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Ballesteros-Mejia L, Kitching I, Jetz W, Beck J (2016)
Putting insects on the map: Near-global variation in sphingid moth richness along spatial and environmental gradients
Despite their vast diversity and vital ecological role, insects are notoriously underrepresented in biogeography and conservation, and key broad-scale ecological hypotheses about them remain untested – largely due to generally incomplete and very coarse spatial distribution knowledge. Integrating records from publications, field work and natural history collections, we used a mixture of species distribution models and expert estimates to provide geographic distributions and emergent richness patterns for all ca. 1,000 sphingid moth species found outside the Americas in high spatial detail. Total sphingid moth richness, the first for a higher insect group to be documented at this scale, shows distinct maxima in the wet tropics of Africa and the Oriental with notable decay toward Australasia. Using multivariate models controlling for spatial autocorrelation, we found that primary productivity is the dominant environmental variable associated with moth richness, while temperature, contrary to our predictions, is an unexpectedly weak predictor. This is in stark contrast to the importance we identify for temperature as a niche variable of individual species. Despite divergent life histories, both main sub-groups of moths exhibit these relationships. Tribal-level deconstruction of richness and climatic niche patterns indicate idiosyncratic effects of biogeographic history for some of the less species-rich tribes, which in some cases exhibit distinct richness peaks away from the tropics. The study confirms, for a diverse insect group, overall richness associations of remarkable similarity to those documented for vertebrates and highlights the significant within-taxon structure that underpins emergent macroecological patterns. Results do not, however, meet predictions from vertebrate-derived hypotheses on how thermoregulation affects the strength of temperature-richness effects. Our study thus broadens the taxonomic focus in this data-deficient discourse. Our procedures of processing incomplete, scattered distribution data are a template for application to other taxa and regions.
Keywords: Distribution modelling, Lepidoptera, Productivity, Spatial scale, Sphingidae, Tropics
Bocksberger G, Schnitzler J, Chatelain C, Daget P, Janssen T, Schmidt M et al. (2016)
Journal of Vegetation Science.
Questions Which environmental variables influence grass diversity in West Africa? What are the effects of climate and grass functional traits on the spatial patterns (richness and abundance) of the grass clades Andropogoneae, Paniceae and Chloridoideae? Location West Africa, demarcated by the Atlantic Ocean in the west and south (20° W and 4° N), the Sahara desert in the north (25° N) and the border between Niger and Chad in the east (20° E). Methods Based on 38 912 georeferenced occurrence records, we modelled the distribution of 302 grass species (51% of West African grass diversity). We integrated species richness, abundance and functional traits (life cycle, photosynthetic type and height) to determine the contribution of the most speciose grass clades (Andropogoneae, Paniceae and Chloridoideae) to overall grass diversity in West Africa. Results Precipitation is the variable most often influencing the species distribution models of grasses in West Africa. Richness and relative abundance of the tribe Andropogoneae show a centre of diversity in Sudanian savanna regions. The height of Andropogoneae species, generally >150 cm, is driving this ecological dominance. Species richness of the tribe Paniceae is more dispersed and shows two main centres of abundance: The southern regions with higher mean annual precipitation and tree density are dominated by C3 Paniceae species. The Sahelian regions in the north are dominated by short Paniceae species with the C4 NAD-ME photosynthetic subtype, as well as Chloridoideae possessing the same functional attributes. Conclusions Our study provides insight into the environmental correlates of grass species richness in West Africa and contributes to the much-needed research on tropical rangelands. Moreover, the integration of evolutionary history significantly improves our understanding of large-scale biodiversity patterns.
Keywords: Andropogoneae, Chloridoideae, Maxent, Paniceae, Poaceae, Savanna, Species distribution modelling, West Africa, species richness
Boucher F, Lavergne S, Basile M, Choler P, Aubert S (2016)
Perspectives in Plant Ecology, Evolution and Systematics 20 22-31.
