Pollination Ecology and Pollination Evolutionary Processes with Relevance in Ecosystem Restoration – Pollination Biology of Diuris: Testing for Batesian Mimicry in Southwestern Australia

Mimicry is based on the interaction between a mimic, a model and a receiver. While there is increasing recognition of Batesian floral mimicry in plants, there are few confirmed cases where mimicry involves more than one model species. The Australian orchid genus Diuris has been long hypothesised to engage in guild mimicry of a range of co-occurring pea plants (Faboideae). Some clades of Diuris are superficially similar in both colour and shape to those of a guild of yellow and brown pea plants (Faboideae). Here, we test for pollination via mimicry of pea plants in Diuris (Orchidaceae). Additionally, we test for further ecological interactions (non-model plants, pollination limitation, habitat size and plant frequency) in order to assess the reproductive success of the orchids. For addressing these hypothesis we select two study species, occurring in different habitat: Diuris brumalis (Jarrah forest) and Diuris magnifica (Banksia woodland), the latter occurring in fragmented habitat. We test for floral mimicry criteria in both of the species. In order to frame the pollination ecology of the putative model plants, we verify the type of pollinator interactions (generalised vs specialized) occurring in four communities of pea plants in the southwestern Australian Floristic Region (SWAFR). D. brumalis, D. magnifica and the pea plants showed strong flower similarity and were likely to be perceived as the same by pollinators, native bees (Trichocolletes; Colletidae). However, in D. brumalis the orchid reproductive success increased with the local abundance of the model species (Daviesia spp.), while in D. magnifica the reproductive success wasn’t in relation to the putative models. Alternatively, D. magnifica reproductive success was influenced by a non-model pea plant (Hardenbergia) which is locally abundant and widespread in all the study sites. Additionally, habitat size and orchid plant frequency influenced the orchid reproductive success. Pea plant species were visited by between one and four genera of native bees, indicating variation in levels of specialisation of the pollination systems of Faboideae. Several pea plant species showed specialised interactions with bee genera attracted. Unexpectedly, some pea plant species frequently attracted beetles that may play an important role in pollination. Evidence for mimicry of multiple models suggests that D. brumalis and D. magnifica may be engaged in guild mimicry system. Interestingly, D. brumalis and D. magnifica belongs to a complex of species with similar floral traits, suggesting that this represents a useful system for investigating speciation in lineages that employ mimicry of food plants. Furthermore, the study on pollination of Faboideae species of SWAFR, offers a pivotal research for next investigations on pollinator webs and syndromes of Australian pea plants scarcely documented until now

A simple and effective ground-based tool for sampling tree flowers at height for subsequent nectar extraction

Abstract Sampling nectar from forest canopies is logistically challenging as it requires physical access to the canopy to a height greater than that can be achieved by hand. The most common solutions comprise the use of cherry pickers, cranes or tree climbers. These techniques are generally expensive, logistically complex, and often involve additional safety risks and specialized technicians to use the equipment/machinery. In addition, access is required up to the tree for cherry pickers and cranes, and tree climbers are often unable to reach the outermost branches. Here, we propose a simple approach based on a special, easy to assemble tool, to sample tree flowers for subsequent nectar extraction, to avoid climbing and cumbersome/expensive equipment. Conducting a study on nectar production of Eucalypt trees (Myrtaceae) in southwest Australia, we conceived a practical ground‐based tool formed by an extendible pole with an adapted container at the end for covering the tree inflorescence with organza and plastic (polyethylene) bags. We experimented with the tool on dozens of trees of each of the co‐occurring species Eucalyptus marginata and Corymbia calophylla, successfully completing the following operational manoeuvres: bagging the inflorescence with an organza bag prior to the nectar collection, then bagging the inflorescence and organza bags with plastic bags if necessary, and cutting the bagged inflorescences from the branch for subsequent nectar extraction. We present the instructions for assembling the tool and we detail the sequence for bagging and sampling flowers from canopy trees, including time‐saving tips. This approach allows efficient sampling of tree flowers for subsequent nectar extraction. To effectively handle the tool while covering the inflorescence, the maximum sample collection height is approximately 10 m. Overall, the tool helps to address limitations related to sampling nectar from medium‐height trees such as costs, risks and time factors. Beyond tree flowers, the tool can be used for sampling flowers of epiphytic and climbing plants, and it could also be used to test for autogamy in flowering trees

Soil, site, and management factors affecting cadmium concentration in cacao-growing soils

