Genetic diversity of Astragalus nitidiflorus, a critically endangered endemic of SE Spain,and implications for its conservation

Inter-simple sequence repeats (ISSR) markers were used to assess the genetic diversity and population structure in five populations of Astragalus nitidiflorus, a critically endangered species endemic to southeast Spain. Eight primers amplified 78 bands with 40 (51.3%) being polymorphic. Statistical results indicated a low genetic diversity at the population and species level, with percentages of polymorphic bands (PPB) ranging from 28.2 to 37.2% (an average of 31.8%), and means of gene diversity (H_E) of 0.129 and 0.171 respectively. The Shannon’s index (SI) ranged from 0.160 to 0.214 at the population level and was 0.260 at the species level. A low level of genetic differentiation among populations was detected, based on the Shannon’s information index (0.297), the coefficient of genetic differentiation between populations (G_ST = 0.2418) and AMOVA analysis (Φ_ST = 0.255). The estimated gene flow (Nm) was 0.789. The high genetic connectivity found among populations of A. nitidiflorus is an evidence of a recent habitat fragmentation. In addition, a bottleneck event in the past has been revealed, with a subsequent reduction of population size and a loss of genetic variation. Based on these results, the conservation strategy of A. nitidiflorus was proposed.     

吉首蒲儿根的繁殖生态学特性及其濒危成因

吉首蒲儿根为近年来发现的菊科蒲儿根属新物种,由于种群和数量都极度稀少,其濒危级别达极危(CR)等级。生态分布和生境的调查结果表明,吉首蒲儿根仅在吉首市德夯地质公园内分布有3个种群,总数约2000-3000株,其中,峡谷瀑布下的种群最大,约2000株;分布海拔为268-384 m,生境特点是温暖、湿润,土壤略偏酸性且钙质高。野外生殖物候的观察结果表明,2月初吉首蒲儿根的芽开始萌动,2月底至3月初抽生花葶,3月中旬至5月中旬开花,6月茎生叶逐渐枯死,随后根状块茎侧芽开始萌动,逐渐形成新分株。种群水平从第1个头状花序开放到最后一个凋谢约为50 d,单个头状花序从开始膨大到凋谢约为18 d,单朵小花的花期为3-5 d,整个过程表现出明显的雌雄异位和菊科特有的花粉次级展现现象。吉首蒲儿根的花部构成、高度同期的开花模式和"刷状机制"、瘦果小且无冠毛及以营养繁殖为主兼有种子繁殖等是对峡谷瀑布特殊生境的生态适应。人为活动的干扰,访花昆虫种类较少、访问频次和效率低,种子数量不多、质量差和传播不开,以及生境要求苛刻则是吉首蒲儿根致濒的主要原因。     

Reproductive ecology of Ameroglossum pernambucense (Scrophulariaceae): is this ornithophilous and threatened shrub highly adapted to a naturally fragmented habitat?

Many rare plants exist in a naturally fragmented distribution and are expected to exhibit reproductive adaptations to isolation. Thus, understanding the reproduction of these plants might be important in predicting the future of artificially fragmented species. Ameroglossum pernambucense is a threatened ornithophilous shrub with naturally fragmented populations on granite outcrops in north-eastern Brazil. The current research studied two populations of A. pernambucense and determined if three reproductive features (mating system, flowering phenology and nectar dynamics) facilitate the colonisation of new areas and the gene flow among the outcrops. To verify the species’ reproductive efficiency, pollinator efficiency and pollen limitation were tested. Ameroglossum pernambucense has a mixed mating system, and pollinators increased seed production. The pollinator efficiency test revealed that hummingbirds can supply the entire pollen demand. No pollen limitation was detected. Variation in sunset time was the main factor to explain the flowering pattern of A. pernambucense. Nectar was abundantly produced after successive removals. The reproductive traits observed in A. pernambucense were interpreted as highly adapted to its fragmented condition. Phenological photoperiodic regulation may increase the flowering synchrony and chances of gene flow among outcrops in environmentally distinct microsites. The mixed mating system favours both the colonisation of isolated outcrops and allogamy. High flower production and its high energetic value may have an important role in pollinator attraction and may increase long-distance outcrossing. Our data suggest that artificially fragmented plants with reproductive features similar to those observed here might be reproductively less susceptible to fragmentation.     

