Plant reintroductions as demographic-genetic experiments

Background/Question/Methods

Plant conservation practice increasingly involves population reinforcement and reintroductions, a.o. to counter detrimental genetic effects of habitat fragmentation. The consequences of these actions for population viability parameters are rarely monitored, however.  We have studied effects of population reinforcement experiments on levels of genetic diversity and reproductive success in the self-incompatible plant Arnica montana. We compared genetic diversity with AFLP markers, population size and seed set between 15 Dutch populations sampled in 2000 and again in 2012. Five of these populations became extinct during this period. We hypothesize that (i) extinct populations were smaller, and had lower genetic diversity and seed set than extant populations, (ii) populations to which individuals from other populations were added increased their size, genetic diversity and seed set, (iii) genetic diversity and seed set declined in the small populations that were not reinforced, and (iv) large populations still had high levels of genetic diversity and good seed set.

Results/Conclusions

There were substantial differences in genetic diversity, population size and seed set between extinct, reinforced and non-reinforced (natural) populations. For the extant populations, there were also significant differences between samples from 2000 and 2012. As compared to extant populations, the extinct populations were significantly smaller and had lower genetic diversity in 2000. In contrast to natural populations, gene diversity of reinforced populations increased slightly, population size increased dramatically and they had much higher seed set in 2012 as compared to 2000. In conclusion, the reinforcement of A. montana populations has boosted their viability after 12 years. Even though genetic diversity for the AFLP markers increased only to a minor extent, population size and reproductive success increased dramatically, whereas other populations went extinct or remained stable at best. Because A. montana is long-lived and clonal, however, even in 12 years too few generations will have passed to detect outbreeding depression. Our study demonstrates that populations that were relatively small, genetically poor and consequently had low reproductive success had a higher probability of extinction.