Peripheral regions of the Alps are often overlooked in molecular studies, yet they may play a major role in shaping the current distribution of species and genetic lineages.
Europe.
Angiosperms (Primulaceae: Primula).
By focusing on the bear's ear (Primula auricula) complex as model species, we used genetic inferences for population genetic structure and performed genetic reconstructions, species delimitations and divergence time estimates in order to get a detailed view of its molecular evolution and current genetic structuring across the Alps sensu lato.
The Lombardian Alps and the southern eastern Alps are genetically distinct in the vicinity of the Adige valley. The northern and western Alps and their peripheries constitute a third clade and are separated by the siliceous central Alps. Within the latter, an additional cluster made of singular populations from the Dévoluy and Vercors regions is retrieved, likely reflecting a strong founder effect rather than an ancient divergence.
The biogeographic history P. auricula sensu lato pinpoints the importance of the peripheral regions in a phylogeographic context. Populations from northern peripheral regions exhibit long-lasting isolation and in situ survival during glaciations, followed by recolonisation into the central Alpine massif.
On the cover: Atlantic Flyingfish, Cheilopogon melanurus, Atlantic Yellowfin Tuna, Thunnus albacares, and Phycis chesteri, Longfin Hake all living in the Atlantic Ocean. Illustration credit: Kendra Mojica
The general dynamic model (GDM) of oceanic island biogeography proposes that evolutionary processes shift predictably with island ontogeny: opportunities for ecological speciation on young islands drive a rapid increase in diversity, which peaks on middle-aged islands, then declines on older islands as extinction increases. Most studies reporting support for the GDM have not assessed the evolutionary processes associated with these phases: ecological speciation on young islands, genetic drift within species on middle-aged islands, and finally, extinction on old islands. Here, we refine and extend the GDM by developing a set of testable predictions to show that the dominant evolutionary drivers of lineage divergence shift as islands progress through successive ontogenetic stages. We then assess whether patterns of genomic divergence are consistent with our predictions in an iconic flowering plant radiation.
The Mascarene archipelago (Rodrigues, Mauritius, Réunion) in the Indian Ocean.
Hibiscus section Lilibiscus (Malvaceae).
Using genome-wide data from 2bRAD sequencing, we conducted phylogenomic, population genomic and demographic analyses (approximate Bayesian computation in DIY-ABC) of six single-island endemic species sampled across the three islands.
On the youngest island, we detected signatures of ecological differentiation and high intraspecific gene flow, suggesting ecological speciation as the dominant driver of lineage divergence. On the middle-aged island, we found that recent population structure was shaped predominantly by genetic drift, with some evidence of ancient interspecific gene flow. On the oldest island, phylogenetic and population genetic patterns were consistent with lineage loss and increased phylogenetic distance, suggesting extinction as the dominant evolutionary force.
Our findings provide rare empirical support for the GDM's process-based predictions and offer a general framework for linking geomorphological change on oceanic islands to evolutionary dynamics in island systems. Our framework lays the groundwork for future population genetic studies to directly test the evolutionary processes shaping insular biodiversity.
We aimed to provide a molecular phylogeny of all currently known and described Labiotermes species to clarify taxonomic relationships, including the synonymy of Paracornitermes, in order to reconstruct the historical biogeography of the genus and investigate the role of specific biogeographic domains in its diversification.
South America.
Termite genus Labiotermes (Isoptera: Termitidae).
A dated Bayesian phylogeny was estimated using complete mitogenomes (14,985 bps) from all species. We performed biogeographic analyses using the BioGeoBEARS R package, testing 12 maximum likelihood models (six default models with and without a time-stratified dispersal matrix) across eight defined biogeographic units.
The genus Labiotermes originated approximately 21 Mya. Our phylogenetic analysis corroborated the synonymy of Paracornitermes with Labiotermes. The species L. labralis, L. guasu, and L. oreadicus formed a monophyletic group sister to all other Labiotermes. The top four best-fitting models (DIVALIKE+TS, DEC+TS, DEC+TS+j and DIVALIKE+TS+j) showed no significant differences in their estimations. The analysis revealed limited vicariance but multiple sympatric events, particularly within the western Brazilian savanna (Cerrado).
The Cerrado has been a key center of diversification for Labiotermes, with multiple dispersal events occurring over the last 10 Mya. These findings underscore the dynamic role of the Cerrado in shaping speciation patterns and highlight how Neotropical landscape evolution has profoundly influenced termite biogeography.
