How Attractive Are Recommended Garden Plants to Butterflies?
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View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Sussex Research Online Garden varieties: How attractive are recommended garden plants to butterflies? Kyle Shackleton & Francis L. W. Ratnieks Journal of Insect Conservation An international journal devoted to the conservation of insects and related invertebrates ISSN 1366-638X J Insect Conserv DOI 10.1007/s10841-015-9827-9 1 23 Your article is published under the Creative Commons Attribution license which allows users to read, copy, distribute and make derivative works, as long as the author of the original work is cited. You may self- archive this article on your own website, an institutional repository or funder’s repository and make it publicly available immediately. 1 23 J Insect Conserv DOI 10.1007/s10841-015-9827-9 SHORT COMMUNICATION Garden varieties: How attractive are recommended garden plants to butterflies? 1 1 Kyle Shackleton • Francis L. W. Ratnieks Received: 30 June 2015 / Accepted: 16 November 2015 Ó The Author(s) 2015. This article is published with open access at Springerlink.com Abstract One way the public can engage in insect con- as nectar sources for butterflies. Furthermore, garden plant servation is through wildlife gardening, including the recommendations can probably benefit from being more growing of insect-friendly flowers as sources of nectar. precise as to the species of butterfly they attract. However, plant varieties differ in the types of insects they attract. To determine which garden plants attracted which Keywords Wildlife gardening Á Butterfly Á Insect butterflies, we counted butterflies nectaring on 11 varieties conservation Á Flowers Á Nectar Á Garden of summer-flowering garden plants in a rural garden in East Sussex, UK. These plants were all from a list of 100 varieties considered attractive to British butterflies, and Introduction included the five varieties specifically listed by the UK charity Butterfly Conservation as best for summer nectar. A Butterflies are an important group of insects that can act as total of 2659 flower visits from 14 butterfly and one moth pollinators and environmental indicators but are facing species were observed. We performed a principal compo- widespread decline (Jennersten 1984; Thomas 2005, Polus nents analysis which showed contrasting patterns between et al. 2007; Thomas et al. 2011; Forister et al. 2010). the species attracted to Origanum vulgare and Buddleia Recent research has drawn attention to the resources but- davidii. The ‘‘butterfly bush’’ Buddleia attracted many terflies use within their habitat (Dennis et al. 2006, Dennis nymphalines, such as the peacock, Inachis io, but very few 2010). One pivotal resource is floral nectar, which is the satyrines such as the gatekeeper, Pyronia tithonus, which primary energy source for adults of most butterfly species mostly visited Origanum. Eupatorium cannibinum had the and can enhance reproduction as nectar amino acids may highest Simpson’s Diversity score of 0.75, while Buddleia compensate for a nutrient-poor larval diet (O’Brien et al. and Origanum were lower, scoring 0.66 and 0.50 respec- 2004; Mevi-Schu¨tz and Erhardt 2005; Cahenzli and tively. No one plant was good at attracting all observed Erhardt 2013). Lack of an adequate nectar supply is butterfly species, as each attracted only a subset of the potentially a limiting factor to butterfly populations and has butterfly community. We conclude that to create a butter- been linked to population declines (Murphy et al. 1983; fly-friendly garden, a variety of plant species are required Wallisdevries and Swaay 2012; Curtis et al. 2015), although probably not all butterfly populations are nectar limited (Thomas et al. 2011). Electronic supplementary material The online version of this Gardens normally contain ornamental flowers that can article (doi:10.1007/s10841-015-9827-9) contains supplementary material, which is available to authorized users. provide nectar and are increasingly being recognised for their value in supporting wildlife (McGeoch and Chown & Kyle Shackleton 1997; Gaston et al. 2007; Dearborn and Kark 2010). In the [email protected] United Kingdom, a study in five major cities found that 99 % of houses were associated with a garden and gardens 1 Laboratory of Apiculture and Social Insects (LASI), School of Life Sciences, University of Sussex, Brighton BN1 9QG, covered at least 20 % of the land area within those cities UK (Loram et al. 2007). Gardens have even been referred to as 123 J Insect Conserv ‘‘England’s most important nature reserve’’ (Owen and Butterfly sampling Owen 1975; Owen 2010). Many gardeners are environ- mentally conscious and seek to balance the aesthetic All data were collected between 09:00 and 18:00 in from 8 attributes of their garden with those that enhance its value to 13 August 2013 during dry, sunny weather at tempera- to wildlife (Gaston et al. 2007; Freeman et al. 2012). This tures of 17–25 °C with zero or light wind when butterflies is termed ‘‘wildlife gardening’’ (Good 2000). were most likely to be active. The survey was carried out There is a huge