Long‐term effect of over‐supplementation 565


on the verge of extinction, and it is categorized as Critically Endangered regionally (Witkowski, 2004), even though in Europe as a whole it is categorized as Near Threatened (van Swaay et al., 2010). In the mid 20th century, the taxon in the PieninyMountains was described as P. apollo franken- bergeri (Slaby, 1955). A combination of several threat factors reduced its abundance in the early 1990sto 20–30 adults per year (Witkowski & Adamski, 1996; Adamski &Witkowski, 2007). A two-stage recovery project for the subspecies began in


FIG. 1 (a) Location of the Pieniny Mountains in Poland, and (b) the spatial structure of the Apollo butterfly Parnassius apollo metapopulation (Adamski &Witkowski, 2007) in the Pieniny National Park, showing the western, central and eastern subpopulations and their patchy structure. The question mark indicates uncertain status.


flawed for invertebrates. The recovery project of the large blue butterfly Phengaris arion in the UK resulted in an abundance of the species at some sites that was equivalent to the estimated local carrying capacity (Thomas et al., 2010). A similar situation arose during the Apollo butterfly Parnassius apollo recovery project in the Pieniny Nation- al Park in southern Poland, albeit on a smaller scale (Adamski & Witkowski, 2007). Effectiveness analysis of the first decade of the project suggested there could be a problem concerning over-supplementation with captive- reared specimens (Adamski & Witkowski, 2007); i.e. that the introduction of too many individuals caused the carry- ing capacity of the habitat to be exceeded. Here we analyse the population dynamics of the Apollo


butterfly during the 25 years of the recovery project in the Pieniny National Park. This long-term study, in conjunction with the short lifetime of theApollo, provides a unique oppor- tunity for analysing a multi-generational period. Analysis of the state of a population using classical population growth models may be helpful for assessing the potential harm to a recovery programme of over-supplementation.


Study population


The Apollo (family Papilionidae) is categorized as Least Concern on the IUCN Red list (Nadler et al., 2021). But by the 1950s, the sole remaining population in Poland was in the Pieniny Mountains (Fig. 1a), where it had been known and studied since at least the second half of the 19th century (Siła-Nowicki, 1865). By the end of the 1980s, however, it was


1992. In the first stage, the sites inhabited by the subspecies before its decline were restored by removing the trees and shrubs that had been planted during reforestation pro- grammes or that had grown as a result of succession follow- ing scree stabilization and abandonment of management of the mountain meadows. By 1997, these sites had been re- stored to a suitable state (Witkowski et al., 1997; Adamski & Witkowski, 2007; Adamski, 2016). In the second stage, indi- viduals from the Pieniny National Park’s captive breeding programme, which originated from the local population, were reintroduced (Witkowski & Adamski, 1996;Adamski & Witkowski, 2007). During the first stage, the carrying capacity for the


Apollo butterfly was estimated from an inventory of host plant abundance (Witkowski et al., 1992; Adamski & Witkowski, 2007): the anticipated target abundance was 1,200–1,300 adults. The Apollo’s abundance was estimated using the capture–mark–recapture method. All reintroduc- tion sites were visited weekly, when the weather was favour- able for the species’ activity, and individuals were netted and marked with a unique code on the hindwing, and released (Adamski & Witkowski, 2007; Adamski, 2016). Abundance was estimated using Craig’smethod(Seber, 1982). The study population is a mixed type metapopulation (Harrison, 1991) comprising western, central and eastern populations and a few smaller, ephemeral subpopulations (Fig. 1b; Adamski & Witkowski, 2007;Adamski, 2016).


Methods


Simulation of population recovery based on captive-reared individuals


The model aimed to analyse population growth scenarios in a reinforced population in which the basic model para- meters varied in value and stability. The simulation was carried out using Ricker’s(1958) model, a classical discrete population model in which the expected number of individ- uals in generation t + 1 is a function of the number of indi- viduals in generation t, with the addition of a new variable Nc, the number of captive-reared individuals in generation t:


Nt+1 = Nter1−


Nt+Nc K


 Oryx, 2022, 56(4), 564–571 © The Author(s), 2022. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605321000296 (1)


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