Understanding the Invasion Success and Spread of the Globally Introduced Marine Invertebrate, Diadumene Lineata.

摘要

Fundamental to understanding invasion ecology is the identification of the processes regulating how species persist and often thrive in regions and environments in which they did not evolve. A remarkable colonizing species serving as a model by which to address invasion hypotheses is Diadumene lineata, the world's most widely distributed yet understudied sea anemone. In only 15 years (1892--1906) D. lineata expanded from its native Asia (the only region where it undergoes sexual reproduction) to colonize all continental margins of the Northern Hemisphere, and in the 20th century colonized all but one continental shoreline of the Southern Hemisphere. I sought, through multiple lines of evidence, to elucidate the key elements of its biology, ecology, and physiology that may have provided the foundation for its global success. To understand how D. lineata populations respond to seasonal changes endured under severe continental climate regimes, I conducted the first long-term field survey of populations in a sublittoral epibenthic habitat. D. lineata showed a striking population increase in spring-summer and a decrease in fall-winter, with few individuals surviving through winter that are responsible for recolonization in the following spring-summer. I conducted laboratory experiments with three populations from Maine to Delaware to determine the effects of temperature, body size and geographic origin on reproduction and growth. D. lineata reproduced asexually via rapid fissipary under higher temperatures, with little to no fission at lower temperatures. In an apparent trade-off between reproduction and growth, the higher latitude population showed lower growth potential than those from lower latitudes at all temperatures. Doubling times indicated that a small number of overwintering individuals could effectively recolonize a habitat and reach high observed summer densities. A comprehensive evaluation of D. lineata, framed through the stages of the invasion sequence from donor to recipient regions, revealed that this species employs a remarkable range of strategies to achieve global citizenry: a unique combination of a rare encapsulation tactic (producing a hardened mucous sheath), eurythermal and euryhaline capacity, and asexual reproduction, all help explain the success of one of the world's most euryplastic marine invaders.