Testing the regeneration niche hypothesis with Gesneriaceae (tribe Sinningiae) in Brazil: Implications for the conservation of rare species

The germination requirements of sexually reproducing plants are regulated by environmental factors such as temperature. Those factors acting at the germination phase are part of the regeneration niche, which is fundamental in the processes that contribute to habitat suitability and geographic distribution. We tested the hypothesis that rarity is associated with regeneration niche in three species of plants in the family Gesneriaceae (tribe Sinningieae), Sinningia rupicola (Mart.) Wiehler, Paliavana sericiflora Benth and Sinningia allagophylla (Mart.) Wiehler, which vary in their distribution and habitat specificity but share a small zone of sympatry in rocky fields south of Belo Horizonte in Minas Gerais, Brazil. The regeneration niche was tested using a seed germination experiment under controlled light conditions at seven fixed temperatures (10–40°C at 5°C intervals). Each of the three species germinated differently at the various temperatures. The species with the smallest geographic range, S. rupicola, also had the most restricted germination: germination peaked at 15°C when relatively few seeds germinated (45%), and even fewer germinated at other temperatures. The regeneration niche was wider in P. sericiflora and wider still in S. allagophylla, with germination greater than 90% between 15–25°C and greater than 80% between 15–30°C, respectively. Our germination results provide qualified support for the hypothesis of correlation of the regeneration niche with geographic distribution of related plant taxa, with important conservation implications for rare and endangered species.     

Origins of prehistoric flints: The neocortex memory revealed by scanning electron microscopy

Flint has been widely used during prehistoric times and the question of determining the origin of specific pieces is recurrent in archaeological discussions. We have run a scanning electron microscope examination of the surfaces of both natural flints from geological deposits and flaked artefacts excavated from prehistoric sites in the Massif Central (France). These samples exhibit mineralogical textures resulting from genomorphic and phenomorphic processes, dispersed alteration in the form of erosion as well as the dissolution and migration of more or less mobile elements. Rocks used to manufacture artefacts at Sainte-Anne 1 (Haute-Loire, France) and Payre (Ardèche, France) show various kinds of alteration related to the range of phases of transport and deposition to which they were subjected, beginning with their first exposure in a geological context and following through to the post-depositional phase, (i.e., following abandonment as artefacts in an archaeological site). Later phenomena do not however completely obliterate stigma imprinted prior to their prehistoric collection, because the main late-phase change that occurs on flat surfaces prior to their collection is preserved in the hollows of remnant natural surfaces on archaeological tools. With the scanning electron microscope, five distinct morphologies representative of different environments have been characterised by establishing associations between the different forms and by plotting their regional distribution.     

Exploring rock fissures: does a specialized root morphology explain endemism on granite outcrops?

Background and Aims

Worldwide, many plant species are confined to open, shallow-soil, rocky habitats. Although several hypotheses have been proposed to explain this habitat specificity, none has been convincing. We suggest that the high level of endemism on shallow soils is related to the edaphic specialization needed to survive in these often extremely drought-prone habitats. Previous research has shown that species endemic to ironstone communities in SW Australia have a specialized root morphology that enhances their chance to access fissures in the underlying rock. Here we test the generality of these findings for species that are confined to a shallow-soil habitat that is of much greater global significance: granite outcrops.

Methods

We compared temporal and spatial root growth and allocation of three endemic woody perennials of SW Australian granite outcrop communities with those of congeners occurring on nearby deeper soils. Seedlings of all species were grown in 1·2 m long custom-made containers with a transparent bottom that allowed monitoring of root growth over time.

Key Results

The granite outcrop endemics mostly differed in a predictable way from their congeners from deeper soils. They generally invested a larger portion of their biomass in roots, distributed their roots faster and more evenly over the container and had a lower specific root length. In different species pairs the outcrop endemics achieved their apparent advantage by a different combination of the aforementioned traits.

Conclusions

Our results are consistent with earlier work, indicating that species restricted to different types of drought-prone shallow-soil communities have undergone similar selection pressures. Although adaptive in their own habitat in terms of obtaining access to fissures in the underlying rock, these root system traits are likely to be maladaptive in deeper soil habitats. Therefore, our results may provide an explanation for the narrow endemism of many shallow-soil endemics.     

