Nadia Bystriakova

NEOENDEMISM IN MADAGASCAN SCALY TREE FERNS RESULTS FROM RECENT, COINCIDENT DIVERSIFICATION BURSTS

Abstract More than 80% of Madagascars 12,000 plant species are endemic with the degree of endemism reaching as much as 95% in the scaly tree ferns, an important species rich component of Madagascars evergreen rainforests. Predominantly African or Asian ancestry and divergence times usually postdating the separation of Madagascar from the Gondwanan landmasses have been demonstrated for several Madagascan animal and angiosperm groups. However, evolutionary studies of rainforest-specific lineages are scarce and the ecological context of radiation events has rarely been investigated. Here, we examine the evolution of Madagascan tree ferns as a rainforest-specific model family, integrate results from bioclimatic niche analysis with a dated phylogenetic framework, and propose an evolutionary scenario casting new light on our knowledge of the evolution of large island endemic clades. We show that Madagascars extant tree fern diversity springs from three distinct ancestors independently colonizing Madagascar in the Miocene and that these three monophyletic clades diversified in three coincident radiation bursts during the Pliocene, reaching exceptionally high diversification rates and most likely responding to a common climatic trigger. Recent diversification bursts may thus have played a major role in the evolution of the extant Madagascan rainforest biome, which hence contains a significant number of young, neoendemic taxa.

Phylogeography of the Sino-Himalayan Fern Lepisorus clathratus on “The Roof of the World”

Background The Qinghai-Tibetan Plateau (QTP) and its southern and southeastern mountain ranges, Himalaya-Hengduan Mountains (HHM), are one of the most extensive habitats for alpine plants in the world. How ferns occurring in QTP and HHM changed their distribution ranges in response to Quaternary climatic oscillations remains almost unknown. Methodology and Results We employed sequences of two chloroplast DNA regions, rps4-trnS and trnL-trnF, to reconstruct phylogeography of the Sino-Himalayan fern Lepisorus clathratus, occurring mainly in the QTP and HHM. Individuals of this species have either dehiscent or indehiscent sporangia with the latter evolved from the plesiomorphic dehiscent forms. Based on a range-wide sampling, we detected 27 cpDNA haplotypes that were divided into five groups by network analyses. Populations in the Hengduan Mountains possess the highest genetic diversity, while a single haplogroup is detected across the north-central region. A distinct phylogeographical subdivision was detected between the Hengduan Mountains and north-central region by AMOVA analysis. The haplogroup distribution pattern, coalescence and AMOVA analysis suggest that a long term survival area (refugia) of the species was located in the Hengduan Mountains during glaciations, with probable range expansions into north-central regions during interglacial periods. Populations with indehiscent sporangium can carry private haplotypes and are inclined to maintain genetic homogeneity. One group with indehiscent sporangia most likely survived in situ on the QTP during glaciations. Conclusions/Significance This study for the first time sheds light on the response of alpine ferns in the QTP and HHM to the Quaternary climatic oscillations.

Sampling bias in geographic and environmental space and its effect on the predictive power of species distribution models

Despite ever-growing popularity of species distribution models (SDM), their performance under conditions of spatially biased data has rarely been studied in detail. Here we explore the effect of a known spatial bias on the predictive ability of Maxent models, using five species of the genus Asplenium with variable reproductive modes. The models were trained and tested on western and central European presence-only distributional data, first with random background and then with target-group background. Then we tested the models on an independent Ukrainian dataset of the same species, using the area under the curve (AUC) value as test statistic. We carried out a principal components analysis (PCA) on the collection localities of the individual species to explore the properties of their ecological niches. In all but one species, spatial bias in the distributional data resulted in poor performance of the Maxent models (trained on the European dataset and tested on the Ukrainian dataset). In all species correction for sampling bias resulted in significantly wider predicted climatic niches. Based on the results of the PCA, spatial bias resulted in environmental bias of variable degree. We argue that species reproductive biology should be taken into account when distributional data are analysed in terms of their suitability for species distribution modelling. The reported results will inform biodiversity conservation assessments, particularly those using data from natural history collections.

Present, past and future of the European rock fern Asplenium fontanum: combining distribution modelling and population genetics to study the effect of climate change on geographic range and genetic diversity

BACKGROUND AND AIMS Climate change is expected to alter the geographic range of many plant species dramatically. Predicting this response will be critical to managing the conservation of plant resources and the effects of invasive species. The aim of this study was to predict the response of temperate homosporous ferns to climate change. METHODS Genetic diversity and changes in distribution range were inferred for the diploid rock fern Asplenium fontanum along a South-North transect, extending from its putative last glacial maximum (LGM) refugia in southern France towards southern Germany and eastern-central France. This study reconciles observations from distribution models and phylogeographic analyses derived from plastid and nuclear diversity. KEY RESULTS Genetic diversity distribution and niche modelling propose that genetic diversity accumulates in the LGM climate refugium in southern France with the formation of a diversity gradient reflecting a slow, post-LGM range expansion towards the current distribution range. Evidence supports the ferns preference for outcrossing, contradicting the expectation that homosporous ferns would populate new sites by single-spore colonization. Prediction of climate and distribution range change suggests that a dramatic loss of range and genetic diversity in this fern is possible. The observed migration is best described by the phalanx expansion model. CONCLUSIONS The results suggest that homosporous ferns reproducing preferentially by outcrossing accumulate genetic diversity primarily in LGM climate refugia and may be threatened if these areas disappear due to global climate change.

