Joost Raeymaekers

Nord University | HIBO · Faculty of Biosciences and Aquaculture

Geographical isolation, habitat variation and trophic specialisation have contributed to a large extent to the astonishing diversity of cichlid fishes in the Great East African lakes. Because parasite communities often vary across space and environments, parasites can accompany and potentially enhance cichlid species diversification. However, host...

Adaptive radiation occurs when species diversify rapidly to occupy an array of ecological niches. Since opportunities for parasite infection and transmission may greatly vary among these niches, adaptive radiation is expected to be associated with a turnover of the parasite community. As major agents of natural and sexual selection, parasites may p...

Genes with major phenotypic effects facilitate quantifying the contribution of genetic vs. plastic effects to adaptive divergence. A classical example is Ectodysplasin (Eda), the major gene controlling lateral plate phenotype in three-spined stickleback. Completely plated marine stickleback populations evolved repeatedly towards low-plated freshwat...

An increase in biological diversity leads to a greater stability of ecosystem properties. For host-parasite interactions, this is illustrated by the 'dilution effect': a negative correlation between host biodiversity and disease risk. We show that a similar mechanism might stabilise host-parasite dynamics at a lower level of diversity, i.e. at the...

Adaptive radiation unfolds as selection acts on the genetic variation underlying functional traits. The nature of this variation can be revealed by studying the tips of an ongoing adaptive radiation. We studied genomic variation at the tips of the Darwin's finch radiation; specifically focusing on polymorphism within, and variation among, three sym...

Embryonic temperature has a lasting impact on muscle phenotype in vertebrates, involving complex molecular mechanisms that encompass both protein-coding and non-coding genes. Circular RNAs (circRNAs) are a class of regulatory RNAs that play important roles in various biological processes, but the effect of variable thermal conditions on the circRNA...

The analysis of growth parameters in fish stocks, such as the asymptotic length (L∞) and the curvature parameter (K), is crucial for the estimation of production rates and total mortality rates in fisheries management. Here, we estimated the growth parameters of the clupeids Limnothrissa miodon and Stolothrissa tanganicae in the northern part of La...

Background Thyasirid bivalves are often recorded as a dominant component of macrobenthic infaunal communities in depositional environments such as fjord basins. Fjord basins comprise patchy soft-bottom habitats bounded by steep walls and sills; however, little is known how this semi-isolated nature of fjords affects benthic populations. Accordingly...

Mercury can be very toxic at low environmental concentrations by impairing immunological, neurological, and other vital pathways in humans and animals. Aquatic ecosystems are heavily impacted by mercury pollution, with evidence of biomagnification through the food web. We examined the effect of mercury toxicity on the spleen, one of the primary imm...

The analysis of growth parameters in fish stocks, such as the asymptotic length (Linf) and the curvature parameter (K) is crucial for the estimation of production rates and total mortality rates in fisheries management. Here, we estimated the growth parameters of the clupeids Limnothrissa miodon and Stolothrissa tanganicae in the northern part of L...

Genetic monitoring of populations currently attracts interest in the context of the Convention on Biological Diversity but needs long-term planning and investments. However, genetic diversity has been largely neglected in biodiversity monitoring, and when addressed, it is treated separately, detached from other conservation issues, such as habitat...

Host-associated microbiota can influence host phenotypic variation, fitness and potential to adapt to local environmental conditions. In turn, both host evolutionary history and the abiotic and biotic environment can influence the diversity and composition of microbiota. Yet, to what extent environmental and host-specific factors drive microbial di...

Divergent natural selection should lead to adaptive radiation - that is, the rapid evolution of phenotypic and ecological diversity originating from a single clade. The drivers of adaptive radiations have often been conceptualized through the concept of "adaptive landscapes"; yet formal empirical estimates of adaptive landscapes for natural adaptiv...

The Norwegian Scientific Committee for Food and Environment (Vitenskapskomiteen for mat og miljø, VKM) appointed a project group to draft the opinion. The project group consisted of 4 VKM members and 2 VKM staff. Two referees commented on and reviewed the draft opinion. The Committee, by the Panel on CITES, assessed and approved the final opinion.

In comparison with traditional lectures, active learning methods have the potential to foster learner agency and consequently raise academic performance. However, these methods are often applied with little knowledge about their effectiveness. In this study, we introduced two concept maps in an undergraduate cell biology course, to investigate thei...

