophy index (MI), is often used to quantify the level of matrotrophy. By contrast, the proportion of maternal body fat is positively associated with post-fertilization, but not pre-fertilization, maternal provisioning and consequently is strongly positively correlated with the MI. We furthermore found that the composition of embryos changes throughout pregnancy. Females invest first in embryo lean mass, and then allocate fat reserves to embryos very late in pregnancy. We argue that this delay in fat allocation may be adaptive, because it delays an unnecessary high reproductive burden to the mother during earlier stages of pregnancy, potentially leading to a more slender body shape and improved locomotor performance. In conclusion, our study suggests that (a) offspring size at birth is a plastic trait that is predicted by both maternal length and body fat, and (b) the MI is a plastic trait that is predicted solely by the proportion of maternal body fat. It herewith provides new insights into the potential maternal causes and consequences of embryo provisioning during pregnancy in matrotrophic live-bearing species.
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http://dx.doi.org/10.1002/ece3.4542DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6308890PMC
December 2018

Why do placentas evolve? Evidence for a morphological advantage during pregnancy in live-bearing fish.

PLoS One 2018 16;13(4):e0195976. Epub 2018 Apr 16.

Experimental Zoology Chair Group, Department of Animal Sciences, Wageningen University & Research, Wageningen, The Netherlands.

A live-bearing reproductive strategy can induce large morphological changes in the mother during pregnancy. The evolution of the placenta in swimming animals involves a shift in the timing of maternal provisioning from pre-fertilization (females supply their eggs with sufficient yolk reserves prior to fertilization) to post-fertilization (females provide all nutrients via a placenta during the pregnancy). It has been hypothesised that this shift, associated with the evolution of the placenta, should confer a morphological advantage to the females leading to a more slender body shape during the early stages of pregnancy. We tested this hypothesis by quantifying three-dimensional shape and volume changes during pregnancy and in full-grown virgin controls of two species within the live-bearing fish family Poeciliidae: Poeciliopsis gracilis (non-placental) and Poeciliopsis turneri (placental). We show that P. turneri is more slender than P. gracilis at the beginning of the interbrood interval and in virgins, and that these differences diminish towards the end of pregnancy. This study provides the first evidence for an adaptive morphological advantage of the placenta in live-bearing fish. A similar morphological benefit could drive the evolution of placentas in other live-bearing (swimming) animal lineages.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0195976PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5901924PMC
July 2018

Three-dimensional analysis of the fast-start escape response of the least killifish, .

J Exp Biol 2018 04 6;221(Pt 7). Epub 2018 Apr 6.

Experimental Zoology Group, Department of Animal Sciences, Wageningen University & Research, Wageningen 6708 WD, The Netherlands.

Fish make C-starts to evade predator strikes. Double-bend (DB) C-starts consist of three stages: Stage 1, in which the fish rapidly bends into a C-shape; Stage 2, in which the fish bends in the opposite direction; and a variable Stage 3. In single-bend (SB) C-starts, the fish immediately straightens after Stage 1. Despite fish moving in three-dimensional (3D) space, fast-start responses of adult fish have mainly been studied in a horizontal plane. Using automated 3D tracking of multi-camera high-speed video sequences, we show that both SB and DB fast-starts by adult female least killifish () often contain a significant vertical velocity component, and large changes in pitch (DB up to 43 deg) and roll (DB up to 77 deg) angles. Upwards and downwards elevation changes are correlated with changes in pitch angle of the head; movement in the horizontal plane is correlated with changes in yaw angle of the head. With respect to the stimulus, escape heading correlates with the elevation of the fish at the onset of motion. Irrespective of the initial orientation, fish can escape in any horizontal direction. In many cases, the centre of mass barely accelerates during Stage 1. However, it does accelerate in the final direction of the escape in other instances, indicating that Stage 1 can serve a propulsive role in addition to its preparatory role for Stage 2. Our findings highlight the importance of large-scale 3D analyses of fast-start manoeuvres of adult fish in uncovering the versatility of fish escape repertoire.
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http://dx.doi.org/10.1242/jeb.168609DOI Listing
April 2018

Consistent individual differences in seed disperser quality in a seed-eating fish.

Authors:
Bart J A Pollux

Oecologia 2017 Jan 4;183(1):81-91. Epub 2016 Oct 4.

Experimental Zoology Group, Department of Animal Sciences, Wageningen University, De Elst 1, 6708 WD, Wageningen, The Netherlands.

