内蒙古武川县农田退耕还草对大型土壤动物群落的影响

用手拣法采集大型土壤动物,应用个体数、类群数、多样性指数等指标分析了内蒙古武川县农田退耕还草管理下大型土壤动物群落的变化.共捕获大型土壤动物49类1479只,隶属于3纲、7目、41科;农田退耕后大型土壤动物的类群数、个体数和生物量均有增加趋势;Margalef丰富度指数(D_Ma)和密度-类群指数(DG)显示,农田退耕还草后大型土壤动物群落多样性明显增加,但由于退耕时间短,Shannon-Wiener多样性指数(H′)和Pielou均匀度指数(E)并不比农田高;不同动物类群对退耕还草的响应不同.退耕后采用紫花苜蓿或紫花苜蓿+蒿属植物的人工种植管理方式较为合适.     

三种温带森林大型土壤动物群落结构的时空动态

对帽儿山3种典型森林群落大型土壤动物进行了连续6个月的野外调查研究。通过系统分析,共获得大型土壤动物3604只,隶属于3门6纲17目50科。其中正蚓科(Lumbricidae)、线蚓科(Enchytraeidae)和石蜈蚣目(Lithobiomorpha)为优势类群,常见类群11类。结果表明:(1)水平分布上,密度和生物量红松人工林最高,其次为硬阔叶林,蒙古栎林最少;类群数硬阔叶林最多,蒙古栎林最少;香农指数和丰富度指数均为蒙古栎林最高,红松人工林最低;优势度指数与两者相反;均匀度指数蒙古栎林最高,硬阔叶林最低;(2)垂直分布上,个体密度、类群数及生物量均差异显著(P < 0.001)。3个样地大型土壤动物个体密度表聚性明显;类群数红松人工林自凋落物层向下减少,硬阔叶林和蒙古栎林0-10 cm最多;生物量在0-10 cm土层最大;香农指数随深度增加而减小,优势度指数则相反;(3)在时间变化上,5月和10月个体密度和类群数较多,9月生物量最大;香农指数和优势度指数差异显著(P < 0.01),其他指数各月间无明显差异;(4)与土壤环境因子关系上,总有机碳含量与类群数、个体密度及生物量显著正相关,容重与香农指数显著负相关;典型对应分析结果表明,不同类群大型土壤动物与环境相关性不同。     

围封对内蒙古退化典型草原大型土壤动物群落多样性的影响

为了探讨不同围封年限对内蒙古退化典型草原大型土壤动物群落多样性的影响,选取位于内蒙古草原生态系统定位站的退化围栏封育19和32年草地为研究样地,以围栏外自由放牧草地为对照,调查了0~10、10~20、20~30 cm不同土层大型土壤动物群落组成。共采集到大型土壤动物984只39类,隶属于2门、4纲、9目。各样地的优势类群不同,封育32年样地为步甲科、叶甲科幼虫、叶蝉科;封育19年样地为叶蝉科、步甲科、叩甲科幼虫;放牧样地为叩甲科幼虫、蚁形甲科。大型土壤动物丰富度、Shannon指数、均匀度指数、密度-类群指数、密度都表现为封育19年样地最高,封育32年样地次之,放牧样地最低,而优势度指数则呈现出相反变化趋势。垂直分布3样地均表现出明显的表聚现象,随着土壤深度增加,个体数和类群数均逐渐递减。围封后土壤含水量、土壤p H、土壤全磷和有机质含量均发生了显著变化(P0.05),而土壤容重、孔隙度和土壤全氮含量变化不显著(P0.05)。大型土壤动物密度、Shannon指数、均匀度指数与土壤含水量呈极显著正相关(P0.01)。研究表明,围封对内蒙古退化典型草原大型土壤动物群落水平和垂直分布具有显著的影响,围封样地大型土壤动物的个体数和类群数明显高于放牧样地。同时,围封有助于内蒙古退化典型草原土壤理化性质的改善。     

