The evolution of plant sexual diversity

Charles Darwin recognized that flowering plants have an unrivalled diversity of sexual systems. Determining the ecological and genetic factors that govern sexual diversification in plants is today a central problem in evolutionary biology. The integration of phylogenetic, ecological and population-genetic studies have provided new insights into the selective mechanisms that are responsible for major evolutionary transitions between reproductive modes.     

The role of roadsides in conserving Cerrado plant diversity

The structure of Cerrado vegetation (sensu stricto) along roadsides was compared with that of protected areas (reserves). The superior stratum of reserves had 2.7 times more individuals and 1.4 times more species than on roadsides, while in the intermediate stratum there were 1.7 times more individuals and 25 % more species in reserves. Additionally, roadsides had a lower prevalence of tree species with thin bark and from forest physiognomies. In the intermediate stratum of roadsides there was a lower proportion of forest species, and also fewer species dispersed by animals. These differences occur, possibly because the vegetation of their edges is cleared during the construction of the roads and part of the soil is taken as landfill. Later, they suffer from a higher fire frequency and high coverage of exotic grasses (80 % average). Moreover, it is likely that the absence of some dispersers on roadsides may affect the recruitment of young plants. Despite these differences, the roadsides are able to maintain at least 70 % of tree species and 72 % of shrub species found in reserves. These results show that roadside vegetation can contribute to the conservation of the flora of Cerrado. This is particularly important considering that over 60 % of the original area of this ecosystem has been destroyed and that less than 4 % is protected. With 32,012 km of roads in the Cerrado alone, the roadside vegetation may represent a cumulative area of 96,000 of hectares, an area larger than many of the Cerrado’s national parks.     

Sub-lethal plant defences: the paradox remains

Lodgepole pine (Pinus contorta) trees of two different seed origins, one a poor quality host (Alaskan lodgepole pine), the other a good quality host (south coastal lodgepole pine), were infested with known numbers of eggs of the pine beauty moth, Panolis flammea. Each tree had paired sleeves, one allowing access by invertebrate predators, the other denying this access. When the sleeves were removed, the numbers of larvae surviving, their weights and developmental stages were assessed. Larvae reared on south coastal lodgepole pine (SLP) in the absence of predators were significantly heavier and had significantly better survival rates than larvae reared in comparable conditions on Alaskan lodgepole pine (ALP). However, in the open sleeves, although the larvae reared on SLP were significantly heavier than those on ALP, survival was significantly greater on ALP. Thus predation was greater on the faster developing larvae on the better quality host. These results indicate that slow growth by a herbivore does not necessarily result in greater vulnerability to predators.     

The long-term relationship between plant diversity and total plant biomass depends on the mechanism maintaining diversity

The relationship between plant diversity and total plant biomass is of great current interest in ecology. Niche differences among plants are widely thought to promote both plant coexistence, and higher biomass in more diverse polycultures. Using simple mechanistic models, I demonstrate that not all niche differences among plants are equally likely to promote high total biomass in polyculture. In particular, transgressive overyielding (when a polyculture of plants outperforms any monoculture) occurs for a wide range of parameter values when plants coexist in polyculture due to differences in resource use. Transgressive overyielding occurs only for a limited set of parameter values when specialist herbivores mediate plant coexistence, and is impossible when generalist herbivores mediate coexistence. Niche differences among plants promote high biomass in polyculture only when plants coexist in polyculture at the expense of other trophic levels – that is, by converting into biomass resources that would otherwise be bound in herbivores, or exist in a free state. A major challenge for future work will be to identify the joint consequences of different coexistence mechanisms for plant diversity and ecosystem performance.     

Conservation of plant diversity in Korea

Korea is a land of contrasts. The mountainous Korean peninsula arches north and northwest towards the Russian and Chinese borders, where the last areas of old growth coniferous forest and the land formed five forest types. Plant and habitat diversity in Korea has been largely damaged by various kinds of human activities. The plant diversity of Korea is severely threatened due to the high population density and rapid industrialization since the 1960s, as well as the illegal collection of wild plants for ornamental, medicinal, and food purposes. Natural areas have been greatly fragmented and survive only as ecological islands surrounded by modified cultivated and industrial lands. For instance, more than 60 industrial parks are located along the coast, and these have contributed to the rapid destruction of plant diversity in the coastal areas of the peninsula. The modern concept of plant conservation in Korea is still in an infant stage. The cooperation of plant conservation bodies with disciplinary approaches based on conservation biology are essential strategies to pursue plant conservation. The capacity building for plant conservation in Korea has different management regimes by the relevant ministries. Since the late 1990s, the plant conservation body Korean Plant Specialist Group of the International Union for the Conservation of Nature and Natural Resources Species Survival Commission (IUCN SSC) has been closely linked with international conservation bodies for in situ and ex situ conservation management. Under the umbrella of the national plant conservation strategies, the different strategies and working agencies can be fully integrated. Furthermore, the systematic approaches for the recovery of threatened species, as well as habitat monitoring over the long-term basis, will need to be supported by a stable budget policy. Also, protocol for the conservation of rare and endangered plant species, including recovery works in Korea, is strongly needed.     

