Orchid biology: from Linnaeus via Darwin to the 21st century. Preface

Abstract

Orchidaceae are the largest family of flowering plants, with at least 24,000 species, and perhaps better than any other family of flowering plants, orchids represent the extreme specializations that are possible. As a result, they have long fascinated luminaries of the botanical world including Linnaeus and Darwin, but the size of the family has historically been an impediment to their study. Specifically, the lack of detailed information about relationships within the family made it difficult to formulate explicit evolutionary hypotheses for such a large group, but the advent of molecular systematics has revolutionized our understanding of the orchids. Their complex life histories make orchids particularly vulnerable to environmental change, and as result many are now threatened with extinction. In this Special Issue we present a series of 20 papers on orchid biology ranging from phylogenetics, floral evolutionary development, taxonomy, mycorrhizal associations, pollination biology, population genetics and conservation.

Fig. 1.

Eriaxis rigida (Vanilloideae) is endemic to the Pacific island of New Caledonia, where it grows on ultramafic maquis. Its closest relative, Clematepistephium smilacifolium, in contrast, is a climbing vine found in the New Caledonian rainforests (photograph: K. M. Cameron).

Fig. 2.

Gomesa echinata (previously known as Baptistonia echinata; Oncidiinae, Cymbidieae, Epidendroideae) from Brazil (photograph: M. W. Chase).

Fig. 3.

Stenorrhynchos speciosum (Cranichideae, Orchidoideae) from Costa Rica (photograph: M. W. Chase).

Fig. 4.

Caladenia longicauda (Caladeniinae, Diurideae, Orchidoideae) from Western Australia (photograph: R. J. Smith).

Fig. 5.

Dichaea morrisii (Zygopetalinae, Cymbidieae, Epidendroideae) is a frequently encountered species found throughout tropical America. It has muricate ovaries, a homoplasious feature in Dichaea (photograph: K. M. Neubig).

Fig. 6.

The specimen of Dendrophylax funalis (Angraecinae, Vandeae, Epidendroideae) from the Linnean Herbarium. Linnaeus mistakenly called this Cactus parasiticus, causing taxonomic problems in Cactaceae (image reproduced with kind permission of the Linnean Society of London).

Fig. 7.

Ophrys insectifera (Orchidinae, Orchidoideae) on Gotland. ‘Its flowers bear such a resemblance to flies, that an uneducated person who sees them might well believe that two or three flies were sitting on a stalk’ (Linnaeus; see Edmondson, 2007; Photograph: K. W. Dixon).

Fig. 8.

Dactylorhiza incarnata var. ochroleuca (Orchidinae, Orchideae) on Gotland (photograph: M. Hedrén).

Fig. 9.

Hippotion celerio visiting flowers of Mystacidium capense (Angraecinae, Vandeae, Epidendroideae) in South Africa (photograph: S. D. Johnson).