Combining modelling, field data and genetic variation to understand the post-reintroduction population genetics of the Marsh Fritillary butterfly (Euphydryas aurinia)

The Marsh Fritillary butterfly (Euphydryas aurinia) is a Eurasian species which has suffered significant reductions in occurrence and abundance over the past century, particularly across the western side of its range, due to agricultural intensification and habitat loss. This loss has been particularly severe in the UK with extensive localised extinctions. Following sympathetic management, reintroduction was undertaken at four Cumbria (northern UK) sites in 2007 with stock from a captive admixture population descended from Cumbrian and Scottish founders. Annual population monitoring of the reintroductions was undertaken. Nine years post-reintroduction, the level of population genetic variation was assessed using microsatellites. Variation in historical Cumbrian samples was determined using museum samples and Scottish samples from current populations were assayed to characterise natural population variation. Half of the Scottish sites also served as indicators of the alleles present in the founder populations. The genetic contribution of the founder populations allied to population size data allowed patterns of genetic variation to be modelled. Alleles from Cumbrian and Scottish founders are present in the reintroduced populations. The four sites have levels of variation akin to natural populations and exhibit differentiation as predicted by statistical modelling and comparable with natural populations. This suggests that reintroduction following captive breeding can produce self-sustaining populations with natural levels of genetic diversity. These populations appear to be undergoing the same evolutionary dynamics with bottlenecks and drift as natural populations. Implications for insect conservation Reintroduction of captive bred individuals is a viable strategy for producing populations with natural levels of genetic diversity and evolutionary dynamics. Hybridisation of populations on the brink of extinction with those thriving can preserve some of the genetic distinctiveness of the declining population.

Gene-flow within a butterfly metapopulation: the marsh fritillary Euphydryas aurinia in western Bohemia (Czech Republic)

In human-altered landscapes, species with specific habitat requirements tend to persist as metapopulations, forming colonies restricted to patches of suitable habitats, displaying mutually independent within-patch dynamics and interconnected by inter-colony movements of individuals. Despite intuitive appeal and both empirical and analytical evidence, metapopulations of only relatively few butterfly systems had been both monitored for multiple years to quantify metapopulation dynamics, and assayed from the point of view of population genetics. We used allozyme analysis to study the genetic make-up of a metapopulation of a declining and EU-protected butterfly, Euphydryas aurinia, inhabiting humid grasslands in western Czech Republic, and reanalysed previously published demography and dispersal data to interpret the patterns. For 497 colony x year visits to the 97 colonies known at that time, we found annual extinction and colonisation probabilities roughly equal to 4%. The genetic diversity within colonies was intermediate or high for all assessed parameters of population genetic diversity and hence higher than expected for such a habitat specialist species. All the standard genetic diversity measures were positively correlated to adult counts and colony areas, but the correlations were weak and rarely significant, probably due to the rapid within-colony population dynamics. Only very weak correlations applied to larval nests numbers. We conclude that the entirety of colonies forms a well-connected system for their majority. Especially in its core parts, we assume a metapopulation structure with a dynamic equilibrium between local extinction and recolonization. It is vital to conserve in particular these structures of large and interconnected colonies.Implications for insect conservation: Conservation measures should focus on considering more in depth the habitat requirements of E. aurinia for management plans and on stabilisation strategies for colonies, especially of peripheral ones, e.g. by habitat restoration.

Caterpillars of the marsh fritillary butterfly Euphydryas aurinia can extend their life-cycle in Scotland

The marsh fritillary Euphydryas aurinia is declining across Europe and is of high conservation interest. Its ecology has been defined and its conservation status assessed primarily from the affinities and populations of young caterpillars in the autumn, before hibernation and high winter mortality. The possibility that caterpillars of E. aurinia can overwinter more than once was investigated on the Isle of Islay, Scotland after caterpillars were found to occur at some locations in the spring despite a pre-hibernation absence. Closely-related species in North America and Northern Europe can prolong larval development by diapausing for a year as does E. aurinia in Scandinavia. Measurements of development and manipulations of distribution confirmed that some caterpillars do extend the life-cycle in Scotland and may occur in areas devoid of larvae in their first year. Caterpillars attempting this life-cycle develop slowly in spring, attain the normal penultimate spring instar and then enter diapause while other caterpillars are pupating. They moult just before diapause, construct highly cryptic webs and on emergence the following spring are 5–6 times heavier than larvae emerging in their first spring, or the equivalent of a month or so ahead. They attain a final, extra instar as larvae in their first spring reach the penultimate instar. Knowledge of this life-cycle is confined in the UK to Islay but its occurrence in this mild climate implies that it is more widespread.Implications for insect conservation Conditions that permit long diapause are probably precise and may not be reflected in recognised qualities of habitat. The species may also be present despite a perceived absence in autumn, the standard period for monitoring. Assessments of the prevalence of the life-cycle and its contribution to the persistence of E. aurinia are required. Populations of E. aurinia are known to fluctuate greatly and do occur below the observation threshold for long periods.

