Transcript 22-KOPRDOVA

May we expect “granivory” by isopods
also in their original terrestrial biotopes
of Mediterranean region?
1, 2
1Crop
S. Koprdová, 1P. Saska, 1A. Honěk, 1Z. Martinková
Research Institute, Department of Entomology, Prague, Czech Republic
2Czech University of Life Sciences, Faculty of Agrobiology, Food and Natural Resources,
Department of Agroecology and Biometeorology, Prague, Czech Republic
May we expect “granivory” by isopods
WHY?
also in their original
terrestrial biotopes
• recent studies – terrestrial isopods from central Europe
of Mediterranean region?
are granivorous!!!
• important seed and seedling predators together with
carabid beetles and slugs
• soil moisture is probably the main factor affecting the
distribution and abundance of isopods (Heely
1941/1942, Warburg et. al 1984)
Matter of this lecture
• to introduce terrestrial isopods (Crustacea: Isopoda:
Oniscoidea) and to discuss their relative importance in
their original biotopes
• model species (Taraxacum officinale) in Czech Republic
- relative importance of the main invertebrate
predator groups in seed and seedling predation
- variation in predation between sites
(“moist“ x “dry“)
Crustacea: Isopoda: Oniscoidea
• app. 3600 members of Oniscoidea worldwide
• 42 species in Czech Republic
• 213 species of Oniscoidea in Greece (137 of which
are endemic)
• ranging from tropics at rain forests to desert
• terrestrial isopods are considered detritivores (Sutton
1972, Hassall & Rushton 1982, Zimmer 2002)
• granivory established recently (Saska 2008)!!!
Armadillidium vulgare x Capsella bursa-pastoris
Hemilepistus reaumurii, locality near Kairouan – Tunisia
Halocnemum strobilaceum (Amaranthaceae)
Dandelion
Taraxacum officinale Weber ex Wiggers
Established facts:
• Seed produced during the
whole vegetative season
• Mortality c. 95 % before
reaching stage of 1st true leaf
• Important seed predators are
ground beetles
Overall seed predation
• Two sites ("moist" vs.
"dry") situated c. 300 m
apart placed
• Pairs of c. 25 cm2 plots,
one protected from and the
other open to invertebrate
predation
• Ten replicates at each site
exposed in monthly
intervals from April to
October
• Seeds germinated after
rainfall counted
Overall seed predation
Average percentage germination (±SE) in arenas “protected from“
and “exposed to“ predators at “moist“ and “dry“ sites – combined
data for 2005 and 2006
• About 70 % of seeds
germinated on plots protected
from predation and 30 % on
plots exposed to seed
predation
• This means that about 60 %
of germinable seeds was
removed by seed predators
before natural germination
occured
Seed predators - ground beetles
Dominant carabid genera
(pitfall traps):
Amara
Harpalus
Ophonus
Pseudoophonus
(10 spp. in total)
- taxonomic composition
similar at both sites
photo by P. Klimeš
Seed predators - isopods
Dominant (pitfall traps):
Armadillidium vulgare
Trachelipus rathkii
- taxonomic composition
similar at both sites
Photo by P. Čáp
Seed-feeding established only
recently!!!
Seed predators - slugs
Dominant (plasticine trays):
Arion lusitanicus
-consumption of plasticine higher
at moist site
-large proportion of seeds eaten
was excreted apparently undigested
Preferred food: living plants in all
stages of development, dead plant
remnants
!Invaded the territory only in
1993!
Relative importance of seed predators
Consumption in laboratory recalculated per unit of dry body mass
0.4
-1
-1
Consumption (seeds mg d )
*
0.3
**
0.2
0.1
***
0.0
Ground beetles
Isopoda
Slugs
* Average for five top consumer species in no-choice experiments, 25 °C
** No-choice experiments, 20 °C
*** No-choice experiments at 15 °C
Seedling predation - methods
Recording longevity of
naturally established seedlings
Measuring feeding of slugs
Exposing seedlings to predation
Site i – moist
Site ii - dry
Consumption (seedlings mg-1d-1)
Seedling
negatively
correlated
Relativesurvival
importance
of seedling predators
withrecalculated
slug abundance
Consumption
per unit of dry body mass
0.2
0.1
0.0
Ground beetles
Isopoda
Slugs
Seed fate
survived
seedling predation
seed predation
non-germinable
Moist
Dry
Site
Conclusions
• Overall seed predation varied little between sites
• Most important ground beetles
• Slugs may eat seeds which remain germinable after gut
passage
• Overall seedling predation varied between sites (moisture)
• Slugs are most important seedling predators
• Isopods are of intermediate importance (both seeds and
seedlings)
Thank you for your attention
[email protected]
photo: MUDr. Pavel Schlemmer