Overview

Distribution

Endemic to the Galápagos Islands, particularly the western and southern islands, mostly occurring on coastal lava to within 1 m of high tide mark within range of sea spray (strongly salt tolerant) but also occasionally inland, for example on volcanic slopes on Isabela and Fernandina; sea-level to 50 m (exceptionally to 1500m on volcanic slopes).

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Physical Description

Diagnostic Description

Formal Description

Habit

Perennial herbs, erect initially, later procumbent, slender to robust and viny, to 3 m long. Stems 10-12 mm in diameter at base, green, densely pubescent, the pubescence composed of simple uniseriate trichomes of several lengths, the longest 0.5-2 cm long, ca. 0.1 mm wide, some gland-tipped, the longer ones with minute single-celled glands, among dense 1-2-celled trichomes, some gland-tipped, the glands unicellular and minute or multicellular, the plant with a strong citrus scent, smaller trichomes unicellular and usually gland-tipped.

Sympodial Structure

Sympodial units 3-foliate; internodes 1.5-3.5 (-6) cm long.

Leaves

Leaves interrupted imparipinnate, 5-25 cm long, 2-17 cm wide, bright green, densely pubescent with uniseriate glandular trichomes ca. 0.5 mm long, and shorter unicellular trichomes on both surfaces, more abundant abaxially, lime green; primary leaflets 2-4 pairs, subopposite or alternate, ovate or obovate, the base oblique and decurrent basioscopically, cuneate to cordate, the margins deeply lobed, forming secondary, tertiary and occasionally quaternary leaflets of varying sizes, the apex acute to rounded; terminal leaflet scarcely larger than the laterals, often with secondary leaflets, 0.5-2 cm long, 0.4-1 cm wide, the petiolule 0.2-0.3 cm long; lateral leaflets 2-7 cm long, 1-4.5 cm wide, the petiolule 0.1-0.6 cm long; secondary leaflets present, always more than (6-) 10-30 per leaf, 0.3-1 cm long, 0.2-0.5 cm wide, sessile or with a petiolule to 0.4 cm long; tertiary leaflets usually present, ca. 0.1-0.2 cm long, 0.1-0.2 cm wide, sessile or with a minute petiolule; interjected leaflets usually present, (3-) 5-22 (-30), 0.1-0.5 cm long, 0.1-0.5 cm wide, sessile or with a short petiolule to 0.3 cm long; petiole 0.6-4 cm long; pseudostipules absent.

Inflorescences

Inflorescences to 10 cm long, simple or occasionally 2-3-branched, with up to 12 flowers, usually ebracteate, but bract and bracteole-like leaflets occasionally present in some populations, peduncle 1-3.5 cm long, pubescent like the stems. Pedicels 0.5-1.8 cm long, articulated just below the middle. Buds 0.7-1 cm long, 0.3-0.4 cm wide, conical, straight, with the corolla about halfway exserted from the calyx just before anthesis.

Flowers

Flowers with the calyx tube 0.05-0.1 cm long, the lobes 0.3-0.6 cm long, 0.1-0.15 cm wide, linear, pubescent with long and short simple uniseriate trichomes, the apex acute; corolla 1.6-3.2 cm in diameter, pentagonal, occasionally somewhat bilaterally symmetric due to fusion of adjacent lobes, yellow, the tube 0.5-0.7 cm long, the lobes 0.7-1.3 cm long, 0.3-0.7 cm wide, densely pubescent along the midveins with tangled transparent uniseriate trichomes ca. 0.5 mm long, reflexed at anthesis; staminal column 0.3-0.7 cm long, narrowly cone-shaped, straight, the filaments 1-2.7 mm long, the anthers 0.3-0.45 cm long, the sterile apical appendage 0.1-0.2 (-0.4) cm long; ovary conical, minutely glandular-villous; style 0.4-0.8 cm long, straight, < 0.5 mm in diameter, usually included in the staminal column, rarely exserted to less than 0.5 mm long; stigma minute, green.

