The Laterosensory Canal System in Epigean and Subterranean Ituglanis (Siluriformes: Trichomycteridae), With Comments About Troglomorphism and the Phylogeny of the Genus

The laterosensory system is a mechanosensory modality involved in many aspects of fish biology and behavior. Laterosensory perception may be crucial for individual survival, especially in habitats where other sensory modalities are generally useless, such as the permanently aphotic subterranean environment. In the present study, we describe the laterosensory canal system of epigean and subterranean species of the genus Ituglanis (Siluriformes: Trichomycteridae). With seven independent colonizations of the subterranean environment in a limited geographical range coupled with a high diversity of epigean forms, the genus is an excellent model for the study of morphological specialization to hypogean life. The comparison between epigean and subterranean species reveals a trend toward reduction of the laterosensory canal system in the subterranean species, coupled with higher intraspecific variability and asymmetry. This trend is mirrored in other subterranean fishes and in species living in different confined spaces, like the interstitial environment. Therefore, we propose that the reduction of the laterosensory canal system should be regarded as a troglomorphic (= cave‐related) character for subterranean fishes. We also comment about the patterns of the laterosensory canal system in trichomycterids and use the diversity of this system among species of Ituglanis to infer phylogenetic relationships within the genus. J. Morphol. 278:4–28, 2017. ©© 2016 Wiley Periodicals,Inc.     

喀斯特地区农村劳动力转移对生态恢复的影响及其区域差异——基于酉阳和沿河的农户调查数据

喀斯特地区的生态恢复对于促进国土空间的生态修复、实现区域生态安全具有重要意义。基于酉阳县和沿河县的383份农户调查数据，从微观的农户尺度运用Tobit模型分析喀斯特地区农村劳动力转移对生态恢复的影响，并关注其对酉阳县和沿河县生态恢复的影响差异。研究结果表明：①研究区劳动力转移现象明显，47.67%的农村劳动力发生了转移；②研究区生态恢复情况总体较好，酉阳县的生态恢复好于沿河县；③农村劳动力转移通过农业劳动力的流失效应和非农收入的替代效应促进了喀斯特地区的生态恢复；④劳动力转移的程度不同，对生态恢复的作用强度也不同。沿河相对滞后的劳动力转移程度，使得其生态恢复稍弱于酉阳。为促进喀斯特地区生态恢复，政府应有序引导农村劳动力向非农就业转移，提高转移农户的非农化程度。     

The interspecific competition presents greater nutrient facilitation compared with intraspecific competition through AM fungi interacting with litter for two host plants in karst soil

AM 真菌和枯落物互作下两种喀斯特植物种间竞争较种内竞争更能促进植物养分利用 枯落物是植物养分获取和土壤养分转化的关键载体。丛枝菌根(Arbuscular mycorrhizae, AM)对植物养分摄取的影响已被广泛认知。然而，在养分亏缺的喀斯特生境中，不同竞争方式的植物如何通过AM真菌和枯落物利用养分尚不清楚。本研究对两种喀斯特适生植物构树(Broussonetia papyrifera)和云贵鹅耳枥(Carpinus pubescens)进行种内竞争和种  间竞争种植处理，并通过幼套球 囊霉(Glomus etunicatum)接种或不接种处理，以及土壤中添加或不添加两物种叶片混合枯落物处理，测定了植物生物量以及氮、磷、钾浓度等指标，研究植物的生长和养分利用。研究结果表明，AM真菌对两种植物养分摄取影响不同，AM真菌显著提高了种内和种间竞争下构树的养分摄取量，但降低了云贵鹅耳枥的养分摄取量。种间竞争下接种AM真菌，枯落物添加促进了云贵鹅耳枥对氮的摄取，抑制了构树对氮的摄取。接种AM真菌和添加枯落物条件下，种间竞争的构树对氮、磷和钾的摄取量及云贵鹅耳枥对氮的摄取量均高于种内竞争；种间竞争下两物种养分竞争力呈现明显差异，即构树对磷和钾养分竞争力显著提高，对氮则不显著；云贵鹅耳枥仅对钾的养分竞争力显著降低，对氮和磷则无显著影响。这些结果说明，在AM真菌与枯落物相互作用下，两种喀斯特植物种间竞争较种内竞争更能促进植物养分利用。     

