Dr Louise Cranmer

Statement of research interests and experience

My main research interests are pollination biology, pollinator conservation and plant-pollinator interactions. I am particularly interested in pollinator behaviour and how this can affect plant reproductive success. My PhD investigated the relationship between pollinators and plants at the landscape scale. The mobility of pollinating animals is a key feature of their importance but we are largely ignorant of how landscape structure influences pollinator movements, though it is known to affect movements of non-pollinating invertebrates. My fieldwork involved observing the influences of landscape structure (both natural and artificially created) on insect movement. The results show that both hedgerows and artificial linear landscape features can influence the flight directions of bumblebees ( Bombus spp. Hymenoptera, Apidae), one of Europe's most important groups of pollinators. Bumblebees follow hedgerows around the landscape. A bioassay experiment in which Salvia pratensis (Lamiaceae) was planted into landscape patches with different numbers of connecting hedgerows showed that this directional response can have a profound effect on plant reproductive success – plants had increased pollinator activity, pollen receipt and subsequent seed set in patches with more connections. I concluded that the overall hedgerow connectedness of a landscape is therefore important both to bumblebee movement and to those plants which depend on bumblebees for pollination services.

My postdoctoral work investigated the true pollinators of three endemic, threatened bird pollinated plants on Tenerife in the Canary Islands. Previous work had suggested that these plants evolved floral traits as adaptations to pollination by flower specialist sunbirds, but there are no specialist flower-visiting birds on the Canary Islands. The previously undisputed theory stated that these ‘orphaned' plants subsequently appear to have co-opted passerine birds as sub-optimal pollinators following the sunbirds' ‘disappearance'. To test these ideas I carried out a quantitative study of the pollination biology of three of the bird pollinated plants, Canarina canariensis (Campanulaceae), Isoplexis canariensis (Veronicaceae) and Lotus berthelotii (Fabaceae). My fieldwork showed that the passerine chiff chaff ( Phylloscopus collybita ) was an effective pollinator of these species. The plants have become well adapted to pollination by these generalist birds that only occasionally visit flowers. In particular, the large nectar standing crop and extended flower longevities of Canarina and Isoplexis strongly suggest that they have evolved a “sit and wait” functionally specialised passerine bird pollination system, that effectively exploits these pollen vectors and is in no way suboptimum.

Other interests were inspired by my MSc in insect pest ecology, particularly biological control and glasshouse integrated pest management. I have always been fascinated by the array of complementary methods employed to manage pest numbers. Simple observation and knowledge of the pest's life cycle can highlight areas in which to target the pest most effectively rather than the blanket application of insecticide.

PhD Abstract: ‘The influence of linear landscape features on pollinator behaviour.' 

Linear landscape features such as hedgerows are important wildlife habitats, but their functional role in improving connectivity in fragmented habitats remains uncertain. This thesis studied the influence of both natural and artificial linear features on pollinator behaviour at medium and landscape scales. Observations along 30m transects, perpendicular to eight different hedgerows revealed that non-foraging pollinators were far more likely to exhibit linear flight next to the hedgerow than they were further out in the field. Using a medium-scale experimental design, three patches of potted Phacelia tanacetifolia (Hydrophyllaceae) were arranged equidistantly, with two of the patches connected by an artificial linear feature. Results demonstrated that there was significantly greater inter-patch movement by bumblebees ( Bombus spp.) between the connected patches than to the isolated patch even after the position of the feature was changed. The isolated patch was not approached from the other two patches. Bumblebees demonstrated high patch fidelity but their abundance in the connected patches was not necessarily greater than the isolated patch. There were no significant differences in hoverfly (Syrphidae) abundance between patches. Later, the same experimental array was scaled up to fit within the farm landscape structure, using an existing hedgerow as the connection. A similar pattern of flight directions emerged. In a landscape investigation, the reproductive success of Salvia pratensis (Labiatae) growing in patches with a high number of connecting hedgerows was compared with those plants growing within poorly connected patches. Pollinator abundance, pollen grains per stigma and seed yield, were greater in highly connected patches compared with patches with fewer connecting hedgerows. The overall connectedness of a landscape may therefore be important to both pollinator movement and those plants which depend on them for greater reproductive success. Linear landscape features might also represent navigational aids with which pollinators orient themselves.

CV

2005 – Present: I have recently been working in a variety of part time projects: 1) Wildlife Surveyor - a private commission to conduct a wildlife survey of private residents' communal gardens in Southampton. 2) Teaching and fieldwork assistant to undergraduate students at the University of Northampton.

January 2005-July 2005 Postdoctoral Research Assistant . Queen Mary College, University of London. Awarded a £30,000 NERC-funded grant with Prof. Lars Chittka and Dr Jeff Ollerton to investigate the pollination of Canary Island endemic plants, involving three months of fieldwork in the Anaga Mountains of Tenerife.

1999-2004 PhD . ‘The influence of linear landscape features on pollinator behaviour.' University of Northampton, Landscape and Biodiversity Research Group. Supervisors: Dr Jeff Ollerton and Dr Duncan McCollin.

1997-1998 MSc & DIC . Applied Entomology (Insect Pest Management).

Imperial College of Science, Technology and Medicine, London, Silwood Park Campus. MSc Project: ‘The impact of a localised insecticide application on the leaf-eating beetle Phratora vulgatissima (Chrysomelidae) and non-target species within short rotation coppice willow crops.' In collaboration with the Game Conservancy Trust.

1994-1997 BSc (Hons) 2:1. Environmental Biology.

Oxford Brookes University. BSc (Hons) Project: ‘The abundance and diversity of surface-active invertebrates in differing habitats with particular reference to ground beetles (Carabidae).'

Publications

Cranmer, L., McCollin, D. & Ollerton, J. (2011) Landscape structure influences pollinator movements and directly affects plant reproductive success. Oikos (pdf 640)

Ollerton, J; Johnson , SD ; Cranmer, L & Kellie, S (2003). The pollination ecology of an assemblage of grassland asclepiads in South Africa. Annals of Botany , 92 , 807-834. (Acrobat 1MB)

Ollerton, J & Cranmer, L (2002). Latitudinal trends in plant-pollinator interactions: are tropical plants more specialised? Oikos , 98 , 340-350. (Acrobat 131KB)

Cranmer, L ; Ollerton, J & McCollin, D (in prep.) Landscape structure directly affects bumblebee movements and plant reproductive success. To be submitted to Oikos .

Ollerton, J., Cranmer, L., Stelzer, R., Sullivan, S. and Chittka, L. (2008) Bird pollination of Canary Island endemic plants. Naturwissenschaften (Acrobat 291KB) DOI: 10.1007/s00114-008-0467-8

Ollerton, J; Cranmer, L ; Henderson, B & Gopaul, D (in prep.) Species richness and pollination ecology of Apocynaceae s.I. across a savannah-rainforest ecotone in Guyana . To be submitted to Annals of Botany .

Ollerton, J; Alarcon, R; Waser, N; Price, M; Watts, S; Cranmer, L ; Hingston, A; Peter, C & Rotenberry, J (in press). A global test of the pollination syndrome hypothesis. Annals of Botany.