Larval and adult seed consumption affected by the degree of food specialization inAmara(Coleoptera: Carabidae)

Abstract

AbstractMany carabid beetles (Coleoptera: Carabidae) are known to feed on plant seeds, but the level of specialization on this food differs. This is the first study in which seed consumption is assessed for all larval instars and adults of ground beetles. Three species ofAmarawith syntopic occurrence,Amara aenea(DeGeer),Amara familiaris(Duftschmid) andAmara similata(Gyllenhal), were examined. Larvae of all three instars and adults were fed seeds ofStellaria media(L.) Vill.,Capsella bursa‐pastoris(L.) Med. andTaraxacum officinaleWick. ex Wigg. in a laboratory no‐choice experiment. In general, larvae, particularly the first instar, showed greater differences in seed consumption than the adults, although the latter showed similar but less marked pattern.Amara aeneaconsumed all offered seed diets in all life stages. All three larval instars of granivorousA. familiarisalmost exclusively fed on seeds ofS. mediaand the adults also ate significantly more of this than other seeds.Amara similataconsumed mostly seeds ofC. bursa‐pastorisin the first instar and adult stages, whereas the larvae of the later instars seemed to be unspecialized on particular seed diet. Differences in seed‐specific consumption between larval instars in granivorous carabids are reported for the first time. The results provide further support for the parallel evolution of various degrees of granivory in the genusAmara, which may ultimately facilitate species coexistence. The daily seed consumption by the larvae was comparable or (in case of the third instar) even higher than that by the adults. Hence, we suggest that larvae may be the important consumers of seed in the field and should not be forgotten when seed predation is assessed.