© Entomologica Fennica. 3 October 2012 Can brief marking campaigns provide reliable dispersal estimates? A Nickerl’s Fritillary (Melitaea aurelia, Lepidoptera: Nymphalidae) case study David Novotný, Martin Konvièka & Zdenìk Fric Novotný, D., Konvièka, M., Zdenìk, F. (2012) Can brief marking campaigns provide reliable dispersal estimates? A Nickerls Fritillary (Melitaea aurelia, Lepidoptera: Nymphalidae) case study. Entomol. Fennica 23: 155164. Functions expressing dispersal probability decays with increasing distance are widely used in studies of animal movements. The inverse power function (IPF) exhibits the property of self-similarity, and hence should perform robustly against variation in marking efforts, allowing comparisons across studies. We in- vestigated this function property using dispersal data of Nickerls fritillary (Melitaea aurelia), a little studied checkerspot butterfly which is currently ex- panding in Central Europe. During mark-recapture in South Moravia, Czech Re- public, a single researcher worked for the entire flight period in 2005, while in 2006 five researchers worked for just 5 days. Slopes of the fitted functions did not differ between the two seasons, illustrating the robustness of the function and suggesting the possibility to obtain reliable dispersal estimates even from brief marking campaigns. For both years, it was predicted that approximately one indi- vidual per one thousand would cross 10 km distance, the maximum distance sep- arating the most isolated colonies in the region. D. Novotný*, M. Konvièka & Z. Fric, Biology Centre of the Academy of Sciences of the Czech Republic andUniversity of South Bohemia, Faculty of Science, Braniovská 31, 37005, Èeské Budìjovice, Czech Republic; *Corresponding au- thors e-mail: [email protected] Received28 November 2011, accepted26 January 2012 1. Introduction cesses, unless saved by occasional colonisation (Hanski 1999). Studies on model groups such as The awareness of insect losses from habitat frag- butterflies have provided ample evidence that in ments surrounded by human dominated land- such isolated populations losses indeed occur scapes, such as the intensive farmlands of West- (Wenzel et al. 2006, Leidner & Haddad 2011). ern and Central Europe, has raised interest in in- The data amassed in empirical butterfly dispersal sect dispersal, or mobility related to gene flow studies, using a variety of approaches from classi- (Habel et al. 2009, Hanski & Mononen 2011). cal mark-recapture to molecular and electronic Losses from habitat fragments are explicable by tools, are now allowing broad generalisations the metapopulation theory, which predicts that which link dispersal to species life histories and small local populations are prone to eventual ex- aim to assist practical conservation (Hovestadt & tinctions due to deterministic or stochastic pro- Nieminen 2009, Stevens et al. 2010, Sekar 2012). 156 Novotný et al. ENTOMOL. FENNICA Vol. 23 Fig. 1. Schematic rep- resentation of dánický les hills, Czech Repub- lic, showing the study site, the distribution of xeric grasslands, and their occupancy by Melitatea aurelia within the mostly intensively farmed, or forested, area. Checkerspot butterflies (Nymphalidae: Meli- 2002), but is currently re-expanding to histori- teaeinae) represent a popular model in population cally occupied regions (Germany: Eichel & ecology (e.g., McLaughlin et al. 2002, Hellmann Fartmann 2008, the Czech Republic: Spitzer & et al. 2003, Ehrlich & Hanski 2004, Bulman et al. Bene 2010). It hence offers an excellent compar- 2007, Zimmermann et al. 2011). They often form ison with much more studied, but recently declin- spatially distinct colonies, are easily detectable ing, checkerspots. both as larvae and adults, are rather poor fliers Mobility studies based on capture-mark-re- and occur in high densities. At the same time, they capture often miss rare long-range movements display a remarkable diversity of life history traits (Baguette & Schtickzelle 2003, Zimmermann et (Ehrlich & Hanski 2004), which transfers into al. 2011), instrumental in the recolonisation/ex- varying levels of threat from intensive land use. pansion processes. Franzen and Nilsson (2007) Some European species are among the most en- recommended that a sampling area as large as 100 dangered butterflies on the continent (e.g., Eu- km2 is necessary to estimate lepidopteran phydryas maturna, cf. Freese et al. 2007), while (re)colonisation ability. A way to overcome this others vary in status regionally (e.g. Melitaea logisticlimitation is to use dispersal kernel func - athalia, cf. Hodgson et al. 2009). An interesting tions, predicting long-range movements from case in Central Europe is Melitaea aurelia short-range ones. This does not fully eliminate Nickerl, 