Niklas Janz

Niklas Janz
Stockholm University | SU · Department of Zoology

Professor

About

103
Publications
22,567
Reads
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3,984
Citations
Introduction
I work with the evolution of insect-plant associations, in particular with regard to host range and how this may influence diversification.
Additional affiliations
January 2011 - present
Stockholm University
Position
  • Professor (Associate)

Publications

Publications (103)
Article
Full-text available
After almost 50 years of scrutiny, the ideas that Ehrlich and Raven presented in their classical paper on the coevolution between butterflies and plants are still very much alive. Much of this interest has involved the potential for codiversification, both in how the interaction itself diversifies and how the interaction affects modes and rates of...
Article
Full-text available
Plant-feeding insects make up a large part of earth's total biodiversity. While it has been shown that herbivory has repeatedly led to increased diversification rates in insects, there has been no compelling explanation for how plant-feeding has promoted speciation rates. There is a growing awareness that ecological factors can lead to rapid divers...
Article
Full-text available
1. One of the main challenges faced by ecologists today is to understand and predict how species interactions will respond to the current environmental change. It is likely that these changes will have a stronger effect on phylogenetic lineages that depend on intimate and specialised ecological interactions, such as most herbivorous insects. 2. In...
Article
Full-text available
The study of herbivorous insects underpins much of the theory that concerns the evolution of species interactions. In particular, Pieridae butterflies and their host plants have served as a model system for studying evolutionary arms races. To learn more about the coevolution of these two clades, we reconstructed ancestral ecological networks using...
Article
Full-text available
Climate and land use change can alter the incidence and strength of biotic interactions, with important effects on the distribution, abundance and function of species. To assess the importance of these effects and their dynamics, studies quantifying how biotic interactions change in space and time are needed. We studied interactions between nettle‐...
Preprint
Full-text available
The study of herbivorous insects underpins much of the theory that concerns the evolution of species interactions. In particular, Pieridae butterflies and their host plants have served as a model system for studying evolutionary arms-races. To learn more about how the two lineages co-evolved over time, we reconstructed ecological networks and netwo...
Article
Full-text available
• Many insects that live in temperate zones spend the cold season in a state of dormancy, referred to as diapause. As the insect must rely on resources that were gathered before entering diapause, keeping a low metabolic rate is of utmost importance. Organs that are metabolically expensive to maintain, such as the brain, can therefore become a liab...
Article
Full-text available
Recent advances in obtaining reduced representation libraries for next‐generation sequencing permit phylogenomic analysis of species‐rich, recently diverged taxa. In this study, we performed sequence capture with homemade PCR‐generated probes to study diversification among closely related species in a large insect genus to examine the utility of th...
Article
Full-text available
Intimate ecological interactions, such as those between parasites and their hosts, may persist over long time spans, coupling the evolutionary histories of the lineages involved. Most methods that reconstruct the coevolutionary history of such interactions make the simplifying assumption that parasites have a single host. Many methods also focus on...
Preprint
Full-text available
Aim Biotic interactions are an important factor structuring ecological communities but data scarcity limits our understanding of the impact of their response to climate and land use changes on communities. We studied the impact of a change in species assemblage on biotic interactions in a community of closely-related butterflies. Specifically, we e...
Preprint
Full-text available
Intimate ecological interactions, such as those between parasites and their hosts, may persist over long time spans, coupling the evolutionary histories of the lineages involved. Most methods that reconstruct the coevolutionary history of such associations make the simplifying assumption that parasites have a single host. Many methods also focus on...
Article
Full-text available
Explaining the exceptional diversity of herbivorous insects is an old problem in evolutionary ecology. Here we focus on the two prominent hypothesised drivers of their diversification, radiations after major host switch or variability in host use due to continuous probing of new hosts. Unfortunately, current methods cannot distinguish between these...
Article
Full-text available
In phytophagous insects such as butterflies, there is an evolutionary trend toward specialization in host plant use. One contributing mechanism for this pattern may be found in female host search behavior. Since search attention is limited, generalist females searching for hosts for oviposition may potentially increase their search efficacy by aimi...
Article
Full-text available
Colonization of novel hosts is thought to play an important role in parasite diversification, yet little consensus has been achieved about the macroevolutionary consequences of changes in host use. Here we offer a mechanistic basis for the origins of parasite diversity by simulating lineages evolved in silico. We describe an individual‐based model...