Understanding plant reproductive diversity

Flowering plants display spectacular floral diversity and a bewildering array of reproductive adaptations that promote mating, particularly outbreeding. A striking feature of this diversity is that related species often differ in pollination and mating systems, and intraspecific variation in sexual traits is not unusual, especially among herbaceous plants. This variation provides opportunities for evolutionary biologists to link micro-evolutionary processes to the macro-evolutionary patterns that are evident within lineages. Here, I provide some personal reflections on recent progress in our understanding of the ecology and evolution of plant reproductive diversity. I begin with a brief historical sketch of the major developments in this field and then focus on three of the most significant evolutionary transitions in the reproductive biology of flowering plants: the pathway from outcrossing to predominant self-fertilization, the origin of separate sexes (females and males) from hermaphroditism and the shift from animal pollination to wind pollination. For each evolutionary transition, I consider what we have discovered and some of the problems that still remain unsolved. I conclude by discussing how new approaches might influence future research in plant reproductive biology.     

Biosynthetic diversity in plant triterpene cyclization

Plants produce a wealth of terpenoids, many of which have been the tools of healers and chiefs for millennia. Recent research has led to the identification and characterization of many genes that are responsible for the biosynthesis of triterpenoids. Cyclases that generate sterol precursors can be recognized with some confidence on the basis of sequence; several catalytically important residues are now known, and the product profiles of sterol-generating cyclases typically reflect their phylogenetic position. By contrast, the phylogenetic relationships of cyclases that generate nonsteroidal triterpene alcohols do not consistently reflect their catalytic properties and might indicate recent and rapid catalytic evolution.     

Scale dependence in desert plant diversity

The relationship between the number of species and the area sampled is one of the oldest and best-documented patterns in community ecology. An equation of the form S = cA ^z describing more precisely the species–area relation for plant species in smaller area is proposed as a result of intensive examination of species presence. Several study and field data from a wild range of plant and animal taxa suggest that the slope, z, of a graph of the logarithm of species richness against the logarithm of area is not a constant to the grassland or woodland community. We collected replicated and randomized plant data at 6 spatial scales from 1 m² to 1 km² in the desert region of northwest China to identify the scale dependence in desert plant biodiversity. The results showed that the slope of the log–log plot varied systematically with spatial scale. The value of z was high (0.37) at small scales from 1 to 10 m² and it decreased with increased spatial scale subsequently. When spatial scales varied from 1 m² to 1 km², the value of z varied from 0.37 to 0.035, suggesting that desert plant diversity has strongly scale-dependence at the small scales (less than 100 m²). The result is different from the research of grassland and woodland communities.     

Human aspects of plant diversity

Different human societies have different biodiversity around them; there is diversity in their food habits, ailments, occupations, daily routine, social customs, needs, and notions about natural phenomena. They have different domestic animals, and consequently, different veterinary diseases to manage. These circumstances have given rise to very diverse experiences among indigenous societies about plant wealth around them. Over generations, this has made very rich additions to the interrelationships between man and plant wealth around him. Faith, tradition, taboos and several such associations with forests and particular plant species have helped in conservation of plant diversity. The richness of plant diversity in any area, is not evaluated merely by the number of species occurring there, but by the intensity of associations and dependence of the indigenous communities on that plant wealth. Respect for this indigenous knowledge, and relationship helps in conservation.     

Assessing diversity in plant communities: The importance of within-species variation

While the measurement of plant species diversity continues to play a central role in ecology and conservation, few formal attempts have been made at defining the concept of diversity, and, specifically, at evaluating the utility of taxonomic species as units for diversity indices. Ecological diversity is defined here as a measure of the degree of biotic and/or abiotic dissimilitude within a community that is perceivable and utilizable by organisms. Although indices based merely on ‘species’ may be useful for cataloging taxonomic diversity in communities, plant taxa are generally unreliable units for quantifying the ecological diversity perceived and utilized by most organisms in communities. Recent research highlights the shortcomings of the unit of species for characterizing ecological diversity, and we advocate the further exploration of alternative diversity classes with which to describe plant communities.     

