Influence of phylogeny and ploidy on species ranges of North American angiosperms

Abstract

Summary1. Species differ widely in the size and ecological characteristics of their geographic ranges. This variation reflects, in part, differences in ecological tolerance among taxa, but the influence of phylogeny and evolutionary divergence through genome duplication remains controversial. 2. Here, we examine the evolutionary sources of variation in species range area, latitudinal position and overlap, and six range climatic variables (maximum, minimum and breadth of temperature and precipitation) for North American angiosperms. We sampled two diploid and one polyploid species from each of 144 genera and examined sources of variation in a nested taxonomic analysis and congeneric species pairs comparison. 3. For all range characteristics studied, a significant portion of the variance among species (mean 53%, range 37-60%) was attributable to taxonomic membership above species (i.e. genus, family and order). Four of the seven range attributes were significantly correlated between diploid congeners (e.g. range area r s = 0.65) and between heteroploid (diploid and polyploid) congeners (e.g. range area r s = 0.62). The strength of correlations between heteroploid relatives was not consistently different than correlations between diploids. 4. No differences in mean range breadth (range area, temperature breadth, precipitation breadth) or climatological position (minimum and maximum temperature and precipitation) were observed between diploid and polyploid congeners. Polyploids were not more likely to occupy northern latitudinal positions and were no more displaced from diploids than other congeneric diploids. 5. Synthesis. Our results suggest that, at the scale of North America, the geographical and ecological aspects of species ranges are influenced by phylogenetic history. Furthermore, genome duplication does not cause or allow greater divergence in species range characteristics than occurs between related diploid species.

Angiosperm polyploids and their road to evolutionary success

“…So far, it has been difficult to prove that polyploids in general have a higher adaptability or ecological tolerance compared to their diploid progenitors. For instance, Martin and Husband 34 compared the geographical and ecological ranges of polyploids and diploids taking their phylogenetic history into account, but could not find any significant differences in the ranges of polyploids and their diploid relatives. Another recent study reported an example in which diploids had a higher fitness and are replacing polyploids.…”

“…21,44,45 Thus, comparative studies of polyploids and diploids regarding factors such as their range, adaptability, or diversification potential is likely to be affected by the different phases of the sampled polyploids. Recent studies on the range or diversification rate have treated polyploids of all ages equally, 34,46 and taking into account the different stages of establishment could be one of the next steps in order to imoprove our understanding of the evolutionary dynamics of polyploids.…”

Ecological studies of polyploidy in the 100 years following its discovery

“…For example, latitudinal analyses of polyploidy are biased towards floras of Europe and North America; much less cytogeographical work has been done in the tropics or in temperate regions of the Southern Hemisphere [69]. Building on knowledge of species distributions and evolutionary relationships among genera and families, more explicit testing of the incidence of polyploids is now possible [73][74][75][76]. For example, a phylogenetically explicit analysis of the genus Clarkia found that polyploids on average have fivefold greater range sizes (area in km 2 ) than diploids [75].…”

“…It may never be possible to fully untangle the functional, historical, phylogenetic and environmental factors that were associated with polyploidy by classical botanical research, but much more comprehensive efforts may now be attempted. Phylogenetic relationships within polyploid species complexes provide the foundation for these efforts, coupled with improved knowledge about cytotype spatial distributions and biological characteristics [73][74][75][76]237,250]. Arguably the biggest limitation to recent studies is the focus on small numbers of factors-geographical range size being the most popular choice for analysis-which makes it difficult to tease apart direct and indirect relationships among variables.…”

Polyploidy and novelty: Gottlieb's legacy

“…Recent publications have assessed polyploid ecogeography using these techniques in a variety of systems [116,[118][119][120]131]; however, few conclusive patterns have emerged. Future studies must take into account phylogeny, type of polyploid and a wide variety of ecological variables at a scope so far unattained, yet achievable with current digitized resources.…”