Prueba de Hipótesis Tabla 17: Índice de correlación

Such realities are not synonymous to the desired „clean, green‟ reputation mentioned earlier which the wine industry aspires to maintain. In light of this, mitigation of past habitat loss by current land owners through restoration of native vegetation may be seen as a means by which vineyard operations can attain a reputation for environmental sensitivity; satisfying the

„green‟ demands of their consumers. Such action is already evident. Banrock Station, a well known Australian wine label, informs consumers that it directs part of its profits into the protection and restoration of wetlands in the region where the wine is purchased

(www.banrockstation.com). Another wine maker, Grove Mill of Marlborough, undertakes similar restoration initiatives and markets this upon their wine bottles with a stated philosophy to produce “premium quality wines with minimal environmental impact”

(www.grovemill.co.nz).

As the various ecosystem services provided by native New Zealand plants is better understood a grasp of their value to the wine industry beyond marketing may be attained. If native plants deployed within vineyards contribute to aspects of vineyard sustainability, such as improved soil health or a reduced need for synthetic herbicide or pesticide applications then their

percieved value to the wine industry will grow. The value of native plants to the New Zealand wine industry therefore arises through their provision of ecosystem services relevent to the wine industry.

1.6 Aims and objectives of the thesis

The conception of this thesis began with a thought to investigate whether any native New Zealand plants might be utilised for conservation biological control within vineyards in a similar fashion to the currently deployed non-native flowering plants (buckwheat (Fagopyrum

esculentum Moench (Polygonaceae)) and alyssum (Lobularia maritima L. Desv.

(Brassicaceae)). Collaborations with colleagues at Michigan State University who were undertaking similar research and the development of the Greening Waipara project motivated the thesis to include an investigation of other ecosystem services that native New Zealand plants might provide within agricultural landscapes. However the focus remained within the vineyard environment. These investigations took the form of both laboratory and field experiments and also included surveys of both vineyard managers and winery visitors. The following section provides an overall description and explains the rationale for the content of thesis chapters 2 to 8. The over-arching aim of the thesis was to gain a better understanding of the ecosystem services that native New Zealand plants may provide within our agricultural landscapes by testing a series of hypothetical or anticipated benefits.

1.6.2 Chapter descriptions and their objectives

Chapter 2: Investigating a potential tool for screening native floral resources for CBC.

During the short-listing of native plants suitable for CBC a potential tool for selecting species arose through discussions with UK colleagues. A theory that plants displaying a sucrose dominant nectar ratio (sucrose/(fructose+glucose) were more suitable for hymenopterans had been suggested in early literature (Baker & Baker, 1983) while more recent work had

proposed this may be a factor by which floral resources for CBC could be short-listed (Vattala et al., 2006). If this theory holds for parasitoids important for pest control, and if native New Zealand plants displayed differing sugar ratios, then this characteristic could be useful in identifying suitable plant species for CBC where parasitoid fitness was of interest. This chapter investigates the importance of the nectar sugar ratio to the longevity of two

hymenopteran species known for their pest control services within New Zealand‟s agricultural landscapes; Diadegma semiclausum Hellen (Hymenoptera: Ichneumonidae) which attacks brassica (Brassica spp.) pests and Dolichogenidea tasmanica Cameron (Hymenoptera:

Braconidae) the primary parasitic wasp attacking a vineyard pest. The nectar sugar ratios of several native plant species was determined to confirm that this could be a differentiating characteristic by which to select floral resources for CBC.