云南石林公园不同生境蚂蚁多样性研究

2003年5月下旬(雨季初期)和9月下旬(雨季后期),选择云南石林公园地带性植被滇青冈(Cyclobalanopsisglaucoides)林(原始林)、次生林、灌丛、草地、云南松(Pinusyunnanensis)林5种生境,采用陷阱诱捕法采集蚂蚁,共获蚂蚁8775头,隶属4亚科16属26种。优势种为阿诗玛无刺蚁(Kartidrisashima)、布立毛蚁(Pseudolasiusbournica)和重庆弓背蚁(Campontuschongqingensis)。两个季节蚂蚁多样性指数均以原始林最低,灌丛和松林最高。各生境蚂蚁群落相似性低,相似性系数在0–0.2609之间。结果显示,蚂蚁的多样性受多种环境因子影响;与地带性植被相比,蚂蚁群落在人为干扰的各种生境中已发生较大的变化。     

Patterns of endemism of the eastern North American cave fauna

Aim Over 250 species of obligate terrestrial cave‐dwelling animals (troglobionts) are known from single caves in the eastern United States. We investigate their geographical distribution, especially in relation to other troglobionts. We relate these patterns to taxonomic group, opportunities for dispersal and geographical location. Location Caves of the United States east of the Mississippi River. Methods We associated over 3000 records of more than 450 troglobiotic species and subspecies with hexagons of 1000, 5000 and 10,000 km² in size. We calculated Moran's I, black–white joins and cubic regression of endemics on non‐endemics at all three spatial scales. For 5000 km² hexagons, we modelled the spatial autocorrelation of the residuals of the cubic regression of endemics on non‐endemics. Results Differences among orders in percentage single‐cave endemism were not significant, except for Pseudoscorpionida, which was higher (69%) than any other order. At all three scales, Moran's I and black–white joins were significant, indicating a clumped distribution of both single‐cave endemics and other troglobionts. Spatial patterns were similar at all three scales and Moran's I was highest at 5000 km². The cubic fit of endemics to non‐endemics was consistently better, with less systematic error or residuals, than were linear or quadratic models. Residuals showed a significant geographical pattern with excess endemics in more southerly locations. Main conclusions There was both a non‐spatial and spatial component to the pattern of single‐cave endemism. The non‐spatial component was the association of high levels of single‐cave endemism with areas of high diversity of non‐endemics. It may be that both are high because of high secondary productivity. Spatially, single‐cave endemism is high in central rather than peripheral areas and in the southern part of the range. It is not higher in areas of more dissected limestone, which would reduce migration rates; if anything endemism is lower. Regional spatial effects are important, indicating that cave communities cannot be understood (or protected) in isolation.     

Ultrastructure of the peduncular aesthetascs of Speleonectes tanumekes (Crustacea, Remipedia) in comparison with crustaceans from stressful environments

Abstract. Osmotic stress associated with the freshwater environment and desiccation stress associated with the terrestrial environment may have a shortening effect on the length of the innervation of crustacean aesthetascs. Physical stress of the littoral environment may have a similar effect on the length of the cuticular portion of aesthetascs. The aesthetascs of crustaceans that inhabit these environments share a similar ultrastructural feature, which may help animals cope with these environmental stresses. This ultrastructural feature, the position of the basal bodies proximal to the lumen of the aesthetasc, is absent from the aesthetascs of crustaceans that occur in the typical marine environment. Interestingly, the ultrastructural feature associated with these stressful habitats is present in the peduncular aesthetascs of the remipede Speleonectes tanumekes , even though the environmental stresses that may invoke the reduction of aesthetascs are absent in the marine-cave environment where this animal occurs. The importance of the sensitivity of aesthetascs for survival in this lightless environment may result in a selective pressure that favors basal bodies to be positioned proximal to the lumen of the aesthetasc.     

