Jerome Goddard

The black bear, Ursus americanus (Carnivora: Ursidae), is a large mammal listed as threatened in the state of Mississippi since 1992. After years of historical decline, black bear numbers and their range have been increasing in Mississippi, with bears returning to areas within their historic range. Little is known about ectoparasites and vector-borne microorganisms associated with black bears. During 2024, 83 ticks comprising 4 species were removed from 17 bears (one of which was a recapture) captured in 9 central and southern Mississippi counties. Upon molecular screening of the 83 ticks, 11 specimens contained DNA of the Rickettsia endosymbiont of Ixodes scapularis (also known as Rickettsia buchneri); 20 contained Rickettsia parkeri; 21 had “Candidatus Rickettsia andeanae;” 9 had R. tillamookensis; 4 had R. amblyommatis; 1 had R. bellii; and 4 had organisms in the family Anaplasmataceae; of these, 1 was identified as Ehrlichia chaffeensis. Four ticks had detectable levels of Rickettsia DNA that could not be identified to the species level.

Incidence of tickborne diseases is increasing in the United States, with nearly half a million cases estimated to occur annually. The rising burden of tickborne disease in the United States underscores the need to investigate the presence and prevalence of tick species and associated pathogens. Southern Florida serves as an introductory point for non-native invasive reptiles, amphibians, and ectoparasites due to the region’s international ports and tropical climate. At Zoo Miami, visitors are near exhibit animals and free-living invasive species, including cane toads and green iguanas. This study identified ticks removed from reptiles and amphibians at Zoo Miami and analyzed these ticks for bacteria in the order Rickettsiales. 309 ticks were collected over a 2-year period (October 2022 to November 2024; Amblyomma dissimile Koch, 1844 (266/309), Amblyomma rotundatum Koch, 1844 (41/309), and A. tuberculatum Marx, 1894 (2/309). Rickettsia spp. DNA (Rickettsiales: Rickettsiaceae) was identified in A. dissimile (4.14%) and A. rotundatum (4.88%), including a Rickettsia species similar to several strains of R. parkeri based on a portion of the ompA gene. Three ticks contained Anaplasmataceae DNA (Rickettsiales: Anaplasmataceae), including 1 Ehrlichia chaffeensis-positive A. rotundatum, and 1 A. dissimile containing E. canis-like DNA. This study represents the first report to jointly describe ticks and their rickettsial bacteria from Zoo Miami, including novel host records for A. dissimile and A. rotundatum. Paired with identification of an ehrlichial pathogen, these novel host associations highlight the importance of tick surveillance for pathogens of public health concern in zoos and other animal facilities in southern Florida.

Fragmentation and loss of habitat owing to increased human activity are major drivers of species extinctions and declining global biodiversity. In ecological communities, trait–mediated indirect effects are frequently observed and can influence population dynamics as strongly, possibly even more strongly, than direct effects. However, few studies have focused on trait–mediated behavior such as trait–mediated dispersal, in which the dispersal patterns are altered by the presence of an interacting species. Moreover, little is known about how trait–mediated dispersal interacts with habitat fragmentation and loss to affect the coexistence of interacting species. Here, we explore the consequences of both trait–mediated dispersal and fragmentation/loss on coexistence in a system consisting of two competing species or a predator and its prey. By assuming that the density–mediated effects are negligible, we isolate the role of trait–mediated effects. Our results show that the combined influence of fragmentation and trait–mediated dispersal can substantially reshape the population dynamics and species coexistence outcomes.