物种多样性与植物群落的维持机制

物种多样性的形成与维持是生物多样性研究中的核心问题之一,形成了许多假说。剖析了群落物种多样性维持具有增加、减少和稳定共存三方面内容,着重阐明物种稳定共存的内因是物种的生物学与生态学特性差异,外因是生境具有小尺度的差异;群落生境异质性是其物种多样性维持的基础,并影响着群落的组织过程;群落的斑块镶嵌结构源于林隙形成的生境异质性,导致了物种多样性;群落斑块镶嵌结构是群落的基本属性,使群落的结构和功能得以长期维持等论点。最后,还以鼎湖山季风常绿阔叶林为例,对群落斑块镶嵌结构的形成及其对物种多样性维持和群落生产力构成与维持等方面的意义予以说明。     

How Useful are Ant Assemblages for Monitoring Habitat Disturbance on Grasslands in South Eastern Australia?

Native grasslands are one of the most endangered ecosystems in south eastern Australia. Conservation of grassland remnants and development of effective indicator groups to monitor their quality is a high priority. Recent surveys of epigaeic invertebrates have revealed several candidate groups for this. Ants are a popular focal group for invertebrate surveys in the region. The ant species richness and functional groups on four series of grassland sites in Victoria suggest that small scale heterogeneity is sufficiently high that the predictive indicator values of ants are limited, and that ants may not be sufficiently sensitive to floristic change to employ them alone in monitoring grassland condition in the region.     

Species richness of microcrustacea in subterranean freshwater habitats. Comparative analysis and approximate evaluation

Among terrestrial biomes the groundwater domain is generally considered to be a species poor environment. This view results, mainly, from the large geographic scale faunistic surveys (tens and hundreds of kilometres) and the traditionally coarse spatial scale (i.e. macroscale level) of ecological analysis. This view has been challenged by Margalef (1993) who suggests that high diversities are to be expected in the subterranean environment comparable to those found in the deep sea because of environmental similarities, e.g. low energetic resources. During the last twenty years long-term ecological research on much smaller scales, i.e. metres to hundred metres for interstitial media, a mesoscale approach, or kilometre size for karst systems was carried on. Long-term projects on limnic subsurface systems have shown that the species richness (SR) of the microcrustacea (Harpacticoida, Cyclopopoida, Ostracoda) is much higher than previously considered. Details on Harpacticoida of the alluvial bedsediments of a Pyreneean brook, the Lachein, and on Ostracoda of the alluvial sediments of the Danube plain (the phreatic zone), near Vienna, are presented. The SR values of the interstitial microcrustacea obtained through investigations at a mesoscale level are comparable to those of karstic and/or surface freshwater benthic water systems; they are lower than those of the deep-sea data sets for equivalent crustacean groups at a similar scale of investigation. From the data presented we infer the following points: (a) The subterranean waters are much more rich in species than earlier accepted, at least for some organismic groups like the microcrustacean copepods and ostracods. (b) Hence, to describe the still unknown fauna it is appropriate to sample the subsurface waters at an ecological scale. (c) Only studies during long-term ecological projects and with intensive, quantitative, sampling programmes allow a correct evaluation of the subterranean faunal diversity. (d) The species richness of a given subsurface site is strongly dependent on the structure of the habitats and the functioning of the underlying ecosystems. (e) Finally we consider the rationale for the protection of the subterranean faunal diversity.     

Winter coexistence in herbivorous waterbirds: Niche differentiation in a floodplain,Poyang Lake,China

The classical niche theory supports the idea that stable coexistence requires ecological differences between closely related species. However, information on waterbirds coexistence in the entirely landlocked freshwater system of Poyang Lake is not well understood, especially when the available biomass of their food in the area decreases. In this study, we tested the ecological segregation mechanisms in the 2015/2016 and 2016/2017 wintering periods among eight herbivorous waterbirds (including the Siberian crane Grus leucogeranus, hooded crane Grus monacha, white‐naped crane Grus vipio, common crane Grus grus, greater white‐fronted goose Anser albifrons, bean goose Anser fabalis, swan goose Anser cygnoides, and tundra swan Cygnus columbianus) at Poyang Lake. Using field observations and species niche and foraging habitat selection models, we investigated the abundance, distribution, and food sources of these eight waterbird species to quantify and compare their habitat use and ecological niches. Our results showed that niche segregation among the waterbirds, with respect to food types, time, and spatial location, allow them to coexist and use similar resources. The water level gradually receded in the sub‐lakes of the Poyang Lake, which could provide food sources and various habitats for wintering herbivorous waterbirds to coexist. We demonstrated that the differences in habitat use could mitigate interspecific competition, which may explain the mechanism whereby waterbirds of Poyang Lake coexist during the wintering period, despite considerable overlap in the dietary niches of herbivorous waterbirds.     