刈割活动对松嫩草原碱化羊草草地土壤线虫群落的影响

应用类群数、个体密度、多样性指数和功能类群指数等多个群落参数, 研究刈割活动对松嫩草原碱化羊草草地土壤线虫群落特征的影响。本研究共捕获土壤线虫8,335条, 分别隶属于线虫动物门2纲7目23科40属。结果表明, 与围栏封育样地相比, 刈割活动样地中线虫个体密度和类群数显著减少, 群落多样性指数(H′)、均匀度指数(J)和丰富度指数(SR)虽低于围栏封育样地, 但两类处理间差异不显著, 表明刈割活动尽管明显降低土壤线虫群落个体密度和类群数, 但对土壤线虫群落多样性的影响有限; 样地间PPI／MI值差异明显, 表明刈割活动在一定程度上确实改变了土壤线虫功能类群组成, 其中受影响的主要是非植物寄生线虫。     

成都市温江区不同栽植年限园林植物土壤动物群落特征

对成都市温江区不同栽植年限园林植物土壤动物群落特征进行调查分析,4次取样共捕获土壤动物10258只,隶属26目78科。不同园林植物土壤动物类群数存在显著差异,基本以红花檵木、银杏样地最高,结缕草样地最低,各栽植年限土壤动物类群数均低于周边农田和撂荒地;桂花样地土壤动物类群数、个体数受季节变化影响较小,其余样地土壤动物个体数具有明显的季节动态,而类群数随季节变化不显著;土壤动物多样性指数受园林植物种类及栽植年限影响,银杏样地土壤动物密度-类群指数(DG)及Margalef丰富度指数(D)和结缕草样地土壤动物Shannon多样性指数(H)及D指数均随栽植年限增加而显著降低,桂花样地土壤动物DG指数、D指数则随栽植年限增加显著升高,红花檵木样地土壤动物多样性各指数随栽植年限增加未表现规律性变化,其中土壤动物DG、D、H指数各栽植年限基本以桂花样地最低;聚类及典型关联分析(CCA)表明,园林植物种类对样地生境的影响大于栽植年限,土壤动物对不同生境因子响应不同,其中速效P、土壤pH对土壤动物影响较大。土壤动物群落特征受园林植物种类、栽植年限及栽培管理方式的影响,而过度人为干扰、单一植物连栽会对土壤动物产生不利影响,并可能导致土壤地力衰退。     

地埂植物篱对大型土壤动物多样性的影响

为了解地埂植物篱作为农田边界对于大型土壤动物多样性的影响,2006年冬季和2007年春季对桑园、桑埂、橘园、橘埂和农田大型土壤动物群落结构进行了调查,共获得大型土壤动物 4533只,隶属于3门、9纲、24类.结果表明,不同土地利用方式大型土壤动物群落的个体密度、类群数和DG多样性指数均存在显著差异.无论在冬季还是在春季,地埂植物篱桑埂和橘埂的个体密度、类群数和DG多样性指数均显著高于农田;冬季桑园和橘园的个体密度、类群数和DG多样性指数也显著高于农田.大型土壤动物群落的个体密度和类群数在垂直分布上与土壤含水量、全N和有机质含量的垂直分布规律一致,均随着土层深度的增加而递减.主成分分析表明,桑埂、橘埂和橘园的大型土壤动物群落组成与桑园和农田存在显著差异,桑园与农田也存在显著差异.地埂植物篱的存在对于大型土壤动物多样性保护具有重要意义.     

