ISSR markers in five North American Sceptridium species

Relationships among North
American Sceptridium (sensu Škoda) species are
often difficult to assess because of few stable distinguishing characters
and high intraspecific variability. We used ISSR-PCR to examine
relationships among four samples of Holubiella, 24 samples
representing four diploid North American Sceptridium species, and
a Russian Sceptridium sample. Nine ISSR primers yielded 147
polymorphic loci. We generated three neighbor-joining dendrograms using a
Jaccard, Nei & Li, or Dice coefficient. All three coefficients
cluster based solely on the presence of bands and not the absence. ISSR
data analyses across all three coefficients were consistent with published
analyses of DNA sequence data in
supporting Holubiella as sister to
all Sceptridium species sampled. Sister group
relationships among the four Sceptridium species were
not consistent across all three neighbor-joining analyses, and bootstrap
support was generally low. However, 26 of the 29 samples consistently
clustered with other samples of similar morphology, and these clusters
generally supported current species concepts. In taxa such
as Sceptridium with low DNA sequence variability among
species, ISSR-PCR may provide an important tool for evaluating
morphologically defined species, but additional data are necessary for
establishing robust hypotheses of phylogenetic relationships.