Ecological Conditions Favoring Budding in Colonial Organisms under Environmental Disturbance

Abstract

Dispersal is a topic of great interest in ecology. Many organisms adopt one of two distinct dispersal tactics at reproduction: the production of small offspring that can disperse over long distances (such as seeds and spawned eggs), or budding. The latter is observed in some colonial organisms, such as clonal plants, corals and ants, in which (super)organisms split their body into components of relatively large size that disperse to a short distance. Contrary to the common dispersal viewpoint, short-dispersal colonial organisms often flourish even in environments with frequent disturbances. In this paper, we investigate the conditions that favor budding over long-distance dispersal of small offspring, focusing on the life history of the colony growth and the colony division ratio. These conditions are the relatively high mortality of very small colonies, logistic growth, the ability of dispersers to peacefully seek and settle unoccupied spaces, and small spatial scale of environmental disturbance. If these conditions hold, budding is advantageous even when environmental disturbance is frequent. These results suggest that the demography or life history of the colony underlies the behaviors of the colonial organisms.

The evolution of group dispersal with leaders and followers

“…It is standard in mathematical models to assume that dispersal occurs independently, but in many species dispersal occurs in groups of individuals that are often but not always related, and group dispersal is frequently initiated by a subset of individuals (Schoof et al, 2009;Wikberg, 2012;Nichols et al, 2012;Yano, 2008;Berg et al, 2009;Mumme et al, 1988;Lewis et al, 2011;Andersson and Wallander, 2004). The few models that incorporate the concept of group dispersal do not examine the emergence or maintenance of this biological phenomenon, nor do they assume the presence of leader-follower relationships (Gardner and West, 2006;Gardner et al, 2009;Nakamaru et al, 2014).…”

Life-history evolution in ants: the case ofCardiocondyla

“…Life-history theory of social insects is still far from complete and often relies on verbal arguments [32][33][34][35][36][37]. Detailed ecological and population genetic models, such as [38,39], are needed. In the next paragraphs, I first give an overview on evolutionary pathways concerning queen numbers and male reproductive tactics and try to explain the observed patterns with present ideas about social evolution in ants.…”

“…[33,38,39]). Instead, facultative polygyny and colony founding by budding appear to be ancestral traits in Cardiocondyla.…”

“…B 284: 20161406 queens and the abundance of ephemeral nest sites in the ground, hollow branches or grass stems in the rainforests of Southeast Asia and Wallacea (e.g. [33,38,39]). Queen antagonism has not been observed in these polygynous species, even though queen number negatively affects the fitness of individual queens by lowering their egg-laying rate and shortening their lifespan [42].…”

“…In social Hymenoptera, polygyny is thought to be a derived trait [40] that evolved whenever environmental conditions promoted large colony size [32] or facilitated colony propagation by fragmentation of the natal colony and the dispersal of groups of workers and queens ('budding' e.g. [33,38,39]). Instead, facultative polygyny and colony founding by budding appear to be ancestral traits in Cardiocondyla.…”