Darwin’s Galapagos gourd: providing new insights 175 years after his visit

Abstract

DarwinÕs contributions to the field of biogeography, stressing the importance of his natural history specimens. Here, we illustrate how a plant collected by Darwin during his visit to Floreana and not collected since can provide insights into dispersal to oceanic islands as well as extinction of island plants, based on ancient DNA from DarwinÕs herbarium specimen.Keywords Cucurbitaceae, DarwinÕs herbarium, extinction, Galapagos, island biogeography, molecular clock, phylogenetics, plant viruses, Sicyos.During his voyage on the Beagle, Charles Darwin industriously collected natural history specimens and sent them home from various ports along the way (Briggs, 2009). On his return to Great Britain, he immediately began supervising work on the scientific results of the expedition, employing the help of specialists to record his fossils, fishes, mammals, birds and plants. Among the 209 plants that Darwin collected on the Galapagos Islands and sent to J. D. Hooker was a new species of Cucurbitaceae, Sicyos villosus J. D. Hooker (Fig. 1). Unlike his bird collections, Darwin labelled his plants by island, which is why we know that this cucurbit came from Charles Island, now Floreana. On the herbarium label, the species is described as ÔIn great beds injurious to vegetation.Õ Since then, this species has never been found again, despite intense search efforts of several botanists. Based on one fruit from a bag attached to DarwinÕs 175-year-old specimen in the Cambridge herbarium (Fig. 1, insert), one of us (H.S.) generated nuclear and chloroplast sequences to find out the affinities of this vanished mystery plant. We also tested its relationship to another endemic Galapagos cucurbit, the Santa Cruz gourd, Sicyocaulis pentagonus Wiggins, which is known from five collections on Santa Cruz and Isabela, but has not been collected in the past 35 years.Based on molecular data (Kocyan et al., 2007; Schaefer et al., 2008 Schaefer et al., , 2009, the New World Sicyoeae comprise a clade of about 150 species in 20 genera (Apatzingania, Brandegea, Cyclanthera, Echinocystis, Echinopepon, Elateriopsis, Frantzia, Hanburia, Linnaeosicyos, Marah, Microsechium, Parasicyos, Pseudocyclanthera, Rytidostylis, Sechiopsis, Sechium, Sicyocaulis, Sicyos, Sicyosperma, Vaseyanthus). Herbarium specimens of 76 Figure 1 The sole herbarium collection in existence of Sicyos villosus, collected by Darwin during his visit to Floreana in September 1835 and described as a new species by J. D. Hooker. The specimen is now in the Darwin herbarium, whose keeper, Professor J. Parker, granted permission to extract DNA from one of the seeds shown in the inset in the lower right (inset scale bar = 5 mm). Photograph by A. Tye.

Bird Nests in Museum Collections: A Rich Resource for Research

“…However, evidence from other fields and impromptu experimentation at the NHM has demonstrated that DNA can be obtained from a variety of dead plant materials, including preserved nests. The extraction of 'ancient' DNA has become routine in the study of sub-fossil plant material, archaeological sites and herbarium collections (Russo et al, 2008;Lister et al, 2010;Sebastian et al, 2010;Palmer et al, 2012). Attachment materials used to secure a nest to its site are often absent for both suspended and supported nests, but communication materials (camouflage/advertisement) can be examined in museum nests to illustrate and examine variation in use of materials with signal function.…”

Museomics illuminate the history of an extinct, paleoendemic plant lineage (Hesperelaea, Oleaceae) known from an 1875 collection from Guadalupe Island, Mexico

“…With the advent of the polymerase chain reaction (PCR), historical museum specimens have been included in phylogenetic or population genetic work and this has allowed the investigation of important topics such as the placement of extinct species in phylogenies (e.g. Wallander & Albert, ; Sebastian, Schaefer & Renner, ), the reconstruction of historic intercontinental movements of crops and their associated pests (Ames & Spooner, ; Schaefer & Renner, ; Yoshida et al ., ), and the origin of herbicide resistance alleles in weeds (Délye, Deulvot & Chauvel, ). The main problem with using museum specimens for these purposes is the low quality of DNAs that can be extracted, especially from poorly preserved samples that were collected several decades or centuries ago (Wandeler, Hoeck & Keller, ).…”

Radiation following long‐distance dispersal: the contributions of time, opportunity and diaspore morphology in Sicyos (Cucurbitaceae)

“…Among them is Sicyos , the focal clade of this study. Sicyos is a genus in the Cucurbitaceae that has 14 endemic species on the Hawaiian Islands (Wagner & Shannon, 1999), two species on the Galápagos Islands (Sebastian et al. , 2010a), two in Australia, one in New Zealand, and between 41 and 56 species in the Americas, depending on the taxonomic concept applied: several small genera have been included in Sicyos or segregated from it based mostly on fruit characters.…”