Top lectures - Leiden Biology
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“Top lectures” concerns a series of lectures by invited speakers of top quality who will give a lecture and who will be present at a mini-symposium of student presentations of a set of selected papers. The series is a joint undertaking by IBL, CML, and Naturalis. Each speaker is associated with a guest convener from one of these institutes.
Everybody is welcome to join the lectures and the student presentations.
- Next Top lecture
Hormone-mediated maternal effects in birds
Date: Friday, 25 May 2012, time: 10:00-11:00 hrs
Location: Sylvius building, 1st floor, Grote Collegezaal 1.5.31
Invited speaker: Wendt Müller, University of Antwerp, Belgium
Guest convener: Katharina Riebel, IBL
Abstract:
Maternal effects are defined as phenotypic effects mothers have on the phenotypes of their offspring. They are thought to be shaped by natural selection enabling adaptive responses in heterogeneous environments, because of their potential to generate immediate phenotypic change in the offspring. Maternal effects do have evolutionary consequences even if they initially do not alter the distribution of genotypes, but because they alter the phenotypes on which selection may later act on. The role of maternal effects in ecology and evolution is, therefore, now increasingly accepted. Maternal effects have been particularly well studied in birds, where the egg provides essential resources for offspring development. Both egg size and composition are determined by the mother, representing important maternal traits that generate maternal effects. One particular egg component, maternally derived yolk hormones, recently received increased attention in behavioral and evolutionary ecology - stimulated by the pioneering work of Hubert Schwabl. I will review the systematic variation in maternal yolk hormone levels and the numerous often persistent effects of yolk hormones on offspring phenotype that have been documented. First, I will take an evolutionary ecological approach with a focus on the ultimate aspects, before focusing on the underlying mechanisms and physiological trade-offs, which may have important implications for the selection on and evolution of hormone-mediated maternal effects. Finally, in order to understand the evolutionary significance of hormone-mediated maternal effects it is essential to take the perspective of all family members, parents and offspring, and I will discuss the potential of (hormone-mediated) maternal effects to influence the coadaptation of parent and offspring traits.
- Previous Top lectures
Universal diversity patterns: ecology and beyond
Date: Friday, 27 April 2012
Location: Big lecture hall, first floor, Sylvius building
Invited speaker: Jeffrey Nekola, University of New Mexico
Guest convener: Heike Kappes/Menno Schilthuizen, NCB NaturalisThis invitation is jointly supported by the NCB Naturalis Focus Groups Character Evolution and Dynamic Biodiversity.
Abstract:
Although species abundance distributions, species-area-relationships, species-time-relationships, and the distance decay of similarity have been long-used by ecologists to describe biodiversity and to test theory, these patterns are not limited to ecological systems. Rather, exact analogs may be found across a wide assortment of physical, biological and societal systems including geology, astronomy, climatology, sociology, linguistics, the arts, and many others. As a result, the ultimate causes for these patterns must not be ecological, but rather appear rooted in the second law of thermodynamics, complex systems behavior, and/or statistical mechanics. This talk provides an overview of these patterns, how they have been used −and misused− in ecology, and demonstrates how they can be better used to test ecological hypotheses. Jeff Nekola has established an eclectic research program that not only spans the ecological field (taxonomy and evolutionary biology to community ecology, macroecology, and theoretical ecology) but also works across a variety of study systems (land snails, lepidoptera, and vascular plants ranging from terrestrial to deep sea and from the arctic to tropics). He is also active in conservation biology, heirloom food plant preservation, and the ceramic, photographic, and installation arts.—————————————————————————————————————————————
Evolutionary ecology of host-parasite interactions: ticks and hole-nesting songbirds
Date: Friday, 27 January 2012
Location: Big lecture hall, first floor, Sylvius building
Invited speaker: Erik Matthyssen, Antwerp University
Guest convener: Hans de Iongh, CMLAbstract:
