DOI: 10.5061/dryad.79v0d8r
title: Data from: Specialization and niche overlap across spatial scales: revealing ecological factors shaping species richness and coexistence in Australian songbirds

description: 1. Ecological specialization enables the partitioning of resources and
 thus can facilitate the coexistence of species and promote higher species
 richness. Specialization and niche partitioning are expected to exert a
 decisive influence on local spatial scales, while species richness at
 regional scales should be shaped mostly by historical factors and abiotic
 conditions. Moreover, specialization is expected to be particularly
 important in communities that are exceptionally species rich for their
 environmental conditions. Concurrently, niche overlap in these communities
 should be minimized to enable species coexistence. 2. We tested these
 hypotheses by studying specialization-richness relationship and niche
 overlap in assemblages of 298 species of songbirds (Passeriformes) across
 Australia. We used local (2-6 ha) to regional (bioregions) spatial scales,
 and detailed data on habitat, diet, and foraging behaviour (method,
 substrate, and stratum). 3. We expected the richness-specialization
 relationship to be particularly strong i) on local spatial scales and ii)
 in communities exceptionally species rich for given environmental
 conditions (approximated by moisture and vegetation complexity). We also
 expected iii) low niche overlap in assemblages with specialized species.
 4. Only the third prediction was partly supported. First, while the
 specialization and species richness were often positively related, the
 strength and the direction of the relationship changed between traits and
 across spatial scales. The strength of the specialization-richness
 relationship was consistently positive only in foraging stratum, and it
 increased towards smaller spatial scales only in case of habitat and diet.
 Simultaneously, species in local communities demonstrated high overlap in
 habitat and diet. Second, we did not find particularly strong
 specialization-richness relationships in exceptionally species rich
 communities. Third, we found the expected negative relationship between
 specialization and overlap in foraging stratum and substrate (in local
 communities), suggesting that species partition ecological space locally
 in terms of where they find food. 5. Our expectations were only weakly
 supported. Specialization on foraging stratum was probably important in
 facilitating species co-existence. Conversely, although species were often
 specialized on habitat and diet, high overlap in these traits did not
 preclude their local coexistence. Overall, specialization and overlap in
 foraging traits were more important for species coexistence than habitat
 or diet.
description: Full dataset of habitat,
 diet, and foraging behaviour traits used for computation of specialization
 of Australian passerines.Traits for 308 species
 of Australian passerines include type of habitat, diet, foraging method,
 foraging stratum, and foraging substrate. Each trait is divided into
 several categories and each category of each trait has a value
 corresponding to proportional use (percentage) of that category by a given
 species based on information in HANZAB. The sum of all categories of a
 given trait for a given species is always 100.Harmackova_et-al_Specialization_data.xlsx