La escuela como institución total Los talleres como control

Introduction

Atmospheric levels of carbon dioxide now exceed 400 parts per million (ppm), increasing global oceanic and land surface temperatures by 0.85°C on average in the last 120 years (Intergovernmental Panel on Climate Change (IPCC) 2014, National Oceanic Atmospheric Administration (NOAA) 2017). Concentrations of greenhouse gases are projected to raise global temperatures further, from 1°C to 3.7°C, depending on Representative Concentration Pathway (RCP) trajectories (IPCC 2014) (Table 4.1). Such temperature increases are having, and will have, profound impacts on biodiversity, especially on species that have narrow temperature requirements (Bulgarella et al. 2014, Chen et al. 2011, Hickling et al. 2006, Levinsky et al. 2007, Moritz et al. 2008, Parmesan 2006, Rodríguez-Trelles & Rodríguez 1998, Root et al. 2003, Thomas et al. 2004). Changes in species distributions as a result of anthropogenic climate change are of ecological, conservation and economic interest (Bellard et al. 2016, Buerki et al. 2015,Buczkowski & Bertelsmeier 2017, Fletcher et al. 2016, Gama et al. 2015, Ihlow et al. 2016, Lazo et al. 2016, Lei et al. 2017, Martins et al. 2016, Molloy et al. 2017, Schinhen et al. 2014, Yan et al. 2017).

Defining an organisms niche

An organism’s ecological niche is considered to be all the “conditions” that allow it to exist in a set space and time; all the abiotic and biotic factors that allow a species to maintain its population growth at or above zero, and therefore exist (Elton 1927,

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Table 4.1 The four Representative Concentration Pathway (RCP) trajectories proposed by the Intergovernmental Panel on Climate Change Fifth Assessment Report. Trajectories are based on four greenhouse gas concentration scenarios, which are estimated on whether emissions are reduced or not, and when they will be reduced, before the year 2090 (2081 – 2100).

Climate Change Scenario

Mean Temperature Increase (°C)

Temperature Increase Range (°C)

RCP2.6 1.0 0.3 – 1.7

RCP4.5 1.8 1.1 – 2.6

RCP6.0 2.2 1.4 – 3.1

145 Grinnell 1924). Also known as its Realised Ecological Niche, an organism’s niche is the outcome of its Realised Environmental Space, Fundamental Niche Space and Potential Niche Space interacting (Jackson & Overpeck 2000). A Realised Environmental Space consists of all the environmental conditions that are occurring in an organism’s surroundings at a set time, and Fundamental Niche Space encompasses the specific environmental zone within which an organism can maintain a stable population size (e.g. appropriate climatic conditions); where these two variables overlap they create an organisms Potential Niche Space (Figure 4.1) (Grinnell 1917, Jackson & Overpeck 2000). This Potential Niche Space becomes further limited to an organism’s Realised Ecological Niche when biotic interactions with other organisms are considered (e.g. predation, competition, disease, parasitism, mutualism) (Figure 4.1) (Elton 1927, Grinnell 1924, Jackson & Overpeck 2000).

General climatic changes will alter available Realised Environmental Space, and evolutionary processes will alter an organism’s Fundamental, and therefore, Potential Niche Space; changes in biotic variables (e.g. arrival of invasive species) will result in further changes to its Realised Ecological Niche (Jackson & Overpeck, 2000). Organisms will continually be under pressure from inter- and intra-specific competition, and will need to adjust their niches to stay viable (Gause 1932, Jackson & Overpeck 2000, Van Valen 1973). With anthropogenic climate change, selection pressure is likely to change more rapidly, threatening populations, species and ecosystems.

Ecological Niche Models

Ecological Niche Models (ENMs), also known as species distribution models, are a useful tool for predicting the potential niche space that species can occupy (Pearson & Dawson 2003, Phillips & Dudik 2008, Thuiller 2003). There has been an increase in the modelling of species distributions with the availability of modelling software (GARP, MaxEnt, ModEco) and R packages (biomod2, dismo, sdm); while the more recent introduction of ensemble models has improved their predictive accuracy (Anderson et al. 2003, Hijmans & Elith 2013, Naimi & Araújo 2016, Phillips et al. 2005, Sivyer et al.2018, Thuiller 2003, Thuiller et al. 2009, 2016). Ecological Niche Models use the known distribution of a species to determine what environmental

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Potential Niche Space

Realised Ecological Niche

Fundamental Niche Space Realised Environmental Space

Environmental Variable X E n v ir o n men tal V ar iable Y

Figure 4.1 A 2-dimensional diagram demonstrating how a species realised environmental space and fundamental niche space interact to form a species potential niche space; this is further restricted to a species realised ecological niche space once biotic interactions are considered(modified from Jackson & Overpeck 2000).

147 variables are key to limiting the distribution of that species. The Potential Niche Space of a species models the current suitable environmental conditions for a species, based on its occurrence data. This information is used to hindcast or forecast the potential distribution of species, demonstrating where these same suitable conditions may have occurred in the past, or will occur in the future (Anderson et al. 2003). Available environmental data usually comprises of climate variables and landuse information. To hindcast or forecast potential species distributions, predictions of these variables from the past or for the future are required, and can be acquired from online databases that have inferred climate based on models (e.g. Worldclim – Global Climate Data) (Hijmans et al. 2005).