轮伐期前后不同密度巨桉(Eucalyptus grandis)人工林土壤动物群落结构特征

在前期巨桉(E.grandis)人工林土壤生物多样性在轮伐期前(4年左右)降低,此后随林龄显著升高的研究基础上,在四川省丹棱县选择轮伐期前即4年和轮伐期后即8年的不同密度(D1:2000, D2:1600, D3:1200株/hm~2)巨桉人工林,研究了其土壤动物群落结构特征。结果显示:1)共捕获土壤动物2904只,隶属于4门8纲22目70科,其中大型土壤动物541只,以蚁科和康叭科为优势类群;中小型土壤动物2363只,以大翼甲螨科、等节虫兆科和线虫为优势类群。2)土壤动物类群数、个体数和密度随林分密度和林龄具有显著差异,4年生林地大型土壤动物个体数随密度降低显著增加,8年生巨桉人工林中小型土壤动物个体数及类群数随密度降低均显著增加;土壤动物个体数及类群数除D1密度时4年高于8年,其余密度均表现为8年高于4年。3)林分密度对土壤动物多样性指数有显著影响,4年生林地大型土壤动物Margalef丰富度指数随密度降低显著增加,8年巨桉人工林中小型土壤动物Shannon-wiener指数及Margalef丰富度指数随密度降低显著升高。4)巨桉人工林大型土壤动物以杂食性为主,枯食性次之,中小型土壤动物以腐食性为主,杂食性次之。5)RDA分析显示,林分密度、土壤含水量和土壤pH为对土壤动物的主要作用环境因子,4年时对奥甲螨科、长角长虫兆科、寄螨科、隐翅甲科、丽甲螨科等类群影响较大;8年时对线虫、蜚蠊科、康叭科、厉螨科、棘虫兆科等类群影响较大。为此,延长轮伐期、降低林分密度可改善巨桉人工林土壤动物生境、增加土壤动物多样性、促进土壤动物群落结构稳定性。     

黑土区免耕秸秆不同覆盖频率下大型土壤动物群落结构特征

为探讨免耕玉米秸秆不同覆盖频率下大型土壤动物群落组成、结构和季节变化,于2015年4、7和10月,在中国科学院吉林省梨树县保护性耕作试验基地,对免耕玉米秸秆不同覆盖频率各样地进行大型土壤动物群落调查。结果获得大型土壤动物26类,隶属2门5纲13目,线蚓为优势类群,不同类群在各处理样地所占数量比例存在差异。免耕秸秆不同覆盖频率样地大型土壤动物个体密度、类群丰富度和多样性指数均高于常规耕作样地。各处理样地大型土壤动物群落个体密度的最高值均出现在10月,类群数量和多样性则以7月最高。不同土壤动物类群对免耕秸秆覆盖频率增加的响应存在差异。相对常规耕作,免耕秸秆覆盖频率的增加可显著提高腐食性类群密度。     

川西北冷杉林恢复过程中土壤动物群落动态

为了掌握川西北冷杉林群落恢复过程中土壤动物群落的变化动态,2008年4月对川西北地区的原始冷杉林和50a冷杉林的土壤动物群落进行了调查。共捕获大型土壤动物287个,33科(类);中小型土壤动物4681个,57科(类)。50a冷杉林大型土壤动物群落的类群数和密度显著高于原始冷杉林(P<0.05);中小型土壤动物群落的类群数和密度分别显著低于(P<0.05)和高于原始林(P<0.05)。PCA排序结果表明两个不同年龄段间的大型和中小型土壤动物群落结构均存在明显差异,但大型土壤动物群落间的相似性系数小于中小型土壤动物群落,表明大型土壤动物群落的恢复速度慢于中小型土壤动物群落;且大型和中小型土壤动物群落间的Srenson相似性均低于Morisita-Horn相似性,进一步表明群落物种组成的恢复速度较慢,而优势类群及常见类群的数量恢复较快。50a冷杉林的大型和中小型土壤动物的多样性指数H、丰富度指数D和优势度指数C均高于原始冷杉林,而均匀度指数E则低于原始冷杉林,但仅大型土壤动物的丰富度指数D存在显著差异(P<0.05)。以上研究结果表明,冷杉林的恢复过程可显著提高大型土壤动物群落多样性,且土壤动物群落的组成恢复较慢,而优势类群和常见类群的个体数量恢复较快。     

