Statistical method for testing the neutral mutation hypothesis by DNA polymorphism.

Evolutionary adaptation can be rapid and potentially help species counter stressful conditions or realize ecological opportunities arising from climate change. The challenges are to understand when evolution will occur and to identify potential evolutionary winners as well as losers, such as species lacking adaptive capacity living near physiological limits. Evolutionary processes also need to be incorporated into management programmes designed to minimize biodiversity loss under rapid climate change. These challenges can be met through realistic models of evolutionary change linked to experimental data across a range of taxa.

http://www.indiaenvironmentportal.org.in/files/climate%20change_1.pdf

Climate change and evolutionary adaptation

The Human Hippocampus and Spatial and Episodic Memory

In a dynamic world, mechanisms allowing prediction of future situations can provide a selective advantage. We suggest that memory systems differ in the degree of flexibility they offer for anticipatory behavior and put forward a corresponding taxonomy of prospection. The adaptive advantage of any memory system can only lie in what it contributes for future survival. The most flexible is episodic memory, which we suggest is part of a more general faculty of mental time travel that allows us not only to go back in time, but also to foresee, plan, and shape virtually any specific future event. We review comparative studies and find that, in spite of increased research in the area, there is as yet no convincing evidence for mental time travel in nonhuman animals. We submit that mental time travel is not an encapsulated cognitive system, but instead comprises several subsidiary mechanisms. A theater metaphor serves as an analogy for the kind of mechanisms required for effective mental time travel. We propose that future research should consider these mechanisms in addition to direct evidence of future-directed action. We maintain that the emergence of mental time travel in evolution was a crucial step towards our current success.

/pdf/the-evolution-of-foresight-what-is-mental-time-travel-and-is-4i9wwln8os.pdf

The evolution of foresight: What is mental time travel, and is it unique to humans?

The recollection of past experiences allows us to recall what a particular event was, and where and when it occurred, a form of memory that is thought to be unique to humans. It is known, however, that food-storing birds remember the spatial location and contents of their caches. Furthermore, food-storing animals adapt their caching and recovery strategies to the perishability of food stores, which suggests that they are sensitive to temporal factors. Here we show that scrub jays (Aphelocoma coerulescens) remember 'when' food items are stored by allowing them to recover perishable 'wax worms' (wax-moth larvae) and non-perishable peanuts which they had previously cached in visuospatially distinct sites. Jays searched preferentially for fresh wax worms, their favoured food, when allowed to recover them shortly after caching. However, they rapidly learned to avoid searching for worms after a longer interval during which the worms had decayed. The recovery preference of jays demonstrates memory of where and when particular food items were cached, thereby fulfilling the behavioural criteria for episodic-like memory in non-human animals.

Episodic-like memory during cache recovery by scrub jays

"Squirrels of the World", written by scientists with more than 100 years of collective experience studying these popular mammals, is the first comprehensive examination of all 285 species of squirrels worldwide. The authors reveal virtually every detail of the family Sciuridae, which includes ground squirrels, tree squirrels, flying squirrels, prairie dogs, and chipmunks. Each species-from the familiar gray squirrel of American backyards to the exotic and endangered woolly flying squirrel of Pakistan-is described in a detailed account that includes distinguishing characteristics, ecology, natural history, conservation status, and current threats to its existence. "Squirrels of the World" includes: stunning color photographs that document rare and unusual squirrels as well as common varieties; evolution, morphology, ecology, and conservation status; colorful range maps marking species distribution; images of the skull of each genus of squirrel; and extensive references.

