Patterns of Beta Diversity of Vascular Plants and Their Correspondence With Biome Boundaries Across North America

Jesús N Pinto-Ledezma,Jeannine Cavender-Bares,Daniel J Larkin

doi:10.3389/fevo.2018.00194

Jesús N Pinto-Ledezma, Jeannine Cavender-Bares + Show 1 more

Open Access

https://doi.org/10.3389/fevo.2018.00194

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Abstract

Understanding why species composition and diversity varies spatially and with environmental variation is a long-standing theme in macroecological research. Numerous hypotheses have been generated to explain species and phylogenetic diversity gradients. Much less attention has been invested in explaining patterns of beta diversity. Biomes boundaries are thought to represent major shifts in abiotic variables accompanied by vegetation patterns and composition as a consequence of long-term interactions between the environment and the diversification and sorting of species. Using North American plant distribution data, phylogenetic information and three functional traits (SLA, seed mass and plant height), we explicitly tested whether beta diversity is associated with biome boundaries and the extent to which two components of beta diversity – turnover and nestedness – for three dimensions of biodiversity (taxonomic, phylogenetic and functional) – are associated with contrasting environments and linked to different patterns of historical climatic stability. We found that dimensions of vascular plant beta diversity are strongly coupled and vary considerably across North America, with turnover more influential in biomes with higher species richness and greater environmental stability and nestedness more influential in species-poor biomes characterized by high environmental variability. These results can be interpreted to indicate that in harsher climates with less stability explain beta diversity, while in warmer, wetter more stable climates, patterns of endemism associated with speciation processes, as well as local environmental sorting processes, contribute to beta diversity. Similar to prior studies, we conclude that patterns of similarity among communities and biomes reflects biogeographic legacies of how vascular plant diversity arose and was shaped by historical and ecological processes.

Highlights

Ecological and evolutionary processes act in concert to modulate species traits that determine colonization and persistence of species within assemblages and across regions through evolutionary time (Simpson, 1953; Cavender-Bares et al, 2016)
Beta diversity and its components were unevenly distributed across North America (Figure S3). βsim for all three dimensions of vascular plant diversity was higher in dry and temperate biomes in southern North America and in polar biomes in northern North America, whereas, βnes was higher at mid- to high latitudes positioned between polar and temperate biomes (Figure 2)
Spatial structure of the βnes and βsim components were similar across the three dimensions of plant vascular diversity (Figures 2A–C; Figure S3), which showed high spatial congruence based on spatial correlations (Table 1) and correlograms (Figure S4)

Summary

Introduction

Ecological and evolutionary processes act in concert to modulate species traits that determine colonization and persistence of species within assemblages and across regions through evolutionary time (Simpson, 1953; Cavender-Bares et al, 2016). A crucial challenge for understanding how biodiversity is structured and maintained through time is the integration of ecological and evolutionary processes at different spatial scales (Graham and Fine, 2008) To this end, analysis of beta diversity is a promising approach that allows heterogeneity in the distribution of gamma and alpha diversities to be quantified (Loreau, 2000; Baselga, 2010), permitting the evaluation of how species or lineages change across space and in response to environmental variation (Graham and Fine, 2008; Baselga, 2010). We apply a partition procedure for beta diversity (Baselga, 2010; Leprieur et al, 2012) that allows the identification of species poor regions (differences in diversity between biomes—the nestedness component) and replacement regions (diversity interchange between biomes—the turnover component) (Baselga, 2010; Leprieur et al, 2012; see Box 1)

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