植物的特有现象与生物多样性

特有现象是生物多样性的依据,多样性是特有现象的体现,特圾现象是种系分化的结果,特有现象的成因是多方面的,包括地貌因子、土壤因子、气候因子、边缘效应、海洋岛屿隔离以及自然杂交。全球各大的自然条件的多样性,促成了各大陆各异的特有现象和生物多样性,生物多样性是生命运动的属性,它是在系统发育过程中发展壮大的,因此,它的发展有生的,既具有普遍性,又具有特殊性,保护生物多样性是当前的迫切任务。     

Length-Weight Relationships for freshwater fishes from streams of the Atlantic Rainforest,State of Paraná, Brazil

This study reports the Length-Weight Relationships (LWR) for 10 freshwater fish species sampled in the Atlantic Rainforest, Southern Brazil. Sampling was conducted between 2016 and 2017, in nine streams, using electrofishing. Collected fishes were fixed in formalin, and thus some shrinking was unavoidable. The values of parameter b of the LWR (W = aL^b) ranged between 2.5 and 3.5. We report for the first time the LWR for seven species: Geophagus iporanguensis, Isbrueckerichthys duseni, Hypostomus interruptus, Kronichthys lacerta, Chasmocranu lopezi, Astyanax lacustris e Neoplecostomus ribeirensis. We highlight the importance of the LWR data in supporting further studies on fish stocks and environment in the Atlantic Rainforest, thereby contributing to the database needed to develop fisheries management and maintenance of ecosystem services.     

Patterns of plant species endemism in Ecuador

Distribution patterns of plant species endemic to Ecuador and adjacent parts of southern Colombia and northern Peru are analysed on the basis of information in the Flora of Ecuador. A total of 827 restricted-range species were found, many of which are known from extremely small areas, often only one or a few localities. A total of 27% of the species treated in the Flora of Ecuador are endemic to that country. The overall proportion of endemic and restricted-range species is greater in the Andes than in the lowland areas on either side of these mountains; particularly the southern Andes appears to be very rich in endemic species. Spatial analysis of distribution data results in the recognition of 15 floristic elements and 18 geographical endemism regions in Ecuador, the characteristics of which are discussed. Comparison with distribution patterns of restricted-range bird species show a general correspondence, with the main difference that birds tend to be more widely distributed than plants along the Andes. Comparison of the results with the location of national parks and other protected areas shows that the endemic floras in the northern and eastern parts of the country are much better protected than those of the southern and western parts.     

Tripterygiid Fishes of New Caledonia, with Zoogeographical Remarks

The Tripterygiidae of New Caledonia are revised and their zoogeographical relationships discussed. A total of 27 species is recognized from the territory; three species are recorded from New Caledonia for the first time [Enneapterygius howensis Fricke, 1997; Enneapterygius rhabdotus Fricke, 1994; Helcogramma trigloides (Bleeker, 1858)]. From Grande Terre, 26 species are known, with four species recorded for the first time. Seven species occur at the Ile des Pins (all new records); from the Chesterfield Islands, six species of tripterygiid fishes have been recorded; and from the Loyalty Islands, 17 species are known, with three species recorded from the island group for the first time: 15 species from Ouvéa, 11 species from Lifou (eight new records) and five species from Maré (three new records).     

地面节肢动物营养类群对土地覆被变化和管理扰动的响应

近几十年来,黑河中游荒漠绿洲过渡带大面积天然沙质草地被转变为农田和防风固沙人工林,然而目前尚缺乏土地利用/覆被变化和管理措施对地面节肢动物多样性形成和维持影响的系统研究。以天然沙质草地转变为的人工梭梭灌木林、人工杨树林、人工樟子松林和农田为研究对象,以天然草地为对照,通过对5种样地地面节肢动物群落的调查及非生物环境因子的测定,采用典范对应分析(CCA)等方法,系统探讨了土地覆被和管理强度(天然草地和人工梭梭林实施零管理、杨树和樟子松人工林实施灌溉管理、农田实施灌溉和施肥管理)变化对地面节肢动物营养类群组成、数量和物种丰富度的影响。主要结果是:(1) 在干旱环境下,单纯改变土地覆被并不会导致土壤环境的显著变化,而高强度的管理扰动加速了土壤环境的演变过程。(2)不同土地覆被和管理措施对营养类群组成及其数量和丰富度的调控作用不同,将天然草地转变为杨树和樟子松人工林和农田后,显著提高了捕食性和植食性类群的比例,降低了'腐食性+杂食性’类群的比例;转变为人工梭梭林后显著降低了3种营养类群的数量;转变为人工杨树林后显著降低了'腐食性+杂食性’类群数量;转变为人工樟子松林后显著增加了植食性类群数量而降低了其它类群的数量;转变为农田后显著增加了植食性类群数量而降低了'腐食性+杂食性’类群数量。(3)影响捕食性动物分布的关键环境因子是地面温度、土壤硝态氮和田间持水量,影响植食性动物分布的关键因子是土壤粘粉粒、土壤硝态氮、土壤容重和pH值,影响'腐食性+杂食性’动物分布的关键因子是地面温度和田间持水量。主要结论是:土地覆被变化与管理措施相互作用对地面节肢动物群落组装过程及其多样性形成具有重要调控作用,尽管其相对重要性不同。     

