Bridging meta-analysis and the comparative method: a test of seed size effect on germination after frugivores’ gut passage

Abstract

Most studies using meta-analysis try to establish relationships between traits across taxa from interspecific databases and, thus, the phylogenetic relatedness among these taxa should be taken into account to avoid pseudoreplication derived from common ancestry. This paper illustrates, with a representative example of the relationship between seed size and the effect of frugivore's gut on seed germination, that meta-analytic procedures can also be phylogenetically corrected by means of the comparative method. The conclusions obtained in the meta-analytical and phylogenetical approaches are very different. The meta-analysis revealed that the positive effects that gut passage had on seed germination increased with seed size in the case of gut passage through birds whereas decreased in the case of gut passage through non-flying mammals. However, once the phylogenetic relatedness among plant species was taken into account, the effects of gut passage on seed germination did not depend on seed size and were similar between birds and non-flying mammals. Some methodological considerations are given to improve the bridge between the meta-analysis and the comparative method.

Methodological issues and advances in biological meta-analysis

“…A series of papers have demonstrated the importance of controlling phylogeny for comparing phenotypic traits across species (reviewed in Freckleton et al 2002;Blomberg et al 2003). The earlier attempts at controlling for phylogeny included running both standard metaanalysis and comparative analysis on the same datasets (see Dubois and Cezilly 2002;Verdu and Traveset 2004; see also Verdu and Traveset 2005), because software packages to conduct 'phylogenetic' meta-analysis (sensu Adams 2008) were not available. Adams (2008) first described how the fixed-effect meta-analytic model could incorporate phylogenetic relatedness.…”

Fitness‐related benefits of dominance in primates

“…In a study on seed germination in relation to seed size and seed passage through frugivores' guts, Verdú and Traveset (2004) compared results obtained from standard meta-analysis and nonmeta-analytic phylogenetic comparative methods. They found significant differences between the results obtained with the two methods and concluded that standard meta-analysis and phylogenetic methods should be used concurrently.…”

Western lowland gorilla seed dispersal: Are seeds adapted to long gut retention times?

“…It has been shown that phylogenetic relatedness among plant species is a crucial aspect that must be considered when interpreting gut passage effect (Verdu and Traveset, 2004), as species Table 3 Results of the generalized linear models performed to test the impact of seed treatment (western lowland gorilla gut passaged, manually depulped and within intact fruits) on germinability of the five tree species tested.…”