Meeting Abstract

S6.4  Wednesday, Jan. 5  Physiological mechanisms of range expansion in Kenyan house sparrows MARTIN, LB*; LEIBL, AL; COON, CAC; RICHARDS, CL; SCHREY, AW; University of South Florida, Integrative Biology; University of South Florida, Integrative Biology; University of South Florida, Integrative Biology; University of South Florida, Integrative Biology; University of South Florida, Integrative Biology lmartin@cas.usf.edu

Organisms introduced outside their native range should sacrifice costly defenses because of the enemy release experienced in new areas. Previous studies in house sparrows (Passer domesticus), one of the world’s most broadly distributed species, have supported this idea, indicating that inflammatory responses particularly are damped in invaders. Inflammation is one of the most expensive inducible immune responses animals can mount. In the present study, we investigated the importance of adjustments of inflammatory responses during the recent (~50 years) colonization of Kenya as well as the molecular mechanisms mediating variation in inflammatory responses. We predicted that the newest (western-most) Kenyan populations would exhibit the weakest whereas the oldest (eastern-most) populations would exhibit the strongest inflammatory responses, and we expected that these differences would be mediated by variation in mRNA expression of microbial detectors (Toll-like receptor 4; TLR4) and/or pro-inflammatory cytokines (i.e., interleukins-1 and 6) among populations. To test the hypothesis, we compared aspects of acute phase responses (APRs) to lipopolysaccharide (LPS; a component of Gram-negative bacteria) among 7 populations. Preliminary analysis indicates that one aspect of APRs, anorexia (i.e., body mass loss), was not weakest in the western-most city as expected, but instead weakest in a central Kenyan population (Nakuru). Ongoing analyses are investigating other APR elements as well as the functional genetic basis of APR variation pattern (via cytokine gene expression) and whether Nakuru is the true vanguard population of the colonization (via microsatellite analyses).