Many animals are regarded as relatively sedentary and specialized in marginal parts of their geographical distributions. They are expected to be slow at colonizing new habitats. Despite this, the cool margins of many species' distributions have expanded rapidly in association with recent climate warming. We examined four insect species that have expanded their geographical ranges in Britain over the past 20 years. Here we report that two butterfly species have increased the variety of habitat types that they can colonize, and that two bush cricket species show increased fractions of longer-winged (dispersive) individuals in recently founded populations. Both ecological and evolutionary processes are probably responsible for these changes. Increased habitat breadth and dispersal tendencies have resulted in about 3- to 15-fold increases in expansion rates, allowing these insects to cross habitat disjunctions that would have represented major or complete barriers to dispersal before the expansions started. The emergence of dispersive phenotypes will increase the speed at which species invade new environments, and probably underlies the responses of many species to both past and future climate change.
Groups of animals often need to make communal decisions, for example about which activities to perform, when to perform them and which direction to travel in; however, little is known about how they do so. Here, we model the fitness consequences of two possible decision-making mechanisms: 'despotism' and 'democracy'. We show that under most conditions, the costs to subordinate group members, and to the group as a whole, are considerably higher for despotic than for democratic decisions. Even when the despot is the most experienced group member, it only pays other members to accept its decision when group size is small and the difference in information is large. Democratic decisions are more beneficial primarily because they tend to produce less extreme decisions, rather than because each individual has an influence on the decision per se. Our model suggests that democracy should be widespread and makes quantitative, testable predictions about group decision-making in non-humans.
Conflicting interests among group members are common when making collective decisions, yet failure to achieve consensus can be costly. Under these circumstances individuals may be susceptible to manipulation by a strongly opinionated, or extremist, minority. It has previously been argued, for humans and animals, that social groups containing individuals who are uninformed, or exhibit weak preferences, are particularly vulnerable to such manipulative agents. Here, we use theory and experiment to demonstrate that, for a wide range of conditions, a strongly opinionated minority can dictate group choice, but the presence of uninformed individuals spontaneously inhibits this process, returning control to the numerical majority. Our results emphasize the role of uninformed individuals in achieving democratic consensus amid internal group conflict and informational constraints. S ocial organisms must often achieve a consensus to obtain the benefits of group living and to avoid the costs of indecision (1 12). In some societies, notably those of eu social insects, making consensus decisions is often a unitary, conflict free process because the close relatedness among individuals means that they typically share preferences (11). However, in other social animals, such as schooling fub, flocking birds, herding ungulates, and humans, individual groop members may be oflow relatedness; thus, self interest can play an important role in group decisions. Reaching a consensus decision, there fore, frequently depends on individuals resolving complex conilicts of interest (1 11, 13, 14).There are several means of achieving groop consensus. In some cases, decisions made by one or only a small proportion of the group dictate the behavior of the entire group ( 4 6, 13, 14). There fore, a minority, or even a single individual, has the potential to control or exploit the majority, achieving substantial gains at the expense of other group members (1 6,9,10,14). In contrast, consensus can also be reached throogh demo cratic means, with fuir representation and an out come determined by a plurality. Democratic decisions tend to be more moderate, rninimiz ing group consensus costs, particularly in large animal groops (3). However, in the absence of established procedures such as voting ( 8), it is IDlclear how equal representation is enforced Consequently, for both human socwtJes (1,2,6,9,10,14) and group living animals ( 6, 13), it has been afb'lted that group decisions can be subject to manipulation by a self interested and opinionated minority. In particular, previoos work suggests that groups containing individu als who are uninformed, or naive, about the de cision being made are particularly vulnerable to such manipulation (2,9,10,13). Under this view, IDlinformed individuals destabilize the capacity for collective intelligence in groups (J 0, 14), with poorly informed individuals potentially facilitat ing the establishment of extremist opinions in populations (9,14).Here, we address the question of whether and, if so, under which condit...
Self-organizing-system approaches have shed significant light on the mechanisms underlying synchronized movements by large groups of animals, such as shoals of fish, flocks of birds, or herds of ungulates. However, these approaches rarely consider conflicts of interest between group members, although there is reason to suppose that such conflicts are commonplace. Here, we demonstrate that, where conflicts exist, individual members of self-organizing groups can, in principle, increase their influence on group movement destination by strategically changing simple behavioral parameters (namely, movement speed, assertiveness, and social attraction range). However, they do so at the expense of an increased risk of group fragmentation and a decrease in movement efficiency. We argue that the resulting trade-offs faced by each group member render it likely that group movements are led by those members for which reaching a particular destination is most crucial or group cohesion is least important. We term this phenomenon leading according to "need" or "social indifference," respectively. Both kinds of leading can occur in the absence of knowledge of or communication about the needs of other group members and without the assumption of altruistic cooperation. We discuss our findings in the light of observations on fish and other vertebrates.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.