Problems with areal definitions of endemism: the effects of spatial scaling

The concept of endemism is useful in quantifying the biological uniqueness of an area, and has been used by many authors as a meaningful alternative to simple species richness. The traditional definition of endemism includes those species with ranges restricted to a particular region, and therefore is useful only in reference to that region. To compare different regions, however, a standardized approach is required, so several authors began using area-based definitions. Accordingly, those species with ranges smaller than a particular area (e.g. 50,000 km ²) are deemed endemic. Nevertheless, several problems are associated with this approach: as the area threshold changes, scaling of endemism also changes, producing a different picture of endemism for each spatial scale. Moreover, the areal definition assumes equal levels of heterogeneity in different landscapes (clearly a simplification), which overemphasizes fine-grained regions. Herein, the importance of distinguishing the regional definition (endemism) from the areal definition (range restriction) is emphasized, and investigators are encouraged to consider multiple spatial scales and geographic dimensions in evaluations of biodiversity.     

The elevational gradient of Andean plant endemism: varying influences of taxon-specific traits and topography at different taxonomic levels

Aim Little is known about the elevational gradient of plant endemism. It is mostly assumed that patterns are determined by topographical factors such as area of elevational belts and degree of habitat fragmentation, but comparative studies of different plant taxa along the same elevational gradient are lacking. The aim was to compare the elevational patterns of plant endemism of the entire flora and selected families and genera in a search for commonalities. Methods The elevational patterns of endemism for the entire Ecuadorean vascular plant flora, for twenty‐seven selected families, and for twenty‐four selected genera based on the Catalogue of Vascular Plants of Ecuador were analysed. Results Elevational patterns of endemism were non‐random at all taxonomic levels but there was no common elevational pattern. Rather, the study groups showed a wide variety of independent patterns at all taxonomic levels. Most groups had hump‐shaped patterns with maxima at different elevations and mostly at the same or at higher elevations than the maxima of species richness. The overall flora showed highest endemism in the narrowest and most fragmented elevational belts, presumably because of the consequent fragmentation of species populations. Main conclusions Patterns of endemism appear to be influenced both by taxon‐specific ecological traits (e.g. life form, reproduction, dispersal, demography, spatial population structure, competitive ability) in their specific interaction with historical processes and by environmental factors such as topographical fragmentation. The degree to which these influences become visible along the elevational gradient are determined by which combination of species is analysed: for a given genus or family, taxon‐specific traits dominate the patterns, for the entire flora taxon‐specific patterns are blurred by averaging and the signal of topography emerges. Beyond the elevational gradient as such, this study shows that the frequently stated assumption that given biogeographical settings lead to similar patterns of endemism among different taxa is wrong.     

Biodiversity in the Gulf of Guinea: an overview

Patterns of species-richness and endemism in the Gulf of Guinea reflect the region's biogeographic history. Bioko is a continental-shelf island that was recently connected to the African mainland, whereas Príncipe, São Tomé and Annobón are truly oceanic and have never been connected with each other or with the mainland. As a result, Bioko supports a much more diverse flora and fauna but with relatively low levels of endemism at the species level, whereas the oceanic islands are relatively depauperate because of their isolation but rich in endemic taxa. Species endemism is 0–3% on Bioko for angiosperms, bats, birds, reptiles and amphibians, compared with much higher values on Principe for these same taxa of 8% (plants) to 100% (amphibians), on São Tomé between 14% (plants) and 100% (amphibians), and on Annobón 0% (bats) to 71% (reptiles). On a global scale, for their size both Príncipe and São Tomé support unusually high numbers of single-island endemic species of birds, reptiles and amphibia. For its tiny size, Annobón is also notable for its endemic birds and reptiles. Among terrestrial molluscs the rates of endemism are in general higher than for plants and vertebrates, from ca 50% on Bioko to ca 80% on the oceanic islands. In contrast and as might be expected, only Bioko supports a rich freshwater fish fauna and it contains many endemic taxa, whereas the oceanic islands support only a few salt-tolerant species. The Gulf of Guinea islands are also important for their marine organisms, amongst which coral reef fish and marginellid molluscs show high levels of endemism, though they are not especially species-rich. The Gulf of Guinea islands are of great interest to conservationists and evolutionary biologists. Each island, of greatly differing size and degree of isolation, has acquired its unique sub-set of plants and animals separately from the neighbouring mainland, followed by adaptive radiations in situ. For this reason the conservation value of the archipelago as a whole is greater than the sum of the biodiversity contained in its individual islands. Conservation initiatives in the Gulf of Guinea should therefore ensure that representative terrestrial, freshwater and marine habitats and groups of organisms are targeted in a co-ordinated manner among the islands.     

Biodiversity and environmental stability

Although levels of biological diversity may seem to be equivalent in different areas, diversity is created and maintained by a range of different ]processes: overlap of habitat on gradients; a dynamic mosaic of communities; and accumulation and evolution of taxa in extremely stable areas. These different communities will respond in very different ways to disturbance. The most fragile are those whose component taxa are genetically adapted to the stability of a predictable environment. These areas are often under pressure from local rural populations and require intensive local conservation management actions. In other areas, where diversity is adapted to dynamism, communities are more resilient to disturbance and conservation can be best effected by policy instruments.