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Macquarie University PURE Research Management System This is the peer reviewed version of the following article: Yadav, S., Stow, A. and Dudaniec, R.Y. (2020), Elevational partitioning in species distribution, abundance and body size of Australian alpine grasshoppers (Kosciuscola). Austral Ecology, vol. 45, no. 5, pp. 609-620. which has been published in final form at: doi.org/10.1111/aec.12876 This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. 1 Elevational partitioning in species distribution, abundance and body size of Australian 2 alpine grasshoppers (Kosciuscola) 3 4 Sonu Yadav1*, Adam Stow1, Rachael Y. Dudaniec1 5 6 1 Department of Biological Sciences, Macquarie University, North Ryde, 2109, NSW, 7 Australia 8 9 *Corresponding author: 10 11 Sonu Yadav, Department of Biological Sciences, Macquarie University, North Ryde, 2109, 12 NSW, Australia, Email- [email protected] 13 14 Acknowledgments 15 We thank Kate D. L. Umbers for help with field work protocols and useful discussions. We 16 thank Justin McNab for help with fieldwork, Rachel Slatyer for providing useful information 17 on the species occurrence and Giselle Muschett for helping with species identification. We 18 thank Youning Su from the Australian National Insect Collection, CSIRO museum, Canberra 19 for providing access to type specimens. This project was funded by Macquarie University 20 with start-up funding to R.Y.D., a Macquarie graduate student research grant to S.Y, a 21 Holsworth Wildlife Research Endowment grant from the Ecological Society of Australia (to 22 SY), the Theodore J. Cohn Research Fund from the Orthopterist’s Society (to SY) and the 23 Joyce W. Vickery Scientific Research Fund from The Linnean Society of NSW (to SY). All 24 procedures were performed in accordance with the animal ethical guidelines of Macquarie 25 University, Australia, and sampling permissions were obtained from local government 26 authorities and national parks (License number: SL101832). 27 Abstract 28 Changes in the physical environment with elevation can influence species distributions and 29 their morphological traits. In mountainous regions, steep temperature gradients can result in 30 patterns of ecological partitioning among species that potentially increases their vulnerability 31 to climate change. We collected data on species distributions, relative abundance and body 32 size for three grasshopper species of the genus Kosciuscola (K. usitatus, K. tristis, and K. 33 cognatus) at three locations within the mountainous Kosciuszko National Park in Australia 34 (Thredbo, Guthega and Jagungal). All three species showed differences in their distributions 35 according to elevation, with K. usitatus ranging from 1400 m asl to 2000 m asl, K. tristis 36 from 1600 m asl to 2000 m asl, and K. cognatus from 1550 m asl to 1900 m asl. Decreasing 37 relative abundance with increasing elevation was found for K. usitatus, but the opposite 38 pattern was found for K. tristis. The relative abundance of K. cognatus did not change with 39 elevation but was negatively correlated with foliage cover. Body size decreased with 40 elevation in both male and female K. usitatus, which was similarly observed in female K. 41 tristis and male K. cognatus. Our results demonstrate spatial partitioning of species 42 distributions and clines in body size in relation to elevational gradients. Species-specific 43 sensitivities to climatic gradients may help to predict the persistence of this grasshopper 44 assemblage under climate change. 45 46 Keywords 47 Australian Alps, Kosciuscola, Orthoptera, relative abundance, body size 48 Introduction 49 Alpine species are often adapted to narrow thermal ranges, making them sensitive to 50 increasing temperatures (Laurance et al, 2011; Williams et al, 2008) and more likely to be 51 adversely affected by climate change (Dirnböck et al, 2011; La Sorte & Jetz, 2010). Alpine 52 ecosystems show sharp clines in climatic characteristics leading to changes in the 53 composition and diversity of biota at fine spatial scales (Beccacece et al, 2016; Hilt & 54 Fiedler, 2005; Sundqvist et al, 2013; Zenker et al, 2015). Changes in species composition and 55 diversity along elevation gradients have been reported for several taxa (moths: Brehm & 56 Fiedler, 2003; dung beetles: Herzog et al, 2013; plants: Mota et al, 2018; birds: Rahbek, 57 1997; Zenker et al, 2015), and climate, topography and productivity are among the major 58 drivers of such changes (Currie & Kerr, 2008; Lomolino, 2001; Ramirez-Bautista & 59 Williams, 2019). Species’ physiological tolerances and microhabitat usage are further 60 contributors (Birkett et al, 2018; Röder et al, 2017; Wachter et al, 1998; Werenkraut & 61 Ruggiero, 2014), whereby specialist species with narrow distributions and narrow thermal 62 niches are expected to show increased sensitivity to shifts in climatic conditions (Hoffmann, 63 2010). Therefore, knowledge of the fine-scale distributions of species within alpine 64 environments is necessary for assessing their vulnerability to climate change. 