Illinois State Museum

ABSTRACTThere are two major groups of methods estimating diversification rates: One group depends on well resolved phylogenies and the other is phylogeny‐free. Previous studies on angiosperms (flowering plants) have used phylogeny‐based methods to estimate diversification rates and concluded that diversification rates increase with increasing latitudes, a trend opposite to that of liverworts, mosses and ferns, for which diversification rates were estimated with the method‐of‐moments estimator, a nonphylogeny method. In this study, we use the method‐of‐moments estimator to estimate diversification rates of angiosperm species within genera worldwide. We find that diversification rates decrease with increasing latitudes. The result of our study is thus contrary to those of previous studies on angiosperms. We discuss the degree to which these differences are due to methodological limitations of using phylogeny‐based approaches to estimate diversification rates of angiosperms. More data from poorly studied angiosperm groups are needed so that we can move toward developing well‐resolved species‐level phylogenies for angiosperms, which will allow a better assessment of the robustness of various diversification estimation methods.

Biological invasions by non-native fish species pose a major threat to global freshwater ecosystems. However, our understanding of why invaders establish in some communities but not others (i.e., occurrence probability) and why some communities harbor more invaders than others (i.e., invasion richness) remains limited. Here, we combine species- and community-level analyses across taxonomic, phylogenetic, and functional dimensions to investigate both the occurrence probability and invasion richness of exotic and translocated fish species across nearly 3000 North American freshwater fish communities. We found that ecological similarity between non-native and native species primarily governed non-native fish establishment, with invaders more likely to succeed when closely related to native species. In contrast, invasion richness was largely promoted by human pressure, while native diversity reduced richness specifically for translocated species. Additionally, both the occurrence and richness of invaders increased toward lower latitudes. Together, these findings highlight the distinct yet complementary roles of environmental filtering, human activities, and biotic interactions in shaping freshwater fish invasions.

ABSTRACTAimPhylogenetic niche conservatism predicts that species tend to retain the ecological traits of their ancestors. Accordingly, communities developing under more stressful conditions should be more strongly structured by environmental filtering than communities in less stressful conditions, and thus would exhibit lower phylogenetic dispersion and diversity. Elevational gradients offer unique opportunities to studying, among others, phylogenetic structure patterns across climatic gradients because the geographic distance of the same length of a climatic gradient is much shorter along an elevational gradient than along a latitudinal gradient. Here, we examine the relationship of phylogenetic diversity and dispersion of angiosperms in local communities with elevation and climate along a temperate elevational gradient.LocationThe Siskiyou Mountains in the western United States.TaxonAngiosperms.MethodsPhylogenetic diversity and dispersion of angiosperms in 236 local communities distributed along an elevational gradient ranging from 533 to 2103 m were related with elevation, mean annual temperature and annual precipitation using correlation and regression analyses. Variation partitioning analysis was conducted to assess the relative importance of temperature and precipitation in affecting phylogenetic diversity and dispersion.ResultsPhylogenetic diversity and dispersion in angiosperm communities generally decrease with increasing elevation but the opposite pattern is observed in the middle segment of the elevational gradient. The patterns are more conspicuous for herbaceous plants than for woody plants. Temperature is more strongly associated with phylogenetic diversity and dispersion of angiosperm communities compared to precipitation.Main ConclusionsThe patterns of phylogenetic diversity and dispersion in angiosperm communities along the elevational gradient in the Siskiyou Mountains are consistent with the tropical niche conservatism hypothesis, which predicts that communities in areas with lower temperature and precipitation would have lower phylogenetic diversity and dispersion.

Liverworts are an ancient plant lineage that occurs worldwide with the highest species richness in cool and humid habitats such as tropical montane and temperate rain forests. It has been proposed that liverworts originated under such temperate climatic conditions and have later expanded into more tropical conditions, but how this is reflected in their phylogenetic diversity along the strong climatic gradients associated with elevation remains unexplored. We studied the phylogenetic diversity of regional liverwort floras along the elevational gradient in the tropical Andes, comparing indices that emphasize deeper and shallower phylogenetic relationships, and relating these to temperature‐ and precipitation‐related variables, as well as to climatic extremes and seasonality. We found that whereas liverwort species richness peaks at around 2000 m a.s.l., richness‐corrected phylogenetic diversity increases with elevation, and the standardized effect of size of phylogenetic diversity is highest at 2500–4000 m a.s.l. This is in accordance with an origin of liverworts under cool conditions, followed by more recent diversification in warmer climates at lower elevations. We further found temperature‐related climatic parameters to be stronger predictors of phylogenetic diversity of liverworts than precipitation‐related variables, and climatic extremes to have a stronger influence than climatic seasonality. We interpret these patterns as reflecting the physiological challenges of adapting to low temperatures as well as rare occurrences of extreme climatic events. All this reveals a strong signal of the evolutionary dynamics of this ancient plant lineage linked with its physiological adaptations to climatic conditions. The age of this group and its poikilohydric nature, i.e. its inability to regulate water loss, lead to patterns that contrast with those of vascular plants, allowing for discerning evolutionary generalities that are independent of physiology and lineage age.

Abstract Species range size is a central topic in macroecology, biogeography and conservation biology. Species age has been frequently regarded as a contributor to range size in previous studies on range size, but this has rarely been specifically examined. Using global data from four living terrestrial vertebrate classes (birds, mammals, reptiles and amphibians) as a case study, we examine how species range size might be related to species age at a global scale. We found statistically significant positive, albeit weak, species age–range size relationships for all four species groups. However, although the age–range relationships were positive, species with young ages had very different range sizes (both large and small), and those with very old ages always had small ranges. The observed age–range relationships were more complex than expected. The weak, rather than strong, species age–range relationships could be because our data set included all living species with different stages of their life spans (durations) that are either expanding or fluctuating or contracting, which would necessarily have minimized or cancelled species age–range relationship when all species in a group are considered collectively. Our findings shed new light on temporal dimension and macroecological correlates of species ranges.