Conservation of old individual trees and small populations is integral to maintain species' genetic diversity of a historically fragmented woody perennial

Historically fragmented and specialized habitats such as granite outcrops are understudied globally unique hot spots of plant evolution. In contrast to predictions based on mainstream population genetic theory, some granite outcrop plants appear to have persisted as very small populations despite prolonged geographic and genetic isolation. Eucalyptus caesia Benth. is a long‐lived lignotuberous tree endemic with a naturally fragmented distribution on granite outcrops in south‐western Australia. To quantify population to landscape‐level genetic structure, we employed microsatellite genotyping at 14 loci of all plants in 18 stands of E. caesia. Sampled stands were characterized by low levels of genetic diversity, small absolute population sizes, localized clonality and strong fine‐scale genetic subdivision. There was no significant relationship between population size and levels of heterozygosity. At the landscape scale, high levels of population genetic differentiation were most pronounced among representatives of the two subspecies in E. caesia as originally circumscribed. Past genetic interconnection was evident between some geographic neighbours separated by up to 20 km. Paradoxically, other pairs of neighbouring stands as little as 7 km apart were genetically distinct. There was no consistent pattern of isolation by distance across the 280 km range of E. caesia. Low levels of gene flow, together with strong drift within stands, provide some explanation of the patterns of genetic differentiation we observed. Individual genet longevity via the ability to repeatedly resprout and expand from a lignotuber may enhance the persistence of some woody perennial endemic plants despite small population size, minimal genetic interconnection and low heterozygosity.     

海南龙血树种群的年龄结构及分布格局

通过调查石灰岩及花岗岩两种不同生境样地内海南龙血树分布和胸径/基径情况,分析其龄级结构,用相邻格子法对海南龙血树进行每木调查,并采用方差/均值比率法和丛生指数(I)、负二项参数(K)、平均拥挤度(m*)、聚块性指数(PAI)、聚集指数(Ca)等聚集强度指数对海南龙血树种群分布格局进行分析。结果表明:石灰岩及花岗岩样地内的海南龙血树种群皆呈衰退型,其中天安乡、江边乡两样地种群的幼苗储备不足,昌化镇及东澳镇两地的中龄级植株数量稀少,大小洞天样地的种群年龄结构不完整;石灰岩样地内的海南龙血树种群在不同尺度、不同阶段上主要表现为集群分布,花岗岩地区种群的不同组分在不同取样尺度上分布格局相同,幼龄树、中龄树、老龄树的分布格局分别为集群分布、均匀分布、集群分布。     

海南龙血树种群的年龄结构及分布格局

通过调查石灰岩及花岗岩两种不同生境样地内海南龙血树分布和胸径/基径情况,分析其龄级结构,用相邻格子法对海南龙血树进行每木调查,并采用方差/均值比率法和丛生指数(I)、负二项参数(K)、平均拥挤度(m*)、聚块性指数(PAI)、聚集指数(Ca)等聚集强度指数对海南龙血树种群分布格局进行分析。结果表明:石灰岩及花岗岩样地内的海南龙血树种群皆呈衰退型,其中天安乡、江边乡两样地种群的幼苗储备不足,昌化镇及东澳镇两地的中龄级植株数量稀少,大小洞天样地的种群年龄结构不完整;石灰岩样地内的海南龙血树种群在不同尺度、不同阶段上主要表现为集群分布,花岗岩地区种群的不同组分在不同取样尺度上分布格局相同,幼龄树、中龄树、老龄树的分布格局分别为集群分布、均匀分布、集群分布。     

Variability,genetic structure and phylogeography of the dolomitophilous species Convolvulus boissieri (Convolvulaceae) in the Baetic ranges,inferred from AFLPs,plastid DNA and ITS sequences

Convolvulus boissieri is an edaphic endemic plant which grows in the Baetic ranges always in association with high mountain xeric dolomitic outcrops. As these dolomitic areas appear in a ‘soil‐island’ pattern, the distribution of this species is disjunct. Populations of this species frequently include a low number of individuals, which could have an important impact on their genetic diversity and viability. Convolvulus boissieri provides an excellent opportunity to study the genetic and phylogeographical aspects of species linked to dolomites. We used amplified fragment length polymorphism markers and nuclear (internal transcribed spacer region of the nuclear ribosomal cistron) and plastid sequences (trnL‐trnF, rpl32‐trnL and trnQ‐5′rps16). Data were generated from 15 populations, representing the distribution area of the species. For sequence analysis and estimation of divergence times we also used sequences from other Convolvulus species. Results revealed low intrapopulational genetic diversity and a strong interpopulational structure. Furthermore, we found clear‐cut differentiation caused by the existence of two large population groups separated by the Guadiana Menor river basin. Estimation of divergence times indicated that divergence took place during the Pleistocene glaciations. Genetic diversity and differentiation are similar to those other species exhibiting naturally fragmented distribution with a sky islands pattern. In phylogeographical terms, the successive glaciation–interglaciation cycles caused the species to spread from the western sites to eastern sites, the latter being more exposed to the effects of glaciation. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176 , 506–523.     