基于黑土农田生物多样性监测样地的地表大型节肢动物群落特征

农田生态系统是陆地生态系统的重要组成部分,是全球生态与环境研究的关键区之一.为了研究农田生物群落构建过程,探索其多样性维持机理,本研究于2015年在东北典型黑土区建立了16 hm²的农田生物多样性监测样地,按照作物生长期,于玉米生长大喇叭口期(8月初)、抽穗期(9月初)和成熟期(10月初)对陷阱法获取的地表大型节肢动物进行了统计分析.结果表明: 3次调查共获得地表大型节肢动物5284只,隶属于节肢动物门3纲12目32科47种.调查中优势类群3类,常见类群11类.节肢动物营养功能群中植食性和杂食性节肢动物所占比重较大.地表大型节肢动物物种数量和个体数量随作物生长期有显著变化.9月初节肢动物的Shannon多样性指数、Margalef丰富度指数、Pielou均匀度指数相对较高,8月初Simpson优势度指数较高.从不同物种的变异系数(CV)及群落空间插值可以看出,节肢动物群落在水平方向上存在异质性.在与土壤环境因子关系上,双变量相关分析表明,不同月份地表大型节肢动物总个体数与土壤pH值、有机质、全氮、含水量的相关性均未达到显著性水平;典范对应分析(CCA)进一步表明,优势类群和常见类群对环境因子具有较强的适应能力,在研究区内分布广泛.农田生物多样性监测样地内地表节肢动物物种组成丰富,在作物不同生长时期地表节肢动物群落组成及空间分布格局具有明显的变化过程.农田生物多样性监测样地通过大尺度、长时间对样地内土壤动物空间过程进行监测,可以为解决群落生物多样性形成和维持机制提供重要手段.     

春季解冻期不同纬度兴安落叶松林的土壤微生物生物量

以移栽自兴安落叶松林自然分布区内4个纬度梯度(塔河、松岭、孙吴和带岭)的8年生兴安落叶松林为对象,于移栽3年后(2007年)的春季土壤解冻期,采用氯仿熏蒸浸提法测定了4个纬度梯度(处理)土壤的微生物生物量碳(C_mic)和微生物生物量氮(N_mic)的时间动态.结果表明：在相似基质和相同气候条件下,移栽自4个纬度梯度的兴安落叶松林春季土壤解冻期的C_mic和N_mic平均值差异显著,呈随纬度升高而减少、随土层加深而下降的分布格局.其中塔河、松岭、孙吴和带岭的C_mic平均为554.63、826.41、874.81和1246.18 mg·kg^-1,而N_mic分别为70.63、96.78、79.76 和119.66mg·kg^-1.C_mic和N_mic在解冻前达到最大值;解冻初期迅速下降;在冻融交替阶段变化不显著,且维持在较低水平;在解冻末期,来自低纬度的带岭和孙吴的C_mic回升较快. 春季冻融期土壤温度和含水量对C_mic和N_mic的影响显著,其影响程度随冻融阶段而变化.土壤微生物生物量与解冻前的土壤温度呈负相关,与整个解冻期间的土壤含水量呈指数关系.     

Studies on species diversity of Larix chinensis community ecotone

The communities of Larix chinensis and their ecotone in Qinling Mountains were investigated by sampling belt method. Species richness, Simpson diversity, Shannon-Weiner diversity, PIE and Pielou evenness indices of vascular plants in their communities and ecotone were calculated. Structure and composition of the communities in 6 sampling belts within the sites were analyzed. The results showed that the edge effect was obvious in the ecotone with a less changing environment (such as soil and terrain) and acute variation of composition and structure, while inconspicuous or even none in the ecotone with worse environmental condition (such as great space fluctuation). It is apparent that the edge effect of community was affected by soil and terrain, but not by microclimate. __________ Translated from Guibaia, 2005, 25 (2)[译自: 广西植物, 2005,25(2)]     

