Migratory History and Ecology of the Apollo butterfly

This article is the first in a two-part, scientifically-based series on Parnassius apollo by Maureen Nieuwschepen

Origin and migratory history

The Parnassius genus first originated in Laurasia (now West-China, Fig. 1) in the early Paleogen (about 65 million years ago). The collision of the Indian tectonic plate into the Asian continent, during the Miocene epoch (23.03 – 5.33 million years ago), resulted in the formation of the Himalayan mountain ranges in Central Asia and thereby a dramatic change in habitats. The Himalayan plateau blocked the Asian monsoon and reduced precipitation in Central Asia (Quade et al., 1989), which led to an increase in steppe plants. The changes in biotic (host plant shift) and abiotic (climate change and orogeny (i.e. mountain formation by converging tectonic plates)) conditions led to the first large-scale radiation of Parnassius into more than 50 species (Condamine et al., 2018). 

Further diversification

One Parnassius species, Parnassius apollo (Linnaeus, 1758), dispersed far westward towards Europe and northwards until the permanent snow cover border (Nakonieczny et al., 2007).  During this time, it was still a vast steppe species. The first glaciation in Europe drove P. apollo southwards into refuges (Nakonieczny et al., 2007). Further subsequent glacial-interglacial cycles fueled the expansion and retraction of P. apollo and its occupations and withdrawals in and out of refuges. These ongoing dynamics most probably have led to the further subspecific evolution within P. apollo, leading to over  200 described subspecies in Europe (Todisco et al., 2010). Similar, but to a lesser extent dynamic, processes occurred in the Asian P. apollo range, explaining the difference in subspecies variety between Europa and Asia.

Current distribution

The shrinking steppe habitat in Europe posed selective pressure on P. apollo, leading to a gradual change from a typical steppe species to a mountain-steppe species (Nakonieczny et al., 2007). Now, P. Apollo is considered a steppe and mountain-subalpine-sub boreal species, occupying many different habitats in a wide distribution range (Descimon, 1995).  Its extensive Palaearctic range spans from 7° W (Cantabrian Mountains, Spain) to 120° E (Yakutia, Russia), including the Khentei Mountains in Mongolia. Its latitudinal distribution spans from 62° N (western Finland and Oppland, Norway) to approximately 38° N (Sierra Gádor in Spain, La Madonie massif in Sicily, Mt. Erímanthos in Greece, and West Taurus massif in northeastern Turkey) (summarized from several sources by Nakonieczny et al., 2007)(Fig. 1).

Description

The appearance of P. Apollo makes it one of Europe’s most iconic butterflies, with its 50-80 mm wingspan, chalk-white wings, grey markings, and black and red spots. Males and females differ in their patterns on the fore and hindwings, indicating sexual dimorphism. The different subspecies vary in size, wing shape, and wing pattern. However, the red spots are always present on the hindwings (Bonin et al., 2024).

Apollo habitats in Europe

P. Apollo habitats in Europe typically consist of dry calcareous grasslands and steppes in upland areas, and alpine and subalpine grassland. Rocky habitats and screes are also suitable, but below an altitude limit dependent on the mountain range (up to 1,800 m a.s.l. in the Carpathians, 2,500 m a.s.l. in the Alps, and 3,000 m a.s.l. in the Sierra Nevada (Nakonieczny et al., 2007). Regardless of habitat type, the availability of suitable food plants for the larvae is crucial.  

Host plants

P. apollo is an oligophagous species, i.e., it is restricted to a few specific food sources. Larvae (caterpillars) feed on Sedum album (Linnaeus, 1758) (Fig. 4) or Hylotelephium telephium (Linnaeus, 1758) (Fig. 5) (Nakonieczny & Kędziorski, 2005). These are Sedum species, or stonecrop, which can live in dry conditions due to their CAM strategy (Crassulacean Acid Metabolism) (Wai et al., 2019). Lowland P. apollo populations primarily feed on H. telephium, as it grows in open forests and meadows. In contrast, higher altitude P. apollo populations predominantly feed on S. album, a species found in calcareous rocky environments (Stephenson, 1994).  This divides European P. apollo populations into ‘telephiophagous’ forms, feeding on H. telephium and ‘albophagous’ forms, feeding on S. album. Flying adult butterflies rely on a broader range of nectariferous plants for their nectar source, depending on the availability in the area (Massolo et al., 2022).

Life cycle

The P. Apollo life cycle (Fig. 6) lasts one year and is univoltine, i.e., overwintering in the egg stage (Bonin et al, 2024).  Females lay eggs that remain dormant over the winter and hatch in the spring of the following year.  The larvae feed on the host plants until they develop fully in size while going through several molts. After this phase, the caterpillar turns into metamorphosis, becoming a pupa. The pupa does not feed but relies on the energy stored from the food it consumed as a larva (Gilbert et al., 1996).  While in the pupa state, the metamorphosis of larva to adult butterfly occurs through a complex series of biochemical reactions, controlled by neural and hormonal mechanisms (Gilbert et al., 1996). 

EWS is a partner of LIFE Apollo2020, which is dedicated to the conservation of Parnassius apollo in Austria, Poland, and Czechia. Find more information on the website.

Bibliography

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Descimon, H., Bachelard, P., Boitier, E., & Pierrat, V. (2005). Decline and extinction of Parnassius apollo populations in France-continued. Studies on the Ecology and Conservation of Butterflies in Europe, 1, 114-115.

Gilbert, S. F., Opitz, J. M., & Raff, R. A. (1996). Resynthesizing evolutionary and developmental biology. Developmental biology, 173(2), 357-372.

Massolo, A., Fric, Z. F., & Sbaraglia, C. (2022). Climate Change Effects on Habitat Suitability of a Butterfly in the Past, Present, and Future: Biotic Interaction between Parnassius Apollo and Its Host Plants. University of Pisa.

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Wai, C. M., Weise, S. E., Ozersky, P., Mockler, T. C., Michael, T. P., & VanBuren, R. (2019). Time of day and network reprogramming during drought induced C