A trade‐off model for immunocompetence: The potential contribution of immunological regulation in invasive vertebrate success

Abstract

Invasive species have become a prolific environmental issue, second only to climate change, yet many of the phenomena that facilitate invasive success are not well understood (Phillip & Shine, Proc. Roy. Soc. B, 273, 1545-1550. The combination of several generalist life-history traits, certain physiological mechanisms, and environmental conditions is thought to play a significant role in invasion success. The ability to undergo fitness trade-offs-to reallocate nutritional and energetic resources towards processes that increase reproduction, growth, and dispersal-is also thought to be an adaptive quality of many invasive species. Due to their inherent flexibility, phenotypically plastic traits in particular are often targeted for fitness reallocations.Immune function, for example, is determined by a highly plastic phenotype, which is crucial for combating a diverse array of pathogens. When active, immune function also demands extensive resources from the host. Laboratory and field studies suggest that certain aspects of the immune system are more costly than others, though, and that its components can be regulated independent of one another. In invasive species undergoing fitness trade-offs, costly innate inflammatory responses are often downregulated, while antibody-mediated responses may be enhanced. A combination of fixed physiological responses and environmentally induced trade-offs are thought to regulate the immune system, though the relationship between these facets of regulation is still an area of active research. The field of ecoimmunology, then, has emerged in effort to understand the phenomena by which individual immune regulation can drive (and be driven by) species-level ecology and evolution, and therefore be linked to invasive success (Downs et al., 2014. Integr. Compar. Biol., 54, 340-352).adaptive, cell-mediated, ecoimmunology, enemy-release hypothesis, fitness trade-offs, humoral, immunocompetence, inflammatory response, innate, invasive species

Stress and immunity: Field comparisons among populations of invasive cane toads in Florida

“…We predicted that baseline BKA would be lower in the North region, once the complement proteins may activate the inflammatory response (Gao & Deviche, 2019; Ochsenbein & Zinkernagel, 2000), which is predicted by the EICA/EICA‐revised hypotheses to be downregulated in invading populations (Blossey & Notzold, 1995; Lee & Klasing, 2004; Lee, Martin, & Wikelski, 2005). The EICA/EICA‐revised hypotheses also predict that populations of invading organisms rely more on Ab or humoral immune responses, and therefore we predicted that populations in the North region would have higher baseline Ab titers (Blossey & Notzold, 1995; Lee & Klasing, 2004; Lee et al, 2005; Poirier, 2019). Although we did not see this occurring in the cane toads from our study, these individuals were not mounting an immune response to an antigen; no stimuli were given to generate specific Ab titers production; rather, we assessed natural Ab levels.…”

Epidermal Club Cells in Fishes: A Case for Ecoimmunological Analysis

“…For example, pre-formed elements of innate immunity, like mucus and antimicrobial peptides, which are critical in providing immediate defense is likely to require less resources than the ones involving systemic activation and turnover of cellular components (e.g., phagocytic macrophages). Similarly, the cell-mediated (T lymphocytic) immune responses, which are essential for tackling intracellular pathogens, are likely to be more metabolically expensive than antibody-mediated humoral immune response against extracellular pathogens [ 203 , 204 ]. The elements of the immune system that are costlier to maintain are more likely to be affected by environmental stressors [ 190 ].…”

Invading nonnative frogs use different microhabitats and change physiology along an elevation gradient

“…Many studies have documented phenotypic differences among populations of invasive species in their nonnative range (Kolbe et al, 2014; McCann et al, 2014; Mittan & Zamudio, 2019) suggesting that they acclimate to local conditions. Such studies in animals often investigate changes in physiology (Litmer & Murray, 2019; Llewelyn et al, 2010; Mittan & Zamudio, 2019; Poirier, 2019; Shearer et al, 2016), behavior (Brown et al, 2011; Currylow et al, 2021), morphology (O'Neill et al, 2018; Phillips et al, 2006; Van Kleeck et al, 2015), and life history (Phillips et al, 2010). In many cases, it is unclear whether these changes are genetic or phenotypic plasticity, and often likely both changes are key to invasives responding to novel landscapes (Agrawal, 2001; Davidson et al, 2011; Forsman, 2015).…”