Key objective: To improve our ability to select native New Zealand plants suitable for CBC Ecosystem service targeted: Biological control of pests

Chapter 3: Screening native floral resources for conservation biological control

Through laboratory bioassays this chapter investigated the effects of the floral resources of eight commonly planted native shrub species upon the longevity of several beneficial and pest invertebrate species. Beneficial invertebrates included the omnivorous lacewing: Micromus

tasmaniae Walker (Neuroptera, Hemerobiidae), and two parasitic wasps: D. semiclausum and Aphidius ervi Haliday (Hymenoptera: Aphidiidae). Pest invertebrates included two

lepidopteran species; the light brown apple moth: Epiphyas postvittana Walker (Tortricidae) and the diamond back moth: Plutella xylostella L. (Hyponomeutidae). Identifying floral resources native to this country which can also enhance natural enemy fitness would contribute to an understanding of their value within the agricultural landscape.

Key objective: To assess the potential of several commonly planted native New Zealand flowering plants for CBC

Ecosystem service targeted: Biological control of pests

Chapter 4: Deploying native plants beneath grapevines for ecosystem service enhancement in a North Canterbury vineyard

This chapter utilised both laboratory bioassays and a field trial to assess the potential of native ground covering plants (established upon the vineyard floor) to provide various ecosystem services.

Laboratory work investigated the potential for the native floral resources to be utilised by invertebrates which contribute to vineyard pest control and also assessed the risk that those same resources may be used by vineyard pests. The field trial assessed selected native plant species for their potential to provide the ecosystem services: biodiversity conservation,

field trial also provided an understanding of the practicalities involved in incorporating native vegetation within the cropping system and the likelihood of this practice being adopted by growers.

Key objective: To gain a better understanding of the value of native ground covering plants within the vineyard environment.

Ecosystem service targeted: Biodiversity conservation, biological control of pests, weed suppression, greenhouse gas sequestration & soil health.

Chapter 5: The value of remnant vegetation to agriculture within the Waipara valley This chapter investigated the contribution of small pockets of remnant vegetation to pest control services within the Waipara valley. Field and laboratory researches were undertaken to assess the use of floral resources within remnant habitats by beneficial and pest

invertebrate. The dominant native shrub species within the remnants was the insect pollinated

Discaria toumatou Raoul (Rhamnaceae), consequently it was this species which work centred

upon.

Key objective: To gain a better understanding of the value remnants of native vegetation have within agricultural landscapes

Ecosystem service targeted: Biological control of pests

Chapter 6: Vineyard biodiversity trails: realising the marketing value of native plants to New Zealand wineries

Marketing is critically important to the wine industry of New Zealand. As mentioned in section 1.4.2 New Zealand wine growers are under increasing pressure from both

international and domestic consumers to incorporate sustainable practices into their wine making procedures. The promotion then of their establishment of native plants into their vineyard properties for the purpose of enhancing ecosystem services presents valuable marketing opportunities. This value of native plants was investigated through face-to-face questionnaires with winery customers who had walked a native plant „biodiversity trail‟. Key objective: To better understand the marketing value of native plants to New Zealand wineries.

Chapter 7: The Greening Waipara project: the practicalities of incorporating native plants into agricultural landscapes

This chapter reviewed the Greening Waipara project which sought to re-establish native New Zealand plants within the North Canterbury landscape and increase grower adoption of sustainable agricultural practices- specifically those involving native plants. The review focussed on the practicalities of incorporating native New Zealand plants into the agricultural landscapes of this country and some guidelines for maximising success.

Key objective: To gain a better understanding of the practicalities of incorporating native plants into agricultural landscapes

Chapter 8: Concluding discussion

The final chapter synthesises the major findings from this thesis and evaluates the extent to which key objectives were met. The likelihood of the practices developed within this thesis being adopted by agriculturalists is discussed and suggestions for further extension of the research are made.