Algae, macrofaunal assemblages and temperature: a quantitative approach to intertidal ecosystems of Iceland

Algae and the associated macrofauna in two Icelandic intertidal ecosystems under cold and warm influence, respectively, were studied with respect to algae-macrofauna relationships and a possible effect of temperature on community structure. Two sites in Iceland were selected, Sandgerdi ligthhouse (64°8′N 22°40′W) on the southwestern coast, and Grimsey Island (66°33′N 18°04′W), in the north, on the Arctic Circle, where sea temperature is considerably lower (5° approximately). The biomass of algae and the number of species of algae and macrofauna were higher in Sandgerdi than in Grimsey, and the patterns of diversity, evenness, biomass and abundance also differed between the sites. In the intertidal zone of Sandgerdi, a total of 28 species of algae and 45 species of macrofauna were identified whereas only 16 algal species and 27 macrofaunal species were found in Grimsey. Canonical correspondence analysis (CCA) using algal biomass as the environmental variable were conducted, and revealed significant relationships between algae composition and the associated macrofauna; some macrofauna taxa showed specific trophic or refuge relationships with algal species. According to the CCA, Corallina officinalis showed the highest correlation with macrofaunal assemblages in both study sites. However, correlations between macrofauna and other algae differed between Grimsey and Sandgerdi. The present study, together with additional observations in Greenland waters, shows a general decrease of species richness and diversity towards the north which may primarily be due to the temperature regime.     

Diversity,abundance and composition in macrofaunal molluscs from the Ross Sea (Antarctica): results of fine-mesh sampling along a latitudinal gradient

The Latitudinal Gradient Program (2002–2011) aimed at understanding the marine and terrestrial ecosystems existing along the Victoria Land coast (Ross Sea), an area characterized by strong latitudinal clines in environmental factors. During the program’s voyage of the Italian RV “Italica” in 2004, a fine-mesh towed gear, the “Rauschert dredge”, was deployed for the first time at 18 stations in four latitudinal distinct shelf areas between ~71°S and ~74°S. The collected samples contained undescribed species and new records for the Ross Sea from a variety of different marine taxa. Here, we describe the molluscan fauna and investigate evidences for latitudinal effects on molluscan diversity, abundance and assemblage composition. No significant latitudinal trends were detected: while diversity did not vary significantly with latitude, species richness showed an apparent but non-significant decrease with increasing latitude. Beta-diversity was found to be high both within and between latitudinally distinct shelf areas. A large fraction (~20 %) of the collected molluscs corresponded to new species records for the Ross Sea or undescribed species. Rarity in Antarctic molluscan occurrences was confirmed, with singletons (i.e. species represented by only a single individual) accounting for a 22 % and uniques (i.e. species occurring in one sample only) for a 43.5 % of the total presence. Our study of the smaller macrofaunal benthic fraction showed that Antarctic marine research still has far to go to have robust reference baselines to measure possible changes in benthic communities, even in the case of the assumed well-known, well-sampled and well-studied group of Ross Sea shelf molluscs. We advocate the use of fine-mesh trawling gears for routine sampling activities in future Antarctic expeditions to assess the full marine biodiversity.     

Biogeography and macroecology of phorid flies that attack fire ants in south-eastern Brazil and Argentina

