Translocate to establish populations outside of known range

Supporting evidence from individual studies

1. A study in 1979–1980 in an alpine meadow in Colorado, USA (Holdren & Ehrlich 1981, same experimental set up as Boggs et al. 2006) reported that a population of Gillette's checkerspot Euphydryas gillettii translocated outside the species’ native range died out within a year. Immediately after the release of 8,000 eggs and caterpillars, 85–90% of egg masses hatched and began feeding, and at least a third grew to a good size. Ten months later, 14 caterpillars were found feeding on plants where individuals were released, and 85% of bearberry honeysuckle Lonicera involucrata bushes had extensive feeding damage. However, only one adult female and a single egg cluster were found in July, and the egg cluster later disappeared. A later study confirmed that the population did not survive (Boggs et al. 2006). In July 1979, eggs and mated adult females were collected in Wyoming. On 10 July 1979, seventeen females were released in an alpine meadow. A week later, ~8,000 eggs and newly-hatched caterpillars were released on to bearberry honeysuckle at the same site. Egg clusters were taped to the leaves, and caterpillars were released in paper cups. Large plants which were not at risk of flooding were specifically chosen. In May 1980, the site was surveyed for surviving caterpillars, and in June and July it was monitored for adults and egg clusters. A second, successful translocation reported by this study is summarized in 2 - Boggs et al. 2006.

   Study and other actions tested

   Referenced paper

   Holdren C.E. & Ehrlich P.R. (1981) Long range dispersal in checkerspot butterflies: Transplant experiments with Euphydryas gillettii. Oecologia, 50, 125-129.

2. A study in 2001–2002 in one subalpine grassland site in northern Czech Republic (2 - Schmitt et al 2005) found that 69 years after translocation, an introduced population of the small mountain ringlet butterfly Erebia epiphron silesiana had similar genetic diversity to its source population, and higher genetic diversity than a small native population. The mean genetic diversity of adult butterflies from the translocated population (expected heterozygosity (HE): 11.6%) was not significantly different from that of the source population (HE: 10%), and higher than that of a small native population close to the source population (HE: 5.5%). In 1932–1933, about 50 female butterflies were translocated from a native population in the Jeseniky Mountains to a site in the Krkonose Mountains where they had not previously been recorded. In July 2002, researchers collected 81 butterflies from two locations within the range of the translocated population. For comparison, in July 2001 and 2002, they collected 120 butterflies from three locations within the range of the large native source population (>10,000 individuals) and 46 butterflies from a smaller native population (5,000 individuals), both within the Jeseniky Mountains. DNA from these samples was used to measure genetic diversity.

   Study and other actions tested

   Referenced paper

   Schmitt T., Cizek O. & Konvicka M. (2005) Genetics of a butterfly relocation: large, small and introduced populations of the mountain endemic Erebia epiphron silesiana. Biological Conservation, 123, 11-18.

3. A study in 1977–2005 in an alpine meadow in Colorado, USA (Boggs et al. 2006, same experimental set up as Holdren & Ehrlich 1981) reported that a translocated and captive-bred population of Gillette's checkerspot Euphydryas gillettii released outside the species’ native range survived for 28 years, but only increased in size and colonized new sites after 22–25 years. For 21 years after the release of 83 egg clusters, the population size fluctuated between 24 and 143 adults, and remained confined to the release site. However, four years later, the population was estimated at >3,000 adults, and covered 70.4 ha. After a further three years, the population had declined to 150 adults at the release site, but two other habitat patches (0.3 and 0.6 ha) remained occupied (13–153 adults/ha). In July 1977, eggs and adult females were collected in Wyoming, and kept in a laboratory where more eggs were laid. In July–August 1977, eighty-three wild- and captive-laid egg and caterpillar clusters (~10,000 individuals from ~40 females) were released on to bearberry honeysuckle Lonicera involucrata in a 2.25-ha meadow. Details of the translocation taken from Holdren & Ehrlich (1981). In June–July 1978–1989 and 2002–2005, adult butterflies at the release site were caught and uniquely marked every 1–7 days. Recapture rates of marked butterflies were used to estimate the population size in years with sufficient data (1981–1986, 2002–2005). In 1978–1989, 2002 and 2004–2005, egg clusters and/or caterpillar webs were counted throughout the season at the release site, and in 2003–2005 at two newly colonized sites. The relationship between number of egg clusters and adult population was used to estimate the population size in the remaining years. From 1978–1987, areas surrounding the release site were searched for egg clusters or caterpillar webs, and from 2002–2005 a larger area was searched for adults.

   Study and other actions tested

   Referenced paper

   Boggs C.L., Holdren C.E., Kulahci I.G., Bonebrake T.C., Inouye B.D., Fay J.P., McMillan A.N.N., Williams E.H. & Ehrlich P.R. (2006) Delayed population explosion of an introduced butterfly. Journal of Animal Ecology, 75, 466-475.

4. A study in 1999–2008 in two limestone grasslands in Durham and Northumbria, UK (Willis et al. 2009) reported that translocated populations of small skipper Thymelicus sylvestris and marbled white Melanargia galathea survived and spread for eight years after release into climatically suitable areas north of their current range. Six years after release, the distribution of small skipper was 3.64 ha, compared to 0.17 ha in the first year, and the distribution of marbled white was 17.8 ha, compared to 7.2 ha in the first year. Six years after release, the abundance of marbled white was 14 butterflies/km, compared to 6 butterflies/km one year after release. However, most individuals of both species remained within 1 km of their release site. Eight years after release, both populations were still present. In July–August 1999, about 400 adult small skipper were collected from sites in North Yorkshire, and released in a quarry in Northumberland the following day, ~35 km north of the natural range. In July 2000, a further 200 small skipper were translocated to the same site, and ~500 adult marbled white were caught in North Yorkshire and released in a quarry in Durham, ~65 km north of their natural range. Roughly equal numbers of males and females were released. From 2001–2006, extensive searches of each release site and all suitable habitat within 3–4 km were conducted regularly to record adults during their flight period. In 2007–2008, more limited surveys were conducted. Marbled white were also recorded along a 1,550-m transect through their release site every 3–4 days during the flight period (years not given).

   Study and other actions tested

   Referenced paper

   Willis S.G., Hill J.K., Thomas C.D., Roy D.B., Fox R., Blakeley D.S. & Huntley B. (2009) Assisted colonization in a changing climate: A test-study using two U.K. butterflies. Conservation Letters, 2, 46-52.