Contribution to the knowledge of the butterfly diversity (Lepidoptera: Papilionoidea) of Kosovo

In terms of Rhopalocera diversity Kosovo is one of the least studied areas in Europe. During 2018 we visited Kosovo on several occasions and gathered a total of 500 records of 98 species of butterflies or 57% of the 171 species known from the area so far. While our survey was not systematic and most localities were visited only once, the data gathered provide an important addition to the butterfly diversity of Kosovo. During this survey some species of European importance such as Lycaena dispar and Euphydryas aurinia were observed, adding to the knowledge about their distribution in the region. 14 of the recorded species are listed in the Red book of the fauna of Kosovo while six are listed in the European Red list of butterflies.

Associations between the larval-pupal parasitoids Erycia furibunda and E. festinans (Diptera: Tachinidae) and respectively, the sympatric and syntopic butterflies Euphydryas aurinia provincialis and Melitaea cinxia (Lepidoptera: Nymphalidae)

Several studies on butterfly ecology and biology of Melitaeini butterflies have been carried out in the past, however the factors affecting butterfly mortality and the role of natural enemies on population dynamics are not yet fully known. Larval survival plays a key role in determining butterfly population size and distribution range; thus, knowing the sources and variation in larval mortality is essential understanding and predicting population dynamics. Butterfly larval mortality is generally ascribed to abiotic factors, predators and parasitoids (mainly Diptera and Hymenoptera). Among Diptera, tachinids parasitize primarily larval Lepidoptera. In this paper, we report the results of 5-year observations in the wild and captivity on the tachinids, Erycia furibunda and E. festinans, parasitoids of caterpillars of a population of Euphydryas aurinia spp. provincialis and Melitaea cinxia in Central Italy revealing their host specifity. The hosts, E. aurinia and M. cinxia, and parasitoids, E. furibunda and E. festinans, inhabit the same habitat and their life cycles highly overlap, nevertheless, the parasitoids maintain their host specifity: E. furibunda as parasitoid of E. aurinia; E. festinans as parasitoid of M. cinxia. This was confirmed by our findings during the butterfly breeding activities carried out for over five years. Although the role of chemical cues in host finding requires further research, according to our observations the presence of only E. furibunda on larval webs of E. aurinia let us suppose that the mechanism by which E. furibunda locates its host could be based on olfactory cues emitted by feeding damage to host plants that act from afar. Similarly, the mechanism of host finding used by E. festinans could act to select its host, M. cinxia. Furthermore, we illustrate some diagnostic features of adults for the identification of the studied parasitoids.

Parasitoid wasps indicate that the marsh fritillary butterfly (Euphydryas aurinia) has persisted on Tiree rather than re-colonised recently

The population of the marsh fritillary butterfly (Euphydryas aurinia) in western Scotland fluctuates greatly and the species is difficult to locate during periods of scarcity. It was recorded on Tiree in 2014 for the first time in 64 years during a period of abundance. The nearest known populations occur 40 km to the east and its discovery represents either a recent colonisation event well beyond its known capability or it has escaped detection for a longer period. Surveys for the larval cocoons of two wasps that are parasitoids of E. aurinia and host-specific were undertaken on Tiree in spring and autumn 2017. The adult wasps are small with limited powers of dispersal and are unlikely to have followed E. aurinia to Tiree since 2014. Cocoons of one species - Cotesia melitaearum – were abundant in all concentrations of E. aurinia in spring 2017 but neither species was found in the autumn. The absence of the second species - C. bignellii - is inconclusive as it was also absent at known locations elsewhere in autumn 2017. The occurrence, distribution and abundance of C. melitaearum on Tiree indicate that E. aurinia had been present for some time before its discovery in 2014. Although continuous presence since 1950 cannot be extrapolated with certainty, the results highlight the propensity of E. aurinia to persist for long periods in numbers that fall below the observation threshold, even in areas of high wildlife awareness, and that it is not always an easy species to record.