Biology Reference
In-Depth Information
portions of thalli appear more susceptible to epiphyte colonization (Ballantine
1979
; Lobban and Baxter
1983
; Ducker and Knox
1984
; Pearson and Evans
1989
,
1990
; Arrontes
1990
). Patterns of epiphytic assemblages are also strongly
dependent on the intensity of grazing by various invertebrates or fishes (Lubchenco
and Gaines
1981
). The species composition of epiphyte guilds is also conditioned
by physical factors, particularly desiccation and wave action (Hayward
1980
;
Graham and Hanna
1989
; Longtin et al.
2009
). These factors strongly impact the
distribution and stability of suitable substrata and increase selective forces affecting
epiphyte growth (Benzing
1987
). Despite substantial work on marine epiphytes,
their population ecology has received little attention (Harlin
1987
; Longtin and
Scrosati
2009
; Longtin et al.
2009
).
Various types of interactions can be established between basiphytes and epiphytes,
but only a few studies, based on both wild and laboratory-infected material, report on
the contact surface established between epiphytes and their hosts (Rawlence
1972
;
Rawlence and Taylor
1972
; Ducker and Knox
1984
; Gonzalez and Goff
1989
;
Gonzalez et al.
2003
; Dawes et al.
2000
; Leonardi et al.
2006
).Thedamagecaused
by an epiphyte to its basiphyte can be highly variable and is mainly influenced by the
type of anatomical association and the incidence of the epiphyte (Fletcher
1995
).
According to Linskens (
1963
), holo-epiphytes are those attached to the outer layers of
the host, whereas amphi-epiphytes are deeply anchored in the tissue of their hosts.
Linskens (
1963
) suggested, however, that the type of anatomical contact is highly
variable and determined by the nature of the partners. Epiphytes attach via single cells,
filamentous bases, or massive rhizoidal structures. Host-epiphyte interfaces were
typed and their relative abundance and temporal variability were monitored to unravel
the mechanisms of host recognition and host damage that could explain the loss of
crops and the negative effects of epiphytism in
Gracilaria chilensis
farming (Leonardi
et al.
2006
): Five types of anatomical relationships were detected.
Infection type I
included the epiphytes weakly attached to the surface of the host and not associated
with damage of host tissues (i.e.,
Hincksia mitchelliae
,
H. granulosa
and
Ectocarpus
acutus
).
Infection type II
included those epiphytes strongly attached to the surface of
the host but not associated with any host tissue damage (i.e.,
Acrochaetium
sp.,
Antithamnionella
sp. and
Colpomenia sinuosa
).
Infection type III
included all the
epiphytes that penetrated the outer layer of the host wall without damaging its cortical
cells (i.e.,
Xenococcus
sp. and
Sahlingia subintegra
).
Infection type IV
included
epiphytes penetrating deep into the host cell wall, disorganizing the cortical tissue
(i.e.,
Ulva lactuca
and
Acrosorium corallinarum
).
Infection type V
included epiphytes
that penetrated deeply into the cortex, reached the medullary tissue, and caused
destruction of the host's cells in the area around the infection (i.e.,
Ceramium rubrum
and
Polysiphonia harveyi
). Prevalence varied with time and with infection type, with
types II and III reaching up to 80% and 90% of the thalli, respectively. Severity of
epiphyte infection was similar to the distribution of infection prevalence, with crustose
epiphytes colonizing up to 80% of the host surface.
It was also noted that epiphytes could actually be present on the host in the field,
yet in a “dormant” state, and that they later developed to maturity in the richer
culture conditions.
