Local adaptation and host specificity to copepod intermediate hosts by the tapeworm .

Host-parasite coevolution may lead to patterns of local adaptation in either the host or parasite. For parasites with complex multi-host life cycles, this coevolution may be more challenging as they must adapt to multiple geographically varying hosts. The tapeworm exhibits some local adaptation to its second intermediate host, threespine stickleback, to which the parasite is strictly specialized.

Population-level variation in parasite resistance due to differences in immune initiation and rate of response.

Closely related populations often differ in resistance to a given parasite, as measured by infection success or failure. Yet, the immunological mechanisms of these evolved differences are rarely specified. Does resistance evolve via changes to the host's ability to recognize that an infection exists, actuate an effective immune response, or attenuate that response? We tested whether each of these phases of the host response contributed to threespine sticklebacks' recently evolved resistance to their tapeworm .

Between-population differences in constitutive and infection-induced gene expression in threespine stickleback.

Vertebrate immunity is a complex system consisting of a mix of constitutive and inducible defences. Furthermore, host immunity is subject to selective pressure from a range of parasites and pathogens which can produce variation in these defences across populations. As populations evolve immune responses to parasites, they may adapt via a combination of (1) constitutive differences, (2) shared inducible responses, or (3) divergent inducible responses.

Character displacement in the midst of background evolution in island populations of Anolis lizards: A spatiotemporal perspective.

Negative interactions between species can generate divergent selection that causes character displacement. However, other processes cause similar divergence. We use spatial and temporal replication across island populations of Anolis lizards to assess the importance of negative interactions in driving trait shifts.

Resist Globally, Infect Locally: A Transcontinental Test of Adaptation by Stickleback and Their Tapeworm Parasite.

Parasite infections are a product of both ecological processes affecting host-parasite encounter rates and evolutionary dynamics affecting host susceptibility. However, few studies examine natural infection variation from both ecological and evolutionary perspectives. Here, we describe the ecological and evolutionary factors generating variation in infection rates by a tapeworm (Schistocephalus solidus) in a vertebrate host, the threespine stickleback (Gasterosteus aculeatus).

Population-Specific Covariation between Immune Function and Color of Nesting Male Threespine Stickleback.

Multiple biological processes can generate sexual selection on male visual signals such as color. For example, females may prefer colorful males because those males are more readily detected (perceptual bias), or because male color conveys information about male quality and associated direct or indirect benefits to females. For example, male threespine stickleback often exhibit red throat coloration, which females prefer both because red is more visible in certain environments, and red color is correlated with male immune function and parasite load.

Female stickleback prefer shallow males: Sexual selection on nest microhabitat.

Sexual selection is most often thought of as acting on organismal traits, such as size or color. However, individuals' habitat use may also affect mating success. Here, we show that, in threespine stickleback, nest depth can be a target of sexual selection.