How to Measure Group Selection in Real-world Populations

Multilevel selection and the evolution of cooperation are fundamental to the formation of higher-level organisation and the evolution of biocomplexity, but such notions are controversial and poorly understood in natural populations. The theoretic principles of group selection are well developed in idealised models where a population is neatly divided into multiple semi-isolated sub-populations. But since such models can be explained by individual selection given the localised frequency-dependent effects involved, some argue that the group selection concepts offered are, even in the idealised case, redundant and that in natural conditions where groups are not well-defined that a group selection framework is entirely inapplicable. This does not necessarily mean, however, that a natural population is not subject to some interesting localised frequency-dependent effects – but how could we formally quantify this under realistic conditions? Here we focus on the presence of a Simpson’s Paradox where, although the local proportion of cooperators decreases at all locations, the global proportion of cooperators increases. We illustrate this principle in a simple individual-based model of bacterial biofilm growth and discuss various complicating factors in moving from theory to practice of measuring group selection

Brain structural connectivity and neurodevelopment in post-Fontan adolescents

Congenital heart disease (CHD) is the most common congenital anomaly, with single ventricle (SV) defects accounting for nearly 10% of all CHD. SV defects tend to be the most severe forms of CHD: all patients born with SV require multiple open heart surgeries, often beginning in the neonatal period, ultimately leading to the Fontan procedure. Due to improvements in surgical procedures and medical care, more patients are surviving into adolescence and adulthood. Brain imaging and pathology studies have shown that patients with SV have differences in brain structure and metabolism even before the first surgery, and as early as in utero. Furthermore, a significant number of patients have new or more severe lesions after the initial surgery, and many still have brain abnormalities into early childhood. However, there are no detailed brain structural data of SV patients in adolescence. Our group recruited a large cohort of post-Fontan SV patients aged 10-19 years. Separate analyses of neuropsychological and behavioral outcomes in these patients show deficits in multiple areas of cognition, increased rates of attention deficit-hyperactivity disorder (ADHD), and increased use of remedial and/or special education services compared to a control group. Post-Fontan adolescents have more gross brain abnormalities, including evidence of chronic ischemic stroke. Furthermore, there are widespread reductions in cortical and subcortical gray matter volume and cortical thickness, some of which are associated with medical and surgical variables. Diffusion tensor imaging (DTI) analyses show widespread areas of altered white matter microstructure in deep subcortical and cerebellar white matter. In this dissertation, I use graph theory methods to characterize structural connectivity based on gray matter (cortical thickness covariance) and white matter (DTI tractography), and examine associations between brain structure and neurodevelopment. I found that brain network connectivity differs in post-Fontan patients compared with controls, both at the global and regional level. Additionally, deficits in overall network structure were associated with impaired neurodevelopment in several domains, including general intelligence, executive function, and visuospatial skills. These data suggest that early neuroprotection should be a major focus in the care of SV patients, with the goal of improving long-term neurodevelopmental outcomes

Rhythms of Locomotion Expressed by Limulus polyphemus, the American Horseshoe Crab: II. Relationship to Circadian Rhythms of Visual Sensitivity

In the laboratory, horseshoe crabs express a circadian rhythm of visual sensitivity as well as daily and circatidal rhythms of locomotion. The major goal of this investigation was to determine whether the circadian clock underlying changes in visual sensitivity also modulates locomotion. To address this question, we developed a method for simultaneously recording changes in visual sensitivity and locomotion. Although every animal (24) expressed consistent circadian rhythms of visual sensitivity, rhythms of locomotion were more variable: 44% expressed a tidal rhythm, 28% were most active at night, and the rest lacked statistically significant rhythms. When exposed to artificial tides, 8 of 16 animals expressed circatidal rhythms of locomotion that continued after tidal cycles were stopped. However, rhythms of visual sensitivity remained stable and showed no tendency to be influenced by the imposed tides or locomotor activity. These results indicate that horseshoe crabs possess at least two biological clocks: one circadian clock primarily used for modulating visual sensitivity, and one or more clocks that control patterns of locomotion. This arrangement allows horseshoe crabs to see quite well while mating during both daytime and nighttime high tides