Cushion-forming species occur in all cold and dry environments worldwide, where they play important engineering roles. Understanding the origins of cushion plants may thus provide insights into the evolutionary assembly of biomes under extreme climatic conditions. Here we investigate the evolutionary and biogeographic history of cushions in Angiosperms based on a global checklist of all cushion plants, along with phylogenetic, climatic, and biogeographic information. Our aim is to measure the frequency of this evolutionary convergence and to identify its historic, environmental, and biogeographic drivers. We show that cushions appeared at least 115 times in Angiosperms and that they mainly belong to families that occupy the coldest and driest environments on Earth. We found that cushions have intensively diversified in the Himalayas, the Andes, or New Zealand, while other regions like Patagonia have probably been hubs enabling cushion species to migrate between different alpine regions. We conclude that the cushion life form is a remarkable example of convergent key innovation, which has favored the colonization of cold and dry habitats.
Keywords: Alpine, Angiosperms, Arctic, Biogeography, Cushion plants, Evolutionary convergence
Dufresnes C, Litvinchuk S, Leuenberger J, Ghali K, Zinenko O, Stöck M et al. (2016)
Evolutionary melting pots: a biodiversity hotspot shaped by ring diversifications around the Black Sea in the Eastern tree frog ( Hyla orientalis )
Hotspots of intraspecific genetic diversity, which are of primary importance for the conservation of species, have been associated to glacial refugia, i.e. areas where species survived the Quaternary climatic oscillations. However, the proximate mechanisms generating these hotspots remain an open issue. Hotspots may reflect the long-term persistence of large refugial populations; alternatively, they may result from allopatric differentiation between small and isolated populations, that later admixed. Here we test these two scenarios in a widely distributed species of tree frog, Hyla orientalis, which inhabits Asia Minor and Southeastern Europe. We apply a fine-scale phylogeographic survey, combining fast-evolving mitochondrial and nuclear markers, with a dense sampling throughout the range, as well as ecological niche modeling, to understand what shaped the genetic variation of this species. We documented an important diversity center around the Black Sea, composed of multiple allopatric and/or parapatric diversifications, likely driven by a combination of Pleistocene climatic fluctuations and complex regional topography. Remarkably, this diversification forms a ring around the Black Sea, from the Caucasus through Anatolia and Eastern Europe, with terminal forms coming into contact and partially admixing in Crimea. Our results support the view that glacial refugia generate rather than host genetic diversity, and can also function as evolutionary melting pots of biodiversity. Moreover, we report a new case of ring diversification, triggered by a large, yet cohesive dispersal barrier, a very rare situation in nature. Finally, we emphasize the Black Sea region as an important center of intraspecific diversity in the Palearctic with implications for conservation.
Keywords: Alpine, Angiosperms, Arctic, Biogeography, Cushion plants, Evolutionary convergence
Ferreira G, Ferreira P, Chautems A, Waechter J (2016)
Subtropical species of Sinningia (Gesneriaceae): distribution patterns and limiting environmental factors
Flora - Morphology, Distribution, Functional Ecology of Plants 222 86-95.
The neotropical genus Sinningia Nees encompasses tuberous herbs or subshrubs which occupy a wide range of environments with respect to climate and soil or substrate types. The genus has more than 70 species distributed from Southern Mexico to Northern Argentina, with a diversity centre in the Brazilian Atlantic Rainforest. In this ecosystem, a large number of species occur in several particular vegetation types, occupying terrestrial, rupestrial and epiphytic substrates. The aims of this study were to describe the distribution patterns of subtropical Sinningia species, and to determine possible limiting factors for their range extension. We summarized environmental data for 21 subtropical species. Ten geographical and ecological variables were subdivided into several regional or local conditions. The occurrence of species in each of these conditions was obtained from published material, herbarium reviews and field expeditions. We used exploratory multivariate approaches, (cluster and ordination analyses) to assess the contribution of these variables to species’ ecological and geographical distributions. Comparisons between groups of species were evaluated using randomization tests. Two major patterns of geographic distribution were identified for subtropical Sinningia species: widespread and restricted. Species richness according to spatial and climatic variables showed four distinct patterns. Habitat tolerance of the species also distinguished two groups in a wider continuum context. Cluster analysis resulted in two stable groups, which coincided almost entirely with an a priori classification based on geographic range. Ordination analysis showed a distinction between widespread and restricted species, as well as a gradient of substrate occupancy. Patterns of ecological and geographical distribution were strongly related to the evolutionary history of the genus. The southern distribution limit of Sinningia is mainly linked to shifts in vegetation types around the 30°S parallel, where the northern forested Atlantic and Paranean biogeographic provinces give place to the southern non-forested Espinal and Pampean provinces.
