Global patterns and climatic determinants of phylogenetic structure of regional fern floras

Abstract

Knowledge of relationships between phylogenetic structure of a biological assemblage and ecological factors that drive the variation of phylogenetic structure among regions is crucial for understanding the causes of variation in taxonomic composition and richness among regions, but this knowledge is lacking for the global flora of ferns. Here, we fill this critical knowledge gap.We divided the globe into 392 geographic units on land, collated species lists of ferns for each geographic unit, and used different phylogenetic metrics (tip-vs basal-weighted) reflecting different evolutionary depths to quantify phylogenetic structure. We then related taxonomic and phylogenetic structure metrics to six climatic variables for ferns as a whole and for two groups of ferns (old clades vs polypods) reflecting different evolutionary histories across the globe and within each continental region.We found that when old clades and polypods were considered separately, temperaturerelated variables explained more variation in these metrics than did precipitation-related variables in both groups. When analyses were conducted for continental regions separately, this pattern holds in most cases.Climate extremes have a stronger relationship with phylogenetic structure of ferns than does climate seasonality. Climatic variables explained more variation in phylogenetic structure at deeper evolutionary depths.

Effects of climate and environmental heterogeneity on the phylogenetic structure of regional angiosperm floras worldwide

“…All of these factors in combination lead to a situation where the effects of recent diversification events are more easily explained than those in the deep past. Interestingly, our finding that environmental variables explain more variation in phylogenetic metrics reflecting shallow evolutionary history than in those reflecting deep evolutionary history is contrary to the finding for regional fern floras across the world 44 . This discrepancy might result from differences in evolutionary histories between the two groups of plants.…”

“…For example, averaging across the five phylogenetic metrics and comparing the six continents, the environmental variables explained the most (87%) variation in Southern America and the least (55%) variation in Africa. This is consistent with the findings of Qian et al 44 for ferns, where the variation in phylogenetic metrics that was explained by environmental variables varied greatly among the continents, and the environmental variables explained the least variation in Africa. However, because phylogenetic metrics and environmental variables examined in the two studies are not identical, a direct comparison between the findings of the two studies cannot be made.…”

“…However, when individual continents were considered separately, temperature-related variables played a more important role in Europe, Australasia, and Southern America, whereas precipitation-related variables played a more important role in Asia, Northern America, and Africa. This pattern of the relative effects of these two types of current climatic variables on phylogenetic structure for angiosperms in different continents is largely similar to that for ferns 44 . Similar mixed patterns were also observed when comparing the relative effects of climate extreme and climate seasonality on the phylogenetic structure.…”

“…Specifically, PD is the sum of all phylogenetic branch lengths that connect species in an assemblage 69 . Because PD increases with species richness, which commonly increases linearly with log-transformed sampling area 17 , we divided PD in each region by the log 10 -transformed area (in square kilometers) of the region to account for variation in sampling area 15 , 18 , 44 . Area-corrected PD in each region was considered as a measure of PD in the region in this study.…”

Foliar endophyte diversity in Eastern Asian-Eastern North American disjunct tree species – influences of host identity, environment, phylogeny, and geographic isolation

“…Many studies have been conducted to understand the phylogeny and biogeography of these disjunct genera to gain insights into the origin and evolution of the phytogeographic pattern (e.g., Xiang et al., 1998b ; Xiang et al., 2000 ; Donoghue and Smith, 2004 ; Xiang et al., 2004 ; Harris et al., 2013 ; reviewed in Wen, 1999 , and Wen et al., 2010 ; Wen et al., 2016 ). Recent studies have also examined morphological and molecular evolution in disjunct lineages, and some have integrated climatic data to decipher the underlying ecological drivers from a phylogenetic perspective (e.g., Du et al., 2020 ; Gaynor et al., 2020 ; Lindelof et al., 2020 ; Melton et al., 2020 ; Zhou et al., 2020 ; Melton et al., 2022 ; Qian et al., 2023 ). This large-scale phytogeographic pattern provides a unique opportunity for studying plant spatiotemporal evolution and the underlying mechanisms following allopatric speciation due to the presence of disjunct sister species or clades that have diverged over different lengths of time ( Wen et al., 2010 ; Dong et al., 2019 ; Melton et al., 2020 ).…”