The influence of climate on the spatial patterning of Neotropical plant families

Abstract

Aim: Climate is recognized for the significant role it plays in the global distribution of plant species diversity. We test the extent to which two aspects of climate, namely temperature and precipitation, explain the spatial distribution of high taxonomic groupings (plant families) at a regional spatial resolution (the Neotropics). Our goal is to provide a quantitative and comparative framework for identifying the local effects of climate on the familial composition of tropical forests by identifying the influence of climate on the number of individuals and the number of species within a given family. Location: One hundred and forty-four 0.1-ha forest transect sites from the Neotropics (19.8°N-27.0°S and 40.1°W-105.1°W). Data were originally collected by A.H. Gentry. Methods: Spatial variability in the abundance (density) and species richness of 159 tropical plant families across a range of predominately lowland Neotropical landscapes were attributed to eight temperature and precipitation measures using the eigen analysis method of two-field joint single-value decomposition. Results: Climate significantly affects the within-clade diversity of several ecologically important Neotropical plant families. Intrafamily abundance and richness covary with temperature in some families (e.g. Fabaceae) and with precipitation in others (e.g. Bignoniaceae, Arecaceae), with differing climatic preferences observed even among co-occurring families. In addition, the family-level composition of Neotropical forests, in both abundance and richness, appears to be influenced more by temperature than by precipitation. Among lowland families, only Asteraceae increased in species richness with decreasing temperature, although several families, including Melastomataceae and Rubiaceae, are more abundant at lower temperatures. Main conclusions: Although plant diversity is known to vary as a function of climate at the species level, we document clear climatic preferences even at the rank of family. Temperature plays a stronger role in governing the familial composition of tropical forests, particularly in the richness of families, than might be expected given its narrow annual and diurnal range in the tropics. Although other environmental or geographic variables that covary with temperature may be more causally linked to diversity differences than temperature itself, the results nonetheless identify the taxonomic components of tropical forest composition that may be most affected by future climatic changes. © 2007 The Authors.