Keywords: Biogeography, Corytholoma, Dircaea, Ecology, Plasticity
Fuchs J, Lemoine D, Parra J, Pons J, Raherilalao M, Prys-Jones R et al. (2016)
Long-distance dispersal and inter-island colonization across the western Malagasy Region explain diversification in brush-warblers (Passeriformes: Nesillas )
Biological Journal of the Linnean Society.
The present study examines the colonization history and phylogeography of the brush-warblers (Nesillas), a genus of passerines endemic to islands of the western Indian Ocean (Madagascar, Comoros, and Aldabra Atoll). The phylogeny of all recognized Nesillas taxa was reconstructed employing Bayesian phylogenetic methods and divergence times were estimated using a range of substitution rates and clock assumptions. Spatiotemporal patterns of population expansion were inferred and niches of different lineages were compared using ecological niche modelling. Our results indicate that taxa endemic to the Comoros are paraphyletic and that the two endemic species on Madagascar (Nesillas typica and Nesillas lantzii) are not sister taxa. The brush-warblers started to diversify approximately 1.6 Mya, commencing with the separation of the clade formed by two species endemic to the Comoros (Nesillas brevicaudata and Nesillas mariae) from the rest of the genus. The lineages leading to the two Malagasy species diverged approximately 0.9 Mya; each with significantly different modern ecological niches and the subject of separate demographic processes. Patterns of diversification and endemism in Nesillas were shaped by multiple long distance dispersal events and inter-island colonization, a recurring pattern for different lineages on western Indian Ocean islands. The diversification dynamics observed for Nesillas are also consistent with the taxon cycle hypothesis.
Keywords: MAXENT, demographic history, ecological niche modelling, island biogeography, mitochondrial sequence data, phylogenetic constraints, taxon cycle
Lee-Yaw J, Kharouba H, Bontrager M, Mahony C, Csergő A, Noreen A et al. (2016)
A synthesis of transplant experiments and ecological niche models suggests that range limits are often niche limits
Global change has made it important to understand the factors that shape species' distributions. Central to this area of research is the question of whether species' range limits primarily reflect the distribution of suitable habitat (i.e. niche limits) or arise as a result of dispersal limitation. Over-the-edge transplant experiments and ecological niche models are commonly used to address this question, yet few studies have taken advantage of a combined approach for inferring the causes of range limits. Here, we synthesise results from existing transplant experiments with new information on the predicted suitability of sites based on niche models. We found that individual performance and habitat suitability independently decline beyond range limits across multiple species. Furthermore, inferences from transplant experiments and niche models were generally concordant within species, with 31 out of 40 cases fully supporting the hypothesis that range limits are niche limits. These results suggest that range limits are often niche limits and that the factors constraining species' ranges operate at scales detectable by both transplant experiments and niche models. In light of these findings, we outline an integrative framework for addressing the causes of range limits in individual species.
Keywords: Abiotic constraints, climate, dispersal limitation, fitness, geographical distribution, over the edge transplant, species distribution modelling
Onstein R, Peter Linder H (2016)
Beyond climate: convergence in fast evolving sclerophylls in Cape and Australian Rhamnaceae predates the mediterranean climate
Journal of Ecology.
Morphological convergence in mediterranean-type ecosystems (MTEs) has long been interpreted as adaptation to climatic similarities among the five MTEs of the world. Here, we challenge this model using the globally distributed Rhamnaceae. We collected functional trait data (specific leaf area, leaf area, spinescence, leaf phenology, growth form and leaf margin type) and biome data to test for trait convergence in MTEs, for models of trait evolution and ancestral state reconstruction and for the effect of traits on speciation and extinction rates, using a phylogenetic framework. We show that leaf functional traits evolve to three optima, which correspond to (a) the edaphically specialized Australian and Cape MTEs (AC), (b) the mediterranean-type climates, but edaphically normal Chile, California and Mediterranean Basin (CCM), and (c) the non-mediterranean habitats. We find that Rhamnaceae in CCM are predominantly characterized by non-sclerophylly, the ancestral state in Rhamnaceae, and Rhamnaceae in AC by sclerophylly. These leaf character syndromes have evolved prior to mediterranean climates in MTEs, thereby failing to be adaptive to this selective regime. However, sclerophylly evolved contemporaneously with the transitions to AC, and may therefore be an adaptation to nutrient-poor soils. The evolution of sclerophylly has contributed to increased diversification rates of Pomaderreae in Australia and Phyliceae in the Cape, by reducing extinction rates and thereby facilitating evolutionary persistence. The historical relatively stable conditions in AC are consistent with this persistence hypothesis. Synthesis. In this study we integrate the fields of macroevolution and ecology and show that low extinction rates may not only account for the ecological, but also for the floristic dominance of sclerophylly in the hyperdiverse Australian and Cape mediterranean-type ecosystems.
