Comparative Parasitology 67(1) 2000 - Peru State College

liese, 1995; Marcogliese and Cone, 1997). Complex
life cycles are integrated within intricate
food webs, so parasites can be valuable indicators
of trophic ecology, structure of food webs,
food preferences, and foraging mode of hosts
(Bartoli, 1989; Williams et al., 1992; Hoberg,
1996; Marcogliese and Cone, 1997). Within this
ecological-trophic context, parasites can tell us
the following: (1) trophic positions in food webs
(what hosts eat and what eats them); (2) use of
and time spent in different microhabitats (e.g.,
even though Termpene Carolina is mainly a terrestrial
turtle, it hosts the digenean Telorchis robustus,
which uses tadpoles as second intermediate
hosts); (3) whether hosts are picking up
parasites via host switching, and if so, which
hosts might be in potential competition (e.g.,
guild associations were recognized in the Sea of
Okhotsk based on examining parasites (Belogurov,
1966)); (4) whether any host harbors parasites
that are likely to cause disease problems;
(5) whether the host changes diet during its lifetime,
including seasonally or regionally denned
changes in food habits or prey availability
(Bush, 1990; Hoberg, 1996); and (6) which
hosts are residents and which are colonizers in
the community. Because such a wide range of
information can be gleaned from relatively little
effort, parasites should be highly useful in all
biodiversity studies. Additional special cases for
the application of parasitological data are related
to their use as contemporary biogcographic indicators.
Analysis of parasite biogeography has
been a powerful approach for identification of
stocks or populations in fisheries management
(Williams et al., 1992) and among marine mammals
(Dailey and Vogelbein, 1991; Balbuena and
Raga, 1994; Balbuena et al., 1995).
We can maximize the use of this information
if we begin to think of parasites as biodiversity
probes par excellence and as libraries of natural
and geological history (Brooks et al., 1992;
Gardner and Campbell, 1992; Hoberg, 1996).
Parasites are admirably suited to augment the
development of conservation strategies through
the recognition of regions of critical diversity
and evolutionary significance (Gardner and
Campbell, 1992; Hoberg, 1997a).
The predictive power of parasitology in a
phylogenetic context becomes increasingly important
when attempts are made to elucidate impacts
from natural and anthropogenic perturbations
of faunas and ecosystems. In marine sys-
BROOKS AND HOBHRG—PARASITE BIODIVERSITY
tems, climatological forcing, such as that linked to
the El Nino-Southern Oscillation or to cyclical
changes in atmospheric circulation, dramatically
influences patterns of oceanic upwelling and water
masses, which are reflected in food web
structure and ultimately in parasite faunas. In
such situations, parasites should be well suited
to tracking variation in trophic dynamics and
host distributions on the global scale (Hoberg,
1996). Knowledge of the evolution of a hostparasite
assemblage can provide direct estimates
of the history of ecological associations and can
indicate the continuity of trophic assemblages
through time.
Parasites as Historical Indicators. Manter
(1966) made the most eloquent statement about
the significance of parasites for understanding
evolutionary and ecological phenomena:
Parasites . . . furnish information about present-day
habits and ecology of their individual hosts. These
same parasites also hold promise of telling us something
about host and geographical connections of
long ago. They are simultaneously the products of
an immediate environment and of a long ancestry
reflecting associations of millions of years. The
messages they carry are thus always bilingual and
usually garbled. As our knowledge grows, studies
based on adequate collections, correctly classified
and correlated with knowledge of the hosts and life
cycles involved should lead to a deciphering of the
message now so obscure. Eventually there may be
enough pieces to form a meaningful language which
could be called parascript—the language of parasites
which tells of themselves and their hosts both
of today and yesteryear. (Manter, 1966)
Phylogenetic systematics provided the Rosetta
stone for what are now called parascript studies
(Brooks and McLennan, 1993a). In the past 2
decades, since formalization of the parascript
concept (Brooks, 1977), the number of such
studies has increased dramatically (see reviews
in Brooks and McLennan, 1993a; Hoberg,
1997a). Today there is virtually no area of modern
comparative evolutionary biology and historical
ecology that has not been enriched by at
least one parascript study.
The concept of parascript was based on the
contention by Manter (1966) that parasites are
powerful biological indicators of recent and ancient
ecological associations and geographic distributions.
Parasites tell stories about themselves
and their hosts that involve evolutionary emergence
of complex ecological associations
throughout immense periods. These ideas dra-
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