Biology subjects

Grafe, U.

Publications and source records attributed to Grafe, U..

4 recordsLinked to original sources

bioRxiv2025

Three-dimensional Tracking Method for Water-Hopping Mudskippers in Natural Habitats

We present a portable, non-invasive, and low-cost three-dimensional tracking method to quantify in situ water-hopping kinematics of mudskippers. By combining dual-camera video recordings with tracking fish path, Gaussian Splatting terrain reconstruction and epipolar geometric analysis, we capture detailed 3D trajectories of mudskippers in their natural tidal-flat habitats. Our proposed method resolves complex hopping motions, including both straight and curved escape paths, and reveals that horizontal distance, hopping height, and speed are strongly influenced by fish size and local terrain features. These results highlight both the biomechanical and ecological significance of water-hopping in mudskippers, demonstrating how a simple, deployable 3D approach can resolve complex amphibious movements in challenging field environments.

animal behavior and cognition↗

bioRxiv2025

Arms race of physical defences: Hooked trichomes of Macaranga ant-plants kill lycaenid caterpillars, but one specialist has a counter-defence

The co-evolution of insects and chemical plant defences has been described as an arms-race, but it is unclear if physical plant defences can produce similar outcomes. Here we report a previously unknown interaction from the mutualism between ants and Macaranga trees. Although Macaranga trees are well protected against herbivory by aggressive ants, caterpillars of the genus Arhopala (Lepidoptera: Lycaenidae) can feed on the leaves by appeasing the ants with nectar-like secretions. One ant-plant species, M. trachyphylla, bears hooked trichomes on its green surfaces. When placed on M. trachyphylla stems or petioles, Arhopala caterpillars associated with other Macaranga species (A. major, A. dajagaka and A. zylda) were quickly arrested by the sharp trichomes which pierced their cuticle, resulting in rapid loss of blood and death. In striking contrast, A. amphimuta caterpillars, which occur naturally on M. trachyphylla, could easily walk over the hooked trichomes without any injury. As hooked trichomes are a novel trait within Macaranga, this interaction provides an example of de novo evolution of a physical plant defence, which in turn has been overcome by a specialist herbivore. Our study suggests that physical plant defences can lead to evolutionary arms races similar to those for chemical defences.

zoology↗

bioRxiv2023

Genomic evidence for rapid speciation and gene flow between sympatric carnivorous Nepenthes pitcher plants

Speciation can result from both neutral and adaptive processes, but their relative importance and the factors exerting selective pressures are incompletely understood. In theory, interspecific gene flow could suffice to reverse speciation, or else erode neutral divergence and expose traits and underlying genes whose divergence is due to selection. Hence, introgression can shed light on selection during the speciation process. Here we study mixed assemblages of carnivorous Nepenthes pitcher plants, which frequently produce natural hybrids yet maintain distinct phenotypes. Using ddRAD-seq markers, we characterize divergence and introgression for eight Nepenthes species that grow sympatrically in communities of three to seven species at four locations in Southeast Asia, totalling 22 populations. The sympatric species fell into two discrete classes of high and low divergence. Five lineages with high divergence displayed little recent introgression in tests of location-dependent allele sharing (ABBA-BABA) despite the presence of some natural hybrids. However, all five lineages appear to have introgressed in the more distant past, as revealed by coalescent models with Approximate Bayesian Computation. In the same locations occur three further sympatric species with low genetic divergence. These incipient species also showed some natural hybrids, but in addition both ABBA-BABA tests and ABC suggested very recent or ongoing introgression, raising the question how divergence is maintained in these hybrid zones. One trait possibly involved in maintenance of divergence against gene flow might be the carnivorous pitcher traps, whose morphology showed greater divergence than expected under neutral evolution (Pst-Fst) in the introgressing species pair N. hemsleyana and N. rafflesiana t.f..

evolutionary biology↗

bioRxiv2023

Adaptive evolution of carnivory in Nepenthes pitcher plants: a comparative transcriptomics and proteomics perspective

While trait diversity associated with evolutionary radiations is easily recognized, their function and adaptive relevance often remain elusive. Here we study the evolution of carnivory genes in Nepenthes, an iconic radiation of carnivorous pitcher plants. We investigate 13 species chosen to represent the diversity of nutrient acquisition strategies, geography and climates covered by the genus. Using a combination of proteomics and transcriptomics, we discovered that Nepenthes secrete hundreds of enzymes and antimicrobial proteins into their digestive fluids. Further genes related to plant carnivory were uncovered by analyses of gene expression changes induced by experimental feeding of starved Nepenthes traps. Feeding status appears to affect the relative abundance of nearly 35% of all expressed genes, and may be accompanied by a strong physiological shift away from photosynthesis towards heterotrophy, proteolysis, and protein synthesis. Among the many thousand genes showing signatures of adaptive evolution in sequence or expression level within the Nepenthes radiation, the secreted pitcher fluid proteins and the carnivory-related genes were over-represented. A bias towards carnivory genes, and towards trap-expressed genes versus leaf-expressed genes, was also observed among the genes differing in expression in a young pair of sister species. Together, our results suggest that the molecular basis of the carnivorous syndrome was disproportionally targeted by positive selection during the Nepenthes radiation. This study demonstrates how the evolutionary relevance of putative key traits can be tested at the level of underlying genes.

evolutionary biology↗