Involvement of Microorganisms in the Formation of Carbonate Speleothems in the Cervo Cave (L'Aquila-Italy)

Much is known about the bacterial precipitation of carbonate rocks, but comparatively little is known about the involvement of microbes in the formation of secondary mineral structures in caves. We hypothesized that bacteria isolated from calcareous stalactites, which are able to mediate CaCO₃ precipitation in vitro, play a role in the formation of carbonate speleothems. We collected numerous cultivable calcifying bacteria from calcareous speleothems from Cervo cave, implying that their presence was not occasional. The relative abundance of calcifying bacteria among total cultivable microflora was found to be related to the calcifying activity in the stalactites. We also determined the δ ¹³C and δ ¹⁸ O values of the Cervo cave speleothems from which bacteria were isolated and of the carbonates obtained in vitro to determine whether bacteria were indeed involved in the formation of secondary mineral structures. We identified three groups of biological carbonates produced in vitro at 11°C on the basis of their carbon isotopic composition: carbonates with δ ¹³C values (a) slightly more positive, (b) more negative, and (c) much more negative than those of the stalactite carbonates. The carbonates belonging to the first group, characterized by the most similar δ ¹³C values to stalactites, were produced by the most abundant strains. Most of calcifying isolates belonged to the genus Kocuria. Scanning electron microscopy showed that dominant morphologies of the bioliths were sherulithic with fibrous radiated interiors. We suggest a mechanism of carbonate crystal formation by bacteria.     

Microbial Communities in Chesapeake & Ohio Canal National Historical Park and Their Function as Indicators of Water Quality

Abstract

The objective of this study was to establish meaningful relationships between prokaryotic community profiles and water quality parameters in different water bodies (spring, stream, cave, and mine) in the middle reach of the Chesapeake & Ohio Canal National Historic Park (C&O), Maryland. The microbial profiles in the water samples were determined using metagenomic analysis. The relationships between microbial phylogenetic profiles and water quality parameters were investigated using principal component analysis (PCA) and redundancy analysis (RDA). The most abundant phyla identified in most samples were Proteobacteria (55.4%), Bacteroidetes (12.3%), Actinobacteria (10.6%), Firmicutes (2.4%), Planktomycetes (1.8%), Verrucomicrobia (1.5%), Chloroflexi (1.5%), and Acidobacteria (1.3%), which are major bacterial and archaeal groups typically observed in natural freshwater environments. PCA showed that water chemistry was determined primarily by the geology of the site and the type of water source (i.e., spring, stream, cave, or mine). Most samples located in carbonate formations correlated with high alkalinity, inorganic carbon, and calcium, representing the typical karstic geochemistry. RDA shows that pH, electrical conductivity, temperature and nutrients including nitrate, phosphate, and sulfate, were significant determinants of the microbial ecology.     

Local genetic structure in the critically endangered,cave‐associated perennial herb Primulina tabacum (Gesneriaceae)

The local spatial genetic structures of cave‐associated plants are seldom studied. Given that these plants are mainly confined to small areas in and around the entrances of caves, we hypothesized that they might lack genetic structures at local scales. To test this hypothesis, we sampled two large populations (named D and T) of a critically endangered perennial herb, Primulina tabacum, which is endemic to karst caves in southern China. We analysed nine microsatellite loci and sequenced four chloroplast DNA (cpDNA) intergenic spacer regions to study the genetic diversity and structure within and between both populations. Both populations have distinct genetic characteristics. Samples from two subpopulations in population D showed considerable genetic divergence. This is not consistent with the hypothesis that P. tabacum has a weak genetic structure at a local scale. However, 94% of the individuals in population T shared the same multilocus genotype, which indicates little genetic structure within this population. The contributions of seed flow, pollen flow and (sub)population history to the genetic diversity and structure in each and both populations are discussed. Our study is the first to investigate local genetic diversity and structure in a cave‐associated plant, and provides valuable information for the sustainable conservation of such species. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 747–756.