Background Circular RNAs (circRNAs) are covalently closed-loop RNAs with critical regulatory roles in cells. Tens of thousands of circRNAs have been unveiled due to the recent advances in high throughput RNA sequencing technologies and bioinformatic tools development. At the same time, polymerase chain reaction (PCR) cross-validation for circRNAs p...

Muscle growth in teleosts is a complex biological process orchestrated by numerous protein-coding genes and non-coding RNAs. A few recent studies suggest that circRNAs are involved in teleost myogenesis, but the molecular networks involved remain poorly understood. In this study, an integrative omics approach was used to determine myogenic circRNAs...

Muscle growth in teleosts is a complex biological process orchestrated by numerous protein-coding genes and non-coding RNAs. A few recent studies suggest that circRNAs are involved in teleost myogenesis, but the molecular networks involved remain poorly understood. In this study, an integrative omics approach was used to determine myogenic circRNAs...

The conservation of biodiversity from the genetic to the community levels is fundamental for the continual provision of ecosystem services (ES), the benefits that ecosystems provide to people. Genetic and genomic diversity enhance the resilience of populations and communities that underpin the provision of ecosystem functions and services. We show...

Background: Circular RNAs (circRNAs) are covalently closed-loop RNAs with critical regulatory roles in cells. The tenth of thousands of circRNAs have been unveiled due to the recent advances in high throughput RNA sequencing technologies and bioinformatic tools development. At the same time, polymerase chain reaction (PCR) cross-validation for circ...

Habitat fragmentation impacts the distribution of genetic diversity and population genetic structure. Therefore protecting the evolutionary potential of species, especially in the context of the current rate of human‐induced environmental change, is an important goal. In riverine ecosystems, migration barriers affect the genetic structure of native...

Background The hydrogeological history of Lake Tanganyika paints a complex image of several colonization and adaptive radiation events. The initial basin was formed around 9–12 million years ago (MYA) from the predecessor of the Malagarasi–Congo River and only 5–6 MYA, its sub-basins fused to produce the clear, deep waters of today. Next to the wel...

The term terroir is used in viticulture to emphasize how the biotic and abiotic characteristics of a local site influence grape physiology and thus the properties of wine. In ecology and evolution, such terroir (i.e., the effect of space or "site") is expected to play an important role in shaping phenotypic traits. Just how important is the pure sp...

Background The hydro-geological history of Lake Tanganyika paints a complex image of several colonization and adaptive radiation events. The initial basin was formed around 9-12 million years ago (MYA) from the predecessor of the Malagarasi–Congo River and only 5-6 MYA, its sub-basins fused to produce the clear, deep waters of today. Next to the we...

How parasites alter host feeding ecology remains elusive in natural populations. A powerful approach to investigate the link between infection and feeding ecology is quantifying unique and shared responses to parasite infection in related host species within a common environment. Here, 9 pairs of sympatric populations of the three-spined and nine-s...

Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban...

Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban...

Knowledge on the reproductive biology of the endemic clupeids Limnothrissa miodon and Stolothrissa tanganicae, two main target species of the pelagic fisheries of Lake Tanganyika, is constrained by fragmented monitoring activities. Here, we investigate the nursing areas of L. miodon, the timing of reproductive activities of littoral and pelagic L....

Understanding why certain host species harbor more parasites is an important question in parasite and fish ecology. Parasite infection among sympatric species may integrate various processes affecting parasite assembly, including the species-specific ecology and the success of invaders. We focused on spatial, environmental, and host-related determi...

Global warming challenges the persistence of local populations, not only through heat‐induced stress, but also through indirect biotic changes. We study the interactive effects of temperature, competition and parasitism in the water flea Daphnia magna. We carried out a common garden experiment monitoring the dynamics of Daphnia populations along a...

Anthropogenic stressors, such as pollutants, act as selective factors that can leave measurable changes in allele frequencies in the genome. Metals are of particular concern among pollutants, because of interference with vital biological pathways. We use the three‐spined stickleback as a model for adaptation to mercury pollution in natural populati...

• An optimal timing for diapause induction through the sexual production of dormant propagules is expected in organisms with temporary populations. Yet, empirical studies often find high within-population genetic variation in the sexual production of such propagules, suggesting that this is a common feature of such organisms. • Here, we hypothesize...

We lack a thorough understanding of the origin and maintenance of standing genetic variation that enables rapid evolutionary responses of natural populations. Whole genome sequencing of a resurrected Daphnia population shows that standing genetic variation in over 500 genes follows an evolutionary trajectory that parallels the pronounced and rapid...