Squirrels of the World

Caching decisions by grey squirrels: a test of the handling time and perishability hypotheses

There is now unequivocal evidence for global climate change; however, its potential impacts on evolutionary processes remain unclear. Many species have responded to contemporary climate change through shifts in their geographic range. This could lead to increased sympatry between recently diverged species; likely increasing the potential for hybridization. Recently, following a series of warm winters, southern flying squirrels (Glaucomys volans) in Ontario, Canada rapidly expanded their northern range limit resulting in increased sympatry with the closely related northern flying squirrel (Glaucomys sabrinus). This provided the opportunity to test the prediction that contemporary climate change can act as a catalyst creating conditions for the formation of hybrid zones. Following extensive sampling and molecular analyses (nuclear and mitochondrial DNA), we identified the occurrence of hybridization between sympatric G. sabrinus and G. volans .T here was evidence of backcrossing but not of extensive introgession, consistent with the hypothesis of recent rather than historic hybridization. To our knowledge, this is the first report of hybrid zone formation following a range expansion induced by contemporary climate change. This is also the first report of hybridization between North American flying squirrel species.

Climate change induced hybridization in flying squirrels

-A common assumption in studies of seed predation is that seeds survive attack and are dispersed only 'when animals fail to find seeds, drop undamaged seeds or fail to recover seeds after they are cached. This study, however, suggests that many acorn consumers consistently eat only a portion of the cotyledon of several species of acorns and thereby permit embryo survival. Several vertebrates [gray squirrels (Sciurus carolinensis), common grackles (Quiscalus quiscula) and blue jays (Cyanocita cristata)] were observed to consume only 30-60% of the cotyledon from the basal portion (cap end) of willow oak (Quercus phellos) acorns. Gray squirrels exhibited a similar preference for the basal end of acorns of several other species of red oaks (Q. rubra, Q. laevis, Q. nigra, Q. palustris and Q. coccinea) from a wide geographic region. In addition, acorn weevil larvae (Curculio sp.) were observed significantly (>35%) more often in the basal portion than in the apical end of Q. alba acorns. Chemical analyses of acorns from two tree species revealed that the concentration of protein-precipitable phenolics (primarily tannins) was 12.5% (Q. phellos) and 84.2% (Q. laevis) higher in the apical portion of the seeds where the embryo is located. Moreover, germination experiments revealed equal or greater germination frequencies for partially consumed acorns than for intact acorns. We suggest that the higher tannin levels may render the apical portion less palatable, and thereby increase the probability of embryo survival after attack by seed consumers.

Tannins and partial consumption of acorns: implications for dispersal of oaks by seed predators.

Scatter-hoarding rodents should space food caches to maximize cache recovery rate (to minimize loss to pilferers) relative to the energetic cost of carrying food items greater distances. Optimization models of cache spacing make two predictions. First, spacing of caches should be greater for food items with greater energy content. Second, the mean distance between caches should increase with food abundance. However, the latter prediction fails to account for the effect of food abundance on the behavior of potential pilferers or on the ability of caching individuals to acquire food by means other than recovering their own caches. When considering these factors, shorter cache distances may be predicted in conditions of higher food abundance. We predicted that seed caching distances would be greater for food items of higher energy content and during lower ambient food abundance and that the effect of seed type on cache distance variation would be lower during higher food abundance. We recorded distances moved for 8636 seeds of five seed types at 15 locations in three forested sites in Pennsylvania, USA, and 29 forest fragments in Indiana, USA, across five different years. Seed production was poor in three years and high in two years. Consistent with previous studies, seeds with greater energy content were moved farther than less profitable food items. Seeds were dispersed less far in seed-rich years than in seed-poor years, contrary to predictions of conventional models. Interactions were important, with seed type effects more evident in seed-poor years. These results suggest that, when food is superabundant, optimal cache distances are more strongly determined by minimizing energy cost of caching than by minimizing pilfering rates and that cache loss rates may be more strongly density-dependent in times of low seed abundance.

https://www.jstor.org/stable/pdfplus/27651399.pdf

Michael A. Steele

Papers

Squirrels of the World

Caching decisions by grey squirrels: a test of the handling time and perishability hypotheses

Climate change induced hybridization in flying squirrels

Tannins and partial consumption of acorns: implications for dispersal of oaks by seed predators.

Determinants of seed removal distance by scatter-hoarding rodents in deciduous forests