Aim Saevissima group fire ants, Solenopsis richteri and S. invicta, have become serious pests when introduced from Argentina and Brazil to other continents. In South America, Solenopsis are distributed across a great variety of habitats and climates. In North America, S. invicta, introduced free of phorids, now ranges from coast to coast in the south. Success in introducing particular Pseudacteon as agents for the biological control of fire ants has varied across climatic zones. We aimed at assembling all the information about fire ant phorids from Argentina and Brazil, to estimate their richness and geographical ranges, to perform a climatic analysis for these distributions, to define groups and climate‐based communities, and to test and elucidate Rapoport's biogeographical rule. Location Argentina and Brazil (South America). Methods From field and museum collections and historical records, we developed a database of fire ant‐specific phorids throughout their known geographical range. A total of 123 sites with values for 15 climatic variables were mapped between 10° and 38° SL and between 35° and 65° C WL for the presence/absence of phorids. We calculated species richness across all sites combined, and for each phytogeographical region, using rarefaction curves, and ICE and Mmean estimators. We calculated mid‐latitudinal points, geographical ranges and areas for each species. The correlation between mid‐latitudinal point and ranges/areas was tested against a null model generated from the randomization of the raw distributional data. We used several types of multivariate analyses to distinguish groups of phorids by phytogeographical regions, hosts and climate, to find gradients of climate throughout the studied area, to define phorid communities in terms of their relationships with gradients of climate, and to test a mechanism for Rapoport's rule. Results Richness estimations using ICE and Mmean estimators were similar or higher than the observed values depending on the phytogeographical region. Cluster multivariate analyses based on climatic, phytogeographic and host data revealed distinct groupings of Pseudacton. The ‘cerrado’ group was confined to tropical savanna areas. A more ‘widespread’ group included ‘Chaco’ and ‘Maritime’ subgroups defined by their respective association with extreme temperatures or precipitation. Ordination multivariate analyses showed (1) two climatic gradients throughout the study area: one of temperature and the other of precipitation, and (2) that climatic variables significantly explained the observed assemblages of phorids. Positive and negative signs of the eigenvalues from the main axes of a canonical correspondence analysis allowed us to define eight communities whose geographical distribution resembled that of phytogeographical regions. We found a significant and positive correlation between geographical areas and mid latitudinal points, and furthermore, the Mantel test based on climatic variables suggested a mechanism for Rapoport's rule applying in the case of Pseudacteon. Main conclusions Pseudacteon species with greater mid‐latitudinal points occupy broader geographical areas and confront more stressful environmental conditions. Because the composition of Pseudacteon communities is largely determined by climatic variables, the correspondence between climates at sites of origin vs. sites of release should be an important consideration in choosing specific phorids for biocontrol efforts.     

Composition and community structure of pelagic copepods in the Indian sector of the Antarctic Ocean during the end of the austral summer

The present paper describes latitudinal and vertical changes in the composition, abundance and diversity of copepods in the Indian sector of the Antarctic Ocean, during the end of austral summer along a transect on 66°30′E between 43 and 62°S, within three layers (600–0, 200–0, 100–0 m). Highest copepod densities were noted in the central part of the transect, between the Antarctic Divergence and the Antarctic Convergence, with a maximum in the Antarctic Divergence zone, particularly in the upper levels of the water column. A total number of 80 copepod species were identified over the entire survey area. The south end and the central part of the transect comprised a small number of species. North of the Antarctic Convergence, this number increased markedly with the progressive disappearence of those species characteristic of Antarctic waters and their replacement by temperate and subtropical species. Generally, small copepods, particularly Oithona similis, Oithona frigida and Ctenocalanus citer, dominated in numbers in both Antarctic and sub-Antarctic areas. The contribution of large species to total copepod numbers was much lower, with Calanus simillimus in the central part of the transect, Pleuromamma borealis in the subtropical zone and Calanus propinquus in the southern part. Correspondence analysis showed a marked latitudinal gradient in population structure with four groups of samples and species corresponding to four latitudinal zones. Community structure (species richness, relative dominance index, evenness, Shannon species diversity index) and species abundance patterns (as rank-frequency diagrams) suggested that the maturity and species richness increased gradually from south to north. A low diversity index and evenness were observed in the area of the Antarctic Divergence, whereas the convergence zone showed high diversity and evenness. Conversely, the frontal zone showed high diversity and evenness. Distribution appeared unrelated to chlorophyll concentrations and on the large scale was related to the hydrologic characteristics. Received: 8 May 1996 / Accepted: 27 August 1996     

