其它可利用食物对小花宽瓣黄堇(Corydalis giraldii Fedde)种子散布的影响

作为蚁播植物种子的重要传播者,蚂蚁不但取食种子上附着的油质体,也喜食其它富含蛋白质、脂类、糖和维生素等的食物,因此环境中其它可利用食物的存在可能会影响蚂蚁对种子的搬运进而影响种子散布,但目前对于这种影响是如何发生的仍不清楚。在野外研究了蚂蚁对小花宽瓣黄堇(Corydalis giraldii Fedde)种子、肉、蜂蜜、苹果、馒头等食物的趋性和偏好程度,以及添加食物后蚂蚁对种子的拜访频率和搬运效率,以揭示其它可利用食物如何影响蚂蚁觅食和取食偏好,进而影响小花宽瓣黄堇种子散布。结果显示,在所诱捕的8种蚂蚁中,玉米毛蚁(Lasius alienus(Foerster))和丝光蚁(Formica fusca Linnaeus)是小花宽瓣黄堇种子的主要搬运者,不同食物诱捕的玉米毛蚁数量无显著性差异(P0.05),但蜂蜜和苹果诱捕的丝光蚁数量均显著大于种子(P0.05)。玉米毛蚁和丝光蚁均为杂食性,在觅食中分别行使群体募集和简单协作性募集。在仅有种子的对照处理中,玉米毛蚁和丝光蚁对种子的拜访频率分别为(38.73±4.57)头和(30.8±2.87)头(40min,n=15),两种蚂蚁对种子的拜访频率差异不显著(P0.05);玉米毛蚁和丝光蚁搬运种子的效率分别为(33.87±4.22)粒和(16.27±3.35)粒(40min,n=15),玉米毛蚁的搬运效率显著高于丝光蚁(P0.05)。与对照相比,添加馒头、苹果和蜂蜜后丝光蚁对种子的拜访频率显著降低(P0.05),分别为(15.6±3.61)头、(9.07±1.4)头和(7.67±1.58)头(40min,n=15);添加苹果和蜂蜜后丝光蚁对种子的搬运效率显著降低(P0.05),分别为(3.47±1.17)粒和(2.87±0.9)粒(40min,n=15);添加不同食物后玉米毛蚁对种子的拜访频率和搬运效率均无显著变化(P0.05)。研究结果表明行使群体募集的玉米毛蚁比行使简单协作募集的丝光蚁有更高的种子搬运效率,添加食物后影响丝光蚁对种子的拜访频率和搬运效率,这说明其它可利用食物对小花宽瓣黄堇种子散布的影响与搬运蚂蚁的种类及其觅食的募集方式有关。研究结果可为进一步研究蚂蚁与植物(种子)间的互利共生关系及其影响因素提供资料。

Effect of alternative food resources on the seed dispersal of an ant-dispersed plant Corydalis giraldii Fedde (Papaveraceae)

Myrmecochory is a widespread and important ecological interaction in which ants benefit by obtaining nutrition from lipid-rich elaiosomes attached to seeds. Plants benefit from having their seeds dispersed from parent plants. Given that ants are generally polyphagous, we hypothesized that the availability of alternative food resources other than the diaspore itself may influence ant-mediated seed dispersal. We used the myrmecochore Corydalis giraldii Fedde (Papaveraceae), the seeds of which are attached to a lipid-rich elaiosome that is attractive to ants, to investigate: (1) whether dispersing ants are more prone to alternative resources than the diaspore itself; and (2) how the availability of alternative resources affects ant activity and feeding preference, and, hence, ant visiting frequency to seeds and the rate of seed removal. In a field experiment, the pitfall trapping method was used to examine ant feeding preference among five dietary items (i.e. meat, honey, apple, bread, and seed of C. giraldii). Additionally, two artificial diaspore depots were offered near the ant nests, one with seeds and the other with either meat, honey, bread, apple fragments, or no food (control), to determine the effect of alternative food resources on seed removal. While eight ant taxa (ca. 837 individuals) were captured in the sampling plots, only two species (Lasius alienus and Formica fusca) were dominant and effective dispersers, with mass recruitment and simple cooperative recruitment, respectively. In fifteen 40-minute trials, the mean number of ant visits to the seeds was 38.73±4.57 times, and the mean rate of seed removal was 33.87±4.22 in L. alienus. No significant difference in either ant visit frequency or seed removal rate was found in L. alienus following the addition of alternative food types (P > 0.05). Both ant visit frequency and the rate of seed removal in F. fusca were reduced significantly by the addition of alternative food (P < 0.05). In particular, ant visit frequency decreased from the mean of 30.8±2.87 individuals (n=15, 40 min) in the control to 15.6 ± 3.61, 9.07±1.4,and 7.67±1.58 individuals with the addition of bread, apple fragments, and honey, respectively. The rate of seed removal decreased from 16.27±3.35 individuals (n=15, 40 min) in the control to 3.47±1.17 and 2.87±0.9 with the addition of apple fragments or honey, respectively. This suggested that the frequency of ant visits and removal rate of seeds in F. fusca strongly differed from that in L. alienus when alternative foods were presented along with the plant. We concluded that the indirect effects of alternative resources on seed dispersal depended on ant identity and its recruitment mode, contributing to the understanding of the fate of diaspores adapted for ant dispersal.