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Roberts, David L.

Job title: 

Honorary Research Associate

Joined Kew: 


Qualifications and appointments: 
  • BSc (Hons) Botany, Univ of Wales, Aberystwyth, 1996
  • MPhil, Univ. of Wales, Aberystwyth, 1997
  • PhD, Univ. of Aberdeen, Scotland, 2001
  • Honorary Research Fellow, School of Life Sciences, University of Sussex, 2009
  • Sarah & Daniel Hrdy Fellowship in Conservation Biology - Dept. of Organismic & Evolutionary Biology, Harvard University, USA, 2007-2008
  • Editorial Board, Endangered Species Research
  • Editor, Orchid Research Newsletter
  • Advisor, Malesian Orchid Journal
  • Scientific Advisor to the UK government on the Convention on International Trade in Endangered Species (CITES) issues relating to the trade in orchids

Research on species detectability, extinction, response of orchids to climate change and orchid epiphyte ecology.

Extinction Models & Their Application - Estimating the probability that a species is extinct and the timing of extinctions is of fundamental importance in a range of fields of biology.  Even for species that attract considerable attention, any level of certainty is difficult to achieve because any statement of extinction is probabilistic. Conservation priorities are currently guided more by raw estimates of diversity than by any measure of how quickly that diversity is being lost. Estimating the probability that a species is extinct and the timing of those extinctions is of fundamental importance in setting priorities to manage biodiversity loss. Much of my work in this field is aimed at the development of statistically rigorous methods for understand extinction process. Through the development of large datasets, I aim to test the various methods using L-moment diagrams and probability plot correlation coefficient hypothesis tests to evaluate their goodness-of-fit. The eventual aim is to use these methods to quantify local extinction patterns and their causes by generating maps of extirpation patterns that can be used for secondary analyses (i.e., relating extirpation to land use changes, climate, edge effects, etc).

Species Detectability - Any attempt to use biological collections to draw inferences about species needs to have an understanding of the collection process. For example, the relative paucity of specimens of some taxa may be related to their time since discovery and the time for specimens to accumulate in collections. This begs the question as to why taxa are discovered when they are and whether conservation and biodiversity prioritisation may reflect a level of conspicuousness and accumulation of knowledge? Perhaps even more importantly is whether what we are collecting is representative of biodiversity or are rapid biodiversity assessments merely an index of human cognitive behaviour?

Orchid & Climate Change - Global climate change is already altering the timing of important developmental and behavioural events in plants, birds, amphibians, and insects. Despite some impressive phenological records, there is both a lack of long-term datasets to study these events as well as a molecular understanding of the mechanisms involved. Changes in species' ranges and trophic relationships in response to climate warming affect the interactions of their populations.  Highly co-evolved pollination systems, such as those in orchids, could be particularly susceptible to disruption. A wealth of specimen-based records may be found in biological collections. These specimens provide verifiable information on the distribution of taxa through space and time, and represent much under-used phenological datasets. A number of phenological studies have demonstrated that herbarium specimens can be used in climate change research, but there has been no direct validation of their usefulness for this purpose. With my PhD student, we have undertaken the first validation of the use of herbarium specimens for phenological studies. Further, I am working on the genetic basis of phenological responses in orchids by correlating FT expression levels with flowering. This offers an exciting interdisciplinary approach towards obtaining the molecular biomarkers for responses to climate change in wild-plants.

Epiphyte Seed Dispersal & Canopy Structure - Three years after the On the origin of species Darwin (1862) published On the various contrivances by which British and foreign orchids are fertilised by insects' in support of his theory of evolution by natural selection. Since Darwin's initial observations, most orchid research has focussed on their pollination biology, with other areas of orchid ecology such seed dispersal having been neglected. However, Darwin did speculated that 'the great grandchildren of a single plant [of Orchis maculata] would nearly 'clothe with one uniform green carpet the entire surface of the land throughout the globe' What puzzled him though was 'What checks this unlimited multiplication cannot be told. The minute seeds within their light coats are well fitted for wide dissemination' This perception of their immense dispersability still continues with virtually no quantitative analysis or data. I am currently the effects of canopy heterogeneity, seed release height and inertia on wind dispersal kernels of epiphytic orchid seeds, using the recently developed Regional Atmospheric Modelling System-based Forest Large Eddy Simulation. Further, natural systems such as tree canopies exhibit fractal patterns, exploring the physics of fractal-generated turbulence will enable us to understand these complex systems through lab-based flows. This has major implications for our understanding of the effects of habitat fragmentation and selective logging on canopy integrity and seed dispersal.

Selected publications: 

Bell, A.K., Roberts, D.L., Hawkins, J.A., Rudall, P.J., Box, M.S., Bateman, R.M. (2009) Comparative micromorphology of nectiferous and nectarless labellar spurs in selected clades of subtribe Orchidinae (Orchidaceae). Botanical Journal of the Linnean Society, 160: 369-387.

Duffy, K. J., Kingston, N. E., Sayers, B. A., Roberts, D. L., Stout, J. C. (2009) Inferring national and regional declines of rare orchid species using probabilistic models. Conservation Biology, 23: 184-195.

Roberts, D.L., Marshall, C.R. (2009) Are higher taxa described earlier or later than expected by chance? Systematics and Biodiversity, 7.

Vogel, R.M., Hosking, J.R.M, Elphick, C.S., Roberts, D.L., Reed, J.M. (2009) Goodness-of-fit for probability distributions of sightings as species approach extinction. Bulletin of Mathematical Biology, 71: 701-719.

Roberts, D.L., Dixon, K.W. (2008) Orchids. Current Biology, 18: R325-R329.