Data from: The effect of inbreeding rate on fitness, inbreeding depression and heterosis over a range of inbreeding coefficients

Understanding the effects of inbreeding and genetic drift within
populations and hybridization between genetically differentiated
populations is important for many basic and applied questions in ecology
and evolutionary biology. The magnitudes and even the directions of these
effects can be influenced by various factors, especially by the current
and historical population size (i.e., inbreeding rate). Using Drosophila
littoralis as a model species, we studied the effect of inbreeding rate
over a range of inbreeding levels on 1) mean fitness of a population
(relative to that of an outbred control population), 2) within-population
inbreeding depression (reduction in fitness of offspring from inbred vs.
random mating within a population), and 3) heterosis (increase in fitness
of offspring from inter-population vs. within-population random mating).
Inbreeding rate was manipulated by using three population sizes (2, 10,
and 40), and fitness was measured as offspring survival and fecundity.
Fast inbreeding (smaller effective population size) resulted in greater
reduction in population mean fitness than slow inbreeding, when
populations were compared over similar inbreeding coefficients.
Correspondingly, populations with faster inbreeding expressed more
heterosis upon inter-population hybridization. Inbreeding depression
within the populations did not have a clear relationship with either the
rate or the level of inbreeding.