First data on the host ant usage of Large Blue from the Carpathian Basin

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Changes in host ant communities of Alcon Blue butterflies in abandoned mountain hay meadows

1. Land use intensification is a general threat to biodiversity, but many species depend on low-intensity agricultural ecosystems. One example is European mountain meadow ecosystems, traditionally managed by hay harvesting or livestock grazing. Abandoning management often causes population declines, local extinctions and biotic homogenisation in these meadows. 2. We studied changes in the Myrmica host ant communities of the xerophilic form of the ant-parasitic Alcon Blue butterfly (Maculinea alcon) in four hay meadows in the Bükk mountains of Hungary between 2000–2007 and 2018. Abandonment started in this region in the 1970s, accelerated in the 1980s, and culminated in the 1990s. 3. We found that the Myrmica ant community has changed substantially in less than two decades. Diversity of the ant community always decreased, and species composition became more homogeneous at two sites. Habitat suitability for Maculinea butterflies decreased at three sites and increased at only one site, where management was restarted 20 years after abandonment. 4. The number of M. alcon caterpillars and pupae, the rate of infestation of ant nests and the mean number of caterpillars and pupae per ant nest decreased between the two periods, whereas host ant specificity did not differ from random in either period. 5. We conclude that the unfavourable changes in the host ant community due to abandonment have negative consequences for the persistence of Maculinea populations. Our study highlights the need for detailed monitoring, and the maintenance of low-intensity management by mowing or grazing to avoid the decline of biodiversity dependent on low-intensity agriculture

Evidence of a fixed polymorphism of one-year and two-year larval growth in the myrmecophilous butterfly Maculinea rebeli

1. Maculinea (= Phengaris) species of butterfly have complex life-styles in which the larvae feed briefly on specific foodplants before entering the final instar, after which they live as social parasites within Myrmica ant colonies and acquire 98–99% of their ultimate biomass by either preying on ant brood (predatory species) or being fed by worker ants (cuckoo species). Cuckoo species demonstrate two growth forms, whereby some individuals develop to pupate in 11 months and others remain 23 months in the nest, a strategy that in theory represents the most efficient exploitation of resources within Myrmica societies. Early studies suggested that development rates in Maculinea rebeli (referred to by other authors as the xerophilous form of Maculinea alcon) were not plastic but represented an unusual fixed polymorphism, in which eggs were genetically predetermined as 1- or 2-year larvae. 2. We tested this idea in lab experiments using M. rebeli from the French HautesAlpes, with these results: (i) the growth strategy of every individual larva is predetermined by the mother either genetically or, less probably, during oogenesis. (ii) Intra-nest competition and host fitness affects survival and growth but does not influence the inherent growth strategy. (iii) The ratio of 1- and 2-year developing larvae is initially about 50:50, although differential survival in crowded nests may alter the ratio of surviving individuals. (iv) All females tested laid eggs that hatched into both 1- or 2-year developers. (v) Growth patterns vary between different regions. Larvae from the Spanish Pyrenees initially grow less than those from the Alps, with a smaller initial differentiation between the size classes

The Evolution of Invasiveness in Garden Ants

It is unclear why some species become successful invaders whilst others fail, and whether invasive success depends on pre-adaptations already present in the native range or on characters evolving de-novo after introduction. Ants are among the worst invasive pests, with Lasius neglectus and its rapid spread through Europe and Asia as the most recent example of a pest ant that may become a global problem. Here, we present the first integrated study on behavior, morphology, population genetics, chemical recognition and parasite load of L. neglectus and its non-invasive sister species L. turcicus. We find that L. neglectus expresses the same supercolonial syndrome as other invasive ants, a social system that is characterized by mating without dispersal and large networks of cooperating nests rather than smaller mutually hostile colonies. We conclude that the invasive success of L. neglectus relies on a combination of parasite-release following introduction and pre-adaptations in mating system, body-size, queen number and recognition efficiency that evolved long before introduction. Our results challenge the notion that supercolonial organization is an inevitable consequence of low genetic variation for chemical recognition cues in small invasive founder populations. We infer that low variation and limited volatility in cuticular hydrocarbon profiles already existed in the native range in combination with low dispersal and a highly viscous population structure. Human transport to relatively disturbed urban areas thus became the decisive factor to induce parasite release, a well established general promoter of invasiveness in non-social animals and plants, but understudied in invasive social insects

Patterns of host use by brood parasitic Maculinea butterflies across Europe

The range of hosts exploited by a parasite is determined by several factors, including host availability, infectivity and exploitability. Each of these can be the target of natural selection on both host and parasite, which will determine the local outcome of interactions, and potentially lead to coevolution. However, geographical variation in host use and specificity has rarely been investigated. Maculinea (=Phengaris) butterflies are brood parasites of Myrmica ants that are patchily distributed across the Palæarctic and have been studied extensively in Europe. Here, we review the published records of ant host use by the European Maculinea species, as well as providing new host ant records for more than 100 sites across Europe. This comprehensive survey demonstrates that while all but one of the Myrmica species found on Maculinea sites have been recorded as hosts, the most common is often disproportionately highly exploited. Host sharing and host switching are both relatively common, but there is evidence of specialization at many sites, which varies among Maculinea species. We show that most Maculinea display the features expected for coevolution to occur in a geographic mosaic, which has probably allowed these rare butterflies to persist in Europe

Patterns of host use by brood parasitic Maculinea butterflies across Europe

The range of hosts exploited by a parasite is determined by several factors, including host availability, infectivity and exploitability. Each of these can be the target of natural selection on both host and parasite, which will determine the local outcome of interactions, and potentially lead to coevolution. However, geographical variation in host use and specificity has rarely been investigated. Maculinea (=Phengaris) butterflies are brood parasites of Myrmica ants that are patchily distributed across the Palæarctic and have been studied extensively in Europe. Here, we review the published records of ant host use by the European Maculinea species, as well as providing new host ant records for more than 100 sites across Europe. This comprehensive survey demonstrates that while all but one of the Myrmica species found on Maculinea sites have been recorded as hosts, the most common is often disproportionately highly exploited. Host sharing and host switching are both relatively common, but there is evidence of specialization at many sites, which varies among Maculinea species. We show that most Maculinea display the features expected for coevolution to occur in a geographic mosaic, which has probably allowed these rare butterflies to persist in Europe