Habitat-Specific Morphological Variation among Threespine Sticklebacks (Gasterosteus aculeatus) within a Drainage Basin

Habitat-specific morphological variation, often corresponding to resource specialization, is well documented in freshwater fishes. In this study we used landmark based morphometric analyses to investigate morphological variation among threespine sticklebacks (Gasterosteus aculeatus L.) from four interconnected habitat types within a single lowland drainage basin in eastern England. These included the upper and lower reaches of the river, the estuary, a connected ditch network and a coastal salt marsh. We found significant habitat-specific differences in morphology, with three axes of variation describing differences in orbit diameter, body depth, caudal peduncle shape and pectoral fin positioning as well as variation in relative dorsal and pelvic spine size. Interestingly, the ditch system, an artificial and heavily managed habitat, is populated by sticklebacks with a characteristic morphology, suggesting that human management of habitats can in some circumstances lead to morphological variation among the animals that inhabit them. We discuss the mechanisms that conceivably underlie the observed morphological variation and the further work necessary to identify them. Finally, we consider the implications of habitat-specific body shape variation for the behavioural ecology of this ecologically generalist species

Investigations into stickleback social learning

The objective of the experiments contained within this thesis was to provide further insight into the social learning capabilities of threespined sticklebacks and the factors affecting the transmission of information through populations. There are a number of previous studies which provide evidence that both threespined and ninespined sticklebacks possess the ability to learn socially under a range of contexts, such as foraging, anti-predator behaviour, mate choice, and cooperation. The studies presented in this thesis aim to extend this knowledge and shed light on the social learning processes used. Evidence was found to support previous opinion that threespined sticklebacks are capable of using a number of social learning processes, including local enhancement, stimulus enhancement, and the social enhancement of food preferences. However, therewas no evidence to suggest that either threespined or ninespined sticklebacks are capable of using the social learning process of delayed local enhancement under a shelter choice context, a process which both species have previously been shown to use under a foraging context. This thesis also explores the effect of the social network within shoals of threespined sticklebacks upon the transmission of novel foraging information. It was discovered that both prior association preferences and prior diet have an effect on the order in which individuals discover a novel foraging task

Social learning in fish

Social learning is known to be a common phenomenon in fish, which they utilise under many different contexts, including foraging, mate-choice and migration. Here I review the literature on social learning in fish and present two studies. The first examines the ability of threespined sticklebacks to use social learning in the enhancement of food preferences. The second study examines the ability of both threespined sticklebacks and ninespined sticklebacks to use social learning in the avoidance of predators

Data from: Environmental complexity influences association network structure and network-based diffusion of foraging information in fish shoals

Socially transmitted information can significantly affect the ways in which animals interact with their environments. We used network-based diffusion analysis, a novel and powerful tool for exploring information transmission, to model the rate at which sticklebacks (Gasterosteus aculeatus) discovered prey patches, comparing shoals foraging in open and structured environments. We found that for groups in the open environment, individuals tended to recruit to both the prey patch and empty comparison patches at similar times, suggesting that patch discovery was not greatly affected by direct social transmission. In contrast, in structured environments we found strong evidence that information about prey patch location was socially transmitted and moreover that the pathway of information transmission followed the shoals’ association network structures. Our findings highlight the importance of considering habitat structure when investigating the diffusion of information through populations and imply that association networks take on greater ecological significance in structured than open environments

Environmental complexity influences association network structure and network-based diffusion of foraging information in fish shoals

Socially transmitted information can significantly affect the ways in which animals interact with their environments. We used network-based diffusion analysis, a novel and powerful tool for exploring information transmission, to model the rate at which sticklebacks (Gasterosteus aculeatus) discovered prey patches, comparing shoals foraging in open and structured environments. We found that for groups in the open environment, individuals tended to recruit to both the prey patch and empty comparison patches at similar times, suggesting that patch discovery was not greatly affected by direct social transmission. In contrast, in structured environments we found strong evidence that information about prey patch location was socially transmitted and moreover that the pathway of information transmission followed the shoals' association network structures. Our findings highlight the importance of considering habitat structure when investigating the diffusion of information through populations and imply that association networks take on greater ecological significance in structured than open environments.</p

Data from: Environmental complexity influences association network structure and network-based diffusion of foraging information in fish shoals

Socially transmitted information can significantly affect the ways in which animals interact with their environments. We used network-based diffusion analysis, a novel and powerful tool for exploring information transmission, to model the rate at which sticklebacks (Gasterosteus aculeatus) discovered prey patches, comparing shoals foraging in open and structured environments. We found that for groups in the open environment, individuals tended to recruit to both the prey patch and empty comparison patches at similar times, suggesting that patch discovery was not greatly affected by direct social transmission. In contrast, in structured environments we found strong evidence that information about prey patch location was socially transmitted and moreover that the pathway of information transmission followed the shoals’ association network structures. Our findings highlight the importance of considering habitat structure when investigating the diffusion of information through populations and imply that association networks take on greater ecological significance in structured than open environments

Webster et al. NBDA_Am Nat

Part 1: Association matrices used to compare association network structure in open and structured environments.Part 2a: Association matrices used to compare association network structure in open and structured environments for diffusion analysis. Part 2b: Prey and control patch entry times and orders, used in diffusion analysis

Plots showing consistency of landmark location.

<p>In order to confirm that landmarks could be identified precisely and consistently, both within and between samples, we repeatedly digitised landmarks on the same images. Five images were selected at random. For each image, the same 20 landmarks were digitised each day, for five consecutive days (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0021060#s2" target="_blank">Methods</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0021060#pone-0021060-g001" target="_blank">Figure 1</a> for discussion of the landmark selection criteria). The order in which each image was landmarked was randomised for each day. Landmark locations for days 1 to 5 are represented by blue, red, yellow, purple and black markers respectively. Each image represents a fish 36–40 mm in length.</p