Abstract Detail

Biogeography

Monks, Logan [1], Davies, Stuart [2], Swenson, Nathan [1].

Climate and geographic distance drive phylogenetic regionalization in the world's tree flora.

The biogeographic distribution of trees is the result of barriers to dispersal, environmental filtering, and biogeographic region of origin. Thus, closely related species that have shared evolutionary and biogeographic history as well as similar ecological characteristics often exhibit congruent geographic ranges. This expectation is the basis for a phylogenetic regionalization scheme of the world’s forests that reflects shared evolutionary history and avoids the pitfall of treating taxa as independent data points. Here, we provide results from a phylogenetic regionalization of the world’s tree flora using a forest inventory dataset from 70 large scale forest plots that are part of the Smithsonian ForestGEO Network of long-term forest dynamics plots. We first assembled the dataset and standardized the taxonomic treatment of species across the network. We then created a phylogeny of our dataset using an existing phylogenetic tree for vascular plants and calculated pairwise phylogenetic beta-diversity between each plot. Phylogenetic beta-diversity was quantified using the mean nearest taxon distance between plots. Plots were hierarchically clustered to create a tree like dendrogram useful for a first assessment of forest relatedness. Our results demonstrate clear evolutionary distinctions between temperate, tropical, and subtropical (warm temperate China) tree flora. Additionally, there are regional distinctions in tropical tree flora such that Asian tropical forests are more closely related to African tropical forests than either are to American tropical forests. These results in conjunction with the separation of tropical and subtropical flora contrast with recently published relationships between tropical forests. The use of phylogeny in our work permitted further investigation into the processes that drive evolutionary relatedness and phylogenetic beta-diversity of the world’s forests. From previous published work, we hypothesized that climate and past dispersal barriers would jointly drive patterns of phylogenetic beta diversity. Furthermore, we hypothesized that climate is important in defining basal clusters of forest plots (e.g. temperate vs tropical) while geographic distance, as a proxy for barrier to dispersal, will exhibit greater importance in delineating more terminal clusters (e.g. Asian vs African tropical). Geographic distance and Euclidean distance between plots in multivariate climate space (precipitation and temperature variables) were used to hierarchically cluster plots in a manner analogous to our approach for phylogenetic beta-diversity. Statistical tests of dendrogram similarity between hierarchical clusters of phylogenetic, climate, and geographic distance reveal that both geographic distance and climatic distance explain phylogenetic (dis)similarity of the world’s forests. As we hypothesized, climatic variables were most important in explaining the basal clustering of plots and declined in importance in more terminal clusters. Geographic distance had a greater importance in explaining more terminal clusters beginning with the distinction between tropical forest clusters. Moreover, indicator lineages of more basal clusters demonstrated differentiation from one another along climate axes while lineages from more terminal clusters did not. We interpret this as compelling evidence that phylogenetic similarity of forests is foremost determined by climatic niches of lineages and secondarily by dispersal limitation. Thus, as climate becomes increasingly similar between forests, dispersal limitation plays a larger role in structuring the evolutionary similarity between forests.

1 - University of Notre Dame, Biological Sciences, 100 Galvin Life Science Center, Notre Dame, IN, 46556, USA
2 - Smithsonian Tropical Research Institute, Forest Global Earth Observatory, Smithsonian Tropical Research Institute, Washington, DC, 20053

Keywords:
Trees
forests
Phylogenetic beta-diversity
Biogeographic regions.

Presentation Type: Oral Paper
Number: BIOG I009
Abstract ID:776
Candidate for Awards:None