May we expect “granivory” by isopods also in their original terrestrial biotopes of Mediterranean region? 1, 2 S. Koprdová, 1 P. Saska, 1 A. Honěk, 1 Z.

Presentation on theme: "May we expect “granivory” by isopods also in their original terrestrial biotopes of Mediterranean region? 1, 2 S. Koprdová, 1 P. Saska, 1 A. Honěk, 1 Z."— Presentation transcript:

1 May we expect “granivory” by isopods also in their original terrestrial biotopes of Mediterranean region? 1, 2 S. Koprdová, 1 P. Saska, 1 A. Honěk, 1 Z. Martinková 1 Crop Research Institute, Department of Entomology, Prague, Czech Republic 2 Czech University of Life Sciences, Faculty of Agrobiology, Food and Natural Resources, Department of Agroecology and Biometeorology, Prague, Czech Republic

2 WHY? recent studies – terrestrial isopods from central Europe 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) May we expect “granivory” by isopods also in their original terrestrial biotopes of Mediterranean region?

3 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“)

4 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)!!!

5 Armadillidium vulgare x Capsella bursa-pastoris

6 Hemilepistus reaumurii, locality near Kairouan – Tunisia Halocnemum strobilaceum (Amaranthaceae)

7 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

8 Overall seed predation Two sites ("moist" vs. "dry") situated c. 300 m apart placed Pairs of c. 25 cm 2 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

9 Overall seed predation 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 Average percentage germination (±SE) in arenas “protected from“ and “exposed to“ predators at “moist“ and “dry“ sites – combined data for 2005 and 2006

10 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

11 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!!!

12 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!

13 Relative importance of seed predators Consumption in laboratory recalculated per unit of dry body mass * Average for five top consumer species in no-choice experiments, 25 °C ** No-choice experiments, 20 °C *** No-choice experiments at 15 °C

14 Slugs consume but do not damage seeds 70% of seeds may germinate after gut passage

15 Seedling predation - methods Exposing seedlings to predation Measuring feeding of slugs Recording longevity of naturally established seedlings

16 Relative importance of seedling predators Consumption recalculated per unit of dry body mass Site i – moist Site ii - dry Seedling survival negatively correlated with slug abundance

17 Seed fate survived seedling predation seed predation non-germinable Moist Dry Site

18 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)

19 Thank you for your attention koprdova@vurv.cz

20 photo: MUDr. Pavel Schlemmer