THE EFFICIENCY OF THE STRATEGY OF MUCILAGINOUS SEEDS OF SOME COMMON ANNUALS OF THE NEGEV ADHERING TO THE SOIL CRUST TO DELAY COLLECTION BY ANTS

Groups of dry seeds of four annual plant species which occur in the Negev highlands were placed on a natural, dry or wet loess soil crust surface near Sede Boker on the Zin plateau during the autumn before the first rains, and on the first day with rain (1.15 mm). Ant nests ofMessor rugosuswere 8 to 14m from the experimental plot. The length of time it took these ants to collect the free or adhered seeds was observed. When the mucilaginous ombrohydrochoric seeds ofAnastatatica hierochuntica, Plantago coronopus, andCarrichtera annuaadhere to wet soil that remains moist, most of the seeds may have time to germinate in proper conditions before they are collected by ants. However, all but 5% of theReboudia pinnataseeds were collected within 2 h. The adhered seeds that had been moistened by wet soil crust and then dried, were collected by ants, in most cases, faster than when seeds and soil remained moist. Within 2 h none of the dry and free seeds situated on the dry soil surface remained. The first free seeds were collected after 7 min. Findings are discussed together with the mechanisms and strategies involved in seed dispersal by rain and germination of these plant species.