The European Union adopted the Water Framework Directive (WFD) in the year 2000 to tackle the rapid degradation of freshwater systems. However, biological, hydromorphological, and physico-chemical water quality targets are currently not met, and identifying successful policy implementation and management actions is of key importance. We built a joi...

There is a general and solid theoretical framework to explain how the interplay between natural selection and gene flow affects local adaptation. Yet, to what extent coexisting closely related species evolve collectively or show distinctive evolutionary responses remains a fundamental question. To address this, we studied the population genetic str...

The fisheries of Lake Tanganyika play an important role in food security in Central and Eastern Africa. Conservation of these valuable fish stocks will benefit from documenting the ideas, opinions and observations of stakeholders. Knowledge of the perceptions and an understanding of the concerns and struggles of stakeholders of these fisheries can...

Uncertainty hampers innovative mixed‐fisheries management by the scales at which connectivity dynamics are relevant to management objectives. The spatial scale of sustainable stock management is species‐specific and depends on ecology, life history and population connectivity. One valuable approach to understand these spatial scales is to determine...

Lake Tanganyika, East Africa, is the oldest and deepest African Great Lake and harbours one of the most diverse fish assemblages on earth. Two clupeid fishes, Limnothrissa miodon and Stolothrissa tanganicae, constitute a major part of the total fish catch, making them indispensable for local food security. Parasites have been proposed as indicators...

Sea ice loss may have dramatic consequences for population connectivity, extinction‐colonization dynamics, and even the persistence of Arctic species subject to climate change. This is of particular concern in face of additional anthropogenic stressors, such as overexploitation. In this study, we assess the population‐genetic implications of dimini...

Disruptive natural selection within populations exploiting different resources is considered to be a major driver of adaptive radiation and the production of biodiversity. Fitness functions, which describe the relationships between trait variation and fitness, can help to illuminate how this disruptive selection leads to population differentiation....

An optimal timing for diapause induction through the sexual production of dormant propagules is expected in populations of annual organisms. Yet, experimental work typically finds high within-population genetic variation in the sexual production of such propagules. Thus, high genetic variation in timing for diapause induction should be a common fea...

Connectivity between spawning and nursery grounds influences the colonization, replenishment and resilience of populations of marine organisms. Connectivity rate, measured as the exchange of individuals between spawning and nursery grounds, is therefore a crucial determinant of stock size. However, connectivity of early-life stages is hard to explo...

Differences in habitat and diet between species are often associated with morphological differences. Habitat and trophic adaptation have therefore been proposed as important drivers of speciation and adaptive radiation. Importantly, habitat and diet shifts likely impose changes in exposure to different parasites and infection risk. As strong select...

Evidence of reciprocal influences between ecological and evolutionary processes (eco‐evolutionary dynamics) is accumulating at different levels of biological organisation, ranging from populations to communities and even ecosystems. This special feature showcases the state‐of‐the art knowledge on eco‐evolutionary dynamics and dissects the feedback...

Background Clupeid fisheries in Lake Tanganyika (East Africa) provide food for millions of people in one of the world’s poorest regions. Due to climate change and overfishing, the clupeid stocks of Lake Tanganyika are declining. We investigate the population structure of the Lake Tanganyika sprat Stolothrissa tanganicae, using for the first time a...

Urbanization is influencing patterns of biological evolution in ways that are only beginning to be explored. One potential effect of urbanization is in modifying ecological resource distributions that underlie niche differences and that thus promote and maintain species diversification. Few studies have assessed such modifications, or their potenti...

Theoretical models pertaining to feedbacks between ecological and evolutionary processes are prevalent in multiple biological fields. An integrative overview is currently lacking, due to little crosstalk between the fields and the use of different methodological approaches. Here, we review a wide range of models of eco‐evolutionary feedbacks and hi...

Background Species delineation is particularly challenging in taxa with substantial intra-specific variation. In systematic studies of fishes, meristics and linear measurements that describe shape are often used to delineate species. Yet, little is known about the taxonomic value of these two types of morphological characteristics. Here, we used Tr...

Whereas Lake Tanganyika's littoral and benthic zones are famous for their diverse fish communities, its pelagic zone is dominated by few species, of which two representatives of Clupeidae (Limnothrissa miodon and Stolothrissa tanganicae) take a pivotal role. We investigated the monogenean fauna infecting these freshwater clupeids to explore the lin...