Biology subjects

Kollross, J.

Publications and source records attributed to Kollross, J..

3 recordsLinked to original sources

bioRxiv2026

Contrasting signatures of interspecific gene flow in the Atlantic Forest endemic butterfly Heliconius besckei

Gene flow between diverging species can reshuffle genomic variation and greatly influence the speciation process, sometimes reinforcing, sometimes eroding species boundaries. However, the effect of ecological and historical processes on the patterns of introgression remains poorly understood. Here, we focus on the evolutionary history of Heliconius besckei, a geographically restricted butterfly endemic to the Brazilian Atlantic Forest, together with the mimetic H. melpomene nanna, the sympatric non-mimetic H. ethilla narcaea, and its closely related H. numata robigus. Using whole-genome sequencing, genome-wide tests of introgression, demographic modelling and palaeoclimatic species distribution models, we tested the extent and timing of interspecific gene flow in relation to mimicry, ecological context, and changes in geographic overlap. Despite strong genomic differentiation among the four focal Heliconius species, we detected widespread signatures of interspecific gene flow, greatly influenced by geographical overlap. Demographic models including post-divergence gene flow were better supported than strict-isolation models. In addition, genome-wide introgression analyses showed more numerous and larger candidate introgressed regions between H. besckei and H. ethilla narcaea, consistent with recurrent opportunities for exchange between these currently sympatric species. Species distribution models further recovered repeated expansions of suitable habitat for H. besckei during cold periods, providing a potential geographic context for secondary contact within the Atlantic Forest. Together, our results reveal recurrent gene flow occurring under different temporal, geographic, and potentially selective contexts, and show that the evolutionary history of a geographically restricted lineage can be shaped by repeated genetic exchange while substantial species differentiation is maintained.

evolutionary biology↗

bioRxiv2023

Insectivorous birds and bats outperform ants in the top-down regulation of arthropods across strata of a Japanese temperate forest

O_LIBirds, bats, and ants are recognized as significant arthropod predators. However, empirical studies reveal inconsistent trends in their relative roles in top-down control across strata. Here, we describe the differences between forest strata in the separate effects of birds, bats, and ants on arthropod communities and their cascading effects on plant damage. C_LIO_LIWe implemented a factorial design to exclude vertebrates and ants in both the canopy and understory. Additionally, we separately excluded birds and bats from the understory using diurnal and nocturnal exclosures. At the end of the experiments, we collected all arthropods and assessed herbivory damage. C_LIO_LIArthropods responded similarly to predator exclusion across forest strata, with a density increase of 81% on trees without vertebrates and 53% without both vertebrates and ants. Additionally, bird exclusion alone led to an 89% increase in arthropod density, while bat exclusion resulted in a 63% increase. Herbivory increased by 42% when vertebrates were excluded and by 35% when both vertebrates and ants were excluded. Bird exclusion alone increased herbivory damage by 28%, while the exclusion of bats showed a detectable but non-significant increase (by 22%). In contrast, ant exclusion had no significant effect on arthropod density or herbivory damage across strata. C_LIO_LIOur results reveal that the effects of birds and bats on arthropod density and herbivory damage are similar between the forest canopy and understory in this temperate forest. In addition, ants were not found to be significant predators in our system. Furthermore, birds, bats, and ants appeared to exhibit antagonistic relationships in influencing arthropod density. These findings highlight, unprecedentedly, the equal importance of birds and bats in maintaining ecological balance across different strata of a temperate forest. C_LI

ecology↗

bioRxiv2022

Nonlethal effects of predation: Presence of insectivorous birds affects the behaviour and level of stress in insects

Insect exposure to their predators can affect individuals and community processes, through direct consumption or nonlethal (i.e., nonconsumptive) effects. However, the links between behavioural and physiological responses and stimuli needed for development of the fear are not clear. We therefore subjected the desert locusts (Schistocerca gregaria) to three nonlethal treatments, using the great tits (Parus major) as a potential predator. The treatments involved: (1) bird - presence of a live great tit and its calls, (2) call - great tit calls only, (3) control - without any treatment. In the first behavioural laboratory experiment, hungry locusts were kept in an experimental cage with a shelter and food on opposite sides of the cage. The duration of hiding and feeding were considered as an indicator of fear responses. In the second laboratory experiment with the same three treatments, levels of the adipokinetic hormone (AKH) were evaluated in the central nervous system (CNS) and haemolymph. In the third experiment in an outdoor aviary, birds were free to fly in larger distances from locusts, before hormone levels were measured as response to bird and control treatments. In the first behavioural experiment, the presence of tits and their call resulted in significantly longer hiding time and significantly shorter feeding time than in the call/control treatments. The proximity of birds and locusts in the laboratory experiment elicited a significant increase in the AKH levels in the CNS and haemolymph as compared to the call/control treatments. In the outdoor experiment, the AKH levels were significantly higher in the CNS of locusts exposed to the bird than to control; no difference was recorded in their haemolymph. We showed that predator exposure quickly affected behavioural responses and physiological processes of locusts. Playback of the avian calls was not an appropriate stimulus to induce stress responses in desert locusts.

animal behavior and cognition↗