Soil contamination by potentially toxic trace elements (PTEs) such as Cadmium (Cd), is a major environmental concern because of its potential implications to human health. Cacao-based products have been identified as food sources with relatively high Cd contents. Here, we assessed Cd concentrations of cacao-growing soils in four major agricultural regions with contrasting climates in Peru, one of the main exporters of cacao products worldwide. At each study site (n = 40) a broad range of potential factors affecting Cd concentration in soils, i.e., site, soil and management, were evaluated. Concentrations of Cd ranged between 1.1-3.2 mg kg-1. Mean values per region were below 2.7 mg kg-1, usually established as upper-limit for non-polluted soils. Cadmium concentrations were significantly (p < 0.001) higher in sites at higher elevations and in a temperate, drier climate. Cadmium correlated positively with pH (r = 0.57; p < 0.05) and was higher (p < 0.001) in alluvial sediments and Leptosols. Management factors (cacao variety, cultivation year, management practices) and agroecology did not affect Cd concentrations directly. Overall, this study highlights the importance of considering a broad range of both natural and anthropogenic factors to evaluate Cd concentrations in cacao-growing soils and contribute to effective and sustainable cacao production by improving land management and plannin

Rotating Arrays of Orchid Flowers: A Simple and Effective Method for Studying Pollination in Food Deceptive Plants

Floral deception has been observed in several genera in angiosperms, but is most common in the Orchidaceae. Pollination mechanisms in food deceptive plants are often difficult to assess, as visitation frequency by insects requires numerous hours of field observations to ascertain. Here, for the first time, we describe in detail and validate a simple and effective method that extends previous approaches to increase the effectiveness of pollination studies of food deceptive orchids. We used an orchid of southwest Australia, Diuris brumalis (Orchidaceae), that visually mimics model plants belonging to the genus Daviesia (Faboideae). Arrays of orchid flowers were placed and moved systematically in proximity to model plants, resulting in rapid attraction of the pollinators of D. brumalis. We compared pollinaria removal (as an indicator of pollination success) in naturally growing orchids with pollinaria removal in arrays of orchid flowers in the same sites. We showed that the proposed method greatly enhances pollinator attractiveness in food deceptive systems with very low pollination rates, and we compared its efficiency with other similar methods. The approach can be used for observing pollinator behavioural patterns and confirming effective pollinators for food deceptive species with low insect visitation rates

Pollination Ecology and Pollination Evolutionary Processes with Relevance in Ecosystem Restoration – Pollination Biology of Diuris: Testing for Batesian Mimicry in Southwestern Australia

The thesis demonstrates a unique pollination system in the Australian orchid genus Diuris via floral mimicry of multiple pea plants (Faboideae). In order to frame the pollination ecology of the putative model pea plants, we also verify the type of pollinator interactions (generalised vs specialized), occurring in communities of pea plants in the southwestern Australian Floristic Region (SWAFR). Our findings support one of the rare confirmed case of guild mimicry in plant world

Ecological factors driving pollination success in an orchid that mimics a range of Fabaceae

Rewarding plants can enhance the pollination success of co-occurring plants pollinated by food mimicry. However, it is not always possible to readily discern between the effect of model and magnet species. Here, we tested for mimicry of co-occurring Fabaceae by the rewardless Diuris magnifica (Orchidaceae) and whether the number of flowers of Fabaceae, habitat remnant size and frequency of conspecifics, influenced the pollination success of D. magnifica. Trichocolletes bees were the primary pollinators of D. magnifica, on which they displayed similar behaviour as seen when feeding on Fabaceae. Quantification of spectral reflectance suggested that flowers of Bossiaea eriocarpa, Daviesia divaricata and Jacksonia sternbergiana may represent models for D. magnifica, whereas Hardenbergia comptoniana strongly differed in colour. Orchid pollination success was not directly affected by the number of model flowers, but the pollination rate was enhanced by increased numbers of Hardenbergia flowers. Pollination success of the orchid decreased with higher density of conspecifics, but did not exhibit a significant relationship with Trichocolletes occurrence, possibly because of the contribution of sub-optimal pollinator species. Fruit set of the orchid was greater in larger habitat remnants. Overall, pollination success of D. magnifica is affected by ecological factors related to the effectiveness of mimicry, numbers of co-flowering plants and anthropogenic landscape alteration

Pronounced differences in visitation by potential pollinators to co-occurring species of Fabaceae in the Southwest Australian biodiversity hotspot

Despite their diversity and the potential for specialized pollination systems, Australian Fabaceae have received little attention in pollination studies. In the Southwest Australian Floristic Region (SWAFR), a recognized biodiversity hotspot, co-occurring and abundant species of Faboideae exhibit a range of floral colours and forms, suggestive of adaptation to different groups of pollinators. For four communities of Fabaceae in the SWAFR we investigated whether co-occurring species overlap in pollinator genera, whether these pollinators show differences in behaviour on the pea flower and whether variations in stamen length and nectar composition among species are associated with different pollinator types. Species of Fabaceae were visited by one to four genera of native bees, suggesting varying levels of ecological specialisation. In Fabaceae with more specialized interactions, co-occurring species showed marked differences in the bee genera attracted. Unexpectedly, some Fabaceae frequently attracted beetles, which may play an important role in their pollination. There was no evidence for an association between stamen length or nectar composition and the type of pollinator. The introduced honeybee, visited all studied species of Fabaceae, suggesting that they may act both as a pollinator and a potential competitor with native pollinators

