Differential patterns of floristic phylogenetic diversity across a post‐glacial landscape

Ida M Mienna,Mika Bendiksby,Michael D Martin,James D M Speed,Andrew H Thornhill,Brent D Mishler

doi:10.1111/jbi.13789

Abstract

AbstractAimIn this study, we explored spatial patterns of phylogenetic diversity (PD) and endemism in the flora of Norway and tested hypothesized post‐glacial environmental drivers of PD, including temperature, precipitation, edaphic factors and time since glacial retreat.LocationNorway.TaxonVascular plants (Trachaeophyta).MethodsWe produced a multi‐locus maximum‐likelihood (ML) phylogeny using a combination of newly produced DNA sequences from herbarium specimens and sequences available from public repositories. We combined the phylogeny with species occurrence data to estimate PD and phylogenetic endemism across Norway, using a spatial randomization to judge statistical significance. We used multiple‐model inference to identify environmental variables that contributed the most to the patterns of PD. Finally, we estimated phylogenetic turnover and used this to identify Norwegian plant assemblages in terms of composition and evolutionary history.ResultsOur ML phylogeny contained 87% of all currently described native Norwegian vascular plants. Assemblages were phylogenetically overdispersed in warmer and wetter regions of Norway, as well as in regions with a longer post‐glacial history. In cold and dry regions, plant assemblages were phylogenetically clustered, and characterized by neo‐endemism, while the mild and wet regions were characterized by both paleo‐ and neo‐endemism. PD was positively correlated with summer temperature and habitat heterogeneity, and peaked in the southeast of Norway.Main conclusionsBoth contemporary ecological factors (climate and habitat heterogeneity), and post‐glacial history seem to have shaped the phylogenetic structure of the flora of Norway. The flora in the far north of Norway appear to be a result of recent diversification while the coastal regions are assemblages of deeper lineages. Our results suggest that there is an evolutionary signal in the distribution of the Norwegian vascular flora.

Highlights

Understanding observed biodiversity patterns is important for conservation issues
Since the temperature variable in this study was highly correlated with other temperature variables in Norway (Speed & Austrheim, 2017), among them winter temperature, we argue that there would be a positive correlation between cold winter temperatures and northern mixed endemism cells
We show that despite its relatively recent origin via post-glacial colonization, Norway's vascular flora is non-randomly distributed in space in terms of evolutionary history

Summary

Introduction

Understanding observed biodiversity patterns is important for conservation issues. While species-level biodiversity patterns are most commonly studied in conservation biology, some regard phylogenetic diversity (PD) to be of greater importance since it encompasses the evolutionary history of the species (Faith, 1992; Kling, Mishler, Thornhill, Baldwin, & Ackerly, 2019). Spatial phylogenetics combines species occurrence data with molecular phylogenetics to recover information about the spatial distribution of PD and phylogenetic endemism (PE) across selected geographical regions (Mishler et al, 2014; Thornhill et al, 2016) This approach makes it possible to discover centres of endemism, distinguish phylogenetically clustered communities from phylogenetically dispersed ones and identify regions differing in phylogenetic composition. Previous studies have investigated spatial patterns of PD and endemism of vascular plants in regions with long evolutionary histories, such as Australia (Mishler et al, 2014; Nagalingum et al, 2015; Thornhill et al, 2016), Chile (Scherson et al, 2017), California (Thornhill et al, 2017), Mexico (Sosa, De-Nova, & Vasquez-Cruz, 2018) and Florida (Allen, Brown, & Gillooly, 2002) In these regions, the flora has had considerable opportunity to evolve in situ. In floras with a short evolutionary history, regardless of the cause, it is likely that immigration plays a larger role in determining the phylogenetic composition of communities than in situ diversification (Ma, Sandel, & Svenning, 2016)

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Conclusion