Null model analysis of spatial species associations in spruce, tree line and dwarf-pine bird assemblages in the High Tatras, the Western Carpathians

Abstract

Jared Diamond proposed several assembly rules based on the assumption of competitive interactions among
species. The first Diamond’s rule proposes that communities are formed of certain permissible combinations of
species that can co-exist. The fifth assembly rule states that some pairs of species never co-occur, forming so
called “checkerboard” or complementary distributions. The objective of this study was to test these propositions
on spruce, tree-line and dwarf-pine bird assemblages censused by the fixed radius point count method in the
High Tatras, Slovakia. The null model simulations yielded no clear assembly patterns. The binary null models
had tendency toward random associations, while quantitative null models suggested segregations. Presence/
absence null models showed tendency toward random associations in post-breeding and breeding spruce
bird assemblages, while quantitative null models yielded half random and half segregations in post-breeding
season and all types of associations were detected during the breeding with slight prevalence of segregation.
All binary tests indicated random associations in the post-breeding bird assemblages in the upper tree line
and dwarf pine communities, whereas quantitative models showed prevalence of segregation. Binary models
indicated slight prevalence of random associations in the breeding bird assemblages of the upper tree line and
dwarf pine communities from territorial records and prevalence of segregation from all records. Quantitative
models did not show consistent results in these habitat types detecting prevalence of segregations. In summary,
the first Diamond’s rule was not supported due to random patterns of unique species combinations and the fifth
rule was supported partly by quantitative null model analyses.