Mueller C

Bio: Mueller C is an academic researcher from Bielefeld University. The author has contributed to research in topics: Offspring & Agonistic behaviour. The author has an hindex of 2, co-authored 5 publications receiving 10 citations.

Syndromes in suites of correlated traits suggest multiple mechanisms facilitating invasion in a plant range-expander

Abstract: Various mechanisms can facilitate the success of plant invasions simultaneously, but may be difficult to disentangle. In the present study, plants of the range-expanding species Bunias orientalis from native, invasive and naturalised, not yet invasive populations were compared in a field common garden over two years. Plants were grown under two nitrate-regimes and multiple traits regarding growth, defence, antagonist loads and reproduction were measured. A rank-based clustering approach was used to assign correlated traits to distinct suites. These suites were analysed for “syndromes” that are expressed as a function of population origin and/or fertilisation treatment and might represent different invasion mechanisms. Indeed, distinct suites of traits were differentially affected by these factors. The results suggest that several pre-adaptation properties, such as certain growth characteristics and intraspecific chemical variation, as well as post-introduction adaptations to antagonists and resource availability in novel habitats, are candidate mechanisms that facilitate the success of invasive B. orientalis in parallel. It was concluded that rank-based clustering is a robust and expedient approach to integrate multiple traits for elucidating invasion syndromes within individual species. Studying a multitude of traits at different life-history and establishment stages of plants grown under distinct resource treatments reveals species-specific trade-offs and resource sinks and simplifies the interpretation of trait functions for the potential invasive success of plants.

Consequences of pharmacophagous uptake from plants and conspecifics in a sawfly elucidated using chemical and molecular techniques

Abstract: Pharmacophagy involves the sequestration of specialised plant metabolites for non-nutritive purposes and commonly occurs in insects Here we investigate pharmacophagy in the turnip sawfly, Athalia rosae, where adults not only collect specialised metabolites (clerodanoids) from a plant (Ajuga reptans), but also from the exterior of conspecifics via fighting Using behavioural assays, chemical analytics, and RNAseq we show that when individuals nibble on conspecifics that have already acquired clerodanoids from A reptans leaves, this nibbling results in the transfer of compounds between individuals Furthermore, unlike other pharmacophagous insects, the acquisition of clerodanoids by A rosae from the leaves of A reptans does not induce the upregulation of known detoxification or sequestration genes and pathways In contrast, pharmacophagous nibbling on conspecifics results in the upregulation of metabolic pathways associated with elevated metabolic rates and increased energy consumption It therefore seems that individuals attack conspecifics to acquire clerodanoids despite the apparent metabolic costs of this form of pharmacophagy compared to clerodanoid uptake from a plant Changes in the metabolic phenotype of Arosae individuals consequently has profound consequences for social interactions with possible ramifications for their social niche Summary statementThe turnip sawfly (Athalia rosae) gains potentially beneficial compounds from the leaf surface of non-food plants (eg Ajuga reptans), but can also steal these compounds from conspecifics via aggressive nibbling

Fighting over defence chemicals disrupts mating behaviour

Abstract: Studies on intraspecific contest behaviour predominantly focus on contests between individuals of the same sex, however contest behaviour is also expected to occur between individuals of the opposite sex including possible mates. Here we investigate potential trade-offs between mating and fighting behaviour in the turnip sawfly (Athalia rosae). Adults of this species collect chemical defence compounds (clerodanoids) directly from plants but also indirectly by nibbling on conspecifics that have already obtained clerodanoids themselves, a highly aggressive behavioural interaction. An A. rosae individual without clerodanoids may therefore be the potential mate or attacker of an individual of the opposite sex that has gained clerodanoids. We paired males and females with or without clerodanoid access and manipulated body mass differences between the sexes via the early life starvation of females. We show that asymmetrical clerodanoid acquisition between male-female pairs causes an increase in agonistic nibbling behaviour, irrespective of sex. Moreover, fighting over clerodanoids disrupted mating behaviour, and the frequency of aggressive nibbling behaviour in these pairs was determined by the comparative body mass of the attacking individual. Our study highlights the vital importance of investigating agonistic intersex interactions not only over mating but also over resources.

