Galápagos tomatoes (Solanum section Lycopersicon) have long interested
scientists and plant breeders. Several morphological and physiological
characters found in the endemic Galápagos tomatoes have been bred into the
cultivated Solanum lycopersicum, making the native plants an invaluable
resource for the development of this important global crop.
Extensive fieldwork was carried out on twelve islands, old records were
confirmed, new records added, but several previously recorded populations of
endemic tomatoes could not be confirmed. I collected tomatoes from 12 islets
and Islands. Detailed morphometric analysis on c.400 plants and extensive
genetic studies on c.1,200 plants were carried out in addition to fieldwork and
natural history studies. Observations and experiments were carried out on
herbarium specimens, field collected and green house grown accessions. I
confirmed the presence of four taxa in the Galápagos Islands – two endemic
species S. cheesmaniae and S. galapagense, the latter here described as new,
and two introduced species S. pimpinellifolium and S. lycopersicum.
Hybrids were found involving all taxa growing in the Galápagos Islands.
Of particular interest is an extensive hybrid zone between S. cheesmaniae and
S. pimpinellifolium spanning 20km along the Baltra Road on Isla Santa Cruz.
Hybridization raises the threat of extinction by introgression and the possibility
of the evolution of a serious invasive species. Conservation recommendations
are proposed.
In addition, a genetic analysis was undertaken of 60 seed bank
accessions of all four tomato species from the Galápagos. Again, indications of
hybridization were found, raising the potential of introgression within the seed
bank collections, occurring potentially during rejuvenation cycles.
Furthermore, I propose a new outline for a generic invasive species
threat/impact scoring system. Applying this new system I class Solanum
pimpinellifolium as an alien invasive species and assess its impact on Isla
Santa Cruz in the Galápagos Islands
