Data from: The conservation value of small population remnants: variability in inbreeding depression and heterosis of a perennial herb, the narrow-leaved purple coneflower (Echinacea angustifolia)

Anthropogenically fragmented populations may have reduced fitness due to
loss of genetic diversity and inbreeding. The extent of such fitness
losses due to fragmentation and potential gains from conservation actions
are infrequently assessed together empirically. Controlled crosses within
and among populations can identify whether populations are at risk of
inbreeding depression and whether interpopulation crossing alleviates
fitness loss. Because fitness depends on environment and life stage,
studies quantifying cumulative fitness over a large portion of the
lifecycle in conditions that mimic natural environments are most
informative. To assess fitness consequences of habitat fragmentation, we
leveraged controlled within-family, within-population, and
between-population crosses to quantify inbreeding depression and heterosis
in seven populations of Echinacea angustifolia within a 6400-hectare area.
We then assessed cumulative offspring fitness after 14 years of growth in
a natural experimental plot (N = 1136). Mean fitness of progeny from
within-population crosses varied considerably, indicating genetic
differentiation among source populations, even though these sites are all
less than 9 km apart. The fitness consequences of within-family and
between-population crosses varied in magnitude and direction. Only one of
the seven populations showed inbreeding depression of high effect, while
four populations showed substantial heterosis. Outbreeding depression was
rare and slight. Our findings indicate that local crossings between
isolated populations yield unpredictable fitness consequences ranging from
slight decreases to substantial increases. Interestingly, inbreeding
depression and heterosis did not relate closely to population size,
suggesting that all fragmented populations could contribute to
conservation goals as either pollen recipients or donors.