Th.--Pharm.--Paris 5, 1982. N°: 71.

Reliable estimates of species abundance, distribution, and population trajectories are critical in conservation and management. However, for many tropical species that information is missing. We conducted Sharp-shinned Hawk (SSHA) searches during the breeding seasons of 2013, 2014, and 2016 in eight montane forest reserves and their adjacent private lands of Puerto Rico. Further, we developed a maximum entropy model (MaxEnt) of the SSHA’s potential distribution using the following environmental variables: aspect, canopy closure, elevation, rainfall, slope, and terrain roughness. Elevation accounted for 89.8% of model fit, predicting the greatest probability of occurrence (> 60%) at elevations above 900 m. The model estimated 0.6% Puerto Rico (56.1 km2) has the greatest probability of occurrence. We developed a periodic population matrix model to describe influence of early life stages on population growth of the Red-tailed Hawk (RTHA) in eastern Puerto Rico. Our results suggest that the RTHA population has an average annual population increase of 5%, with rates differing between highlands (λh = 1.05) and 27% lowlands (λl = 1.27). Adult survival was the most important population growth parameter, with more effect in highlands (elasticity = 0.86) than in lowlands (elasticity = 0.53). Sensitivity of λ to changes in nestling survival was greater than for other life-stages (sensitivity lowlands = 0.46, sensitivity highlands = 0.48). I developed an open population N-mixture model to estimate abundance, availability, and detection probability of RTHA in the Luquillo Mountains and western Cordillera Central. The abundance estimates were 0.05 RTHA/ha, with an availability of (ϕ) = ~1 RTHA/per survey point and a detection probability (r) = ~0.25. In Luquillo Mountains, abundance was positively influenced by slope and elevation. In the western Cordillera Central, abundance of RTHA was constant across elevation, slope, and canopy closure. Detection probability decreased with increasing slope and wind conditions and showed a gradual small negative decrease with slope with reduced winds conditions. My findings are a contribution to our knowledge to how population traits and ecological constraints imposed by insular environments are influencing distribution, abundance, and population dynamics of raptors to propose management or conservation schemes.

The influence of forest canopy disturbance (FCD) on La Crosse virus (LACV), leading cause of US pediatric arboviral encephalitis, is critical to understand in landscapes where forests are periodically harvested. Southwestern Virginia is part of an emerging focus of this interior forest bunyavirus. I investigated how the temperate forest mosquito community, LACV vectors, and the LACV amplifying vertebrate host (chipmunks) were impacted by logging. This research was conducted across an experimental FCD gradient (from least to most disturbed: contiguous control, fragmented control, clearcut, and high-leave shelterwood (SW)). Using gravid traps, I found that the mosquito community was resilient to logging with no significant difference in diversity or community composition across treatments. Mean number of female mosquitoes caught per trap-night declined with disturbance. FCD significantly affected the abundance of vector species in different ways. The primary LACV vector, Aedes triseriatus, and the recent invasive Ae. japonicus declined with logging. Other vectors (Ae. albopictus, Ae. canadensis, and Ae. vexans) thrived with logging. Culex pipiens/restuans was affected by disturbance but had no treatment preference. A mark-recapture study revealed that chipmunk abundance and LACV seroprevalence were greatest on the SW. In sync with Ae. triseriatus abundance but in contrast to the chipmunk results, mosquito LACV detection was significantly greater on unlogged sites. Surprisingly, LACV was detected in Ae. japonicus and Cx. pipiens/restuans. In a follow-up study, I isolated LACV from field-collected Ae. japonicus. Although LACV was previously isolated from Cx. pipiens, the vector competence was unknown. Therefore, I examined the vector competence of Cx. pipiens and Cx. restuans. Although poor vectors, I did detect LACV in the saliva of both species. An additional experiment found that nutritionally-stressed Cx. restuans were better vectors than those in the control group, indicating that environmental stressors (e.g., FCD) may alter the ability of accessory vectors to spread LACV. The influence of FCD on LACV is complex. Because logging decreases Ae. triseriatus abundance, human LACV risk is likely lowered by decreased transovarial vertical transmission. However, high chipmunk seroprevalence on disturbed sites suggest horizontal transmission with accessory vectors plays a larger role in LACV risk on recently logged sites. / Ph. D.