High functional diversity of avian breeders of the mammoth steppe during the last glacial maximum

Abstract

The largest continuous ecosystem was presented by the mammoth steppe during the Pleistocene, which exhibited high primary productivity and plant diversities creating a diverse set of habitats. This work is the first investigation where I aimed to analyse the functional diversity of bird species predicted to breed at the Last Glacial Maximum (LGM) within the Eurasian part of the mammoth steppe, in comparison to present-day metrics calculated for the same spatial region. To do so, I performed Species Distribution modelling of the breeding ranges of birds distributed in Eurasia and projected the breeding ranges backward to the LGM. Next, I computed functional diversity metrics with and without phylogenetic control for both LGM and present timescales and analysed relationships among functional diversity metrics calculated for the LGM and modern times.I found that i) although the total number of species of birds at the LGM is far less than during present conditions within the same zone, species richness values are predicted to be similar; ii) the distribution ranges of birds breeding within the mammoth steppe zone are governed by annual mean temperature, temperature seasonality, minimum temperature of the coldest month and the mean temperature of the wettest quarter; iii) with the exception of function richness, all descriptors of functional diversity showed significantly higher values during the LGM than those calculated for the present; iv) the observed correlation between co-occurrence and phylogenetic distance was found to be significant during present timescales but showed non-significant relationships on LGM timescales; v) all descriptors of phylogenetic species diversity differed significantly between present and LGM timescales.