Meeting Abstract
Invasive species are predicted to have decreased immunity compared with conspecifics from more established ranges, specifically inflammatory responses that may be energetically costly and decrease dispersal. Populations of the invasive cane toad, introduced into Florida in the early 1930’s, have recently spread northward through the state. To determine if toads near the invasion front in Florida have predicted differing immune responses, toads were collected from a southern core (Miami-MIA) and northern invasion front population (New Port Richey-NPR), and given an immune challenge with lipopolysaccharide (LPS). Toads were injected with either saline (n = 5 and 6, MIA and NPR, respectively) or 20 µg/gram of body mass with LPS (n = 11, 9 (MIA, NPR respectively)), and metabolic rates were measured for 20 hr. Toads were bled at 20 hr, and we measured plasma corticosterone (CORT) levels and bacteria killing ability (BKA). Toads injected with LPS had significantly higher metabolic rates during the 20 hr following injection compared with saline-injected toads (p = 0.018), although metabolic rates of LPS-injected toads did not differ between the populations (p = 0.27). CORT levels of toads injected with LPS at 20 hr were not different than saline-injected toads for either population at 20 hr (p = 0.24), although, regardless of treatment, toads from NPR had significantly higher CORT levels than MIA toads (p = 0.025). At 20 hr, BKA of LPS-injected toads was significantly higher than saline-injected toads (p = 0.0008), with Miami toads having significantly higher BKA than NPR (p =0.009). Although further studies are needed, CORT differences between the populations, and BKA differences between the populations responding to LPS, could provide support to predictions by the EICA hypothesis.