考洲洋人工种植红树林湿地大型底栖动物群落环境响应

2017年以来,广东省惠州市在考洲洋潮间带开展了大规模人工种植红树林生态修复工程,但考洲洋人工种植红树林湿地大型底栖动物群落的环境响应未见报道。根据2018-2019年四个季节在考洲洋盐洲大桥附近红树种植1-2年（X断面）和5-6年（Y断面）的两处湿地的大型底栖动物定量取样数据,分析了人工红树林湿地大型底栖动物的时空格局及其环境响应。方差分析表明,Y断面冬季的大型底栖动物群落的物种数、栖息密度、生物量、多样性指数（H''）和丰富度指数（d）,以及夏季的栖息密度均随潮高（海平面高程）降低而增加;而Y断面冬季的均匀度指数（J）、夏季的H''和J则是随潮高降低而减少。聚类（Cluster）和非度量多维尺度（nMDS）分析表明冬季和夏季X断面和Y断面大型底栖动物群落相似性较低,而春季和秋季X断面和Y断面大型底栖动物群落相似性较高。冬季和夏季最大潮高、潮差、大型底栖动物物种数、栖息密度、H''和d较春季和秋季的高。红树种植1-2年的X断面大型底栖动物物种数、H''和J低于种植5-6年的Y断面。上述结果证实潮汐和红树种植年限影响考洲洋红树林湿地大型底栖动物的群落结构,研究结果可为大型底栖动物多样性保护和生态修复提供基础资料。     

Colonization of a host tree by herbivorous insects under a changing climate

Climate warming has been predicted to increase the abundance of herbivorous insects. Together with concurrent poleward shifts in many insect species this may increase herbivore pressure on plants. However, the manner in which plants at higher latitudes become colonized by herbivorous insects in the future is unknown. We established a translocation experiment using 26 micropropagated silver birch Betula pendula genotypes from six populations originating from 60°N to 67°N, to study the susceptibility of the translocated birches to local herbivores. The birches were planted at three different latitudes in Finland (60°N, 62°N and 67°N). We studied the effect of source population and latitudinal translocation on herbivore density, species richness, and community composition among the genotypes growing in the same environmental conditions in two years; 2011 and 2012. The source population explained the variation in the herbivore density only in 2012, whereas latitudinal translocation did not affect herbivore density. Variation in species richness was not explained by the source population or by the latitudinal translocation. At two of the study sites, the similarity of the herbivore communities among the populations decreased with increasing latitudinal distance of the source populations, possibly because birch populations that grow geographically closer to each other are genetically more similar, and therefore support a more similar composition of the arthropod community. All birch genotypes were colonized by local herbivores, suggesting that as herbivores shift their ranges polewards, they are able to colonize novel host‐plant genotypes. This enables compositional changes in insect communities on their host plants in the future, which in turn, might affect total herbivory and eventually, plant growth.     

Untangling latitudinal richness gradients at higher taxonomic levels: familial perspectives on the diversity of New World bat communities