Keywords: Cape flora, character syndrome, diversification rate, extinction rate, fynbos, kwongan, plant-climate interactions, sclerophylly, specific leaf area
Onstein R, Jordan G, Sauquet H, Weston P, Bouchenak-Khelladi Y, Carpenter R et al. (2016)
Evolutionary radiations of Proteaceae are triggered by the interaction between traits and climates in open habitats
Global Ecology and Biogeography.
Aim Ecologically driven diversification can create spectacular diversity in both species numbers and form. However, the prediction that the match between intrinsic (e.g. functional trait) and extrinsic (e.g. climatic niche) variables may lead to evolutionary radiation has not been critically tested. Here, we test this hypothesis in the Southern Hemisphere plant family Proteaceae, which shows a spectacular diversity in open mediterranean shrublands in the Southwest Australian Floristic Region (SWAFR) and the Cape Floristic Region (CFR). Species in the Proteaceae family occupy habitats ranging from tropical rain forests to deserts and are remarkably variable in leaf morphology. Location Southern Hemisphere. Methods We built a phylogenetic tree for 337 Proteaceae species (21% of the total), representing all main clades, climatic tolerances and morphologies, and collected leaf functional traits (leaf area, sclerophylly, leaf shape) for 261 species and climatic niche data for 1645 species. Phylogenetic generalized least squares regression and quantitative-trait evolutionary model testing were used to investigate the evolutionary pathways of traits and climatic niches, and their effect on diversification rates. Results We found that divergent selection may have caused lineages in open vegetation types to evolve towards trait and climatic niche optima distinct from those in closed forests. Furthermore, we show that the interaction between open habitats, dry, warm and/or mediterranean climates, and small, sclerophyllous, toothed leaves increases net diversification rates in Proteaceae. Main conclusions Our results suggest that the evolution of specific leaf adaptations may have allowed Proteaceae to adapt to variable climatic niches and diversify extensively in open ecosystems such as those in the CFR and SWAFR. This match between morphology and environment may therefore more generally lead to evolutionary radiation.
Keywords: Adaptation, climatic niche, evolutionary radiation, functional trait, leaf shape, mediterranean-type ecosystem, sclerophylly
Antonelli A, Zizka A, Silvestro D, Scharn R, Cascales-Miñana B, Bacon C (2015)
An engine for global plant diversity: highest evolutionary turnover and emigration in the American tropics.
Frontiers in genetics 6 130.
Understanding the processes that have generated the latitudinal biodiversity gradient and the continental differences in tropical biodiversity remains a major goal of evolutionary biology. Here we estimate the timing and direction of range shifts of extant flowering plants (angiosperms) between tropical and non-tropical zones, and into and out of the major tropical regions of the world. We then calculate rates of speciation and extinction taking into account incomplete taxonomic sampling. We use a recently published fossil calibrated phylogeny and apply novel bioinformatic tools to code species into user-defined polygons. We reconstruct biogeographic history using stochastic character mapping to compute relative numbers of range shifts in proportion to the number of available lineages through time. Our results, based on the analysis of c. 22,600 species and c. 20 million geo-referenced occurrence records, show no significant differences between the speciation and extinction of tropical and non-tropical angiosperms. This suggests that at least in plants, the latitudinal biodiversity gradient primarily derives from other factors than differential rates of diversification. In contrast, the outstanding species richness found today in the American tropics (the Neotropics), as compared to tropical Africa and tropical Asia, is associated with significantly higher speciation and extinction rates. This suggests an exceedingly rapid evolutionary turnover, i.e., Neotropical species being formed and replaced by one another at unparalleled rates. In addition, tropical America stands out from other continents by having "pumped out" more species than it received through most of the last 66 million years. These results imply that the Neotropics have acted as an engine for global plant diversity.
Keywords: Angiosperms, Latitudinal diversity gradient, biogeography, diversification rates, evolution, phylogenetics, tropical biodiversity