TY - JOUR
T1 - Reduced dispersal at nonexpanding range margins
T2 - A matter of disperser identity
AU - Ben Zvi, Gilad
AU - Seifan, Merav
AU - Giladi, Itamar
N1 - Funding Information:
We thank Ishai Hoffman, Ofir Altstein, Guy Van‐Bommel and Nataly Levine for helping with the observations and measurements in the field and for technical support throughout the research. Many others helped with field experiments, especially the Sde Boker Field School staff. We thank Shani Gleitmann and Yahel Porat for constructive discussion of aspects of the research. Dr. Inna Khozin‐Goldberg and Shoshana Didi contributed with the analysis and interpretation of the elaiosomes' fatty acid profiles. We thank three anonymous reviewers and the handling editor for extremely helpful comments that significantly improved the manuscript. This work was supported by an Israel Science Foundation grant (No. 834/15) to IG and by the JNF. This is publication # 1065 of the Mitrani Department of Desert Ecology.
Funding Information:
We thank Ishai Hoffman, Ofir Altstein, Guy Van-Bommel and Nataly Levine for helping with the observations and measurements in the field and for technical support throughout the research. Many others helped with field experiments, especially the Sde Boker Field School staff. We thank Shani Gleitmann and Yahel Porat for constructive discussion of aspects of the research. Dr. Inna Khozin-Goldberg and Shoshana Didi contributed with the analysis and interpretation of the elaiosomes' fatty acid profiles. We thank three anonymous reviewers and the handling editor for extremely helpful comments that significantly improved the manuscript. This work was supported by an Israel Science Foundation grant (No. 834/15) to IG and by the JNF. This is publication # 1065 of the Mitrani Department of Desert Ecology.
Publisher Copyright:
© 2020 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.
PY - 2020/6/1
Y1 - 2020/6/1
N2 - The evolution of dispersal at range margins received much attention recently, especially in the context of dynamic range shifts, such as those following climate change. However, much less attention has been devoted to study variation in and selection on dispersal at nonexpanding range margins, where populations are often small and isolated, and empirical test is dearly missing. To fill this gap, we tested whether dispersal of an ant-dispersed perennial plant (Sternbergia clusiana) is quantitatively and/or qualitatively reduced toward a nonexpanding range margin. We evaluated plant investment in dispersal structures (elaiosome), seed removal rates, and the relative abundance, activity, and behavior of low- and high-quality seed-dispersing ants in six sites ranging from mesic Mediterranean site to arid site (>600 to <100 mm of annual rainfall, respectively), which marks the southern range margin of the species. In a set of cafeteria and baiting experiments, we found that overall seed removal rates, the contribution of high-quality dispersers, maximum dispersal distance and dispersal-conducive ant behavior decreased toward range margins. These findings agree with a lower investment in reward by range margin plant populations, as reflected by lower elaiosome/seed ratio, but not by variation in the reward chemistry. More than variation in traits controlled by the plants, the variation in ant–seed interactions could be attributed to reduced presence and activity of the more efficient seed-dispersing ants in the marginal populations. Specifically, we found a mismatch between local distribution of potentially effective seed dispersers and that of the plant, even though those dispersers were observed in the study site. Interestingly, although the observed variation in the outcome of ant–seed interactions supported the prediction of reduced dispersal at nonexpanding range margins with small and isolated populations, the underlying mechanism seems to be incidental difference in the seed-dispersing ant community rather than a plant-mediated response to selection.
AB - The evolution of dispersal at range margins received much attention recently, especially in the context of dynamic range shifts, such as those following climate change. However, much less attention has been devoted to study variation in and selection on dispersal at nonexpanding range margins, where populations are often small and isolated, and empirical test is dearly missing. To fill this gap, we tested whether dispersal of an ant-dispersed perennial plant (Sternbergia clusiana) is quantitatively and/or qualitatively reduced toward a nonexpanding range margin. We evaluated plant investment in dispersal structures (elaiosome), seed removal rates, and the relative abundance, activity, and behavior of low- and high-quality seed-dispersing ants in six sites ranging from mesic Mediterranean site to arid site (>600 to <100 mm of annual rainfall, respectively), which marks the southern range margin of the species. In a set of cafeteria and baiting experiments, we found that overall seed removal rates, the contribution of high-quality dispersers, maximum dispersal distance and dispersal-conducive ant behavior decreased toward range margins. These findings agree with a lower investment in reward by range margin plant populations, as reflected by lower elaiosome/seed ratio, but not by variation in the reward chemistry. More than variation in traits controlled by the plants, the variation in ant–seed interactions could be attributed to reduced presence and activity of the more efficient seed-dispersing ants in the marginal populations. Specifically, we found a mismatch between local distribution of potentially effective seed dispersers and that of the plant, even though those dispersers were observed in the study site. Interestingly, although the observed variation in the outcome of ant–seed interactions supported the prediction of reduced dispersal at nonexpanding range margins with small and isolated populations, the underlying mechanism seems to be incidental difference in the seed-dispersing ant community rather than a plant-mediated response to selection.
KW - Sternbergia clusiana
KW - dispersal
KW - dispersal effectiveness
KW - mutualism
KW - myrmecochory
KW - range margins
UR - http://www.scopus.com/inward/record.url?scp=85083468000&partnerID=8YFLogxK
U2 - 10.1002/ece3.6220
DO - 10.1002/ece3.6220
M3 - Article
C2 - 32551051
AN - SCOPUS:85083468000
SN - 2045-7758
VL - 10
SP - 4665
EP - 4676
JO - Ecology and Evolution
JF - Ecology and Evolution
IS - 11
ER -