Lapuz RS, Monzon AKV, Reyes SR, de Alban JD, Tomlinson KW*., 2022. Greater loss and fragmentation of savannas than forests over the last three decades in Yunnan Province, China. Environmental Research Letters 17: 014003. https://doi.org/10.1088/1748-9326/ac3aa2

Abstract

Yunnan Province, southwest China, has a monsoonal climate suitable for a mix of fire-driven savannas and fire-averse forests as alternate stable states, and has vast areas with savanna physiognomy. Presently, savannas are only formally recognised in the dry valleys of the region, and a no-fire policy has been enforced nationwide since the 1980s. Misidentification of savannas as forests may have contributed to their low protection level and fire-suppression may be contributing to vegetation change towards forest states through woody encroachment. Here, we present an analysis of vegetation and land-use change in Yunnan for years 1986, 1996, 2006, and 2016 by classifying Landsat imagery using a hybrid of unsupervised and supervised classification. We assessed how much savanna area had changed over the 3 decades (area loss, fragmentation), and of this how much was due to direct human intervention versus vegetation transition. We also assessed how climate (mean annual temperature, aridity), landscape accessibility (slope, distance to roads), and fire had altered transition rates. Our classification yielded accuracy values of 77.89%, 82.16%, 94.93%, and 86.84% for our four maps, respectively. In 1986, savannas had the greatest area of any vegetation type in Yunnan at 40.30%, whereas forest cover was 30.78%. Savanna coverage declined across the decades mainly due to a drop in open parkland savannas, while forest cover remained stable. Savannas experienced greater fragmentation than forests. Savannas suffered direct loss of coverage to human uses and to woody encroachment. Savannas in more humid environments switched to denser vegetation at a higher rate. Fire slowed the rate of conversion away from savanna states and promoted conversion towards them. We identified remaining savannas in Yunnan that can be considered when drafting future protected areas. Our results can inform more inclusive policy-making that considers Yunnan’s forests and savannas as distinct vegetation types with different management needs.

Chu, Y., Wee, A. K*., Lapuz, R. S., & Tomlinson, K. W*. 2021. Phylogeography of two widespread C4 grass species suggest tableland and valley grassy biome in southwestern China pre-date human modification. Global Ecology and Conservation 31: e01835, DOI: 10.1016/j.gecco.2021.e01835

Abstract

The Yunnan-Guizhou Plateau in southwest China lies at the intersection between East and South Asia, and is characterised by highly complex vegetation ranging from subtropical forest to open grassland. There is a long history of human modification to the landscape, but we know surprisingly little of the biogeography of open habitats such as grassy biomes in the region. To investigate the historical continuity of grassy biomes in southwest China, we examined the biogeographies and evolutionary histories of two widespread and dominant C₄ grasses, Themeda triandra and Heteropogon contortus, in Yunnan and southern Sichuan provinces, using chloroplast DNA markers in combination with climate data. We discovered that cool- and warm-adapted lineages have been widely distributed across the Yunnan-Guizhou Plateau for at least the last 2 million years, pre-dating any possible anthropogenic impact. Moreover, the high genetic diversity and strong spatial structure of both species suggests the continuous presence of multiple large populations, rather than a recent expansion from the dry valleys in response to anthropogenic deforestation. This is the first evidence for the long-term existence of extensive populations of C₄ grasses in this region outside the dry valleys, and calls for a reappraisal of the conservation value of these grass-dominated landscapes.

Anest, A., Charles-Dominique, T., Maurin, O., Millan, M., Edelin, C. and Tomlinson, K.W. (2021), Evolving the structure: climatic and developmental constraints on the evolution of plant architecture. A case study in Euphorbia. New Phytol, 231: 1278-1295. https://doi.org/10.1111/nph.17296

Summary

• Plant architecture strongly influences ecological performance, yet its role in plant evolution has not been explored in depth. By testing both phylogenetic and environmental signals, it is possible to separate architectural traits into four categories: development constraints (phylogenetic signal only); convergences (environmental dependency only); key confluences to the environmental driver (both); unknown (neither).
• We analysed the evolutionary history of the genus Euphorbia, a model clade with both high architectural diversity and a wide environmental range. We conducted comparative analyses of 193 Euphorbia species world-wide using 73 architectural traits, a dated phylogeny, and climate data.
• We identified 14 architectural types in Euphorbia based on trait combinations. We found 22 traits and three types representing convergences under climate groups, 21 traits and four types showing phylogenetic signal but no relation to climate, and 16 traits and five types with both climate and phylogenetic signals.
• Major drivers of architectural trait evolution likely include water stress in deserts (selected for succulence, continuous branching), frost disturbance in temperate systems (selected for simple, prostrate, short-lived shoots) and light competition (selected for arborescence). Simple architectures allowed resilience to disturbance, and frequent transitions into new forms. Complex architectures with functional specialisation developed under stable climates but have low evolvability.

