Anywhere but here: local conditions alone drive dispersal inDaphnia

Abstract

Dispersal is fundamental to population dynamics and it is increasingly apparent that, despite most models treating dispersal as a constant, many organisms make dispersal decisions based upon information gathered from the environment. Ideally, organisms would make fully informed decisions, with knowledge of both intra-patch conditions (conditions in their current location) and extra-patch conditions (conditions in alternative locations). Acquiring information is energetically costly however, and extra-patch information will typically be costlier to obtain than intra-patch information. As a consequence, theory suggests that organisms will often make partially informed dispersal decisions, utilising intra-patch information only. We test this proposition in an experimental two-patch system using populations of the aquatic crustacean, Daphnia carinata. We manipulated conditions (food availability) in the population's home patch, and in its alternative patch. We found that D. carinata made use of intrapatch information (resource limitation in the home patch induced a ten-fold increase in dispersal probability) but made no use of extra-patch information (resource limitation in the alternative patch did not affect dispersal probability). Our work highlights the very large influence that information can have on dispersal probability, but also that dispersal decisions will often be made in only a partially informed manner. The magnitude of the response we observed also adds to the growing chorus that condition-dependence may be a significant driver of variation in dispersal.

Infection in patchy populations: Contrasting pathogen invasion success and dispersal at varying times since host colonization

“…To determine the repeatability of host colonization, we first created four replicates of three interconnected experimental patches built from 500‐mL containers filled with 400 mL artificial media (see Erm et al. ). On day 1, five 3‐day old juveniles and one adult Daphnia were introduced into the first patch, and the subsequent population sizes at each patch were counted weekly thereafter.…”