To develop the palaeoecological and palaeoclimatic history of Maplecrest Fen, Greene County, NY.
Catskill Mountains, New York.
13,500 calendar years to present (ybp, present = 1950).
Angiosperms, gymnosperms and bryophytes.
We used pollen and spore analysis, macrofossil analysis, loss-on-ignition (LOI) and X-ray fluorescence (XRF) analysis of a 7.8 m sediment core from the Fen along with AMS radiocarbon dates retrieved from the identified terrestrial macrofossils.
Late-glacial and Holocene vegetational change from ice withdrawal reveals the development of a shallow lake and then fen to the present. The boreal spruce (Picea), fir (Abies) and paper birch ((Betula papyrifera) pollen signature near the base of the core (Zone M2) suggest a Younger Dryas (YD) signal overtopping warmer Allerod aged basal sediments. The early Holocene white pine (Pinus strobus) is followed by increases in hemlock (Tsuga) and beech (Fagus), ushering in a moister climate. About 5200 ybp drought is indicated by the well-known hemlock biostratigraphic decline in the Northeast. Drepanocladus moss and stonewort (Chara) shift to sedges (Carex) and violets (Viola) locally present. For the next 5000 years, the vegetation will remain relatively stable with lower temperatures suggested by the return of spruce and fir. Ragweed (Ambrosia) rise along with other weedy taxa marks European settlement near the top 50 cm of the core, along with a striking increase in anthropogenic lead, as seen using X-ray fluorescence.
Deglaciation began in the Catskills at a high elevation about 13,500 years ago and recession of ice from the Laurentide margin proceeded at about 0.1 km/year. Temperature shifts promoted changes in the boreal forest including warming and cooling, and drought and wetter intervals both appear in the Holocene history but do not appear to be easily forecast as climate continues to warm.
The changing frequency and intensity of climatic extremes due to climate change can have sudden and adverse impacts on the distribution of species. While species distribution modelling is a vital tool in ecological applications, current approaches fail to fully capture the distribution of climatic extremes, particularly of rare events with the most disruptive potential. Especially at the edges of species' ranges, where conditions are already less favourable, predictions might be inaccurate when these extremes are not well represented.
Europe.
Tree species.
We present a novel approach to integrate extreme events into species distribution models based on the generalised extreme value (GEV) distribution. This distribution, following from the extreme value theory has been established as a valuable tool in analysing climatic extremes, both in an ecological context and beyond. The approach relying on the GEV distribution is broadly applicable, readily transferable across species and relies on widely available data. We demonstrate the efficacy of our approach for 28 European tree species, illustrating its superior ability to fully capture the distribution of climatic extremes compared to state-of-the-art methods.
We found that incorporating parameters on climatic extremes derived from the GEV distribution increased model performance (AICmodel) and characterised range edges more accurately (AUCedge) compared to competing approaches. However, general AUC values were only marginally increased across the species and study period analysed. Overall, the GEV model predicted a narrower niche for the species included in this study.
Incorporating climatic extremes can impact spatial predictions of species distribution models, especially at range margins. We found that using the GEV distribution to characterise extreme variables in SDMs yields the best performance at these distribution edges. Given the importance of range edges for species conservation, a detailed inclusion of extremes in SDMs employed for those applications will help ensure robust conclusions.
As range maps do not imply the continuous presence of species across their extents—and are commonly developed with species conservation in mind—their underlying assumptions unsurprisingly lead to richness overpredictions for a given area. Despite this expectation, species richness extracted from overlapping species range maps continues to be used in macroecological models (MEMs) of species richness. In this paper, we demonstrate the various implications of using range map richness in MEMs.
Puerto Rico.
Anolis lizards.
We used random forests to build two MEMs of Puerto Rico Anolis species richness: (a) using richness extracted from superimposed species range maps and (b) using biodiversity surveys conducted by the Puerto Rico non-profit, Para la Naturaleza. We then compare richness predictions, variable importance and evaluation metrics between the two models.