Parasitism is generally considered as an important evolutionary force, leading to mutual adaptations and arms races in host and parasite. Nevertheless, even in very commonly studied species such as hole-nesting songbirds, interactions with parasites have received comparatively little attention compared to other selection pressures such as predation, food or sexual selection. In this lecture I will report on our ongoing research on interactions between great and blue tits as hosts, and several tick species (Ixodidae) as parasites. Ticks have a number of features that make them particularly interesting for studies of host-parasite interactions, including their amenability to experimental infestations in both lab and field conditions. Great and blue tits are regularly infested with two tick species with highly contrasting ecologies: the generalist field-dwelling sheep tick (Ixodes ricinus) and the generalist tree-hole tick (Ixodes arboricola), a specialist of hole-nesting forest birds. I will first focus on the impact of ticks on hosts, and the possible defense strategies of birds to avoid or minimalize the cost of infestation. Then I will focus on behavioural and ecological adaptations of I. arboricola to its nidicolous lifestyle, which makes it highly dependent on its host for survival, future reproduction and dispersal. Since ticks feed only once in each life stage and remain attached to the host for several days, we conducted a series of experiments studying how ticks decide when to attack and when to leave a particular host (attachment and detachment strategies). Finally I will broaden the scope towards other hosts and tick species and discuss some of our research plans towards evolution of host specificity and the potential role of ticks as bridging vectors between multiple zoönotic cycles of Borrelia. In this part I will also refer to previous work by other authors on ticks in seabird colonies.—————————————————————————————————————————————
Hearing and lateral line sensation in fish; application of infrasound to fish guiding
Date: Thursday, 26 May 2011
Location: Big lecture hall, first floor, Sylvius building
Invited speaker: Olav Sand, University of Oslo
Guest convener: Hans Slabbekoorn, IBLAbstract:
The focus of research in the group of Prof Olav Sand at Oslo University is on membrane physiology and in particular the signal transduction pathways involved in the hypothalamic regulation of pituitary cells. However, Prof. Sand has published several highly interesting papers on hearing and lateral line sensation in fish. Background: The three pairs of otoliths in the inner ear of fish have a relatively high mass density and are in close contact with the sensory epithelium. When a fish is accelerated back and forth in a sound field, the sensory cells are stimulated by relative movements between the dense otoliths and the epithelium. The otolith organs are thus accelerometers, with a working range from zero to the upper auditory frequency limit. Hence, fish are superior to mammals regarding sensitivity to very low frequencies, including infrasound. Ambient infrasound constitutes a major part of the underwater “acoustic landscape”, or “soundscape”, which may be important for orientation. Infrasound is also important in prey-predator interactions, and is particularly potent in inducing behavioural reactions in fish. The lateral line system is insensitive to propagated sound, but is crucial for wake-tracking of moving objects. By detecting distortion of the hydrodynamic flow pattern around its own body, a moving fish may also use the lateral line to detect close, stationary objects.—————————————————————————————————————————————
Extreme positive selection on a highly-expressed larval ZP-domain gene
in Galaxias fishesDate: Friday, 20 May 2011
Invited speaker: Graham Wallis, University of Otago
Host: Pim Arntzen, NCB Naturalis
Guest convener: Hans Slabbekoorn, IBLAbstract:
Positive Darwinian selection can be revealed by a high ratio of
non-synonymous to synonymous substitutions in a coding region. This is
a stringent test, and rarely applies to an entire protein. We have
found a larval glycoprotein gene (LGP) in galaxiid fishes, with distant
similarity to Danio THP (Tamm-Horsefall urinary glycoprotein;
uromodulin) and cichlid SPP120 (seminal plasma glycoprotein) due to
conserved features of its zona pellucida (ZP) region, including 11
highly conserved cysteines, signal peptide, EHP, IHP, dimersiation sites
and a consensus furin cleavage site (CFCS). Using a combination of 454
sequencing of cDNA, and exon-primed intron-spanning sequencing of
genomic DNA, we obtained full sequences of the coding region (996 bp)
and its intervening sequences (1459 bp). LGP shows an exceptionally
strong signal of positive selection over the entire coding region, as
evidenced by dN/dS values > 1. Across 9 species of Galaxias, 87/332
(26%) of amino-acid residues are variable, compared with 9/386 (2%) for
mitochondrial cytb in the same group of species. Across 36
interspecific pairwise comparisons, genetic distances are in all cases
larger for coding region than for introns, by a factor of 2.4-fold on
average. Reading frame, gene structure, splice sites and many ZP motifs
are conserved across all species. Together with the fact that the gene
is expressed in all species, these results clearly rule out a
pseudogene. We show by 454 sequencing and qPCR that the transcript is
abundant (ca 0.5%) in newly-hatched larvae, and appears to be almost
absent from a range of adult tissues. We postulate that the strong
Darwinian evolution exhibited by this protein may reflect some type of
immuno-protection at this vulnerable larval stage.—————————————————————————————————————————————
Morphological evolution within and among Drosophila species.
