Biology subjects

Van Steenberge, M.

Publications and source records attributed to Van Steenberge, M..

5 recordsLinked to original sources

bioRxiv2024

Worms of change: anthropogenic disturbance changes the ectoparasite community structure of Lake Victoria cichlids

Host-parasite interactions increase the complexity, and thus robustness and resilience, of an ecosystem. This role is particularly relevant in times of global change. Environmental changes cause biodiversity loss and shifts in community compositions of free-living organisms, but how these changes affect parasite communities is still unclear. We tested how parasites respond to anthropogenic perturbations, using the case of Lake Victoria (East Africa), after 40 years of their onset. Lake Victoria experienced multiple human-induced invasions (e.g. Nile perch) and eutrophication that heavily affected haplochromine cichlid fishes (whose species richness decreased from 500 to 250 species in a decade). We compared gill macroparasite communities of 13 haplochromine species before and after perturbations, using historical and recent fish collections. The host-parasite network re-arranged, with few emerging and few disappearing host-parasite combinations, in a way that reduced stability. The host range of parasites, which is linked to resilience ability, decreased and thus we expect a decreased resilience ability in the future. We also found a decrease in infection parameters, co-infection occurrence, and biodiversity indices highlighting the urgent need of a conservation plan for wildlife parasites, to preserve their ecosystem services in face of global change. This study serves as a proof-of-concept of how often-overlooked aspects of host-parasite interactions provide a tool to monitor the health status of an ecosystem.

ecology↗

bioRxiv2023

Lifestyle and not density of fish hosts determines parasite distribution over time and space

Despite their important ecological role, questions remain on mechanisms structuring parasite assemblages. We present a simple and endemic host-parasite system of clupeid fishes and monogenean parasites (Kapentagyrus, Dactylogyridae) with contrasting levels of host-specificity from Lake Tanganyika as a model to study parasite distribution patterns and co-infection dynamics in nature. With two parasites, two host species, and three host-parasite combinations between them, this unique system represents the simplest natural host-parasite model that is not trivial. We modelled spatiotemporal dynamics of host-parasite interaction using infection data along the North-South axis of Lake Tanganyika (660 km) over the course of two seasons and four years (1730 fish, 3710 parasites). We found temporal stability of infection, which contrasts with previously reported seasonally driven fluctuations of fish host abundances. We found a difference in spatial structure between the parasite species, confirming that their distributions are only restricted by their most mobile host species. On the host species that is infected by two parasite species, we discovered a positive correlation with host body size for one parasite species, and a negative correlation for the other species. As we also discovered facilitation of infection, this cannot be due to competition. The differences reported between parasite species infecting the same host species further extrapolate the dependence on changes in lifestyle of the host during its ontogenetic development. In conclusion, we show that in a simple, closed system parasite infection dynamics are dependent on a combination of host mobility, host lifestyle changes over ontogenetic development and interspecific interactions between parasites.

ecology↗

bioRxiv2022

Intraspecific diversification and mitonuclear discordance in native versus introduced areas: co-introduction of Dolicirroplectanum lacustre, a monogenean gill parasite of the invasive Nile perch Lates niloticus

The Nile perch (Lates niloticus) is a notorious invasive species. The introductions of Nile perch into several lakes and rivers in the Lake Victoria region led to the impoverishment of the trophic food webs, particularly well documented in Lake Victoria. Along with the introductions of the Nile perch, its parasites were co-introduced. Dolicirroplectanum lacustre (Monogenea, Diplectanidae) is a gill parasite of latid fishes (Lates spp.) inhabiting several major African freshwater systems. We examined the intra-specific diversification of D. lacustre from L. niloticus in Lake Albert (native range) and Lake Victoria (introduced range) by assessing morphological and genetic differentiation, and microhabitat preference. We expected reduced morphological and genetic diversity for D. lacustre in Lake Victoria compared to Lake Albert, as a result of the historical introductions. Dolicirroplectanum lacustre displays high morphological variability within and between African freshwaters. Mitonuclear discordance within the morphotypes of D. lacustre indicates an incomplete reproductive barrier between the morphotypes. The diversification in the mitochondrial gene portion is directly linked with the morphotypes, while the nuclear gene portions indicate conspecificity. Based on our results, we reported reduced genetic and morphological diversity, potentially being a result of a founder effect in Lake Victoria.

evolutionary biology↗

bioRxiv2021

The initial response of females towards congeneric males matches the propensity to hybridize in Ophthalmotilapia.

