Abstract
Simple SummaryThe endangered Alcon blue butterfly (Phengaris alcon) starts its larval stage by feeding on the seeds of gentian plants, after which it completes development in the nests of suitable Myrmica ant species. Any particular population often uses more than one host ant species, and some host switching is likely. To test switching in the lab we introduced relatively strong colonies of alien Myrmica species to the arenas of weaker colonies, and to orphaned caterpillars. Most of the caterpillars were successfully readopted by alien ants, and survived well. Our results suggest higher ecological plasticity in host ant usage of this butterfly than generally thought. The Alcon blue is an iconic species, e.g., its special life cycle has featured in several high profile television and streaming media wildlife series, and the more we know about its unusual life the more we can do for its protected sites.The socially parasitic Alcon blue butterfly (Phengaris alcon) starts its larval stage by feeding on the seeds of gentians, after which it completes development in the nests of suitable Myrmica ant species. The host plant and host ant species can differ at the population level within a region, and local adaptation is common, but some host switches are observed. It has been suggested that one mechanism of change is through the re-adoption of caterpillars by different ant species, either through occupation of abandoned nests or take-over of established nests by competitively superior colonies. To test this question in the lab we introduced relatively strong colonies (50 workers) of alien Myrmica species to the arenas of weaker colonies (two caterpillars with six workers), and to orphaned caterpillars (two caterpillars without ants). We used caterpillars from a xerophylic population of P. alcon, and both local hosts, M. sabuleti and M. scabrinodis, testing the possibility of host switch between these two host ant species during larval development. Most of the caterpillars were successfully readopted by alien ants, and survived well. Our results suggest higher ecological plasticity in host ant usage of this butterfly than generally thought.
Highlights
Different forms of social parasitism are well known to affect all insect taxa that live socially, where the social parasites exploit the host’s parental efforts [1]
The two in which they did not do so were both cases in which M. sabuleti was the foreign ant, but unsurprisingly trials in which they did not do so were both cases in which M. sabuleti was the foreign ant, but givenunsurprisingly the rarity of this difference outcomes foroutcomes the two for Myrmica givenoutcome, the rarity the of this outcome,between the difference between the twospecies
Sources of variation in survivorship were: Foreign ant species—The introduced introduced Myrmica species, either M. scabrinodis or Myrmica species, either M. scabrinodis or M. sabuleti
Summary
Different forms of social parasitism are well known to affect all insect taxa that live socially, where the social parasites exploit the host’s parental efforts [1]. Many social parasites from a wide variety of insect orders, and even different phyla, are known to exploit ants [2]. Myrmica ants (Hymenoptera: Formicidae) host especially diverse forms of social parasite [3]. Phengaris (=Maculinea; Lepidoptera: Lycaenidae) butterflies are probably the most intensively studied social parasites of Myrmica ants [4]. The caterpillars of these butterflies start their development feeding. Insects 2020, 11, 556 on the developing seeds of specific host plants. In the final-instar the caterpillars leave the initial food plant and mimic the odour [5,6,7,8] and the sound [9] of certain Myrmica species, so as to be “adopted”
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