Spatial patterns of woody plant and bird diversity: functional relationships or environmental effects

• Published in: Global ecology and biogeography Vol. 17; no. 3; pp. 327 - 339
• Main Authors: Kissling, W. Daniel, Field, Richard, Böhning-Gaese, Katrin
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.05.2008; Blackwell Publishing Ltd; Blackwell Publishing; Blackwell
• Subjects: Animal and plant ecology; animal ecology; Animal, plant and microbial ecology; Animals; Autocorrelation; Autoregressive model; Aves; biodiversity; Biogeography; Biological and medical sciences; Birds; Climate change; climatic factors; community assembly; cross-taxon congruence; Environmental effects; environmental impact; environmental models; equations; feeding preferences; frugivory; Fundamental and applied biological sciences. Psychology; General aspects; habitats; indigenous species; indirect effects; Kenya; plant ecology; plant-animal interactions; Plants; prediction; regression analysis; Species; Species diversity; species-energy theory; Synecology; trophic guild; trophic relationships; vegetation; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; Woody plants; Kenya; Africa; indirect effects; trophic guild; Theory; Frugivorous; Taxon; Trophic relation; Autoregressive model; Woody plant; Biodiversity; Guild; Spatial variation; Kenya; cross-taxon congruence; Functional diversity; frugivory; Vertebrata; Spatial distribution; Animal plant relation; plant-animal interactions; species-energy theory; Environment; Aves; Community; community assembly
• ISSN: 1466-822X; 1466-8238; 1466-822X
• DOI: 10.1111/j.1466-8238.2007.00379.x

To understand cross-taxon spatial congruence patterns of bird and woody plant species richness. In particular, to test the relative roles of functional relationships between birds and woody plants, and the direct and indirect environmental effects on broad-scale species richness of both groups. Kenya. Based on comprehensive range maps of all birds and woody plants (native species > 2.5 m in height) in Kenya, we mapped species richness of both groups. We distinguished species richness of four different avian frugivore guilds (obligate, partial, opportunistic and non-frugivores) and fleshy-fruited and non-fleshy-fruited woody plants. We used structural equation modelling and spatial regressions to test for effects of functional relationships (resource-consumer interactions and vegetation structural complexity) and environment (climate and habitat heterogeneity) on the richness patterns. Path analyses suggested that bird and woody plant species richness are linked via functional relationships, probably driven by vegetation structural complexity rather than trophic interactions. Bird species richness was determined in our models by both environmental variables and the functional relationships with woody plants. Direct environmental effects on woody plant richness differed from those on bird richness, and different avian consumer guilds showed distinct responses to climatic factors when woody plant species richness was included in path models. Our results imply that bird and woody plant diversity are linked at this scale via vegetation structural complexity, and that environmental factors differ in their direct effects on plants and avian trophic guilds. We conclude that climatic factors influence broad-scale tropical bird species richness in large part indirectly, via effects on plants, rather than only directly as often assumed. This could have important implications for future predictions of animal species richness in response to climate change.