Biology subjects

Timaeus, L.

Publications and source records attributed to Timaeus, L..

3 recordsLinked to original sources

bioRxiv2025

Ecology and temporal dynamics of urban Drosophila species communities as potential indicators of biodiversity decline

Understanding the impact of ecological factors on biodiversity is central in the context of accelerating climate change and biodiversity loss. Urban areas, as landscapes under particularly strong anthropogenic influence, are undergoing rapid ecological change, yet the consequences for urban biodiversity and ecosystem functioning remain poorly understood. In this study, we focused on fruit flies of the genus Drosophila - a diverse group of dipterans with variable ecological niches and degrees of synanthropy - to investigate species composition and community ecology in the metropolitan area of Vienna, Austria. With the help of numerous citizen scientists, we have collected approximately 18,000 specimens through dense spatio-temporal sampling both indoors and outdoors of human dwellings. A total of 13 Drosophila species were identified, with communities dominated by widespread cosmopolitan synanthropic species. Among these, D. mercatorum and D. virilis represent novel records for Austria. Comparisons to a previous study from more than 30 years ago revealed that the species richness in Vienna was more than 50% lower than before and showed that formerly common species were potentially replaced by neobiots. We further assessed ecological niches by intersecting species abundance data with high-dimensional, high-resolution earth observation datasets, which revealed distinct ecological preferences among species. In particular, the neozoan D. mercatorum emerged as a highly synanthropic species, tightly confined to urban areas with high levels of imperviousness. In summary, our study underpins the versatility of the Drosophila system as indicators of biodiversity loss in a rapidly changing world.

ecology↗

bioRxiv2020

Parallel visual pathways with topographic versus non-topographic organization connect the Drosophila eyes to the central brain

One hallmark of the visual system is the strict retinotopic organization from the periphery towards the central brain, spanning multiple layers of synaptic integration. Recent Drosophila studies on the computation of distinct visual features have shown that retinotopic representation is often lost beyond the optic lobes, due to convergence of columnar neuron types onto optic glomeruli. Nevertheless, functional imaging revealed a spatially accurate representation of visual cues in the central complex (CX), raising the question how this is implemented on a circuit level. By characterizing the afferents to a specific visual glomerulus, the anterior optic tubercle (AOTU), we discovered a spatial segregation of topographic versus non-topographic projections from molecularly distinct classes of medulla projection neurons (medullo-tubercular, or MeTu neurons). Distinct classes of topographic versus non-topographic MeTus form parallel channels, terminating in separate AOTU domains. Both types then synapse onto separate matching topographic fields of tubercular-bulbar (TuBu) neurons which relay visual information towards the dendritic fields of central complex ring neurons in the bulb neuropil, where distinct bulb sectors correspond to a distinct ring domain in the ellipsoid body. Hence, peripheral topography is maintained due to stereotypic circuitry within each TuBu class, providing the structural basis for spatial representation of visual information in the central complex. Together with previous data showing rough topography of lobula projections to a different AOTU subunit, our results further highlight the AOTUs role as a prominent relay station for spatial information from the retina to the central brain.

neuroscience↗

bioRxiv2017

A topographic visual pathway into the central brain of Drosophila

The visual system is characterized by a strict topographic organization from the retina towards multiple layers of synaptic integration. Recent studies in Drosophila have shown that in the transition from the optic lobes to the central brain, due to convergence of columnar neurons onto optic glomeruli, distinct synaptic units employed in the computation of different visual features, the retinotopic representation is lost in these circuits. However, functional imaging revealed a spatial representation of visual cues in the Drosophila central complex, raising the question about the underlying circuitry, which bypasses optic glomerulus convergence.\n\nWhile characterizing afferent arborizations within Drosophila visual glomeruli, we discovered a spatial segregation of topographic and non-topographic projections from distinct molecular classes of medulla projection neurons, medullo-tubercular (MeTu) neurons, into a specific central brain glomerulus, the anterior optic tubercle (AOTu). Single cell analysis revealed that topographic information is organized by ensembles of MeTu neurons (type 1), forming parallel channels within the AOTu, while a separate class of MeTu neurons (type 2) displays convergent projection, associated with a loss of spatial resolution. MeTu afferents in the AOTu synapse onto a matching topographic field of output projection neurons, these tubercular-bulbar (TuBu) neurons relay visual information towards dendritic fields of central complex ring neurons in the bulb neuropil. Within the bulb, neuronal proximity of the topographic AOTu map as well as channel identity is maintained despite the absence of a stereotyped map organization, providing the structural basis for spatial representation of visual information in the central complex (CX). TuBu neurons project onto dendritic fields of efferent ring neurons, where distinct sectors of the bulb correspond to a distinct ring domain in the ellipsoid body. We found a stereotypic circuitry for each analyzed TuBu class, thus the individual channels of peripheral topography are maintained in the central complex structure. Together with previous data showing rough topography within the lobula AOTu domain, our results on the organization of medulla projection neurons define the AOTu neuropil as the main relay station for spatial information from the optic lobes into the central brain.

neuroscience↗