Adrien Favre

The role of the uplift of the Qinghai-Tibetan Plateau for the evolution of Tibetan biotas

Biodiversity is unevenly distributed on Earth and hotspots of biodiversity are often associated with areas that have undergone orogenic activity during recent geological history (i.e. tens of millions of years). Understanding the underlying processes that have driven the accumulation of species in some areas and not in others may help guide prioritization in conservation and may facilitate forecasts on ecosystem services under future climate conditions. Consequently, the study of the origin and evolution of biodiversity in mountain systems has motivated growing scientific interest. Despite an increasing number of studies, the origin and evolution of diversity hotspots associated with the Qinghai‐Tibetan Plateau (QTP) remains poorly understood. We review literature related to the diversification of organisms linked to the uplift of the QTP. To promote hypothesis‐based research, we provide a geological and palaeoclimatic scenario for the region of the QTP and argue that further studies would benefit from providing a complete set of complementary analyses (molecular dating, biogeographic, and diversification rates analyses) to test for a link between organismic diversification and past geological and climatic changes in this region. In general, we found that the contribution of biological interchange between the QTP and other hotspots of biodiversity has not been sufficiently studied to date. Finally, we suggest that the biological consequences of the uplift of the QTP would be best understood using a meta‐analysis approach, encompassing studies on a variety of organisms (plants and animals) from diverse habitats (forests, meadows, rivers), and thermal belts (montane, subalpine, alpine, nival). Since the species diversity in the QTP region is better documented for some organismic groups than for others, we suggest that baseline taxonomic work should be promoted.

GENETIC AND ECOLOGICAL DIFFERENTIATION IN THE HYBRIDIZING CAMPIONS SILENE DIOICA AND S. LATIFOLIA

Abstract Ecological differentiation is a major contributor to the generation and maintenance of biological diversity. We investigated habitat differentiation between and within sites in the fully cross-fertile and hybridizing Silene dioica and S. latifolia using amplified fragment length polymorphisms (AFLP) profiles and corresponding vegetation relevés around individual plants. Nineteen study sites in the Swiss Alps included pure sites and contact sites (both taxa present within 30 m). In pure sites and at contact sites, the two taxa showed consistently differentiated AFLP banding patterns across regions but few discriminating bands. This indicates that although the two taxa are weakly differentiated, current introgression has not led to genome-wide admixture. Only three putative early generation hybrids were detected at contact sites. The habitats of the two taxa differed between pure sites with S. dioica occurring in moister, colder, and less-disturbed sites than S. latifolia. However, asymmetric habitat overlap was evident within contact sites found in intermediate conditions that were more similar to S. latifolia sites. This situation might favor introgression from S. dioica into S. latifolia. Evidence for habitat–genotype associations within contact sites was weak making habitat-mediated selection against intermediate phenotypes of hybrids unlikely in the contact sites investigated. We suggest that other reproductive barriers together with dispersal limitation contribute to the rarity of early generation hybrids.

Two new genera of Gentianinae (Gentianaceae): Sinogentiana and Kuepferia supported by molecular phylogenetic evidence

Subtribe Gentianinae, encompassing Gentiana, Tripterospermum, Metagentiana and Crawfurdia, represents one of the most species-rich clades of Gentianaceae. Only a few taxonomic uncertainties have remained at generic level in subtribe Gentianinae: the inclusion of Gentiana sect. Otophora in Gentiana, and the polyphyletic nature of Metagentiana. In both cases, data were lacking in earlier studies to resolve ambiguities and provide the baseline for a solid taxonomic treatment of these lineages. For the present study, we increased the number of species sequenced for Gentiana sect. Otophora and Metagentiana, using a combination of nuclear (ITS) and plastid (trnL-F, atpB-rbcL) markers. We reconstructed phylogenetic relationships in Gentianinae conducting maximum likelihood and Bayesian analyses. Our results show that Gentiana sect. Otophora is monophyletic and more closely related to Metagentiana than to Gentiana. We suggest excluding Gentiana sect. Otophora from Gentiana and elevating this group to the rank of genus described here under the name Kuepferia. Metagentiana is monophyletic when excluding two species, M striata and M souliei, here described as the new genus Sinogentiana.

Spatio-temporal evolution of Allium L. in the Qinghai-Tibet-Plateau region:Immigration and in situ radiation

A plethora of studies investigating the origin and evolution of diverse mountain taxa has assumed a causal link between geological processes (orogenesis) and a biological response (diversification). Yet, a substantial delay (up to 30 Myr) between the start of orogenesis and diversification is often observed. Evolutionary biologists should therefore identify alternative drivers of diversification and maintenance of biodiversity in mountain systems. Using phylogenetic, biogeographic, and diversification rate analyses, we could identify two independent processes that most likely explain the diversity of the widespread genus Allium in the Qinghai–Tibet Plateau (QTP) region: (1) While the QTP-related taxa of the subgenus Melanocrommyum diversified in situ, (2) QTP-related taxa of other subgenera migrated into the QTP from multiple source areas. Furthermore, shifts in diversification rates within Allium could not be attributed spatially and temporally to the uplift history of the QTP region. Instead, global cooling and climate oscillations in the Quaternary were major contributors to increased speciation rates in three clades of Allium. Our study therefore adds to the growing evidence supporting the “mountain-geo-biodiversity hypothesis”, which highlights the role of climate oscillations for the diversification of mountain organisms.

Evolutionary radiations in the species-rich mountain genus Saxifraga L.

