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Aim Gondwanan vicariance, boreotropical migration and long‐distance dispersal have been posited as alternative hypotheses explaining the tropical distribution patterns and diversifications in many fern groups. Here, the historical biogeography of Diplazium is reconstructed to evaluate the impact of these biogeographical processes in shaping the modern tropical disjunctions. Location World‐wide with a focus on tropical forest habitats. Methods Divergence times were estimated by analysing nucleotide sequences of seven plastid DNA regions (atpA, atpB, matK, rbcL, rps4, rps4–trnS and trnL–F) from 123 species of Diplazium and its allied genera, using a Bayesian relaxed clock method and three fossil calibrations. The ancestral areas were reconstructed using the likelihood dispersal–extinction–cladogenesis (DEC) approach. Results The crown group of Diplazium was estimated to have originated in Eurasia and undergone an initial diversification in the Northern Hemisphere around 41.7 Ma [95% highest posterior density (HPD): 34–49 Ma] during the Eocene. Two disjunct events between the Old and New World were identified: one in subgenus Diplazium around the Eocene–Oligocene boundary (31.2 Ma, 95% HPD: 25–38 Ma), and the other in subgenus Callipteris during the middle Miocene (12.6 Ma, 95% HPD: 15–23 Ma). Furthermore, Palaeotropical disjunctions in subgenus Callipteris are indicative of multiple dispersal events during the Miocene. Main conclusions The evolutionary history of Diplazium involves a variety of biogeographical scenarios. Early diversification of Diplazium in the Northern Hemisphere during the Eocene corresponds with the migration from Eurasia to North America over land bridges as a member of the boreotropical flora. The current tropical amphi‐Pacific disjunctions in subgenus Diplazium can be better explained by the disruption of boreotropical belt, however, long‐distance dispersal between Eurasia and tropical America cannot be ruled out. Island‐hopping and trans‐Pacific dispersals followed by speciation characterize the disjunctions and diversifications of subgenus Callipteris during the Neogene. Gondwanan vicariance is not supported by any of our results.

Aim The aim of this study was to investigate whether the equilibrium theory of island biogeography (ETIB) is equally applicable at regional and local spatial scales, and whether the 'echo pattern', the correlation between regional species pool and local diversity by which the diversity of the regional species pool 'trickles down' to local scales, influences local diversity equally across a range of sampling scales.Location Twelve mountain regions on islands having different sizes, degrees of isolation and environmental conditions in Indonesia and the Philippines.Methods We sampled ferns in standardized field plots within a fixed spatial design at six spatial scales (with the grain size varying from plot to island). Using ordinary least squares regression and relative variable importance, we tested for the predictive power of area and isolation as well as of local and regional environmental factors for explaining diversity at the chosen spatial scales.Results Consistent with MacArthur and Wilson's ETIB, we found the strongest correlations of area and isolation with diversity at regional scales. The explanatory power of area increased with increasing spatial scale. The strength of the negative relationships among diversity and isolation decreased with increasing spatial scale. We found evidence for an 'echo pattern' at large to intermediate but not at small spatial scales.Main conclusions Area and isolation are strong predictors of biodiversity at regional scales. The size of the species pool has a scale-dependent influence on diversity at smaller scales but is unimportant at the most local scale, where environmental conditions dominate as predictors of diversity. To make predictions about local diversity on islands it is therefore important to take the scale dependence of the 'echo pattern' into account.

We investigated if an increase in species pool size leads to more pronounced turnover in local communities and assessed if this increase relates to stronger competition for environmental niches or to more random placement of species. We compared compositional turnover of pteridophytes (ferns and lycophytes) at 15 sites in mountain ecosystems on 13 islands in southeast Asia and Melanesia that mainly differed in the size of their species pool. Each site was sampled with 16 plots of 20 × 20 m2. Using multiple regression on distance matrices, we investigated the relationship between environmental distance and compositional turnover at different spatial extents within sites with different species pool sizes. Additionally, we tested the hypothesis that the intensity of competition increases with increasing species pool size. This was done by assessing how realized niche overlap and unevenness of communities relate to environmental distance and species pool size. With increasing species pool size, there was an increase in: a) proportional turnover in community composition, b) the importance of environmental distance for explaining turnover in community composition and c) a decrease in environmental niche overlap between species indicating an increasing importance of competition for community composition. Our results support the idea that increasing species pool size increases the competition for available environmental niches, and thereby leads to a tighter connection between environmental factors and community composition.

Davallia repens and its close relatives have been identified as a species complex in this study because of the existence of continuously morphological variation. To decipher its evolutionary history, integrated methodologies were applied in this study including morphology, cytology, reproductive biology and molecular phylogeny. Analysis of morphological characters reveals several important discriminating characteristics, such as the shape of stipe scales, frond and indusium. Both diploid and polyploid forms are present in the complex and reproduce sexually and by apogamy, respectively. The incongruence between cpDNA and nDNA phylogeny indicates a hybrid origin for most polyploid individuals. Based on the present results, we hypothesize that there were at least two ancestral lineages distributed in the Malesian region. Through hybridization, polyploidization and apogamy, some polyploid genotypes dispersed outwards to shape the extant distribution.