土地利用变化对花岗岩红壤底土溶解性有机质数量和光谱特征的影响

了解底土溶解性有机质(DOM)的数量和化学结构对土地利用变化的响应,对科学评价区域土壤有机质动态和碳库稳定性具有重要意义。通过选取花岗岩红壤丘陵区同一景观单元的天然林地(常绿阔叶林)以及由此转变而来的杉木人工林、板栗园和坡耕地,采用化学分析结合光谱扫描(紫外光谱、二维荧光光谱和傅里叶变换红外光谱)技术,研究底土(0.2—1 m)和表土(0—0.2 m)DOM数量和结构对土地利用变化的响应差异,结果表明:58%—87%的DOM贮存在底土中。天然林地土壤的DOM数量最为丰富,底土DOM的宏观化学结构比表土更为简单,以碳水化合物、类蛋白为主。天然林转变为其他利用方式后,底土DOM的损失量(26%—41%)超过表土(12%—49%),冬季比夏季更为凸显;这反映底土DOM数量对人为干扰和植被变化的高度敏感性。同时,底土DOM宏观化学结构趋于复杂化,芳香类、烷烃类和烯烃类的化学抗性物质出现积累的现象。DOM光谱曲线形状、特定峰值、特征值对土地利用的响应敏感,对人为干扰后植被、土壤有机质的变化具有生态指示意义。研究显示,天然林地转变为其他利用方式后,不仅导致底土DOM的损失,也显著降低土壤有机质品质,长期上削弱底土的碳库稳定性和碳吸存能力。     

High species diversity and turnover in granite inselberg floras highlight the need for a conservation strategy protecting many outcrops

Determining patterns of plant diversity on granite inselbergs is an important task for conservation biogeography due to mounting threats. However, beyond the tropics there are relatively few quantitative studies of floristic diversity, or consideration of these patterns and their environmental, biogeographic, and historical correlates for conservation. We sought to contribute broader understanding of global patterns of species diversity on granite inselbergs and inform biodiversity conservation in the globally significant Southwest Australian Floristic Region (SWAFR). We surveyed floristics from 16 inselbergs (478 plots) across the climate gradient of the SWAFR stratified into three major habitats on each outcrop. We recorded 1,060 species from 92 families. At the plot level, local soil and topographic variables affecting aridity were correlated with species richness in herbaceous (HO) and woody vegetation (WO) of soil‐filled depressions, but not in woody vegetation on deeper soils at the base of outcrops (WOB). At the outcrop level, bioclimatic variables affecting aridity were correlated with species richness in two habitats (WO and WOB) but, contrary to predictions from island biogeography, were not correlated with inselberg area and isolation in any of the three habitats. Species turnover in each of the three habitats was also influenced by aridity, being correlated with bioclimatic variables and with interplot geographic distance, and for HO and WO habitats with local site variables. At the outcrop level, species replacement was the dominant component of species turnover in each of the three habitats, consistent with expectations for long‐term stable landscapes. Our results therefore highlight high species diversity and turnover associated with granite outcrop flora. Hence, effective conservation strategies will need to focus on protecting multiple inselbergs across the entire climate gradient of the region.     

Microhabitat relationships among five lizard species associated with granite outcrops in fragmented agricultural landscapes of south‐eastern Australia

A fundamental part of developing effective biodiversity conservation is to understand what factors affect the distribution and abundance of particular species. However, there is a paucity of data on ecological requirements and habitat relationships for many species, especially for groups such as reptiles. Furthermore, it is not clear whether habitat relationships for particular species in a given environment are transferable to other environments within their geographical range. This has implications for the type of ‘landscape model’ used to guide management decisions in different environments worldwide. To test the hypothesis that species‐specific habitat relationships are transferable to other environments, we present microhabitat models for five common lizard species from a poorly studied habitat – insular granite outcrops, and then compared these relationships with studies from other environments in south‐eastern Australia. We recorded twelve species from five families, representing 699 individuals, from 44 outcrops in the south‐west slopes of New South Wales. Five lizard species were abundant and accounted for 95% of all observations: Egernia striolata, Ctenotus robustus, Cryptoblepharus carnabyi, Morethia boulengeri and Carlia tetradactyla (Scincidae). Linear regression modelling revealed suites of different variables related to the abundance patterns of individual species, some of which were broadly congruent with those measured for each species in other environments. However, additional variables, particular to rocky environments, were found to relate to reptile abundance in this environment. This finding means that species' habitat relationships in one habitat may not be readily transferable to other environments, even those relatively close by. Based on these data, management decisions targeting reptile conservation in agricultural landscapes, which contain rocky outcrops, will be best guided by landscape models that not only recognize gradients in habitat suitability, but are also flexible enough to incorporate intraspecies habitat variability.