Biology subjects

Pardikes, N. A.

Publications and source records attributed to Pardikes, N. A..

4 recordsLinked to original sources

bioRxiv2025

Dominant species determines Drosophila-parasitoid food web dynamics and stability more strongly than complexity, warming or invasion

Ecological communities face major challenges of biodiversity loss, invasive species, and warming due to human action. Factors that determine the dynamics, stability and functioning of network of interacting species have been debated in ecology since its beginning as discipline. Community complexity and dominant (keystone) species have been proposed as the most relevant factors, however there is lack of knowledge on how these factors will interact with warming and invasion. To determine the effect of complexity, warming or invasion and their combinations on stability and functioning of a food web we performed a microcosm laboratory experiment using Drosophila-parasitoid food webs as a model. During five months, we recorded the dynamics of twelve different food webs (different combinations of flies and parasitoid species with two complexity levels) subjected to two temperature regimes (ambient and warming) and invasion or not by Drosophila suzukii in a factorial design. We did not observe any major effect of complexity or invasion. However, species composition had major effect, as webs with Drosophila simulans present were rapidly dominated by it, reducing diversity, increasing parasitism rate, reducing stability and bringing the community on the verge of collapse. Warming in turn increased diversity, overall fly population and temporal stability, while decreasing parasitism rate. Invasion of D. suzukii was not successful in any of the networks, possibly due to its low competitive ability. Our results imply that dominant species can have very strong effects on dynamics and stability, compared to food web complexity.

ecology↗

bioRxiv2021

Multiple parasitoid species enhance top-down control, but parasitoid performance is context-dependent

O_LIEcological communities are composed of many species, forming complex networks of interactions. Current environmental changes are altering community composition. We thus need to identify which aspects of species interactions are primarily driven by community structure and which by species identity to predict changes in the functioning of communities. Yet, this partitioning of effects is challenging and thus rarely explored. C_LIO_LIHere we disentangled the influence of community structure and the identity of co-occurring species on the outcome of consumer-resource interactions using a host-parasitoid system. C_LIO_LIWe used four community modules that are common in host-parasitoid communities to represent community structure (i.e., host-parasitoid, exploitative competition, alternative host, and a combination of both exploitative competition and alternative host). We assembled nine different species combinations per community module in a laboratory experiment using a pool of three Drosophila hosts and three larval parasitoid species. To investigate the potential mechanisms at play, we compared host suppression and parasitoid performance across community modules and species assemblages. C_LIO_LIWe found that multiple parasitoid species enhanced host suppression due to sampling effect, weaker interspecific than intraspecific competition between parasitoids, and synergism. However, the effects of community structure on parasitoid performance were species-specific and dependent on the identity of co-occurring species. Consequently, multiple parasitoid species generally strengthen top down-control, but the performance of the parasitoids depends on the identity of either the co-occurring parasitoid species, the alternative host species, or both. C_LIO_LIOur results highlight the importance of preserving predator diversity for ecosystem functioning, but also show that other effects depend on community composition, and will therefore be likely altered by current environmental changes. C_LI

ecology↗

bioRxiv2021

DROP: Molecular voucher database for identification of Drosophila parasitoids

Molecular identification is increasingly used to speed up biodiversity surveys and laboratory experiments. However, many groups of organisms cannot be reliably identified using standard databases such as GenBank or BOLD due to lack of sequenced voucher specimens identified by experts. Sometimes a large number of sequences are available, but with too many errors to allow identification. Here we address this problem for parasitoids of Drosophila by introducing a curated open-access molecular reference database, DROP (Drosophila parasitoids). Identifying Drosophila parasitoids is challenging and poses a major impediment to realize the full potential of this model system in studies ranging from molecular mechanisms to food webs, and in biological control of Drosophila suzukii. In DROP (http://doi.org/10.5281/zenodo.4519656), genetic data are linked to voucher specimens and, where possible, the voucher specimens are identified by taxonomists and vetted through direct comparison with primary type material. To initiate DROP, we curated 154 laboratory strains, 856 vouchers, 554 DNA sequences, 16 genomes, 14 transcriptomes, and 6 proteomes drawn from a total of 183 operational taxonomic units (OTUs): 114 described Drosophila parasitoid species and 69 provisional species. We found species richness of Drosophila parasitoids to be heavily underestimated and provide an updated taxonomic catalogue for the community. DROP offers accurate molecular identification and improves cross-referencing between individual studies that we hope will catalyze research on this diverse and fascinating model system. Our effort should also serve as an example for researchers facing similar molecular identification problems in other groups of organisms.

genomics↗

bioRxiv2020

Experimental warming influences species abundances in a Drosophila host community through direct effects on species performance rather than altered competition and parasitism

Current global warming trends are expected to have direct effects on species through their sensitivity to temperature, as well as on their biotic interactions, with cascading indirect effects on species, communities, and entire ecosystems. To predict the community-level consequences of global change we need to understand the relative roles of both the direct and indirect effects of warming. We used a laboratory experiment to investigate how warming affects a tropical community of three species of Drosophila hosts interacting with two species of parasitoids over a single generation. Our experimental design allowed us to distinguish between the direct effects of temperature on host species performance, and indirect effects through altered biotic interactions (competition among hosts and parasitism by parasitoid wasps). Although experimental warming significantly decreased parasitism for all host-parasitoid pairs, the effects of parasitism and competition on host communities did not vary across temperatures. Instead, effects on host relative abundances were species-specific, with one host species dominating the community at warmer temperatures, independently of parasitism and competition treatments. Our results show that temperature shaped a Drosophila host community directly through differences in species thermal performance, and not via its influences on biotic interactions.

ecology↗