Temperature and rainfall influence the distribution, diversity and
habitat suitability of Solanum species of the Leptostemonum clade
in Uganda
Abstract
Solanum species of the Leptostemonum clade were mapped, and
predictions made on the distribution and possible habitats using a set
of environmental variables. The variables were temperature, rainfall,
slope, soil and land use/cover. During field surveys, location presence
data (geocoded with Germin S90 GPS) was collected. Additional data were
obtained from herbarium specimens kept at Makerere University Herbarium
and others obtained from the Global Biodiversity Information Facility.
Distribution maps were generated in ArcMap software. Using MaxEnt
software (version 3.3.3), spatial distribution models were generated.
Model evaluation was based on the generated Area Under Curve (AUC) of
both the testing and training gain data. The Jackknife test was used to
assess the importance of each environmental variable in predicting
species occurrence. Eighteen species were analyzed out of the 20 known
to occur in the country. Solanum chrysotrichum was
recorded as a new species to Uganda, thus, a new total of 21 species
known for the country. Presence of S. forskalii in Uganda was
confirmed. Most of the species occur in disturbed habitats in the land
use/cover areas defined as croplands, tree cover and grasslands. The
highest species richness was recorded in south western Uganda with a
total of 11 species. Karamoja had unique diversity with species
restricted to the region and these included S. forskalii, S.
lanzae, S. coagulans and S. hastifolium. The environmental parameters
selected for the study when used in combination had a good fit in
predicting the occurrence of species as revealed by the high AUC values.
Temperature and rainfall were the most useful variables in predicting
occurrence of Solanum species. Karamoja region and south western
Uganda are hotspots for conservation of the spiny Solanum.
Periodic field surveys should be carried out to assess the effect of
climate change and anthropogenic disturbance on the occurrence of the
species.