Chaturvedi, R.K.*, Tripathi, A., Raghubanshi, A.S. & Singh, J.S., 2021. Functional traits indicate a continuum of tree drought strategies across a soil water availability gradient in a tropical dry forest. Forest Ecology and Management 482: 118740. DOI:  10.1016/j.foreco.2020.118740

Abstract

This study evaluates drought survival mechanisms of tropical dry forest (TDF) trees based on their functional traits (FTs). We addressed the following questions: (i) What are the dominant functional guilds (FGs) of tree species across a soil water availability gradient in TDF? (ii) What are the important FTs influencing tree species assemblage in different FGs? (iii) What is the functional composition of different FGs in the study sites, and how are they influencing biomass accumulation capacity (BAC) across the soil water availability gradient?

We selected 12 FTs associated with plant water use strategies, viz., canopy cover intensity (CC), wood specific gravity (WSG), saturated stem water content (QWsat), leaf size or leaf area (LA), specific leaf area (SLA), relative water content (RWC), leaf dry matter content (LDMC), leaf nitrogen content (LNC), leaf phosphorus content (LPC), maximum saturated stomatal conductance (Gs_max), maximum saturated photosynthetic rate (A_max), and intrinsic water use efficiency (WUEi). By using these FTs, we classified 47 tree species by HCPC (hierarchical clustering on principal components) into three FGs, viz, drought avoiding (DAFG), drought resistant (DRFG), and drought tolerant (DTFG). For species grouping, QWsat was the most significant for DAFG, impacts of A_max, LPC, Gs_max and LNC were significant for DRFG, while LDMC and CC were significant for DTFG. Across the five forest fragments, along a soil moisture content (SMC) gradient, the three FGs exhibited significant differences in species richness, stem density, aboveground biomass, and biomass accumulation capacity (BAC). We observed increasing dominance of DAFG towards drier sites, while the abundance of DRFG and DTFG was higher towards moister sites. Among the three FGs, DTFG showed highest biomass and BAC in our study region. Strategies of DAFG were more associated with savanna habitats, while DRFG and DTFG exhibited strategies important for TDFs. Our findings could help forest managers in restoration and conservation of TDFs.

Silvaraju, S., Menon, N., Fan, H*., Lim, K. and Kittelmann, S.*, 2020. Phylotype-Level Characterization of Complex Lactobacilli Communities Using a High-Throughput, High-Resolution Phenylalanyl-tRNA Synthetase (pheS) Gene Amplicon Sequencing Approach. Applied and Environmental Microbiology 87: e02191-20. DOI: 10.1128/AEM.02191-20

Abstract: The lactobacilli identified to date encompass more than 270 closely related species that were recently reclassified into 26 genera. Because of their relevance to industry, there is a need to distinguish between closely related and yet metabolically and regulatory distinct species, e.g., during monitoring of biotechnological processes or screening of samples of unknown composition. Current available methods, such as shotgun metagenomics or rRNA gene-based amplicon sequencing, have significant limitations (high cost, low resolution, etc.). Here, we generated a phylogeny of lactobacilli based on phenylalanyl-tRNA synthetase (pheS) genes and, from it, developed a high-resolution taxonomic framework which allows for comprehensive and confident characterization of the community diversity and structure of lactobacilli at the species level. This framework is based on a total of 445 pheS gene sequences, including sequences of 276 validly described species and subspecies (of a total of 282, including the proposed L. timonensis species and the reproposed L. zeae species; coverage of 98%), and allows differentiation between 265 species-level clades of lactobacilli and the subspecies of L. sakei The methodology was validated through next-generation sequencing of mock communities. At a sequencing depth of ∼30,000 sequences, the minimum level of detection was approximately 0.02 pg per μl DNA (equaling approximately 10 genome copies per μl template DNA). The pheS approach, along with parallel sequencing of partial 16S rRNA genes, revealed considerable diversity of lactobacilli and distinct community structures across a broad range of samples from different environmental niches. This novel complementary approach may be applicable to industry and academia alike.

IMPORTANCE: Species formerly classified within the genera Lactobacillus and Pediococcus have been studied extensively at the genomic level. To accommodate their exceptional functional diversity, the over 270 species were recently reclassified into 26 distinct genera. Despite their relevance to both academia and industry, methods that allow detailed exploration of their ecology are still limited by low resolution, high cost, or copy number variations. The approach described here makes use of a single-copy marker gene which outperforms other markers with regard to species-level resolution and availability of reference sequences (98% coverage). The tool was validated against a mock community and used to address diversity of lactobacilli and community structure in various environmental matrices. Such analyses can now be performed at a broader scale to assess and monitor the assembly, structure, and function of communities of lactobacilli at the species level (and, in some cases, even at the subspecies level) across a wide range of academic and commercial applications.

For more details on papers published from this group, click here.

