Data from: Population viability of the orchid Gymnadenia conopsea increases with population size but is not related to genetic diversity

Population size is a main indicator of conservation potential, thought to
predict both current and long-term population viability. However, few
studies have directly examined the links between the size and the genetic
and demographic properties of populations, using metrics that integrate
effects across the whole life cycle. In this study, we combined six years
of demographic data with SNP-based estimates of genetic diversity from 18
Swedish populations of the orchid Gymnadenia conopsea. We
assessed whether stochastic growth rate increases with population size and
genetic diversity, and used stochastic LTRE analysis to evaluate how
underlying vital rates contribute to among-population variation in growth
rate. For each population, we also estimated the probability of
quasi-extinction (shrinking below a threshold size) and of a severe (90%)
decline in population size, within the next 30 years. Estimates of
stochastic growth rate indicated that ten populations are declining, seven
increasing, and one population is approximately stable. SLTRE
decomposition showed that low mean adult survival and growth characterized
strongly declining populations, whereas high mean fecundity characterized
strongly increasing populations. Stochastic growth rate increased with
population size, mainly due to higher survival in larger populations, but
was not related to genetic diversity. One third of the populations were
predicted to go extinct and eight populations to undergo a 90% decrease in
population size in the coming 30 years. Low survival in small populations
most likely reflects a positive association between local environmental
conditions and population size. Synthesis: The association between G.
conopsea population size and viability was driven by variation in
survival, and there was no sign that ongoing declines are due to genetic
erosion. This suggests that large populations occur in favourable habitats
that buffer effects of climatic variation. The results also illustrate
that demographic metrics can be more informative than genetic metrics,
regarding conservation priority.