1850. This xeric grasslands specialist the problem with undetected long-range dis- has declined severely during the 20th century persal, but at least allows comparisons among (e.g., Van Swaay & Warren 1999, Bene et al. species, sexes, regions and seasons (Fric et al. ENTOMOL. FENNICA Vol. 23 Dispersal estimate in brief marking campaign 157 2010). Contributing to the debate (e.g., Baguette corded to date, including 17 nationally threatened et al. 2000, Kuras et al. 2003) on the appropriate ones, according to unpublished Czech Butterfly shape of dispersal kernel functions, Fric and and Moths Recording data), complex land-hold- Konvièka (2007) showed that a particular func- ing patterns have so far prevented legal protec- tion form, the inverse power function (IPF), is tion. A part of the dry grassland area is actively particularly robust to variation in the marking ef- managed by conservation volunteers. fort, owing to the scale invariance of the function slope; i.e., the parameter expressing decay of dis- persal with distance. 2.2. Study species The scale invariance of IPF offers an attrac- tive possibility to collect reliable dispersal data Melitaea aurelia is a univoltine butterfly, dis- with reduced marking effort and to compare dis- playing colonial distribution at short-bladed xeric persal data collected under varying study circum- grasslands with a high cover of its host plant, stances. We examined this by performing a two- Plantago media L. (Eichel & Fartmann 2008). seasons mark-recapture study targeting move- Females lay small egg batches on the underside of ment patterns in a strong M. aurelia population host plant leaves, larvae are gregarious until au- inhabiting xericgrasslands in the CzechRepub - tumn. Its total distribution stretches from France lic. In the first season, we followed a traditional through Central and Eastern Europe, Transcau- approach, marking the population during the en- casia, the Southern Urals and Siberia up to the tire flight period. In the second season, we sub- Tian Shan region (Tolman & Lewington 2008). stantially increased the study area, restricted In the Czech Republic, a decline during the 20th marking to peak adult flight, and increased per- century has restricted its distribution to the warm- day marking intensity. Here, we (1) describe the est regions of the country, but recent records doc- basicdemography and movement patterns in the ument a return of the species to parts of its former population of M. aurelia, and (2) assess the ro- range. bustness of the movement estimates obtained while following different marking protocols. 2.3. Mark-recapture data We worked in four adjoining valleys with a total 2. Material and methods dry grasslands area of 51 ha, divided into eleven subsites for the purpose of dispersal analysis (Fig. 2.1. Study system 1). Two adjoining valleys (32 ha) were covered by marking in 2005, and two others (19 ha) were The study was carried out in a system of valleys at added in 2006. the southern slopes of the Zdanicky les hills In 2005, the marking covered the entire adult (49°05N, 17°02E, altitude 245330 m), South- flight period (25. VI28. VII), every day with fa- ern Moravia, SE Czech Republic. While most of vourable weather, from 10:00 to 17:00 (CEST). Southern Moravia consists of intensively farmed Each netted butterfly was assigned a numeric lowlands, Zdanicky les is a ridge (maximum alti- code and released at its point of capture. A single tude 437 m), formed by base-rich Carpathian person carried out the marking, working for 32 flysch and covered by oak-hornbeam and beech person-days in total. forests. Its south-facing valleys, historically cov- In 2006, the marking was limited to the peak ered by a patchwork of gardens, hay meadows, of adult flight season (5.9.VII), but covered an orchards and pastures, were largely abandoned expanded area. Five persons did the marking each several decades ago, and now are in varying day, resulting in the total marking effort of 25 per- stages of succession. The prevailing vegetation is son-days. Daily marking intensity, i.e. the num- classified as Bromion erecti dry grasslands, Ge- ber of marking persons per day and unit area, was ranion sanguinei forb-rich mantles, and Berbe- 3.6 times higher in 2006 than in 2005 (5-fold in- ridion xericscrub(Chytrý et al. 2001). Despite crease in persons marking, but covering an area high bioticdiversity (e.g., 74 butterfly speciesre - 1.37 times larger). 158 Novotný et al. ENTOMOL. FENNICA Vol. 23 Fig. 2. Daily numbers of captures of Melitaea aurelia males and fe- males.–a.In2005. – b. In 2006. The ar- rows in panel (a) show the 2005 days pheno- logically corresponding to the five marking days in 2005. 2.4. Demography estimates ments, lumped them into 50-m distance