Demography, reproduction, and dormancy along altitudinal gradients in three intermountain Allium species with contrasting abundance and distribution

Little is known about the variation in demographics, flower number, fruit set, and summer dormancy in Allium species native to the Intermountain West region of the United States. The purpose of this study was to investigate demographic patterns, summer dormancy traits, and variation in reproductive characteristics among habitats. Three populations of each of three species, Allium acuminatum, A. brandegei, and A. passeyi, were studied along an altitudinal gradient in northern Utah, USA, from 2004 to 2006. Demographic data were collected from individuals in permanent plots established in each population. Individual flowering plants were periodically monitored and used to calculate reproductive characteristics. Leaf area measurements throughout the 2005 growing season and soil temperature sensors were used to assess the relationship between habitat and dormancy characteristics. Populations of the widely distributed species, A. acuminatum and A. brandegei, were dominated by individuals in seedling and flowering stages while the restricted A. passeyi had populations containing a majority of individuals in the post-seedling, but non-flowering stage-class. There was a strong directional trend in A. acuminatum reproductive traits, with flower number and fruit set decreasing with increasing elevation. The mid-elevation A. brandegei populations were reproductively more successful than the high and low-elevation populations. The high-elevation A. passeyi population had more flowers per plant and higher fruit set in comparison to the lower elevation populations. The onset of summer dormancy as indicated by the timing of leaf senescence, was associated with high soil temperatures specific to each species. In general, the timing of leaf senescence was later in higher elevation populations in all species. A smaller proportion of non-flowering individuals in A. acuminatum and A. brandegei may indicate a high seedling mortality rate or a shorter juvenile phase in comparison to A. passeyi. The A. passeyi populations exhibit demographic characteristics of rare taxa; low seed production and low seedling recruitment. The high number of non-flowering plants in A. passeyi likely includes many reproductively mature individuals which are influenced by the unique habitat and environment of this species. Temperature is likely the key environmental cue inducing summer dormancy in all three species.     

Linking vital rates to invasiveness of a perennial herb

Invaders generally show better individual performance than non-invaders and, therefore, vital rates (survival, growth, fecundity) could potentially be used to predict species invasiveness outside their native range. Comparative studies have usually correlated vital rates with the invasiveness status of species, while few studies have investigated them in relation to population growth rate. Here, I examined the influence of five vital rates (plant establishment, survival, growth, flowering probability, seed production) and their variability (across geographic regions, habitat types, population sizes and population densities) on population growth rate (λ) using data from 37 populations of an invasive, iteroparous herb (Lupinus polyphyllus) in a part of its invaded range in Finland. Variation in vital rates was often related to habitat type and population density. The performance of the populations varied from declining to rapidly increasing independently of habitat type, population size or population density, but differed between regions. The population growth rate increased linearly with plant establishment, and with the survival and growth of vegetative individuals, while the survival of flowering individuals and annual seed production were not related to λ. The vital rates responsible for rapid population growth varied among populations. These findings highlight the importance of both regional and local conditions to plant population dynamics, demonstrating that individual vital rates do not necessarily correlate with λ. Therefore, to understand the role of individual vital rates in a species ability to invade, it is necessary to quantify their effect on population growth rate.     

Later flowering is associated with a compressed flowering season and reduced reproductive output in an early season floral resource

Climate change‐induced shifts in flowering phenology can expose plants to novel biotic and abiotic environments, potentially leading to decreased temporal overlap with pollinators and exposure to conditions that negatively affect fruit and seed set. We explored the relationship between flowering phenology and reproductive output in the common shrub pointleaf manzanita Arctostaphylos pungens in a lower montane habitat in southeastern Arizona, USA. Contrary to the pattern of progressively earlier flowering observed in many species, long‐term records show that A. pungens flowering onset is shifting later and the flowering season is being compressed. This species can thus provide unusual insight into the effects of altered phenology. To determine the consequences of among‐ and within‐plant variation in flowering time, we documented individual flowering schedules and followed the fates of flowers on over 50 plants throughout two seasons (2012 and 2013). We also measured visitation rates by potential pollinators in 2012, as well as both fruit mass and seeds per fruit of flowers produced at different times. Fruit set was positively related to visitation rate but declined with later dates of flower production in both years. Total fruit production per plant was positively influenced by flowering duration, which declined with later flowering onset, as did fruit mass. Individual flowering schedules were consistent between years, suggesting that plants that begin flowering late have lower reproductive output each year. These patterns suggest that if pointleaf manzanita flowering continues to shift later, its flowering season may continue to become shorter, compressing floral resource availability for pollinators and leading to reduced reproductive output. These results reveal the negative effects of delayed phenology on reproductive output in a long‐lived plant. They highlight the value of using natural variation in flowering time, in combination with long‐term data, to anticipate the consequences of phenological shifts.     

