By Vlado Vancura
This article is Part 1 of a series on the benefits of grazing for Apollo. Part 2 will be published next week.
Parnassius apollo is under threat. Populations of the butterfly species have dramatically decreased in the last couple of decades. There are countries with about a 20% decrease, but also some with a much more dramatic decline of around 50%. This very much depends on the geographical region.
The analysis provides evidence that the most fragile subspecies and forms of Apollo are those from a low altitude in East and Central Europe, while forms inhabiting the higher parts of the Alps and other, mostly south European, high mountain ranges are still relatively large and strong.
Disappearing habitats – Apollo requires open habitats
One hypothesis explaining these differences is that low-altitude areas in East and Central Europe have been heavily impacted by industrialization, new development and unprecedented intensification of agriculture in the last 20 years. A significant amount of habitat and food for Apollo disappeared.
Continuing on this hypothesis, we see that this kind of development was not so obvious 20 years ago in higher mountain areas. Open landscape developed by humans in previous centuries and maintained by grazing still provided fragments of suitable habitat for Apollo. This happened despite more and more massive abandonment of the traditionally grazed landscape (Fred & Brommer, 2005).
Since the Ice Age, shrinking steppe biotypes imposed selective pressure onto local Apollo populations due to a changing climate. That pressure resulted in the adaptation to new habitats, such as mountains, screes and meadows.
Gradually, Apollo shifted from a typical steppe into a mountain-steppe species. This occurred in the Alps and probably at the southern, calcareous slopes of the Carpathian Mountains, and resulted in the emergence of numerous forms and Apollo subspecies.
Current habitat of Apollo
As a steppe and mountain-subalpine-subboreal species, Apollo occupies different habitats within its range. It is found in heaths, shrubs, various grasslands communities in lowland biotopes, and also in small clearings in forest. Among the most typical habitats, there are alpine and subalpine grasslands, dry calcareous grasslands and slopes in upland areas.
Open landscapes such as screes, rocky habitats high in the European mountain ranges such as Alps or Carpathians, are also suitable for Apollo. To maintain stable Apollo populations, the habitat must provide food-plant for the larvae, particularly the Sedum, Serpenvivum and Teleephium sp.
Nowadays, particular Apollo forms and subspecies occupy small areas, sometimes limited to single mountain massive or even hillside, as it was documented in the Alps and the Carpathians.
Parnassius apollo seems to be a quite adaptable species. History shows that it survived dramatic weather changes and even skills to adapt to these changes significantly. That provides hope that this species, with l support and care for its habitat from us, can survive the coming years.