Harmos, K. | bioRxiv Science

bioRxiv2025

Assessment of environmental variables for species distribution modelling: insights from the mosaic distribution of red- and yellow-bellied toads

Species distribution modelling can possibly be improved through the preferential use of explanatory variables that reflect the natural history features of the species being modelled. Red- and yellow-bellied toads (genus Bombina) engage in an intricate mosaic distribution across Europe. Analysing new atlas data on these species mutual distribution in Hungary with principal coordinate analysis we identified their differential ecological preferences as forested, hilly and mountainous for B. variegata and open lowland for B. bombina. These locally operating parameters we consider to be good proxies for the essential species difference which resides in breeding in ephemeral puddles (B. variegata) versus larger permanent ponds (B. bombina). With two-species distribution modelling - in which the presence of one species is contrasted with the presence of the counterpart species - we obtained excellent model fit (AUC) for climate and elevation / land cover datasets alike (AUC=0.98 versus 0.95). For both models fit values dropped upon transference to surrounding countries, yet the latter model kept significantly higher predictive power (AUC=0.91) than the climate model (AUC=0.79). Swapping elevation for hilliness as suggested in the literature had a significant negative effect on model performance. We conclude that an informed parameter selection enhances model transferability, therewith improving our understanding of species-habitat associations. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=109 SRC="FIGDIR/small/650429v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@5caa3forg.highwire.dtl.DTLVardef@1ad3857org.highwire.dtl.DTLVardef@14df970org.highwire.dtl.DTLVardef@3352ca_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIRed- and yellow-bellied toads engage in a yin-yang-like mosaic distribution across Europe. C_LIO_LISpecies differential habitat characteristics were studied with principal coordinates. C_LIO_LISpecies distribution modelling was with climate data and with landscape variables. C_LIO_LIModels produced with atlas data for Hungary were assessed over neighbouring countries. C_LIO_LITransferred models with elevation and forestation performed better than climate-based ones. C_LI

ecology↗

bioRxiv2024

Mitigation of chytrid infection on tadpoles with the antimicrobial metabolites of Xenorhabdus szentirmaii

Survival of amphibian assemblages is threatened by many factors. Among them, chytridiomycosis, the disease caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd) has great importance, also threatening the populations of the yellow-bellied toad (Bombina variegata), which has a scattered, isolated distribution in Hungary. Treatment with secondary metabolites of the entomopathogenic bacterium, Xenorhabdus szentirmaii is a promising method in the mitigation of chytridiomycosis, as recently demonstrated. To assess whether it may also be effective for lowering infection intensities in B. variegata tadpoles, we extracted cell-free culture media (CFCM) from liquid cultures of X. szentirmaii and tested their antifungal efficacy at a dilution of 0.1 % (v/v), while also measuring possible short-term malign effects on tadpoles experimentally infected with Bd or sham infection. According to our results, CFCM treatment alone did not compromise tadpoles survival probability, nor reduced the body mass and developmental speed of the individuals. At the same time, the treatment reduced the intensity and prevalence of Bd infection, but this effect was affected by the population of origin. The antimicrobial metabolites produced by X. szentirmaii may therefore be suitable for the safe mitigation of chytridiomycosis in B. variegata tadpoles, but further studies are needed, aiming to monitor and increase the efficacy of this method.

ecology↗