Anna Kasparson - Profile on Academia.edu (original) (raw)

Papers by Anna Kasparson

Temporal resolution of birth rate analysis in zooplankton and its implications for identifying strong interactions in ecology

Ecology and Evolution

Expanding on Haeckel's classical definition, ecology can be defined as the study of strong an... more Expanding on Haeckel's classical definition, ecology can be defined as the study of strong and weak interactions between the organism and the environment, hence the need for identifying strong interactions as major drivers of population and community dynamics. The solution to this problem is facilitated by the fact that the frequency distribution of interaction strengths is highly skewed, resulting in few or, according to Liebig's law of the minimum, just one strong interaction. However, a single strong interaction often remains elusive. One of the reasons may be that, due to the ever‐present dynamics of ecological systems, a single strong interaction is likely to exist only on relatively short time intervals, so methods with sufficient temporal resolution are required. In this paper, we study the temporal resolution of contribution analysis of birth rate in zooplankton, a method to assess the relative strength of bottom‐up (food) versus top‐down (predation) effects. Birth r...

Interactions between color channels (long-wave (L), middle-wave (M) and short-wave (S)) in the re... more Interactions between color channels (long-wave (L), middle-wave (M) and short-wave (S)) in the receptive ̄eld of direction-selective (DS) and orientation-selective (OS) ganglion cells (GCs) were investigated with combined selective stimulation of pairs of cone types (L andM, L and S, M and S). In the experiments with DS GCs of both ON and OFF types, it was shown that: (1) M and S channels were synergistic relative to each other and opponent to L channel. (2) Three-parameter signal (from L, M and S cones) is transformed to one-parameter signal at the output of DS GC, thus illustrating the principle of univariance. (3) In the experiments with OS GCs, it was shown that L and M channels were synergistic in the OFF-pathway, while the S channel was opponent to them. Our results suggested that photoreceptor synaptic connectivity of the bipolar cells hypothetically involved in the gold ̄sh OS circuitry substantially di®ers from connectivity of bipolar cells presumably targeting DS GC. (4) T...

Updated functional segregation of retinal ganglion cell projections in the tectum of a cyprinid fish—further elaboration based on microelectrode recordings

Fish Physiology and Biochemistry

Assessing the relative strength of the effects of food resources and predators on a population: A review of methods

Biology Bulletin Reviews

Journal of Integrative Neuroscience, 2014

Responses of direction-selective and orientation-selective motion detectors were recorded extrace... more Responses of direction-selective and orientation-selective motion detectors were recorded extracellularly from the axon terminals of ganglion cells in the super¯cial layers of the tectum opticum of immobilized gold¯sh, Carassius gibelio (Bloch, 1782). Color stripes or edges moving on some color background (presented on the CRT monitor with known emission spectra of its phosphors) served as stimuli. It was shown that stimuli of any color can be more or less matched with the background by varying their intensities what is indicative of color blindness of the motion detectors. Sets of stimuli which matched the background proved to represent planes in the three-dimensional color space of the gold¯sh. A relative contribution of di®erent types of cones to the spectral sensitivity was estimated according to orientation of the plane of color matches. The spectral sensitivity of any motion detector was shown to be determined mainly by long-wave cones with a weak negative (opponent) contributions of middle-wave and/or short-wave ones. This resulted in reduced sensitivity in the blue-green end of the spectrum, what may be considered as an adaptation to the aquatic environment where, because of the substantial light scattering of a blue-green light, acute vision is possible only in a red region of the spectrum.

Proceedings of the Royal Society B: Biological Sciences, 2013

The results of early studies on colour vision in dogs led to the conclusion that chromatic cues a... more The results of early studies on colour vision in dogs led to the conclusion that chromatic cues are unimportant for dogs during their normal activities. Nevertheless, the canine retina possesses two cone types which provide at least the potential for colour vision. Recently, experiments controlling for the brightness information in visual stimuli demonstrated that dogs have the ability to perform chromatic discrimination. Here, we show that for eight previously untrained dogs colour proved to be more informative than brightness when choosing between visual stimuli differing both in brightness and chromaticity. Although brightness could have been used by the dogs in our experiments (unlike previous studies), it was not. Our results demonstrate that under natural photopic lighting conditions colour information may be predominant even for animals that possess only two spectral types of cone photoreceptors.

Allee effects and the spatial dynamics of a locally endangered butterfly, the high brown fritillary ( Argynnis adippe )

Ecological Applications, 2014

Conservation of endangered species necessitates a full appreciation of the ecological processes a... more Conservation of endangered species necessitates a full appreciation of the ecological processes affecting the regulation, limitation, and persistence of populations. These processes are influenced by birth, death, and dispersal events, and characterizing them requires careful accounting of both the deterministic and stochastic processes operating at both local and regional population levels. We combined ecological theory and observations on Allee effects by linking mathematical analysis and the spatial and temporal population dynamics patterns of a highly endangered butterfly, the high brown fritillary, Argynnis adippe. Our theoretical analysis showed that the role of density-dependent feedbacks in the presence of local immigration can influence the strength of Allee effects. Linking this theory to the analysis of the population data revealed strong evidence for both negative density dependence and Allee effects at the landscape or regional scale. These regional dynamics are predicted to be highly influenced by immigration. Using a Bayesian state-space approach, we characterized the local-scale births, deaths, and dispersal effects together with measurement and process uncertainty in the metapopulation. Some form of an Allee effect influenced almost three-quarters of these local populations. Our joint analysis of the deterministic and stochastic dynamics suggests that a conservation priority for this species would be to increase resource availability in currently occupied and, more importantly, in unoccupied sites.

Archives of Biological Sciences, 2009

The optic tectum or superior colliculus processes image motion and takes part in orienting respon... more The optic tectum or superior colliculus processes image motion and takes part in orienting responses revealed in rapid eye, head, and/or body movemements. This function can proceed without taking into account information about color, and the superior colliculus in mammals is color-blind . In the frog, the system carrying chromatic information also originates as a channel separate from the tectal pathway, providing the main information needed for the frog's reactions to moving objects . Color blindness of movement detectors projecting to the fish tectum was proved in color-matching experiments for both orientation-selective and direction-selective (Maximova et al., 2005) units. Recent experiments using selective stimulation of different cone types revealed new features of these projections.