Chapter 2

Investigating a potential tool for screening native floral

resources for conservation biological control

Adapted from:

Tompkins, J-M. L., Wratten, S. D., & Wäckers, F. L, 2010. Nectar to improve parasitoid fitness in biological control; does the sucrose: hexose ratio matter? Basic and Applied Ecology (11) pp. 264-271

2.1 Abstract

During the short-listing of native plants suitable for conservation biological control (CBC) a potential tool for selecting species arose through discussions and assessing the literature. A theory that plants with a sucrose dominant nectar ratio (sucrose/(fructose+glucose) were more suitable for parasitoids had been suggested in early literature (Baker & Baker, 1983) while more recent work had indicated this may be a factor by which floral resources for CBC could be short-listed (Vattala et al., 2006). If this theory holds for parasitoids important for pest control, and if native New Zealand plants displayed differing sugar ratios, then this

characteristic could be useful in identifying suitable plant species for CBC where parasitoid fitness was of interest.

This chapter investigates the importance of the nectar sugar ratio for the longevity of two parasitoid species known for their biocontrol services within New Zealand‟s agricultural landscapes; Diadegma semiclausum Hellén (Hymenoptera: Ichneumonidae) which attacks brassica (Brasica spp.) pests and Dolichogenidea tasmanica Cameron (Hymenoptera: Braconidae) the primary parasitoid attacking a key vineyard pest, Epiphyas postvittana (Lepidoptera: Tortricidae). The nectar sugar ratios of several native plant species were

determined to confirm whether this could be a differentiating characteristic by which to select floral resources for CBC. Analysis of floral nectar from fourteen plant species confirmed that the sucrose/hexose ratio significantly differed between species. The hymenopteran parasitoids

D. semiclausum and D. tasmanica were fed 40% w/w sugar solutions, differing in their sugar

ratios. Solutions were classified as either sucrose dominant (ratio >0.99), sucrose rich (ratio 0.5-0.99), hexose rich (ratio 0.1-0.499) or hexose dominant (ratio <0.1). The control treatment was water only. No significant differences in parasitoid longevity were found between the sugar treatments for either species but all had higher longevity compared to the water treatment. This suggests there is not an optimal sucrose/hexose ratio for parasitoid wasps,

although a greater number of parasitoid species should ideally be tested to confirm if this is true for the wider parasitoid taxonomic groups.

Consequently, nectar sugar ratios were not utilized within this study as a tool to short-list native plant species suitable for CBC. Rather the laboratory and field experiments outlined in Chapters 3 and 4 provided information with which to short-list suitable native plant species.

2.2 Introduction

Providing flowering plants within or around a crop is a practice increasingly adopted by agriculturalists to benefit natural enemies of arthropods and thus to enhance pest management. This form of conservation biological control is undertaken to provide the natural enemies with food such as nectar and pollen, alternative prey or hosts as well as shelter (Jonsson et al., 2008; Landis et al., 2000; Zehnder et al., 2007). Most adult parasitoids feed on sugar sources, using saccharides as an energy source (Heimpel & Jervis, 2005; Jervis & Kidd, 1986) and such feeding may be critical to enhancing biological pest control (Jonsson et al., 2008; Wäckers et al., 2005).

Currently, only seven annual flowering plant species are common in the literature as nectar resources for parasitoid wasps. These plants have had some success in improving biological control, ranging from improving parasitoid fitness in the laboratory to reducing pest

populations in the field. They are, however, often deployed outside their native range.

Considering that there are more than 200, 000 other flowering plant species on Earth, there is large scope for utilizing other species with the potential to enhance parasitoid fitness. This would include species that are native to the agricultural landscape in which they are to be deployed. Identifying such plants would not only give growers a wider selection of plants to utilize, but would also provide conservation and other ecosystem service values (Fiedler et al., 2008; Fiedler & Landis 2007a). Understanding more about which plant characteristics are vital in determining nutritional suitability of floral resources would aid in the identification of potential flowering species and reduce the need for routine, repetitive and time-consuming bioassays. An important consideration when assessing floral resource suitability is its nectar quality.

Floral nectar predominantly comprises the sugars fructose, glucose and sucrose. It is these principal nectar components which have been shown to have the greatest positive effect upon

parasitoid longevity (Wackers, 2001). This may be due to the fact that these sugars are more readily converted to energy by parasitoids (Hausmann et al., 2005).