We demonstrate how (1) using range map richness in MEMs results in richness overprediction, (2) variable importance taken from MEMs built with range map richness may be unreliable or indicative of variable importance at a coarser spatial scale and (3) correlation metrics used for evaluating MEMs are potentially misleading. Through this work, we shed light on the implications of using range map species richness in MEMs.
Tardigrades are important members of Antarctic metazoan communities with many endemic species. Major biogeographic patterns of Antarctic fauna have been identified, in particular regarding the zonation across the Gressitt line, dividing Continental and Peninsular Antarctica. Evidences suggest that Antarctic tardigrades follow this zonation too, but this has never been rigorously tested.
Limnoterrestrial ecosystems of Antarctica.
1950 to Present.
Tardigrades.
Records of tardigrades from Antarctica were collected and their taxonomy and coordinates harmonised. Alpha and Beta diversity measures were calculated and compared across different Antarctica biogeographic areas, in particular across the Gressitt line. Analyses were repeated at different spatial scales to ensure their robustness.
Tardigrades communities are different both in terms of alpha and beta diversity across the Gressitt line. Results were consistent across the analyses at different spatial scales. Taxa richness was higher in the Antarctic Peninsula compared to the Continental Antarctica. Sampling effort had a substantial effect on the measured richness. Despite having a significant effect, Gressitt line side and biogeographic areas explained a low amount of variance.
The presence of a different Tardigrade communities composition across the Gressitt line is supported, and a geographical structure is present also at smaller scales. This geographic structuring suggests local endemisms and calls for attention to eventual effects of climate change on tardigrades communities. Faunistic data on Antarctica is still far from being exhaustive and Linnean and Wallacean biodiversity shortfalls are the two most immediate issues to be solved to have a more reliable estimation of the true Antarctic tardigrades biodiversity.
The aim of the current study is to conduct a comprehensive phylogenetic analysis of the genus Arbacia to elucidate the evolution and phylogenetic relationships among all extant species and reevaluate the presence of geographic structure within species that have wide, fragmented distributions.
Specimens of Arbacia were collected from 34 localities spanning the Atlantic and Pacific Oceans, and the Mediterranean Sea.
We obtained sequences from three mitochondrial markers (COI, 16S and the control region and adjacent tRNAs) and two nuclear markers (28S and 18S; the latter ultimately excluded from the final analyses). Phylogenetic trees were constructed using maximum likelihood and Bayesian inference approaches. A time-calibrated phylogenetic tree was inferred using a relaxed Bayesian molecular clock and three fossil calibration points.
Our analysis supports the monophyly of the genus Arbacia, including the species Arbacia nigra (previously assigned to the monotypic genus Tetrapygus). The new phylogenetic topology suggests an alternative biogeographic scenario of initial divergence between Atlantic and Pacific subclades occurring approximately 9 million years ago. The dispersal and subsequent diversification of the Pacific subclade to the southeast Pacific coincides with the onset of glacial and interglacial cycles in Patagonia. In the Atlantic subclade, the split between A. punctulata and A. lixula occurred 3.01–6.30 (median 3.74 million years ago), possibly associated with the strengthening of the Gulf Stream current connecting the western and eastern Atlantic. Our study also reveals significant genetic and phylogeographic structures within both Atlantic species, indicating ongoing differentiation processes between populations.
Our study provides valuable insights into the evolutionary history and biogeography of the genus Arbacia and highlights the complex interplay between historical climate changes and oceanic currents in shaping the distribution and diversification of echinoids in the Atlantic and Pacific Oceans.
On the cover: Andryala laevitomentosa (Asteraceae) reproduces almost exclusively by vegetative reproduction and its clones are among the oldest living individuals on Earth. Mt. Pietrosul Brostenilor, Eastern Carpathians Mountains, Romania, July 2015. Photo credit: Peter Turis.
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