A species’ ecological niche is complex, and ENMs by no means encompass all of the dimensions that go in to the formation of a species niche (Davis et al. 1998,Pearson et al. 2006). However, ENMs are informative and are a step towards understanding how a species may be interacting with its abiotic and biotic environment (Anderson et al. 2003, Pearson et al. 2006). Ecological Niche Models are primarily used to aid in the management of endangered and invasive species, as ENMs can highlight where suitable habitat is and where it is most likely to decrease or increase in light of future climate or landuse change scenarios (Bellard et al. 2016, Buerki et al. 2015, Buczkowski & Bertelsmeier 2017, Duque-Lazo et al. 2016, Fletcher et al. 2016, Gama et al. 2015, Ihlow et al. 2016, Lei et al. 2017, Martins et al. 2016, Molloy et al. 2017,van Schingen et al. 2014, Yan et al. 2017). Less commonly, is the use of ENMs to aid in species delimitation, alongside genetic and morphological evidence (Leaché et al. 2009, Raxworthy et al. 2007, Rissler & Apodaca 2007). Once niches are established and changes predicted, appropriate management solutions such as implementing or increasing protection of a species and particular habitats, or increasing pest management, can be applied (Bellard et al. 2016, Buerki et al. 2015, Buczkowski & Bertelsmeier 2017, Duque-Lazo et al. 2016, Fletcher et al. 2016, Gama et al. 2015, Ihlow et al. 2016, Lei et al. 2017, Martins et al. 2016, Molloy et al. 2017,van Schingen et al. 2014, Yan et al. 2017).

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Climate change in New Zealand

It is predicted that average temperatures in New Zealand will increase by 0.7°C (RCP2.6) to 3.0°C (RCP8.5) by 2090 (relative to 1986-2005 temperatures) (Ministry for the Environment, 2016). Precipitation is predicted to reduce in the north and east of the North Island and increase in most other areas, particularly the West Coast of the South Island, where it could increase by up to 40% (Ministry for the Environment, 2016). Droughts are predicted to increase in severity and intensity, particularly in the north and east of the North Island, and around the main divide of the South Island (Ministry for the Environment, 2016). Additionally, mean sea level pressure and daily extreme wind speeds are also predicted to increase in most parts of New Zealand, whilst humidity is predicted to decrease – except along the West Coast of the South Island. In high elevation areas of the South Island, snow days are predicted to decrease by 30 days by 2090 (RCP8.5) (Ministry for the Environment, 2016). These findings were simulated based on RCP trajectories established by the Intergovernmental Panel on Climate Change (IPCC) fifth Assessment Report (IPCC 2014). Representative Concentration Pathways reflect the projected outcomes of four different greenhouse gas concentration scenarios: RCP2.6 assumes a decline in greenhouse gas emissions following a peak in 2020; RCP4.5 assumes a decline in greenhouse gas emissions following a peak in 2040; RCP6.0 assumes a decline in greenhouse gas emissions following a peak in 2080; and RCP8.5 assumes an uninhibited increase in greenhouse gas emissions throughout the 21st century (Table 4.1) (IPCC 2014). Representative Concentration Pathway 2.6 and RCP8.5 are used in this study to investigate the two most extreme scenarios for which future climate change may impact alpine grasshoppers in New Zealand.

Alpine grasshoppers as representatives of alpine fauna

New Zealand is inhabited by a diverse fauna of endemic Acrididae (Bigelow 1967). Of 13 species, 10 are predominantly found in alpine environments, where they inhabit tussock, herb and scree habitats (Bigelow 1967). Some of these grasshopper species are found only inhabiting the alpine zone (e.g. Alpinacris crassicauda and Sigaus villosus), others have ranges that extend from the alpine zone to below the treeline (e.g. Paprides nitidus and Sigaus australis), and there are also members that are only found inhabiting lowland grasslands (e.g. Sigaus childi and Sigaus minutus). With future climate change, New Zealand’s alpine zone is predicted to be reduced by ~50%, and is estimated to lose

149 33-50% of its indigenous alpine flora species with 3°C of warming (Halloy & Mark 2003); it is not known how New Zealand’s alpine fauna will be affected. By modelling New Zealand’s endemic alpine grasshopper diversity and the niches they inhabit, we may be able to better understand how New Zealand’s alpine fauna will respond to future climate change.

Aims

What limits the current distribution of New Zealand’s endemic alpine grasshoppers? If the factors controlling their distribution are mostly captured by abiotic factors then species distributions are expected to closely match their environmental envelope (e.g. their Realised Niche Space will match their Potential Niche Space) and the effects of climate change on species ranges should be predictable (if no adaptation). However, if biotic interactions are important factors controlling distribution, then species distributions may poorly correlate with their predicted environmental envelope and it will be more difficult to predict the effect of climate change on their future distributions. Here I use current species distributions and Ecological Niche Modelling tools to infer past (i.e. LGM), current and future (i.e. RCP2.6 and RCP8.5) distributions of New Zealand’s endemic alpine grasshoppers. In order to predict how climate has, and will, impact their distributions, this comprehensive study will explore niche models at two taxonomic levels, including examination of the diverging mitochondrial lineages of Brachaspis nivalis and Sigaus piliferus. Knowing how these alpine grasshoppers may respond to future climate scenarios will be valuable knowledge in the conservation management of alpine habitats in New Zealand. Interpretation of future effects will draw upon inference from past change. Specifically, it is expected that climate warming since the Last Glacial Maximum (LGM) is likely to have reduced the habitat available to these alpine grasshoppers. This is predicated upon the assumption that occupiable area reduces with elevation.

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Materials and Methods