Biology subjects

Vranken, N.

Publications and source records attributed to Vranken, N..

4 recordsLinked to original sources

bioRxiv2025

African Cichlid Lake Radiations Recapitulate Riverine Axial Morphologies Through Repeated Exploration of Morphospace

Macroevolutionary theory predicts that adaptive radiations are characterised by early bursts of trait evolution followed by rate slowdowns as ecological niches are filled. However, these dynamics are rarely detected within individual clades. Here, we test whether this discrepancy arises from limited temporal sampling by comparing replicated adaptive radiations of African cichlids spanning distinct evolutionary timescales. We show that the net rates of vertebral count evolution are inversely correlated with radiation age, consistent with early burst dynamics. However, we do not detect this pattern within the individual systems. We also find evidence of changes to the underlying processes that generate disparity across the timescale of adaptive radiation, signalled by increasing importance of phylogenetic signal with radiation age. This suggests that early phenotypic expansion is both rapid and phylogenetically unstructured, but that stabilising dynamics emerge on longer timescales, amid declining rates. Despite rapid phenotypic diversification, lacustrine lineages occupy only a subset of the broader morphospace of riverine taxa, suggesting that diversification over short timescales is constrained and may largely resample the variation already present in older lineages. Our results provide strong evidence for shifting evolutionary dynamics through time in adaptive radiations, and that the apparent rarity of early-burst signals in comparative analyses may partly reflect limited statistical power due to narrow temporal sampling.

evolutionary biology↗

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↗

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

Genomic consequences of domestication of the Siamese fighting fish

Siamese fighting fish, commonly known as betta, are among the worlds most popular and morphologically diverse pet fish, but the genetic processes leading to their domestication and phenotypic diversification are largely unknown. We assembled de novo the genome of a wild Betta splendens and whole-genome sequenced multiple individuals across five species within the B. splendens species complex, including wild populations and domesticated ornamental betta. Given our estimate of the mutation rate from pedigrees, our analyses suggest that betta were domesticated at least 1,000 years ago, centuries earlier than previously thought. Ornamental betta individuals have variable contributions from other Betta species and have also introgressed into wild populations of those species. We identify dmrt1 as the main sex determination gene in ornamental betta but not in wild B. splendens, and find evidence for recent directional selection at the X-allele of the locus. Furthermore, we find genes with signatures of recent, strong selection that have large effects on color in specific parts of the body, or the shape of individual fins, and are almost all unlinked. Our results demonstrate how simple genetic architectures paired with anatomical modularity can lead to vast phenotypic diversity generated during animal domestication, and set the stage for using betta as a modern system for evolutionary genetics. One-Sentence SummaryGenomic analyses reveal betta fish were domesticated more than 1,000 years ago and the genes that changed in the process.

evolutionary biology↗