Animal-mediated seed dispersal (zoochory) is considered to be an important mechanism regulating biological processes at larger spatial scales. To date, intra-specific variation in seed disperser quality within seed-dispersing animals has not been studied. Here, I employed seed feeding trials to quantify individual differences in disperser quality within the common carp (Cyprinus carpio) using seeds of two aquatic plants: unbranched bur-reed (Sparganium emersum, Sparganiaceae) and arrowhead (Sagittaria sagittifolia, Alismataceae). I found substantial variation among carp individuals in their propensity to ingest seeds and their ability to digest them, resulting in up to 31-fold differences in the probability of seed dispersal. In addition, there were significant differences in the time that seeds are retained in their digestive systems, generating a twofold difference in the maximum distance over which they can potentially disperse seeds. I propose that seed-eating animal species consist of individuals that display continuous variation in disperser quality, with at one end of the continuum individuals that are likely to eat seeds, pass them unharmed through their digestive tract and transport them over large distances to new locations (i.e. high-quality seed dispersers) and at the other end individuals that rarely eat seeds, destroy most of the ones they ingest and transport the few surviving seeds over relatively short distances (low-quality seed dispersers). Although individual differences in seed dispersal quality could be the result of a variety of factors, these results underline the ecological and evolutionary potential of such variation for both plants and animals.
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http://dx.doi.org/10.1007/s00442-016-3749-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5239806PMC
January 2017

Acquired versus innate prey capturing skills in super-precocial live-bearing fish.

Proc Biol Sci 2016 07;283(1834)

Experimental Zoology Group, Department of Animal Sciences, Wageningen University, Wageningen, The Netherlands.

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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http://dx.doi.org/10.1098/rspb.2016.0972DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4947892PMC
July 2016

Native and non-native plants provide similar refuge to invertebrate prey, but less than artificial plants.

PLoS One 2015 17;10(4):e0124455. Epub 2015 Apr 17.

Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, the Netherlands.

Non-native species introductions are widespread and can affect ecosystem functioning by altering the structure of food webs. Invading plants often modify habitat structure, which may affect the suitability of vegetation as refuge and could thus impact predator-prey dynamics. Yet little is known about how the replacement of native by non-native vegetation affects predator-prey dynamics. We hypothesize that plant refuge provisioning depends on (1) the plant's native status, (2) plant structural complexity and morphology, (3) predator identity, and (4) prey identity, as well as that (5) structurally similar living and artificial plants provide similar refuge. We used aquatic communities as a model system and compared the refuge provided by plants to macroinvertebrates (Daphnia pulex, Gammarus pulex and damselfly larvae) in three short-term laboratory predation experiments. Plant refuge provisioning differed between plant species, but was generally similar for native (Myriophyllum spicatum, Ceratophyllum demersum, Potamogeton perfoliatus) and non-native plants (Vallisneria spiralis, Myriophyllum heterophyllum, Cabomba caroliniana). However, plant refuge provisioning to macroinvertebrate prey depended primarily on predator (mirror carp: Cyprinus carpio carpio and dragonfly larvae: Anax imperator) and prey identity, while the effects of plant structural complexity were only minor. Contrary to living plants, artificial plant analogues did improve prey survival, particularly with increasing structural complexity and shoot density. As such, plant rigidity, which was high for artificial plants and one of the living plant species evaluated in this study (Ceratophyllum demersum), may interact with structural complexity to play a key role in refuge provisioning to specific prey (Gammarus pulex). Our results demonstrate that replacement of native by structurally similar non-native vegetation is unlikely to greatly affect predator-prey dynamics. We propose that modification of predator-prey interactions through plant invasions only occurs when invading plants radically differ in growth form, density and rigidity compared to native plants.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0124455PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4401678PMC
April 2016

Niche segregation in two closely related species of stickleback along a physiological axis: explaining multidecadal changes in fish distribution from iron-induced respiratory impairment.

Aquat Ecol 2012;46(2):241-248. Epub 2012 Apr 21.

Experimental Zoology Group, Department of Animal Sciences, Wageningen University, De Elst 1, 6708 WD Wageningen, The Netherlands.

Acute exposure to iron can be lethal to fish, but long-term sublethal impacts of iron require further study. Here we investigated whether the spatial and temporal distribution (1967-2004) of two closely related species of stickleback matched the spatial distribution of iron concentrations in the groundwater. We used the 'Northern Peel region', a historically iron-rich peat landscape in The Netherlands as a case study. This allowed us to test the hypothesis that niche segregation in two closely related species of stickleback occurred along a physiological axis. Patterns in stickleback occurrence were strongly associated with spatial patterns in iron concentrations before 1979: iron-rich grid cells were avoided by three-spined stickleback (, Linnaeus 1758) and preferred by nine-spined stickleback (, [Linnaeus, 1758]). After 1979, the separation between both sticklebacks became weaker, corresponding to a decreased influence of local groundwater on stream water quality. The way both species changed their distribution in the field provides a strong indication that they differ in their susceptibility to iron-rich conditions. These observed differences correspond with differences in their respiration physiology, tolerance of poor oxygen conditions and overall life-history strategy documented in the literature. Our results exemplify how species can partition niche along a non-structural niche axis, such as sublethal iron-rich conditions. Other fish species may similarly segregate along concentration gradients in iron, while sublethal concentrations of other metals such as copper may similarly impact fish via respiratory impairment and reduced aerobic scope.
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http://dx.doi.org/10.1007/s10452-012-9395-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4431660PMC
April 2012