Tripathi S.N.*, Bhadouria, R., Srivastava, P., Devi, R.S., Chaturvedi, R.K. & Raghubanshi, A.S. 2020. Effects of variations in light availability on leaf attributes and seedling growth of four tree species in tropical dry forest. Ecological Processes 9: 2. DOI: 10.1186/s13717-019-0206-4

Background: In tropical dry forests, variation in understory light availability due to season and canopy tree density could be a governing factor in establishment and growth of tree seedlings. Species with varying life history traits are expected to respond differentially to such heterogeneity. We investigated the response of seedlings of four tree species in a tropical day forest in relation to spatiotemporal variability of light. We attempt to explore the role of leaf attributes in explaining intra- and inter-specific variations in relative growth rate. Four study sites, each with three contrasting canopy conditions, were selected along a soil moisture gradient. Seedlings of four tree species (viz., Acacia catechu, Bridelia retusa, Lagerstroemia parviflora, and Shorea robusta), varying in life history traits, were monitored for seasonal variations in growth traits across canopy condition and sites for 2 years.

Results: We observed a larger variation in leaf attributes for pioneer species. A. catechu showed highest mean values for leaf dry matter content, leaf nitrogen concentration, leaf phosphorus concentration, net stomatal conductance, net photosynthetic rate, and relative growth rate in high light conditions. S. robusta and B. retusa demonstrated highest mean values for all the leaf attributes (except leaf dry matter content) in low light conditions. However, intermediate values for leaf attributes were observed in L. parviflora which preferred moderate light conditions.

Conclusions: Seasonal variations in light availability at the forest floor appear to play an important role in the establishment and growth of tree seedlings in seasonal dry forests. Leaf attributes can be used to explain intra- and inter-specific variation in response to light availability. Leaf attributes in combinations can be used to predict relative growth rate of tree species in tropical dry environment, which apart from soil moisture is also determined by light availability due to seasonal changes and canopy tree density.

Xu W, Tomlinson KW, Jie L*. 2020. Strong intraspecific trait variation in a tropical dominant tree species along an elevational gradient. Plant Diversity 42: 1-6. DOI: 10.1016/j.pld.2019.10.004

Abstract: Functional trait variation of plant species includes both inter- and intraspecific variation; however, trait-based plant ecology generally considers only interspecific variation while ignoring intraspecific variation. One reason for this neglect is that intraspecific variation may be negligible when compared to interspecific variation; however, direct comparisons between inter- and intraspecific variation of plant species are lacking, especially in tropical forests. Here we investigated intraspecific leaf trait variation (leaf area, specific leaf area, leaf thickness, leaf density, leaf chlorophyll content) of Pittosporopsis kerrii Craib (Icacinaceae), the most abundant tree species in the Xishuangbanna tropical seasonal rainforest in southwestern China, along an elevational gradient (703–824 m). We found a substantial range of intraspecific variation in P. kerrii that was never less than 22.1% of range of the interspecific variation among 462 tree species reported before in the same community. Moreover, with increased elevation, both leaf thickness and density increased and specific leaf area decreased significantly. It could be more important for the individuals of P. kerrii to produce thicker and denser leaves to tolerate environmental stress (e.g. soil water availability) rather than having high growth rates at the places with higher elevation in the Xishuangbanna tropical seasonal rainforest.

Gélin, U., Keller, M., de Beaupuis, V., Nowak, R., Lévy, F., Locatelli, Y. Impact of hybridization between sika and red deer on phenotypic traits of the newborn and mother-young relationships, Animal Behaviour (2019), DOI: 10.1016/j.anbehav.2019.09.016

Abstract: The removal of pre-existing geographical barriers between species, notably by humans, allows previously isolated species to hybridize. Interspecies hybridization has been studied at different levels but the mothereyoung relationship, which is crucial for the offspring’s survival, has not been investigated in wild mammals. We compared the establishment of the mothereyoung relationship at birth and during the first week of life and the morphological development of the young in red deer, Cervus elaphus, sika deer, Cervus nippon, and their hybrids (male nippon  female elaphus). Most mothereyoung behaviours did not differ between the three groups, showing strong conservation of peripartum behaviours in cervids. In contrast, the behaviour and body size of the hybrid young were similar or tended to be close to those found in the maternal species, suggesting important maternal effects. In addition, hybrid young were more likely to be standing during the first week than young from the other groups, possibly resulting from increased maternal stimulation and/or hybrid vigour. Adult females in the herd were more likely to perform smell-related and agonistic behaviours towards the hybrid young, suggesting potential species recognition issues, which require further investigation. In conclusion, our findings show that hybridization has no noticeable impact on the mothereyoung relationship, which could partly explain the success of hybridization between the sika and red deer in the wild.

Congratulations to Armani who got the “best poster/presentation” at the New Phytologist symposium in Ghana!

Congratulation to Thiri who is Msc graduate !