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2 Posts tagged with the hawkmoth tag

Many species and larger taxonomic groups, especially invertebrates, have been little studied in terms of their patterns of geographical distribution - biogeography - and even basic information, inventories and assessments are missing.  A key reason for this is that collecting and sampling has been too limited and too uneven: there are simply no good baseline data on distributions.


Ian Kitching of the NHM Life Sciences Department, with colleagues from the University of Basel, Switzerland, and Yale University, USA, set out to establish why inventories for the hawkmoths of Sub-Saharan Africa are incomplete, considering human geographical and associated environmental factors.


Xanthopan morganii praedicta - a hawkmoth found in Madagascar and East Africa


They used a database of hawkmoth distribution records to estimate species richness across 200 x 200 km map grid cells and then used mathematical models predict species richness and  map region-wide diversity patterns. Next, they estimated cell-wide inventory completeness related to human geographical factors.


They found that the observed patterns of hawkmoth species richness are strongly determined by the number of available records in grid cells. Vegetation type is an important factor in estimated total richness, together with heat, energy availability and topography. Their model identified three centres of diversity: Cameroon coastal mountains, and the northern and southern East African mountain areas. Species richness is still under-recorded in the western Congo Basin and in southern Tanzania/Mozambique.


What does this mean?  It means that sampling (and therefore our knowledge) of biodiversity is heavily biased.  We have good data and information where there is higher population density; for more accessible and less remote areas; for protected areas and for certain areas where there was collecting in colonial periods.  If it is easy to get to, not too difficult to access, there are more people around and there have been longer histories of collecting: we have better knowledge. 


This is important in how we understand biodiversity and in how we make decisions with our knowledge to protect forests or other areas.  But this study means that we can take account of data gaps if we are looking at larger scale patterns of diversity.  It shows that baselines for broad diversity patterns can be developed using models and what data there is available.  We can identify the "known unknowns" in terms of information gaps in part by looking at human geographical features - the models can help set priorities for future exploration and collection as well as informing our understanding of biodiveristy.

Ballesteros-Mejia, L., Kitching, I.J., Jetz, W., Nagel, P. & Beck, J. 2013. Mapping the biodiversity of tropical insects: species richness and inventory completeness of African sphingid moths. Global Ecology & Biogeography 22: 586-595. (doi: 10.1111/geb.12039)


Ian Kitching, together with colleagues at the University of California, National University of Singapore and the University of Erlangen, Germany, has published a review paper charting the history of Charles Darwin’s prediction of coevolution between a long-spurred orchid, Angraecum sesquipedale, and a long-tongued hawkmoth, Xanthopan morganii praedicta, from Darwin’s first observations in 1862 to the final demonstration of successful pollination in the wild in 2004.


Angraecum NaturalHistoryMuseum_PictureLibrary_012880_IA.jpg

Angraecum Sesquipedale


Darwin wrote in his 1862 work On the various contrivances by which British and foreign orchids are fertilised by insects, and on the good effects of intercrossing:


I fear that the reader will be wearied, but I must say a few words on the Angræcum sesquipedale, of which the large six-rayed flowers, like stars formed of snow-white wax, have excited the admiration of travellers in Madagascar. A whip-like green nectary of astonishing length hangs down beneath the labellum. In several flowers sent me by Mr. Bateman I found the nectaries eleven and a half inches long, with only the lower inch and a half filled with very sweet nectar. What can be the use, it may be asked, of a nectary of such disproportional length? We shall, I think, see that the fertilisation of the plant depends on this length and on nectar being contained only within the lower and attenuated extremity. It is, however, surprising that any insect should be able to reach the nectar: our English sphinxes have probosces as long as their bodies: but in Madagascar there must be moths with probosces capable of extension to a length of between ten and eleven inches!


A moth with such a long proboscis, Xanthopan morganii praedicta, was not described until 41 years after the publication of this book, and it was not observed to visit Angraecum until 1992, with further work to prove pollination since then.  Ian and colleagues discuss issues of co-evolution and predation in this excellent paper.


Xanthopan morganii praedicta NaturalHistoryMuseum_PictureLibrary_037535_IA.jpg
Xanthopan morganii praedicta

Arditti, J., Elliott, J., Kitching, I.J. & Wasserthal, L.T. 2012. ‘Good Heavens what insect can suck it’ – Charles Darwin, Angraecum sesquipedale and Xanthopan morganii praedicta. Botanical Journal of the Linnean Society 169: 403-432.