Scale Resonance: Effects of spatial scales on the inference of drivers behind species distribution

Atuhaire, Fatumah (2017-12)

Thesis (MSc)--Stellenbosch University, 2017.

Thesis

ENGLISH ABSTRACT: The factors that determine species distributions across landscapes have for long served keen interest to conservation biology. Abiotic factors have been the major determinants of species distribution at larger scales whereas biotic factors have been considered to be at small scales. The effect of a factor at one scale cannot be extrapolated to other scales. So to understand these effects,we need to make comparisons at multiple scales. Although there has been several progressive research studies done on the effects of spatial scales on species distributions, empirical studies involving varying more than one factor have been lacking. I develop a model that uses two factors of growth rate and carrying capacity as the key drivers of species distribution in a landscape. Each factor here has its own spatial autocorrelation and species’ responses to these factors vary as the spatial scales increase from local to regional to global scales. I represent these factors as two fractal landscapes and implement an integro difference equation (IDE) on them. The results obtained tell us how the population density is dependant on the growth rate and carrying capacity. Keywords: Spatial scale; fractal landscape; spatial autocorrelation; integro difference equations; hierarchical partitioning.

AFRIKAANSE OPSOMMING: Die faktore wat die verspreiding van spisies oor landskappe bepaal, was vir lank ’n belangstelling van bewaringsbiologie. Abiotiese faktore beïnvloed hierdie verspreiding op die groot skaal, terwyl biotiese faktore vir die kleiner skaal in ag geneem moet word. Die effek van ’n faktor by een skaal kan nie geëkstrapoleer word na ’n ander skaal nie, so om hierdie effekte te verstaan, moet ons hulle op verskeie skale vergelyk. Alhoewel daar ’n hele paar progressiewe navorsingstudies oor die uitwerking van ruimtelike skale op die verspreding van spesies gedoen is, ontbreek ’n empiriese studie waar meer as een faktor op ’n slag verander word. Ek ontwikkel ’n model wat die twee faktore van groeikoers en drakrag gebruik as die sleutelbestuurders van die verspreiding van spesies in ’n landskap. Elke faktor het hier sy eie outo-korrelasie en spesies se antwoorde tot hierdie faktore wissel soos die ruimtelike skale van plaaslik na streek na globaal vergroot. Ek stel hierdie faktore as twee landskappe voor en implenmenteer ’n integro versil (Eng. IDE) model op hulle. Die resultsate wat verkry word, vertel ons hoe die bevolkingsdigtheid afhanklik is van die groeitempo en drakrag. Ruimtelike skaal; fraktale landskap; ruimtelike outokorrelasie; integro verskilvergelykings; hiërargiese verdeling.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/102574
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