Tropical Forest Community Ecology

Endophytic Fungi 255

the intervenin gyears, the few studies on trop-
ical endophytes have been primarily descriptive,
with some attention to the impact of tropical
endophytes on estimates of global fungal diversity
(e.g.,FröhlichandHyde1999,Arnoldet al.2000).
Most of this work has focused on endophytes of
leaves (foliar endophytes), which are especially
diverse and abundant (Arnoldet al. 2000). Four
recent studies have provided the first evidence
for ecologically relevant roles of tropical foliar
endophytes, includin gincreased host resistance to
pathogens (Arnoldet al.2003) and physiological
costs in terms of water relations and photosynthe-
sis (Pintoet al.2000, Herreet al.2005b, Arnold
and Engelbrecht 2007). These studies represent
the tip of a very large iceberg: in as much as
the mycota of all ecosystems are understudied,
the endophytic fungi in any tropical forest remain
extremely poorly known.
Due to a growing interest from ecologists, bio-
prospectors, and mycologists, an expansion of
research infrastructure in the tropics, and the
development of new methods, the study of tropi-
cal endophytes is more accessible now than ever

before. While alpha taxonomic studies are still

sorely needed, the stage is also set for experimen-

tal manipulations of endophyte abundance and

diversity, and for addressin gecolo gical questions.

In this context, the purposes of this chapter are

three-fold: (1) to synthesize current knowledge

regarding the natural history of foliar endophytes

in tropical forests; (2) to examine current evi-

dence regarding their ecological roles; and (3) to

highlight a series of tractable questions for future

research. The overarchin g goal of this chapter

is to encourage multidisciplinary research into

the ecology of these little-known but ubiquitous

and potentially important symbionts of tropical

plants.

ENDOPHYTE TRANSMISSION IN

TROPICA LFORESTS

The vast majority of fungal endophytes asso-

ciated with leaves (hereafter, endophytes) are

Ascomycota, includin gall major linea ges of non-

lichenized, filamentous ascomycetes (Boxes 15.1