Date: Tuesday, 19 April 2011
Invited speaker: Dr. Alistair P. McGregor, Oxford Brookes University
Hosts: Patricia Beldade and Maurijn van der Zee, IBLAbstract:
In the last 10 years there has been much progress in understanding the genetic basis of morphological differences among species. However, there are at least three areas that could be further explored to test current models and give a more complete picture of morphological evolution: What is the developmental genetic basis of differences in quantitative traits such as organ shape and size? To what extent do standing genetic polymorphisms underlying trait variation within species contribute to differences in the same traits between species? What evolutionary forces have shaped morphological differences? To address these questions my group employs species of the D. melanogaster subgroup and I will discuss ongoing projects in my lab to investigate the evolution of leg trichome patterns, and eye size and shape.—————————————————————————————————————————————
Evolution of Venoms in Snakes
Date: Friday, 11 March 2011
Invited speaker: R. M. Kini, National University of Singapore
Guest convener: Mike Richardson, IBLAbstract:
Prof. Kini’s research aims to understand structure-function relationships of proteins, particularly snake venom toxins, and their mechanism. Snake venoms are rich sources of toxins that interfere with various physiological processes. He is specifically interested in protein families of phospholipase A2 (PLA2) enzymes, serine proteinases, three-finger toxins and helveprins. The functional diversity despite the structural similarity and the presence of functional sites in different segments of the toxins makes his research interesting and challenging. The functional sites are used in designing proteins with novel biological activities and prototypes of therapeutic agents.—————————————————————————————————————————————
Sex and spite in the Mediterranean Flora
Date: Friday, 28 January 2011
Invited speaker: John R. Pannell, Oxford University
Guest convener: Tom de Jong, IBLAbstract:
Prof. Pannell’s research is broadly centered on the areas of ecological genetics and plant evolutionary ecology. He is particularly interested in understanding (1) plant gender and sex allocation strategies; (2) the ecology, genetics and evolution of polyploidy, especially in its interaction with the sexual system; (3) the evolution of local adaptation in colonising plant species; and (4) the ecology and population genetics of metapopulations subject to repeated local extinctions and re‐colonisations. He approach these topics from both a theoretical and an empirical perspective, with the latter both field and lab-based.—————————————————————————————————————————————-
Character Displacement in Animal Signals: Insights from Neotropical Suboscine Birds
Date: Thursday 24th June 2010
Invited speaker: Joseph Tobias, Oxford University
Guest convener: Hans Slabbekoorn, IBLAbstract:
Species interactions are predicted to drive trait divergence in sympatry as a result of reproductive character displacement in mating signals, or trait convergence as a result of agonistic character displacement in aggressive signals. Despite opposing predictions, neither of these hypotheses has received much support from previous empirical studies. The songs of suboscine birds provide a useful system for exploring these ideas because they are simple and quantifiable, and they function in both mate attraction and territory defence. The results of long-term experimental and comparative studies in Neotropical suboscine birds suggest that song evolution is shaped by a combination of divergent and convergent processes, thus shedding light on a long-standing debate in evolutionary biology.—————————————————————————————————————————————-
The nutritive soul, the conspiracy of signals and the programme of ageing
Date:Friday 18th June 2010
Invited speaker: Armand Leroi, Imperial College London
Guest convener: Mike Richardson, IBLAbstract: The idea that reproduction increases the rate of ageing is very old. Yet it remains popular, indeed, it is often held to be fundamental to the evolutionary theory of senescence or modern life-history theory. But is it? I review the evidence for a senescence cost of reproduction and conclude that none exists. I argue that the negative correlation between longevity and reproduction visible in so many animals under so many circumstances is, instead, due to a “conspiracy” of molecular signals that jointly regulate these traits – and I outline the nature of these signals as they are understood in Drosophila and C. elegans. Finally, I turn to the question of why we, and most other animals age. I suggest that ageing is due to developmental programmes going awry in adults. I argue that this is also how G. C. Williams, one of the founders of evolutionary biology, understood the cause of ageing. And I show how the “bad programmes” that cause ageing are being uncovered in C. elegans and other animals.
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Plant invasions, interspecific hybridization and evolution: hybrid speciation and gene transfer in action
Date: Thursday 27th May 2010
Invited speaker: Richard Abbott, University of St Andrews
Guest convener: Peter Klinkhamer, IBLAbstract:
Interspecific hybridization has long been recognized as an important force in plant evolution. In recent years there has been a renaissance in research aimed at understanding the effects and evolutionary consequences of hybridization in plants, due largely to the increased availability of a wide range of new molecular tools for analysis. Here, I shall focus on work we have conducted on recent hybrid speciation and introgression (gene transfer) in the genus Senecio. First, I shall describe work on the origin and establishment of an invasive diploid hybrid species with particular emphasis on genetic changes occurring in the initial stages of the event. Second, I shall describe the isolation and characterization of genes transferred from this species to a native tetraploid species, causing significant changes in floral morphology and outcrossing rate of the recipient species. The latter work illustrates the potential of introgression for bringing about evolutionary change in plants even in situations where strong reproductive barriers exist between species.—————————————————————————————————————————————-
Learning, developmental plasticity and the evolution of morphological asymmetry
Date: Thursday 22th April 2010
Invited speaker: Richard Palmer, University of Alberta
Guest convener: Menno Schilthuizen, NaturalisAbstract:
Evolution by natural selection requires three steps. New variants of organisms: must arise, must have an impact on fitness (survival or fecundity), and must (ultimately) be heritable. The first step – how new variants arise - remains controversial. Traditionally, new phenotypes are attributed to novel genotypes (mutants or recombinants). But developmental plasticity may be a more important source of new variants than generally recognized. The absence of heritable variation for direction of asymmetry in species that show a random mixture of asymmetric forms (i.e., equal numbers of right- and left-handed forms), identifies a unique phenotype - “direction of asymmetry” - for which there is no genotype. A wide-ranging survey of asymmetry variation within and among species of animals and plants offers some of the strongest evidence to date for a ‘phenotype-precedes-genotype’ mode of evolution. In addition, the tendency of many animals to learn (e.g., handed behavior) may facilitate both the origin and the amplification of right-left morphological differences via developmental plasticity. Such an interplay between learning and developmental plasticity might greatly enhance the rate of morphological evolution.—————————————————————————————————————————————-
