Endophytic Fungi 261addressed before a clear understandin gof tropical
endophyte diversity can emerge. First, consistent
and biologically meaningful species concepts are
needed that incorporate sterile (non-sporulating)
fungi, which typically dominate endophyte cul-
tures (Box 15.3). Second, extensive sampling
within sites is needed to reliably estimate host
affinity. Third, comparative studies are needed
to assess spatial structure and beta-diversity.
Although several studies have addressed one or
more of these goals, none has fully satisfied these
criteria. Moreover, uncertainty exists regarding
the potential diversity of unculturable species,
the degree of overlap between endophytes and
other fungal guilds (i.e., pathogens, saprophytes;
Box 15.4), and the appropriate spatial scale at
which to estimate species turnover (amon gleaves,
trees, or forests?). The number of endophyte