Chemical patterns of colony membership and mother-offspring similarity in Antarctic fur seals are reproducible over time

Abstract: Replication studies are essential for assessing the validity of previous research findings and for probing their generality. However, it has proven challenging to reproduce the results of ecological and evolutionary studies, partly because of the complexity and lability of many of the phenomena being investigated, but also due to small sample sizes, low statistical power and publication bias. Additionally, replication is often considered too difficult in field settings where many factors are beyond the investigator9s control and where spatial and temporal dependencies may be strong. We investigated the feasibility of reproducing original research findings in the field of chemical ecology by attempting to replicate a previous study by our team on Antarctic fur seals (Arctocephalus gazella). In the original study, skin swabs from 41 mother-offspring pairs from two adjacent breeding colonies on Bird Island, South Georgia, were analysed using gas chromatography-mass spectrometry. Seals from the two colonies differed significantly in their chemical fingerprints, suggesting that colony membership may be chemically encoded, and mothers were also chemically similar to their pups, implying that phenotype matching may be involved in mother-offspring recognition. Here, we generated and analysed comparable chemical data from a non-overlapping sample of 50 mother-offspring pairs from the same two colonies five years later. The original results were corroborated in both hypothesis testing and estimation contexts, with p-values remaining highly significant and effect sizes, standardized between studies by bootstrapping the chemical data over individuals, being of comparable magnitude. We furthermore expanded the geographic coverage of our study to include pups from a total of six colonies around Bird Island. Significant chemical differences were observed in the majority of pairwise comparisons, indicating not only that patterns of colony membership persist over time, but also that chemical signatures are colony-specific in general. Our study systematically confirms and extends our previous findings, while also implying that temporal and spatial heterogeneity need not necessarily negate the reproduction and generalization of ecological research findings.

Intergenerational Effects of Early Life Starvation on Life-History, Consumption, and Transcriptomes of a Holometabolous Insect

Abstract: Intergenerational effects, also known as parental effects in which the offspring phenotype is influenced by the parental phenotype, can occur in response to parental early life food-limitation and adult reproductive environment. However, little is known about how these parental life stage-specific environments interact with each other and with the offspring environment to influence offspring phenotype, particularly in organisms that realize distinct niches across ontogeny. We examined the effects of parental early life starvation and adult reproductive environment on offspring traits under matching or mismatching offspring early life starvation conditions using the holometabolous, haplo-diploid insect Athalia rosae (turnip sawfly). We show that the parental early life starvation treatment had context-dependent intergenerational effects on the life-history and consumption traits of offspring larvae, partly in interaction with offspring conditions and sex, while there was no significant effect of parental adult reproductive environment. In addition, while offspring larval starvation led to numerous gene- and pathway-level expression differences, parental starvation impacted fewer genes and only the ribosomal pathway. Our findings reveal that parental starvation evokes complex intergenerational effects on offspring life-history traits, consumption patterns as well as gene expression, although the effects are less pronounced than those of offspring starvation.

Semaphorin3A induces nerve regeneration in the adult cornea-a switch from its repulsive role in development.