variety of ornamental flowers available during the period of the Big Butterfly Count, an annual which differ in the number and diversity of insects they citizen science and participation survey organized by attract (Garbuzov and Ratnieks 2015; Garbuzov et al. Butterfly Conservation in the UK (Big Butterfly Count 2015). With such choice, gardeners seeking advice as to 2014). Each patch was visited three times per hour at which species to plant may turn to one of the many lists of intervals of 20 min. A patch was defined as a discrete area ‘‘insect-friendly’’ garden flowers that are available. How- of vegetation where only the focal plant was growing. The ever, an analysis of 15 published lists found several exception to this was Rubus fruticosus (bramble), which shortcomings, including the fact that few were based on was growing in a hedge. During a visit, the observer empirical data or gave any indication as to how they were identified and counted the number of each butterfly species constructed (Garbuzov and Ratnieks 2014a). Overall, there foraging on a patch. The three counts from each hour were is a need for recommended lists of insect-friendly flowers summed for statistical analysis to reduce zero-inflation. We to be put on a firmer scientific basis (Corbet et al. 2001; made a total of 105 visits to each patch resulting in 35 data Garbuzov and Ratnieks 2014b). points (105/3 per hour = 35) for each plant. We emphasise For British butterflies, Vickery (1998) listed and ranked that we counted the number of butterfly ‘‘feeding events’’ ‘‘the 100 best butterfly nectar plants in order of attraction’’. rather than the absolute number of butterflies. Thus, the Five of these are featured on the Butterfly Conservation data represent the flower choices made by the butterflies in website (2014) as ‘‘the best plants for summer nectar’’. the study garden. Vickery (1998) was the only list reviewed by Garbuzov and Ratnieks (2014a) which included information on its Statistical analysis assembly. However, even this list provides little informa- tion on how its recommendations were derived, or which We performed a principal components analysis (PCA) of butterfly species are attracted to which plants. One of the butterfly visits to characterise the structure of the but- Butterfly Conservation’s (2014) five plants is Buddleia terfly community’s choices of plant species. We used the davidii (Franch.), whose common name is the Butterfly prcomp function in R version 3.1.1 (R Core Team 2014)to Bush, implying that is attractive to butterflies in general. In calculate a set of orthogonal standardised linear combina- this study, we surveyed butterflies on 11 varieties of tions (principal components) of the data (Crawley 2013). A ornamental flowers in a garden in East Sussex, UK, in late scree plot was used to determine which principal compo- summer. All 11 were on the list of Vickery (1998), and nents were most important in explaining the variation in the included the five summer varieties recommended by But- data. Additionally, we calculated Simpson’s Diversity terfly Conservation (2014). The aim was not to compare P Index per plant variety, defined as 1 À S niðÞnÀ1 where overall attractiveness to butterflies, but to determine dif- i¼1 NiðÞNÀ1 ferences among plant species in the butterfly species they n is the number of visits of a particular butterfly species and attract. N is the total number of visits of all butterflies. We then compared the plant’s rank (Vickery 1998, Table 1) with total butterfly diversity using Spearman’s rank correlation Methods coefficient. Study site and species Results The study was conducted in a rural garden in the village of Magham Down, East Sussex, England (decimal degrees A total of 2659 Lepidoptera visits were recorded in the 50.880426N, 0.28488247E). The garden included 11 study, made by 14 butterfly and one moth species (see flower varieties listed by Vickery (1998) including the five Supplementary Table A for a full summary). The recorded listed by Butterfly Conservation (2014) as best for summer species are relatively common, and with the exception of nectar (Table 1). All plants were in good condition and in Thymelicus sylvestris (Poda), all appear on the list of 19 full view of the sun. All plants of a given species were of common butterfly species and two moth species surveyed the same colour and variety. in the Big Butterfly Count (Big Butterfly Count 2014). A 123 J Insect Conserv Table 1 List of plant species studied Species name Common name Position in Vickery Listed on Butterfly- No. Total area (1998) conservation.org? patches m2 Buddleia davidii (Franch.) Buddleia 1 Yes 4 5 Origanum vulgare (L.) Marjoram 5 Yes 3 15 Lavendula angustifolia Lavender 3 Yes 2 4 (Mill.) Erysimum bicolor Perennial wallflower ‘Bowles’ 31 Yes 3 7.1 (Hornem.) Mauve Verbena bonariensis (L.) Vervain 26 Yes 3 1.5 Eupatorium cannibinum (L.) Hemp agrimony 17a No 1 1 Nepeta x faassenii Catmint 42 No 3 6 (Bergmans) Rubus fruticosus (Weihe and Bramble 10 No 3 2 Nees) Lythrum salicaria (L.) Purple loosestrife 25 No 5 2.5 Lotus corniculatus (L.) Bird’s foot trefoil 83 No 3 4.2 Dipsacus fullonum (L.) Teasel 55 No 4 2 a In an apparent misprint, E.