中国高等植物多样性

据最新资料统计,中国有野生高等植物454科3,818属35,112种。其中,苔藓植物151科602属3,045种;蕨类植物38科176属2,124种;裸子植物8科37属227种;被子植物257科3,003属29,716种。根据世界高等植物多样性相关研究数据,中国的苔藓、蕨类、裸子植物和被子植物物种多样性分别占世界的18.8%、17.7%、22.2%和11.1%。中国高等植物特有属共212属,其中苔藓7属、蕨类2属、裸子植物7属、被子植物196属;特有种共17,439种,其中苔藓524种、蕨类840种、裸子植物115种、被子植物15,960种;特有种比例分别为17.2%、39.6%、50.7%和53.7%。因此,中国高等植物中国特有种的比例为49.7%,维管植物为52.8%,种子植物为53.7%。物种多样性最高的前10个科依次为:菊科(227属/2,315种)、禾本科(215/1,787)、豆科(141/1,631)、兰科(205/1,556)、唇形科(103/975)、毛茛科(38/957)、蔷薇科(53/954)、莎草科(32/871)、杜鹃花科(22/841)和茜草科(94/696)。特有属最多的前12个科依次为:苦苣苔科(26属)、菊科(18)、兰科(14)、唇形科(11)、伞形科(9)、十字花科(9)、夹竹桃科(6)、禾本科(6)、野牡丹科(5)、紫草科(4)、茜草科(4)和毛茛科(4)。物种多样性最高的前10个属依次为:杜鹃花属(Rhododendron)(588种)、薹草属(Carex)(537)、黄芪属(Astragalus)(420)、马先蒿属(Pedicularis)(363)、紫堇属(Corydalis)(357)、报春花属(Primula)(310)、风毛菊属(Saussurea)(293)、柳属(Salix)(279)、凤仙花属(Impatiens)(274)和龙胆属(Gentiana)(255)。特有种最多的前10个属依次为:杜鹃花属(433种)、马先蒿属(283)、薹草属(273)、紫堇属(258)、黄芪属(237)、凤仙花属(234)、报春花属(222)、小檗属(Berberis)(209)、楼梯草属(Elatostema)(207)和风毛菊属(196)。物种数目超过5,000种的省区依次为:云南(15,900种)、四川(10,374)、西藏(7,629)、广西(7,399)、贵州(6,405)、广东(5,498)和台湾(5,290)。在17个世界生物多样性大国中,按物种多样性排序,中国略低于巴西,位列第四;按照物种特有比例排序,中国略高于菲律宾,位列第七。     

Cryptosexuality and the genetic diversity paradox in coffee rust, Hemileia vastatrix

Background

Despite the fact that coffee rust was first investigated scientifically more than a century ago, and that the disease is one of the major constraints to coffee production - constantly changing the socio-economic and historical landscape of the crop - critical aspects of the life cycle of the pathogen, Hemileia vastatrix, remain unclear. The asexual urediniospores are regarded as the only functional propagule: theoretically, making H. vastatrix a clonal species. However, the well-documented emergence of new rust pathotypes and the breakdown in genetic resistance of coffee cultivars, present a paradox.

Methods and Results

Here, using computer-assisted DNA image cytometry, following a modified nuclear stoichiometric staining technique with Feulgen, we show that meiosis occurs within the urediniospores. Stages of spore development were categorised based on morphology, from the spore-mother cell through to the germinating spore, and the relative nuclear DNA content was quantified statistically at each stage.

Conclusions

Hidden sexual reproduction disguised within the asexual spore (cryptosexuality) could explain why new physiological races have arisen so often and so quickly in Hemileia vastatrix. This could have considerable implications for coffee breeding strategies and may be a common event in rust fungi, especially in related genera occupying the same basal phylogenetic lineages.     

The impact of nesting cormorants on plant and arthropod diversity

Seabirds can strongly affect several major factors correlated with species diversity by concentrating marine nutrients on their nesting islands and by physically disturbing island vegetation. In this study, we investigated the effects of nesting cormorants on the abundance, species richness, and composition of plants and arthropods (Coleoptera, Heteroptera, Araneae, and Chironomidae) on islands in Stockholm archipelago, Sweden. Nesting cormorants negatively affected plant species richness and vegetation cover and that changed plant species composition. The effect of nesting cormorants on island arthropods varied between feeding groups and sampling methods. Most orders did not change in abundance or species richness but some, such as coleopterans and spiders changed in species composition. Herbivorous coleopterans were generally negatively affected by cormorants whereas fungivorous species and scavengers were generally positively affected. In structural equation modeling we found that the effect of cormorants was sometimes direct, such as on scavengers, but many effects on island consumers were mediated by changes in vegetation caused by cormorant presence. Overall, arthropod communities were highly dissimilar between cormorant and reference islands, and we therefore conclude that nesting cormorants not only affect the diversity of their nesting islands but also of the archipelago as a whole. The total diversity in the archipelago may increase through regional increased habitat heterogeneity and by adding species which are favored by seabirds (e.g. scavenging and fungivorous coleopterans).