Abstract: The peripheral sensory nerves that innervate the cornea can be easily damaged by trauma, surgery, infection or diabetes. Several growth factors and axon guidance molecules, such as Semaphorin3A (Sema3A) are upregulated upon cornea injury. Nerves can regenerate after injury but do not recover their original density and patterning. Sema3A is a well known axon guidance and growth cone repellent protein during development, however its role in adult cornea nerve regeneration remains undetermined. Here we investigated the neuro-regenerative potential of Sema3A on adult peripheral nervous system neurons such as those that innervate the cornea. First, we examined the gene expression profile of the Semaphorin class 3 family members and found that all are expressed in the cornea. However, upon cornea injury there is a fast increase in Sema3A expression. We then corroborated that Sema3A totally abolished the growth promoting effect of nerve growth factor (NGF) on embryonic neurons and observed signs of growth cone collapse and axonal retraction after 30 min of Sema3A addition. However, in adult isolated trigeminal ganglia or dorsal root ganglia neurons, Sema3A did not inhibited the NGF-induced neuronal growth. Furthermore, adult neurons treated with Sema3A alone produced similar neuronal growth to cells treated with NGF and the length of the neurites and branching was comparable between both treatments. These effects were replicated in vivo, where thy1-YFP neurofluorescent mice subjected to cornea epithelium debridement and receiving intrastromal pellet implantation containing Sema3A showed increased corneal nerve regeneration than those receiving pellets with vehicle. In adult PNS neurons, Sema3A is a potent inducer of neuronal growth in vitro and cornea nerve regeneration in vivo. Our data indicates a functional switch for the role of Sema3A in PNS neurons where the well-described repulsive role during development changes to a growth promoting effect during adulthood. The high expression of Sema3A in the normal and injured adult corneas could be related to its role as a growth factor.

From plants to herbivores: novel insights into the ecological and evolutionary consequences of plant variation.

Abstract: Individuals differ! This observation goes already back to Aristotle almost 2500 years ago, but individual differences are nowadays still highlighted in various areas of social and natural sciences. Almost every day, new fascinating layers of this variation, with their intriguing causes and consequences for species interactions, are discovered. Likewise, variation within and among plant individuals and across landscapes are critical for plant–herbivore interactions, but not fully explored. Microor macro-scale spatial heterogeneity in the abiotic and biotic environment can generate significant withinand among-plant variation (e.g., Schaeffer et al. 2018), and recent studies have provided novel insights into how plant chemistry impacts herbivores, microbes and natural enemies (Albrectsen et al. 2018; Calf et al. 2018; Coley et al. 2018; Cuny et al. 2018). Moreover, the effects of plant chemical traits are often considered in isolation, but they may act together with other features of growth and defense to form distinct trait combinations or syndromes (Coley et al. 2018; Kergunteuil et al. 2018; Tewes and Müller 2018). Yet it is important not to just focus on plant traits, as environmental change such as habitat fragmentation and climate change also alter the relative abundances of herbivores and predators (van der Putten 2012; Genua et al. 2017). In this special topic, stimulated by the Plant–Herbivore Interactions Gordon Conference of 2017, we invited a series of reviews and empirical studies that build on recent advances to examine the drivers and importance of variation within and among plants at the microand macro-scale for the interactions among plants, herbivores and other organisms. The studies of this special topic cover a broad range of plant life forms, from marine algae in an aquatic system (Ledet et al. 2018) to terrestrial herbs (Calf et al. 2018; Chiriboga et al. 2018; Cuny et al. 2018; Howard et al. 2018; Humphrey et al. 2018; Kergunteuil et al. 2018; Quintero and Bowers 2018), to shrubs (Nell et al. 2018; Ochoa-López et al. 2018), to long-lived trees (Albrectsen et al. 2018; Bagchi et al. 2018; Cipollini and Peterson 2018; Coley et al. 2018; Falk et al. 2018; Lämke and Unsicker 2018). In twelve case studies and four review papers, selected aspects of the huge variation in phenomena and underlying mechanisms are highlighted and new research questions opened, which may inspire further research in this exciting field. Below we highlight some of the key findings of these papers.

