Can models of presence-absence be used to scale abundance? Two case studies considering extremes in life history

摘要: Understanding patterns of species occurrence and abundance is a central theme ecology, natural resource management, conservation. Although models have been widely used for describing distribution, particularly rare species, are less common, despite greater information conservation management. Because presence-absence data easier expensive to collect, predictions from could prove useful. We examined the relationship between two with very different life histories: bracken fern Pteridium aquilinum moose Alces alces. predicted that if were functionally related we should observe: 1) correlation probability observed abundance; 2) similar environmental covariates estimated coefficients developed separately low-density, high-density, global sites; 3) parallel components zero-inflated count models. Probability was not correlated abundance-when-present fern, while evidence apparent at densities animals below 7 individuals per cutblock. Coefficients levels density did vary significantly. However, once accounted for, measured appeared important in abundance. For bracken, differed their expression Differences extreme moose; however, results two-process suggest distribution may be function processes. Environmental factors influencing differ those limiting distribution. Life history, scale, site socio-competitive processes further help shape Two-stage modeling provides powerful tool animal plant where influenced by factors.