Restriction limits and main drivers of fruit production in palm in central Amazonia

Adult plants incapable of producing viable offspring inflate our perception of the size of population distribution. We propose that species occurrence is limited to a subset of the environmental gradient and that it changes as ontogenetic development progresses. Moreover, fruit production is associated with site-specific environmental conditions. We sampled 2988 adult individuals from nine palm species in 30 plots (40 × 250 m) and used a larger data set including 42 other plots distributed along a continuous topo-edaphic gradient in a terra firme forest near Manaus, Brazil. Five out of nine palm species were more restricted to a sub-section of the topo-edaphic gradient in the adult-size phase. More specifically, reproductive individuals of species Attalea attaleoides and A. microcarpa had even more restricted distributions than adult-sized, non-reproductive plants. Successive environmental filtering and competition probably acting through selective mortality led to increasing habitat restriction, with reproductive adults being restricted to a smaller part of the region than juveniles and adults. Water availability and nutrients limited both the ability to produce fruits and the amount of fruit production. Previous studies have reported stronger habitat associations for older plants than for seedlings or juveniles, but we show here that some species are more restricted at their reproductive stage. Plant specializations to local conditions may be more common than currently acknowledged, and a significant portion of individuals in a population might represent sinks. Such strong environmental limitations of reproductive plants should also be considered in management of species with economic value and in conservation planning.     

Reproductive output in Mediterranean shrubs under climate change experimentally induced by drought and warming

The effects of climate change on plant reproductive performance affects the sequence of different plant reproductive stages from flowering to seed production and viability, as well as the network of relationships between them. These effects are expected to respond to different components of climate change, such as temperature and water availability, and may be sensitive to differences in species phenology.We used long-term experimental drought and warming treatments to study the effect of climate change on flower production, fruit and seed-set, seed size and seed germination rate (proportion of germinating seeds) in three Mediterranean shrubs coexisting in a coastal shrubland.Larger plants produced significantly more flowers in all three species, and higher fruit-set in Dorycnium pentaphyllum. Flower production was reduced in drought and warming treatments in the spring-flowering species D. pentaphyllum and Helianthemum syriacum, but not in the autumn–winter species Erica multiflora, which increased flowering in the warming treatment. However, the drought treatment eventually resulted in a decreased seed-set in E. multiflora. Structural equation modelling revealed strong correlations between the sequential reproductive stages. Specifically, flower density in inflorescences determined seed-set in H. syriacum, and seed size and germination rate in E. multiflora. Nevertheless, the relevance of relationships between reproductive traits changed between climatic treatments: in D. pentaphyllum a direct relationship between plant size and seed size only arised in the drought treatment, while in H. syriacum climate treatments resulted in a stronger relationship between the number of flowers and seed-set.This experimental study shows the ability of changing climatic variables to determine the reproductive sequential process of woody species. We show that several parameters of the reproductive performance of some Mediterranean species are affected by drought and warming treatments simulating climate change, highlighting the importance of changes in both water availability and temperature, and the sequential relationship between reproductive stages. Phenological patterns also contribute to species’ differential responses to climatic change, due to the relationship of these patterns with resource availability, environmental conditions and plant–pollinator interactions.     

Reproductive biology of Launaea cervicornis: A keystone species of the Balearic coastal shrublands

Launaea cervicornis (Boiss.) Font Quer & Rothmaler, an endemic of the islands of Majorca and Minorca (Balearic Islands), is a keystone species of the cushion-like plant communities of the coastal rocky places. The study of its reproductive biology shows the existence of differential strategies, with reference to other species of the genus. The principal features are: (1) the absence of continuous iteroparity; (2) short average duration of the flowering period (36.8 days); (3) high value of intrapopulational flowering overlap index (0.86); (4) high levels of aptitude to produce fruits having atelechory as preferential mechanism of dispersion; and (5) germination capacity is increased during the autumn of the first year (fruits are not capable of joining the seedbank of the soil). These characteristics are considered to be determinants for its adaptation to the peculiar habitat in which it prospers.     