Human land use shapes landscapes and threatens avian biodiversity, yet its interaction with altitudinal gradients and the consequences for the assembly of long-distance migratory and sedentary bird communities remain poorly understood.
Southern France.
Avian breeding communities.
We examined the changes in the migratory–sedentary ratio (the relative proportion of migratory versus sedentary species) in avian breeding communities (5 × 5 km resolution) in response to a regional-scale altitudinal gradient (4000 m), in interaction with landscape structure (landscape heterogeneity and forest cover) and species richness.
We detected interactions between altitude, landscape structure and species richness influencing the migratory: sedentary ratio. This highlights the complex responses of avian communities to both abiotic and biotic drivers. Reduced habitat diversity and evenness at lower altitudes promoted the occurrence of migratory species. While increasing forest cover generally promotes bird species richness, our results showed that its effect on the migratory: sedentary ratio differ between altitudinal belts. Specifically, forest cover was associated with a decrease in the proportion of migratory species at lower altitudes but with an increase at higher altitudes. Finally, increasing total bird richness altered the equilibrium at lower altitudes, where the richest communities (above ~117 bird species) hosted more migratory species than expected from the regional pool. We hypothesise that adding migratory rather than sedentary species to the richest communities reduces competitive interactions for resources and limits niche saturation.
Understanding interactions among environmental drivers is essential for predicting the assemblage of avian communities. Our results identify specific environmental conditions that promote or threaten the richness of migratory and sedentary bird species and thus provide insights to inform conservation actions and policy decisions aimed at mitigating the impacts of environmental change on avian communities.
Test the response of mesopelagic zooplankton community composition and distributional ranges to dispersal potential and environment, in comparison with the epipelagic zooplankton community.
Epipelagic (0–200 m) and mesopelagic (200–1000 m) depth zones of the North Pacific Ocean.
Multicellular zooplankton.
Metabarcoding of two molecular markers (18S and COI) in combination with a global ocean circulation model, analysed by General Dissimilarity Modelling.
We found no significant difference in beta-diversity across three depth strata (0–200, 200–500, and 500–1000 m), calculated from the nMDS dispersion of samples within each stratum. Similarity in beta-diversity within the three depth strata indicates that epipelagic and mesopelagic zooplankton communities have similar levels of spatial turnover in species composition despite differences in the magnitude of environmental gradients and dispersal potential. There were no differences in the biogeographic ranges of taxa associated with each depth zone, but we observed larger temperature, salinity, and dissolved oxygen habitat envelopes as well as narrower potential food ranges for deeper-dwelling taxa. Ocean basin-scale community dissimilarity was correlated with dispersal distance, as well as with changes in temperature, salinity, dissolved oxygen concentration, and food flux. Combined Generalised Dissimilarity Models incorporating both dispersal potential and environmental habitat variables revealed that the environmental variables temperature and food flux had the strongest predictive power to explain community dissimilarity.
To investigate macroevolutionary and biogeographic patterns of chromosome number variation in ants (Formicidae), and to test whether chromosomal diversity is taxonomically structured, associated with species richness, varies with latitude, and accumulates over evolutionary time.
Global.
Ants (Hymenoptera: Formicidae).
We compiled 1203 records of haploid chromosome numbers from the Ant Chromosome Database, representing all major ant subfamilies. Taxonomic names were standardised and matched to a genus-level phylogeny on the basis of recent molecular studies. We quantified chromosomal diversity and analysed its relationship with clade age, species richness, absolute latitude, and latitudinal range using linear mixed-effects models (LMMs), generalised linear models (GLMs), generalised additive models (GAMs), and phylogenetic signal metrics (Blomberg's K, Pagel's λ). Sampling effort was incorporated to control for potential biases.
Haploid chromosome numbers ranged from 1 to 60, with a bimodal distribution structured by phylogeny. Chromosomal diversity was positively correlated with species richness and clade age. A non-linear latitudinal gradient was observed: diversity declined at higher latitudes but increased in regions with greater spatial heterogeneity. These patterns persisted after correcting for sampling intensity and taxonomic effects.
Chromosome number evolution in ants is shaped by a complex interplay between phylogenetic constraints, geographic gradients, and historical diversification. Chromosomal diversity appears to both reflect and potentially promote lineage diversification. Our findings highlight ants as a valuable system for exploring genome evolution in a macroecological and biogeographic context.
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