Phoenix clones: recovery after long-term defoliation- induced dormancy

Patrice A. Morrow* and Joel P. Olfelt Department of Ecology, Evolution and Behaviour, 1987 Upper Buford Circle, University of Minnesota, St. Paul, MN 55108, USA Department of Biology, Northeastern Illinois University, 5500 North St. Louis Avenue, Chicago, Illinois 60625-4699, USA *Correspondence: E-mail: [email protected] Abstract Many long-lived plants are known to prolong dormancy in response to abiotic stresses such as drought. We are unaware, however, of any reports of plants prolonging dormancy in response to biotic stresses such as herbivory. We monitored 140 putative Solidago missouriensis clones (hereafter clones ) ‡ 13 years before, during and after intense defoliation by the specialist herbivore Trirhabda canadensis. Eight of the clones produced no above-ground growth in the season following defoliation. Though apparently killed, these clones reappeared 1–10 years after they disappeared, with six of them robustly recovering in a single season. We used 38 RAPD markers to test the hypotheses (denoted by H and numbered with subscripts) that territories were recovered by (H1) seedling establishment or (H2) rhizomes. We compared predefoliation and post-recovery genotypes in two clones using the same 38 markers. Our data document the existence of very large clones (60–350 m with c. 700–20 000 ramets), and support the hypothesis that recovery is from rhizomes. Within-clone diversity is low, and the pre-defoliation and post-recovery genotypes match. We consider mechanisms that could enable plants entering dormancy with depleted resources to robustly recover, and the implications of dormancy for avoiding biotic stress such as that induced by T. canadensis.