Introduced populations of the garden lupine are adapted to local generalist snails but have lost alkaloid diversity

Abstract: Intraspecific variation in growth and defence among plant populations can be driven by differences in (a)biotic conditions, such as herbivory and resources. Introduction of species to novel environments affects simultaneously herbivory encountered by a plant and resource availability both directly and via altered competitive environment. Here, we address the question of how growth (leaf mass per area (LMA), plant size) and resistance traits (leaf alkaloids, leaf trichomes, resistance to a generalist snail) vary and covary between native and introduced populations of the garden lupine, Lupinus polyphyllus. We focused specifically on evolved differences among populations by measuring traits from plants grown from seed in a common environment. Plants from the introduced populations were more resistant against the generalist snail, Arianta arbustorum, and they had more leaf trichomes and higher LMA than plants from the native populations. The composition of alkaloids differed between native and introduced populations, with the native populations having more diversity in alkaloids among them. Resistance was positively associated with plant size and LMA across all populations. Other trait associations differed between native and introduced areas, implying that certain trade-offs may be fundamentally different between native and introduced populations. Our results suggest that, for the introduced populations, the loss of native herbivores and the alterations in resource availability have led to a lower diversity in leaf alkaloids among populations and may facilitate the evolution of novel trait optima without compensatory trade-offs. Such phytochemical similarity among introduced populations provides novel insights into mechanisms promoting successful plant invasions.

Soil microbiota explain differences in herbivore resistance between native and invasive populations of a perennial herb

Abstract: Soil microbiota can either slow down or facilitate plant invasions through their effects on plant performance. Associations with soil microbiota can also modify other plant traits such as herbivore resistance, which can indirectly affect the outcome of plant introductions. We studied the effects of soil microbiota on the perennial herbaceous legume Lupinus polyphyllus that hosts nitrogen‐fixing mutualistic bacteria. We compared the plant performance, herbivore resistance and volatile organic compounds (VOCs) of plants from native (North American) and invasive (Finnish) populations of the species that were inoculated with intact or autoclaved soil from an invasive population. We found that plants of both origins greatly benefited from the intact soil inoculum with respect to all performance measures considered, suggesting that beneficial nitrogen‐fixing rhizobia in the soil play a major role in shaping plant phenotypes. For three traits, effects of the intact soil inoculum were stronger in plants of native origin than in plants of invasive origin (number of leaves, herbivore resistance and total biomass). With the intact soil inoculum, plants of invasive origin were more resistant to snails than plants of native origin. Strikingly, differences in resistance to snails between plants of different origins disappeared entirely when soil microbes were reduced. Soil inoculum treatment altered the composition of the leaf VOC bouquet similarly regardless of plant origin. Synthesis. These results demonstrate the ability of Lupinus polyphyllus to associate with and benefit from putatively novel soil microbiota including rhizobia, which has likely contributed to its invasion success. Furthermore, it appears that the invasive populations have adapted to be less reliant on their symbionts, which further facilitates species spread. To our knowledge, this is the first study to demonstrate that differences in herbivore resistance between native and invasive plant populations of the same species can depend entirely on soil microbiota.

Interactions of Bunias orientalis plant chemotypes and fungal pathogens with different host specificity in vivo and in vitro

Abstract: Within several plant species, a high variation in the composition of particular defence metabolites can be found, forming distinct chemotypes. Such chemotypes show different effects on specialist and generalist plant enemies, whereby studies examining interactions with pathogens are underrepresented. We aimed to determine factors mediating the interaction of two chemotypes of Bunias orientalis (Brassicaceae) with two plant pathogenic fungal species of different host range, Alternaria brassicae (narrow host range = specialist) and Botrytis cinerea (broad host-range = generalist) using a combination of controlled bioassays. We found that the specialist, but not the generalist, was sensitive to differences between plant chemotypes in vivo and in vitro. The specialist fungus was more virulent (measured as leaf water loss) on one chemotype in vivo without differing in biomass produced during infection, while extracts from the same chemotype caused strong growth inhibition in that species in vitro. Furthermore, fractions of extracts from B. orientalis had divergent in vitro effects on the specialist versus the generalist, supporting presumed adaptations to certain compound classes. This study underlines the necessity to combine various experimental approaches to elucidate the complex interplay between plants and different pathogens.