SPATIAL AND TEMPORAL VARIATION IN CHASMOGAMY AND CLEISTOGAMY IN OXALIS MONTANA (OXALIDACEAE)

Chasmogamous (CH) and cleistogamous (CL) flower production was investigated in natural populations of the perennial herb Oxalis montana in southern Quebec, Canada. Every 10–12 days during two flowering seasons, we recorded the reproductive output of approximately 2,000 plants distributed among five forest sites. The percentage of plants flowering, proportion of flowering plants producing CH and CL flowers, CH and CL flower number per flowering plant, and the proportion of flowers that are CL differed significantly among sites and corresponded to site differences in forest type and habitat quality. Unlike patterns in most CL species, however, reproduction by cleistogamy increased in sites with habitat conditions favorable to plant growth and sexual reproduction, and decreased in less productive sites. Chasmogamous and CL flower production increased with increasing plant size but plant size explained a significantly greater proportion of the variation in CL flower numbers. The percentage of flowering plants producing CH flowers decreased between years while the proportion of CL flowers increased at all sites during the second flowering season. The somewhat unusual aspects of reproduction in Oxalis may stem from its perennial habit which allows use of stored resources in adjusting the balance of cleistogamy versus chasmogamy in different environmental regimes.     

An evaluation of the species boundaries of two putative taxonomic entities of Euterpe (Arecaceae) based on reproductive and morphological features

Past taxonomic treatments have classified Euterpe espiritosantensis as a synonym of E. edulis. However, both continue to be identified as two distinct species and are enumerated in the threatened species list. The goal of this study was to compare the reproductive biology of sympatric populations of these two morphs so as to identify morphological characters and mechanisms of reproductive isolation that could help to clarify species boundaries. Individuals of E. edulis and E. espiritosantensis show differences in size and duration of the peduncular bract, and differ in regard to inflorescence and immature fruit coloration. With an overlapping flowering period, but with distinctly different flowering peaks, the two taxa share the main visitors, viz. different Apidae and some Vespidae. Fruit and viable seeds are produced after self-, cross- and inter-specific cross-pollination in both morphs. Seed germination is significantly higher in E. edulis than in E. espiritosantensis. Differences in morphological and reproductive features suggest that these sympatric populations of two Euterpe morphs are to a reasonable degree reproductively isolated, which supports the recognition of E. espiritosantensis as a distinct species from E. edulis. The potential for hybridization does not reject the hypothesis of species distinctness, but points to a potential case of sympatric speciation that merits further investigations. Given that natural populations of Euterpe are nowadays fragmented and reduced in area of occurrence, retaining the high conservation status for E. espiritosantensis will help to safeguard this taxonomic entity under considerable threat.     

Rarity up in the mountain: Ecological niche modeling,phenology, and reproductive biology of the most commercialized Masdevallia species

Knowledge of how natural and anthropogenic factors can limit the distribution of rare species is key to develop conservation strategies. We show data on how both factors potentially affect the distribution of a rare high Andean orchid. We chose Masdevallia coccinea as a model because it is endangered and the most commercialized species of the entire genus. Using ecological niche modeling, we confirm its rarity, with a restricted potential occurrence equivalent to only 0.00005 % of South America, 0.0003 % of the Andes, and 0.0009 % of Colombia. We projected the future potential occurrence of M. coccinea and found that it can have a reduction of 43.49 % in the best-case scenario and 89.06 % in the worst-case scenario in 2100. We describe the flowering and fruiting phenologies and demonstrate that the precipitation two months before may determine the first one. Masdevallia coccinea is a rewardless species and, unlike most Pleurothallidinae species, we show that it is self-compatible but non-autonomous selfer. Thus, it is dependent on biotic pollination, performed only by Leucophenga sp. (Drosophilidae: Diptera) which has low efficiency (8.6 % of fruit set). This is the first pollinator report for the genus. While self-compatibility may be related to reproductive assurance, apparently inbreeding depression may affect populations since selfed fruits had less viable seeds. Nevertheless, self-pollination can be avoided by the retention of the anther cap on pollinia, giving more time until the pollinator flies away to another flower. We consider that the rarity of M. coccinea may be a result of both anthropogenic (habitat loss, climate change, and overcollection) and natural factors (high elevation distribution, self-compatibility, rewardless strategy, pollinator specificity, and low fruit set). The several new facets investigated here can be used for future conservation strategies of this emblematic species as well as other high Andean threatened species.     

