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recognize only two species in this complex, one
from the “northern” part of the distribution area
(
Solanum candolleanum
from central and southern
Peru and north-western Bolivia), the other from
the “southern” part (
S. brevicaule
from northern
Bolivia to central Argentina). However, even
these two species are extremely similar, differing
primarily in their geography, and are difficult to
key out. A key is announced, but although based
on the insights from the replicated field trials (Van
den Berg
et al
., 1998; Alvarez
et al
., 2008) and a
thorough study of herbarium specimens, the au-
thors themselves warn that determinations will
often fail. The extensive synonymy proposed on
the Solanaceae Source website is based on the im-
practicality of morphological data to distinguish
these species and the low support they receive in
molecular phylogenetic studies.
This solution to the problem of the
brevi-
caule
complex, already envisaged by Ugent
(1970), who reduced the whole complex to one
species,
S. brevicaule
, was anticipated by several
studies (Van den Berg
et al
., 1996, 1998; Miller
and Spooner, 1999). Although a certain infra-
structure of the complex can be recognized,
leading to a series of geographically restricted
“species” from north to south, the morphomet-
ric studies mentioned above clearly showed that
many of the taxa involved could not be separ-
ated from each other reliably, and extensive syn-
onymy was unavoidable. The Solanaceae Source
website provides a workable taxonomic solution
and it would be wise to heed their warning:
and
Solanum astleyi
and enlarged terminal leaflet
in most other species). Giannattasio and Spooner
(1994a,b) reduced
Solanum toralapanum
to a sub-
species of
Solanum megistracrolobum
, and Spooner
et al
. (1997) reduced
S. astleyi
to a subspecies of
S. boliviense
. The treatment on the Solanaceae
Source website reduces most of the former spe-
cies names to synonyms of
S. boliviense
, accepts
Solanum sogarandinum
as a separate species,
but notes that it is extremely difficult to dis-
tinguish it from
S. boliviense
and indicates
that the status of other species still has to be des-
ignated.
Our own AFLP data (Van den Berg and
Groendijk-Wilders, 2007) and the CBSG data (Ja-
cobs
et al
., 2011) more or less clearly distinguish
a complex consisting of
S. boliviense
and
S. astleyi
(which are indistinguishable from each other)
from the rest of the species of series
Megistacroloba
.
The synonymizing of
S. astleyi
as subspecies of
S. boliviense
is not in line with the results of Jacobs
et al
. (2011), who in their Structure analysis
found no support for a subspecies level within
S. boliviense
. Reducing
S. astleyi
to a synonym of
S. boliviense
seems more logical. The AFLP data
also show an unexpected closer relationship between
S. megistacrolobum
and
Solanum sanctae- rosae
, with
S. toralapanum
sister to both, which would be in
line with the Solanaceae Source treatment. Jacobs
et al
. (2011) found only weak evidence for species
status for the combination of
S. megistacrolobum
and
S. toralapanum
, and for
S. sanctae-rosae
, but
the material with these species names clustered
separately from that of an
astleyi
/
boliviense
cluster.
All this leaves some doubt whether the synonymy
arrived at on the Solanaceae Source website is
too extreme.
We suspect that our synonymy will be
questioned by those using molecular marker
data, but we suggest that such workers wishing
to resurrect our synonymized names do so only
with morphological data needed to support the
identification of these species in realistic and
practical ways. Without such data, we envision
the perpetuation of alternative taxonomies,
variant identifications by different workers, and
the maintenance of unstable names and
taxonomic confusion in these important but
taxonomically confusing species related to the
cultivated potato.
The gene bank predicament
As the cultivated potato is an important crop and
its wild relatives are valuable potential sources
of useful traits to improve the crop, much energy
and time have been invested to collect, maintain,
and evaluate germplasm of the wild species. These
collections are maintained in gene banks, with
the most important collections at CIP (Inter-
national Potato Center, Lima, Peru), NRSP-
6
(Potato
Introduction Station, US Potato Genebank,
Sturgeon Bay, USA), and CGN (Centre for Gen-
etic Resources, Wageningen, the Netherlands).
Series Megistacroloba
Hawkes (1990) recognized
11
species in series
Meg-
istacroloba
, mostly relying on leaf dissection char-
acters (e.g. simple leaves in
Solanum boliviense