Abstract:
Identification of fungi and the International Code of Nomenclature underpinning this process, rests
strongly on the characterisation of morphological structures. Yet, the value of these characters to define species in
many groups has become questionable or even superfluous. This has emerged as DNA-based techniques have
increasingly revealed cryptic species and species complexes. This problem is vividly illustrated in the present
study where 105 isolates of the Botryosphaeriales were recovered from both healthy and diseased woody tissues
of native Acacia spp. in Namibia and South Africa. Thirteen phylogenetically distinct groups were identified based
on Internal Transcribed Spacer (ITS) rDNA PCR-RFLP and translation elongation factor 1-α (TEF1-α) sequence
data, two loci that are known to be reliable markers to distinguish species in the Botryosphaeriales. Four of these
groups could be linked reliably to sequence data for formerly described species, including Botryosphaeria dothidea,
Dothiorella dulcispinae, Lasiodiplodia pseudotheobromae and Spencermartinsia viticola. Nine groups, however,
could not be linked to any other species known from culture and for which sequence data are available. These
groups are, therefore, described as Aplosporella africana, A. papillata, Botryosphaeria auasmontanum, Dothiorella
capri-amissi, Do. oblonga, Lasiodiplodia pyriformis, Spencermartinsia rosulata, Sphaeropsis variabilis and an undescribed
Neofusicoccum sp. The species described here could not be reliably compared with the thousands of
taxa described in these genera from other hosts and regions, where only morphological data are available. Such
comparison would be possible only if all previously described taxa are epitypified, which is not a viable objective
for the two families, Botryosphaeriaceae and Aplosporellaceae, in the Botryosphaeriales identified here. The extent
of diversity of the Botryosphaeriales revealed in this and other recent studies is expected to reflect that of other
undersampled regions and hosts, and illustrates the urgency to find more effective ways to describe species in
this, and indeed other, groups of fungi.
