Hide and seek: results from monitoring populations of a species prone to prolonged dormancy

Bálint Pacsai ¹, Vivien Lábadi ¹, Judit Bódis ¹

Hungarian University of Life Sciences, Department of Nature Conservation Biology, Georgikon Campus ¹

The management of protected and rare species populations is frequently planned on the basis of data obtained from censuses, with population size serving as a derived indicator of population condition. This could apply to Fritillaria meleagris, a Eurasian species that is in decline across its range and which serves as a flagship species in conservation in some regions. Estimations of population sizes are typically based on the number of flowering individuals. The objective of our study was to assess the extent of bias in population size estimates based on the number of flowering individuals. Two sets of permanent quadrats were established in populations of Fritillaria meleagris located in wet meadows in western part of Hungary: one in Gyékényes and one in Tüskeszentpéter (with 80 km distance between them). Morphometric characteristics of the plants were recorded on an annual basis between 2017 and 2023, with the specimens then classified according to their age-state categories: juvenile, vegetative, reproductive. Significant differences were identified between the two populations, exhibiting consistent patterns across years. The proportion of individuals flowering at Tüskeszentpéter was notably higher (60.6%) than that observed at Gyékényes (28.9%). The proportion of juveniles at Gyékényes was more than three times that observed at Tüskeszentpéter. The populations were similar in the frequency of prolonged dormancy with about half of the plants appeared aboveground went into dormancy in the following year (and possibly remaining in this state even longer) at both sites. Examination of transitions through dormancy revealed that stasis was the most frequent transition at both sites, however plants at Gyékényes were more likely to step forward an age-state than retrogress following dormancy, whereas at Tüskeszentpéter retrogression was more prevalent than progress. While one- and two-year dormancy were the most common, the maximum potential duration of dormancy remains unknown. Consequently, the mortality estimates were approximate and insufficient to determine the exact population size. The mortality rates observed at Gyékényes and Tüskeszentpéter were approximately 10% and 1-5%, respectively. Given the higher proportion of adult plants at Tüskeszentpéter compared to Gyékényes, an equal number of flowering individuals in the two populations would correspond to a smaller population size at Tüskeszentpéter compared to Gyékényes. These results reinforce the conclusion that the bias of population size estimates based on censuses varies greatly across different populations. They also highlight the need to study the demographic structure of such populations for more reliable population size estimates which can lead to better planning of conservation.

Main author career stage: PhD student

Contribution type: Talk

First choice session: 2. Ecology

Second choice session: 3. Biodiversity and global change