Effects of forest structure on the interaction between avian hosts, dipteran vectors and haemosporidian parasites

Abstract

Background: Forest habitats are important biodiversity refuges for a wide variety of bird species. Parasitism may modulate host species presence and abundance, and parasite effects can change according to forest management practices. Such processes are not well studied in vector-borne avian haemosporidians. We analyzed the effects of forest management on bird-dipteran-haemosporidian interactions, using seven common bird species in managed and unmanaged beech forest habitats in northeastern Germany. We assumed that forest structural heterogeneity affects parasite population parameters in avian hosts (i.e., prevalence and parasitemia), through its effect on the condition of the avian host but also through varying vector abundances. Results: Parasite prevalence was high (about 80%) and homogeneous across different beech forest categories (i.e., young, old, unmanaged) and for all bird species, except Erithacus rubecula (35%). Parasitemia varied across bird species but not across forest categories within each avian species (lowest parasitemia were found in E. rubecula, Turdus merula, and Turdus philomelos). In our study system, we found that vector abundance was not the main driver of parasite dynamics. We found that forest structure affects parasite infection probability directly and potentially host condition via available resources that have to be used either to combat infections (i.e., high parasitemia) or to maintain a good body condition. Conclusions: The effects of each of the predictors were bird species-specific, and we found that Diptera vectors were not the foremost influence in our host-vector-parasite system. Effects of forest habitat variables indicated that for most bird species in this study, habitat regulation of infection probability was more likely (i.e., E. rubecula, Fringilla coelebs, Sylvia atricapilla), whereas for Parus major habitat characteristics impacted first individuals' body condition and subsequently the probability of infection. Our findings emphasize the need of species-specific analyses and to use continuous forest structural parameters (e.g., the proportion of gap, south facing aspect) to better understand habitat and land use effects on host-vector-parasite dynamics.

The drivers of avian‐haemosporidian prevalence in tropical lowland forests of New Guinea in three dimensions

“…The species‐specific effect of different environmental variables on Haemoproteus prevalence (Figure 2 ) aligns with results from other studies on bird species from both temperate and tropical regions (Isaksson et al, 2013 ; Samuel et al, 2015 ; Santiago‐Alarcon et al, 2019 ; Van Hoesel et al, 2020 ). Despite the overall nonsignificant effect of distance to roads (a proxy for anthropogenic influence), it did significantly affect prevalence in three bird species, suggesting the potential for elevated infection levels with increased anthropogenic activity.…”

“…While prevalences did not differ between the continuous and fragmented forests, host–parasite network structures were notably different, where continuous forests harbored significantly more specialized networks than fragmented forests. The greater specialization in continuous forests could imply that undisturbed forests may provide more stable environments with higher host species richness (Bregman et al, 2014 ; Sam et al, 2014 ; Van Hoesel et al, 2020 ) that could lead to more specialized associations. Highly specialized avian‐haemosporidian networks has been observed before in an undisturbed tropical lowland bird community in Ecuador (Svensson‐Coelho et al, 2014 ).…”

The drivers of avian haemosporidian prevalence in tropical lowland forest of New Guinea in three dimensions

“…The species-specific effect of different environmental variables onHaemoproteus prevalence (Figure 2) aligns with results from other studies on bird species from both temperate and tropical regions (Isaksson, Sepil, Baramidze, & Sheldon, 2013;Samuel, Woodworth, Atkinson, Hart, & LaPointe, 2015;Santiago-Alarcon et al, 2019;Van Hoesel, Santiago-Alarcon, Marzal, & Renner, 2020). Despite the overall non-significant effect of distance to the road (a proxy for anthropogenic influence) on prevalence, this factor did significantly affect prevalence in three bird species, suggesting the potential for elevated infection levels with increased anthropogenic activity (Table 1).…”

Contrasting drivers of diversity in hosts and parasites across the tropical Andes

“…Variation in the distribution of these vectors likely underlies the elevational segregation that we see among hemosporidian genera and may affect turnover within each genus (SI Appendix). Most available evidence suggests hemosporidian distributions are less constrained by vector compatibility than by vertebrate host compatibility (80,89). Nevertheless, the role of vector availability and diversity in shaping hemosporidian distribution requires further study.…”