Aims (i) To describe at the level of local communities latitudinal gradients in the species richness of different families of New World bats and to explore the generality of such gradients. (ii) To characterize the relative effects of changes in the richness of each family to the richness of entire communities. (iii) To determine differences in the rate and direction of latitudinal gradients in species richness within families. (iv) To evaluate how differences among families regarding latitudinal gradients in species richness influence the latitudinal gradient in species richness of entire communities. Location Continental New World ranging from the northern continental United States (Iowa, 42° N) to eastern Paraguay (Canindeyú, 24° S). Methods Data on the species composition of communities came from 32 intensively sampled sites. Analyses focused on species richness of five of nine New World bat families. Multivariate analysis of variance and discriminant function analysis determined and described differences among temperate, subtropical, and tropical climatic zones regarding the species richness of bat families. Simple linear regression described latitudinal gradients in species richness of families. Path analysis was used to describe: (i) the direct effect of latitude on species richness of communities, (ii) the indirect effects of latitude on the species richness of communities through its effect on the species richness of each family, (iii) the relative effects of latitude on the species richness of bat families, and (iv) the relative contribution of each family to variation in the species richness of communities. Results Highly significant differences among climatic zones existed primarily because of a difference between the temperate zone and the tropical and subtropical zones combined. This difference was associated with the high number of vespertilionids in the temperate zone and the high number of phyllostomids in the tropical and subtropical zones. Latitudinal gradients in species richness were contingent on phylogeny. Although only three of the five families exhibited significant gradients, all families except for the Vespertilionidae exhibited indistinguishable increases in species richness with decreases in latitude. The Emballonuridae, Phyllostomidae and Vespertilionidae exhibited significant latitudinal gradients whereby the former two families exhibited the classical increase in species richness with decreasing latitude and the latter family exhibited the opposite pattern. Variation in species richness of all families contributed significantly to variation in the species richness of entire communities. Nonetheless, the Phyllostomidae made a significantly stronger contribution to changes in species richness of communities than did all other families. Much of the latitudinal gradient in species richness of communities could be accounted for by the effects of latitude on the species richness of constituent families. Main conclusions Ecological and evolutionary differences among higher taxonomic units, particularly those differences involving life‐history traits, predispose taxa to exhibit different patterns of diversity along environmental gradients. This may be particularly true along extensive gradients such as latitude. Nonetheless, species rich taxa, by virtue of their greater absolute rates of change, can dominate and therefore define the pattern of diversity at a higher taxonomic level and eclipse differences among less represented taxa in their response to environmental gradients. This is true not only with respect to how bats drive the latitudinal gradient in species richness for all mammals, but also for how the Phyllostomidae drives the latitudinal gradient for all bats in the New World. Better understanding of the mechanistic basis of latitudinal gradients of diversity may come from comparing and contrasting patterns across lower taxonomic levels of a higher taxon and by identifying key ecological and evolutionary traits that are associated with such differences.     

Invariant properties of mycobiont-photobiont networks in Antarctic lichens

Aim

Lichens are often regarded as paradigms of mutualistic relationships. However, it is still poorly known how lichen-forming fungi and their photosynthetic partners interact at a community scale. We explored the structure of fungus-alga networks of interactions in lichen communities along a latitudinal transect in continental Antarctica. We expect these interactions to be highly specialized and, consequently, networks with low nestedness degree and high modularity.

Location

Transantarctic Mountains from 76° S to 85° S (continental Antarctica).

Time Period

Present.

Major Taxa Studied

Seventy-seven species of lichen-forming fungi and their photobionts.

Methods

DNA barcoding of photobionts using nrITS data was conducted in 756 lichen specimens from five regions along the Transantarctic Mountains. We built interaction networks for each of the five studied regions and a metaweb for the whole area. We explored the specialization of both partners using the number of partners a species interacts with and the specialization parameter d'. Network architecture parameters such as nestedness, modularity and network specialization parameter H₂' were studied in all networks and contrasted through null models. Finally, we measured interaction turnover along the latitudinal transect.

Results

We recovered a total of 842 interactions. Differences in specialization between partners were not statistically significant. Fungus-alga interaction networks showed high specialization and modularity, as well as low connectance and nestedness. Despite the large turnover in interactions occurring among regions, network parameters were not correlated with latitude.

Main Conclusions

The interaction networks established between fungi and algae in saxicolous lichen communities in continental Antarctica showed invariant properties along the latitudinal transect. Rewiring is an important driver of interaction turnover along the transect studied. Future work should answer whether the patterns observed in our study are prevalent in other regions with milder climates and in lichen communities on different substrates.