AO_SCPLOWBSTRACTC_SCPLOWCichlid radiations often harbour closely related species with overlapping niches and distribution ranges. Such species sometimes hybridise in nature, which raises the question how can they coexist. This also holds for the Tanganyika mouthbrooders Ophthalmotilapia ventralis and O. nasuta. Earlier studies found indications of asymmetrical hybridisation with females of O. ventralis accepting males of O. nasuta, but not the other way around. We hypothesised that this was due to differences in the capacity for species recognition. Given the higher propensity of O. ventralis females towards hybridisation, we expect a reduced ability for species recognition in O. ventralis females, compared to O. nasuta females. We staged two experiments, one focusing on 22 female O. nasuta and one on 21 female O. ventralis. These fish were placed in one half of a tank and briefly exposed to a conspecific or a heterospecific male, a conspecific female, or nothing (control). Female response was evaluated by scoring six tracking parameters and by noting the occurrence of ten discrete behaviours before and during the encounter. Females always responded to the presence of another fish by approaching it. Remarkably, for both O. nasuta and O. ventralis, we did not find a different response between encounters with conspecific males and females. However, in agreement with our hypothesis, O. nasuta females behaved differently towards conspecific or heterospecific males, whereas O. ventralis females did not. When presented with a heterospecific male, O. nasuta females performed a lower number of ram behaviours. Additionally, they never displayed the flee behaviour, a component of the species mating repertoire that was seen in all but one of the presentations with a conspecific male. Our findings show that differences in species recognition at first encounter predict to a large degree the outcome of the mating process, even in the absence of mating behaviour.

animal behavior and cognition↗

bioRxiv2021

Somewhere I Belong: Phylogenetic Comparative Methods and Machine Learning to Investigate the Evolution of a Species-Rich Lineage of Parasites

AO_SCPLOWBSTRACTC_SCPLOWA substantial portion of biodiversity evolved through adaptive radiation. However, the effects of explosive speciation on species interactions remain poorly understood. Metazoan parasites infecting radiating host lineages could improve our knowledge because of their intimate host relationships. Yet limited molecular, phenotypic, and ecological data discourage multivariate analyses of evolutionary patterns and encourage the use of discrete characters. Here, we assemble new molecular, morphological, and host range data widely inferred from a species-rich lineage of parasites (Cichlidogyrus, Platyhelminthes: Monogenea) infecting cichlid fishes to address data scarcity. We infer a multi-marker (28S/18S rDNA, ITS1, COI mtDNA) phylogeny of 58/137 species and characterise major lineages through synapomorphies inferred from mapping morphological characters. We predict the phylogenetic position of species without DNA data through shared character states, a combined molecular-morphological phylogenetic analysis, and a classification analysis with support vector machines. Based on these predictions and a cluster analysis, we assess the systematic informativeness of continuous characters, search for continuous equivalents for discrete characters, and suggest new characters for morphological traits not analysed to date. We also model the attachment/reproductive organ and host range evolution using the data of 136/137 described species and multivariate phylogenetic comparative methods (PCMs). We show that discrete characters can mask phylogenetic signals but can be key for characterising species groups. Regarding the attachment organ morphology, a divergent evolutionary regime for at least one lineage was detected and a limited morphological variation indicates host and environmental parameters affecting its evolution. However, moderate success in predicting phylogenetic positions, and a low systematic informativeness and high multicollinearity of morphological characters call for a revaluation of characters included in species characterisations.

evolutionary biology↗