Fertilisation of Orchids - Influence

Influence

Michael Ghiselin has expressed the view that all studies of coevolution follow directly or indirectly from Darwin's orchid book, which was also the origin of all work on the evolution of extreme specialisation. Its publication led almost immediately to research by many other naturalists into specialisation and coevolution, in some cases analysing other taxa. In his autobiography, Darwin modestly recalled how this work had revived interest in Christian Konrad Sprengel's neglected ideas:

For some years before 1862 I had specially attended to the fertilisation of our British orchids; and it seemed to me the best plan to prepare as complete a treatise on this group of plants as well as I could, rather than to utilise the great mass of matter which I had slowly collected with respect to other plants. My resolve proved a wise one; for since the appearance of my book, a surprising number of papers and separate works on the fertilisation of all kinds of flowers have appeared; and these are far better done than I could possibly have effected. The merits of poor old Sprengel, so long overlooked, are now fully recognised many years after his death.

Among the many prominent biologists who began research on coevolution, Hermann Müller was particularly interested in the evolutionary sequence in which insects and flowers became adapted to each other. Like Darwin, he began with the premise that flowers were adapted to ensure cross-fertilisation, and added his own premise that most insects were not "limited by hereditary instinct to particular flowers". On this basis, he developed the view that specialisation develops from the need for flowers to attract pollinating insects (without making access too easy for non-pollinators), and from the evolution of pollinators to adapt to changes in the location of rewards such as nectar. He found that Alpine flowers tended to be visited by bees at lower altitudes, and by butterflies at higher altitudes, beginning research on the idea that plants at different altitudes were specialised for different pollinators. By comparing related plant species that he thought had diverged in form from a common ancestor, and testing whether they were visited by butterflies or bees, he was the first to use a combination of morphological and ecological approaches to understand patterns in the evolution of interactions and specialisation. His brother Fritz Müller used similar methods when studying mimicry in Brazil. The early development of ideas on specialisation and coevolution became increasingly focused on the problem of mimicry; Henry Walter Bates had initially raised this issue in a paper read to the Linnean Society of London in December 1861 in Darwin's presence, and published in November 1862.

Others basing their studies of reproductive ecology on Darwin's evolutionary approach included Friedrich Hildebrand and Severin Axell in Europe, Asa Gray and Charles Robertson in North America. In Italy, Federigo Delpino adopted the theory of descent but like Sprengel had a teleological approach and explained the mechanisms of flowers by the intervention of a "psychovitalistic intelligence". Delpino classified flowers on the basis of the pollinators they attracted, and coined many of the terms still in use such as pollination syndrome and ornithophily. There was an enormous increase in knowledge during this period. In 1874, Asa Gray paid tribute to Darwin's work on orchids for explaining "all these and other extraordinary structures, as well as of the arrangement of blossoms in general, and even the very meaning and need of sexual propagation". He credited Darwin with establishing the understanding that "Nature abhors close fertilization".

By the end of the 19th century, there were so many uncritical and unproven speculations about floral mechanisms that floral ecology became discredited. In the 1920s, it was revived with further developments in detailed analyses of insects' senses, led by researchers Frederic Clements, Karl von Frisch and others. Their experiments resulted in new information, including the discovery that some insects have ultraviolet vision, and findings involving bee learning and communication. Modern floral ecology has been reinvigorated by its relevance for evolutionary studies.