Basin fragmentation during dry climatic periods can divide drainage systems into isolated endorheic units, profoundly affecting the genetic structure of freshwater organisms. This study aims to perform a comparative phylogeographic analysis incorporating different freshwater fish species where we assessed the roles of isolation by distance (IBD), barriers (IBB) and environment (IBE) in shaping the genetic diversity of seven neotropical fish species using mitochondrial DNA.
Argentina, Brazil and Uruguay endorheic and exorheic basins.
Hypostomus cordovae, Rineloricaria catamarcensis, Oligosarcus jenynsii and Hoplisoma longipinne.
Samples were collected across multiple localities for each species and grouped based on basin type (endorheic vs. exorheic), hydrographic system and environmental criteria. Mitochondrial DNA (COI or D-loop) was sequenced, and phylogenetic reconstructions, haplotype networks, genetic diversity indices and population structure analyses were performed. Distance-based Redundancy Analysis (db-RDA) was used to evaluate the influence of isolation by distance (IBD), barriers (IBB) and environment (IBE) on genetic structuring. Environmental variables such as altitude, latitude and turbidity, vegetation cover, and land surface temperature were derived from remote sensing data.
Basin fragmentation (IBB) is the main driver of genetic divergence in Hypostomus cordovae and Hoplisoma longipinne. Geographic distance (IBD) significantly influenced H. cordovae, Rineloricaria catamarcensis and Oligosarcus jenynsii (Continental Group), while environmental factors such as altitude (IBE) contributed to the structure of H. longipinne and O. jenynsii.
These findings emphasise the importance of adopting an integrative approach to understanding genetic diversification in freshwater organisms. They highlight the complex interplay of historical, geographical and ecological processes in fragmented river systems. Furthermore, they underscore the conservation significance of isolated endorheic basins as reservoirs of unique genetic lineages.
To investigate how the El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) influence zooplankton diversity and community structure in the central Chile coastal upwelling system, focusing on long-term changes in species composition and abundance under shifting climatic conditions.
Eastern South Pacific off central Chile, covering an area of approximately 38,500 km2.
2003–2020.
Zooplankton, with emphasis on dominant groups such as copepods, jellyfish, radiolarians, siphonophores and cladocerans.
We analysed an 18-year time series of zooplankton abundance and composition. Partial Canonical Correspondence Analysis (pCCA) examined relationships between zooplankton groups, the PDO and environmental variables (sea surface temperature, dissolved oxygen, wind). Threshold Indicator Taxa Analysis (TITAN) identified taxa characteristic of warm (PDO+) or cold (PDO–) phases, clarifying their roles as either sensitive or tolerant indicators of climatic shifts.
Warm phases (PDO+) were dominated by jellyfish, siphonophores and pteropods, whereas cold phases (PDO–) favoured radiolarians and cladocerans. Copepods, the most abundant group, exhibited notable fluctuations across climate phases. Zooplankton diversity showed an ‘in-phase’ response to climatic oscillations, indicating strong links between decadal-scale climate regimes and ecosystem dynamics in this productive upwelling region.
Our findings underscore the sensitivity of marine zooplankton communities to climate variability, with distinct PDO phases exerting significant influence on zooplankton composition and diversity. Recognising key indicator taxa in warm versus cold periods is crucial for ecosystem management and developing indicator-based monitoring programs. Continued long-term surveys will be essential to anticipate future shifts in marine biodiversity under ongoing climate change.
Endemism is a critical aspect of biological diversity, yet the mechanisms driving it remain unclear. The leading hypothesis posits that prolonged environmental stability fosters speciation and reduces extinction rates, promoting endemism. While terrestrial studies exist, marine environments remain underexplored. This study analysed the global distribution and drivers of phylogenetic endemism in two marine taxa: Calanidae copepods and Blenniidae fish.
Global.
From the Last Glacial Maximum (LGM, past 24,000 years) to the current period.
Calanidae copepods and Blenniidae fish.
We assessed taxonomic and phylogenetic diversity, endemism and areas of paleo- and neo-endemism using Categorical Analysis of Neo- and Paleo-Endemism and Piecewise Structural Equation Modelling to evaluate the influence of present-day and historical environmental variables.
Results showed consistent diversity patterns and significant endemism hotspots, with Calanidae in the Southern Hemisphere and Blenniidae in the Northern Hemisphere. Tropical regions, particularly the Indonesian-Australian Archipelago (IAA), exhibited high species richness and endemism for both groups. Paleo-endemism was observed in the Pacific for Calanidae and the IAA for Blenniidae, suggesting that these areas are either relict diversity centres or diversification hubs.
The Mediterranean and Caribbean Seas emerged as biodiversity cradles for Calanidae and Blenniidae respectively. Phylogenetic endemism is driven by both historical and contemporary factors, with centres of endemism emerging in regions where past environmental fluctuations have been moderate (hypothesis 1) and where cold, productive ocean currents foster the development of endemic areas (hypothesis 2). These findings underscore the importance of historical stability in ocean temperatures in shaping phylogenetic endemism, indicating that long-term environmental stability sustains marine endemism.
To test how evolutionary processes of spiders in mountain ranges of eastern China were in response to environmental changes, we analyze the correlation between diversification of the Pardosa laura species complex (Araneae, Lycosidae) and historical climates and mountains in this region.
We reconstruct phylogenetic relationships and patterns of phylogeography and genetic diversity using mtDNA data from samples spanning the full range of the species complex P. laura in eastern China.
The P. laura species complex clustered into four lineages: Lineage I includes five haplotypes from the areas to the north of the Yinshan-Yanshan Mountains; Lineage II consists of 23 haplotypes from the areas between the Qinling Mountains–Huaihe River Line and the Nanling Mountains; Lineage III and IV are composed of 21 and 62 haplotypes, respectively, from the areas between the Yinshan-Yanshan Mountains and the Nanling Mountains. Each lineage corresponds to that, grouped from haplotype network analyses, with the same geographic distribution areas. All four lineages initially diversified during about 1.43 and 0.24 Ma ago (Ma) in relation to the Pleistocene glacial-inglacial cycles. The biogeographic reconstructions suggest that the species complex P. laura most likely originated in central China around 7.68 (11.17–4.85) Ma in relation to the recent (approximately 8 Ma) expansion of grasslands and retraction of forests. The inter-colony dispersal between central China and northeastern China occurred during the late Neogene, between around 7.68 and 3.14 Ma. Central China is an important dispersal center, with dispersal to southwestern and northern China between the late Pliocene and middle Pleistocene, approximately 3.14–2.89 and 2.89–1.43 Ma, respectively.
The contemporary genetic structure of the P. laura species complex presents a high correlation between lineages and geographic distribution. The historical phylogeographic patterns suggested that the late Cenozoic climate changes and the mountainous corridors and isolation events, as well as the lineage dispersals and ecological adaptations shaped the diversification of a spider species complex in eastern China over long timescales.
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