A simple and effective ground-based tool for sampling tree flowers at height for subsequent nectar extraction

© 2020 British Ecological Society. Sampling nectar from forest canopies is logistically challenging to sample as it requires physical access to the canopy to a height greater than that can be achieved by hand. The most common solutions comprise the use of cherry pickers, cranes or tree climbers. These techniques are generally expensive, logistically complex, and often involve additional safety risks and specialized technicians to use the equipment/machinery. In addition, access is required up to the tree for cherry pickers and cranes, and tree climbers are often unable to reach the outermost branches. Here, we propose a simple approach based on a special, easy to assemble tool, to sample tree flowers for subsequent nectar extraction, to avoid climbing and cumbersome/expensive equipment. Conducting a study on nectar production of Eucalypt trees (Myrtaceae) in southwest Australia, we conceived a practical ground-based tool formed by an extendible pole with an adapted container at the end for covering the tree inflorescence with organza and plastic (polyethylene) bags. We experimented with the tool on dozens of trees of each of the co-occurring species Eucalyptus marginata and Corymbia calophylla, successfully completing the following operational manoeuvres: bagging the inflorescence with an organza bag prior to the nectar collection, then bagging the inflorescence and organza bags with plastic bags if necessary, and cutting the bagged inflorescences from the branch for subsequent nectar extraction. We present the instructions for assembling the tool and we detail the sequence for bagging and sampling flowers from canopy trees, including time-saving tips. This approach allows efficient sampling of tree flowers for subsequent nectar extraction. To effectively handle the tool while covering the inflorescence, the maximum sample collection height is approximately 10 m. Overall, the tool helps to address limitations related to sampling nectar from medium-height trees such as costs, risks and time factors. Beyond tree flowers, the tool can be used for sampling flowers of epiphytic and climbing plants, and it could also be used to test for autogamy in flowering trees

Masquerading as pea plants: behavioural and morphological evidence for mimicry of multiple models in an Australian orchid

Background and Aims: While there is increasing recognition of Batesian floral mimicry in plants, there are few confirmed cases where mimicry involves more than one model species. Here, we test for pollination by mimicry in Diuris (Orchidaceae), a genus hypothesized to attract pollinators via mimicry of a range of co-occurring pea plants (Faboideae). Methods: Observations of pollinator behaviour were made for Diuris brumalis using arrays of orchid flowers. An analysis of floral traits in the co-flowering community and spectral reflectance measurements were undertaken to test if Di. brumalis and the pea plants showed strong similarity and were likely to be perceived as the same by bees. Pollen removal and fruit-set were recorded at 18 sites over two years to test if fitness of Di. brumalis increased with the abundance of the model species. Key Results: Diuris brumalis shares the pollinator species Trichococolletes capillosus and T. leucogenys (Hymenoptera: Colletidae) with co-flowering Faboideae from the genus Daviesia. On Di. brumalis, Trichocolletes exhibited the same stereotyped food-foraging and mate-patrolling behaviour that they exhibit on Daviesia. Diuris and pea plants showed strong morphological similarity compared to the co-flowering plant community, while the spectral reflectance of Diuris was similar to that of Daviesia spp. Fruit-set and pollen removal of Di. brumalis was highest at sites with a greater number of Daviesia flowers. Conclusions: Diuris brumalis is pollinated by mimicry of co-occurring congeneric Faboideae species. Evidence for mimicry of multiple models, all of which share pollinator species, suggests that this may represent a guild mimicry system. Interestingly, Di. brumalis belongs to a complex of species with similar floral traits, suggesting that this represents a useful system for investigating speciation in lineages that employ mimicry of food plants

Soil, Site, and Management Factors Affecting Cadmium Concentrations in Cacao-Growing Soils

Soil contamination by potentially toxic trace elements (PTEs) such as Cadmium (Cd), is a major environmental concern because of its potential implications to human health. Cacao-based products have been identified as food sources with relatively high Cd contents. Here, we assessed Cd concentrations of cacao-growing soils in four major agricultural regions with contrasting climates in Peru, one of the main exporters of cacao products worldwide. At each study site (n = 40) a broad range of potential factors affecting Cd concentration in soils, i.e., site, soil and management, were evaluated. Concentrations of Cd ranged between 1.1–3.2 mg kg−1. Mean values per region were below 2.7 mg kg−1, usually established as upper-limit for non-polluted soils. Cadmium concentrations were significantly (p < 0.001) higher in sites at higher elevations and in a temperate, drier climate. Cadmium correlated positively with pH (r = 0.57; p < 0.05) and was higher (p < 0.001) in alluvial sediments and Leptosols. Management factors (cacao variety, cultivation year, management practices) and agroecology did not affect Cd concentrations directly. Overall, this study highlights the importance of considering a broad range of both natural and anthropogenic factors to evaluate Cd concentrations in cacao-growing soils and contribute to effective and sustainable cacao production by improving land management and planning