Density and habitat use of one of the last jaguar populations of the Brazilian Atlantic Forest: Is there still hope?

The jaguar (Panthera onca) plays an important role in maintaining biodiversity and ecological processes. We evaluated the status of a jaguar population in one of the last stronghold habitats for its conservation in the Atlantic Forest, the Rio Doce State Park (RDSP). We used a random survey design from 2016/17 to estimate jaguar abundance and density as well as its occupancy and detection probabilities in the entire Park''s area. To monitor for temporal fluctuations in density and abundance, we used a systematic survey design in the southern portion of the Park where jaguars were more recorded when using the random approach. We then conducted two surveys in 2017/18 and 2020. Our 2016/17 random survey revealed that jaguar density (0.11 ± SE 0.28 individuals/100 km²) was the lowest obtained for the species across the Atlantic Forest. We noticed that jaguar density increased three times from 2017/18 (0.55 ± SE 0.45 individuals/100 km²) to 2020 (1.61 ± SE 0.6 individuals/100 km²). Jaguar occupancy and detection probability were 0.40 and 0.08, respectively. The low jaguar occupancy probability was positively associated with smaller distances from lakes and records of potential prey. The detection probability was positively associated with prey detection, the rainy season, and smaller distances from lakes. Our work contributes to a growing awareness of the potential conservation value of a protected area in a human‐dominated landscape as one of the last strongholds for jaguars across the Atlantic Forest.     

Importance of Water Flow on Larval Growth and Pupation of Himalopsyche acharai, (Malicky and Chantaramongkol, 1989) (Trichoptera: Rhyacophilidae)

Larval mortality with growth and pupation rates of Himalopsyche acharai were compared between standing and flowing water in a laboratory from June to November 2004. In flowing water, 90% of larvae started pupal case building and 81.5% of them developed to pupae by October. In standing water, 92.6% died before pupation. The larvae reared in flowing water grew significantly faster than those in standing water. These results show why Himalopsyche acharai does not inhabit pools and slowly flowing streams.     

Microhabitat use by wild-ranging Cabrera voles <Emphasis Type="Italic">Microtus cabrerae</Emphasis> as revealed by live trapping

The conservation problems affecting the endangered rodent Microtus cabrerae are mainly related to habitat loss and fragmentation. In the present study, we examined the presence/absence of the species in a group of potentially suitable habitat patches, and then evaluated the microhabitat attributes of locations used by wild-ranging individuals within occupied patches. Our results revealed that shallow flooding and abundant grass cover appear to be important factors in determining the presence among localities, but high rush cover strongly determined the presence and habitat use by voles both among and within localities. The preservation of these microhabitat characteristics may be required to effectively ensure the occurrence and stability of M. cabrerae colonies.     

The ecology of the sandy estuaries of North Devon and Carmarthen Bay

The estuaries of the Taf, Tywi, Gwendraeth and Loughor (Carmarthen Bay, South Wales), and the Taw and Torridge (North Devon) were surveyed during the spring and summer of 1988, as part of a four year study of harbours, rias and estuaries in southern Britain commissioned by the Nature Conservancy Council. The aims of these surveys were to describe the major marine habitats and communities present in each estuary, and to assess their nature conservation importance. This paper outlines the results of these surveys, concentrating on the many environmental similarities between the six estuaries.     

Temporal organization of endocrine events underlying larval-larval ecdysis in the silkworm, Bombyx mori

The timing of ecdysis in the penultimate instar of Bombyx mori was demonstrated to be under the control of a circadian clock. The temporal organization of secretion of prothoracicotropic hormone (PTTH), ecdysone and juvenile hormone was studied with particular attention to the circadian control of the timing of hormone release. PTTH release occurs, at least, in the second and third night. The latter is responsible for evoking the larval ecdysis. Prothoracic gland initiates ecdysone secretion abruptly with a very short span after the second PTTH release and secrete enough amount of ecdysone for larval moulting, which takes place 11 h later. Juvenile hormone titer is relatively high before the second PTTH release and corpus allatum becomes dispensable for ensuring the larval moulting in 1.5 h. Based on these findings, interpretations for the endocrine system underlying precocious pupation and formation of intermediates, which are produced by neck ligation, are presented.