Multi-epoch infrared photometry of the star forming region G173.58+2.45

We present a multi-epoch infrared photometric study of the intermediate-mass star forming region G173.58+2.45. Photometric observations are obtained using the near-infrared $JHKL'M'$ filters and narrow-band filters centered at the wavelengths of H$_2$ (1-0) S(1) (2.122 $\mu$m) and [FeII] (1.644 $\mu$m) lines. The H$_2$ image shows molecular emission from shocked gas, implying the presence of multiple star formation and associated outflow activity. We see evidence for several collimated outflows. The most extended jet is at least 0.25 pc in length and has a collimation factor of $\sim$ 10, which may be associated with a binary system within the central cluster, resolved for the first time here. This outflow is found to be episodic; probably occurring or getting enhanced during the periastron passage of the binary. We also find that the variable star in the vicinity of the outflow source, which was known as a FU Ori type star, is probably not a FU Ori object. However, it does drive a spectacular outflow and the variability is likely to be related to accretion, when large clouds of gas and dust spiral in towards the central source. Many other convincing accretion-outflow systems and YSO candidates are discovered in the field.Comment: 15 pages, 9 figures, accepted for publication in MNRA

Rhythms of Locomotion Expressed by Limulus polyphemus, the American Horseshoe Crab: I. Synchronization by Artificial Tides

Limulus polyphemus, the American horseshoe crab, has an endogenous clock that drives circatidal rhythms of locomotor activity. In this study, we examined the ability of artificial tides to entrain the locomotor rhythms of Limulus in the laboratory. In experiments one and two, the activity of 16 individuals of L. polyphemus was monitored with activity boxes and “running wheels.” When the crabs were exposed to artificial tides created by changes in water depth, circatidal rhythms were observed in animals exposed to 12.4-h “tidal” cycles of either water depth changes (8 of 8 animals) or inundation (7 of 8 animals). In experiment three, an additional 8 animals were exposed to water depth changes under cyclic conditions of light and dark and then monitored for 10 days with no imposed artificial tides. Most animals (5) clearly synchronized their activity to the imposed artificial tidal cycles, and 3 of these animals showed clear evidence of entrainment after the artificial tides were terminated. Overall, these results demonstrate that the endogenous tidal clock that influences locomotion in Limulus can be entrained by imposed artificial tides. In the laboratory, these tidal cues override the influence of light/dark cycles. In their natural habitat, where both tidal and photoperiod inputs are typically always present, their activity rhythms are likely to be much more complex

The feeding ecology of the European otter (lutra lutra l.) in a marine environment

The bulk of the research took place on the coast of Fetlar, Shetland, in1976-78.Otters were studied by direct observation of individuals recognised by variations in natural markings on the lips and throat, and in addition their diet was studied by means of spraint (faecal) analysis. Most foraging occurred in the sea within 150 m of the shore, a wide variety of fish species being eaten, the majority demersal, as well as some crabs. The pronounced seasonal) variation in dietary composition is considered in the light of available information on the behaviour of the prey species. Detailed observations of an adult female and her cub revealed a significant difference in the composition of their diets, the cub taking a lower proportion of the faster prey species as well as a significant number of crabs which were not predated at all by the adult. Most feeding was localised in bouts in relatively restricted areas. There was no clear correlation between otter activity and the diel or tidal cycles. The adult female and her cub had a home range consisting of 2.5km of coastline with a maximum foraging area of 42.6ha, and their pattern of use of this home range is described. Evidence suggests that for the effective exploitation of foraging areas, breeding females require holt sites (resting places) close by. In 1977 the minimum population density along 11km of coast was 1 otter: 1,2km of coast; and in 1978 along 16km of coast was 1 otter: 0.9km of coast. A positive correlation between dive duration and water depth was noted and it is hypothesised that this is a causal relationship determined by the necessity for minimising the up thrust produced by the air in the lungs during diving. The implications of this for otter foraging behaviour and population distribution are discussed