Dragonfly Responses to Landscape Cover
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TSPACE RESEARCH REPOSITORY tspace.library.utoronto.ca Version: Postprint (Accepted Manuscript) 2019 Te Movement Responses of Tree Libellulid Dragonfy Species to Open and Closed Landscape Cover Sarah K. French and Shannon J. McCauley Funding Information: Te Teodore Roosevelt Memorial Fund of the American Museum of Natural History and Queen Elizabeth II/Pfzer Graduate Scholarship in Science and Technology with funding from the Departments of Ecology & Evolutionary Biology at the University of Toronto and the Department of Biology at University of Toronto Mississauga awarded to SKF. Te Canada Foundation for Innovation, Ontario Research Fund (31974), and Natural Sciences and Engineering Research Council of Canada (RGPIN435614) awarded to SJM. License: Te Accepted Manuscript (AM), the fnal draft of this author manuscript, is licensed under Attribution- NonCommercial 4.0 International (CC BY-NC 4.0). To view the details of this license, visit https://creativecommons.org/licenses/by-nc/4.0/ Important Notes Always cite the Version of Record (VoR: fnal publisher’s version) so that the author(s) will receive recognition through services that track citation counts, e.g., Scopus. When you are unable to access the VoR, the citation needs to include the word, Postprint (Accepted Manuscript). Visit Publisher’s Site for the VoR: https://doi.org/10.1111/icad.12355 (Wiley) 1 This is an Accepted Manuscript of an article published by Wiley in Insect Conservation and Diversity in May 2019, available online: https://doi.org/10.1111/icad.12355 1 Title: The movement responses of three libellulid dragonfly species to open and closed 2 landscape cover 3 4 Running title: Dragonfly responses to landscape cover 5 6 Author details: 7 Sarah K. French1,2,3 8 Shannon J. McCauley1,2 9 1Department of Biology, University of Toronto Mississauga, 3359 Mississauga Road, 10 Mississauga, ON, Canada, L5L 1C6. 11 2Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, 12 Toronto, ON, Canada, M5S 3B2. 13 3Present address: Department of Biology, University of Waterloo, 200 University Avenue West, 14 Waterloo, ON, Canada, N2L 3G1 15 16 Correspondence: Sarah K. French. E-mail: [email protected] 2 17 Abstract 18 1.The land cover between habitats (i.e. matrix environment) can affect connectivity by impacting 19 organismal movement. However, many animals have preferences for specific matrix 20 environments, which can affect their movement through the landscape. 21 2.We examined how different terrestrial matrix environments impacted the fine-scale movement 22 of adult dragonflies. Based on previous studies of adult dragonfly dispersal and larval 23 distributions, we hypothesized that dragonflies would prefer to enter fields rather than forests, 24 and that forests would be a barrier to dragonfly movement, due to forests’ structural complexity, 25 low understory light availability, and lower air temperatures. 26 3.To test how adult dragonflies responded to various terrestrial environments, we released 108 27 Leucorrhinia intacta, a mixture of 108 Sympetrum rubicundulum and obtrusum/rubicundulum 28 hybrids, and 108 Sympetrum vicinum, at field-forest ecotones and assessed their preferences for 29 fields or forests. Individual behavioural responses were recorded, including their probability of 30 taking flight, their direction of movement with respect to the two matrix types, and flight time. 31 4.The likelihood of adult dragonflies taking flight was species-specific in response to release 32 location. Adults moved more frequently towards fields than forests when released at a forest 33 edge. Individuals released within forests had shorter flight times, but again this response was 34 species-specific. 35 5.The presence of an open matrix (field or meadow) is likely important for facilitating movement 36 in dragonflies, however forests are not movement barriers for all dragonfly species. Integrating 37 assays of matrix and habitat preferences can provide insight into how landscape connectivity can 38 be maintained for actively dispersing species. 39 Keywords: Forest cover, behaviour, matrix, dispersal, Odonata 3 40 Introduction 41 In heterogeneous landscapes, patches of habitat where a focal species lives are 42 surrounded by compositionally similar and dissimilar (i.e. matrix) environments (Forman & 43 Godron, 1981, 1986; Kracker, 1999). A matrix environment can promote or restrict organismal 44 movement (Ricketts, 2001; Murphy & Lovett-Doust, 2004; Prugh et al., 2008). The behavioural 45 responses of individuals to a matrix environment can therefore provide critical insight into how 46 species move through, use, and distribute themselves across heterogeneous landscapes. Few 47 studies connect individual-based behaviour to processes seen at the community and landscape 48 scale (Lima & Zollner, 1996; Bélisle, 2005; Gordon, 2011). Yet, observations of these 49 behaviours at a local scale have been useful in explaining organismal movement (e.g. pumas; 50 Zeller et al., 2014), dispersal (e.g. butterflies; Haddad, 1999), and species coexistence (e.g. 51 warblers; Toms, 2013). Indeed, the integration of behaviour and larger scale patterns can be 52 informative in predicting species’ distributions and responses to environmental change 53 (Knowlton & Graham, 2010). 