BackgroundA large number of taxa have undergone evolutionary radiations in mountainous areas, rendering alpine systems particularly suitable to study the extrinsic and intrinsic factors that have shaped diversification patterns in plants. The species-rich genus Saxifraga L. is widely distributed throughout the Northern Hemisphere, with high species numbers in the regions adjacent to the Qinghai-Tibet Plateau (QTP) in particular the Hengduan Mountains and the Himalayas. Using a dataset of 297 taxa (representing at least 60% of extant Saxifraga species), we explored the variation of infrageneric diversification rates. In addition, we used state-dependent speciation and extinction models to test the effects of geographic distribution in the Hengduan Mountains and the entire QTP region as well as of two morphological traits (cushion habit and specialized lime-secreting glands, so-called hydathodes) on the diversification of this genus.ResultsWe detected two to three rate shifts across the Saxifraga phylogeny and two of these shifts led to radiations within two large subclades of Saxifraga, sect. Ciliatae Haworth subsect. Hirculoideae Engl. & Irmsch. and sect. Porphyrion Tausch subsect. Kabschia Engl. GEOSSE analyses showed that presence in the Hengduan Mountains had a positive effect on diversification across Saxifraga. Influence of these mountains was strongest in Saxifraga sect. Ciliatae subsect. Hirculoideae given its pronounced distribution there, and thus the radiation in this group can be classified at least partially as geographic. In contrast, the evolution of the cushion life form and lime-secreting hydathodes had positive effects on diversification only in selected Saxifraga sections, including sect. Porphyrion subsect. Kabschia. We therefore argue that radiation in this group was likely adaptive.ConclusionsOur study underlines the complexity of processes and factors underpinning plant radiations: Even in closely related lineages occupying the same life zone, shifts in diversification are not necessarily governed by similar factors. In conclusion, alpine plant radiations result from a complex interaction among geographical settings and/or climatic modifications providing key opportunities for diversification as well as the evolution of key innovations.

Do flower color and floral scent of silene species affect host preference of Hadena bicruris, a seed-eating pollinator, under field conditions?

Specialization in plant–insect interactions is an important driver of evolutionary divergence; yet, plant traits mediating such interactions are poorly understood. In this study, we investigated how flower color and floral scent are related to seed predation by a seed-eating pollinator. We used field-transplanted recombinant F2 hybrids between Silene latifolia and S. dioica that are the preferred and alternative hosts of the moth Hadena bicruris and crosses within these species for comparison. We scored seed predation and flower color and analyzed floral scent. Pinker S. dioica-like flowers and emission of α-pinene decreased the odds of seed predation while emission of benzyl acetate and 6-methyl-5-hepten-2-one increased the odds of seed predation. Emission of these compounds did not differ significantly between the two Silene species. Our results suggest that flower color plays an important role in the specific interaction of H. bicruris with its preferred host S. latifolia. The compounds α-pinene, benzyl acetate and 6-methyl-5-hepten-2-one could represent non-specific deterrents and attractants to ovipositing moths. Alternatively, emission of these compounds could be related to herbivory or pathogen attack and act as a signal for host quality. This would weaken the predictability of the plants costs and benefits of the interaction and act to maintain an imperfect degree of specialization.

Increasing phylogenetic support for explosively radiating taxa: The promise of high‐throughput sequencing for Oxytropis (Fabaceae)

The origin and evolution of alpine biota are not yet fully understood, particularly in the vast Asian mountain regions. In addition, in these regions, most studies have concentrated on taxa occurring in areas benefitting from relatively generous rainfall from the summer monsoon. In this study, we collected a large number of Oxytropis species throughout their distribution range, and investigated the taxonomy and evolution of this diverse legume genus, which also occurs in mountainous areas prone to drought. Using nuclear (ITS) and plastid (trnL‐F) markers, we reconstructed phylogenetic relationships within Oxytropis, conducting maximum parsimony, fasttree‐like, maximum likelihood, Bayesian, and BEAST analyses. We also used Anchored Hybrid Enrichment (AHE) to test the power of this method to resolve relationships among a small subset of Oxytropis species. For AHE, we sampled eight species and obtained 527 low‐copy and orthologous nuclear loci. We show that the taxonomy of this genus that radiated explosively in Asian mountains will remain recalcitrant based on conventional molecular methods. Because of a severe lack of resolution, none of the available taxonomic treatments for Oxytropis could either be confirmed or refuted based upon ITS and trnL‐F. Nevertheless, we confirm the status of several species, and identify morphological or genetic particularities for some groups of species. The AHE approach yielded a highly supported phylogenetic tree, suggesting that increased taxon sampling coupled with AHE methods promise advances in the study of the taxonomy and evolution of Oxytropis, thus providing further analytical opportunities, such as diversification rate and biogeographical analyses.

Two New Species of the Asian Genus Tripterospermum (Gentianaceae)

Abstract This paper presents descriptions and illustrations for two new species of Gentianaceae, Tripterospermum maculatum from Sichuan Province (China) and T. tanatorajanense from Sulawesi (Indonesia). Based on literature search, Tripterospermum maculatum is morphologically close to T. pingbianense and T. lanceolatum, and T. tanatorajanense resembles T. luzonense and T. alutaceifolium. To test if the new species differ from their morphologically most similar species, we measured various traits on herbarium specimens and performed a principal component analysis (PCA). This analysis showed that the new species differ from similar species in gross morphology for several diagnostic traits. Tripterospermum maculatum differs from T. pingbianense and T. lanceolatum by having calyx lobes longer than calyx tubes, a whitish-yellow corolla maculated with purple dots, and a gynophore shorter than the ovary. Tripterospermum tanatorajanense is distinct from T. luzonense by having a narrowly winged calyx. It differs from T. alutaceifolium and T. luzonense by having a shorter ovary and a slightly longer gynophore. A key including all species of Tripterospermum is provided.