Can associative learning be the general process for intelligent behavior in non-human animals?

The general process- and adaptive specialization hypotheses represent two contrasting explanations for understanding intelligence in non-human animals. The general process hypothesis proposes that associative learning underlies all learning, whereas the adaptive specialization hypothesis suggests additional distinct learning processes required for intelligent behavior. Here, we use a selection of experimental paradigms commonly used in comparative cognition to explore these hypotheses. We tested if a novel computational model of associative learning --- A-learning --- could solve the problems presented in these tests. Results show that this formulation of associative learning suffices as a mechanism for general animal intelligence, without the need for adaptive specialization, as long as adequate motor- and perceptual systems are there to support learning. In one of the tests, however, the addition of a short-term trace memory was required for A-learning to solve that particular task. We further provide a case study showcasing the flexibility, and lack thereof, of associative learning, when looking into potential learning of self-control and the development of behavior sequences. From these simulations we conclude that the challenges do not so much involve the complexity of a learning mechanism, but instead lie in the development of motor- and perceptual systems, and internal factors that motivate agents to explore environments with some precision, characteristics of animals that have been fine-tuned by evolution for million of years.

Intraspecific divergence and convergence of floral tube length in specialized pollination interactions

Floral tubes are often thought to be a consequence of adaptive specialization towards pollinator morphology. We explore floral tube length evolution within Tritoniopsis revoluta (Iridaceae), a species with considerable geographical tube length variation. We ask whether tube lengths of T. revoluta populations are associated with pollinator proboscis lengths, whether floral divergence occurs in the presence of different pollinators and whether floral convergence occurs between distantly related populations pollinated by the same pollinator. Finally, we ask whether tube length evolution is directional. Shifts between morphologically different pollinators were always associated with shifts in floral morphology, even when populations were very closely related. Distantly related populations had similar tube lengths when they were pollinated by the same pollinator. Shifts in tube length tended to be from short to long, although reversals were not infrequent. After correcting for the population-level phylogeny, there was a strong positive, linear relationship between floral tube length and pollinator proboscis length, suggesting that plants are functionally specialized on different pollinators at different sites. However, because tube length evolution in this system can be a bidirectional process, specialization to the local pollinator fauna is unlikely to result in evolutionary or ecological dead-ends such as canalization or range limitation.

Low allozyme heterozygosity in North Pacific and Bering Sea populations of red king crab (Paralithodes camtschaticus): adaptive specialization, population bottleneck, or metapopulation structure?

Grant, W. S., Merkouris, S. E., Kruse, G. H., and Seeb, L. W. 2011. Low allozyme heterozygosity in North Pacific and Bering Sea populations of red king crab (Paralithodes camtschaticus): adaptive specialization, population bottleneck, or metapopulation structure? – ICES Journal of Marine Science, 68: . Populations of red king crab in the North Pacific and Bering Sea have declined in response to ocean-climate shifts and to harvesting. An understanding of how populations are geographically structured is important to the management of these depressed resources. Here, the Mendelian variability at 38 enzyme-encoding loci was surveyed in 27 samples (n = 2427) from 18 general locations. Sample heterozygosities were low, averaging HE = 0.015 among samples. Weak genetic structure was detected among three groups of populations, the Bering Sea, central Gulf of Alaska, and Southeast Alaska, but without significant isolation by distance among populations. A sample from Adak Island in the western Aleutians was genetically different from the remaining samples. The lack of differentiation among populations within regions may, in part, be due to post-glacial expansions and a lack of migration-drift equilibrium and to limited statistical power imposed by low levels of polymorphism. Departures from neutrality may reflect the effects of both selective and historical factors. The low allozyme diversity in red king crab may, in part, be attributable to adaptive specialization, background selection, ice-age population bottlenecks, or metapopulation dynamics in a climatically unstable North Pacific.

Is bigger always better? A critical appraisal of the use of volumetric analysis in the study of the hippocampus

A well-developed spatial memory is important for many animals, but appears especially important for scatter-hoarding species. Consequently, the scatter-hoarding system provides an excellent paradigm in which to study the integrative aspects of memory use within an ecological and evolutionary framework. One of the main tenets of this paradigm is that selection for enhanced spatial memory for cache locations should specialize the brain areas involved in memory. One such brain area is the hippocampus (Hp). Many studies have examined this adaptive specialization hypothesis, typically relating spatial memory to Hp volume. However, it is unclear how the volume of the Hp is related to its function for spatial memory. Thus, the goal of this article is to evaluate volume as a main measurement of the degree of morphological and physiological adaptation of the Hp as it relates to memory. We will briefly review the evidence for the specialization of memory in food-hoarding animals and discuss the philosophy behind volume as the main currency. We will then examine the problems associated with this approach, attempting to understand the advantages and limitations of using volume and discuss alternatives that might yield more specific hypotheses. Overall, there is strong evidence that the Hp is involved in the specialization of spatial memory in scatter-hoarding animals. However, volume may be only a coarse proxy for more relevant and subtle changes in the structure of the brain underlying changes in behaviour. To better understand the nature of this brain/memory relationship, we suggest focusing on more specific and relevant features of the Hp, such as the number or size of neurons, variation in connectivity depending on dendritic and axonal arborization and the number of synapses. These should generate more specific hypotheses derived from a solid theoretical background and should provide a better understanding of both neural mechanisms of memory and their evolution.