54 Heterogeneous matrix environments may provide differential costs and benefits to 55 individuals moving through the landscape (Chardon et al., 2003). The suitability of, or 56 preference for, specific types of matrix environments by species and individuals can vary 57 depending on the risks and gains that organisms experience while moving through these 58 environments, whether during rare and long-distance movements from a source habitat to a new 59 habitat (i.e. dispersal) or during short-distance movements that occur frequently (e.g. daily 60 foraging). This landscape of costs and benefits may be complex and drive non-intuitive patterns 61 of movement. For example, matrix environments that provide resources or refuge may be 62 preferred to ones that are easy to move through, despite the costs imposed by the difficulty of 4 63 moving through these environments (Haynes & Cronin, 2006; Prugh et al., 2008; Kuefler et al., 64 2010). One type of matrix in terrestrial landscapes that has dramatic effects on the movement of 65 organisms is forest cover (e.g. Ricketts, 2001; Driscoll et al., 2013; Damschen et al., 2014). 66 Some species preferentially move through forests. For example, green hermit hummingbirds 67 (Phaethornis guy, Apodiformes) prefer to move through forested corridors, possibly due to 68 increased resource availability (Volpe et al., 2016), and some species of the Ambystoma 69 salamander (Caudata) preferentially move through forests rather than fields in order to avoid 70 desiccation (Rothermel & Semlitsch, 2002; Rittenhouse & Semlitsch, 2006). Yet, forests can also 71 increase the risk of mortality (e.g. Phengaris spp., Lepidoptera; Nowicki et al., 2014) or restrict 72 movement (e.g. Leucorrhinia hudsonica, Odonata; Chin & Taylor, 2009). Forests can also be 73 energetically costly for organisms to manoeuvre through due to their structural complexity (e.g. 74 for Bombus impatiens, Hymenoptera; Crall et al., 2015), and in the case of ectotherms, due to the 75 reduced solar radiation available for thermoregulation (e.g. large-bodied dragonfly species; De 76 Marco et al., 2015). Forest cover is also rapidly changing worldwide: some regions are 77 experiencing high levels of forest regrowth whereas in other regions, forest is being lost (Foster 78 et al., 1998; Hansen et al., 2013). Both types of changes may alter how organisms move in the 79 landscape. 80 Terrestrial matrix conditions are similarly important for semi-aquatic insects, many of 81 which have an aquatic larval stage and a terrestrial life history stage. In these taxa, survival and 82 post-colonization distributions can depend on the permeability of the matrix (e.g. Joly et al., 83 2001; Semlitsch, 2008). Our study taxon, dragonflies (three species in the family Libellulidae), 84 use terrestrial systems as adults to make frequent daily movements of over 50 m for activities 85 such as foraging and moving between roosting and reproductive habitats (Eason & Switzer, 5 86 2006), and also to disperse to aquatic habitats where they mate and lay eggs (Switzer, 2002). 87 Dragonflies are a good model taxon for understanding behavioural responses to changes in the 88 landscape, as adults frequently disperse to and establish at new aquatic habitats (Oertli, 2008), 89 and may exhibit differential responses to habitat heterogeneity. For example, forests can obstruct 90 adult dragonfly dispersal to aquatic reproductive habitats at distances ≥ 500 m (Chin & Taylor, 91 2009), and can restrict their arrival at aquatic habitats (Remsburg et al., 2008; French & 92 McCauley, 2018). At shorter distances however (e.g. 125 m), forests do not seem to impede 93 movement to aquatic habitats (Chin & Taylor, 2009). The behavioural mechanisms behind this 94 pattern of increased connectivity at small scales, among dragonfly breeding habitats with an 95 intervening forest matrix, remain unclear. Forests may be beneficial at these small scales, 96 whether by facilitating dragonfly movement (Chin & Taylor, 2009), or by providing resources or 97 refuge. Some species of dragonfly use forest edges to roost during their inactive overnight period 98 (Corbet, 1999; Timofeev, 2016), to take refuge from the heat and/or to bask (Paulson, 2009),