Frontiers of Biogeography

Open access, shifting publishing mores, predatory journals, reviewer over-burden are just a few of the factors reshaping modern scientific publishing. How are changes in the publishing environment influencing biogeography?  Over the past eight years, 63 different titles have been among the 25 journals publishing most “biogeography” articles in any given year; a small nucleus of journals has consistently published a large proportion of “biogeography” papers.  Yet, the journals enjoying the largest positive trends—e.g. increasing share of biogeography publications and increasing Impact Factor—are outside of the nucleus; they are emerging open access ‘mega-journals’ that offer simplified criteria for publication. From the fault lines appearing across the publishing landscape, we see opportunities emerging for Frontiers of Biogeography as a vigorous hybrid model that leverages the strengths of ‘old world’ and ‘new world’ approaches to disseminating scientific knowledge and nurtures mutual benefits.

Vegetation systems with varying levels of tree cover are widely distributed globally, but the determinants of vegetation and tree cover still lack a consistent global framework. How these systems’ distribution responds to spatial variability of climate seasonality and associated fire regimes therefore remains unclear.  Here, we focus on tree cover distribution at the global level. We develop a model that accounts for the role of seasonality and moisture in the dynamics that link climate, fire and tree cover. We choose predictors that have a clear link to functional processes that control tree physiology and growth, such as freezing tolerance (accounted for in the variable growing season length, GSL) and the balance between water availability and evapotranspiration (accounted for in the variables moisture index and moisture season length). The results show that the relative importance of climate factors and fire frequency as determinants of tree cover hinges on the GSL conditions. For example, significant interactions of tree cover with fire only occur in regions with GSL of 6–7 months or of 12 months. Our data also show a general relationship between maximum tree cover and moisture at the global level that is not visible when examining precipitation. Discontinuities in this relationship occur with frequent fires found under specific levels of seasonal moisture and temperature. A common climatic trait of frequent fires is moisture with a pronounced seasonality and an overall negative balance over the growing season. Frequent fires allow grassland to persist where there could be savanna/woodland as in the case of the North American grasslands. Frequent fires also allow savanna to persist where there could be forest, as found in tropical regions. This quantitative work is useful in improving large-scale land-atmosphere models as well as for identifying conditions of vulnerability for ecosystem diversity.

The role of environmental gradients as drivers of biological diversity has been the center of many discussions in ecology and evolution. Hypotheses proposed to explain broad-scale patterns of biological diversity have mechanistic bases that often overlap, at least partially. Consequently, it is often difficult to tease apart the potential effects of different hypotheses. Here I investigate the synergism among macroecological hypotheses commonly invoked to explain species diversity. More specifically, I address the role of ambient-energy, climatic stability, habitat heterogeneity, productivity, and topographic complexity in shaping broad-scale patterns of tropical vertebrates under three different aspects of biological diversity: species richness, species pools, and species composition. I show how differences in the degree of synergism among distinct types of environmental gradients can be used to improve our understanding of traditional macroecological hypotheses, highlighting the convergent findings across the three different aspects of biological diversity.

The present-day southern South American flora comprises a group of lineages with southern temperate affinities, which have been suggested to have evolved during and after the breakup of Gondwana, as well as a group of Neotropical elements which are largely found in northern South America. Here, I aim to assess the floristic coherence of the main vegetation types that inhabit this region and determine the principal drivers of variation in the evolutionary diversity of these forest communities. I compiled a database of 3662 species of shrubs and trees at 781 sampling sites spread over six countries in South America. To understand the vegetation types that occur in the region I conducted clustering and ordination analyses. I then compared the defined vegetation types using taxonomic distinction, indicator species and phylogenetic diversity analyses. My results indicated a high diversity of vegetation types in terms of woody floristic composition, with a large number of indicator species, many of which are endemic. Contradicting the idea that temperate floras are recently derived and evolutionarily poor subsets of tropical floras, I demonstrated that the forests of the far south of South America are characterized by exceptional evolutionary diversity.

Predicting the ecological effects of environmental perturbations remains challenging due to complex interactions between species and the environment, which constantly adapt the ecological memory and, thus, the future response of ecosystems. General theoretical frameworks like the Complex Adaptive Systems (CAS) theory might provide a solution. Here I discuss the applicability of the CAS theory for ecosystems by examining its three major principles (interaction, adaptation and scale dependence) for spring fens. For these ecosystems, adaptation of plant communities to historical environmental stressors (acidification) affecting the resilience to subsequent perturbations (climatic extremes) is empirically shown. Alternative stable states in community composition initiated by acidification turned out to be stabilized by abiotic-biotic feedbacks. Furthermore, ecological response of species to temperature showed high cross-scale similarity. I argue that the exceptional environmental character of spring fens qualifies these ecosystems as ideal model systems to test and further develop CAS theory for ecology and biogeography.

Book Review of: 

Plant functional diversity: organism traits, community structure and ecosystem properties

Eric Garnier, Marie-Laure Navas, and Karl Grigulis

Oxford University Press, 2016, £70.00 (hardback) / £37.50 (paperback), 256 pp.

ISBN: 978-0-19-875736-8 (hardback) / 978-0-19-875737-5 (paperback).