Biology subjects

Metali, F.

Publications and source records attributed to Metali, F..

5 recordsLinked to original sources

bioRxiv2026

Regulation of pitcher fluid volume and properties in six ecologically distinct Bornean Nepenthes species

Carnivorous Nepenthes plants capture and digest prey in fluid-filled pitchers, whose fluid level is subject to fluctuations caused by rain and evaporation. It was found that N. rafflesiana pitchers can reduce these fluctuations by regulating their fluid volume and composition. Here, we investigate whether and to what extent this ability occurs in other Nepenthes species varying in morphology, trapping mechanisms, habitat, lifespan and nutrient sources. We hypothesised that species more exposed to fluid level fluctuations or relying more on fluid for prey capture would exhibit more intensive regulation. In six Bornean Nepenthes species, we quantified the effect of pitcher fluid level on prey-capture efficiency, the natural fluctuations in fluid volume, and the plants response to manipulations of the fluids volume, concentration and pH. The prey capture of Nepenthes species depended to varying degrees on the pitcher fluid level: in species with waxy inner walls, capture efficiency decreased at high fluid levels, as prey could escape easily. In contrast, species with wax-free walls and steep peristomes retained prey efficiently, regardless of fluid level. Although all Nepenthes species were able to secrete and absorb water and electrolytes, the regulation rate varied considerably. The rates of the various secretion and absorption processes (concentration/volume-dependent rates of electrolyte/water transport) were positively correlated with one another, suggesting that they all depend on the activity of the pitcher glandular epithelium. While differences and similarities in fluid regulation may be partly due to phylogeny, the observed species differences can also be explained by the pitchers trapping mechanisms and ecological factors. We found weaker regulation in Nepenthes species growing in sheltered understorey habitats, and in species utilising alternative nutrient sources, which may reduce their reliance on pitcher fluid. Our study highlights the diversity of ecological strategies in pitcher plants and demonstrates how these are influenced by environmental conditions. Lay SummaryNepenthes pitcher plants have fluid-filled pitchers to capture and digest prey. Can they control the volume and composition of their fluids? We found that all six species studied regulated their fluids, but to varying degrees. Species differences can be explained by the plants habitat, pitcher morphology and nutrient acquisition strategies.

Plant Biology↗

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↗

bioRxiv2017

Sex-determination and sex chromosomes are shared across the radiation of dioecious Nepenthes pitcher plants

Plants with separate sexes (dioecy) represent a minority but dioecy has evolved multiple times independently in plants. Our understanding of sex determination systems in plants and of the ecological factors and molecular changes associated with the evolution of dioecy remain limited. Here, we study the sex-determination system in dioecious plants that lack heteromorphic sex chromosomes and are not amenable to controlled breeding: Nepenthes pitcher plants. We genotyped wild populations of flowering males and females of three Nepenthes taxa using ddRAD-seq, and sequenced a male inflorescence transcriptome. We developed a novel statistical tool (privacy rarefaction) to distinguish true sex-specificity from stochastic noise in high-throughput sequencing data. Our results support XY-systems in all three Nepenthes taxa and in Silene latifolia which was used as a positive control for its known XY-system. The male-specific region of the Y chromosome showed little conservation among the three Nepenthes taxa, except for the essential pollen development gene DYT1 which was also male-specific in additional taxa. Hence, this homomorphic XY sex-determination system likely has a unique origin older than the crown of the genus Nepenthes at c. 17.7 My. In addition to the characterisation of the previously unknown sex chromosomes of Nepenthes, our work contributes an innovative, highly sensitive statistical method to efficiently detect sex-specific genomic regions in wild populations in general.

evolutionary biology↗