Concerning concentration, Wäckers (1999) demonstrated that the feeding response of the parasitoid Cotesia glomerata Linn. (Hymenoptera: Braconidae) to a range of sugars was positively correlated to their nutritional suitability. Azzouz et al. (2004) found that Aphidius

ervi (Haliday) (Hymenoptera: Braconidae) longevity rose with increasing sugar

concentrations at a 1:1 fructose:glucose solution up to 70% (w/v). Although longevity may be unaffected when equal concentrations of sucrose or glucose and fructose are provided

(Hogervorst et al., 2007), it has been postulated that the relative amounts of these primary sugars may be of importance to insect fitness (Baker & Baker, 1983; Vattala et al., 2006). Hymenoptera have been thought to prefer sucrose over hexose sugars (Cornelius et al., 1996; Fonta et al., 1985), which could be a reflection of a higher nutritional suitability of sucrose dominant nectar.

Although a plant‟s nectar composition can vary with age, condition, contamination and

various other abiotic and biotic factors (Azzouz et al., 2004; Burquez & Corbet, 1991; Koptur, 2005), robust testing by Baker & Baker (1983) showed that angiosperms could be assigned to a nectar sucrose: hexose-ratio. Based on this ratio nectar was categorized in four classes: sucrose-dominant (>0.99), sucrose-rich (0.5-0.99), hexose-rich (0.1-0.499) and hexose- dominant (<0.1). This sucrose/hexose ratio was found to be an important factor explaining insect-flower associations in different groups of flower visitors and the authors suggested that wasps would benefit most from a high sucrose/hexose ratio. However, little is known about whether the ratio of these dominant sugars within nectar actually affects parasitoid wasp fitness. It was postulated by Vattala et al. (2006) that parasitoids may „prefer‟ the sucrose- dominant nectar due to hexose-dominant nectars causing osmotic stress resulting in physiological constraints.

Here we analyze the nectars from selected native and non-native New Zealand plants to

determine their sugar ratio (S/ (F+G)) and whether these significantly differ from one another. Following this we test whether this sugar ratio affects parasitoid fitness and whether osmotic stress may be implicated as a factor limiting parasitoid longevity when feeding on highly concentrated sugar solutions.

2.3 Materials and methods

2.3.1 Measurement of plant nectar sugar ratio

Nectar was collected from fourteen different plant species including both native and non- native New Zealand plants between 9.00 and 12.00h. Native plant species were Parsonsia

heterophylla A. Cunn. (Apocynaceae), Pimelea prostrata J.R. Forst. et G. Forst.

(Thymeleaceae), Sophora microphylla Aiton (Fabaceae), Muehlenbeckia astonii Petrie (Polygonaceae), Linum monogynum G. Forst. (Linaceae), Discaria toumatou Raoul

(Rhamnaceae), Muehlenbeckia complexa A. Cunn. (Polygonaceae) and Lobelia angulata G. Forst. (Lobeliaceae). Non-native plant species were Phacelia tanacetifolia Benth

(Boraginaceae), Fagopyrum esculentum Moench (Polygonaceae), Lobularia maritima L. Desv. (Brassicaceae), Sonchus sp. (Asteraceae), Coriandrum sativum L. (Apiaceae) and

Sinapis alba L. (Brassicaceae). Plants were housed within a glasshouse at Lincoln University

and kept at temperatures between 14 and 25 °C. Each nectar sample was collected from an individual flower using a clean microcapillary tube and immediately transferred into a 0.6 ml Eppendorf tube that contained 70% ethanol to prevent enzyme activity (Vattala et al., 2006). Five samples were collected from each plant species, except for Sonchus spp. and Sophora

microphylla where three and four samples were taken respectively. HPLC analysis was then

undertaken to measure relative quantities of sucrose, glucose and fructose, following Steppuhn & Wäckers (2004).