Fruits

Fruits 0.6-1.1 cm in diameter, globose, 2-locular, becoming pale to deep orange at maturity, glabrescent to densely pubescent with weak eglandular simple uniseriate patent trichomes to 3 mm long, and smaller uniseriate glandular trichomes with 4-celled heads; fruiting pedicels 0.7-1.5 cm long, curving towards the axis; calyx lobes in fruit accrescent, 1.4 cm long, 0.1-0.3 cm wide, often longer than fruit, basal half of calyx tightly appressed to berry base.

Seeds

Seeds 1.5-2.0 mm long, 0.8-1.2 mm wide, 0.4-0.5 mm thick, obovate, pale brown, pubescent with hair-like outgrowths of the lateral testa cell walls, these adpressed and giving a silky appearance to the surface or more often shaggy, narrowly winged (ca. 0.2 mm) at the apex and acute at the base.

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Life History and Behavior

Cyclicity

Phenology

Solanum galapagense flowers and fruits throughout the year in response to moisture.

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Evolution and Systematics

Systematics or Phylogenetics

Phylogeny

Solanum galapagense is a member of the Potato clade (sensu Weese & Bohs, 2007); within the tomatoes and wild relatives it is a member of the “Lycopersicon group” and is a member of section Lycopersicon.

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

References and More Information

Commentary

Solanum galapagense can be clearly differentiated from the rest of the ‘Lycopersicon’ species group on leaf morphology alone. Other discriminating characters included appressed sepals that exceed the ripe fruit diameter, the presence of bract like leaflets on the inflorescence and presence of branched inflorescences (sometimes 2-3 branched, very occasionally simple). These morphological characters were found at a lower frequency in S. cheesmaniae, only rarely in S. lycopersicum and S. pimpinellifolium. Note that the presence of appressed sepals is not always apparent in herbarium specimens because sepals apparently curl upwards as they dry and can become reflexed in herbarium specimens, in live plants they remain tightly appressed until fruit abscision.

Solanum galapagense has always been recognized as a distinct taxon (Darwin et al. 2003). Orange fruit color is only found in Solanum cheesmaniae and S. galapagense. This character is derived in these two species (Peralta & Spooner 2001) and separates them from S. pimpinellifolium and S. lycopersicum. Fruit color was described by Rick (1971) as a “dependable key character” with which to differentiate the Galápagos tomatoes from all others.

Solanum cheesmaniae and S. galapagense are both endemic to the Galápagos Islands. The introduction of cultivated tomatoes and the evidences of natural introgression with wild tomatoes (see Darwin et al. 2003), generate concern about in situ conservation of natural populations. These two species can be considered endangered (see Knapp, in press).

Darwin et al. (2003) identified Scouler s.n. (E), collected in 1826, as the oldest specimen of one of the Galápagos tomatoes. Since publication of that paper, we have discovered a specimen in BM collected by Archibald Menzies in 1791, probably from northern Isabela, where his ship (HMS Discovery) stopped very briefly on its way to the Pacific Northwest (Eric Groves, pers. comm.). The specimen was mis-labelled as “Sandwich Islands” (Hawa’i) and thus remained unnoticed until databasing of the herbarium as part of the PBI Solanum project began.

Various mis-spellings of Hooker’s epithet minor as minus (Lycopersicon esculentum Mill. var. minus Hook.f. and Lycopersicon cheesmanii L.E. Riley ssp. minus Hook.f.) have entered into some privately circulating lists, but are orthographic errors (minor is the comparative adjective of parvus, while minus is an adverb) and have no nomenclatural standing, and cannot be found even in early editions of Index Kewensis.

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Disclaimer

EOL content is automatically assembled from many different content providers. As a result, from time to time you may find pages on EOL that are confusing.

To request an improvement, please leave a comment on the page. Thank you!