The Neogene fossil record of Pinus canariensis C.Sm ex DC. suggests a wider past distribution in Europe, but due to extirpation by past climatic events, today this taxon is restricted to the Canary Islands. Remarkably, the putative oldest P. canariensis fossil for the Canary Islands, found in Gran Canaria is 13.3–13.0 Ma. This palaeobiogeographical information has been cited as proof of the deep-time presence of conifers, the genus Pinus L., P. canariensis and the pine forest ecosystems in the Canary Islands, but also to justify the long-term evolution of P. canariensis within an active insular volcanic environment. Here we present a re-evaluation of the oldest Pinus fossil from the Canary Island.
Gran Canaria, Canary Islands, Spain.
Pinus canariensis C.Sm ex DC.
We compiled a citation record for the mentions of the ‘bark fossil’ and conducted a review of the specimen. We compared it with extant P. canariensis and with pyroclasts.
The analysis of the specimen demonstrates that it lacks morphological or anatomical characters to identify as a bark or even as a plant fossil. The specimen is best interpreted as a lapilli-sized tube pumice, highly altered by mineral deposition promoted by the percolating hydrothermal water.
The oldest reliable Pinus fossils from the Canary Islands are 3.9–3.1 Ma and ca. 9 to 10 Ma younger than previously claimed. When did Pinus arrive at the Canary Islands is unknown, but this biogeographical question can be approached via focused volcano-stratigraphical and palaeobotanical research in this Archipelago.
Several lines of evidence have noted that open vegetation biomes in the Neotropics are younger than moist forests, leading us to question which historical processes shaped the current species distribution patterns in these new biome formations. Here we investigate the temporal patterns of speciation and colonisation from surrounding biomes (Amazonia, Atlantic Forest and Cerrado) in the Caatinga historical assembly of squamate species, to understand the role of geomorphological events and climate change in driving its diversification.
Neotropics.
Squamata (snakes, lizards and amphisbaenians).
We used a phylogenetic tree and occurrence data for 459 squamate species distributed throughout four different biomes (Amazonia, Atlantic Forest, Cerrado and Caatinga) to reconstruct ancestral geographic ranges using the R package BioGeoBEARS. We used BAMM to estimate the rates of species diversification.
Our results indicate that the current diversity patterns of squamates in the Caatinga were a result of pervasive faunal exchanges from adjacent biomes since the Paleogene, with similar numbers of dispersal events in each source area. The Neogene period was determinant in the diversification process, leading to the current assembly patterns of this group in the Caatinga.
The landscape transformation and climate change that increased aridity in northeastern Brazil probably shaped the diversification of dry-adapted squamates in the Caatinga, like tropidurid lizards. However, the Pleistocene climatic fluctuations associated with the highly heterogeneous gradients of topography, geology, soils, climatic conditions, and different vegetation physiognomies could have facilitated faunal exchange with their neighbouring forested biomes, explaining the current presence of some typical forested lineages inside the Caatinga domain and help us to clarify the current distribution patterns of squamates in this region.
Greenland is among the most rapidly changing regions on Earth, with climate change having a profound impact on its terrestrial ecosystems. Here, moss-associated diatoms hold great potential as sensitive biological indicators to monitor responses to climate change, but their diversity, community structure and biogeography remain virtually unexplored. Our study, thus, aims to (1) explore the diversity and community structure of moss-associated diatoms in Greenland and (2) assess the environmental and spatial variables driving their geographic distribution, establishing a baseline for their use as bio-indicators of climate change.
Greenland, spanning a gradient from high to subarctic regions.
Moss-associated diatoms (Bacillariophyta).
LM and SEM analysis was conducted on 175 terrestrial moss samples collected from preserved herbarium material and fresh samples (1988–2021) from high, low and subarctic localities in Greenland. Biogeographical distributions, biodiversity patterns and community structure were examined in relation to environmental and spatial factors using Kruskal–Wallis, Spearman's Rank, ordination, SIMPROF and variation partitioning analyses.
