Examining Host-Parasite Dynamics in the Gulf of Guinea
Authors:   , Miller Steven C. , Gonder Mary K 
Published: February 2022

Islands serve as natural laboratories to better understand patterns and processes due to their inherent biodiversity, simplified ecological interactions and limited gene flow between disparate populations. The Gulf of Guinea, West Africa, is considered one of 25 global biodiversity hotspots and is home to Bioko island, a land bridge island that was formally connected to mainland West Africa approximately 12,000 ya during the last glacial maximum. Due to its inherent biodiversity, Bioko provides an excellent opportunity to investigate factors that may influence species distribution and diversification patterns among isolated populations. The present dissertation focused on three specific factors that have shaped and continue to shape these patterns among avian species on Bioko: elevation, anthropogenic disturbance and host-parasite dynamics. Regarding avian community composition on Bioko, insectivorous species were the most abundant guild sampled, accounting for 55% of total species diversity within the data set followed by frequent mixed-flock followers (48%). Habitat associated with elevation was the most significant factor influencing the composition of avian communities. Additionally, I identified species with clear statistical associations with a given elevation: the yellow-lored bristlebill (Bleda notatus), Olive Sunbird (Cyanomitra obscura), and white-tailed warbler (Poliolais lopezi). I found evidence for significant community differences between the disturbance edge and interior forest transects at 300 m only. Likewise, understory insectivores were found at higher numbers within the interior forest transect at this elevation. These results suggest that avian species on Bioko are adapted to specific bands of elevational habitat and that low elevation insectivores (mixed flock followers) are sensitive to anthropogenic disturbance. In my second chapter that compares rates of parasite infections in birds on Bioko to those on the mainland, I found higher rates of Plasmodium infection among the mainland avian host populations and higher rates of Haemoproteus and Leucocytozoon infection among the island avian host populations. Based on overall haemosporidian lineage diversity, Bioko Island should be considered a biodiversity hotspot for avian haemosporidians whereas the mainland fails to reach the threshold of 1.24 parasite lineages/bird for this classification. I also found high rates of host specialization among both Plasmodium and Haemoproteus in the island haemosporidian community, whereas Leucocytozoon more of a host generalist in both locations. Lastly, I found that a lack of mixed-flock following behavior was associated with decreased probability of overall haemosporidian infection and both Haemoproteus and Leucocytozoon infection. Additionally, haemosporidian lineages appeared to be most significantly associated with the host species from which they were isolated as opposed to other external factors such as elevation and habitat type. Collectively, these data highlight the complexity of host/parasite dynamics and suggest that host ecology, life history and environmental factors play important roles regarding parasite transmission and pathogenicity within the region. Future studies of disease emergence should focus not only on host carrying capacity and vector competence, but also on ecological behavior, species interactions and group responses to habitat disturbance as these may be crucial factors influencing pathogen spillover.