Effects of soil properties and clonal growth on the apparent sex ratio of the flowering stems of the dioecious clonal shrub Aucuba japonica var. borealis growing in an evergreen coniferous secondary forest

In dioecious plants, the frequencies of flowering stems in each sex produced through clonal growth provide important information on the potential for reproductive success in the populations. However, apart from the light environment in their habitat, the factors affecting the flowering of each sex have not been well documented in shrub species that can maintain their populations in shady environments. In this research, we investigated seven soil variables and the flowering of stems of Aucuba japonica var. borealis in patches of this dioecious clonal shrub with different apparent stem sex ratios in an evergreen coniferous secondary forest with a shady forest floor. Of the 53 patches examined, 52 contained stems with flowers. Flowering stem ratios exhibited a positive relationship with available soil phosphate but a marginal negative relationship with exchangeable magnesium, whereas soil water content was associated with a female-biased flowering sex ratio. Stem density tended to be negatively related to flowering stem ratios in patches containing stems with female flowers but not males. While the results demonstrate that abundant amounts of certain nutrients and moisture in soils promote the production of flowers and/or a bias toward femaleness in patches, it is suggested that antagonistic effects of cations in the soil can inhibit the flowering of both sexes. In addition, the trade-off between sexual reproduction and clonal propagation in the females may amplify the variations in flowering in the population.     

Spatial–temporal patterns of flowering asynchrony and pollinator fidelity in hybridizing species of Narcissus

Speciation requires the evolution of reproductive barriers to achieve isolation between species. In this paper, we examine the role of two major pre-zygotic barriers in reducing the chance of F₁ hybrid formation between two pairs of Narcissus species. Field experiments were performed over 5?years in eight natural populations to determine whether flowering phenology and pollinator fidelity could act as reproductive isolation barriers in Narcissus. Our results show that reproductive isolation due to flowering phenology is highly variable and asymmetric. In some populations, pollinator fidelity was so strong that the quantification of reproductive isolation was complete and a strong negative correlation was found between the strength of this barrier and the abundance of hybrids. Nevertheless, the degree of pollinator fidelity was quite variable among populations indicating that reproductive isolation varies geographically but very consistent across years indicating that plant-pollinator interactions are well established. In fact, the finding that hybrid formation between these species occurs only in sites where pollinator fidelity is incomplete suggests that hybrid formation also varies geographically and that divergent evolutionary outcomes may occur in different sympatric populations of Narcissus.     

Two sympatric Byrsonima species (Malpighiaceae) differ in phenological and reproductive patterns

Sympatric and taxonomically related species may present pre- and/or postzygotic mechanisms for reproductive isolation. We compared the phenology and reproductive biology of Byrsonima intermedia and B. pachyphylla, two sympatric Malpighiaceae species, growing in a remnant of Cerrado in Central Brazil. Both species are evergreens and do not have an overlapping flowering period. In both species, dispersal occurs during the rainy season with low and intermediate overlap in the production of immature and mature fruits, respectively. Both species exhibit self-incompatibility (SI), or, in the case of B. intermedia, facultative SI, and, hence, depend on pollinators to compensate for the lack of spontaneous self-pollination. The flowers of the Byrsonima species were visited by fifteen species of bees that collected pollen and/or oil. Based on their more appropriate intrafloral posture, Epicharis flava and Centris varia were the main pollinators of both species, presenting more frequent visits and/or exhibiting trapline foraging behavior, tending to promote outcrossing. Temporal variation in flowering period and total or partial self-incompatibility seem to function as prezygotic isolation mechanisms that form barriers to gene flow between the studied species and probably avoid competition among pollinators. Both species make oil and pollen available to flower visitors and pollinators almost the entire year, but since Byrsonima intermedia has a long flowering time and is very abundant in the study area, it seems to be more important in maintaining flower-visiting bees.     

西双版纳地区鞘花的繁殖物候特征及影响因素

桑寄生植物作为关键种和关键性食物资源在生态系统中扮演着重要角色,其鞘花的繁殖物候特征不仅会影响自身的繁殖适合度而且还会影响依赖于其获取食物资源的动物。为了解鞘花的繁殖物候特征及其影响因素,探究其与寄主植物和种子散布者之间的相互作用关系。该研究以西双版纳地区分布的鞘花为对象,通过定期观测鞘花和其寄主植物木荷的繁殖物候,测量它们的生物学特性和温湿度等环境因子,并分析鞘花在个体水平和种群水平上的繁殖物候特征以及寄主植物和温湿度对其繁殖物候的影响。结果表明:(1)鞘花的开花物候属于集中大量开花模式,整个种群的花期和果期的持续时间分别约为20 d和72 d,花期和果期的同步性指数都较高,6月中旬鞘花果实被取食的数量和速率最大,之后逐渐降低。(2)鞘花的始花期与木荷的始花期相关性较高,花期和果期与木荷的繁殖物候基本重叠。(3)每月开花和果熟的个体数量与同期和前一个月的平均温度和相对湿度的相关关系均不显著。总之,桑寄生植物的繁殖物候特征可能受到较多因素的影响,若想全面了解半寄生植物的繁殖物候特征,就要综合考虑生物和非生物等多种因子的共同作用。