A total of 544 diatom taxa (66 genera) were identified, with nearly half potentially new to science. Community structure was predominantly influenced by moisture, pH, conductivity and temperature. Local variation in microclimate and bedrock, thus, explained more variation in the diatom communities than latitude-related environmental gradients. Surprisingly, temperature had a negative impact on diatom richness, probably due to its adverse effect on moisture, highlighting the vulnerability of Arctic moss diatoms to global warming.
This study provides the first comprehensive analysis of Greenland's moss-associated diatoms, highlighting their high diversity and sensitivity to environmental changes. Our findings underscore their potential as indicators for monitoring climate change in the Arctic, with moisture, pH, conductivity and temperature being critical factors influencing their communities, laying the groundwork for future research and monitoring efforts.
Phylogenetic niche conservatism predicts that species tend to retain the ecological traits of their ancestors. Accordingly, communities developing under more stressful conditions should be more strongly structured by environmental filtering than communities in less stressful conditions, and thus would exhibit lower phylogenetic dispersion and diversity. Elevational gradients offer unique opportunities to studying, among others, phylogenetic structure patterns across climatic gradients because the geographic distance of the same length of a climatic gradient is much shorter along an elevational gradient than along a latitudinal gradient. Here, we examine the relationship of phylogenetic diversity and dispersion of angiosperms in local communities with elevation and climate along a temperate elevational gradient.
The Siskiyou Mountains in the western United States.
Angiosperms.
Phylogenetic diversity and dispersion of angiosperms in 236 local communities distributed along an elevational gradient ranging from 533 to 2103 m were related with elevation, mean annual temperature and annual precipitation using correlation and regression analyses. Variation partitioning analysis was conducted to assess the relative importance of temperature and precipitation in affecting phylogenetic diversity and dispersion.
Phylogenetic diversity and dispersion in angiosperm communities generally decrease with increasing elevation but the opposite pattern is observed in the middle segment of the elevational gradient. The patterns are more conspicuous for herbaceous plants than for woody plants. Temperature is more strongly associated with phylogenetic diversity and dispersion of angiosperm communities compared to precipitation.
The patterns of phylogenetic diversity and dispersion in angiosperm communities along the elevational gradient in the Siskiyou Mountains are consistent with the tropical niche conservatism hypothesis, which predicts that communities in areas with lower temperature and precipitation would have lower phylogenetic diversity and dispersion.
On the cover: Spix's Warbling-Antbird (Hypocnemis striata) is an understory forest bird, formerly considered part of a polytypic species complex, limited by major Amazonian rivers. Photo credit: Pablo Vieira Cerqueira.
The realised niches of species change following environmental and distributional shifts. Still, the magnitude of niche change and its consequences are determined by how different species cope with environmental changes, which ultimately depends on their ecology and traits. We assessed how environmental and distributional shifts have led to changes in the realised breeding niches of 121 species of North American birds over the last four decades and how the magnitude of niche change was associated with species traits.
North America.
Birds.
We calculated geographic and niche overlap, breadth and shift, and estimated the temporal trends of the different niche metrics from 1980 to 2018 for each species. The slopes of these temporal trends were then modelled as a function of species traits using Bayesian models that accounted for phylogenetic relatedness and the uncertainty of the temporal slopes.
We found that the niche of 57% of the bird species diverged through time as they experienced widespread environmental change, including changes in both niche breadth and position. Most niches expanded due to increasing environmental variability within their ranges, but habitat specialists showed a tendency for niche contraction. Niche shifts were larger in species that live in habitats with denser vegetation cover. However, species showing larger average geographical shifts were able to track their reference niche more effectively.
Bird species were in general increasingly exposed to higher environmental variation that led to changes in their realised niches over a relatively short time span (four decades), while the niches of many others remained stable. The differences in the magnitude of niche change were to some extent related to species traits, providing clues about how different species respond to widespread environmental change in both geographical and niche space.
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