65 66 Species distributed along environmental gradients are often observed with morphological 67 changes such as intraspecific colour polymorphism and variation in body size, particularly in 68 insects (Sheridan & Bickford, 2011; Whitman, 2008; Yadav et al, 2018). Body size is an 69 important trait related to fitness, survival, growth, and physiology (Chown & Gaston, 2010; 70 Kleiber, 1947) and may therefore influence the relative success of certain species within 71 species assemblages in variable environments. Body size in ectotherms, including insects, is 72 generally positively correlated with temperature with smaller individuals in cooler climates 73 (Berner & Blanckenhorn, 2006; Buckley et al, 2014; Mousseau, 1997; Telfer & Hassall, 74 1999), however no single consistent pattern has been found across the insect taxa (Brehm et 75 al, 2018; Maveety & Browne, 2014). This inconsistency indicates that the underlying 76 mechanisms controlling body size may vary across species and locations. 77 Insects frequently show sexual size dimorphism, with females typically being the 78 larger sex (Chown & Gaston, 2010) including in Orthoptera (Hochkirch & Gröning, 2008). 79 Males and females may show distinct variations in body size along environmental gradients, 80 potentially due to sex-specific selection pressures (Fairbairn, 1997; Stamps, 1993; Teder & 81 Tammaru, 2005) or altered developmental periods along temperature gradients (Fairbairn et 82 al, 2007; García-Navas et al, 2017; Laiolo et al, 2013). Due to a strong association between 83 environmental variables (for e.g. temperature) and variation in dimorphism in insects 84 (Davidowitz et al, 2004; Stillwell et al, 2007b), the pattern of dimorphism may vary or shift 85 with changing environmental conditions. Understanding sex-specific variation in body size 86 along elevation gradients may therefore provide insight into the environmental mechanisms 87 generating clinal distributions within species assemblages. 88 89 Alpine ecosystems are particularly susceptible to climate change (Gobiet et al, 2014; IPCC, 90 2014) and the Australian Alps are no exception. Since 1979 the Australian Alps have 91 experienced a decline in precipitation by 6%, an increase in temperature at an average of 92 0.4°C since 1954 along with a substantial decline in snow depth (Hennessy et al, 2003; 93 Nicholls, 2005; Sánchez-Bayo & Green, 2018; Wahren et al, 2013). The Australian alpine 94 bioregion is further threatened by fire, sub-alpine vegetation encroachment and impacts of 95 invasive species (Hoffmann et al, 2019). Such threatening processes have been linked to 96 alterations in the survival rates, distributions and population dynamics of endemic alpine 97 species (Green, 2010; Nicholls, 2005). For invertebrates, overwintering survival rates under 98 reduced snow cover may be decreased because snow acts as a buffer from fluctuating 99 temperatures and insulates eggs during cold winter months (Bale & Hayward, 2010). Despite 100 the potential consequences of climate change to alpine species, studies of these assemblages 101 are few in the Australian Alps (Hoffmann et al, 2019), especially for invertebrates, in spite of 102 their value in assessing ecological responses to shifting thermal regimes (Hassall, 2015; 103 Khamis et al, 2014; Yadav et al, 2019). 104 105 Here we examine the effect of temperature-elevation gradients on Kosciuscola grasshoppers 106 in terms of their occurrence, relative abundance and body size. We focus on three of five 107 species of the genus: K. usitatus, K. tristis, and K. cognatus (Orthoptera: Acrididae), which 108 all co-occur, are flightless, and endemic to the Australian Alps. Our three focal species are 109 common throughout the Kosciuszko alpine region ranging from montane woodlands to alpine 110 areas (Slatyer et al, 2016). Field observations suggests that the species may differ in 111 elevational range, with K. cognatus occupying the broadest range (Tatarnic et al, 2013) and 112 K. tristis having the narrowest range of the five species of Kosciuscola. (Slatyer et al, 2014). 113 Further observations similarly indicate that K. cognatus occupies low to middle elevation 114 areas (900-1700m), K. tristis middle to high elevations (1500-2000m) and K. usitatus (1400- 115 2200m) from middle to the highest of elevations (Campbell & Dearn, 1980). Moreover, 116 previous work has found that these

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