Bumblebees, climate and glaciers across the Tibetan plateau (Apidae: Bombus Latreille)

The Tibetan plateau and its immediately surrounding mountains include the greatest hotspot of diversity worldwide for bumblebees, which are among the most important pollinators in temperate ecosystems. We make the first quantitative description of variation in the species composition of alpine social bumblebee faunas across the Tibetan plateau, for 44 species in 124 of the 307 one-degree grid cells. Data were compiled from field surveys, published sources and museum collections. Sampling effort could not be standardized across the region so our inferences have to be provisional. Faunal variation is described using detrended correspondence analysis (DCA); the faunal variation explained by climate variation is described using canonical correlation analysis (CCA); and the contribution of the climate data to the explanation is assessed using Procrustes analysis. Results show: (1) a particularly distinct group of endemic Himalayan faunas in the south; (2) a group of Tibetan interior faunas, with connections to faunas in the north-west in the Hindu Kush, Pamir and Tian Shan; and (3) a group of faunas in north-eastern Qinghai and Gansu, with connections to faunas to the north-east in Mongolia. The eastern and southern faunas in wetter habitats appear to be closer to equilibrium with climate factors, whereas some western faunas in more arid habitats appear further from equilibrium with the measured climate factors. One possibility is that these western faunas may depend on highly localized factors for mitigating the low precipitation over much of this region, and particularly on continuous summer streams with meltwater from distant permanent glaciers or high-ridge precipitation. Consequently, conservation threats to Tibetan bumblebees now include climate change causing loss of permanent streams in the west as well as the over-grazing documented in the east, threats that have not been major concerns for bumblebee conservation elsewhere.

Discovery of a diverse cave flora in China

Few studies document plants in caves. Our field observations of a widespread and seemingly angiosperm-rich cave flora in SW China lead us to test the following hypotheses, 1) SW China caves contain a diverse vascular plant flora, 2) that this is a relic of a largely absent forest type lacking endemic species, and 3) that the light environment plants occupy in caves is not distinct from non-cave habitats. To do so we surveyed 61 caves and used species accumulation curves (SAC) to estimate the total diversity of this flora and used a subsample of 14 caves to characterise the light environment. We used regional floras and existing conservation assessments to evaluate the conservation value of this flora. We used observations on human disturbance within caves to evaluate anthropogenic activities. Four-hundred-and-eighteen vascular plant species were documented with SACs predicting a total diversity of 529–846. Ninety-three percent of the species documented are known karst forest species, 7% are endemic to caves and 81% of the species are angiosperms. We demonstrate that the light environment in caves is distinct to that of terrestrial habitats and that a subset of the flora likely grow in the lowest light levels documented for vascularised plants. Our results suggest that the proportion of species threatened with extinction is like that for the terrestrial habitat and that almost half of the entrance caverns sampled showed signs of human disturbance. We believe that this is the first time that such an extensive sample of cave flora has been undertaken and that such a diverse vascular plant flora has been observed in caves which we predict occurs elsewhere in SE Asia. We argue that the cave flora is an extension of the karst forest understory present prior to catastrophic deforestation in the 20thC. We suggest that within SW China caves serve as both refuges and a valuable source of germplasm for the restoration of karst forest. We also propose that caves represent a distinct habitat for plants that is most similar to that of the forest understory, but distinct with respect to the absence of trees, leaf litter, root mats, higher levels of atmospheric CO2, and lower diurnal and annual variation in temperature and humidity. We highlight tourism, agriculture and the absence of legislated protection of caves as the main current threats to this flora.

Key environmental determinants of global and regional richness and endemism patterns for a wild bee subfamily

Reports of world-wide decline of pollinators, and of bees in particular, raise increasing concerns about maintenance of pollination interactions. While local factors of bee decline are relatively well known and potential mitigation strategies at the landscape scale have been outlined, the regional and continental-scale threats to bee diversity have only been marginally explored. Here we document large-scale spatial patterns for a representative bee subfamily, the determinants of its species richness, and assess major threats to these pollinators. Using a comprehensive global dataset of Colletinae (genera Colletes, also called “polyester” or “cellophane” bees for their underground nests lined with a polyester secretion, and Mourecotelles), a species-rich subfamily whose organismal and physiological ecology is representative of many bees, we measured species richness and endemism on global to continental scales. We explored the relationships between bee species richness and potential environmental stress factors grouped into three categories: contemporary climate, habitat heterogeneity, and anthropogenic pressure. Bees of the subfamily Colletinae demonstrate the reversed latitudinal gradient in species richness and endemism suggested for bees; the highest species richness of Colletinae was found between 30° and 50° latitude in both the northern and southern hemispheres. Centres of endemism largely overlapped with those of species richness. The importance of the Greater Cape Floristic Region, previously identified as a centre of richness and endemism of bees, was confirmed for Colletinae. On the global scale, present-day climate was a significant predictor of species richness as was flowering plant diversity represented by vascular plant species richness and centres of plant diversity. Our main conclusion is that climate change constitutes a potential threat to bee diversity, as does declining diversity of vascular plants. However, a significant overlap between centres of bee richness and plant diversity might increase chances for developing conservation strategies.