Implications of Dietary Variation on Abundance and Occupancy Relationships in a Predominantly Muroid Small Mammal Community in Mpala Conservancy, Kenya

Abstract

Positive interspecific relationship between abundance and occupancy (AOR) is among the most common patterns in ecology. This has been attributed to niche differences among species such that resource generalists are expected to be abundant and widespread compared to resource specialists (the Resource Breadth Hypothesis). Studies that have tested this hypothesis have failed in ascribing mechanisms because of using datasets across broad spatial scale. However, this hypothesis is better tested at a local scale for individuals to be tracked through time based on prevailing resources. This study sought to establish AOR and the driving mechanisms for the AOR in a predominantly muroid small mammal community in Mpala Conservancy. The Resource Breadth Hypothesis and the underlaying mechanisms as predicted by the Niche Variation Hypothesis were tested. The study predicted that dietary generalists will be the most abundant and widespread species, and ones exhibiting the greatest among individual dietary variation (a prediction of the Niche Variation Hypothesis) as compared to dietary specialists. Abundance and occupancy were estimated from mark-recapture data by fitting N-mixture and single season occupancy models. The degree of dietary generalism and among individual dietary variation was estimated from sequenced plant DNA of fecal samples based on Shannon-Weaver diversity and proportional-similarity indexes. Occupancy increased with increase in abundance (r = .87), and both the Resource Breadth and Niche Variation Hypotheses were supported after fitting simple linear regressions across species. Overall regression for the test of these hypotheses were both statistically significant (ANOVA: F1,3 = 27.44, p = 0.01, regression: R2 = 0.87 and F1,3 = 17.30, p = 0.03, R2 = 0.80 respectively). Results indicate that the Niche Variation Hypothesis provides the mechanism by which the Resource Breadth Hypothesis explains the positive interspecific AOR, suggesting the need to account for individual differences when examining the drivers of abundance and distribution of species.