Article
Full-text available
An ovipositing insect experiences many sensory challenges during her search for a suitable host plant. These sensory challenges become exceedingly pronounced when host range increases, as larger varieties of sensory inputs have to be perceived and processed in the brain. Neural capacities can be exceeded upon information overload, inflicting costs...
Article
Parasite-host and insect-plant research have divergent traditions despite the fact that most phytophagous insects live parasitically on their host plants. In parasitology it is a traditional assumption that parasites are typically highly specialized; cospeciation between parasites and hosts is a frequently expressed default expectation. Insect-plan...
Article
Full-text available
Theory on plasticity driving speciation, as applied to insect–plant interactions (the oscillation hypothesis), predicts more species in clades with higher diversity of host use, all else being equal. Previous support comes mainly from specialized herbivores such as butterflies, and plasticity theory suggests that there may be an upper host range li...
Article
Full-text available
Changes in community composition resulting from climate change entail modifications of biotic interactions and reshape local species distributions. Such changes are currently occurring in nettle-feeding butterflies in Sweden where Araschnia levana has recently expanded its range northward and is now likely to interact with the resident species (Agl...
Article
Full-text available
Background Although most insect species are specialized on one or few groups of plants, there are phytophagous insects that seem to use virtually any kind of plant as food. Understanding the nature of this ability to feed on a wide repertoire of plants is crucial for the control of pest species and for the elucidation of the macroevolutionary mecha...
Article
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Background: In plant-feeding insects, the evolutionary retention of polyphagy remains puzzling. A better understanding of the relationship between these organisms and changes in the metabolome of their host plants is likely to suggest functional links between them, and may provide insights into how polyphagy is maintained. Results: We investigat...
Article
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In a recent paper in Evolution, Hamm and Fordyce (2015) published an analysis of "Patterns of host plant utilization and diversification in the brush-footed butterflies", which was presented as a test of our "oscillation hypothesis" (OH)(Janz et al. 2006; Janz and Nylin 2008; Nylin and Janz 2009). This study joins another recent paper (Hardy and Ot...
Article
Full-text available
Among insects, sexual pheromones are typically mixtures of two to several components, all of which are generally required to elicit a behavioural response. Here we show for the first time that a complete blend of sexual pheromone components is needed to elicit a response also in a butterfly. Males of the Green-veined White, Pieris napi, emit an aph...
Article
Full-text available
Herbivorous insects specialized on a narrow set of plants are believed to be better adapted to their specific hosts. This hypothesis is supported by observations of herbivorous insect species with a broader diet breadth which seemingly pay a cost through decreased oviposition accuracy. Despite many studies investigating female oviposition behavior,...
Article
Full-text available
1.When females mate with multiple partners, the risk of sperm competition depends on female mating history. To maximize fitness, males should adjust their mating investment according to this risk. In polyandrous butterflies males transfer a large, nutritious ejaculate at mating. Larger ejaculates delay female remating and confer an advantage in spe...
Conference Paper
Full-text available
It is generally known that insects use visual, olfactory and gustatory cues to find and evaluate targets such as food sources or host plants, but the particular role of each of the sensory modalities in the search process is less clear. One trait affecting the efficiency and accuracy of the host search process is host plant breadth. For example, sp...
Article
Full-text available
Variation in food stoichiometry affects individual performance and population dynamics, but it is also likely that species with different life histories should differ in their sensitivity to food stoichiometry. To address this question, we investigated the ability of the three nettle-feeding butterflies (Aglais urticae, Polygonia c-album, and Aglai...
Article
Full-text available
More than half of the proteome from mandibular glands in caterpillars is represented by chemosensory proteins. Based on sequence similarity, these proteins are putative transporters of ligands to gustatory receptors in sensory organs of insects. We sought to determine whether these proteins are inducible by comparing, both qualitatively and quantit...
Article
Full-text available
1. In the study of the evolution of insect–host plant interactions, important information is provided by host ranking correspondences among female preference, offspring preference, and offspring performance. Here, we contrast such patterns in two polyphagous sister species in the butterfly family Nymphalidae, the Nearctic Polygonia faunus, and the...
Article
Full-text available
Searching for resources is often a challenging task, especially for small organisms such as insects. Complex stimuli have to be extracted from the environment and translated into a relevant behavioral output. A first step in this process is to investigate the relative roles of the different senses during search for various resources. While the role...
Article
Full-text available
It has been suggested that phenotypic plasticity is a major factor in the diversification of life, and that variation in host range in phytophagous insects is a good model for investigating this claim. We explore the use of angiosperm plants as hosts for nymphalid butterflies, and in particular the evidence for past oscillations in host range and h...
Article
Full-text available
In most phytophagous insects, the larval diet strongly affects future fitness and in species that do not feed on plant parts as adults, larval diet is the main source of nitrogen. In many of these insect-host plant systems, the immature larvae are considered to be fully dependent on the choice of the mothers, who in turn possess a highly developed...
Article
Full-text available
Although changes in phenology and species associations are relatively well-documented responses to global warming, the potential interactions between these phenomena are less well understood. In this study, we investigate the interactions between temperature, phenology (in terms of seasonal timing of larval growth) and host plant use in the polypha...
Data
The database of polyphagous species in the family Nymphalidae, in Excel format.
Data
The character matrix for the two traits scoring polyphagy and use of host plant orders, for each higher butterfly taxon in the family Nymphalidae, in Excel format.
Data
Nexus file containing the character matrix and the phylogenetic tree of the family Nymphalidae used in the analyses.
Article
Full-text available
Transcriptome studies of insect herbivory are still rare, yet studies in model systems have uncovered patterns of transcript regulation that appear to provide insights into how insect herbivores attain polyphagy, such as a general increase in expression breadth and regulation of ribosomal, digestion- and detoxification-related genes. We investigate...
Article
Full-text available
Understanding the processing of odour mixtures is a focus in olfaction research. Through a neuroethological approach, we demonstrate that different odour types, sex and habitat cues are coded together in an insect herbivore. Stronger flight attraction of codling moth males, Cydia pomonella, to blends of female sex pheromone and plant odour, compare...
Article
Full-text available
Olfaction is in many species the most important sense, essential for food search, mate finding, and predator avoidance. Butterflies have been considered a microsmatic group of insects that mainly rely on vision due to their diurnal lifestyle. However, an emerging number of studies indicate that butterflies indeed use the sense of smell for locating...
Article
Full-text available
Subspecies are commonly used taxonomic units to formally describe intraspecific geographic variation in morphological traits. However, the concept of subspecies is not clearly defined, and there is little agreement about what they represent in terms of evolutionary units, and whether they can be used as reliably useful units in conservation, evolut...
Data
Protocol followed for isolation of 10 microsatellite loci for Polygonia c-album . Six of these loci were used in this study. (DOC)
Data
List of samples used along with the collection localities, Genbank accession numbers, collectors and haplotypes. (XLS)
Article
Full-text available
Butterflies are believed to use mainly visual cues when searching for food and oviposition sites despite that their olfactory system is morphologically similar to their nocturnal relatives, the moths. The olfactory ability in butterflies has, however, not been thoroughly investigated. Therefore, we performed the first study of odour representation...
Article
Experimental work on Polygonia c-album, a temperate polyphagous butterfly species, has shown that Swedish, Belgian, Norwegian and Estonian females are generalists with respect to host-plant preference, whereas females from UK and Spain are specialized on Urticaceae. Female preference is known to have a strong genetic component. We test whether the...
Data
Phylogeny of Nymphalinae reconstructed using maximum likelihood analysis. Numbers beside internal nodes are maximum likelihood bootstrap values obtained from RaxML. (TIF)
Data
Diet breadth and geographic range data for 182 Nymphalinae species. Data used in the analyses. Diet breadth measures used in the analyses were number of genera and diet breath index. Diet breadth index was calculated by multiplying the number of host plant genera by the number of families and orders used. (XLSX)
Data
List of taxa used in this study with their Genbank accession numbers. (XLSX)
Article
Full-text available
The "oscillation hypothesis" has been proposed as a general explanation for the exceptional diversification of herbivorous insect species. The hypothesis states that speciation rates are elevated through repeated correlated changes--oscillations--in degree of host plant specificity and geographic range. The aim of this study is to test one of the p...
Article
1. One possible explanation for the latitudinal gradient in species richness often demonstrated is a related gradient in niche breadth, which may allow for denser species packing in the more stable environments at low latitudes. 2. The evidence for such a gradient is, however, ambiguous, and the results have varied as much as the methods. Several s...
Article
Full-text available
The parasite paradox arises from the dual observations that parasites (broadly construed, including phytophagous insects) are resource specialists with restricted host ranges, and yet shifts onto relatively unrelated hosts are common in the phylogenetic diversification of parasite lineages and directly observable in ecological time. We synthesize t...